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Sample records for hydrogels synthesis characterization

  1. Synthesis and characterization of PEG dimethacrylates and their hydrogels.

    PubMed

    Lin-Gibson, Sheng; Bencherif, Sidi; Cooper, James A; Wetzel, Stephanie J; Antonucci, Joseph M; Vogel, Brandon M; Horkay, Ferenc; Washburn, Newell R

    2004-01-01

    Facile synthesis and detailed characterization of photopolymerizable and biocompatible poly(ethylene glycol) dimethacrylates (PEGDM) and poly(ethylene glycol) urethane-dimethacrylates (PEGUDM) are described. Poly(ethylene glycol)s of various molecular masses (M(n) = 1000 to 8000 g/mol) were reacted with methacrylic anhydride or with 2-isocyanatoethyl methacrylate to form PEGDMs and PEGUDMs, respectively. PEGDMs were also prepared by a microwave-assisted route to achieve fast reaction conversions under solvent free conditions. Combined analyses of (1)H NMR and MALDI-TOF MS confirmed the formation of prepolymers of high purity and narrow mass distribution (PD < 1.02). Aqueous solutions of the PEGDMs and PEGUDMs (10% and 20% by mass fraction) were photopolymerized to yield hydrogels. Bovine chondrocytes, seeded in the hydrogels, were used to assess the biocompatibility. Preliminary rheology and uniaxial compression measurements showed varied mechanical response, and biocompatibility studies showed that cells are completely viable in both types of hydrogels after two weeks. PMID:15244441

  2. Synthesis and characterization of a chitosan based nanocomposite injectable hydrogel.

    PubMed

    Wang, Qianqian; Chen, Dajun

    2016-01-20

    The aim of the current study was to enhance the mechanical property of chitosan/β-glycerophosphate disodium salt (CS/GP) injectable hydrogels. A novel nanocomposite injectable hydrogel was prepared by introducing attapulgite (ATP) nano particles into the CS/GP hydrogels. The mechanical properties of the composite hydrogels with two different water contents were characterized by tensile test, the results shown that the tensile strength and elongation at break of composite hydrogels both increased obviously with increasing of ATP content. And, in our testing range, the maximum values of tensile strength and elongation at break were both more than 5 times larger than that of neat CS/GP hydrogel. We discussed this enhancement effect in detail by Scanning electron microscope observations (SEM) and Fourier transform infrared spectroscopy testing (FT-IR). The SEM images of composite hydrogels shown quite different from the neat CS/GP hydrogel, where the pores were more tightly and with some uniform and smaller holes dispersed on the wall. FT-IR test results revealed that the introduction of ATP increased the cross-link density because of the hydrogen bonds formation between ATP nanoparticles and CS molecules. Also, we studied the impact of ATP introduction on gelation speed through tracking the dynamic process of the sol-gel transition by means of rheological measurement, and the results shown that the reaction rate increased significantly with the increase of ATP concentration. PMID:26572466

  3. Synthesis and characterization of cyclic acetal based degradable hydrogels.

    PubMed

    Kaihara, Sachiko; Matsumura, Shuichi; Fisher, John P

    2008-01-01

    While many synthetic, hydrolytically degradable hydrogels have been developed for biomedical applications, there are only a few examples whose polymer backbone does not form acidic products upon degradation. In order to address this concern, we proposed to develop a hydrogel based on a cyclic acetal unit that produces diols and propanals upon hydrolytic degradation. In particular, we proposed the fabrication of hydrogels formed by the free radical polymerization of two diacrylate monomers, 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD), a cyclic acetal having two acryl groups, and poly(ethylene glycol)diacrylate (PEGDA). However, the hydrophobicity of the EHD monomer inhibits hydrogel fabrication. Therefore this work develops a strategy to form hydrogels with a co-monomer system, one of which is hydrophobic, and subsequently describes the properties of the resulting hydrogel. Using benzoyl peroxide as an initiator and N,N-dimethyl-p-toluidine as an accelerator, the EHD and PEGDA monomers were reacted in an acetone/water co-solvent system. The chemical structure of the resulting EH-PEG [5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol-co-PEG] hydrogel was then characterized by FT-IR. Physicochemical properties of the EH-PEG hydrogel, including swelling degree, sol fraction, and contact angle, were determined so as to characterize the properties of these materials and ultimately investigate their use in drug delivery and tissue engineering applications. Results showed that EH-PEG hydrogel may be formed using the co-solvent system. Further results indicated that swelling degree is dependent upon initiator concentration, monomer concentration, and molar ratios of monomers, while sol fraction significantly depended on initiator concentration and monomer concentration, only. These results demonstrate the ability to fabricate hydrogels using EHD and PEGDA system as well as to control the properties of the resulting

  4. Synthesis and Characterization of Hybrid Hyaluronic Acid-Gelatin Hydrogels

    PubMed Central

    Camci-Unal, Gulden; Cuttica, Davide; Annabi, Nasim; Demarchi, Danilo; Khademhosseini, Ali

    2013-01-01

    Biomimetic hybrid hydrogels have generated broad interest in tissue engineering and regenerative medicine. Hyaluronic acid (HA) and gelatin (hydrolyzed collagen) are naturally derived polymers and biodegradable under physiological conditions. Moreover, collagen and HA are major components of the extracellular matrix (ECM) in most of the tissues (e.g. cardiovascular, cartilage, neural). When used as a hybrid material, HA-gelatin hydrogels may enable mimicking the ECM of native tissues. Although HA-gelatin hybrid hydrogels are promising biomimetic substrates, their material properties have not been thoroughly characterized in the literature. Herein, we generated hybrid hydrogels with tunable physical and biological properties by using different concentrations of HA and gelatin. The physical properties of the fabricated hydrogels including swelling ratio, degradation, and mechanical properties were investigated. In addition, in vitro cellular responses in both two and three dimensional (2D and 3D) culture conditions were assessed. It was found that the addition of gelatin methacrylate (GelMA) into HA methacrylate (HAMA) promoted cell spreading in the hybrid hydogels. Moreover, the hybrid hydrogels showed significantly improved mechanical properties compared to their single component analogs. The HAMA-GelMA hydrogels exhibited remarkable tunability behavior and may be useful for cardiovascular tissue engineering applications. PMID:23419055

  5. Synthesis and characterization of hybrid hyaluronic acid-gelatin hydrogels.

    PubMed

    Camci-Unal, Gulden; Cuttica, Davide; Annabi, Nasim; Demarchi, Danilo; Khademhosseini, Ali

    2013-04-01

    Biomimetic hybrid hydrogels have generated broad interest in tissue engineering and regenerative medicine. Hyaluronic acid (HA) and gelatin (hydrolyzed collagen) are naturally derived polymers and biodegradable under physiological conditions. Moreover, collagen and HA are major components of the extracellular matrix (ECM) in most of the tissues (e.g., cardiovascular, cartilage, neural). When used as a hybrid material, HA-gelatin hydrogels may enable mimicking the ECM of native tissues. Although HA-gelatin hybrid hydrogels are promising biomimetic substrates, their material properties have not been thoroughly characterized in the literature. Herein, we generated hybrid hydrogels with tunable physical and biological properties by using different concentrations of HA and gelatin. The physical properties of the fabricated hydrogels including swelling ratio, degradation, and mechanical properties were investigated. In addition, in vitro cellular responses in both two and three-dimensional culture conditions were assessed. It was found that the addition of gelatin methacrylate (GelMA) into HA methacrylate (HAMA) promoted cell spreading in the hybrid hydogels. Moreover, the hybrid hydrogels showed significantly improved mechanical properties compared to their single component analogs. The HAMA-GelMA hydrogels exhibited remarkable tunability behavior and may be useful for cardiovascular tissue engineering applications. PMID:23419055

  6. Lipid-hydrogel nanoparticles: Synthesis methods and characterization

    NASA Astrophysics Data System (ADS)

    Hong, Jennifer S.

    vesicles with encapsulated hydrogel precursor. The encapsulated hydrogel precursor is polymerized off-chip and the resultant hybrid nanoparticle size distributions are highly monodisperse and precisely controlled across a broad range relevant to the targeted delivery and controlled release of encapsulated therapeutic agents. Given the ability to modify liposome size and surface properties by altering the lipid components and the many polymers of current interest for nanoparticle synthesis, this approach could be adapted for a variety of hybrid nanoparticle systems.

  7. Synthesis and Characterization of Gelatin-Based Magnetic Hydrogels

    PubMed Central

    Helminger, Maria; Wu, Baohu; Kollmann, Tina; Benke, Dominik; Schwahn, Dietmar; Pipich, Vitaliy; Faivre, Damien; Zahn, Dirk; Cölfen, Helmut

    2014-01-01

    A simple preparation of thermoreversible gelatin-based ferrogels in water provides a constant structure defined by the crosslinking degree for gelatin contents between 6 and 18 wt%. The possibility of varying magnetite nanoparticle concentration between 20 and 70 wt% is also reported. Simulation studies hint at the suitability of collagen to bind iron and hydroxide ions, suggesting that collagen acts as a nucleation seed to iron hydroxide aggregation, and thus the intergrowth of collagen and magnetite nanoparticles already at the precursor stage. The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching. The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite. SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size. Swelling measurements underline that magnetite acts as additional crosslinker and therefore varying the magnetic and mechanical properties of the ferrogels. Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators. PMID:25844086

  8. PVNO-DVB hydrogels: synthesis and characterization. [Gamma radiation

    SciTech Connect

    Hasirci, V.N.

    1982-01-01

    Hydrogels with various degrees of crosslinking were synthesized from 2-vinylpyridine and divinylbenzene/ethylbenzene monomers using gamma irradiation. The influence of the solvent solubility parameter, ionic strength, and temperature on swelling and gel density were studied. Adsorption of water vapor on these gels was determined, and the data were used in the calculation of free energy changes involved in the process. Finally the drug release behavior-crosslink content relation was investigated. It was found that increase in crosslinking agent content adversely influenced swelling, gel density, and water vapor adsorption. The solvent solubility parameter was found to influence swelling more than ionic strength. Contrary to what was expected, it was not possible to classify the drug release behavior as first order.

  9. Synthesis and characterization of thermoreversible hydrogels from associating polymers

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Li, Chunhua; Rubinstein, Michael; Colby, Ralph; Cohn, Daniel; Rafailovich, Miriam; Sokolov, Jonathan

    2006-03-01

    Multiblock copolymers of poly(ethylene oxide)99-poly(propylene oxide)69-poly(ethylene oxide)99 were synthesized by coupling with hexamethylene diisocyanate (HDI). The rheological, morphological and structural properties of the gel were characterized as a function of temperature, composition and block number. Mixtures of multiblock and single block copolymers were also studied. Using neutron scattering we found that a large degree of alignment could be induced in the single block gel, but no order could be found in the multi-block or homopolymer multiblock mixture. The yield strain in samples with 3.2 of multiblocks was nearly an order of magnitude higher than the single bock gel. This was interpreted in terms of an ordered layered state of micelles being formed by steady shear. A model based on the competition between forming non-interacting micelles and forming bridges will be presented.

  10. Synthesis and characterization of antibacterial carboxymethyl Chitosan/ZnO nanocomposite hydrogels.

    PubMed

    Wahid, Fazli; Yin, Jun-Jiao; Xue, Dong-Dong; Xue, Han; Lu, Yu-Shi; Zhong, Cheng; Chu, Li-Qiang

    2016-07-01

    The antibacterial carboxymethyl chitosan/ZnO nanocomposite hydrogels were successfully prepared via in situ formation of ZnO nanorods in the crosslinked carboxymethyl chitosan (CMCh) matrix, by treating the CMCh hydrogel matrix with zinc nitrate solution followed by the oxidation of zinc ions with alkaline solution. The resulting CMCh/ZnO hydrogels were characterized by using FTIR spectroscopy, X-ray diffractormetry and scanning electron microscopy (SEM). SEM micrographs revealed the formation of ZnO nanorods in the hydrogel matrix with the size ranging from 190nm to 600nm. The swelling behavior of the prepared nanocomposite hydrogels was also investigated in different pH solutions. The CMCh/ZnO nanocomposite hydrogel showed rather higher swelling behavior in different pH solutions in comparison with neat CMCh hydrogel. Furthermore, the antibacterial activity of CMCh/ZnO hydrogel was studied against Escherichia coli and Staphylococcus aureus by CFU assay. The results demonstrated an excellent antibacterial activity of the nanocomposite hydrogel. Therefore, the developed CMCh/ZnO nanocomposite hydrogel can be used effectively in biomedical field. PMID:27017980

  11. Synthesis and characterization of an in situ forming hydrogel using tyramine conjugated high methoxyl gum tragacanth.

    PubMed

    Tavakol, Moslem; Vasheghani-Farahani, Ebrahim; Mohammadifar, Mohammad Amin; Soleimani, Masoud; Hashemi-Najafabadi, Sameereh

    2016-02-01

    In this study, an enzyme catalyzed in situ forming hydrogel based on tyramine conjugated high methoxyl content gum tragacanth (TA-HMGT) was prepared and characterized. TA-HMGT was synthesized via heterogeneous ammonolysis of methyl ester groups of HMGT. Then, the hydrogel was prepared via horseradish peroxidase catalyzed coupling reaction in the presence of hydrogen peroxide. Hydrogel properties, such as gelation time, swelling/degradation behavior and rheological properties could be adjusted by tuning the gelation parameters and extent of tyramine conjugation. This system was a soft elastic hydrogel with appropriate biocompatibility. The fast gelation of the hydrogel is desirable for clinical applications. Also, in vitro bovine serum albumin release from the synthesized hydrogel showed good release profile with limited burst release. PMID:26553882

  12. Synthesis and Characterization of Cellulose-Based Hydrogels to Be Used as Gel Electrolytes.

    PubMed

    Navarra, Maria Assunta; Dal Bosco, Chiara; Serra Moreno, Judith; Vitucci, Francesco Maria; Paolone, Annalisa; Panero, Stefania

    2015-01-01

    Cellulose-based hydrogels, obtained by tuned, low-cost synthetic routes, are proposed as convenient gel electrolyte membranes. Hydrogels have been prepared from different types of cellulose by optimized solubilization and crosslinking steps. The obtained gel membranes have been characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic-extensional properties, respectively. Hydrogels liquid uptake capability and ionic conductivity, derived from absorption of aqueous electrolytic solutions, have been evaluated, to assess the successful applicability of the proposed membranes as gel electrolytes for electrochemical devices. To this purpose, the redox behavior of electroactive species entrapped into the hydrogels has been investigated by cyclic voltammetry tests, revealing very high reversibility and ion diffusivity. PMID:26633528

  13. Synthesis and Characterization of Cellulose-Based Hydrogels to Be Used as Gel Electrolytes

    PubMed Central

    Navarra, Maria Assunta; Dal Bosco, Chiara; Serra Moreno, Judith; Vitucci, Francesco Maria; Paolone, Annalisa; Panero, Stefania

    2015-01-01

    Cellulose-based hydrogels, obtained by tuned, low-cost synthetic routes, are proposed as convenient gel electrolyte membranes. Hydrogels have been prepared from different types of cellulose by optimized solubilization and crosslinking steps. The obtained gel membranes have been characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic-extensional properties, respectively. Hydrogels liquid uptake capability and ionic conductivity, derived from absorption of aqueous electrolytic solutions, have been evaluated, to assess the successful applicability of the proposed membranes as gel electrolytes for electrochemical devices. To this purpose, the redox behavior of electroactive species entrapped into the hydrogels has been investigated by cyclic voltammetry tests, revealing very high reversibility and ion diffusivity. PMID:26633528

  14. Radiation synthesis and characterization of stimuli-sensitive chitosan-polyvinyl pyrrolidone hydrogels

    NASA Astrophysics Data System (ADS)

    Dergunov, Sergey A.; Nam, Irina K.; Mun, Grigoriy A.; Nurkeeva, Zauresh S.; Shaikhutdinov, Erengaip M.

    2005-04-01

    Novel cationic hydrogels were synthesized by γ-irradiation copolymerization of chitosan and polyvinyl pyrrolidone (PVP). The synthesis regularities and the swelling behaviour of hydrogels have been studied. It was shown that increasing of PVP concentration in feed composition also as radiation dose accompanied of increase of yield of gel fraction and decrease of swelling degree. At dose more than 3.5 kGy increasing of swelling degree and decreasing of gel fraction yield have been observed. It was shown that the hydrogels exhibit pH-sensitive behaviour in aqueous solution. In solutions of sodium dodecyl sulfate (SDS) the hydrogels are collapsed due to complexation, however, at concentration of SDS solution equal to critical micelle concentration the gels contracted and then swollen again.

  15. Synthesis and characterization of poly(2-hydroxyethylacrylate)/β-cyclodextrin hydrogels obtained by frontal polymerization.

    PubMed

    Nuvoli, Daniele; Alzari, Valeria; Nuvoli, Luca; Rassu, Mariella; Sanna, Davide; Mariani, Alberto

    2016-10-01

    For the first time, the synthesis of polymeric hydrogels containing cyclodextrins (CDs) obtained by frontal polymerization (FP) is reported. In particular, the effects of CDs on poly(2-hydroxyethylacrylate) hydrogel properties are investigated. In a first series of materials, β-cyclodextrin is dispersed into the polymer matrix, while in the second one acryloyl-β-cyclodextrin is grafted to poly(2-hydroxyethylacrylate) chains. FP parameters (front velocity and maximum temperature), swelling properties, glass transition temperatures and mechanical properties of the hydrogels are studied. Results show that both types of cyclodextrin influence the above properties, and the major effects are found for concentration higher than 1mol% of acryloyl-β-cyclodextrin. Namely, a significant increase of glass transition temperature and of compression moduli are found. Finally, this study demonstrates that FP is a convenient technique to obtain CD-containing hydrogels, in which the type and amount of cyclodextrin can be suitably modulated to tune polymer properties, in function of the desired hydrogel applications. PMID:27312626

  16. Synthesis, characterization and antimicrobial applications of zinc oxide nanoparticles loaded gum acacia/poly(SA) hydrogels.

    PubMed

    Bajpai, S K; Jadaun, Mamta; Tiwari, Seema

    2016-11-20

    In this work, zinc oxide nanoparticles were synthesized in-situ within the gum acacia/poly (acrylate) hydrogel network using hydrothermal approach. The synthesized zinc oxide nanoparticles were characterized by Surface plasmon resonance (SPR), X-Ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy and Scanning electron microscopy (SEM). The water absorption behavior of ZnO/GA/poly(SA) hydrogels was investigated in the phosphate buffer saline (PBS) of pH 7.4 at 37°C. The water uptake data were analyzed with the help of various kinetic models. Finally, the antimicrobial action of nanocomposites was studied using E. coli as model bacteria. PMID:27561472

  17. Synthesis and characterization of silver/poly( N-vinyl-2-pyrrolidone) hydrogel nanocomposite obtained by in situ radiolytic method

    NASA Astrophysics Data System (ADS)

    Jovanović, Željka; Krklješ, Aleksandra; Stojkovska, Jasmina; Tomić, Simonida; Obradović, Bojana; Mišković-Stanković, Vesna; Kačarević-Popović, Zorica

    2011-11-01

    This work describes radiolytic synthesis of silver nanoparticles (Ag NPs) within the poly( N-vinyl-2-pyrrolidone) (PVP) hydrogel. The hydrogel matrix was obtained by gamma irradiation-induced crosslinking, while the in situ reduction of Ag + ions was performed using strong reducing species formed under water radiolysis. Absorption spectrum of the Ag/PVP nanocomposite confirmed the formation of Ag NPs, showing the surface plasmon band maxima at 405 nm. Ag/PVP nanocomposites were characterized by XRD and TEM analysis, accompanied with investigations of swelling and diffusion properties in the simulated body fluid at 37 °C, and mechanical properties in bioreactor conditions. It was shown that Ag/PVP nanocomposite exhibited higher values of equilibrium swelling degree, Young's modulus, and molar mass between crosslinks, while lower values of the diffusion coefficient and effective crosslink density were obtained, as compared to the pure PVP.

  18. Synthesis and Characterization of Tunable Poly(Ethylene Glycol): Gelatin Methacrylate Composite Hydrogels

    PubMed Central

    Hutson, Che B.; Nichol, Jason W.; Aubin, Hug; Bae, Hojae; Yamanlar, Seda; Al-Haque, Shahed; Koshy, Sandeep T.

    2011-01-01

    Poly(ethylene glycol) (PEG) hydrogels are popular for cell culture and tissue-engineering applications because they are nontoxic and exhibit favorable hydration and nutrient transport properties. However, cells cannot adhere to, remodel, proliferate within, or degrade PEG hydrogels. Methacrylated gelatin (GelMA), derived from denatured collagen, yields an enzymatically degradable, photocrosslinkable hydrogel that cells can degrade, adhere to and spread within. To combine the desirable features of each of these materials we synthesized PEG-GelMA composite hydrogels, hypothesizing that copolymerization would enable adjustable cell binding, mechanical, and degradation properties. The addition of GelMA to PEG resulted in a composite hydrogel that exhibited tunable mechanical and biological profiles. Adding GelMA (5%–15% w/v) to PEG (5% and 10% w/v) proportionally increased fibroblast surface binding and spreading as compared to PEG hydrogels (p<0.05). Encapsulated fibroblasts were also able to form 3D cellular networks 7 days after photoencapsulation only within composite hydrogels as compared to PEG alone. Additionally, PEG-GelMA hydrogels displayed tunable enzymatic degradation and stiffness profiles. PEG-GelMA composite hydrogels show great promise as tunable, cell-responsive hydrogels for 3D cell culture and regenerative medicine applications. PMID:21306293

  19. Synthesis and characterization of tunable poly(ethylene glycol): gelatin methacrylate composite hydrogels.

    PubMed

    Hutson, Che B; Nichol, Jason W; Aubin, Hug; Bae, Hojae; Yamanlar, Seda; Al-Haque, Shahed; Koshy, Sandeep T; Khademhosseini, Ali

    2011-07-01

    Poly(ethylene glycol) (PEG) hydrogels are popular for cell culture and tissue-engineering applications because they are nontoxic and exhibit favorable hydration and nutrient transport properties. However, cells cannot adhere to, remodel, proliferate within, or degrade PEG hydrogels. Methacrylated gelatin (GelMA), derived from denatured collagen, yields an enzymatically degradable, photocrosslinkable hydrogel that cells can degrade, adhere to and spread within. To combine the desirable features of each of these materials we synthesized PEG-GelMA composite hydrogels, hypothesizing that copolymerization would enable adjustable cell binding, mechanical, and degradation properties. The addition of GelMA to PEG resulted in a composite hydrogel that exhibited tunable mechanical and biological profiles. Adding GelMA (5%-15% w/v) to PEG (5% and 10% w/v) proportionally increased fibroblast surface binding and spreading as compared to PEG hydrogels (p<0.05). Encapsulated fibroblasts were also able to form 3D cellular networks 7 days after photoencapsulation only within composite hydrogels as compared to PEG alone. Additionally, PEG-GelMA hydrogels displayed tunable enzymatic degradation and stiffness profiles. PEG-GelMA composite hydrogels show great promise as tunable, cell-responsive hydrogels for 3D cell culture and regenerative medicine applications. PMID:21306293

  20. New biodegradable dextran-based hydrogels for protein delivery: Synthesis and characterization.

    PubMed

    Pacelli, Settimio; Paolicelli, Patrizia; Casadei, Maria Antonietta

    2015-08-01

    A new derivative of dextran grafted with polyethylene glycol methacrylate through a carbonate bond (DEX-PEG-MA) has been synthesized and characterized. The photo-crosslinking reaction of DEX-PEG-MA allowed the obtainment of biodegradable networks tested for their mechanical and release properties. The new hydrogels were compared with those made of dextran methacrylate (DEX-MA), often employed as drug delivery systems of small molecules. The inclusion of PEG as a spacer created additional interactions among the polymeric chains improving the extreme fragility and lack of hardness typical of gels made of DEX-MA. Moreover, the different behavior in terms of swelling and degradability of the networks was able to affect the release of a model macromolecule over time, making DEX-PEG-MA matrices suitable candidates for the delivery of high molecular weight peptides. Interestingly, the combination of the two dextran derivatives showed intermediate ability to modulate the release of high molecular weight macromolecules. PMID:25933541

  1. Radiation synthesis and characterization of nanosilver/gelatin/carboxymethyl chitosan hydrogel

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Zhao, Yinghui; Wang, Lu; Xu, Ling; Zhai, Maolin; Wei, Shicheng

    2012-05-01

    A series of antibacterial hydrogels were fabricated from an aqueous solution of AgNO3, gelatin and carboxymethyl chitosan (CM-chitosan) by radiation-induced reduction and crosslinking at ambient temperature. The nanosilver particles were in situ synthesized accompanying with the formation of gelatin/CM-chitosan hydrogel. Transmission Electron Microscope and UV-vis analysis have verified the formation and homogeneous distribution of nanosilver particles in the hydrogel matrix. The nanosilver/gelatin/CM-chitosan hydrogels possessed interconnected porous structure, had a compressive modulus of 44 to 56 kPa, and could absorb 62 to 108 times of deionized water to its dry weight. Furthermore, the hydrogels were found to have sound antibacterial effect on Escherichia coli (E. coli), and their antibacterial ability could be significantly enhanced by the increasing of AgNO3 content. The comprehensive results of this study suggest that nanosilver/gelatin/CM-chitosan hydrogels have potential as an antibacterial wound dressing.

  2. Synthesis, characterization and application in biomedicine of a novel chondroitin sulfate based hydrogel and bioadhesive

    NASA Astrophysics Data System (ADS)

    Strehin, Iossif

    Clinically, there exists a need for adhesive biomaterials. There is room to improve upon what is currently on the market as it is either too toxic, lacks the required adhesive strength and/or lacks the desired degradation properties. The general goals of this thesis all focused on designing a biomaterial which would improve upon these shortcomings while at the same time allow for modifications to meet the needs for the specific application of interest. To accomplish this task, it was important to choose the appropriate composition and crosslinking chemistry which will allow the most flexibility. Chondroitin sulfate (CS) was chosen as the principle component of the hydrogel because it is a ubiquitous glycosaminoglycan (GAG) found in almost all tissues in the body. Many variants of CS exist with each one possessing unique biological activity allowing for tight control over these properties of the material. To modulate cell migration through the adhesive, polyethylene glycol (PEG) or blood was used as the second constituent. The former made the scaffold act as a cell barrier while the ladder could be used in varying concentrations to modulate cell adhesion and migration into the biomaterial. Also, the CS and blood components are both biodegradable and degradation can be controlled using various methods. While the constituents were chosen to allow flexibility in the biological activity and cell migration into the scaffold, the crosslinking chemistry was chosen to allow control over the mechanical properties as well as to increase tissue adhesion. By functionalizing the carboxyl groups of the GAG with N-hydroxysuccinimide (NHS), the resulting chondroitin sulfate succinimidyl succinate (CS-NHS) molecule could react with primary amines on polymers to form a hydrogel as well as the primary amines on proteins comprising tissue to anchor the hydrogel to the tissue. The material has been characterized and optimized for several applications. The applications described here

  3. SYNTHESIS AND CHARACTERIZATION OF POLYSIALIC ACID/CARBOXYMETHYL CHITOSAN HYDROGEL WITH POTENTIAL FOR DRUG DELIVERY.

    PubMed

    Wu, J R; Zhan, X B; Zheng, Z Y; Zhang, H T

    2015-01-01

    A novel hydrogel was prepared from polysialic acid (PSA) and carboxymethyl chitosan (CMCS) using glutaraldehyde as the cross-linking agent. The resulting PSA-CMCS hydrogel exhibited pH sensitivity, in which the swelling ratio under acidic conditions was higher than those under neutral or alkaline conditions. The swelling ratio of PSA-CMCS hydrogel at equilibrium depended on the medium pH, the cross-linking agent concentration, and the ratio of PSA to CMCS (w/w). Bovine serum albumin (BSA) and 5-fluorouracil (5-FU) were used as model drugs to prepare hydrogel delivery systems. The loading efficiencies of the hydrogel for BSA and 5-FU were 26.25 and 36.74%, respectively. Release behaviors of BSA and 5-FU were influenced by the pH. MTT assays confirmed that PSA-CMCS hydrogel has no cytotoxicity toward the NIH-3T3 cell line; in fact, the 100% aqueous extract of the PSA-CMCS hydrogel enhanced cell growth. These results suggest that PSA-CMCS hydrogel may be a promising pH-sensitive delivery system, especially for hydrophobic chemicals. PMID:26762102

  4. Photo-crosslinked PDMSstar-PEG Hydrogels: Synthesis, Characterization, and Potential Application for Tissue Engineering Scaffolds

    PubMed Central

    Hou, Yaping; Schoener, Cody A.; Regan, Katherine R.; Munoz-Pinto, Dany; Hahn, Mariah S.; Grunlan, Melissa A.

    2010-01-01

    Inorganic-organic hydrogels with tunable chemical and physical properties were prepared from methacrylated star polydimethylsiloxane (PDMSstar-MA) and diacrylated poly(ethylene glycol) (PEG-DA) for use as tissue engineering scaffolds. Eighteen compositionally unique hydrogels were prepared by photo-crosslinking varying weight ratios of PEG-DA and PDMSstar-MA of different molecular weights (Mn): PEG-DA (Mn = 3.4k and 6k g/mol) and PDMSstar-MA (Mn = 1.8k, 5k and 7k g/mol). Introduction of PDMSstar-MA caused formation of discrete PDMS-enriched microparticles dispersed within the PEG matrix. The swelling ratio, mechanical properties in tension and compression, non-specific protein adhesion, controlled introduction of bioactivity and cytotoxicity of hydrogels were studied. This library of inorganic-organic hydrogels with tunable properties provides a useful platform to study the effect of scaffold properties on cell behavior. PMID:20146518

  5. Synthesis and characterization of photocrosslinkable gelatin and silk fibroin interpenetrating polymer network hydrogels.

    PubMed

    Xiao, Wenqian; He, Jiankang; Nichol, Jason W; Wang, Lianyong; Hutson, Ché B; Wang, Ben; Du, Yanan; Fan, Hongsong; Khademhosseini, Ali

    2011-06-01

    To effectively repair or replace damaged tissues, it is necessary to design scaffolds with tunable structural and biomechanical properties that closely mimic the host tissue. In this paper, we describe a newly synthesized photocrosslinkable interpenetrating polymer network (IPN) hydrogel based on gelatin methacrylate (GelMA) and silk fibroin (SF) formed by sequential polymerization, which possesses tunable structural and biological properties. Experimental results revealed that IPNs, where both the GelMA and SF were independently crosslinked in interpenetrating networks, demonstrated a lower swelling ratio, higher compressive modulus and lower degradation rate as compared to the GelMA and semi-IPN hydrogels, where only GelMA was crosslinked. These differences were likely caused by a higher degree of overall crosslinking due to the presence of crystallized SF in the IPN hydrogels. NIH-3T3 fibroblasts readily attached to, spread and proliferated on the surface of IPN hydrogels, as demonstrated by F-actin staining and analysis of mitochondrial activity (MTT). In addition, photolithography combined with lyophilization techniques was used to fabricate three-dimensional micropatterned and porous microscaffolds from GelMA-SF IPN hydrogels, furthering their versatility for use in various microscale tissue engineering applications. Overall, this study introduces a class of photocrosslinkable, mechanically robust and tunable IPN hydrogels that could be useful for various tissue engineering and regenerative medicine applications. PMID:21295165

  6. Synthesis and Characterization of Degradable Bioconjugated Hydrogels with Hyperbranched Multifunctional Crosslinkers

    PubMed Central

    Pedrón, Sara; Peinado, Carmen; Bosch, Paula; S.Anseth, Kristi

    2010-01-01

    Hyperbranched poly(ester amide) polymer (Hybrane™ S1200; Mn 1200 g/mol) was functionalized with maleic anhydride (MA) and propylene sulfide, to obtain multifunctional crosslinkers with fumaric and thiol-end groups, S1200MA and S1200SH, respectively. The degree of substitution of maleic acid groups (DS) was controlled by varying the molar ratio of MA to S1200 in the reaction mixture. Hydrogels were obtained by UV crosslinking of functionalized S1200 and poly(ethyleneglycol) diacrylate (PEGDA) in aqueous solutions. Compressive modulus increased with decreasing the S1200/PEG ratio and also depended on the DS of the multifunctional crosslinker (S1200). Also, heparin-based macromonomers together with functionalized hyperbranched polymers were used to construct novel functional hydrogels. The multivalent hyperbranched polymers allowed high crosslinking densities in heparin modified gels while introducing biodegradation sites. Both heparin presence and acrylate/thiol ratio have an impact on degradation profiles and morphologies. Hyperbranched crosslinked hydrogels showed no evidence of cell toxicity. Overall, the multifunctional crosslinkers afford hydrogels with promising properties that suggest that these may be suitable for tissue engineering applications. PMID:20561601

  7. The synthesis of hydrogels with controlled distribution of polymer brushes in hydrogel network

    NASA Astrophysics Data System (ADS)

    Sun, YuWei; Zhou, Chao; Zhang, AoKai; Xu, LiQun; Yao, Fang; Cen, Lian; Fu, Guo-Dong

    2014-11-01

    Poly(ethylene glycol) (PEG) hydrogels with 3-dimensionally controlled well-defined poly(N-isopropylacrylamide) (poly(NIPAAm)) brushes were prepared by combined copper(I)-catalyzed azide-alkyne cycloaddition ("Click Chemistry") and atom transfer radical polymerization (ATRP). The resulting hydrogels were presented as representatives with their detailed synthesis routes and characterization. HPEG-S-poly(NIPAAm) is a hydrogel with poly(NIPAAm) brushes mainly grafted on surface, whereas HPEG-G-poly(NIPAAm) has a gradiently decreased poly(NIPAAm) brushes in their chain length from surface to inside. On the other hand, poly(NIPAAm) brushes in HPEG-U-poly(NIPAAm) are uniformly dispersed throughout the whole hydrogel network. Successful preparation of HPEG-S-poly(NIPAAm), HPEG-G-poly(NIPAAm) and HPEG-U-poly(NIPAAm) were ascertained by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. Optical properties and thermal behaviors of these hydrogels were evaluated by UV-visible transmittance spectra and differential scanning calorimetry (DSC). Hence, the flexibility and controllability of the synthetic strategy in varying the distribution of polymer brushes and hydrogel properties was demonstrated. Hydrogels with tunable and well-defined 3-dimensional poly(NIPAAm) polymer brushes could be tailor-designed to find potential applications in smart devices or skin dressing, such as for diabetics as they have special optical and thermal behaviors.

  8. Synthesis and characterization of thermo- and pH- sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via γ-radiation

    NASA Astrophysics Data System (ADS)

    Cai, Hong; Zhang, Zheng Pu; Chuan Sun, Ping; Lin He, Bing; Xia Zhu, Xiao

    2005-09-01

    Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via γ-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that the grafting percentage and grafting efficiency increased with the increase of monomer concentration and total irradiation dose. The highest grafting percentage is 620%, the lower critical solution temperature (LCST) of this hydrogel is about 28 °C.

  9. A novel thermo-responsive hydrogel based on salecan and poly(N-isopropylacrylamide): synthesis and characterization.

    PubMed

    Wei, Wei; Hu, Xinyu; Qi, Xiaoliang; Yu, Hao; Liu, Yucheng; Li, Junjian; Zhang, Jianfa; Dong, Wei

    2015-01-01

    Salecan is a novel microbial polysaccharide produced by Agrobacterium sp. ZX09. The salt-tolerant strain was isolated from a soil sample in our laboratory and the 16S rDNA sequence was deposited in the GenBank database under the accession number GU810841. Salecan is suitable to fabricate hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility. Here, salecan has been introduced into poly(N-isopropylacrylamide) (PNIPAm) network to form novel thermo-sensitive semi-interpenetrating polymer networks (semi-IPNs). The structure of salecan/PNIPAm semi-IPNs was confirmed by Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) proved the stability of the semi-IPNs. Rheological and compressive tests revealed an elastic solid-like behavior and good mechanical properties of the hydrogels. Swelling behavior test showed the hydrogels possessed high water content at room temperature. An excellent thermo-sensitive property of fast response rates to temperature had been demonstrated as well. In vitro degradation measurements ensured the semi-IPNs were degradable. Cytotoxicity and cell adhesion study suggested the synthesized salecan/PNIPAm hydrogels were non-toxic and biocompatibility. The results indicated the novel thermo-responsive hydrogels could be a suitable candidate for biomedical applications. PMID:25460596

  10. A functionalized, injectable hydrogel for localized drug delivery with tunable thermosensitivity: synthesis and characterization of physical and toxicological properties.

    PubMed

    Elias, Paul Z; Liu, Gary W; Wei, Hua; Jensen, Michael C; Horner, Philip J; Pun, Suzie H

    2015-06-28

    Thermosensitive injectable hydrogels have been used for the delivery of pharmacological and cellular therapies in a variety of soft tissue applications. A promising class of synthetic, injectable hydrogels based upon oligo(ethylene glycol) methacrylate (OEGMA) monomers has been previously reported, but these polymers lack reactive groups for covalent attachment of therapeutic molecules. In this work, thermosensitive, amine-reactive and amine-functionalized polymers were developed by incorporation of methacrylic acid N-hydroxysuccinimide ester or 2-aminoethyl methacrylate into OEGMA-based polymers. A model therapeutic peptide, bivalirudin, was conjugated to the amine-reactive hydrogel to investigate effects on the polymer thermosensitivity and gelation properties. The ability to tune the thermosensitivity of the polymer in order to compensate for peptide hydrophilicity and maintain gelation capability below physiological temperature was demonstrated. Cell encapsulation studies using an H9 T-cell line (CD4+) were conducted to evaluate feasibility of the hydrogel as a carrier for cellular therapies. Although this class of polymers is generally considered to be non-toxic, it was found that concentrations required for gelation were incompatible with cell survival. Investigation into the cause of cytotoxicity revealed that a hydrolysis byproduct, diethylene glycol monomethyl ether, is likely a contributing factor. While modifications to structure or composition will be required to enable viable cell encapsulation, the functionalized injectable hydrogel has the potential for controlled delivery of a wide range of drugs. PMID:25747144

  11. A novel poly(γ-glutamic acid)/silk-sericin hydrogel for wound dressing: Synthesis, characterization and biological evaluation.

    PubMed

    Shi, Lu; Yang, Ning; Zhang, Hao; Chen, Li; Tao, Lei; Wei, Yen; Liu, Hui; Luo, Ying

    2015-03-01

    A novel multifunctional poly(γ-glutamic acid)/silk sericin (γ-PGA/SS) hydrogel has been developed and used as wound dressing. The physical and chemical properties of the γ-PGA/SS gels were systemically investigated. Furthermore, these γ-PGA/SS gels have been found to promote the L929 fibroblast cells proliferate, and in the in vivo study, significant stimulatory effects were also observed on granulation and capillary formation on day 9 in H-2-treated wounds, indicating that this new complex hydrogel could maintain a moist healing environment, protect the wound from bacterial infection, absorb excess exudates, and promote cell proliferation to reconstruct damaged tissue. Considering the simple preparation process and excellent biological property, this γ-PGA/SS hydrogel might have a wide range of applications in biomedical and clinical areas. PMID:25579954

  12. Synthesis, characterization, and swelling behaviors of salt-sensitive maize bran-poly(acrylic acid) superabsorbent hydrogel.

    PubMed

    Zhang, Mingyue; Cheng, Zhiqiang; Zhao, Tianqi; Liu, Mengzhu; Hu, Meijuan; Li, Junfeng

    2014-09-01

    A novel composite hydrogel was prepared via UV irradiation copolymerization of acrylic acid and maize bran (MB) in the presence of composite initiator (2,2-dimethoxy-2-phenylacetophenone and ammonium persulfate) and cross-linker (N,N'-methylenebis(acrylamide)). Under the optimized conditions, maize bran-poly(acrylic acid) was obtained (2507 g g(-1) in distilled water and 658 g g(-1) in 0.9 wt % NaCl solution). Effects of granularity, salt concentration, and various cations and anions on water absorbency were investigated. It was found that swelling was extremely sensitive to the ionic strength and cation and anion type. Swelling kinetics and water diffusion mechanism in distilled water were also discussed. Moreover, the product showed excellent water retention capability under the condition of high temperature or high pressure. The salt sensitivity, good water absorbency, and excellent water retention capability of the hydrogels give this intelligentized polymer wide potential applications. PMID:25133321

  13. Synthesis and characterization of a novel semi-IPN hydrogel based on Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate).

    PubMed

    Hu, Xinyu; Feng, Liandong; Wei, Wei; Xie, Aming; Wang, Shiming; Zhang, Jianfa; Dong, Wei

    2014-05-25

    Salecan is a novel water-soluble, high molecular mass extracellular β-glucan produced by Agrobacterium sp. ZX09. Salecan has excellent physicochemical and biological properties, making it very suitable for hydrogel preparation. In this study, a series of novel semi-interpenetrating polymer network (semi-IPN) hydrogels containing Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethylmethacrylate) (poly(DMAA-co-HEMA)) were synthesized by radical polymerization and semi-IPN technology. Structure and morphology of the hydrogels were characterized by FTIR, XRD, TGA and SEM. The semi-IPNs had a well-interconnected porous structure with tunable pore size ranging from 6 to 41μm. Swelling capability of the hydrogels was improved by introducing the hydrophilic Salecan. Rheological results indicated that the incorporation of poly(DMAA-co-HEMA) into hydrogels enhanced the storage modulus. Compression tests revealed that these semi-IPNs were robust materials with compressive modulus between 13.3 and 90.5kPa, the addition of Salecan increased the fracture strain from 71.1% to 88.8%. Degradation and cytotoxicity tests demonstrated that semi-IPNs were degradable and non-toxic. PMID:24708962

  14. Morphological Characterization of Silicone Hydrogels

    NASA Astrophysics Data System (ADS)

    Gido, Samuel

    2007-03-01

    Silicone hydrogel materials are used in the latest generation of extended wear soft contact lenses. To ensure comfort and eye health, these materials must simultaneously exhibit high oxygen permeability and high water permeability / hydrophilicity. The materials achieve these opposing requirements based on bicontinuous composite of nanoscale domains of oxygen permeable (silicones) and hydrophilic (water soluble polymer) materials. The microphase separated morphology of silicone hydrogel contact lens materials was imaged using field emission gun scanning transmission electron microscopy (FEGSTEM), and atomic force microscopy (AFM). Additional morphological information was provided by small angle X-ray scattering (SAXS). These results all indicate a nanophase separated structure of silicone rich (oxygen permeable) and carbon rich (water soluble polymer) domains separated on a length scale of about 10 nm.

  15. Synthesis and Characterization of Photocurable Polyamidoamine Dendrimer Hydrogels as a Versatile Platform for Tissue Engineering and Drug Delivery

    PubMed Central

    Desai, Pooja N.; Yuan, Quan; Yang, Hu

    2010-01-01

    In this work, we describe a novel polyamidoamine (PAMAM) dendrimer hydrogel (DH) platform with potential for tissue engineering and drug delivery. With PAMAM dendrimer G3.0 being the underlying carrier, polyethylene glycol (PEG) chains of various lengths (MW=1500, 6000, or 12000 gmol−1) were coupled to the dendrimer to different extents, and the resulting PEGylated PAMAM dendrimers were further coupled with acrylate groups to yield photoreactive dendrimer macromonomers for gel formation. It was found that gelation based on photoreactive PAMAM G3.0 macromonomers was restricted by the degree of PEGylation, PEG chain length, and the distribution of acrylate groups on the dendrimer surface. Further, the architecture of the photoreactive macromonomers affects the structural stability and swelling of the resultant networks. A completely crosslinked network (DH-G3.0–12000H) with a high water swelling ratio was created by UV-curing of PAMAM dendrimer G3.0 coupled with 28 PEG 12000 chains in the presence of the eosin Y-based photoinitiating system. The disintegration of DH-G3.0–12000H was pH-insensitive. DH-G3.0–12000H was found to have similar cytocompatibility to uncrosslinked G3.0–12000H but have a significantly lower cellular uptake by macrophages. With PAMAM dendrimer G3.5 being the underlying carrier, the dendrimer modified with 43 PEG 1500 chains was able to form a completely crosslinked network (DH-G3.50–1500H) by UV-curing in the presence of the eosin Y-based photoinitiating system. DH-G3.50–1500H exhibited pH-dependent disintegration. Its disintegration ratio increased with pH. PAMAM dendrimer hydrogels uniquely express the structural characteristics of both PEG hydrogel and PAMAM dendrimer and have potential for various applications in tissue engineering and drug delivery. PMID:20108892

  16. Characterization of Thiol-Ene Crosslinked PEG Hydrogels

    PubMed Central

    Toepke, Michael W.; Impellitteri, Nicholas A.; Theisen, Jeffrey M.

    2014-01-01

    The properties of synthetic hydrogels can be tuned to address the needs of many tissue-culture applications. This work characterizes the swelling and mechanical properties of thiol-ene crosslinked PEG hydrogels made with varying prepolymer formulations, demonstrating that hydrogels with a compressive modulus exceeding 600 kPa can be formed. The amount of peptide incorporated into the hydrogel is shown to be proportional to the amount of peptide in the prepolymer solution. Cell attachment and spreading on the surface of the peptide-functionalized hydrogels is demonstrated. Additionally, a method for bonding distinct layers of cured hydrogels is used to create a microfluidic channel. PMID:24883041

  17. Synthesis and Characterization of a Hydrogel with Controllable Electroosmosis: A Potential Brain Tissue Surrogate for Electrokinetic Transport

    PubMed Central

    Faraji, Amir H.; Cui, Jonathan J.; Guy, Yifat; Li, Ling; Weber, Stephen G.

    2011-01-01

    Electroosmosis is the bulk fluid flow initiated by application of an electric field to an electrolyte solution in contact with immobile objects with a non-zero ζ-potential such as the surface of a porous medium. Electroosmosis may be used to assist analytical separations. Several gel-based systems with varying electroosmotic mobilities have been made in this context. A method was recently developed to determine the ζ-potential of organotypic hippocampal slice cultures (OHSC) as a representative model for normal brain tissue. The ζ-potential of the tissue is significant. However, determining the role of the ζ-potential in solute transport in tissue in an electric field is difficult because the tissue's ζ-potential cannot be altered. We hypothesized that mass transport properties, namely the ζ-potential and tortuosity, could be modulated by controlling the composition of a set of hydrogels. Thus, poly(acrylamide-co-acrylic acid) gels were prepared with three compositions (by monomer weight percent): acrylamide/acrylic acid 100/0, 90/10, and 75/25. The ζ-potentials of these gels at pH 7.4 are distinctly different, and in fact vary approximately linearly with the weight percent of acrylic acid. We discovered that the 25% acrylic acid gel is a respectable model for brain tissue, as its ζ-potential is comparable to the OHSC. This series of gels permits the experimental determination of the importance of electrokinetic properties in a particular experiment or protocol. Additionally, tortuosities were measured electrokinetically and by evaluating diffusion coefficients. Hydrogels with well-defined ζ-potential and tortuosity may find utility in biomaterials, analytical separations, and as a surrogate model for OHSC and living biological tissues. PMID:21905710

  18. A review on the radiation synthesis of copolymeric hydrogels for adsorption and separation purposes1

    NASA Astrophysics Data System (ADS)

    Güven, Olgun; Şen, Murat; Karadağ, Erdener; Saraydın, Dursun

    1999-10-01

    Recent theoretical and experimental work on the radiation synthesis, characterization and the use of hydrogels containing diprotic acid moieties have been reviewed. It is shown that upon incorporating vinyl monomers carrying diprotic acid groups randomly in the main chain, non-ionic hydrogels like poly(acryl amide) and poly(n-vinyl 2-pyrrolidone) acquired stimuli-responsive behaviours. The swelling behaviours of these hydrogels are shown to be predictable reliably under varying solution conditions by a theoretical expression derived recently. Examples are given for the utilization of these hydrogels in the adsorption and separation of biomolecules, dyes and metal ions in aqueous media and their ability to release drugs in stepwise manner in response to pH of the environment.

  19. Crystalline colloidal array hydrogel materials: From synthesis to applications

    NASA Astrophysics Data System (ADS)

    Liu, Lei

    This dissertation is focused on the synthesis, characterization, and applications of crystalline colloidal array (CCA) hydrogel materials. CCA are three dimensional periodic structures formed by the electrostatic self-assembly of monodisperse macroionic colloidal spheres in an aqueous medium. CCA dispersions efficiently Bragg diffract light in the near UV to near IR spectral region, and are useful in areas of optical device fabrication, chemical sensing devices, and novel separation materials. We developed methodologies to synthesize monodisperse colloidal silica spheres via hydrolysis and condensation of tetraethoxysilane in nonionic reverse microemulsion systems. We examined the effects of reaction parameters and surfactant hydrophilic-lipophilic-balance (HLB) number on the final particle size and size distribution. We developed a unique multi-step growth technique by which the final particle diameter can be continuously selected with extremely narrow size distributions over a broad size range. We also developed methodologies to surface functionalize silica spheres to increase the particle surface charge density by two orders of magnitude. The resulting dispersions readily self-assemble into CCA and Bragg diffract light over a broad concentration range. In addition, we discovered an anomalously intense secondary diffraction phenomenon from CCA which occurs due to the superimposed Bragg diffraction from numerous lattice planes. This was quantitatively modeled by using dynamical diffraction and light scattering theory. We extended the microemulsion synthesis methodologies to fabricate monodisperse SiOsb2/CdS composite spheres with well-controlled and complex morphologies. By controlling the co-precipitation process, CdS could be incorporated into silica spheres as quantum dots, as large inclusions, as surface patches and welds, or as shells or cores. Further processing of these materials by selectively etching out CdS templates also generated a series of porous

  20. Radiation synthesis of superabsorbent CMC based hydrogels for agriculture applications

    NASA Astrophysics Data System (ADS)

    Raafat, Amany I.; Eid, Mona; El-Arnaouty, Magda B.

    2012-07-01

    A series of superabsorbent hydrogel based on carboxymethylcellulose (CMC) and polyvinylpyrrolidone (PVP) crosslinked with gamma irradiation have been proposed for agriculture application. The effect of preparation conditions such as feed solution composition and absorbed irradiation dose on the gelation and swelling degree was evaluated. The structure and the morphology of the superabsorbent CMC/PVP hydrogel were characterized using Fourier transform infrared spectroscopy technique (FTIR), and scanning electron microscope (SEM). Effect of ionic strength and cationic and anionic kinds on the swelling behavior of the obtained hydrogel was investigated. Urea as an agrochemical model was loaded onto the obtained hydrogel to provide nitrogen (N) nutrients. The water retention capability and the urea release behavior of the CMC/PVP hydrogels were investigated. It was found that, the obtained CMC/PVP hydrogels have good swelling degree that greatly affected by its composition and absorbed dose. The swelling was also extremely sensitive to the ionic strength and cationic kind. Owing to its considerable slow urea release, good water retention capacity, being economical, and environment-friendly, it might be useful for its application in agriculture field.

  1. Synthesis and characterization of a novel pH-thermo dual responsive hydrogel based on salecan and poly(N,N-diethylacrylamide-co-methacrylic acid).

    PubMed

    Wei, Wei; Qi, Xiaoliang; Liu, Yucheng; Li, Junjian; Hu, Xinyu; Zuo, Gancheng; Zhang, Jianfa; Dong, Wei

    2015-12-01

    Salecan is a water-soluble microbial polysaccharide produced by Agrobacterium sp. ZX09, a salt-tolerant strain isolated from a soil sample in our laboratory. Previous work inspired us salecan is a good candidate to fabricate hydrogels. Poly(N,N-diethylacrylamide) is one type of thermo sensitive polymer which is not investigated extremely as poly(N-isopropylacrylamide). Here, we report a novel pH-thermo dual responsive hydrogel based on salecan and poly(N,N-diethylacrylamide-co-methacrylic acid) semi-interpenetrating polymer networks (semi-IPNs). The physicochemical property of this hydrogel was investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA), rheological test and Scanning Electron Microscopy (SEM). It was interesting that the storage modulus (G') and pore size of the hydrogel could be tuned by adjusting the content of salecan and crosslinker. The pH-thermo dual responsive property was demonstrated by swelling behavior test: the swelling ratio of the hydrogel decreased continuously as the temperature increased from 25 °C to 37 °C, while it was pH-dependent as well. Especially, when exposed to a higher temperature (37 °C) and acidic environment (pH 4.0), drug-loaded hydrogel would have a quick release. Finally, the cytotoxicity of drug-free hydrogels was investigated on A549 and HepG2 cells, results showed that it was non-toxic while the DOX released from hydrogels had comparable cytotoxicity with respect to free DOX. In conclusion, the novel salecan/poly(N,N-diethylacrylamide-co-methacrylic acid) semi-interpenetrating polymer network hydrogels were pH-thermo dual responsive and may be a promising candidate for drug delivery system. PMID:26590634

  2. Synthesis of Borohydride and Catalytic Dehydrogenation by Hydrogel Based Catalyst

    NASA Astrophysics Data System (ADS)

    Boynuegri, Tugba Akkas; Karabulut, Ahmet F.; Guru, Metin

    2016-08-01

    This paper deals with the synthesis of calcium borohydride (Ca(BH4)2) as hydrogen storage material. Calcium chloride salt (CaCl2), magnesium hydride (MgH2), and boron oxide (B2O3) were used as reactants in the mechanochemical synthesis of Ca(BH4)2. The mechanochemical reaction was carried out by means of Spex type ball milling without applying high pressure and temperature. Parametric studies have been established at different reaction times and for different amounts of reactants at a constant ball to powder ratio (BPR) 4:1. The best combination was determined by Fourier Transform Infrared (FT-IR) analysis. According to the FT-IR analysis, reaction time, the first reaction parameter, was found as 1600 min. After the reaction time was fixed at 1600 min, the difference of the B-H peak areas was dependent on the amount of reactant MgH2 that was investigated. The amount of the reactant (MgH2), the second reaction parameter, was measured to be 2.85 times more than the stoichiometric amount of MgH2. According to our previous studies, BPR was selected as 4:1 for all experiments. Samples were prepared in a glove box under argon atmosphere but the time that elapsed for FT-IR analysis highly affected B-H bonds. B-H peak areas clearly decreased with time because of negative effect of ambient atmosphere. A catalyst was prepared by absorbing cobalt fluoride (CoF2) in poly (acrylamide-co-acrylic acid) hydrogel matrices type and its catalytic dehydrogenation performance that has been characterized by the catalytic reaction of sodium borohydride's known hydrogen capacity in an alkaline medium. The metal amount of hydrogel catalyst was determined as 135.82 mg Co by Atomic Absorption Spectroscopy (AAS). The specific dehydrogenation capacity of the Co active compound in the catalyst thanks to catalytic dehydrogenation of commercial sodium borohydride was measured as 1.66 mL H2/mg Co.

  3. Synthesis of Borohydride and Catalytic Dehydrogenation by Hydrogel Based Catalyst

    NASA Astrophysics Data System (ADS)

    Boynuegri, Tugba Akkas; Karabulut, Ahmet F.; Guru, Metin

    2016-06-01

    This paper deals with the synthesis of calcium borohydride (Ca(BH4)2) as hydrogen storage material. Calcium chloride salt (CaCl2), magnesium hydride (MgH2), and boron oxide (B2O3) were used as reactants in the mechanochemical synthesis of Ca(BH4)2. The mechanochemical reaction was carried out by means of Spex type ball milling without applying high pressure and temperature. Parametric studies have been established at different reaction times and for different amounts of reactants at a constant ball to powder ratio (BPR) 4:1. The best combination was determined by Fourier Transform Infrared (FT-IR) analysis. According to the FT-IR analysis, reaction time, the first reaction parameter, was found as 1600 min. After the reaction time was fixed at 1600 min, the difference of the B-H peak areas was dependent on the amount of reactant MgH2 that was investigated. The amount of the reactant (MgH2), the second reaction parameter, was measured to be 2.85 times more than the stoichiometric amount of MgH2. According to our previous studies, BPR was selected as 4:1 for all experiments. Samples were prepared in a glove box under argon atmosphere but the time that elapsed for FT-IR analysis highly affected B-H bonds. B-H peak areas clearly decreased with time because of negative effect of ambient atmosphere. A catalyst was prepared by absorbing cobalt fluoride (CoF2) in poly (acrylamide-co-acrylic acid) hydrogel matrices type and its catalytic dehydrogenation performance that has been characterized by the catalytic reaction of sodium borohydride's known hydrogen capacity in an alkaline medium. The metal amount of hydrogel catalyst was determined as 135.82 mg Co by Atomic Absorption Spectroscopy (AAS). The specific dehydrogenation capacity of the Co active compound in the catalyst thanks to catalytic dehydrogenation of commercial sodium borohydride was measured as 1.66 mL H2/mg Co.

  4. Hydrogel: Preparation, characterization, and applications: A review

    PubMed Central

    Ahmed, Enas M.

    2013-01-01

    Hydrogel products constitute a group of polymeric materials, the hydrophilic structure of which renders them capable of holding large amounts of water in their three-dimensional networks. Extensive employment of these products in a number of industrial and environmental areas of application is considered to be of prime importance. As expected, natural hydrogels were gradually replaced by synthetic types due to their higher water absorption capacity, long service life, and wide varieties of raw chemical resources. Literature on this subject was found to be expanding, especially in the scientific areas of research. However, a number of publications and technical reports dealing with hydrogel products from the engineering points of view were examined to overview technological aspects covering this growing multidisciplinary field of research. The primary objective of this article is to review the literature concerning classification of hydrogels on different bases, physical and chemical characteristics of these products, and technical feasibility of their utilization. It also involved technologies adopted for hydrogel production together with process design implications, block diagrams, and optimized conditions of the preparation process. An innovated category of recent generations of hydrogel materials was also presented in some details. PMID:25750745

  5. Gelatin- and starch-based hydrogels. Part A: Hydrogel development, characterization and coating.

    PubMed

    Van Nieuwenhove, Ine; Salamon, Achim; Peters, Kirsten; Graulus, Geert-Jan; Martins, José C; Frankel, Daniel; Kersemans, Ken; De Vos, Filip; Van Vlierberghe, Sandra; Dubruel, Peter

    2016-11-01

    The present work aims at constructing the ideal scaffold matrix of which the physico-chemical properties can be altered according to the targeted tissue regeneration application. Ideally, this scaffold should resemble the natural extracellular matrix (ECM) as close as possible both in terms of chemical composition and mechanical properties. Therefore, hydrogel films were developed consisting of methacrylamide-modified gelatin and starch-pentenoate building blocks because the ECM can be considered as a crosslinked hydrogel network consisting of both polysaccharides and structural, signaling and cell-adhesive proteins. For the gelatin hydrogels, three different substitution degrees were evaluated including 31%, 72% and 95%. A substitution degree of 32% was applied for the starch-pentenoate building block. Pure gelatin hydrogels films as well as interpenetrating networks with gelatin and starch were developed. Subsequently, these films were characterized using gel fraction and swelling experiments, high resolution-magic angle spinning (1)H NMR spectroscopy, rheology, infrared mapping and atomic force microscopy. The results indicate that both the mechanical properties and the swelling extent of the developed hydrogel films can be controlled by varying the chemical composition and the degree of substitution of the methacrylamide-modified gelatin applied. The storage moduli of the developed materials ranged between 14 and 63kPa. Phase separation was observed for the IPNs for which separated starch domains could be distinguished located in the surrounding gelatin matrix. Furthermore, we evaluated the affinity of aggrecan for gelatin by atomic force microscopy and radiolabeling experiments. We found that aggrecan can be applied as a bioactive coating for gelatin hydrogels by a straightforward physisorption procedure. Thus, we achieved distinct fine-tuning of the physico-chemical properties of these hydrogels which render them promising candidates for tissue engineering

  6. Synthesis of photodegradable hydrogels as dynamically tunable cell culture platforms

    PubMed Central

    Kloxin, April M.; Tibbitt, Mark W.; Anseth, Kristi S.

    2013-01-01

    We describe a detailed procedure to create photolabile, poly(ethylene glycol)-based (PEG) hydrogels and manipulate material properties in situ. The cytocompatible chemistry and degradation process enable dynamic, tunable changes for applications in 2D or 3D cell culture. The materials are created by synthesizing an o-nitrobenzylether-based photodegradable monomer that can be coupled to primary amines. Here, we provide coupling procedures to PEG-bis-amine to form a photodegradable crosslinker or to the fibronectin-derived peptide RGDS to form a photoreleasable tether. Hydrogels are synthesized with the photodegradable crosslinker in the presence or absence of cells, allowing direct encapsulation or seeding on surfaces. Cell-material interactions can be probed in 2D or 3D by spatiotemporally controlling the gel microenvironment, which allows unique experiments to be performed to monitor cell response to changes in their niche. Degradation is readily achieved with cytocompatible wavelengths of low intensity flood irradiation (365 to 420 nm) in minutes or with highintensity laser irradiation (405 nm) in seconds. In this protocol, synthesis and purification of the photodegradable monomers take approximately 2 weeks, but can be substantially shortened by purchasing the o-nitrobenzylether precursor. Preparation of the sterile solutions for hydrogel fabrication takes hours, while the reaction to form the final hydrogel is complete in minutes. Hydrogel degradation occurs on-demand, in seconds to minutes, with user-directed light exposure. This comprehensive protocol is useful for controlling peptide presentation and substrate modulus during cell culture on or within an elastic matrix. These PEG-based materials are useful for probing the dynamic influence of cell-cell and cell-material interactions on cell function in 2D or 3D. While other protocols are available for controlling peptide presentation or modulus, few allow manipulation of material properties in situ and in the

  7. Synthesis and viscoelastic characterization of novel hydrogels generated via photopolymerization of 1,2-epoxy-5-hexene modified poly(vinyl alcohol) for use in tissue replacement.

    PubMed

    Bader, Rebecca A

    2008-07-01

    Hydrogels have been proposed as candidates for tissue replacement; however, current systems are often highly susceptible to hydrolytic degradation and have not been shown to mimic the viscoelastic behavior of the native tissue when subjected to dynamic loading conditions. In the present work, 1,2-epoxy-5-hexene modified poly(vinyl alcohol) was crosslinked via photopolymerization to generate non-degradable hydrogels with mechanical properties and network characteristics that could be modulated through variation in the type and percentage of a monomeric additive. Complex shear moduli obtained from dynamic frequency sweeps in torsional shear were used to exemplify the differences in the viscoelastic behavior of the materials, and the corresponding changes in crosslink density were determined by rubber elasticity theory. Hydrolysis resistance was assessed by monitoring variations in the moduli of hydrogels submerged in Hank's balanced salt solution for progressively longer periods of time. Over the time-frame of the experiment, no change in the viscoelastic behavior was observed. Direct contact assays and elution tests were used to demonstrate that the system was non-cytotoxic. This study represents a successful attempt to generate a non-degradable hydrogel system with viscoelastic behavior that can be readily modulated to match that of soft biological tissues for use in tissue replacement. PMID:18359671

  8. [Study on synthesis of physically crosslinked biomedical polyurethane hydrogel].

    PubMed

    Yin, Zhengyan; Niu, Hong; Tan, Hong; Xie, Xingyi; Zhong, Yinping

    2006-06-01

    In this study, using ethylene carbonate and ethanolamine, we synthesized a novel diol chain-extender, bis-hydroxylethyl carbomate (EC-AE), which contains carbomate structure. The polyurethanes, PUA25 and PUB25, with different extenders, EC-AE and BDO, were synthesized by one-step polymerization, respectively. Their structures were characterized by using FT-IR and DSC. The results indicated that the microphase separation degree of PUA25 was less than that of PUB25, in other words, the amount of hydrogen bonding between hard segments and soft segments in PUA25 was superior to that in PUB25. And the formation of physically crosslinked hydrogels prepared by PUA25 and PUB25 were studied in detail. It was found that only PUA25 can form hydrogel in situ from solution state by cooling. And this kind of hydrogels showed the transition cycle of "gel-sol-gel" under "cooling-heating-cooling" thermal cycles, respectively. The results suggested that the physically crosslinked polyurethane hydrogels were easily possessed in high degree of phase mixing. PMID:16856394

  9. Smart Macroporous IPN Hydrogels Responsive to pH, Temperature, and Ionic Strength: Synthesis, Characterization, and Evaluation of Controlled Release of Drugs.

    PubMed

    Dragan, Ecaterina Stela; Cocarta, Ana Irina

    2016-05-18

    Fast responsive macroporous interpenetrating polymer network (IPN) hydrogels were fabricated in this work by a sequential strategy, as follows: the first network, consisting of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEM) cross-linked with N,N'-methylenebisacrylamide (BAAm), was prepared at -18 °C, the second network consisting of poly(acrylamide) (PAAm) cross-linked with BAAm, being also generated by cryogelation technique. Both single network cryogels (SNC) and IPN cryogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and water uptake. The presence of weak polycation PDMAEM endows the SNCs and the IPNs cryogels with sensitivity at numerous external stimuli such as pH, temperature, ionic strength, electric field, among which the first three were investigated in this work. It was found that the initial concentration of monomers in both networks was the key factor in tailoring the properties of IPN cryogels such as swelling kinetics, equilibrium water content (EWC), phase transition temperature and the response at ionic strength. The pore size increased after the formation of the second network, the swelling kinetics in pure water being comparable with that of the SNC, phase transition temperature being situated in the range 35-36 °C for IPN cryogels. The water uptake at equilibrium (WUeq) abruptly increased at pH < 3.0 in the case of SNCs, whereas the response of IPN cryogels at the decrease of pH from 6.0 to 1.0 was strongly dependent on the gel structure, the values of WUeq being lower at a higher concentration of DMAEM in the first network, the monomer concentration in the second network being about 10 wt %. The pH response was very much diminished when the monomer concentration was high in both networks (15 wt % in the first network, and 21 wt % in the second network). The increase of the ionic strength from 0 up to 0.3 M NaCl led to the decrease of the WUeq, for all cryogels, the level of dehydration

  10. Rheological Characterization of Bioinspired Mineralization in Hydrogels

    NASA Astrophysics Data System (ADS)

    Regitsky, Abigail; Holten-Andersen, Niels

    With increasing amounts of CO2 in the atmosphere linked to potentially catastrophic climate change, it is critical that we find methods to permanently sequester and store CO2. Inspired by the natural biomineralization of calcium carbonate (CaCO3), one future goal of this project is to understand the mechanisms of CaCO3 mineralization in order to ultimately optimize a bioinspired hydrogel system, which produces high value industrial powders that consume CO2 as a feedstock. Along the way, we are developing a rheological technique to study mineral nucleation and growth events by measuring the modulations in mechanical properties of a hydrogel system during mineralization. Our initial system consists of a gelatin hydrogel matrix, which is preloaded with calcium ions, and an aqueous solution of carbonate ions, which are allowed to diffuse through the gel to initiate the mineralization process. In order to monitor how the growth of minerals affects the mechanical properties of the gel network, we measure the storage (G') and loss (G'') moduli of the system in situ. Future work will focus on modifying the properties of the minerals formed by changing the polymer used in the hydrogel network and adding other organic molecules into the system.

  11. Starch nanocrystals based hydrogel: Construction, characterizations and transdermal application.

    PubMed

    Bakrudeen, Haja Bava; Sudarvizhi, C; Reddy, B S R

    2016-11-01

    Bio-based nanocomposites were prepared using starch nanocrystals obtained by acid hydrolysis of native starches using different acid sources. In recent times, focuses on starch nanocrystals (SNCs) have been increasing in number of research works dedicated to the development of bio-nanocomposites by blending with different biopolymeric matrices. The work mainly deals with the preparation of starch nanocrystals using different native starches by acid hydrolysis using hydrochloric acid and trifluroacetic acid. The as-prepared starch nanocrystals are having high crystallinity and more platelet morphologies, and used as a drug carrying filler material in the hydrogel formulations with the care of different polymer matrices. The condensed work also concentrates on the dispersion of antiviral drug in the hydrogels, which are applied onto biocompatible bio-membrane to be formulating a complete transdermal patch. The acid hydrolysed starch nanocrystals were thoroughly characterized using TEM, SEM, particle size analysis and zeta potential. Their thermal stability and the crystalline properties were also characterized using TG-DSC and XRD respectively. The physiochemical interaction and compatibility between the drug and the SNCs filler in the polymeric hydrogels were evaluated using FT-IR analysis. The formulated hydrogels were subjected to evaluation of in vitro permeation studies using Franz diffusion studies. The in vitro study was indicated substantial guarantee for the fabrication of drug dispersed in polymeric hydrogels using SNCs as filler matrices for a successful transdermal drug delivery. PMID:27524091

  12. Nanoscale functionalization and characterization of surfaces with hydrogel patterns and biomolecules

    NASA Astrophysics Data System (ADS)

    Dinakar, Hariharasudhan Chirra

    The advent of numerous tools, ease of techniques, and concepts related to nanotechnology, in combination with functionalization via simple chemistry has made gold important for various biomedical applications. In this dissertation, the development and characterization of planar gold surfaces with responsive hydrogel patterns for rapid point of care sensing and the functionalization of gold nanoparticles for drug delivery are highlighted. Biomedical micro- and nanoscale devices that are spatially functionalized with intelligent hydrogels are typically fabricated using conventional UV-lithography. Herein, precise 3-D hydrogel patterns made up of temperature responsive crosslinked poly(N-isopropylacrylamide) over gold were synthesized. The XY control of the hydrogel was achieved using microcontact printing, while thickness control was achieved using atom transfer radical polymerization (ATRP). Atomic force microscopy analysis showed that to the ATRP reaction time governed the pattern growth. The temperature dependent swelling ratio was tailored by tuning the mesh size of the hydrogel. While nanopatterns exhibited a broad lower critical solution temperature (LCST) transition, surface roughness showed a sharp LCST transition. Quartz crystal microbalance with dissipation showed rapid response behavior of the thin films, which makes them applicable as functional components in biomedical devices. The easy synthesis, relative biocompatibility, inertness, and easy functionalization of gold nanoparticles (GNPs) have made them useful for various biomedical applications. Although ATRP can be successfully carried out over GNPs, the yield of stable solution based GNPs for biomedical applications prove to be low. As an alternative approach, a novel method of ISOlating, FUnctionalizing, and REleasing nanoparticles (ISOFURE) was proposed. Biodegradable poly(beta-amino ester) hydrogels were used to synthesize ISOFURE-GNP composites. ATRP was performed inside the composite, and the

  13. Rheological Characterization Of Nano-Composite Hydrogels

    NASA Astrophysics Data System (ADS)

    Lombardi, Jack

    Engineered Polymer hydrogels and hydrogels from Bio macromolecules have visco-elastic properties that can be measured using Oscillatory Shear Rheology. Manipulation and measurement of physical properties in gels including F-127 Pluronic Block Co-Polymer and Poly(N-isopropylacrylamide)-Clay are shown through OSR by addition of salts, clays and glucose at physiological levels. Rheological analysis of f-127 illustrates changes in G' reduction with phase transition temperature. Measurements also indicate physical changes due to the aforementioned additives vary as a function of the gel physical and chemical structure. In particular, non-enzymatic glycation is shown to change the modulus of elasticity in both of the gels tested. Rheological analysis is also interpreted to produce a reduction In gel mesh size in the PNIPA -clay gels due to a possible co-solvency between phases of varying degrees of hydration.

  14. Magnetic hyaluronate hydrogels: preparation and characterization

    NASA Astrophysics Data System (ADS)

    Tóth, Ildikó Y.; Veress, Gábor; Szekeres, Márta; Illés, Erzsébet; Tombácz, Etelka

    2015-04-01

    A novel soft way of hyaluronate (HyA) based magnetic hydrogel preparation was revealed. Magnetite nanoparticles (MNPs) were prepared by co-precipitation. Since the naked MNPs cannot be dispersed homogenously in HyA-gel, their surface was modified with natural and biocompatible chondroitin-sulfate-A (CSA) to obtain CSA-coated MNPs (CSA@MNPs). The aggregation state of MNPs and that loaded with increasing amount of CSA up to 1 mmol/g was measured by dynamic light scattering at pH~6. Only CSA@MNP with ≥0.2 mmol/g CSA content was suitable for magnetic HyA-gel preparation. Rheological studies showed that the presence of CSA@MNP with up to 2 g/L did not affect the hydrogel's rheological behavior significantly. The results suggest that the HyA-based magnetic hydrogels may be promising formulations for future biomedical applications, e.g. as intra-articular injections in the treatment of osteoarthritis.

  15. In situ characterization of structural dynamics in swelling hydrogels.

    PubMed

    Guzman-Sepulveda, J R; Deng, J; Fang, J Y; Dogariu, A

    2016-07-01

    Characterizing the structural morphology and the local viscoelastic properties of soft complex systems raises significant challenges. Here we introduce a dynamic light scattering method capable of in situ, continuous monitoring of structural changes in evolving systems such as swelling gels. We show that the inherently non-stationary dynamics of embedded probes can be followed using partially coherent radiation, which effectively isolates only single scattering contributions even during the dramatic changes in the scattering regime. Using a simple and robust experimental setup, we demonstrate the ability to continuously monitor the structural dynamics of chitosan hydrogels formed by the Ag(+) ion-triggered gelation during their long-term swelling process. We demonstrate that both the local viscoelastic properties of the suspending medium and an effective cage size experienced by diffusing probe particles loaded into the hydrogel can be recovered and used to describe the structural dynamics of hydrogels with different levels of cross-linking. This characterization capability is critical for defining and controlling the hydrogel performance in different biomedical applications. PMID:27336408

  16. One-step synthesis of interpenetrating network hydrogels: Environment sensitivities and drug delivery properties.

    PubMed

    Lu, Jingqiong; Li, Yinhui; Hu, Deng; Chen, Xiaoling; Liu, Yongmei; Wang, Liping; Ashraf, Muhammmad Aqeel; Zhao, Yansheng

    2016-01-01

    A novel interpenetrating network hydrogel for drug controlled release, composed of modified poly(aspartic acid) (KPAsp) and carboxymethyl chitosan (CMCTS), was prepared in aqueous system. The surface morphology and composition of hydrogels were characterized by SEM and FTIR. The swelling properties of KPAsp, KPAsp/CMCTS semi-IPN and KPAsp/CMCTS IPN hydrogels were investigated and the swelling dynamics of the hydrogels was analyzed based on the Fickian equation. The pH, temperature and salt sensitivities of hydrogels were further studied, and the prepared hydrogels showed extremely sensitive properties to pH, temperature, the ionic salts kinds and concentration. The results of controlled drug release behaviors of the hydrogels revealed that the introduction of IPN observably improved the drug release properties of hydrogels, the release rate of drug from hydrogels can be controlled by the structure of the hydrogels and pH value of the external environment, a relative large amount of drug released was preferred under simulated intestinal fluid. These results illustrated high potential of the KPAsp/CMCTS IPN hydrogels for application as drug carriers. PMID:26858562

  17. One-step synthesis of interpenetrating network hydrogels: Environment sensitivities and drug delivery properties

    PubMed Central

    Lu, Jingqiong; Li, Yinhui; Hu, Deng; Chen, Xiaoling; Liu, Yongmei; Wang, Liping; Ashraf, Muhammmad Aqeel; Zhao, Yansheng

    2015-01-01

    A novel interpenetrating network hydrogel for drug controlled release, composed of modified poly(aspartic acid) (KPAsp) and carboxymethyl chitosan (CMCTS), was prepared in aqueous system. The surface morphology and composition of hydrogels were characterized by SEM and FTIR. The swelling properties of KPAsp, KPAsp/CMCTS semi-IPN and KPAsp/CMCTS IPN hydrogels were investigated and the swelling dynamics of the hydrogels was analyzed based on the Fickian equation. The pH, temperature and salt sensitivities of hydrogels were further studied, and the prepared hydrogels showed extremely sensitive properties to pH, temperature, the ionic salts kinds and concentration. The results of controlled drug release behaviors of the hydrogels revealed that the introduction of IPN observably improved the drug release properties of hydrogels, the release rate of drug from hydrogels can be controlled by the structure of the hydrogels and pH value of the external environment, a relative large amount of drug released was preferred under simulated intestinal fluid. These results illustrated high potential of the KPAsp/CMCTS IPN hydrogels for application as drug carriers. PMID:26858562

  18. Synthesis and degradation test of hyaluronic acid hydrogels.

    PubMed

    Hahn, Sei Kwang; Park, Jung Kyu; Tomimatsu, Takashi; Shimoboji, Tsuyoshi

    2007-03-10

    Hyaluronic acid (HA) hydrogels prepared with three different crosslinking reagents were assessed by in vitro and in vivo degradation tests for various tissue engineering applications. Adipic acid dihydrazide grafted HA (HA-ADH) was synthesized and used for the preparation of methacrylated HA (HA-MA) with methacrylic anhydride and thiolated HA (HA-SH) with Traut's reagent (imminothiolane). (1)H NMR analysis showed that the degrees of HA-ADH, HA-MA, and HA-SH modification were 69, 29, and 56 mol%, respectively. HA-ADH hydrogel was prepared by the crosslinking with bis(sulfosuccinimidyl) suberate (BS(3)), HA-MA hydrogel with dithiothreitol (DTT) by Michael addition, and HA-SH hydrogel with sodium tetrathionate by disulfide bond formation. According to in vitro degradation tests, HA-SH hydrogel was degraded very fast, compared to HA-ADH and HA-MA hydrogels. HA-ADH hydrogel was degraded slightly faster than HA-MA hydrogel. Based on these results, HA-MA hydrogels and HA-SH hydrogels were implanted in the back of SD rats and their degradation was assessed according to the pre-determined time schedule. As expected from the in vitro degradation test results, HA-SH hydrogel was in vivo degraded completely only in 2 weeks, whereas HA-MA hydrogels were degraded only partially even in 29 days. The degradation rate of HA hydrogels were thought to be controlled by changing the crosslinking reagents and the functional group of HA derivatives. In addition, the state of HA hydrogel was another factor in controlling the degradation rate. Dried HA hydrogel at 37 degrees C for a day resulted in relatively slow degradation compared to the bulk HA hydrogel. There was no adverse effect during the in vivo tests. PMID:17101173

  19. Unrefined wood hydrolysates are viable reactants for the reproducible synthesis of highly swellable hydrogels.

    PubMed

    Maleki, Laleh; Edlund, Ulrica; Albertsson, Ann-Christine

    2014-08-01

    A value-adding robust and sequential synthetic pathway was elaborated to produce hydrogel structures with ionic character from crude acetylated galactoglucomannan-rich wood hydrolysate (WH). The WH was first-step liquor originating from a sulphite cracking pulp process for dissolving pulp. The synthetically modified WH fractions were verified at each step by NMR and FTIR, and the hydrogels were characterized with respect to their swelling and mechanical properties. Altering the crosslinking chemistry and the content of ionic moieties resulted in hydrogels with various swelling ratios and mechanical properties. Renewable hydrogel formulations with swelling ratios as high as Qeq=270 were achieved. PMID:24751275

  20. Characterization of alginate-brushite in-situ hydrogel composites.

    PubMed

    Dabiri, Seyed Mohammad Hossein; Lagazzo, Alberto; Barberis, Fabrizio; Farokhi, Mehdi; Finochio, Elisabetta; Pastorino, Laura

    2016-10-01

    In the present study alginate-brushite composite hydrogels were in-situ synthetized and characterized with respect to preparation parameters. Specifically, the influence of initial pH value and initial concentration of phosphate precursor on the in-situ fabrication of the composite hydrogel were taken into account. The composite hydrogels were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric (TGA, DTG) and differential thermal analysis (DTA). Finally, the cell viability tests were carried out (MTT) over the incubation time period of 3, 7, and 14days. The results revealed that the formation and the crystalline stability of brushite were highly dependent on the initial pH value. It was shown that as the pH reached to the value of 6, characteristics peaks of brushite appeared in the FTIR spectra. Besides, the XRD and thermal analysis results were in a good accordance with those of FTIR. In addition, the SEM images demonstrated that the plate like brushite was formed inside the alginate matrix. Also, a considerable impact of pH variation on the biocompatibility of samples was noticed so that the majority of samples especially those prepared in the acidic conditions were toxic. PMID:27287148

  1. Review of Collagen I Hydrogels for Bioengineered Tissue Microenvironments: Characterization of Mechanics, Structure, and Transport

    PubMed Central

    Vlachos, Pavlos P.; Rylander, Marissa Nichole

    2014-01-01

    Type I collagen hydrogels have been used successfully as three-dimensional substrates for cell culture and have shown promise as scaffolds for engineered tissues and tumors. A critical step in the development of collagen hydrogels as viable tissue mimics is quantitative characterization of hydrogel properties and their correlation with fabrication parameters, which enables hydrogels to be tuned to match specific tissues or fulfill engineering requirements. A significant body of work has been devoted to characterization of collagen I hydrogels; however, due to the breadth of materials and techniques used for characterization, published data are often disjoint and hence their utility to the community is reduced. This review aims to determine the parameter space covered by existing data and identify key gaps in the literature so that future characterization and use of collagen I hydrogels for research can be most efficiently conducted. This review is divided into three sections: (1) relevant fabrication parameters are introduced and several of the most popular methods of controlling and regulating them are described, (2) hydrogel properties most relevant for tissue engineering are presented and discussed along with their characterization techniques, (3) the state of collagen I hydrogel characterization is recapitulated and future directions are proposed. Ultimately, this review can serve as a resource for selection of fabrication parameters and material characterization methodologies in order to increase the usefulness of future collagen-hydrogel-based characterization studies and tissue engineering experiments. PMID:24923709

  2. Preparation and characterization of cellulose composite hydrogels from tea residue and carbohydrate additives.

    PubMed

    Liu, Zhijun; Huang, Huihua

    2016-08-20

    Composite hydrogels were prepared from tea cellulose in ionic liquid of 1-allyl-3-methylimidazolium chloride and effect of κ-carrageenan, chitosan, guar gum and soluble starch on characteristics of the prepared hydrogels were investigated. The prepared hydrogels were characterized via Fourier transform infrared, thermogravimetry analysis, differential scanning calorimetry. Sodium salicylate was used as the model drug to compare the swelling, drug loading and releasing kinetics of the prepared hydrogels. Thiazolyl blue tetrazolium bromide assay and relative growth rates were adopted to evaluate cell cytotoxicity and biocompatibility of the prepared hydrogels. Chitosan and guar gum could improve thermostability and mechanical characteristics of the composite hydrogels, while κ-carrageenan or soluble starch could improve equilibrium swelling ratio, sodium salicylate loading and releasing. Guar gum and chitosan could increase permeation resistance and were beneficial for release control of the hydrogels. Addition of chitosan, κ-carrageenan, guar gum and soluble starch were proven cell compatibility and non-cytotoxicity. PMID:27178928

  3. Bioinspired Synthesis of CaCO3 Superstructures through a Novel Hydrogel Composite Membranes Mineralization Platform: A Comprehensive View.

    PubMed

    Di Profio, Gianluca; Salehi, Shabnam Majidi; Caliandro, Rocco; Guccione, Pietro; Nico, Giovanni; Curcio, Efrem; Fontananova, Enrica

    2016-01-27

    Hydrogel composite membranes (HCMs) are used as novel mineralization platforms for the bioinspired synthesis of CaCO3 superstructures. A comprehensive statistical analysis of the experimental results reveals quantitative relationships between crystallization conditions and crystal texture and a strong selectivity toward complex morphologies when monomers bearing carboxyl and hydroxyl groups are used together in the hydrogel layer synthesis in HCMs. PMID:26609641

  4. Biomimetic synthesis of calcium-deficient hydroxyapatite in a natural hydrogel.

    PubMed

    Hutchens, Stacy A; Benson, Roberto S; Evans, Barbara R; O'Neill, Hugh M; Rawn, Claudia J

    2006-09-01

    A novel composite material consisting of calcium-deficient hydroxyapatite (CdHAP) biomimetically deposited in a bacterial cellulose hydrogel was synthesized and characterized. Cellulose produced by Gluconacetobacter hansenii was purified and sequentially incubated in solutions of calcium chloride followed by sodium phosphate dibasic. A substantial amount of apatite (50-90% of total dry weight) was homogeneously incorporated throughout the hydrogel after this treatment. X-ray diffractometry (XRD) showed that CdHAP crystallites had formed in the cellulose. XRD further demonstrated that the CdHAP was comprised of 10-50 nm anisotropic crystallites elongated in the c-axis, similar to natural bone apatite. Fourier transform infrared (FTIR) spectroscopy demonstrated that hydroxyl IR bands of the cellulose shifted to lower wave numbers indicating that a coordinate bond had possibly formed between the CdHAP and the cellulose hydroxyl groups. FTIR also suggested that the CdHAP had formed from an octacalcium phosphate precursor similar to physiological bone. Scanning electron microscopy (SEM) images confirmed that uniform approximately 1 microm spherical CdHAP particles comprised of nanosized crystallites with a lamellar morphology had formed in the cellulose. The synthesis of the composite mimics the natural biomineralization of bone indicating that bacterial cellulose can be used as a template for biomimetic apatite formation. This composite may have potential use as an orthopedic biomaterial. PMID:16713623

  5. Biomimetic Synthesis of Calcium-Deficient Hydroxyapatite in a Natural Hydrogel

    SciTech Connect

    Hutchens, Stacy A; Benson, Roberto S.; Evans, Barbara R; O'Neill, Hugh Michael; Rawn, Claudia J

    2006-01-01

    A novel composite material consisting of calcium-deficient hydroxyapatite (CdHAP) biomimetically deposited in a bacterial cellulose hydrogel was synthesized and characterized. Cellulose produced by Gluconacetobacter hansenii was purified and sequentially incubated in solutions of calcium chloride followed by sodium phosphate dibasic. A substantial amount of apatite (50-90% of total dry weight) was homogeneously incorporated throughout the hydrogel after this treatment. X-ray diffractometry (XRD) showed that CdHAP crystallites had formed in the cellulose. XRD further demonstrated that the CdHAP was comprised of 10-50nm anisotropic crystallites elongated in the c-axis, similar to natural bone apatite. Fourier transform infrared (FTIR) spectroscopy demonstrated that hydroxyl IR bands of the cellulose shifted to lower wave numbers indicating that a coordinate bond had possibly formed between the CdHAP and the cellulose hydroxyl groups. FTIR also suggested that the CdHAP had formed from an octacalcium phosphate precursor similar to physiological bone. Scanning electron microscopy (SEM) images confirmed that uniform ?1 mm spherical CdHAP particles comprised of nanosized crystallites with a lamellar morphology had formed in the cellulose. The synthesis of the composite mimics the natural biomineralization of bone indicating that bacterial cellulose can be used as a template for biomimetic apatite formation. This composite may have potential use as an orthopedic biomaterial.

  6. Synthesis of Gold Nanoflowers Encapsulated with Poly(N-isopropylacrylamide-co-acrylic acid) Hydrogels.

    PubMed

    Bae, Saet-Byeol; Lee, Sang-Wha

    2015-10-01

    In this work, hydrogel-coated gold nanoflowers (AuNFs@hydrogel) were facilely prepared. First, gold nanoflowers (AuNFs) were synthesized by reducing gold acid with ascorbic acid in the presence of chitosan biopolymers, and the chitosan-mediated AuNFs were subsequently conjugated with oleic acid with carboxylate groups. Finally, the olefin-conjugated AuNFs were encapsulated with P(NIPAM-co-AAC) hydrogels via a radical polymerization reaction with co-monomer ratio of [NIPAM:AAc = 91:9 wt%]. The encapsulated hydrogels had a lower critical solution temperature (LCST) slightly above the physiological temperature and demonstrated a thermo-sensitive variation of particle size. The hydrogel-coated AuNFs can be utilized as a promising thermo-responsive drug delivery system with a unique optical property. As-prepared samples were characterized by DLS, SEM, TEM, UV-vis and Zeta potential meter. PMID:26726447

  7. Characterizing pore sizes and water structure in stimuli-responsive hydrogels

    SciTech Connect

    Hoffman, A.S.; Antonsen, K.P.; Ashida, T.; Bohnert, J.L.; Dong, L.C.; Nabeshima, Y.; Nagamatsu, S.; Park, T.G.; Sheu, M.S.; Wu, X.S.; Yan, Q.

    1993-12-31

    Hydrogels have been extensively investigated as potential matrices for drug delivery. In particular, hydrogels responsive to pH and temperature changes have been of greatest interest most recently. Proteins and peptide drugs are especially relevant for delivery from such hydrogel matrices due to the relatively {open_quotes}passive{close_quotes} and biocompatible microenvironment which should exist within the hydrogel aqueous pores. The large molecular size of many proteins requires an interconnected large pore structure. Furthermore, the gel pore {open_quotes}walls{close_quotes} should not provide hydrophobic sites for strong interactions with proteins. In the special case of ion exchange release the protein would be attracted by opposite charges on the polymer backbones. Therefore, it is important both to control and to characterize the pore structure and the water character within a hydrogel to be used or protein or peptide drug delivery. This talk will critically review techniques for estimating these two key parameters in hydrogels.

  8. Preparation and characterization of quaternary ammonium chitosan hydrogel with significant antibacterial activity.

    PubMed

    Fan, Lihong; Yang, Jing; Wu, Huan; Hu, Zhihai; Yi, Jiayan; Tong, Jun; Zhu, Xiaoming

    2015-08-01

    Quaternary ammonium chitosan (HACC)/polyvinyl alcohol (PVA)/polyethylene oxide (PEO) hydrogels were prepared using gamma radiation. The chemical structure of the hydrogels was characterized using FT-IR. The results revealed that HACC, PVA and PEO were perfectly compatible and interacted via the hydrogen bonds. As revealed by SEM, scaffolds with a homogeneous interconnected pore structure were obtained after lyophilizing the hydrogels. The influence of different radiation doses and weight ratios on properties including gel content, swelling ability, water evaporation rate and mechanical properties were investigated. It indicated that the hydrogels had the good swelling ability, water evaporation rate and mechanical properties. In vitro antibacterial activity assessment, the hydrogels exhibited a pronounced inhibitory effect against two bacteria (Staphylococcus aureus and Escherichia coli). Therefore, the hydrogels showed a promising potential to be applied as wound dressing. PMID:25895959

  9. Preparation and characterization of chitosan/gelatin/PVA hydrogel for wound dressings.

    PubMed

    Fan, Lihong; Yang, Huan; Yang, Jing; Peng, Min; Hu, Jin

    2016-08-01

    Chitosan (CS)/gelatin (Gel)/polyvinyl alcohol (PVA) hydrogels were prepared by the gamma irradiation method for usage in wound dressing applications. Chitosan and gelatin solution was mixed with poly(vinyl alcohol) (PVA) solution at different weight ratios of CS/Gel of 1:3, 1:2, 1:1, 2:1 and 3:1. The hydrogels irradiated at 40kGy. The structure of the hydrogels was characterized by using FT-IR and SEM. The CS/Gel/PVA hydrogels were characterized for physical properties and blood clotting activity. The tensile strength of CS/Gel/PVA hydrogel enhanced than on the basis of the Gel/PVA hydrogel. The highest tensile strength reached the 2.2Mpa. All hydrogels have shown a good coagulation effect. It takes only 5min for the BCI index to reached 0.032 only 5min when the weight ratio of CS/Gel was 1:1. It means that the hemostatic effect of hydrogels were optimal. And the hydrogrls also showed good pH-sensitivity, swelling ability and water evaporation rate. Therefore, this hydrogel showed a promising potential to be applied as wound dressing. PMID:27112893

  10. Ultrasonic characterization of silicate glasses, polymer composites and hydrogels

    NASA Astrophysics Data System (ADS)

    Lee, Wan Jae

    In many applications of material designing and engineering, high-frequency linear viscoelastic properties of materials are essential. Traditionally, the high-frequency properties are estimated through the time-temperature superposition (WLF equation) of low-frequency data, which are questionable because the existence of multi-phase in elastomer compounds. Moreover, no reliable data at high frequencies over MHz have been available thus far. Ultrasound testing is cost-effective for measuring high-frequency properties. Although both ultrasonic longitudinal and shear properties are necessary in order to fully characterize high-frequency mechanical properties of materials, longitudinal properties will be extensively explored in this thesis. Ultrasonic pulse echo method measures longitudinal properties. A precision ultrasonic measurement system has been developed in our laboratory, which allows us to monitor the in-situ bulk and/or surface properties of silicate glasses, polymer composites and even hydrogels. The system consists of a pulse-echo unit and an impedance measurement unit. A pulse echo unit is explored mainly. First, a systematic procedure was developed to obtain precise water wavespeed value. A calibration curve of water wavespeed as a function of temperature has been established, and water wavespeed at 23°C serves as a yardstick to tell whether or not a setup is properly aligned. Second, a sound protocol in calculating attenuation coefficient and beam divergence effects was explored using three kinds of silicate glass of different thicknesses. Then the system was applied to four composite slabs, two slabs for each type of fiberglass reinforced plastics, phenolic and polyester manufactured under different processing conditions: one was made by the normal procedures and the other with deliberate flaws such as voids, tapes and/or prepared at improper operation temperature and pressure. The experiment was conducted under the double blind test protocol. After

  11. Synthesis and patterning of hydrogel-nanoparticle composites

    NASA Astrophysics Data System (ADS)

    Martin, Lane A.; Mancini, Derrick C.; Rich, Lauren E.; Divan, Ralu

    2008-08-01

    We have developed a novel method for patterning nanoscale composite hydrogel materials on silicon through electron beam lithography. Gold particles were introduced into poly N-isopropylacrylamide (PNIPAam) patterned by e-beam lithography. By including BAC, the polymer can covalently bond to the colloidal gold nanoparticles. Such composites can be stable for long periods of time. We describe the structure, quality, and properties of the resulting patterned hydrogel-nanoparticle composite films.

  12. Synthesis of poly(N-isopropylacrylamide) hydrogels by radiation polymerization and cross-linking

    SciTech Connect

    Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi; Safranj, Agneza; Yoshida, Masaru; Omichi, Hideki

    1993-12-20

    Poly(N-isopropylacrylamide) [poly(NIPAAm)] shows a typical thermal reversibility of phase transition in aqueous solutions. That is, it precipitates from solution above a critical temperature called the lower critical solution temperature (LCST) and dissolves below this temperature. When it is cross-linked, the obtained hydrogel collapses above LCST, while it swells and expands below LCST. This hydrogel has received much attention recently and has been used as a model system to demonstrate the validity of theories describing the coil-globule transition, swelling of networks, and folding and unfolding of biopolymers. It has also been proposed for various applications ranging from controlled drug delivery to solute separation. Poly(NIPAAm) hydrogel is usually synthesized at room temperature from an aqueous solution of the monomer by using a redox initiator composed of ammonium persulfate and N,N,N{prime},N{prime}-tetramethylethylenediamine in the presence of N,N{prime}-methylenebisacrylamide as a cross-linker. Since the LCST of poly(NIPAAm) is around 32 C, the polymerization at room temperature proceeds in a homogeneous solution. Recently, poly(NIPAAm) hydrogels were synthesized by starting the polymerization below the LCST and then elevating the temperature above it, by which method macroporous gels with fast temperature response were obtained. The idea is to apply a radiation--induced polymerization method for the synthesis of poly(NIPAAm) hydrogels. This method offers unique advantages for synthesis: it is a simple and additive-free process at all temperatures, and the degree of cross-linking can be easily controlled by irradiation conditions. Therefore, radiation methods are especially attractive for the synthesis of hydrogels with potential biomedical application where the residual chemical initiators may contaminate the product. It is possible to combine into one step the synthesis and sterilization of the product, and it is economically competitive.

  13. Mechanical Characterization of Photo-crosslinkable Hydrogels with AFM

    NASA Astrophysics Data System (ADS)

    McKenna, Alyssa; Byun, Myunghwan; Hayward, Ryan; Aidala, Katherine

    2012-02-01

    Stimuli-responsive hydrogel films formed from photo-crosslinkable polymers are versatile materials for controlled drug delivery devices, three-dimensional micro-assemblies, and components in microfluidic systems. For such applications, it is important to understand both the mechanical properties and the dynamics responses of these materials. We describe the use of atomic force microscope (AFM) based indentation experiments to characterize the properties of poly(N-isopropylacrylamide) copolymer films, crosslinked by activation of pendent benzophenone units using ultraviolet light. In particular, we study how the elastic modulus of the material, determined using the Johnson, Kendall, and Roberts model, depends on UV dose, and simultaneously investigate stress relaxation in these materials in the context of viscoelastic and poroelastic relaxation models.

  14. Preparation and characterization of oxidized konjac glucomannan/carboxymethyl chitosan/graphene oxide hydrogel.

    PubMed

    Fan, Lihong; Yi, Jiayan; Tong, Jun; Zhou, Xiaoyu; Ge, Hongyu; Zou, Shengqiong; Wen, Huigao; Nie, Min

    2016-10-01

    Polysaccharide hydrogels have been widely used as biomaterials in biomedical field. In this article, composite hydrogels were prepared through the Schiff-base reaction between the aldehyde of oxidized konjac glucomannan (OKGM) and the amino of carboxymethyl chitosan (CMCS). Meanwhile, different amount of graphene oxide (GO) was added as nano-additive. The hydrogels have been characterized by various methods including Fourier transform infrared spectroscopy (FT-IR) and Surface morphology (SEM). Through the observation of SEM, the hydrogels' scaffolds present a homogeneous interconnected pore structure after lyophilizing. In addition, the influence of different GO content on properties including gelation time, swelling ability, water evaporation rate and mechanical properties was investigated. The results indicate that the hydrogels have short gelation time, appropriate swelling ability and water evaporation rate. Especially, the compressive strength and modulus increase 144% and 296% respectively as the GO content increase from 0 to 5mg/ml. Moreover, MTT assay was applied to evaluate the biocompatibility of hydrogels. The result indicate that hydrogels with GO show better biocompatibility. Therefore, due to the appropriate water absorption capacity, the similar compressive modulus with soft tissue and excellent biocompatibility, the composite hydrogels have potential application in wound dressings. PMID:27181577

  15. Characterization and behavior of composite hydrogel prepared from bamboo shoot cellulose and β-cyclodextrin.

    PubMed

    Liu, Shumin; Luo, Wenchao; Huang, Huihua

    2016-08-01

    Carboxymethyl cellulose was derived from bamboo shoot cellulose via chemical modification and was prepared into composite hydrogels by cross-linkage with β-cyclodextrin using epichlorohydrin as crossing agent. The structure of the prepared hydrogel was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results showed that the prepared composite hydrogel was sensitive to surrounding changes in pH value, temperature and ionic strength. Under the surroundings of low temperatures and high pH values, the prepared hydrogel had significant high swelling ratios (23338±988% at 15°C and 6937±112% at pH 8.0, respectively). In the solution of 0.1mol/L NaCl, the hydrogel showed the maximum water retention rate (48.73%). Sodium salicylate was used as the model drug to study the behaviors of hydrogel adsorption and release in simulated intestinal (at pH 7.4) and gastric liquid (at pH 1.8) surroundings. The prepared composite hydrogel exhibited higher drug release ratio in simulated intestinal liquid (63.09% after 380min) than in gastric liquid (22.09% after 400min). These pH responses of the prepared composite hydrogel showed its potential applications, especially as the drug carrier to attain control release of drugs under different surrounding conditions or organs in human body. PMID:27174909

  16. Synthesis of a novel acrylated abietic acid-g-bacterial cellulose hydrogel by gamma irradiation.

    PubMed

    Abeer, Muhammad Mustafa; Amin, Mohd Cairul Iqbal Mohd; Lazim, Azwan Mat; Pandey, Manisha; Martin, Claire

    2014-09-22

    Acrylated abietic acid (acrylated AbA) and acrylated abietic acid-grafted bacterial cellulose pH sensitive hydrogel (acrylated AbA-g-BC) were prepared by a one-pot synthesis. The successful dimerization of acrylic acid (AA) and abietic acid (AbA) and grafting of the dimer onto bacterial cellulose (BC) was confirmed by 13C solid state NMR as well as FT-IR. X-ray diffraction analysis showed characteristic peaks for AbA and BC; further, there was no effect of increasing amorphous AA content on the overall crystallinity of the hydrogel. Differential scanning calorimetry revealed a glass transition temperature of 80°C. Gel fraction and swelling studies gave insight into the features of the hydrogel, suggesting that it was suitable for future applications such as drug delivery. Scanning electron microscopy observations showed an interesting interpenetrating network within the walls of hydrogel samples with the lowest levels of AA and gamma radiation doses. Cell viability test revealed that the synthesized hydrogel is safe for future use in biomedical applications. PMID:24906785

  17. Characterization of gelatin-agar based phase separated hydrogel, emulgel and bigel: a comparative study.

    PubMed

    Wakhet, Senggam; Singh, Vinay K; Sahoo, Saikat; Sagiri, Sai Sateesh; Kulanthaivel, Senthilguru; Bhattacharya, Mrinal K; Kumar, Naresh; Banerjee, Indranil; Pal, Kunal

    2015-02-01

    The current study describes the in-depth characterization of agar-gelatin based co-hydrogels, emulgels and bigels to have an insight about the differences in the properties of the formulations. Hydrogels have been extensively studied as vehicle for controlled drug release, whereas, the concept of emulgels and bigels is relatively new. The formulations were characterized by scanning electron microscopy, FTIR spectroscopy, XRD and mechanical properties. The biocompatibility and the ability of the formulations to be used as drug delivery vehicle were also studied. The scanning electron micrographs suggested the presence of internal phases within the agar-gelatin composite matrices of co-hydrogel, emulgel and bigel. FTIR and XRD studies suggested higher crystallinity of emulgels and bigels. Electrical impedance and mechanical stability of the emulgel and the bigel was higher than the hydrogel. The prepared formulations were found to be biocompatible and suitable for drug delivery applications. PMID:25672596

  18. Transdermal thiol-acrylate polyethylene glycol hydrogel synthesis using near infrared light

    NASA Astrophysics Data System (ADS)

    Chung, Solchan; Lee, Hwangjae; Kim, Hyung-Seok; Kim, Min-Gon; Lee, Luke P.; Lee, Jae Young

    2016-07-01

    Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm-2) could induce gelation via a mixed-mode reaction with a small increase in temperature (~5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications.Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm-2) could induce gelation

  19. Carboxymethylated hyperbranched polysaccharide: Synthesis, solution properties, and fabrication of hydrogel.

    PubMed

    Tao, Yongzhen; Zhang, Ruquan; Yang, Wei; Liu, Hongtao; Yang, Hongjun; Zhao, Qinghua

    2015-09-01

    The periphery of hyperbranched polysaccharides has many end groups that can be functioned and used as sites to interact with their surroundings. A water-insoluble hyperbranched β-d-glucan, coded as TM3a, extracted from sclerotia of an edible fungus (Pleurotus tuber-regium), was fractionated and modified chemically to obtain carboxymethylated derivatives (CTM3a). The solution properties of the carboxymethylated polysaccharides were studied systematically in phosphate buffer saline at 37 °C. The results indicated that the carboxymethylated glucans still kept hyperbranched structure after carboxymethylation, and existed as a swollen sphere-like chain conformation. The introduction of carboxymethylated groups permitted the formation of hydrogels through crosslinking CTM3a and silk fibroin with carbodiimide chemistry. The resultant hydrogels with porous and interconnected structure displayed good mechanical and swelling properties. This work provides some valuable and fundamental information of the natural hyperbranched polysaccharide from mushroom for further application in biomedical devices and tissue engineering. PMID:26005154

  20. Synthesis and swelling behavior of xanthan-based hydrogels.

    PubMed

    Bueno, Vania Blasques; Bentini, Ricardo; Catalani, Luiz Henrique; Petri, Denise Freitas Siqueira

    2013-02-15

    In this work xanthan chains were crosslinked by esterification reaction at 165 °C either in the absence or in the presence of citric acid. Higher crosslinking density was obtained using citric acid, as evidenced by its lower swelling degree. Tensiometry, a very precise and sensitive technique, was applied to study swelling rates and diffusion mechanisms of water, which was initially quasi-Fickian, controlled by wicking properties, changing to Fickian or Anomalous, depending on hydrogel composition. Hydrogels swelling degree increased at high pH values, due to electrostatic repulsion and ester linkages rupture. Equilibrium swelling degree was affected by salts, depending on gel composition and kind of salt. Effects could be explained by interaction between ions and polymeric chains, EPA/EPD ability of water or osmotic gradient. PMID:23399133

  1. Electrical characterizations of smart hydrogel based on chitosan/poly(diallydimethylammonium chloride) in NaCl solutions

    NASA Astrophysics Data System (ADS)

    Yoon, Seoung Gil; Park, Sang Jun; Lim, Jun Young; Kim, Min Sup; Cho, Baek Hwan; Lee, Sang Min; Kim, Seon Jeong

    2004-07-01

    Temperature- and pH-responsive semi-interpenetrating polymer network (SIPN) hydrogels, constructed with chitosan (CS) and poly(diallyldimethylammonium chloride) (PDADMAC), were studied. The characterizations of the IPN hydrogels were investigated by swelling tests and bending experiments, under various conditions. When the swollen IPN hydrogel was placed between a pair of electrodes it exhibited bending behavior on the application of an electric field, which showed stepwise bending behavior depending on the magnitude of the electrical stimulus. In order to clarify the relationship between the equilibrium swelling ratio and bending behavior of the SIPN hydrogels, the state of water in the SIPN hydrogel was also investigated using differential scanning calorimetry (DSC).

  2. Characterization of hybrid hydrogel with different shape of particles after gamma-ray radiation

    NASA Astrophysics Data System (ADS)

    Kim, Donghyun; Lee, Hoik; Park, Hyemi; Sohn, Daewon

    2011-03-01

    Due to high specific surface area and the ability to absorb organic molecules, inorganic particles such as silica particle (spherical), imogolite (rodlike), and clay (fan shape) could be used as precursors for hydrogels. The hydrogel which had 3-D network structure was directly prepared by polymerization with acrylic acid (AA) on hydroxide surface of inorganic particles that was irradiated by gamma-ray at ambient condition. Surface of inorganic particles was used as sites of initiator and cross-linker to make hydrogel, so we don't need any additional additives to make hydrogel. The properties of hydrogel were characterized by small angle x-ray scattering (SAXS), universal testing machine (UTM), and Raman spectroscopy. By changing the inorganic particles/monomer ratio, the mechanical strength was significantly changed. The synthesized hydrogel can be elongated maximum 1800%. 2D SAXS pattern was different depending on the shape of inorganic particles. And the hydrogel swelled only in basic solutions at pH > 7.

  3. Radiation synthesis of poly(N-vinyl 2-pyrrolidone/itaconic acid) hydrogels and their controlled release behaviours

    NASA Astrophysics Data System (ADS)

    Şen, M.; Güven, O.

    1999-06-01

    N-vinyl 2-pyrrolidone/itaconic acid copolymeric hydrogels were prepared by irradiating the ternary mixtures of N-vinyl 2-pyrrolidone/itaconic acid/water by γ-rays at ambient temperature. For the characterization of network structure of these hydrogels, swelling properties in phosphate buffer solutions and molecular weight between crosslinks were investigated. Methylene Blue was used as a model drug for the investigation of controlled release behaviour of hydrogels. Specific Methylene Blue adsorption capacity of hydrogels are found to increase from 0.36 to 47.7 (mg MB/g gel) with increasing amount of itaconic acid in the gel system. The influence of molecular weight between cross-links, the concentration of ionizable groups, ionization and concentration of MB in the hydrogel were examined. The release studies show that one of the basic parameters affecting the drug release behaviour of hydrogels is the pH of the solution.

  4. Development and characterization of a naturally derived lung extracellular matrix hydrogel.

    PubMed

    Pouliot, Robert A; Link, Patrick A; Mikhaiel, Nabil S; Schneck, Matthew B; Valentine, Michael S; Kamga Gninzeko, Franck J; Herbert, Joseph A; Sakagami, Masahiro; Heise, Rebecca L

    2016-08-01

    The complexity and rapid clearance mechanisms of lung tissue make it difficult to develop effective treatments for many chronic pathologies. We are investigating lung derived extracellular matrix (ECM) hydrogels as a novel approach for delivery of cellular therapies to the pulmonary system. The main objectives of this study include effective decellularization of porcine lung tissue, development of a hydrogel from the porcine ECM, and characterization of the material's composition, mechanical properties, and ability to support cellular growth. Our evaluation of the decellularized tissue indicated successful removal of cellular material and immunogenic remnants in the ECM. The self-assembly of the lung ECM hydrogel was rapid, reaching maximum modulus values within 3 min at 37°C. Rheological characterization showed the lung ECM hydrogel to have a concentration dependent storage modulus between 15 and 60 Pa. The purpose of this study was to evaluate our novel ECM derived hydrogel and measure its ability to support 3D culture of MSCs in vitro and in vivo delivery of MSCs. Our in vitro experiments using human mesenchymal stem cells demonstrated our novel ECM hydrogel's ability to enhance cellular attachment and viability. Our in vivo experiments demonstrated that rat MSC delivery in pre-gel solution significantly increased cell retention in the lung over 24 h in an emphysema rat model. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1922-1935, 2016. PMID:27012815

  5. Nitrocinnamate-functionalized gelatin: synthesis and "smart"hydrogel formation via photo-cross-linking.

    PubMed

    Gattás-Asfura, Kerim M; Weisman, Eric; Andreopoulos, Fotios M; Micic, Miodrag; Muller, Bill; Sirpal, Sanjeev; Pham, Si M; Leblanc, Roger M

    2005-01-01

    Gelatin having p-nitrocinnamate pendant groups (Gel-NC) was prepared via an efficient one-pot synthesis, yield >87%. (1)H NMR data indicated that 1 mol of gelatin was modified with 18 +/- 6 mol of the photosensitive group. Upon exposure to low-intensity 365 nm UV light and in the absence of photoinitiators or catalysts, Gel-NC cross-linked within minutes into a gelatin-based hydrogel as monitored by UV-vis spectroscopy. The degree of swelling of this biodegradable hydrogel in aqueous solutions responded to changes in Gel-NC concentration levels, the ionic strength of the aqueous solutions, and photo-cross-linking time. Topography changes associated with phase transition resulting from "photocleavage" of the hydrogel network with 254 nm UV light were studied with AFM. Both Gel-NC and its hydrogel expressed low toxicity to human neonatal fibroblast cells. In addition, gelatin-based microgels were prepared via the photo-cross-linking of Gel-NC within inverse micelles. PMID:15877371

  6. Dopant-Enabled Supramolecular Approach for Controlled Synthesis of Nanostructured Conductive Polymer Hydrogels.

    PubMed

    Wang, Yaqun; Shi, Ye; Pan, Lijia; Ding, Yu; Zhao, Yu; Li, Yun; Shi, Yi; Yu, Guihua

    2015-11-11

    Conducting polymer hydrogels emerge as a novel class of polymeric materials that show great potential in many energy, environmental, and biomedical devices. We describe here for the first time a general supramolecular approach toward controlled in situ synthesis of one-dimensional nanostructured conductive hydrogels (polypyrrole (PPy) as a model system) using a rational dopant counterion, which is a disc-shaped liquid crystal molecular copper phthalocyanine-3,4',4″,4‴-tetrasulfonic acid tetrasodium salt (CuPcTs). The dopant molecule CuPcTs cross-linked the PPy chains to form a three-dimensional network that gelated into a hydrogel. The PPy hydrogel could be synthesized in bulk quantities with uniform morphology of self-assembled interconnected nanofibers. The tetra-functional dopant favors a supramolecular self-assembly mechanism to form one-dimensional PPy nanostructures. Furthermore, the enhanced interchain charge transport of CuPcTs doped PPy resulted in greatly enhanced conductivity and pseudocapacitance compared with pristine PPy. PMID:26505784

  7. Preparation, characterization, and in vitro enzymatic degradation of chitosan-gelatine hydrogel scaffolds as potential biomaterials.

    PubMed

    Gorgieva, Selestina; Kokol, Vanja

    2012-07-01

    The crosslinking of chitosan (CHT) and gelatin (GEL) accomplished with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was investigated and optimized in relation to hydrogels stability by varying the CHT/GEL mass ratio and the EDC/NHS molar ratio at different and constant EDC concentrations. Hydrogels were also fabricated in the presence of α-tocopherol to assess the release mechanism of a lipophilic drug from a highly-hydrophilic CHT/GEL hydrogel network. Alterations in the physico-chemical properties of hydrogels were characterized by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR), and their biostability was studied within a simulated body-fluid solution (PBS of pH 7.4) at 37 °C for 24 h by evaluating the degree of swelling, followed by topography and morphology characterization using scanning electron microscopy (SEM). The analysis confirmed the formation of a modulated hydrogels porosity using different freezing temperatures prior to lyophilization. The in vitro degradation behaviors of the hydrogels were investigated for up to 5 weeks using collagenase, lysozyme, and N-acetyl-β-D-glucosaminidase by monitoring the weight-losses of hydrogels and their degradation products, being identified by UV-Vis spectroscopy and high-performance liquid chromatography (HPLC) as well as the pH monitoring of degraded solutions. It was observed that an inner morphological hydrogel structure influences their swelling and degradation behavior, which is additionally reduced by in-gel-embedded α-tocopherol because of hydrophobic interactions with their constituents, and hindering the effect on collagenase activity. PMID:22447615

  8. Thermoresponsive, in situ crosslinkable hydrogels based on N-isopropylacrylamide: Fabrication, characterization and mesenchymal stem cell encapsulation

    PubMed Central

    Klouda, Leda; Perkins, Kevin R.; Watson, Brendan M.; Hacker, Michael C.; Bryant, Stephanie J.; Raphael, Robert M.; Kasper, F. Kurtis; Mikos, Antonios G.

    2011-01-01

    Hydrogels that solidify in response to a dual, physical and chemical, mechanism upon temperature increase were fabricated and characterized. The hydrogels were based on N-isopropylacrylamide, which renders them thermoresponsive, and contained covalently crosslinkable moieties in the macromers. The effects of the macromer end group, namely acrylate or methacrylate, and the fabrication conditions were investigated on the degradative and swelling properties of the hydrogels. The hydrogels exhibited higher swelling below their lower critical solution temperature (LCST). When immersed in cell culture media at physiological temperature, which was above their LCST, hydrogels showed constant swelling and no degradation over eight weeks, with methacrylated hydrogels having higher swelling than their acrylated analogs. In addition, hydrogels immersed in cell culture media under the same conditions showed lower swelling as compared to phosphate buffered saline. The interplay between chemical crosslinking and thermally induced phase separation affected the swelling characteristics of hydrogels in different media. Mesenchymal stem cells encapsulated in the hydrogels in vitro were viable over three weeks and markers of osteogenic differentiation were detected when the cells were cultured with osteogenic supplements. Hydrogel mineralization in the absence of cells was observed in cell culture medium with the addition of fetal bovine serum and β-glycerol phosphate. The results suggest that these hydrogels may be suitable as carriers for cell delivery in tissue engineering. PMID:21187170

  9. Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography.

    PubMed

    Hong, Xiaowei; Stegemann, Jan P; Deng, Cheri X

    2016-05-01

    Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger's viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials. PMID:26928595

  10. Optical characterization of porous silicon monolayers decorated with hydrogel microspheres

    NASA Astrophysics Data System (ADS)

    Balderas-Valadez, Ruth F.; Weiler, Markus; Agarwal, Vivechana; Pacholski, Claudia

    2014-08-01

    The optical response of porous silicon (pSi) films, covered with a quasi-hexagonal array of hydrogel microspheres, to immersion in ethanol/water mixtures was investigated. For this study, pSi monolayers were fabricated by electrochemical etching, stabilized by thermal oxidation, and decorated with hydrogel microspheres using spin coating. Reflectance spectra of pSi samples with and without deposited hydrogel microspheres were taken at normal incidence. The employed hydrogel microspheres, composed of poly-N-isopropylacrylamide (polyNIPAM), are stimuli-responsive and change their size as well as their refractive index upon exposure to alcohol/water mixtures. Hence, distinct differences in the interference pattern of bare pSi films and pSi layers covered with polyNIPAM spheres could be observed upon their immersion in the respective solutions using reflective interferometric Fourier transform spectroscopy (RIFTS). Here, the amount of reflected light (fast Fourier transform (FFT) amplitude), which corresponds to the refractive index contrast and light scattering at the pSi film interfaces, showed distinct differences for the two fabricated samples. Whereas the FFT amplitude of the bare porous silicon film followed the changes in the refractive index of the surrounding medium, the FFT amplitude of the pSi/polyNIPAM structure depended on the swelling/shrinking of the attached hydrogel spheres and exhibited a minimum in ethanol-water mixtures with 20 wt% ethanol. At this value, the polyNIPAM microgel is collapsed to its minimum size. In contrast, the effective optical thickness, which reflects the effective refractive index of the porous layer, was not influenced by the attached hydrogel spheres.

  11. Iron-Based Redox Polymerization of Acrylic Acid for Direct Synthesis of Hydrogel/Membranes, and Metal Nanoparticles for Water Treatment

    PubMed Central

    Hernández, Sebastián; Papp, Joseph K.; Bhattacharyya, Dibakar

    2014-01-01

    Functionalized polymer materials with ion exchange groups and integration of nano-structured materials is an emerging area for catalytic and water pollution control applications. The polymerization of materials such as acrylic acid often requires persulfate initiator and a high temperature start. However, is generally known that metal ions accelerate such polymerizations starting from room temperature. If the metal is properly selected, it can be used in environmental applications adding two advantages simultaneously. This paper deals with this by polymerizing acrylic acid using iron as accelerant and its subsequent use for nanoparticle synthesis in hydrogel and PVDF membranes. Characterizations of hydrogel, membranes and nanoparticles were carried out with different techniques. Nanoparticles sizes of 30–60 nm were synthesized. Permeability and swelling measurements demonstrate an inverse relationship between hydrogel mesh size (6.30 to 8.34 nm) and membrane pores (222 to 110 nm). Quantitative reduction of trichloroethylene/chloride generation by Fe/Pd nanoparticles in hydrogel/membrane platforms was also performed. PMID:24954975

  12. Recent Advances in the Synthesis and Biomedical Applications of Nanocomposite Hydrogels

    PubMed Central

    Spizzirri, Umile Gianfranco; Curcio, Manuela; Cirillo, Giuseppe; Spataro, Tania; Vittorio, Orazio; Picci, Nevio; Hampel, Silke; Iemma, Francesca; Nicoletta, Fiore Pasquale

    2015-01-01

    Hydrogels sensitive to electric current are usually made of polyelectrolytes and undergo erosion, swelling, de-swelling or bending in the presence of an applied electric field. The electrical conductivity of many polymeric materials used for the fabrication of biomedical devices is not high enough to achieve an effective modulation of the functional properties, and thus, the incorporation of conducting materials (e.g., carbon nanotubes and nanographene oxide) was proposed as a valuable approach to overcome this limitation. By coupling the biological and chemical features of both natural and synthetic polymers with the favourable properties of carbon nanostructures (e.g., cellular uptake, electromagnetic and magnetic behaviour), it is possible to produce highly versatile and effective nanocomposite materials. In the present review, the recent advances in the synthesis and biomedical applications of electro-responsive nanocomposite hydrogels are discussed. PMID:26473915

  13. Keratin sponge/hydrogel part 1. fabrication and characterization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Keratin sponge/hydrogel products formed by either the oxidation or reduction of U.S. domestic fine- or coarse-grade wool exhibited distinctively different topologies and molecular weights of 6- 8 kDa and 40-60 kDa, each with unique macro-porous structure and microstructural behaviors. The sponge/ ...

  14. Flow and Thixotropic Parameters for Rheological Characterization of Hydrogels.

    PubMed

    Ghica, Mihaela Violeta; Hîrjău, Mircea; Lupuleasa, Dumitru; Dinu-Pîrvu, Cristina-Elena

    2016-01-01

    The goal of this paper was to design several sodium carboxymethylcellulose hydrogels containing a BCS class II model drug and to evaluate their flow and thixotropic properties. The rheological measurements were performed at two temperatures (23 °C and 37 °C), using a rotational viscometer. The hydrogels were stirred at different time intervals (10 s, 2, 5, 10 and 20 min at 23 °C, and 10 s, 2 and 5 min at 37 °C), with a maximum rotational speed of 60 rpm, and the corresponding forward and backward rheograms were recorded as shear stress vs. shear rate. For all hydrogels, the rheological data obtained at both temperatures showed a decrease of viscosity with the increase of the shear rate, highlighting a pseudoplastic behaviour. The flow profiles viscosity vs. shear rate were quantified through power law model, meanwhile the flow curves shear stress vs. shear rate were assessed by applying the Herschel-Bulkley model. The thixotropic character was evaluated through different descriptors: thixotropic area, thixotropic index, thixotropic constant and destructuration thixotropic coefficient. The gel-forming polymer concentration and the rheological experiments temperature significantly influence the flow and thixotropic parameters values of the designed hydrogels. The rheological characteristics described have an impact on the drug release microenvironment and determine the stasis time at the application site. PMID:27322222

  15. Mussel-inspired synthesis of polydopamine-functionalized graphene oxide hydrogel as broad-spectrum antimicrobial material

    NASA Astrophysics Data System (ADS)

    Wang, Xinpeng; Liu, Zhiming; Zhong, Huiqing; Guo, Zhouyi; Yuan, Xiaochan

    2014-09-01

    Recently, three-dimensional GO-based hydrogels have attracted great attention due to the unique advantages. It is generally know that bacteria are everywhere and many of them could cause the diseases and threaten human health. However, developing new antibacterial materials with high-efficiency, low cost, broad-spectrum, and easy recycling is still a great challenge. Herein, inspired by mussel, we synthesized benzalkonium bromide/polydopamine/reduced graphene oxide hydrogel (BKB/PDA/rGOG). The as-prepared three-dimensional hydrogels were characterized by scanning eletron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The resultant hydrogels exhibited strong antibacterial effects to both Gram-negative and Gram-positive bacteria due to the synergistic effect of graphene oxide and benzalkonium bromide. In addition, the resultant hydrogels could be removed easily from the resolution, which was undoubtedly good news for industry application.

  16. Development and Characterization of UHMWPE Fiber-Reinforced Hydrogels For Meniscal Replacement

    NASA Astrophysics Data System (ADS)

    Holloway, Julianne Leigh

    Meniscal tears are the most common orthopedic injuries to the human body. The current treatment of choice, however, is a partial meniscectomy that leads to osteoarthritis proportional to the amount of tissue removed. As a result, there is a significant clinical need to develop materials capable of restoring the biomechanical contact stress distribution to the knee after meniscectomy and preventing the onset of osteoarthritis. In this work, a fiber-reinforced hydrogel-based synthetic meniscus was developed that allows for tailoring of the mechanical properties and molding of the implant to match the size, shape, and property distribution of the native tissue. Physically cross-linked poly(vinyl alcohol) (PVA) hydrogels were reinforced with ultrahigh molecular weight polyethylene (UHMWPE) fibers and characterized in compression (0.1-0.8 MPa) and tension (0.1-250 MPa) showing fine control over mechanical properties within the range of the human meniscus. Morphology and crystallinity analysis of PVA hydrogels showed increases in crystallinity and PVA densification, or phase separation, with freeze-thaw cycles. A comparison of freeze-thawed and aged, physically cross-linked hydrogels provided insight on both crystallinity and phase separation as mechanisms for PVA gelation. Results indicated both mechanisms independently contributed to hydrogel modulus for freeze-thawed hydrogels. In vitro swelling studies were performed using osmotic solutions to replicate the swelling pressure present in the knee. Minimal swelling was observed for hydrogels with a PVA concentration of 30-35 wt%, independently of hydrogel freeze-thaw cycles. This allows for independent tailoring of hydrogel modulus and pore structure using freeze-thaw cycles and swelling behavior using polymer concentration to match a wide range of properties needed for various soft tissue applications. The UHMWPE-PVA interface was identified as a significant weakness. To improve interfacial adhesion, a novel

  17. Preparation and characterization of superporous hydrogels as gastroretentive drug delivery system for rosiglitazone maleate

    PubMed Central

    Vishal Gupta, N.; Shivakumar, H.G.

    2010-01-01

    Background and the purpose of the study Many drugs which have narrow therapeutic window and are absorbed mainly in stomach have been developed as gastroretentive delivery system. Rosiglitazone maleate, an anti-diabetic, is highly unstable at basic pH and is extensively absorbed from the stomach. Hence there is a need to develop a gastroretentive system. In this study a superporous hydrogel was developed as a gastroretentive drug delivery system. Methods Chitosan/poly(vinyl alcohol) interpenetrating polymer network type superporous hydrogels were prepared using a gas foaming method employing glyoxal as the crosslinking agent for Rosiglitazone maleate. Sodium bicarbonate was applied as a foaming agent to introduce the porous structure. Swelling behaviors of superporous hydrogel in acidic solution were studied to investigate their applications for gastric retention device. The optimum preparation condition of superporous hydrogels was obtained from the gelation kinetics. FT-IR, scanning electron microscopy, porosity and swelling ratio studies were used to characterize these polymers. In vitro drug release studies were also carried out. Results The introduction of a small amount of Poly(Vinyl Alcohol) enhanced the mechanical strength but slightly reduced the swelling ratio. The prepared superporous hydrogels were highly sensitive to pH of swelling media, and showed reversible swelling and de-swelling behaviors maintaining their mechanical stability. The degradation kinetics in simulated gastric fluid showed that it had biodegradability. Swelling was dependent on the amount of chitosan and crosslinker. The drug release from superporous hydrogels was sustained for 6 hrs. Major Conclusion The studies showed that chitosan-based superporous hydrogels could be used as a gastroretentive drug delivery system for rosiglitazone maleate in view of their swelling and prolonged drug release characteristics in acidic pH. PMID:22615618

  18. Water-in-Water Emulsion Based Synthesis of Hydrogel Nanospheres with Tunable Release Kinetics

    NASA Astrophysics Data System (ADS)

    Aydın, Derya; Kızılel, Seda

    2016-06-01

    Poly(ethylene glycol) (PEG) micro/nanospheres have several unique advantages as polymer based drug delivery systems (DDS) such as tunable size, large surface area to volume ratio, and colloidal stability. Emulsification is one of the widely used methods for facile synthesis of micro/nanospheres. Two-phase aqueous system based on polymer-polymer immiscibility is a novel approach for preparation of water-in-water (w/w) emulsions. This method is promising for the synthesis of PEG micro/nanospheres for biological systems, since the emulsion is aqueous and do not require organic solvents or surfactants. Here, we report the synthesis of nano-scale PEG hydrogel particles using w/w emulsions using phase separation of dextran and PEG prepolymer. Dynamic light scattering (DLS) and scaning electron microscopy (SEM) results demonstrated that nano-scale hydrogel spheres could be obtained with this approach. We investigated the release kinetics of a model drug, pregabalin (PGB) from PEG nanospheres and demonstrated the influence of polymerization conditions on loading and release of the drug as well as the morphology and size distribution of PEG nanospheres. The experimental drug release data was fitted to a stretched exponential function which suggested high correlation with experimental results to predict half-time and drug release rates from the model equation. The biocompatibility of nanospheres on human dermal fibroblasts using cell-survival assay suggested that PEG nanospheres with altered concentrations are non-toxic, and can be considered for controlled drug/molecule delivery.

  19. Transdermal thiol-acrylate polyethylene glycol hydrogel synthesis using near infrared light.

    PubMed

    Chung, Solchan; Lee, Hwangjae; Kim, Hyung-Seok; Kim, Min-Gon; Lee, Luke P; Lee, Jae Young

    2016-08-01

    Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm(-2)) could induce gelation via a mixed-mode reaction with a small increase in temperature (∼5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications. PMID:27389611

  20. Synthesis of carboxymethylcellulose/acrylic acid hydrogels with superabsorbent properties by radiation-initiated crosslinking

    NASA Astrophysics Data System (ADS)

    Fekete, Tamás; Borsa, Judit; Takács, Erzsébet; Wojnárovits, László

    2016-07-01

    Superabsorbent hydrogels were prepared by gamma irradiation from aqueous solutions of carboxymethylcellulose (CMC) and acrylic acid (AAc) with varying CMC:AAc ratio. By partially replacing the CMC with AAc the gelation increased and led to a higher gel fraction and lower water uptake. Moreover, the gelation required significantly milder synthesis conditions. Decreasing both the dose and the solute concentration in the presence of AAc led to gels with higher gel fraction and higher degree of swelling compared to pure CMC gels. Increasing the AAc content up to 10% proved to be very effective, while very high AAc content (over 50%) hindered the gelation process.

  1. Preparation and characterization of imogolite/DNA hybrid hydrogels.

    PubMed

    Jiravanichanun, Nattha; Yamamoto, Kazuya; Kato, Kenichi; Kim, Jungeun; Horiuchi, Shin; Yah, Weng-On; Otsuka, Hideyuki; Takahara, Atsushi

    2012-01-01

    Imogolite is one of the clay minerals contained in volcanic ash soils. The novel hybrid hydrogels were prepared from imogolite nanofibers and DNA by utilizing strong interaction between the aluminol groups on imogolite surface and phosphate groups of DNA. The hybrid hydrogels of imogolite and DNA were prepared in various feed ratios, and their physicochemical properties and molecular aggregation states were investigated in both dispersion and gel states. The maximum DNA content in the hybrid gels was shown in equivalent molar ratio of imogolite and DNA. The physical properties of the hybrid gels were changed by varying DNA blend ratios. In the dispersion state, the hybrid gels showed a fibrous structure of imogolite, whereas a continuous network structure was observed in pure imogolite, indicating that the hybrid with DNA enhanced the dispersion of imogolite. In the gel state, DNA and imogolite nanofibers formed a 3D network structure. PMID:22148683

  2. Development and characterization of a new hydrogel based on galactomannan and κ-carrageenan.

    PubMed

    Soares, Paulo A G; de Seixas, José R P C; Albuquerque, Priscilla B S; Santos, Gustavo R C; Mourão, Paulo A S; Barros, Wilson; Correia, Maria T S; Carneiro-da-Cunha, Maria G

    2015-12-10

    A new hydrogel based on two natural polysaccharides was prepared in aqueous medium with 1.7% (w/v) galactomannan (from Cassia grandis seeds) and different concentrations of κ-carrageenan (0.3, 0.4 and 0.5%w/v), CaCl2 (0.0, 0.1 and 0.2M) and pH (5.0, 5.5 and 6.0), using a full factorial design based on rheological parameters. The best formulation was obtained with 1.7% (w/v) galactomannan and 0.5% (w/v) κ-carrageenan, containing 0.2M CaCl2 at pH 5.0. Nuclear magnetic resonance and scanning electron microscopy where used in order to characterize the hydrogel formulation. A shelf life study was carried out with this formulation along 90 days-period of storage at 4 °C, evaluating pH, color, microbial contamination and rheology. This hydrogel showed no significant changes in pH, no microbial contamination and became more translucent along the aging. Analyses by nuclear magnetic resonance and rheology showed a larger organization of the polysaccharides in the hydrogel matrix. The results demonstrated that this hydrogel was stable with possible applications in medical and cosmetic fields. PMID:26428171

  3. Preparation and characterization of chitin hydrogels by water vapor induced gelation route.

    PubMed

    Vachoud, L; Pochat-Bohatier, C; Chakrabandhu, Y; Bouyer, D; David, L

    2012-11-01

    A novel method of chitin hydrogel preparation, called vapor induced gelation, using exposure of chitin/N-methyl-pyrrolidone/LiCl solution to water vapors is presented. Compared to gelation induced by direct immersion in water, hydrogels are characterized by smaller deformation during gelation (area shrinkage is 20% instead of 65%), larger water volume fraction (75 instead of 62%, v/v) and 10 times higher apparent compression moduli. Their nanostructure consists of thicker and larger crystalline platelets network (thickness=37 Å, apparent coherent crystalline size L₀₂₀=145 Å) comparatively to direct immersion gels (25 Å and L₀₂₀=95 Å). Drug delivery potential of chitin hydrogels was determined for non-interactive low molecular molecules. PMID:22676995

  4. Hybrid hydrogels produced by ionizing radiation technique

    NASA Astrophysics Data System (ADS)

    Oliveira, M. J. A.; Amato, V. S.; Lugão, A. B.; Parra, D. F.

    2012-09-01

    The interest in biocompatible hydrogels with particular properties has increased considerably in recent years due to their versatile applications in biomedicine, biotechnology, pharmacy, agriculture and controlled release of drugs. The use of hydrogels matrices for particular drug-release applications has been investigated with the synthesis of modified polymeric hydrogel of PVAl and 0.5, 1.0, 1.5% nano-clay. They were processed using gamma radiation from Cobalt-60 source at 25 kGy dose. The characterization of the hydrogels was conducted and toxicity was evaluated. The dried hydrogel was analyzed for thermogravimetry analysis (TGA), infrared spectroscopy (FTIR) and swelling in solutions of different pH. The membranes have no toxicity. The nano-clay influences directly the equilibrium swelling.

  5. Characterization of low-molecular-weight hyaluronic acid-based hydrogel and differential stem cell responses in the hydrogel microenvironments.

    PubMed

    Kim, Jungju; Park, Yongdoo; Tae, Giyoong; Lee, Kyu Back; Hwang, Chang Mo; Hwang, Soon Jung; Kim, In Sook; Noh, Insup; Sun, Kyung

    2009-03-15

    Hyaluronic acid is a natural glycosaminoglycan involved in biological processes. Low-molecular-weight hyaluronic acid (10 and 50 kDa)-based hydrogel was synthesized using derivatized hyaluronic acid. Hyaluronic acid was acrylated by two steps: (1) introduction of an amine group using adipic acid dihydrazide, and (2) acrylation by N-acryloxysuccinimide. Injectable hyaluronic acid-based hydrogel was prepared by using acrylated hyaluronic acid and poly(ethylene glycol) tetra-thiols via Michael-type addition reaction. Mechanical properties of the hydrogel were evaluated by varying the molecular weight of acrylated hyaluronic acid (10 and 50 kDa) and the weight percent of hydrogel. Hydrogel based on 50-kDa hyaluronic acid showed the shortest gelation time and the highest complex modulus. Next, human mesenchymal stem cells were cultured in cell-adhesive RGD peptide-immobilized hydrogels together with bone morphogenic protein-2 (BMP-2). Cells cultured in the RGD/BMP-2-incorporated hydrogels showed proliferation rates higher than that of control or RGD-immobilized hydrogels. Real-time RT-PCR showed that the expression of osteoblast marker genes such as CBFalpha1 and alkaline phosphatase was increased in hyaluronic acid-based hydrogel, and the expression level was dependent on the molecular weight of hyaluronic acid, RGD peptide, and BMP-2. This study indicates that low-molecular-weight hyaluronic acid-based hydrogel can be applied to tissue regeneration as differentiation guidance materials of stem cells. PMID:18384163

  6. Chemically cross-linked silk fibroin hydrogel with enhanced elastic properties, biodegradability, and biocompatibility

    PubMed Central

    Kim, Min Hee; Park, Won Ho

    2016-01-01

    In this study, the synthesis of silk fibroin (SF) hydrogel via chemical cross-linking reactions of SF due to gamma-ray (γ-ray) irradiation was investigated, as were the resultant hydrogel’s properties. Two different hydrogels were investigated: physically cross-linked SF hydrogel and chemically cross-linked SF hydrogel irradiated at different doses of γ-rays. The effects of the irradiation dose and SF concentration on the hydrogelation of SF were examined. The chemically cross-linked SF hydrogel was compared with the physically cross-linked one with regard to secondary structure and gel strength. Furthermore, the swelling behavior, crystallinity, and biodegradation of the SF hydrogels were characterized. To assay cell proliferation, the cell viability of human mesenchymal stem cells on the lyophilized SF hydrogel scaffolds was evaluated, and no significant cytotoxicity against human mesenchymal stem cells was observed. PMID:27382283

  7. Combined numerical and experimental biomechanical characterization of soft collagen hydrogel substrate.

    PubMed

    Castro, A P G; Laity, P; Shariatzadeh, M; Wittkowske, C; Holland, C; Lacroix, D

    2016-04-01

    This work presents a combined experimental-numerical framework for the biomechanical characterization of highly hydrated collagen hydrogels, namely with 0.20, 0.30 and 0.40% (by weight) of collagen concentration. Collagen is the most abundant protein in the extracellular matrix of animals and humans. Its intrinsic biocompatibility makes collagen a promising substrate for embedding cells within a highly hydrated environment mimicking natural soft tissues. Cell behaviour is greatly influenced by the mechanical properties of the surrounding matrix, but the biomechanical characterization of collagen hydrogels has been challenging up to now, since they present non-linear poro-viscoelastic properties. Combining the stiffness outcomes from rheological experiments with relevant literature data on collagen permeability, poroelastic finite element (FE) models were developed. Comparison between experimental confined compression tests available in the literature and analogous FE stress relaxation curves showed a close agreement throughout the tests. This framework allowed establishing that the dynamic shear modulus of the collagen hydrogels is between 0.0097 ± 0.018 kPa for the 0.20% concentration and 0.0601 ± 0.044 kPa for the 0.40% concentration. The Poisson's ratio values for such conditions lie within the range of 0.495-0.485 for 0.20% and 0.480-0.470 for 0.40%, respectively, showing that rheology is sensitive enough to detect these small changes in collagen concentration and thus allowing to link rheology results with the confined compression tests. In conclusion, this integrated approach allows for accurate constitutive modelling of collagen hydrogels. This framework sets the grounds for the characterization of related hydrogels and to the use of this collagen parameterization in more complex multiscale models. PMID:26914710

  8. Design, preparation and characterization of ulvan based thermosensitive hydrogels.

    PubMed

    Morelli, Andrea; Betti, Margherita; Puppi, Dario; Chiellini, Federica

    2016-01-20

    The present study is focused on the exploitation and conversion of sulphated polysaccharides obtained from waste algal biomass into high value added material for biomedical applications. ulvan, a sulphated polysaccharide extracted from green seaweeds belonging to Ulva sp. was selected as a suitable material due to its chemical versatility and widely ascertained bioactivity. To date the present work represents the first successful attempt of preparation of ulvan-based hydrogels displaying thermogelling behaviour. ulvan was provided with thermogelling properties by grafting poly(N-isopropylacrylamide) chains onto its backbone as thermosensitive component. To this aim ulvan was properly modified with acryloyl groups to act as macroinitiator in the radical polymerization of N-isopropylacrylamide, induced by UV irradiation through a "grafting from" method. The thermogelling properties of the copolymer were investigated by thermal and rheological analyses. Sol-gel transition of the copolymer was found to occur at 30-31 °C thus indicating the feasibility of ulvan for being used as in-situ hydrogel forming systems for biomedical applications. PMID:26572453

  9. Characterization of a Functional Hydrogel Layer on a Silicon-Based Grating Waveguide for a Biochemical Sensor

    PubMed Central

    Hong, Yoo-Seung; Kim, Jongseong; Sung, Hyuk-Kee

    2016-01-01

    We numerically demonstrated the characteristics of a functional hydrogel layer on a silicon-based grating waveguide for a simple, cost-effective refractive index (RI) biochemical sensor. The RI of the functional hydrogel layer changes when a specific biochemical interaction occurs between the hydrogel-linked receptors and injected ligand molecules. The transmission spectral profile of the grating waveguide shifts depends on the amount of RI change caused by the functional layer. Our characterization includes the effective RI change caused by the thickness, functional volume ratio, and functional strength of the hydrogel layer. The results confirm the feasibility of, and set design rules for, hydrogel-assisted silicon-based grating waveguides. PMID:27322286

  10. Characterization of a Functional Hydrogel Layer on a Silicon-Based Grating Waveguide for a Biochemical Sensor.

    PubMed

    Hong, Yoo-Seung; Kim, Jongseong; Sung, Hyuk-Kee

    2016-01-01

    We numerically demonstrated the characteristics of a functional hydrogel layer on a silicon-based grating waveguide for a simple, cost-effective refractive index (RI) biochemical sensor. The RI of the functional hydrogel layer changes when a specific biochemical interaction occurs between the hydrogel-linked receptors and injected ligand molecules. The transmission spectral profile of the grating waveguide shifts depends on the amount of RI change caused by the functional layer. Our characterization includes the effective RI change caused by the thickness, functional volume ratio, and functional strength of the hydrogel layer. The results confirm the feasibility of, and set design rules for, hydrogel-assisted silicon-based grating waveguides. PMID:27322286

  11. Preparation and characterization of IPN hydrogels composed of chitosan and gelatin cross-linked by genipin.

    PubMed

    Cui, Li; Jia, Junfang; Guo, Yi; Liu, Yun; Zhu, Ping

    2014-01-01

    The interpenetrating polymer networks (IPN) hydrogels based on chitosan and gelatin using genipin as the cross-linker were prepared and characterized. The IPN formation of the genipin-cross-linked chitosan/gelatin hydrogel was confirmed by means of the instrinsic viscosity measurement, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and the ninhydrin assays. The instrinsic viscosity measurement, FT-IR and SEM suggested that chitosan and gelatin were miscible in the molecular level. The miscibility leads to the formation of IPN after cross-linking. FT-IR also examined the cross-linking mechanism of genipin with primary amino groups. The degree of cross-linking increased with increase genipin concentration. Swelling results revealed that the IPN hydrogels are pH-sensitive, exhibiting reversibility and rather rapidly response in swelling to pH changes. It is expected this IPN hydrogel has potential as controlled drug delivery system or as alternative sorbents for biomedical and environmental use as pH altered. PMID:24274476

  12. Matrix Synthesis and Characterization

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The role of NASA in the area of composite material synthesis; evaluation techniques; prediction analysis techniques; solvent-resistant tough composite matrix; resistance to paint strippers; acceptable processing temperature and pressure for thermoplastics; and the role of computer modeling and fiber interface improvement were discussed.

  13. Magnetic hydrogel with high coercivity

    SciTech Connect

    Sözeri, H.; Alveroğlu, E.; Kurtan, U.; Şenel, M.; Baykal, A.

    2013-08-01

    Highlights: • Polyacrylamide (PAAm) hydrogels containing magnetic BaFe{sub 12}O{sub 19} nanoparticles have been prepared. • Magnetization measurements reveal that hydrogels have hard magnetic properties with high coercivity. • Magnetic nanoparticles makes the gel more homogeneous and do not diffuse out of the gel during water intake. • These gels are useful in applications as wastewater treatment once gels are magnetized before its usage. - Abstract: This study investigates the synthesis and characterization of polyacrylamide (PAAm) hydrogels containing magnetic BaFe{sub 12}O{sub 19} nanoparticles. Structural, electrical, and magnetic characterization of the gels have been performed with X-ray powder diffractometry, scanning electron microscopy, DC conductivity, magnetization and fluorescence spectroscopy techniques. The preparation and characterization of polyacrylamide (PAAm) hydrogels that contain 5 and 10 mg BaFe{sub 12}O{sub 19} (16 and 21 nm diameter) nanoparticles are described herein. It is seen from the fluorescence spectra that, nanoparticles surrounded to pyranine molecules so that some of pyranine molecules could not bound to the polymer strands. Electrical measurements show that presence of nanoparticles make the gel more homogeneous. Magnetization measurements reveal that hydrogels have hard magnetic properties with quite high coercivity of 4.2 kOe, which does not change with swelling. This feature makes these gels useful in applications as wastewater treatment if they are magnetized before use.

  14. Synthesis and investigation of poly(N-isopropylacrylamide-co-N-vinylcarbazole) hydrogels morphological, fluorescence and electrical properties

    NASA Astrophysics Data System (ADS)

    Gökçeören, Argun Talat; Alveroglu, Esra

    2016-03-01

    In this study, poly(N-isopropylacrylamide-co-N-vinylcarbazole) gels were prepared and characterized with Fourier Transform Infrared Spectroscopy, Photoluminescence Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and DC conductivity methods. The synthesis and characterization results showed that the presence of NVCz moieties affected the thermal characteristics, topological properties and conductivity of the gels. The obtained NIPA hydrogel was found to swell in aqueous media for up to 80%, while the 50% NVCz incorporated sample swells up to 40%. Here we report that the fluorescence emission and electrical conductivity results attest the opportunity to manufacture a tunable biomedical materials. Since, the maximum peak at 350 nm red shifted to 385 nm, whilst a second peak appeared at 425 nm by the presence of the conductive PNVCz moieties allowing the possibility to control the fluorescence character of the gel. For instance an in-vivo drug release system tracking in a Fluorescence Image-Guided Surgery (FIGS) in which resolution deepness is essential in the visible wavelength could be extended when excited by means of a fluorophore compound.

  15. Characterization of a chondroitin sulfate hydrogel for nerve root regeneration.

    PubMed

    Conovaloff, Aaron; Panitch, Alyssa

    2011-10-01

    Brachial plexus injury is a serious medical problem that affects many patients annually, with most cases involving damage to the nerve roots. Therefore, a chondroitin sulfate hydrogel was designed to both serve as a scaffold for regenerating root neurons and deliver neurotrophic signals. Capillary electrophoresis showed that chondroitin sulfate has a dissociation constant in the micromolar range with several common neurotrophins, and this was determined to be approximately tenfold stronger than with heparin. It was also revealed that nerve growth factor exhibits a slightly stronger affinity for hyaluronic acid than for chondroitin sulfate. However, E8 chick dorsal root ganglia cultured in the presence of nerve growth factor revealed that ganglia cultured in chondroitin sulfate scaffolds showed more robust growth than those cultured in control gels of hyaluronic acid. It is hypothesized that, despite the stronger affinity of nerve growth factor for hyaluronic acid, chondroitin sulfate serves as a better scaffold for neurite outgrowth, possibly due to inhibition of growth by hyaluronic acid chains. PMID:21804177

  16. Characterization of a chondroitin sulfate hydrogel for nerve root regeneration

    NASA Astrophysics Data System (ADS)

    Conovaloff, Aaron; Panitch, Alyssa

    2011-10-01

    Brachial plexus injury is a serious medical problem that affects many patients annually, with most cases involving damage to the nerve roots. Therefore, a chondroitin sulfate hydrogel was designed to both serve as a scaffold for regenerating root neurons and deliver neurotrophic signals. Capillary electrophoresis showed that chondroitin sulfate has a dissociation constant in the micromolar range with several common neurotrophins, and this was determined to be approximately tenfold stronger than with heparin. It was also revealed that nerve growth factor exhibits a slightly stronger affinity for hyaluronic acid than for chondroitin sulfate. However, E8 chick dorsal root ganglia cultured in the presence of nerve growth factor revealed that ganglia cultured in chondroitin sulfate scaffolds showed more robust growth than those cultured in control gels of hyaluronic acid. It is hypothesized that, despite the stronger affinity of nerve growth factor for hyaluronic acid, chondroitin sulfate serves as a better scaffold for neurite outgrowth, possibly due to inhibition of growth by hyaluronic acid chains.

  17. Novel cross linked guar gum-g-poly(acrylate) porous superabsorbent hydrogels: Characterization and swelling behaviour in different environments.

    PubMed

    Chandrika, Ksv Poorna; Singh, Anupama; Rathore, Abhishek; Kumar, Anil

    2016-09-20

    A new series of eco-friendly cross linked guar gum-g-poly(acrylate) porous superabsorbent hydrogels was prepared by in situ grafting polymerization and cross-linking on to a natural guar gum employing N,N-methylene bis acrylamide as cross linker. Morphological and structural characterization of the prepared hydrogels (SPHs) done by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and solid state C(13) NMR spectroscopy confirmed formation of porous grafted and crosslinked hydrogel structure. Increase in cross linker concentration in the feed mass exhibited decrease in porosity and increase in density of the hydrogels. Swelling of an optimized hydrogel (SPH) in response to external stimuli namely, salt solutions, fertilizer solutions, temperature, and pH exhibited high swelling ratios in various environments. Swelling rate of the SPH was faster than the corresponding nonporous superabsorbent hydrogel. The prepared hydrogels can serve as excellent carriers of pesticides, fertilizers and agriculturally important microbes. Biocontrol formulations based on a representative SPH exhibited excellent shelf-life characteristics and bioefficacy against phytopathogenic fungus Pythium aphanidermatum. PMID:27261742

  18. Synthesis and biocompatibility of a biodegradable and functionalizable thermo-sensitive hydrogel.

    PubMed

    Sinha, Mantosh K; Gao, Jin; Stowell, Chelsea E T; Wang, Yadong

    2015-09-01

    Injectable thermal gels are a useful tool for drug delivery and tissue engineering. However, most thermal gels do not solidify rapidly at body temperature (37°C). We addressed this by synthesizing a thermo-sensitive, rapidly biodegrading hydrogel. Our hydrogel, poly(ethylene glycol)-co-poly(propanol serinate hexamethylene urethane) (EPSHU), is an ABA block copolymer comprising A, methoxy poly ethylene glycol group and B, poly (propanol L-serinate hexamethylene urethane). EPSHU was characterized by gel permeation chromatography for molecular weight and (1)H NMR and Fourier transformed infrared for structure. Rheological studies measured the phase transition temperature. In vitro degradation in cholesterol esterase and in Dulbecco's phosphate buffered saline (DPBS) was tracked using the average molecular weight measured by gel permeation chromatography. LIVE/DEAD and resazurin reduction assays performed on NIH 3T3 fibroblasts exposed to EPSHU extracts demonstrated no cytotoxicity. Subcutaneous implantation into BALB/cJ mice indicated good biocompatibility in vivo. The biodegradability and biocompatibility of EPSHU together make it a promising candidate for drug delivery applications that demand carrier gel degradation within months. PMID:26814023

  19. Synthesis and biocompatibility of a biodegradable and functionalizable thermo-sensitive hydrogel

    PubMed Central

    Sinha, Mantosh K.; Gao, Jin; Stowell, Chelsea E. T.; Wang, Yadong

    2015-01-01

    Injectable thermal gels are a useful tool for drug delivery and tissue engineering. However, most thermal gels do not solidify rapidly at body temperature (37°C). We addressed this by synthesizing a thermo-sensitive, rapidly biodegrading hydrogel. Our hydrogel, poly(ethylene glycol)-co-poly(propanol serinate hexamethylene urethane) (EPSHU), is an ABA block copolymer comprising A, methoxy poly ethylene glycol group and B, poly (propanol L-serinate hexamethylene urethane). EPSHU was characterized by gel permeation chromatography for molecular weight and 1H NMR and Fourier transformed infrared for structure. Rheological studies measured the phase transition temperature. In vitro degradation in cholesterol esterase and in Dulbecco's phosphate buffered saline (DPBS) was tracked using the average molecular weight measured by gel permeation chromatography. LIVE/DEAD and resazurin reduction assays performed on NIH 3T3 fibroblasts exposed to EPSHU extracts demonstrated no cytotoxicity. Subcutaneous implantation into BALB/cJ mice indicated good biocompatibility in vivo. The biodegradability and biocompatibility of EPSHU together make it a promising candidate for drug delivery applications that demand carrier gel degradation within months. PMID:26814023

  20. Facile synthesis of antibacterial chitosan/CuO bio-nanocomposite hydrogel beads.

    PubMed

    Farhoudian, Sana; Yadollahi, Mehdi; Namazi, Hassan

    2016-01-01

    CuO nanoparticles were synthesized in situ during the formation of physically cross-linked chitosan hydrogel beads using sodium tripolyphosphate as the cross-linker. The aim of the study was to investigate whether these nanocomposite beads have the potential to be used in drug delivery applications. The formation of CuO nanoparticles (CuONPs) in the hydrogels was confirmed by X-ray diffraction and scanning electron microscopy studies. SEM micrographs revealed the formation of CuONPs with size range of 10-25 nm within the hydrogel matrix. Furthermore, the antibacterial and swelling properties of the beads were studied. The prepared nanocomposite hydrogels showed a pH sensitive swelling behavior. The CuO nanocomposite hydrogels have rather higher swelling in different aqueous solutions in comparison with neat hydrogel. The nanocomposite hydrogels demonstrated good antibacterial effects against Escherichia coli and Staphylococcus aureus bacteria. PMID:26454107

  1. Rheological characterization of cataplasm bases composed of cross-linked partially neutralized polyacrylate hydrogel.

    PubMed

    Wang, Jian; Zhang, Hongqin; An, Dianyun; Yu, Jian; Li, Wei; Shen, Teng; Wang, Jianxin

    2014-10-01

    Viscoelasticity is a useful parameter for characterizing the intrinsic properties of the cross-linked polyacrylate hydrogel used in cataplasm bases. The aim of this study was to investigate the effects of various formulation parameters on the rheological characteristics of polyacrylate hydrogel. The hydrogel layers were formed using a partially neutralized polyacrylate (Viscomate(™)), which contained acrylic acid and sodium acrylate in different copolymerization ratios, as the cross-linked gel framework. Dihydroxyaluminum aminoacetate (DAAA), which produces aluminum ions, was used as the cross-linking agent. Rheological analyses were performed using a "stress amplitude sweep" and a "frequency sweep". The results showed that greater amounts of acrylic acid in the structure of Viscomate as well as higher concentrations of DAAA and Viscomate led to an increase in the elastic modulus (G'). However, greater amounts of acrylic acid in the structure of Viscomate and higher concentrations of DAAA had an opposite on the viscous modulus (G″); this might be owing to higher steric hindrance. The results of this study can serve as guidelines for the optimization of formulations for cataplasms. PMID:24865937

  2. Development, Fabrication, and Characterization of Hydrogel Based Piezoresistive Pressure Sensors with Perforated Diaphragms

    PubMed Central

    Orthner, M.P.; Buetefisch, Sebastian; Magda, J.; Rieth, L.W.; Solzbacher, F.

    2010-01-01

    Hydrogels have been demonstrated to swell in response to a number of external stimuli including pH, CO2, glucose, and ionic strength making them useful for detection of metabolic analytes. To measure hydrogel swelling pressure, we have fabricated and tested novel perforated diaphragm piezoresistive pressure sensor arrays that couple the pressure sensing diaphragm with a perforated semi-permeable membrane. The 2×2 arrays measure approximately 3 × 5 mm2 and consist of four square sensing diaphragms with widths of 1.0, 1.25, and 1.5 mm used to measure full scale pressures of 50, 25, and 5 kPa, respectively. An optimized geometry of micro pores was etched in silicon diaphragm to allow analyte diffusion into the sensor cavity where the hydrogel material is located. The 14-step front side wafer process was carried out by a commercial foundry service (MSF, Frankfurt (Oder), Germany) and diaphragm pores were created using combination of potassium hydroxide (KOH) etching and deep reactive ion etching (DRIE). Sensor characterization was performed (without the use of hydrogels) using a custom bulge testing apparatus that simultaneously measured deflection, pressure, and electrical output. Test results are used to quantify the sensor sensitivity and demonstrate proof-of-concept. Simulations showed that the sensitivity was slightly improved for the perforated diaphragm designs while empirical electrical characterization showed that the perforated diaphragm sensors were slightly less sensitive than solid diaphragm sensors. This discrepancy is believed to be due to the influence of compressive stress found within passivation layers and poor etching uniformity. The new perforated diaphragm sensors were fully functional with sensitivities ranging from 23 to 252 μV/V-kPa (FSO= 5 to 80mV), and show a higher nonlinearity at elevated pressures than identical sensors with solid diaphragms. Sensors (1.5×1.5 mm2) with perforated diaphragms (pores=40 μm) have a nonlinearity of

  3. Novel synthesis strategy for composite hydrogel of collagen/hydroxyapatite-microsphere originating from conversion of CaCO3 templates

    NASA Astrophysics Data System (ADS)

    Wei, Qingrong; Lu, Jian; Wang, Qiaoying; Fan, Hongsong; Zhang, Xingdong

    2015-03-01

    Inspired by coralline-derived hydroxyapatite, we designed a methodological route to synthesize carbonated-hydroxyapatite microspheres from the conversion of CaCO3 spherulite templates within a collagen matrix under mild conditions and thus constructed the composite hydrogel of collagen/hydroxyapatite-microspheres. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) were employed to confirm the successful generation of the carbonated hydroxyapatite phase originating from CaCO3, and the ratios of calcium to phosphate were tracked over time. Variations in the weight portion of the components in the hybrid gels before and after the phase transformation of the CaCO3 templates were identified via thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) shows these composite hydrogels have a unique multiscale microstructure consisting of a collagen nanofibril network and hydroxyapatite microspheres. The relationship between the hydroxyapatite nanocrystals and the collagen fibrils was revealed by transmission electron microscopy (TEM) in detail, and the selected area electron diffraction (SAED) pattern further confirmed the results of the XRD analyses which show the typical low crystallinity of the generated hydroxyapatite. This smart synthesis strategy achieved the simultaneous construction of microscale hydroxyapatite particles and collagen fibrillar hydrogel, and appears to provide a novel route to explore an advanced functional hydrogel materials with promising potentials for applications in bone tissue engineering and reconstruction medicine.

  4. Fabrication and characterization of cross-linkable hydrogel particles based on hyaluronic acid: potential application in vocal fold regeneration.

    PubMed

    Sahiner, Nurettin; Jha, Amit K; Nguyen, David; Jia, Xinqiao

    2008-01-01

    There is a critical need to engineer hyaluronic acid (HA)-based hydrogels with prolonged in vivo residence time, temporal release of therapeutics and matching viscoelasticity for use in vocal fold tissue engineering. We have previously demonstrated the synthesis and characterization of HA-based soft hydrogel particles (HGP) and particle cross-linked networks as injectable materials to treat vocal fold scarring. In this paper, we report a more versatile technique for preparing cross-linkable HA HGP with reduced sizes. HA HGP were synthesized via chemical cross-linking with divinyl sulfone using a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelle system in the presence of 1-heptanol. These HGP were rendered cross-linkable by introducing aldehyde groups via sodium periodate oxidation (oxHGP). The presence of aldehyde groups was confirmed by multi-photon confocal microscope upon fluorescence staining using cascade blue hydrazide. The aldehyde groups were used as reactive handles for covalent cross-linking with HA that has been previously modified with adipic acid dihydrazide (HADH). The resulting doubly cross-linked networks (DXN) are highly pliable and do not break until approx. 200-300% strain. The measured elastic modulus of the DXN is around 500 Pa, while the dynamic viscosity decreases linearly with frequency in log- log scale. The mechanical characteristics of DXN are similar to that of vocal fold lamina propria. In vitro cell-proliferation assays showed that the cross-linkable HA HGP did not adversely affect the proliferation of the cultured fibroblasts as assessed by MTT assay. A low-molecular-weight model drug, rhodamine 6G (R6G), was loaded into oxHGP, and its release was monitored using UV-Vis spectroscopy. R6G-loaded oxHGP maintained their ability to form DXN when mixed with the HAADH solution. Approximately 84% of entrapped R6G was liberated from oxHGP at a rate of 0.24%/min in the first 6 h. When encapsulated in the DXN, R6G was

  5. Synthesis of graphene peroxide and its application in fabricating super extensible and highly resilient nanocomposite hydrogels.

    PubMed

    Liu, Jiaqi; Chen, Caifeng; He, Changcheng; Zhao, Jing; Yang, Xiaojing; Wang, Huiliang

    2012-09-25

    Functionalized graphene has been considered as one of the most important materials for preparing polymer nanocomposites due to its unique physical structure and properties. To increase the interfacial interaction between polymer component and graphene oxide (GO) sheets, in situ grafting polymerization initiated by a free radical initiator immobilized on GO sheets is a better choice. We report a facile and effective strategy for preparing graphene peroxide (GPO) via the radiation-induced peroxidation of GO. The formation of peroxides on GO is proven by iodometric measurement and other characterizations. Using GPO as a polyfunctional initiating and cross-linking center, we obtained GO composite hydrogels exhibiting excellent mechanical properties, namely, very high tensile strength (0.2-1.2 MPa), extremely high elongations (2000-5300%), and excellent resilience. This work provides new insight into the fabrication of GO/polymer nanocomposites to fulfill the excellent mechanical properties of graphene. PMID:22917015

  6. Bacterial cellulose/acrylamide pH-sensitive smart hydrogel: development, characterization, and toxicity studies in ICR mice model.

    PubMed

    Pandey, Manisha; Mohamad, Najwa; Amin, Mohd Cairul Iqbal Mohd

    2014-10-01

    The objective of this study is to synthesize and evaluate acute toxicity of the bacterial cellulose (BC)/acrylamide (Am) hydrogels as noncytotoxic and biocompatible oral drug delivery vehicles. A novel series of solubilized BC/Am hydrogels were synthesized using a microwave irradiation method. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), swelling ratio, porosity, drug release, and in vitro and in vivo biocompatibility experiments. FTIR spectra revealed that the BC crystallinity and gel fraction decreased as the NaOH concentration increased from 2% to 10% w/v, whereas the optical transparency, pH sensitivity, and porosity were enhanced with increasing alkali concentration. Theophylline was used as a model drug for drug loading and release studies. The percentage of drug released was higher at pH 7.4 compared to pH 1.5. In vitro cytotoxicity and hemolytic tests indicated that the BC/Am hydrogel is noncytotoxic and hemocompatible. Results of acute oral toxicity tests on ICR mice suggested that the hydrogels are nontoxic up to 2000 mg/kg when administered orally, as no toxic response or histopathological changes were observed in comparison to control mice. The results of this study demonstrated that the pH-sensitive smart hydrogel makes it a possible safe carrier for oral drug delivery. PMID:25157890

  7. Preparation and characterization of irradiated carboxymethyl sago starch-acid hydrogel and its application as metal scavenger in aqueous solution.

    PubMed

    Basri, Sri Norleha; Zainuddin, Norhazlin; Hashim, Kamaruddin; Yusof, Nor Azah

    2016-03-15

    Carboxymethyl sago starch-acid hydrogel was prepared via irradiation technique to remove divalent metal ions (Pb, Cu and Cd) from their aqueous solution. The hydrogel was characterized by using Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The removal of these metal ions was analyzed by using inductively coupled plasma-optic emission spectra (ICP-OES) to study the amount of metal uptake by the hydrogel. Parameters of study include effect of pH, amount of sample, contact time, initial concentration of metal solution and reaction temperature. FTIR spectroscopy shows the CMSS hydrogel absorption peaks at 1741cm(-1), 1605cm(-1) and 1430cm(-1) which indicates the substitution of carboxymethyl group of modified sago starch. The degradation temperature of CMSS hydrogel is higher compared to CMSS due to the crosslinking by electron beam radiation and formed a porous hydrogel. From the data obtained, about 93.5%, 88.4% and 85.5% of Pb, Cu and Cd ions has been respectively removed from their solution under optimum condition. PMID:26794735

  8. Radiation synthesis of superabsorbent poly(acrylic acid)-carrageenan hydrogels

    NASA Astrophysics Data System (ADS)

    Francis, Sanju; Kumar, Manmohan; Varshney, Lalit

    2004-04-01

    A series of superabsorbent hydrogels were prepared from carrageenan and partially neutralized acrylic acid by gamma irradiation at room temperature. The gel fraction, swelling kinetics and the equilibrium degree of swelling (EDS) of the hydrogels were studied. It was found that the incorporation of even 1% carrageenan (sodium salt) increases the EDS of the hydrogels from ˜320 to ˜800 g/g. Thermal analysis were carried out to determine the amount of free water and bound water in the hydrogels. Under optimum conditions, poly(acrylic acid)-carrageenan hydrogels with high gel fraction (˜80%) and very high EDS (˜800 g/g) were prepared gamma radiolytically from aqueous solution containing 15% partially neutralized acrylic acid and 1-5% carrageenan. The hydrogels were also found to be sensitive to the pH and the ionic strength of the medium.

  9. Synthesis of PVA/PVP hydrogels having two-layer by radiation and their physical properties

    NASA Astrophysics Data System (ADS)

    Park, Kyoung Ran; Nho, Young Chang

    2003-06-01

    In these studies, two-layer hydrogels which consisted of polyurethane membrane and a mixture of polyvinyl alcohol(PVA)/poly- N-vinylpyrrolidone(PVP)/glycerin/chitosan were made for the wound dressing. Polyurethane was dissolved in solvent, the polyurethane solution was poured on the mould, and then dried to make the thin membrane. Hydrophilic polymer solutions were poured on the polyurethane membranes, they were exposed to gamma irradiation or two steps of 'freezing and thawing' and gamma irradiation doses to make the hydrogels. The physical properties such as gelation, water absorptivity, and gel strength were examined to evaluate the hydrogels for wound dressing. The physical properties of hydrogels such as gelation and gel strength was greatly improved when polyurethane membrane was used as a covering layer of hydrogel, and the evaporation speed of water in hydrogel was reduced.

  10. Synthesis of chemical cross-linked gelatin hydrogel reinforced with cellulose nanocrystals (CNC)

    NASA Astrophysics Data System (ADS)

    Yin, Ooi Shok; Ahmad, Ishak; Amin, Mohd. Cairul Iqbal Mohd

    2014-09-01

    A novel method was performed to obtain hydrogel with superior sensitivity towards changes in pH and temperature by incorporation of CNC into gelatin based hydrogel. Glutaraldehyde was used as cross-linker due to its high chemical reactivity towards NH2 group on gelatin. Different ratio of gelatin / CNC hydrogel was produced in order to study the effects of CNC towards the swelling behaviour of hydrogel at different pH and temperature. Swelling tests were performed at different pH range from pH 3 to pH 11. Temperature swelling tests were performed at 25 °C and 37 °C. The hydrogel showed impressive pH sensitivity and maximum swelling was obtained at pH 3. Higher swelling ratio was observed at higher temperature. SEM micrographs showed that the pore size of hydrogel decreased with increasing CNC content due to formation of more rigid hydrogel structure. The characteristics of the hydrogel to respond to different pH and temperature suggest that gelatin / CNC hydrogel are promising candidates to be developed as drug carrier.

  11. 3D chemical characterization of frozen hydrated hydrogels using ToF-SIMS with argon cluster sputter depth profiling.

    PubMed

    Taylor, Michael; Scurr, David; Lutolf, Matthias; Buttery, Lee; Zelzer, Mischa; Alexander, Morgan

    2016-06-01

    Hydrogels have been used extensively in bioengineering as artificial cell culture supports. Investigation of the interrelationship between cellular response to the hydrogel and its chemistry ideally requires methods that allow characterization without labels and can map species in three-dimensional to follow biomolecules adsorbed to, and absorbed into, the open structure before and during culture. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has the potential to be utilized for through thickness characterization of hydrogels. The authors have established a simple sample preparation procedure to successfully achieve analysis of frozen hydrated hydrogels using ToF-SIMS without the need for dry glove box entry equipment. They demonstrate this on a poly(2-hydroxyethyl methacrylate) (pHEMA) film where a model protein (lysozyme) is incorporated using two methods to demonstrate how protein distribution can be determined. A comparison of lysozyme incorporation is made between the situation where the protein is present in a polymer dip coating solution and where lysozyme is in an aqueous medium in which the film is incubated. It is shown that protonated water clusters H(H2O)n (+) where n = 5-11 that are indicative of ice are detected through the entire thickness of the pHEMA. The lysozyme distribution through the pHEMA hydrogel films can be determined using the intensity of a characteristic amino acid secondary ion fragment. PMID:26253107

  12. Chitosan hydrogels for chondroitin sulphate controlled release: an analytical characterization.

    PubMed

    Bianchera, Annalisa; Salomi, Enrico; Pezzanera, Matteo; Ruwet, Elisabeth; Bettini, Ruggero; Elviri, Lisa

    2014-01-01

    This paper provides an analytical characterization of chitosan scaffolds obtained by freeze-gelation toward the uptake and the controlled release of chondroitin sulphate (CS), as cartilage repair agent, under different pH conditions. Scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and liquid chromatography-UV spectrophotometry (LC-UV) techniques were exploited to obtain qualitative and quantitative descriptions of polymer and drug behaviour in the biomaterial. As for morphology, SEM analysis allowed the evaluation of scaffold porosity in terms of pore size and distribution both at the surface (Feret diameter 58 ± 19 μm) and on the cross section (Feret diameter 106 ± 51 μm). LC and ATR-FTIR evidenced a pH-dependent CS loading and release behaviour, strongly highlighting the role of electrostatic forces on chitosan/chondroitin sulphate interactions. PMID:25614850

  13. Chitosan Hydrogels for Chondroitin Sulphate Controlled Release: An Analytical Characterization

    PubMed Central

    Bianchera, Annalisa; Salomi, Enrico; Pezzanera, Matteo; Ruwet, Elisabeth; Bettini, Ruggero; Elviri, Lisa

    2014-01-01

    This paper provides an analytical characterization of chitosan scaffolds obtained by freeze-gelation toward the uptake and the controlled release of chondroitin sulphate (CS), as cartilage repair agent, under different pH conditions. Scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and liquid chromatography-UV spectrophotometry (LC-UV) techniques were exploited to obtain qualitative and quantitative descriptions of polymer and drug behaviour in the biomaterial. As for morphology, SEM analysis allowed the evaluation of scaffold porosity in terms of pore size and distribution both at the surface (Feret diameter 58 ± 19 μm) and on the cross section (Feret diameter 106 ± 51 μm). LC and ATR-FTIR evidenced a pH-dependent CS loading and release behaviour, strongly highlighting the role of electrostatic forces on chitosan/chondroitin sulphate interactions. PMID:25614850

  14. Light-guiding hydrogels for cell-based sensing and optogenetic synthesis in vivo

    NASA Astrophysics Data System (ADS)

    Choi, Myunghwan; Choi, Jin Woo; Kim, Seonghoon; Nizamoglu, Sedat; Hahn, Sei Kwang; Yun, Seok Hyun

    2013-12-01

    Polymer hydrogels are widely used as cell scaffolds for biomedical applications. Although the biochemical and biophysical properties of hydrogels have been investigated extensively, little attention has been paid to their potential photonic functionalities. Here, we report cell-integrated polyethylene glycol-based hydrogels for in vivo optical-sensing and therapy applications. Hydrogel patches containing cells were implanted in awake, freely moving mice for several days and shown to offer long-term transparency, biocompatibility, cell viability and light-guiding properties (loss of <1 dB cm-1). Using optogenetic, glucagon-like peptide-1 secreting cells, we conducted light-controlled therapy using the hydrogel in a mouse model with diabetes and obtained improved glucose homeostasis. Furthermore, real-time optical readout of encapsulated heat-shock-protein-coupled fluorescent reporter cells made it possible to measure the nanotoxicity of cadmium-based bare and shelled quantum dots (CdTe; CdSe/ZnS) in vivo.

  15. Characterization of gliclazide release from Isabgol husk hydrogel beads by validated HPLC method.

    PubMed

    Sharma, Vipin K; Mazumdar, B

    2014-01-01

    Isabgol husk, a medicinally important natural polysaccharide was applied for fabrication of hydrogel beads by ionic gelation method to incorporate gliclazide. Different strengths of Isabgol husk and sodium alginate were utilized for assessing the process variables on formulation performance. Aqueous solution of calcium chloride in 2, 5 and 8% w/v strength was used as cross-linker for polymeric blends of Isabgol husk and sodium alginate. The formulations were characterized for various parameters such as particle size, swelling index, entrapment efficiency, in vitro release, and release kinetics. The quantification of gliclazide throughout the study was performed by HPLC method which was validated according to ICH guidelines for system suitability, linearity, accuracy, sensitivity, precession, robustness, and ruggedness. The surface morphology of beads was observed by scanning electron microscopy. The formed beads were brown, free flowing, spherical, and irregular in structure. The size in different formulations varied from 752.83 +/- 0.630 to 838.62 +/- 0.741 microm. The beads remained for 2-3 h in alkaline phosphate buffer (pH 7.4), after that they showed disintegration. The formulations released up to 95% of loaded gliclazide in phosphate buffer (pH 7.4) within 8 h. No significant difference was observed in parameters studied such as particle size, entrapment efficiency and swelling index for hydrogel beads during accelerated stability study (p > 0.05). The regression equation developed by HPLC method was linear (r5 > 0.9990) over the range 2.5 to 10 microg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were 0.037619 microg/mL and 0.113997 microg/mL, respectively. The observed values for number of theoretical plates (N > or = 2000), tailing factor (T < or = 2), asymmetry factor (AF < or = 1), and relative standard deviation (RSD < or = 1%) of applied method showed the reliability for gliclazide estimation in Isabgol husk hydrogel beads. PMID

  16. Synthesis and Properties of pH-, Thermo-, and Salt-Sensitive Modified Poly(aspartic acid)/Poly(vinyl alcohol) IPN Hydrogel and Its Drug Controlled Release.

    PubMed

    Lu, Jingqiong; Li, Yinhui; Hu, Deng; Chen, Xiaoling; Liu, Yongmei; Wang, Liping; Zhao, Yansheng

    2015-01-01

    Modified poly(aspartic acid)/poly(vinyl alcohol) interpenetrating polymer network (KPAsp/PVA IPN) hydrogel for drug controlled release was synthesized by a simple one-step method in aqueous system using poly(aspartic acid) grafting 3-aminopropyltriethoxysilane (KH-550) and poly(vinyl alcohol) (PVA) as materials. The hydrogel surface morphology and composition were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The thermal stability was analyzed by thermogravimetric analysis (TGA). The swelling properties and pH, temperature, and salt sensitivities of KPAsp, KPAsp/PVA semi-interpenetrating polymer network (semi-IPN), and KPAsp/PVA IPN hydrogels were also investigated. All of the three hydrogels showed ampholytic pH-responsive properties, and swelling behavior was also extremely sensitive to the temperature, ionic strength, and cationic species. Finally, the drug controlled release properties of the three hydrogels were evaluated and results indicated that three hydrogels could control drug release by external surroundings stimuli. The drug controlled release properties of KPAsp/PVA IPN hydrogel are the most outstanding, and the correlative measured release profiles of salicylic acid at 37°C were 32.6 wt% at pH = 1.2 (simulated gastric fluid) and 62.5 wt% at pH = 7.4 (simulated intestinal fluid), respectively. These results indicated that KPAsp/PVA IPN hydrogels are a promising carrier system for controlled drug delivery. PMID:26351630

  17. Synthesis and Properties of pH-, Thermo-, and Salt-Sensitive Modified Poly(aspartic acid)/Poly(vinyl alcohol) IPN Hydrogel and Its Drug Controlled Release

    PubMed Central

    Lu, Jingqiong; Li, Yinhui; Hu, Deng; Chen, Xiaoling; Liu, Yongmei; Wang, Liping; Zhao, Yansheng

    2015-01-01

    Modified poly(aspartic acid)/poly(vinyl alcohol) interpenetrating polymer network (KPAsp/PVA IPN) hydrogel for drug controlled release was synthesized by a simple one-step method in aqueous system using poly(aspartic acid) grafting 3-aminopropyltriethoxysilane (KH-550) and poly(vinyl alcohol) (PVA) as materials. The hydrogel surface morphology and composition were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The thermal stability was analyzed by thermogravimetric analysis (TGA). The swelling properties and pH, temperature, and salt sensitivities of KPAsp, KPAsp/PVA semi-interpenetrating polymer network (semi-IPN), and KPAsp/PVA IPN hydrogels were also investigated. All of the three hydrogels showed ampholytic pH-responsive properties, and swelling behavior was also extremely sensitive to the temperature, ionic strength, and cationic species. Finally, the drug controlled release properties of the three hydrogels were evaluated and results indicated that three hydrogels could control drug release by external surroundings stimuli. The drug controlled release properties of KPAsp/PVA IPN hydrogel are the most outstanding, and the correlative measured release profiles of salicylic acid at 37°C were 32.6 wt% at pH = 1.2 (simulated gastric fluid) and 62.5 wt% at pH = 7.4 (simulated intestinal fluid), respectively. These results indicated that KPAsp/PVA IPN hydrogels are a promising carrier system for controlled drug delivery. PMID:26351630

  18. Supramolecular Hydrogels Made of the Basic Biological Building Blocks

    PubMed Central

    Du, Xuewen; Zhou, Jie; Xu, Bing

    2014-01-01

    As a consequence of the self-assembly of small organic molecules in water, supramolecular hydrogels are evolving from serendipitous events during organic synthesis to become a new type of materials that promise increased applications in biomedicine. In this focus review, we describe the recent development on the use of basic biological building blocks for creating molecules that act as hydrogelators and the potential applications of the corresponding hydrogels. After introducing the concept of supramolecular hydrogels and defining the scope of this review, we briefly describe the methods for making and characterizing supramolecular hydrogels. Then, we discuss representative hydrogelators according to the categories of their building blocks, such as amino acids, nucleobases, and saccharides, and highlight the applications of the hydrogels when necessary. Finally, we offer our perspectives and outlooks on this fast-growing field at the interface of organic chemistry, materials, biology, and medicine. By providing a snapshot for chemists, engineers, and medical scientists, we hope that this focus review will contribute to the development of multidisciplinary research on supramolecular hydrogels for a wide range of applications in different fields. PMID:24623474

  19. Supramolecular hydrogels made of basic biological building blocks.

    PubMed

    Du, Xuewen; Zhou, Jie; Xu, Bing

    2014-06-01

    As a consequence of the self-assembly of small organic molecules in water, supramolecular hydrogels are evolving from serendipitous events during organic synthesis to become a new type of materials that hold promise for applications in biomedicine. In this Focus Review, we describe recent advances in the use of basic biological building blocks for creating molecules that act as hydrogelators and the potential applications of the corresponding hydrogels. After introducing the concept of supramolecular hydrogels and defining the scope of this review, we briefly describe the methods for making and characterizing supramolecular hydrogels. We then discuss representative hydrogelators according to the categories of their building blocks, such as amino acids, nucleobases, and saccharides, and highlight the applications of the hydrogels when necessary. Finally, we offer our perspective and outlook on this fast-growing field at the interface of organic chemistry, materials, biology, and medicine. By providing a snapshot for chemists, engineers, and medical scientists, we hope that this Focus Review will contribute to the development of multidisciplinary research on supramolecular hydrogels for a wide range of applications in different fields. PMID:24623474

  20. Design and synthesis of an amphiphilic graft hydrogel having a hydrophobic domain formed by multiple interactions.

    PubMed

    Nitta, Kyohei; Kimoto, Atsushi; Watanabe, Junji

    2016-11-01

    A novel hydrogel having hydrophobic oligo segments and hydrophilic poly(acrylamidoglycolic acid) (PAGA) as pH responsive polymer segments was designed and synthesized to be used as a soft biomaterial. Poly(trimethylene carbonate) (PTMC) as the side chain, for which the degrees of polymerization were 9, 19, and 49, and the composition ratios were 1, 5, and 10mol%, was used as the oligo segment in the hydrogel. The swelling ratio of the hydrogel was investigated under various changes in conditions such as pH, temperature, and hydrogen bonding upon urea addition. Under pH2-11 conditions, the graft gel reversibly swelled and shrank due to the effect of PAGA main chain. The interior morphology and skin layer of the hydrogel was observed by a scanning electron microscope. The hydrogel composed of PAGA as the hydrophilic polymer backbone had a sponge-like structure, with a pore size of approximately 100μm. On the other hand, upon increasing the ratio of trimethylene carbonate (TMC) units in the hydrogel, the pores became smaller or disappeared. Moreover, thickness of the skin layer significantly increased with the swelling ratio depended on the incorporation ratios of the PTMC macromonomer. Molecular incorporation in the hydrogel was evaluated using a dye as a model drug molecule. These features would play an important role in drug loading. Increasing the ratio of TMC units favored the adsorption of the dye and activation of the incorporation behavior. PMID:27523997

  1. Preparation and in vitro characterization of thermosensitive and mucoadhesive hydrogels for nasal delivery of phenylephrine hydrochloride.

    PubMed

    Xu, Xiaofeng; Shen, Yan; Wang, Wei; Sun, Chunmeng; Li, Chang; Xiong, Yerong; Tu, Jiasheng

    2014-11-01

    The aim of the present work was to develop a nasal delivery system of phenylephrine hydrochloride (PE) in spray form to make prolonged remedy of nasal congestion. The formulations contain the thermosensitive hydrogel, i.e., Poloxamer 407 (P407) and Poloxamer 188 (P188) mixtures, and mucoadhesives, i.e., ε-polylysine (ε-PL) and low molecular weight sodium hyaluronate (MW 11,000Da). The in vitro characterizations of formulations including rheology studies, texture profiles and in vitro mucoadhesion potential were investigated after gelation temperatures measurements. The results showed that the concentration of P407 or P188 had significant influence on gelation temperature and texture profiles. The addition of mucoadhesives, though lowered the gel strength of formulations, increased interaction with mucin. After screening, two formulations (i.e., 1.0% PE/0.5% ε-PL/17% P407/0.5% P188 or Formulation A; and 1.0% PE/0.5% HA/17% P407/0.8% P188 or Formulation B) presenting suitable gelation temperatures (∼32°C) were used for further studies on in vitro release behaviors and mucosa ciliotoxicity. Both formulations showed sustained release of PE for up to 8h and similar toxicity to saline, the negative control. Thus, the thermosensitive and mucoadhesive PE-containing hydrogels are promising to achieve prolonged decongestion in nasal cavity. PMID:25257714

  2. Nanocomposite hydrogels for biomedical applications

    PubMed Central

    Gaharwar, Akhilesh K.

    2014-01-01

    Hydrogels mimic native tissue microenvironment due to their porous and hydrated molecular structure. An emerging approach to reinforce polymeric hydrogels and to include multiple functionalities focuses on incorporating nanoparticles within the hydrogel network. A wide range of nanoparticles, such as carbon-based, polymeric, ceramic, and metallic nanomaterials can be integrated within the hydrogel networks to obtain nanocomposites with superior properties and tailored functionality. Nanocomposite hydrogels can be engineered to possess superior physical, chemical, electrical, and biological properties. This review focuses on the most recent developments in the field of nanocomposite hydrogels with emphasis on biomedical and pharmaceutical applications. In particular, we discuss synthesis and fabrication of nanocomposite hydrogels, examine their current limitations and conclude with future directions in designing more advanced nanocomposite hydrogels for biomedical and biotechnological applications. PMID:24264728

  3. Synthesis of stiffness-tunable and cell-responsive Gelatin-poly(ethylene glycol) hydrogel for three-dimensional cell encapsulation.

    PubMed

    Cao, Ye; Lee, Bae Hoon; Peled, Havazelet Bianco; Venkatraman, Subbu S

    2016-10-01

    Biosynthetic poly(ethylene glycol) (PEG)-based hydrogels have been extensively investigated as extracellular matrix (ECM) mimicking gels as they retain the benefits of both ECM (biological cues) and synthetic hydrogels (tunable mechanical properties). In this article, we developed and characterized a new gelatin-PEG (GP) hydrogel that retains the benefits of gelatin and synthetic hydrogels. In this strategy, the thiolation of gelatin was accomplished by reacting with Traut's reagent; the thiolated gelatin was then conjugated to one end of PEG diacrylate (PEGDA) by Michael-type addition reaction. Two kinds of GP precursors, GP30 and GP60, were synthesized by changing the amount of Traut's reagent, while the weight ratio between thiolated-gelatin and PEGDA of GP30 and GP60 was 1.451:1 and 0.785:1, respectively. Finally, neonatal human dermal fibroblasts were encapsulated into the hydrogel by cross-linking the remaining double bonds of precursor under ultraviolet light. These GP hydrogels can encapsulate the fibroblasts in situ with high cell viability. Moreover, the behaviors of cells within the GP hydrogels can be modulated by varying the cross-linking density of GP hydrogel (storage modulus from 40 to 2000 Pa). In particular, this article showed that a minimum amount of cell-binding motifs (gelatin >2.30 wt/vol % and 44.0% dry weight percentage) are required for attachment; and appropriate initial rheological and structural properties (storage modulus <∼100 Pa and mesh size >∼150 nm) can accelerate the attachment of cells and improve cell viability. Hence, this mixed-hydrogel platform allows an easily control hydrogel structure and modulates cell behavior to reconstruct new tissue in the three-dimensional microenvironments. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2401-2411, 2016. PMID:27170015

  4. Synthesis and flocculation properties of gum ghatti and poly(acrylamide-co-acrylonitrile) based biodegradable hydrogels.

    PubMed

    Mittal, Hemant; Jindal, Rajeev; Kaith, Balbir Singh; Maity, Arjun; Ray, Suprakas Sinha

    2014-12-19

    This article reports the development of biodegradable flocculants based on graft co-polymers of gum ghatti (Gg) and a mixture of acrylamide and acrylonitrile co-monomers (AAm-co-AN). The hydrogel polymer exhibited an excellent swelling capacity of 921% in neutral medium at 60°C. The polymer was used to remove saline water from various petroleum fraction-saline water emulsions. The flocculation characteristics of the hydrogel polymer were studied in turbid kaolin solution as a function of the amount of polymer and the solution temperature and pH. Biodegradation studies of hydrogel polymer were conducted using the soil composting method, and the degradation process was constantly monitored using scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The results demonstrated an 89.47% degradation of the polymer after 60 days. Finally, the hydrogel polymer adsorbed 98% of cationic dyes from the aqueous solutions. PMID:25263897

  5. In Situ Synthesis of Magnetic Field-Responsive Hemicellulose Hydrogels for Drug Delivery

    PubMed Central

    2015-01-01

    A one-pot synthetic methodology for fabricating stimuli-responsive hemicellulose-based hydrogels was developed that consists of the in situ formation of magnetic iron oxide (Fe3O4) nanoparticles during the covalent cross-linking of O-acetyl-galactoglucomannan (AcGGM). The Fe3O4 nanoparticle content controlled the thermal stability, macrostructure, swelling behavior, and magnetization of the hybrid hydrogels. In addition, the magnetic field-responsive hemicellulose hydrogels (MFRHHs) exhibited excellent adsorption and controlled release profiles with bovine serum albumin (BSA) as the model drug. Therefore, the MFRHHs have great potential to be utilized in the biomedical field for tissue engineering applications, controlled drug delivery, and magnetically assisted bioseparation. Magnetic field-responsive hemicellulose hydrogels, prepared using a straightforward one-step process, expand the applications of biomass-derived polysaccharides by combining the renewability of hemicellulose and the magnetism of Fe3O4 nanoparticles. PMID:26196600

  6. Synthesis of CarAlg/MMt nanocomposite hydrogels and adsorption of cationic crystal violet.

    PubMed

    Mahdavinia, Gholam Reza; Aghaie, Huriyeh; Sheykhloie, Hossein; Vardini, Mohammad Taghi; Etemadi, Hossein

    2013-10-15

    CarAlg/MMt nanocomposite hydrogels composed of kappa-carrageenan (Car) and sodium alginate (Alg) biopolymers were synthesized by incorporation of sodium montmorillonite (Na-MMt) nanoclay. Acrylamide (AAm), methylenebisacrylamide (MBA), and ammonium persulfate (APS) were used as monomer, crosslinker, and initiator, respectively. The structure and morphology of nanocomposites were characterized by XRD, SEM, and TEM techniques. The XRD results showed exfoliated MMt nanoclay and exfoliation of MMt was confirmed by TEM graph. The resulting nanocomposites were evaluated to remove cationic crystal violet (CV) dye from water. According to data, the adsorption capacity of nanocomposites was enhanced as the clay content was increased. The experimental data were analyzed according to both Langmuir and Freundlich models and experimental maximum adsorption capacity was obtained 88.8 mg g(-1). By studying the effect of pH on the dye adsorption capacity of nanocomposites, it was revealed that the adsorption capacity of nanocomposites was enhanced at acidic pHs as the Na-MMt nanoclay and kappa-carrageenan components were increased. PMID:23987355

  7. Synthesis, properties, and biomedical applications of gelatin methacryloyl (GelMA) hydrogels.

    PubMed

    Yue, Kan; Trujillo-de Santiago, Grissel; Alvarez, Mario Moisés; Tamayol, Ali; Annabi, Nasim; Khademhosseini, Ali

    2015-12-01

    Gelatin methacryloyl (GelMA) hydrogels have been widely used for various biomedical applications due to their suitable biological properties and tunable physical characteristics. GelMA hydrogels closely resemble some essential properties of native extracellular matrix (ECM) due to the presence of cell-attaching and matrix metalloproteinase responsive peptide motifs, which allow cells to proliferate and spread in GelMA-based scaffolds. GelMA is also versatile from a processing perspective. It crosslinks when exposed to light irradiation to form hydrogels with tunable mechanical properties. It can also be microfabricated using different methodologies including micromolding, photomasking, bioprinting, self-assembly, and microfluidic techniques to generate constructs with controlled architectures. Hybrid hydrogel systems can also be formed by mixing GelMA with nanoparticles such as carbon nanotubes and graphene oxide, and other polymers to form networks with desired combined properties and characteristics for specific biological applications. Recent research has demonstrated the proficiency of GelMA-based hydrogels in a wide range of tissue engineering applications including engineering of bone, cartilage, cardiac, and vascular tissues, among others. Other applications of GelMA hydrogels, besides tissue engineering, include fundamental cell research, cell signaling, drug and gene delivery, and bio-sensing. PMID:26414409

  8. Development, characterization, and applications of self-assembling, photocrosslinkable collagen-based hydrogels

    NASA Astrophysics Data System (ADS)

    Gaudet, Ian Daniel

    Development of functional soft-tissue engineered constructs for use in regenerative medicine is currently limited by homogeneity within scaffolds that fails to recapitulate the complex architecture that supports normal function in healthy tissues. Additionally, recent breakthroughs in our understanding the biomechanical cell-matrix interface have provided insight into the role of substrate compliance during development and in the pathophysiological environment. This thesis is the result of investigation into using type-I collagen as a base material for creating dynamic, self-assembling, mechanically and biochemically tunable 3D hydrogel scaffolds into which instructive cellular cues can be imparted anisotropically via the directed application of light. This overarching goal was approached by (1) evaluating extant methods for photonically manipulating type I collagen mechanical properties, which led us to the conclusion that published methods were inadequate for our purposes. Following this realization, we (2) developed a novel process for derivatizing free amines on collagen amino acid residues to reactive methacrylamide moieties, allowing robust spatiotemporal control of mechanical properties through photocrosslinking with long-wave UV light and the water-soluble photoinitiator Irgacure 2959. Thorough characterization of this material, collagen methacrylamide (CMA), provided the basis for multiple applications in the field of soft tissue engineering. Additionally, (3) CMA was used in conjunction with synthetic photopolymers in an effort to create a hybrid natural/synthetic hydrogel material. CMA was also (4) employed as a dynamic hydrogel scaffold which we showed could be used to culture a number of neurogenic stem and progenitor cell types with a focus on using photomodulation to impart instructive heterogeneity to the mechanical and biochemical microenvironment. Finally, (5) we used a computational modeling approach to explain interesting yet poorly understood

  9. Characterization of the crosslinking kinetics of multi-arm poly(ethylene glycol) hydrogels formed via Michael-type addition.

    PubMed

    Kim, Jiwon; Kong, Yen P; Niedzielski, Steven M; Singh, Rahul K; Putnam, Andrew J; Shikanov, Ariella

    2016-02-21

    Tunable properties of multi-arm poly(ethylene glycol) (PEG) hydrogel, crosslinked by Michael-type addition, support diverse applications in tissue engineering. Bioactive modification of PEG is achieved by incorporating integrin binding sequences, like RGD, and crosslinking with tri-functional protease sensitive crosslinking peptide (GCYKNRGCYKNRCG), which compete for the same reactive groups in PEG. This competition leads to a narrow range of conditions that support sufficient crosslinking density to provide structural control. Kinetics of hydrogel formation plays an important role in defining the conditions to form hydrogels with desired mechanical and biological properties, which have not been fully characterized. In this study, we explored how increasing PEG functionality from 4 to 8-arms and the concentration of biological moieties, ranging from 0.5 mM to 3.75 mM, affected the kinetics of hydrogel formation, storage modulus, and swelling after the hydrogels were allowed to form for 15 or 60 minutes. Next, human bone marrow stromal cells were encapsulated and cultured in these modified hydrogels to investigate the combined effect of mechano-biological properties on phenotypes of encapsulated cells. While the molar concentration of the reactive functional groups (-vinyl sulfone) was identical in the conditions comparing 4 and 8-arm PEG, the 8-arm PEG formed faster, allowed a greater degree of modification, and was superior in three-dimensional culture. The degrees of swelling and storage modulus of 8-arm PEG were less affected by the modification compared to 4-arm PEG. These findings suggest that 8-arm PEG allows a more precise control of mechanical properties that could lead to a larger spectrum of tissue engineering applications. PMID:26750719

  10. A novel smart injectable hydrogel prepared by microbial transglutaminase and human-like collagen: Its characterization and biocompatibility.

    PubMed

    Zhao, Leilei; Li, Xian; Zhao, Jiaqi; Ma, Saijian; Ma, Xiaoxuan; Fan, Daidi; Zhu, Chenhui; Liu, Yannan

    2016-11-01

    Various tissue scaffold materials are increasingly used to repair skin defects by cross-linking because of the ability to fill and implant in any form via operation. However, crosslinker residues cannot be easily removed from scaffold materials prepared by chemical crosslinking methods, limiting their use for skin tissue engineering. Here, microbial transglutaminase (MTGase), a nontoxic crosslinker with high specific activity and reaction rate under mild conditions, was employed crosslinks in human-like collagen (HLC) to yield novel smart MTGase crosslinked with human-like collagen (MTGH) hydrogels, which are sensitive to temperature and/or enzymes. Various ratios of MTGase/HLC were performed, and their physicochemical properties were characterized, including the swelling ratio, the elastic modulus, the morphology and the porosity. The degradation behavior and mechanism of MTGase in concentration-dependent manner involved in formation hydrogels were identifying in vitro. The cell attachment in vitro and biocompatibility in vivo were also investigated. The results demonstrated that the use of different concentrations of MTGase to crosslink HLC produced products with different degradation times and biocompatibilities. The 50U/g MTGase-prepared MTGH hydrogels had a higher density of crosslinks, which made them more resistant to degradation by collagenase I and collagenase II. However, 40U/g MTGase-prepared MTGH hydrogels were more suitable for cell attachment. In addition, compared with the Collagen Implant I® (SUM) used in animal experiments, the 40U/g MTGase-prepared MTGH hydrogels had a lower toxicity and better biocompatibility. Therefore, 40U/g MTGase crosslinked with HLC should be used to prepare MTGH hydrogels for potential application as soft materials for skin tissue engineering. PMID:27524026

  11. Encapsulation of liver microsomes into a thermosensitive hydrogel for characterization of drug metabolism and toxicity.

    PubMed

    Yang, Huiying; Zheng, Yuanting; Zhao, Bei; Shao, Tengfei; Shi, Qingling; Zhou, Ning; Cai, Weimin

    2013-12-01

    This study reported the encapsulation of liver microsomes into a thermosensitive hydrogel to characterize drug metabolism and predict drug effects. Pluronic(®)F-127 (F127) and acrylamide-bisacrylamide (Acr-Bis) were utilized as the two precursors. After chemical crosslinking catalyzed by ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED), the resulting Pluronic F127-acrylamide-bisacrylamide (FAB) hydrogel could encapsulate microsomes at 4 °C and facilitate metabolic reactions at 37 °C. The gel morphology at different Acr-Bis concentrations was characterized using field emission scanning electron microscopy (FE-SEM). Higher concentrations of Acr-Bis could lead to higher degrees of cross-linking of the gel. A fluorescent staining assay was subsequently used to demonstrate successful encapsulation of microsomes into the gel as well as the free diffusion process of micromolecular substrates. The thermosensitivity of the FAB gel was studied using swelling ratio and protein release assay to verify its ability to encapsulate microsomes. The metabolic activity of microsomes encapsulated in gels was investigated by detecting the metabolites of FDA-approved substrates, including dextromethorphan, chlorzoxazone and testosterone. Compared with the traditional method of microsomal incubation, the FAB gel maintained 60%-70% of microsome activity. Lastly, the classic anticancer prodrug cyclophosphamide (CTX) was chosen as a model drug for the study of drug metabolism and the prediction of drug effects. When the microsomes encapsulated in the FAB gel were used in the cell culture system, CTX induced a higher level of apoptosis in MCF-7 cells compared with traditional microsomes. PMID:24075480

  12. Visible-light-induced synthesis of pH-responsive composite hydrogels for controlled delivery of the anticonvulsant drug pregabalin.

    PubMed

    Cevik, Ozlem; Gidon, Dogan; Kizilel, Seda

    2015-01-01

    We report here a novel method for the synthesis of a pH-responsive composite using visible light. Formation of the pH-responsive layer is based on poly(methacrylic acid-g-ethylene glycol) as the macromer, eosin Y as the photoinitiator and triethanolamine as the co-initiator. The hydrogel was functionalized with hydrophobic domains through incorporation of crosslinked styrene-butadiene-styrene (SBS) copolymer into the pH-responsive prepolymer. Swelling ratios were decreased with the addition of SBS, and resulted in high hydrogel crosslink density. The composite allowed for controlled release of an anticonvulsant model drug, pregabalin, under neutral pH condition and the release was analyzed to describe the mode of transport through the network. In vitro human fibroblast survival assay and in vivo rabbit implantation experiments demonstrated that this hybrid network is not toxic and has desirable biocompatibility properties. This is the first report about the synthesis of a pH-responsive network incorporating crosslinked SBS synthesized under visible light. The approach for multifunctional membranes could allow the incorporation of molecules with specific functionalities so that sequential molecule delivery in response to specific stimuli could be achieved. PMID:25242648

  13. Photoinitiator-free synthesis of endothelial cell-adhesive and enzymatically degradable hydrogels.

    PubMed

    Jones, Derek R; Marchant, Roger E; von Recum, Horst; Sen Gupta, Anirban; Kottke-Marchant, Kandice

    2015-02-01

    We report on a photoinitiator-free synthetic method of incorporating bioactivity into poly(ethylene glycol) (PEG) hydrogels in order to control physical properties, enzymatic biodegradability and cell-specific adhesiveness of the polymer network, while eliminating the need for UV-mediated photopolymerization. To accomplish this, hydrogel networks were polymerized using Michael addition with four-arm PEG acrylate (10 kDa), using a collagenase-sensitive peptide (CSP) as a crosslinker, and introducing an endothelial cell-adhesive peptide either terminally (RGD) or attached to the crosslinking peptide sequence (CSP-RGD). The efficiency of the Michael addition reactions were determined by nuclear magnetic resonance and Ellman's assay. Successful decoupling of cell adhesivity and physical properties was demonstrated by quantifying and comparing the swelling ratios and Young's moduli of various hydrogel formulations. Degradation profiles were established by incubating functionalized hydrogels in collagenase solutions (0.0-1.0 μg ml(-1)), demonstrating that functionalized hydrogels degraded at a rate dependent upon collagenase concentration. Moreover, it was shown that the degradation rate was independent of CSP-RGD concentration. Cell attachment and proliferation on functionalized hydrogels were compared for various RGD concentrations, providing evidence that cell attachment and proliferation were directly related to relative amounts of the CSP-RGD combination peptide. An increase in cell viability was achieved using Michael addition techniques when compared to UV polymerization, and was assessed by a LIVE/DEAD fluorescence assay. This photoinitiator-free method shows promise in creating hydrogel-based tissue engineering scaffolds allow for decoupled cell adhesivity and physical properties and that render greater cell viability. PMID:25462848

  14. Gallium nitride nanostructures: Synthesis, characterization and applications

    NASA Astrophysics Data System (ADS)

    Kente, Thobeka; Mhlanga, Sabelo Dalton

    2016-06-01

    GaN nanostructures have been extensively studied due to their important properties and applications in many fields. The recent synthesis and uses of these nanostructures have been reviewed. The different synthesis methods such as catalyst-assisted and catalyst-free methods to make GaN nanostructures and different reaction conditions have been also reviewed. This review covers the synthesis, growth mechanism, crystalline structure, properties, applications, structural and optical characterization of GaN nanostructures.

  15. Hydrogel/bioactive glass composites for bone regeneration applications: synthesis and characterisation.

    PubMed

    Killion, John A; Kehoe, Sharon; Geever, Luke M; Devine, Declan M; Sheehan, Eoin; Boyd, Daniel; Higginbotham, Clement L

    2013-10-01

    Due to the deficiencies of current commercially available biological bone grafts, alternative bone graft substitutes have come to the forefront of tissue engineering in recent times. The main challenge for scientists in manufacturing bone graft substitutes is to obtain a scaffold that has sufficient mechanical strength and bioactive properties to promote formation of new tissue. The ability to synthesise hydrogel based composite scaffolds using photopolymerisation has been demonstrated in this study. The prepared hydrogel based composites were characterised using techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectrometry (EDX), rheological studies and compression testing. In addition, gel fraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), porosity and swelling studies of the composites were carried out. It was found that these novel hydrogel bioglass composite formulations did not display the inherent brittleness that is typically associated with bioactive glass based bone graft materials and exhibited enhanced biomechanical properties compared to the polyethylene glycol hydrogel scaffolds along. Together, the combination of enhanced mechanical properties and the deposition of apatite on the surface of these hydrogel based composites make them an ideal candidate as bone graft substitutes in cancellous bone defects or low load bearing applications. PMID:23910334

  16. Light-guiding hydrogels for cell-based sensing and optogenetic synthesis in vivo

    PubMed Central

    Choi, Myunghwan; Choi, Jin Woo; Kim, Seonghoon; Nizamoglu, Sedat; Hahn, Sei Kwang; Yun, Seok Hyun

    2013-01-01

    Polymer hydrogels are widely used as cell scaffolds for biomedical applications. While the biochemical and biophysical properties of hydrogels have been extensively investigated, little attention has been paid to their potential photonic functionalities. Here, we report cell-integrated polyethylene glycol-based hydrogels for in-vivo optical sensing and therapy applications. Hydrogel patches containing cells were implanted in awake, freely moving mice for several days and shown to offer long-term transparency, biocompatibility, cell-viability, and light-guiding properties (loss: <1 dB/cm). Using optogenetic, glucagon-like peptide-1 (GLP-1) secreting cells, we conducted light-controlled therapy using the hydrogel in a mouse model with type-2 diabetes and attained improved glucose homeostasis. Furthermore, real-time optical readout of encapsulated heat-shock-protein-coupled fluorescent reporter cells made it possible to measure the nanotoxicity of cadmium-based bare and shelled quantum dots (CdTe; CdSe/ZnS) in vivo. PMID:25346777

  17. Synthesis and Antimicrobial Activity of Some Novel Cross-Linked Chitosan Hydrogels

    PubMed Central

    Mohamed, Nadia Ahmed; Fahmy, Mona Mohamed

    2012-01-01

    Four novel hydrogels based on chitosan were synthesized via a cross-linking reaction of chitosan with different concentrations of oxalyl bis 4-(2,5-dioxo-2H-pyrrol- 1(5H)-yl)benzamide. Their structures were confirmed by fourier transform infrared X-ray (FTIR), scanning electron microscopy (SEM) and X-ray diffraction. The antimicrobial activities of the hydrogels against two crop-threatening pathogenic fungi namely: Aspergillus fumigatus (A. fumigatus, RCMBA 06002), and Aspergillus niger (A. niger, RCMBA 06106), and five bacterial species namely: Bacillis subtilis (B. subtilis, RCMBA 6005), Staphylococcus aureus (S. aureus, RCMBA 2004), Streptococcus pneumoniae (S. pneumonia, RCMB 000101) as Gram positive bacteria, and Salmonella typhimurium (S. typhimurium, RCMB 000104), and Escherichia coli (E. coli, RCMBA 5003) as Gram negative bacteria have been investigated. The prepared hydrogels showed much higher antimicrobial activities than that of the parent chitosan. The hydrogels were more potent in case of Gram-positive bacteria than Gram-negative bacteria. Increasing the degree of cross-linking in the hydrogels resulted in a weaker antimicrobial activity. PMID:23109847

  18. Property-based design: optimization and characterization of polyvinyl alcohol (PVA) hydrogel and PVA-matrix composite for artificial cornea.

    PubMed

    Jiang, Hong; Zuo, Yi; Zhang, Li; Li, Jidong; Zhang, Aiming; Li, Yubao; Yang, Xiaochao

    2014-03-01

    Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt. PMID:24464723

  19. Design and Characterization of a Synthetically Accessible, Photodegradable Hydrogel for User-Directed Formation of Neural Networks

    PubMed Central

    McKinnon, Daniel D.; Brown, Tobin E.; Kyburz, Kyle A.; Kiyotake, Emi; Anseth, Kristi S.

    2015-01-01

    Hydrogels with photocleavable units incorporated into the cross-links have provided researchers with the ability to control mechanical properties temporally and study the role of matrix signaling on stem cell function and fate. With a growing interest in dynamically tunable cell culture systems, methods to synthesize photolabile hydrogels from simple precursors would facilitate broader accessibility. Here, a step-growth photodegradable poly(ethylene glycol) (PEG) hydrogel system cross-linked through a strain promoted alkyne–azide cycloaddition (SPAAC) reaction and degraded through the cleavage of a nitrobenzyl ether moiety integrated into the cross-links is developed from commercially available precursors in three straightforward synthetic steps with high yields (>95%). The network evolution and degradation properties are characterized in response to one- and two-photon irradiation. The PEG hydrogel is employed to encapsulate embryonic stem cell-derived motor neurons (ESMNs), and in situ degradation is exploited to gain three-dimensional control over the extension of motor axons using two-photon infrared light. Finally, ESMNs and their in vivo synaptic partners, myotubes, are coencapsulated, and the formation of user-directed neural networks is demonstrated. PMID:24932668

  20. Preparation and characterization of novel P(HEA/IA) hydrogels for Cd2+ ion removal from aqueous solution

    NASA Astrophysics Data System (ADS)

    Antić, Katarina M.; Babić, Marija M.; Vuković, Jovana J. Jovašević; Vasiljević-Radović, Dana G.; Onjia, Antonije E.; Filipović, Jovanka M.; Tomić, Simonida Lj.

    2015-05-01

    Series of novel hydrogels based on 2-hydroxyethyl acrylate (HEA) and itaconic acid (IA), P(HEA/IA) copolymers, were prepared by free radical cross-linking copolymerization and investigated as potential adsorbents for Cd2+ removal from aqueous solution. The hydrogels before and after Cd2+ adsorption were characterized using FTIR, DSC, SEM/EDX, AFM and DMA analysis. The swelling results showed that these hydrogels are pH and temperature sensitive. In order to evaluate adsorption behavior of samples various factors affecting the Cd2+ uptake behavior, such as: contact time, temperature, pH, ionic strength, adsorbent weight, competitive ions and initial concentration of the metal ions were investigated. Five adsorption isotherms and two kinetic models were studied. The adsorption behavior can be very well described by the pseudo-second order kinetic model and Langmuir isotherm. Multicomponent adsorption studies revealed that adsorption of cadmium depends on the type of metal ions present in the system. Desorption studies showed that hydrogel can be reused three times with only 15% loss of adsorption capacity. All results indicate that the sample with the highest IA content is the most promising adsorbent for Cd2+ removal.

  1. Tragacanth gum/nano silver hydrogel on cotton fabric: In-situ synthesis and antibacterial properties.

    PubMed

    Montazer, M; Keshvari, A; Kahali, P

    2016-12-10

    This paper is mainly focused on introducing cotton fabric with hydrogel and antimicrobial properties using Tragacanth gum as a natural polymer with hydrogel properties, silver nitrate as silver precursor, citric acid as a cross-linking agent and sodium hypophosphite as catalyst. The water absorption behavior of the treated fabrics was investigated with moisture regain, water retention, drying time of wetted fabric at room condition and vertical wicking tests. Antibacterial properties of the samples were evaluated against Escherichia coli and Staphylococcous aureus. The SEM pictures confirmed formation of nano silver and hydrogel layer on the fabric surface and XRD performed the crystal and particle size of the nano silver. The chemical structure of the fabric samples was identified with FTIR spectra. The central composite design (CCD) was used for statistical modelling, evaluated effective parameters and created optimum conditions. The treated cotton fabrics showed good water absorption properties along with reasonable antibacterial effectiveness. PMID:27577917

  2. Characterization and swelling-deswelling properties of wheat straw cellulose based semi-IPNs hydrogel.

    PubMed

    Liu, Jia; Li, Qian; Su, Yuan; Yue, Qinyan; Gao, Baoyu

    2014-07-17

    A novel wheat straw cellulose-g-poly(potassium acrylate)/polyvinyl alcohol (WSC-g-PKA/PVA) semi-interpenetrating polymer networks (semi-IPNs) hydrogel was prepared by polymerizing wheat straw and an aqueous solution of acrylic acid (AA), and further semi-interpenetrating with PVA occurred during the chemosynthesis. The swelling and deswelling properties of WSC-g-PKA/PVA semi-IPNs hydrogel and WSC-g-PKA hydrogel were studied and compared in various pH solutions, salt solutions, temperatures, particle sizes and ionic strength. The results indicated that both hydrogels had the largest swelling capacity at pH=6, and the effect of ions on the swelling of hydrogels was in the order: Na(+)>K(+)>Mg(2+)>Ca(2+). The Schott's pseudo second order model can be effectively used to evaluate swelling kinetics of hydrogels. Moreover, the semi-IPNs hydrogel had improved swelling-deswelling properties compared with that of WSC-g-PKA hydrogel. PMID:24702940

  3. Synthesis and swelling behavior of Protein-g-poly Methacrylic acid/kaolin superabsorbent hydrogel composites

    NASA Astrophysics Data System (ADS)

    Sadeghi, Mohammad

    2008-08-01

    A novel superabsorbent hydrogel composite based on Collagen have been prepared via graft copolymerization of Methacrylic acid (MAA) in the presence of kaolin powder using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The composite structure was confirmed using FTIR spectroscopy. A new absorption band at 1728 cm-1 in the composite spectrum confirmed kaolin-organic polymer linkage. The effect of kaolin amount and MBA concentration showed that with increasing of these parameters, the water absorbency of the superabsorbent composite was decreased. The swelling measurements of the hydrogels were conducted in aqueous salt solutions.

  4. Characterization of Network Structure of Polyacrylamide Based Hydrogels Prepared By Radiation Induced Polymerization

    SciTech Connect

    Mahmudi, Naim; Sen, Murat; Gueven, Olgun; Rendevski, Stojan

    2007-04-23

    In this study network structure of polyacrylamide based hydrogels prepared by radiation induced polymerization has been investigated. Polyacrylamide based hydrogels in the rod form were prepared by copolymerization of acrylamide(AAm) with hydroxyl ethyl methacrylate(HEMA) and methyl acrylamide(MAAm) in the presence of cross-linking agent and water by gamma rays at ambient temperature. Molecular weight between cross-links and effective cross-link density of hydrogels were calculated from swelling as well as shear modulus data obtained from compression tests. The results have shown that simple compression analyses can be used for the determination of effective cross-link density of hydrogels without any need to some polymer-solvent based parameters as in the case of swelling based determinations. Diffusion of water into hydrogels was examined by analyzing water absorption kinetics and the effect of network, structure on the diffusion type and coefficient was discussed.

  5. Silver Nanoparticle Coated Bioactive Glasses--Composites with Dex/CMC Hydrogels: Characterization, Solubility, and In Vitro Biological Studies.

    PubMed

    Wren, Anthony W; Hassanzadeh, Pegah; Placek, Lana M; Keenan, Timothy J; Coughlan, Aisling; Boutelle, Lydia R; Towler, Mark R

    2015-08-01

    Silver (Ag) coated bioactive glass particles (Ag-BG) were formulated and compared to uncoated controls (BG) in relation to glass characterization, solubility and microbiology. X-ray diffraction (XRD) confirmed a crystalline AgNP surface coating while ion release studies determined low Ag release (<2 mg/L). Cell culture studies presented increased cell viability (127 and 102%) with lower liquid extract (50 and 100 ml/ml) concentrations. Antibacterial testing of Ag-BG in E. coli, S. epidermidis and S. aureus significantly reduced bacterial cell viability by 60-90%. Composites of Ag-BG/CMC-Dex Hydrogels were formulated and characterized. Agar diffusion testing was conducted where Ag-BG/hydrogel composites produced the largest inhibition zones of 7 mm (E. coli), 5 mm (S. aureus) and 4 mm (S. epidermidis). PMID:25923463

  6. Facile synthesis of magnetic-/pH-responsive hydrogel beads based on Fe3O4 nanoparticles and chitosan hydrogel as MTX carriers for controlled drug release.

    PubMed

    Wu, Juan; Jiang, Wei; Tian, Renbing; Shen, Yewen; Jiang, Wei

    2016-10-01

    In the present study, methotrexate (MTX)-encapsulated magnetic-/pH-responsive hydrogel beads based on Fe3O4 nanoparticles and chitosan were successfully prepared through a one-step gelation process, which is a very facile, economic and environmentally friendly route. The developed hydrogel beads exhibited homogeneous porous structure and super-paramagnetic responsibility. MTX can be successfully encapsulated into magnetic chitosan hydrogel beads, and the drug encapsulation efficiency (%) and encapsulation content (%) were 93.8 and 6.28%, respectively. In addition, the drug release studies in vitro indicated that the MTX-encapsulated magnetic chitosan hydrogel beads had excellent pH-sensitivity, 90.6% MTX was released from the magnetic chitosan hydrogel beads within 48 h at pH 4.0. WST-1 assays in human liver hepatocellular carcinoma cells (HepG2) demonstrated that the MTX-encapsulated magnetic chitosan hydrogel beads had good cytocompatibility and high anti-tumor activity. Therefore, our results revealed that the MTX-encapsulated magnetic chitosan hydrogel beads would be a competitive candidate for controlled drug release in the area of targeted cancer therapy in the near future. PMID:27464586

  7. A cardiovascular occlusion method based on the use of a smart hydrogel.

    PubMed

    Jackson, Nathan; Verbrugghe, Peter; Cuypers, Dieter; Adesanya, Kenneth; Engel, Leeya; Glazer, Piotr; Dubruel, Peter; Shacham-Diamand, Yosi; Mendes, Eduardo; Herijgers, Paul; Stam, Frank

    2015-02-01

    Smart hydrogels for biomedical applications are highly researched materials. However, integrating them into a device for implantation is difficult. This paper investigates an integrated delivery device designed to deliver an electro-responsive hydrogel to a target location inside a blood vessel with the purpose of creating an occlusion. The paper describes the synthesis and characterization of a Pluronic/methacrylic acid sodium salt electro-responsive hydrogel. Application of an electrical bias decelerates the expansion of the hydrogel. An integrated delivery system was manufactured to deliver the hydrogel to the target location in the body. Ex vivo and in vivo experiments in the carotid artery of sheep were used to validate the concept. The hydrogel was able to completely occlude the blood vessel reducing the blood flow from 245 to 0 ml/min after implantation. Ex vivo experiments showed that the hydrogel was able to withstand physiological blood pressures of > 270 mm·Hg without dislodgement. The results showed that the electro-responsive hydrogel used in this paper can be used to create a long-term occlusion in a blood vessel without any apparent side effects. The delivery system developed is a promising device for the delivery of electro-responsive hydrogels. PMID:25203979

  8. Development and characterization of novel hydrogel containing antimicrobial drug for treatment of burns

    PubMed Central

    Thakkar, Vaishali; Korat, Vaishali; Baldaniya, Lalji; Gohel, Mukesh; Gandhi, Tejal; Patel, Nirav

    2016-01-01

    Introduction: The aim of burn management and therapy is fast healing and epithelisation to prevent infection. The present study is concerned with the development and characterization of a novel nanaoparticulate system; cubosomes, loaded with silver sulfadiazine (SSD) and Aloe vera for topical treatment of infected burns. Methods: Cubosome dispersions were formulated by an emulsification technique using different concentrations of a lipid phase Glyceryl Monooleate (GMO) and Poloxamer 407. The optimum formulae were incorporated in an aloe vera gel containing carbopol 934, to form cubosomal hydrogels (cubogels). The cubogels were characterized by in vitro release of SSD, rheological properties, pH, bioadhesion, Transmission Electron Microscopy and in-vivo Wound Healing Study. Results: The results show that the different concentration of GMO had significant effect on particle size, % EE and in vitro drug release. From the in-vitro drug release pattern and similarity factor (f2), it was concluded that batch CG3 (15% GMO and 1% P407) exhibited complete and controlled drug release within 12 hour (i.e. 98.25%), better bio adhesion and superior burn healing as compared to the marketed product. Conclusion: The in vivo burns healing study in rats revealed that the prepared optimized cubogel containing SSD and aloe vera has superior burns healing rate than cubogel with only SSD and marketed preparation so, it may be successfully used in the treatment of deep second degree burn. PMID:27606259

  9. Structural characterization and anti-cancerous potential of gallium bioactive glass/hydrogel composites.

    PubMed

    Keenan, T J; Placek, L M; Coughlan, A; Bowers, G M; Hall, M M; Wren, A W

    2016-11-20

    A bioactive glass series (0.42SiO2-0.10Na2O-0.08CaO-(0.40-X)ZnO-(X)Ga2O3) was incorporated into carboxymethyl cellulose (CMC)/dextran (Dex) hydrogels in three different amounts (0.05, 0.10, and 0.25m(2)), and the resulting composites were characterized using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and (13)C Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP MAS-NMR). Composite extracts were also evaluated in vitro against MG-63 osteosarcoma cells. TEM confirmed glass distribution throughout the composites, although some particle agglomeration was observed. DSC revealed that glass composition and content did have small effects on both Tg and Tm. MAS-NMR revealed that both CMC and Dex were successfully functionalized, that cross-linking occurred, and that glass addition did slightly alter bonding environments. Cell viability analysis suggested that extracts of the glass and composites with the largest Ga-content significantly decreased MG-63 osteosarcoma viability after 30days. This study successfully characterized this composite series, and demonstrated their potential for anti-cancerous applications. PMID:27561520

  10. Synthesis of a novel supermagnetic iron oxide nanocomposite hydrogel based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) onto salep for controlled release of drug.

    PubMed

    Bardajee, Ghasem Rezanejade; Hooshyar, Zari; Asli, Maryam Jahanbakhsh; Shahidi, Fatemeh Emamjome; Dianatnejad, Nastaran

    2014-03-01

    In this research, a novel supermagnetic iron oxide nanocomposite hydrogel was prepared using simultaneous in situ formation of iron oxide nanoparticles (IONs) and three-dimensional cross-linked polymer networks based on graft copolymerization of poly((2-dimethylamino)ethyl methacrylate) (PDMA) onto salep (PDMA-g-salep). The prepared ION-PDMA-g-salep hydrogel was systematically characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDAX), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). In addition, the ION-PDMA-g-salep hydrogel exhibits favorable swelling properties that are sensitive to temperature, pH, and external magnetic field (EMF). The drug release behavior of the prepared hydrogel under EMF, different temperatures and pHs was also studied for the evaluation of the release mechanism and determination of diffusion coefficients. Finally, the antibacterial activity and cytotoxicity studies of the prepared hydrogel were examined. These results suggested that the ION-PDMA-g-salep hydrogel could be a promising candidate for biological dressing applications. PMID:24433913

  11. Formulation and characterization of poloxamine-based hydrogels as tissue sealants.

    PubMed

    Cho, Eunhee; Lee, Jeoung Soo; Webb, Ken

    2012-07-01

    In situ cross linkable polyethylene glycol (PEG)-based polymers play an increasing role in surgical practice as sealants that provide a barrier to fluid/gas leakage and adhesion formation. This study investigated the gelation behavior and physical properties of hydrogels formed from homogeneous and blended solutions of two acrylated poloxamines (Tetronics® T1107 and T904) of various molecular weights and hydrophilic/lipophilic balances relative to a PEG control. Hydrogels were formed by reverse thermal gelation at physiological temperature (T1107-containing formulations) and covalent crosslinking by Michael-type addition with dithiothreitol. All poloxamine-based hydrogels exhibited thermosensitive behavior and achieved significantly reduced swelling, increased tensile properties and increased tissue bond strength relative to the PEG hydrogel at physiological temperature. Swelling and tensile properties of all poloxamine-based hydrogels were significantly greater at 37°C relative to 4°C, suggesting that their improved physical properties derive from cooperative crosslinking by both noncovalent and covalent mechanisms. Poloxamine-based hydrogels were cytocompatible and underwent hydrolytic degradation over 2-5weeks, depending on their T1107/T904 composition. In conclusion, select poloxamine-based hydrogels possess a number of properties potentially beneficial to tissue sealant applications, including a substantial increase in viscosity between room/physiological temperatures, resistance to cell adhesion and maintenance of a stable volume during equilibration. PMID:22406506

  12. Synthesis and swelling peculiarities of new hydrogels based on the macromolecular reaction of anhydride copolymers with γ-aminopropyltriethoxysilane.

    PubMed

    Timur, Mahir; Can, Hatice Kaplan

    2016-05-01

    This work describes the synthesis and macromolecular reactions of maleic anhydride (MA)-acrylamide (AAm) binary and MA-vinyl acetate (VA)- AAm ternary reactive copolymers with γ-aminopropyltriethoxysilane (APTS) as a polyfunctional crosslinker. Swelling parameters such as the start-time of the hydrogel-formation, initial rate of swelling, swelling rate constant, equilibrium swelling, and equilibrium water content (EWC) are determined for polymers/APTS/water systems with certain copolymer/crosslinker ratios (1.4/1 and 9/1). The formation of a hyperbranched network structure by the fragmentation of the side-chain reactive groups in the systems studied has also been confirmed by the Fourier Transform Infrared (FTIR) method. PMID:25761627

  13. Triethyl orthoformate mediated a novel crosslinking method for the preparation of hydrogels for tissue engineering applications: characterization and in vitro cytocompatibility analysis.

    PubMed

    Yar, Muhammad; Shahzad, Sohail; Siddiqi, Saadat Anwar; Mahmood, Nasir; Rauf, Abdul; Anwar, Muhammad Sabieh; Chaudhry, Aqif Anwar; Rehman, Ihtesham ur

    2015-11-01

    This paper describes the development of a new crosslinking method for the synthesis of novel hydrogel films from chitosan and PVA for potential use in various biomedical applications. These hydrogel membranes were synthesized by blending different ratios of chitosan (CS) and poly(vinyl alcohol) (PVA) solutions and were crosslinked with 2.5% (w/v) triethyl orthoformate (TEOF) in the presence of 17% (w/v) sulfuric acid. The physical/chemical interactions and the presence of specific functional groups in the synthesized materials were evaluated by Fourier transform infrared (FT-IR) spectroscopy. The morphology, structure and pore size of the materials were investigated by scanning electron microscopy (SEM). Thermal gravimetric analysis (TGA) proved that these crosslinked hydrogel films have good thermal stability which was decreased as the CS ratio was increased. Differential scanning calorimetry (DSC) exhibited that CS and PVA were present in the amorphous form. The solution absorption properties were performed in phosphate buffer saline (PBS) solution of pH7.4. The 20% PVA-80% CS crosslinked hydrogel films showed a greater degree of solution absorption (183%) as compared to other compositions. The hydrogels with greater CS concentration (60% and 80%) demonstrated relatively more porous structure, better cell viability and proliferation and also revealed good blood clotting ability even after crosslinking. Based on the observed facts these hydrogels can be tailored for their potential utilization in wound healing and skin tissue engineering applications. PMID:26249576

  14. 2-hydroxyethyl metahcrylate/gelatin based superporous hydrogels for tissue regeneration

    NASA Astrophysics Data System (ADS)

    Tomić, Simonida Lj.; Babić, Marija M.; Vuković, Jovana S.; Perišić, Marija D.; Filipović, Vuk V.; Davidović, Sladjana Z.; Filipović, Jovanka M.

    2016-05-01

    In this study, superporous hydrogels were synthesized by free radical polymerization of 2-hydroxyethyl methacrylate without and in the presence of gelatin. Highly porous hydrogel structures were obtained by two different techniques: using a gas blowing agent, sodium bicarbonate, and a cryogenic treatment followed by freeze-drying. After the gel synthesis, gelatin molecules were covalently immobilised onto PHEMA via glytaraldehyde activation. All samples were characterized for morphological, mechanical, swelling and antibacterial properties. The results obtained show that samples with gelatin show better properties in comparison with PHEMA samples, which make these materials highly attractive for developing hydrogel scaffolds for tissue regeneration.

  15. Fluxgate magnetorelaxometry for characterization of hydrogel polymerization kinetics and physical entrapment capacity.

    PubMed

    Heim, E; Harling, S; Ludwig, F; Menzel, H; Schilling, M

    2008-05-21

    Hydrogels have the potential for providing drug delivery systems with long release rates. The polymerization kinetics and the physical entrapment capacity of photo-cross-linked hydroxyethyl methacrylate hydroxyethylstarch hydrogels are investigated with a non-destructive method. For this purpose, superparamagnetic nanoparticles as replacements for biomolecules are used as probes. By analyzing their magnetic relaxation behavior, the amounts of physically entrapped and mobile nanoparticles can be determined. The hydrogels were loaded with five different concentrations of nanoparticles. Different methods of analysis of the relaxation curves and the influence of the microviscosity are discussed. This investigation allows one to optimize the UV light irradiation time and to determine the amount of physically entrapped nanoparticles in the hydrogel network. It was found that the polymerization kinetics is faster for decreasing nanoparticle concentration but not all nanoparticles can be physically entrapped in the network. PMID:21694236

  16. Mechanical properties and in vitro characterization of polyvinyl alcohol-nano-silver hydrogel wound dressings

    PubMed Central

    Oliveira, R. N.; Rouzé, R.; Quilty, B.; Alves, G. G.; Soares, G. D. A.; Thiré, R. M. S. M.; McGuinness, G. B.

    2014-01-01

    Polyvinyl alcohol (PVA) hydrogels are materials for potential use in burn healing. Silver nanoparticles can be synthesized within PVA hydrogels giving antimicrobial hydrogels. Hydrogels have to be swollen prior to their application, and the common medium available for that in hospitals is saline solution, but the hydrogel could also take up some of the wound's fluid. This work developed gamma-irradiated PVA/nano-Ag hydrogels for potential use in burn dressing applications. Silver nitrate (AgNO3) was used as nano-Ag precursor agent. Saline solution, phosphate-buffered solution (PBS) pH 7.4 and solution pH 4.0 were used as swelling media. Microstructural evaluation revealed an effect of the nanoparticles on PVA crystallization. The swelling of the PVA-Ag samples in solution pH 4.0 was low, as was their silver delivery, compared with the equivalent samples swollen in the other media. The highest swelling and silver delivery were related to samples prepared with 0.50% AgNO3, and they also presented lower strength in PBS pH 7.4 and solution pH 4.0. Both PVA-Ag samples were also non-toxic and presented antimicrobial activity, confirming that 0.25% AgNO3 concentration is sufficient to establish an antimicrobial effect. Both PVA-Ag samples presented suitable mechanical and swelling properties in all media, representative of potential burn site conditions. PMID:24501677

  17. Nanostructured Biomaterials with Controlled Properties Synthesis and Characterization

    PubMed Central

    2009-01-01

    Magnetic nanoparticles were obtained using an adjusted Massart method and were covered in a layer-by-layer technique with hydrogel-type biocompatible shells, from chitosan and hyaluronic acid. The synthesized nanocomposites were characterized using dynamic light scattering, transmission electron microscopy, and Fourier transformed infrared spectroscopy. Biocompatibility of magnetic nanostructures was determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) cell proliferation assay, swelling tests, and degradation tests. In addition, interaction of hydrogel-magnetic nanoparticles with microorganisms was studied. The possibility of precise nanoparticles size control, as long as the availability of bio-compatible covering, makes them suitable for biomedical applications. PMID:20596398

  18. Anisotropic polyvinyl alcohol hydrogel phantom for shear wave elastography in fibrous biological soft tissue: a multimodality characterization

    NASA Astrophysics Data System (ADS)

    Chatelin, Simon; Bernal, Miguel; Deffieux, Thomas; Papadacci, Clément; Flaud, Patrice; Nahas, Amir; Boccara, Claude; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2014-11-01

    Shear wave elastography imaging techniques provide quantitative measurement of soft tissues elastic properties. Tendons, muscles and cerebral tissues are composed of fibers, which induce a strong anisotropic effect on the mechanical behavior. Currently, these tissues cannot be accurately represented by existing elastography phantoms. Recently, a novel approach for orthotropic hydrogel mimicking soft tissues has been developed (Millon et al 2006 J. Biomed. Mater. Res. B 305-11). The mechanical anisotropy is induced in a polyvinyl alcohol (PVA) cryogel by stretching the physical crosslinks of the polymeric chains while undergoing freeze/thaw cycles. In the present study we propose an original multimodality imaging characterization of this new transverse isotropic (TI) PVA hydrogel. Multiple properties were investigated using a large variety of techniques at different scales compared with an isotropic PVA hydrogel undergoing similar imaging and rheology protocols. The anisotropic mechanical (dynamic and static) properties were studied using supersonic shear wave imaging technique, full-field optical coherence tomography (FFOCT) strain imaging and classical linear rheometry using dynamic mechanical analysis. The anisotropic optical and ultrasonic spatial coherence properties were measured by FFOCT volumetric imaging and backscatter tensor imaging, respectively. Correlation of mechanical and optical properties demonstrates the complementarity of these techniques for the study of anisotropy on a multi-scale range as well as the potential of this TI phantom as fibrous tissue-mimicking phantom for shear wave elastographic applications.

  19. Characterization of the chemotactic and mitogenic response of SMCs to PDGF-BB and FGF-2 in fibrin hydrogels

    PubMed Central

    Ucuzian, Areck A.; Brewster, Luke P.; East, Andrea T.; Pang, Yongang; Gassman, Andrew A.; Greisler, Howard P.

    2010-01-01

    The delivery of growth factors to cellularize biocompatible scaffolds like fibrin is a commonly used strategy in tissue engineering. We characterized SMC proliferation and chemotaxis in response to PDGF-BB and FGF-2, alone and in combination, in 2-D culture and in 3-D fibrin hydrogels. While both growth factors induced an equipotent mitogenic response in 2-D culture, only FGF-2 was significantly mitogenic for SMCs in 3-D culture. Only PDGF-BB was significantly chemotactic in a modified Boyden chamber assay. In a 3-D assay of matrix invasion, both growth factors induced an invasive response into the fibrin hydrogel in both proliferating and non-proliferating, mitomycin C (MMC) treated cells. The invasive response was less attenuated by the inhibition of proliferation in PDGF-BB stimulated cells compared with FGF-2 stimulated cells. We conclude that SMCs cultured in fibrin hydrogels have a more robust chemotactic response to PDGF-BB compared with FGF-2, and that the response to FGF-2 is more dependent on cell proliferation. Delivery of both growth factors together potentiates the chemotactic, but not mitogenic response to either growth factor alone. PMID:20730936

  20. Mechanical Characterization of a Dynamic and Tunable Methacrylated Hyaluronic Acid Hydrogel.

    PubMed

    Ondeck, Matthew G; Engler, Adam J

    2016-02-01

    Hyaluronic acid (HA) is a commonly used natural polymer for cell scaffolding. Modification by methacrylate allows it to be polymerized by free radicals via addition of an initiator, e.g., light-sensitive Irgacure, to form a methacrylated hyaluronic acid (MeHA) hydrogel. Light-activated crosslinking can be used to control the degree of polymerization, and sequential polymerization steps allow cells plated onto or in the hydrogel to initially feel a soft and then a stiff matrix. Here, the elastic modulus of MeHA hydrogels was systematically analyzed by atomic force microscopy (AFM) for a number of variables including duration of UV exposure, monomer concentration, and methacrylate functionalization. To determine how cells would respond to a specific two-step polymerization, NIH 3T3 fibroblasts were cultured on the stiffening MeHA hydrogels and found to reorganize their cytoskeleton and spread area upon hydrogel stiffening, consistent with cells originally cultured on substrates of the final elastic modulus. PMID:26746491

  1. Catalyzed ester synthesis using Candida rugosa lipase entrapped by poly(N-isopropylacrylamide-co-itaconic acid) hydrogel.

    PubMed

    Milašinović, Nikola; Jakovetić, Sonja; Knežević-Jugović, Zorica; Milosavljević, Nedeljko; Lučić, Marija; Filipović, Jovanka; Kalagasidis Krušić, Melina

    2014-01-01

    This study reports the synthesis of polymeric matrices based on N-isopropylacrylamide and itaconic acid and its application for immobilization of lipase from Candida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45 °C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic activity in an aqueous medium and esterolytic activity in an organic medium have been evaluated. Maximum reaction rate (V max) and Michaelis-Menten constants (K m ) were also determined for immobilized lipase. Storage stability of lipase was increased as a result of immobilization process. Furthermore, the operational stability and reusability of the immobilized lipase in esterification reaction have been studied, and it was observed that after 10 cycles, the residual activity for entrapped lipase was as high as 50%, implying that the developed hydrogel and immobilized system could provide a promising solution for the flavor ester synthesis at the industrial scale. PMID:24701136

  2. Catalyzed Ester Synthesis Using Candida rugosa Lipase Entrapped by Poly(N-isopropylacrylamide-co-itaconic Acid) Hydrogel

    PubMed Central

    Milašinović, Nikola; Jakovetić, Sonja; Knežević-Jugović, Zorica; Milosavljević, Nedeljko; Lučić, Marija; Filipović, Jovanka; Kalagasidis Krušić, Melina

    2014-01-01

    This study reports the synthesis of polymeric matrices based on N-isopropylacrylamide and itaconic acid and its application for immobilization of lipase from Candida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45°C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic activity in an aqueous medium and esterolytic activity in an organic medium have been evaluated. Maximum reaction rate (Vmax) and Michaelis-Menten constants (Km) were also determined for immobilized lipase. Storage stability of lipase was increased as a result of immobilization process. Furthermore, the operational stability and reusability of the immobilized lipase in esterification reaction have been studied, and it was observed that after 10 cycles, the residual activity for entrapped lipase was as high as 50%, implying that the developed hydrogel and immobilized system could provide a promising solution for the flavor ester synthesis at the industrial scale. PMID:24701136

  3. Electro-response characteristic of starch hydrogel crosslinked with Glutaraldehyde.

    PubMed

    Gao, Ling-xiang; Chen, Jian-li; Han, Xue-wu; Yan, Shu-xian; Zhang, Yan; Zhang, Wei-qiang; Gao, Zi-wei

    2015-01-01

    The facile synthesis of the starch hydrogel with anisotropic microstructure and dynamic behaviors was developed in the presence (A-gel) and absence of DC electric field (B-gel). The microstructures of hydrogels were characterized by environmental scanning electron microscope. Their electro-responsive property of hydrogels was investigated with their storage modulus (G'). The result demonstrates that the G' of A-gel is greater than that of B-gel, and the modulus of A-gel increases along with the external field, which signifies positive electroresponse. In addition, the G' of A-gel and B-gel ((G'(A) and G'(B)) also continuously increases with increasing starch concentration, whereas both the maximum of modulus increment (ΔG' = G'(A)−G'(B) ) and that of modulus increment sensitivity (ΔG'/G'(B)) occur with the starch weight fraction at around 36.5%. To enhance the electro-responsive effects of the hydrogels, dielectric particles were dispersed in the hydrogel. It is found that BaTiO3/chitosan core-shell composite particles significantly enhance the electroresponse of the hydrogel. The mechanism of the electro-response mode is proposed. PMID:25849098

  4. Study of stiffness effects of poly(amidoamine)-poly(n-isopropyl acrylamide) hydrogel on wound healing.

    PubMed

    Chen, Shixuan; Shi, Junbin; Xu, Xiaolin; Ding, Jianyang; Zhong, Wen; Zhang, Lu; Xing, Malcolm; Zhang, Lin

    2016-04-01

    The mechanical miss-match between the host and an implanted foreign body is one of the primary causes for implantation failure. To enhance the efficacy in wound repair, we developed stiffness-tunable temperature-sensitive hydrogels composed of poly(amidoamine) (PAA)-based poly(n-isopropyl acrylamide) (PNIPAM). PNIPAM-PAA hydrogels with three different stiffness fabricated by varying the concentrations of poly(amidoamine) were chosen for morphology and rheology tests. The degradation rate and cell compatibility of gels were also characterized. The PAA-PNIPAM hydrogels were then tested in a wound healing model of mice with full-thickness skin loss. We found that the stiffness of hydrogels has an impact on the wound healing process mainly by regulating the cell activities in the proliferation phase. PNIPAM-PAA hydrogels with appropriate stiffness reduce scar formation and improve wound healing by promoting myofibroblast transformation, keratinocytes proliferation, extracellular matrix synthesis and remodeling. Moreover, the stiffness of hydrogels impact on the secretion of TGF-β1 and bFGF, which play an important role in skin wound healing. These results suggest that the therapeutic effects of hydrogels in skin wound healing can by regulated by hydrogels' stiffness. PMID:26628331

  5. Rheological behaviour of irradiated wound dressing poly(vinyl pyrrolidone) hydrogels

    NASA Astrophysics Data System (ADS)

    Lugão, Ademar B.; Rogero, Sizue O.; Malmonge, Sônia M.

    2002-03-01

    The use of hydrogels as biomaterials has increased lately. Poly(vinyl pyrrolidone) (PVP) is an example of polymer hydrogels applied for the synthesis of hydrogel to be used in different biomedical applications. This paper describes a study on rheological properties of PVP hydrogels obtained by gamma radiation techniques. PVP hydrogels were obtained by gamma radiation of PVP water solutions with different radiation doses. It was studied the influence of additives such as poly(ethylene glycol) (PEG), poly(ethylene oxide) (PEO) and glycerol on the rheological behaviour of the gel. The rheological behaviour of hydrogel samples was characterized by measuring the shear storage modulus ( G') under dynamic shear loading. Besides this, sterility and cytotoxicity tests were performed. The study on rheological behaviour of hydrogels showed that G' of PVP gels change according to the additive used. Glycerol increases the fluidity of the gel. The influence of PEG depends on the amount and on its molecular mass. The increase on PEG amount and molecular mass cause a decrease of G' and an increase in the crosslinking density of PVP hydrogel network. The use of high molecular weight PEO allows the increase of the elasticity of the PVP gels.

  6. Hyperbranched Polyester Hydrogels with Controlled Drug Release and Cell Adhesion Properties

    PubMed Central

    Zhang, Hongbin; Patel, Alpesh; Gaharwar, Akhilesh K.; Mihaila, Silvia M.; Iviglia, Giorgio; Mukundan, Shilpaa; Bae, Hojae; Yang, Huai; Khademhosseini, Ali

    2013-01-01

    Hyperbranched polyesters (HPE) have a high efficiency to encapsulate bioactive agents, including drugs, genes and proteins, due to their globe-like nanostructure. However, the use of these highly branched polymeric systems for tissue engineering applications has not been broadly investigated. Here, we report synthesis and characterization of photocrosslinkable HPE hydrogels with sustained drug release characteristics for cellular therapies. These HPE can encapsulate hydrophobic drug molecules within the HPE cavities, due to the presence of hydrophobic inner structure that is otherwise difficult to achieve in conventional hydrogels. The functionalization of HPE with photocrosslinkable acrylate moieties renders the formation of hydrogels with highly porous interconnected structure, and mechanically tough network. The compressive modulus of HPE hydrogels was tunable by changing the crosslinking density. The feasibility of using these HPE networks for cellular therapies was investigated by evaluating cell adhesion, spreading and proliferation on hydrogel surface. Highly crosslinked and mechanically stiff HPE hydrogels have higher cell adhesion, spreading, proliferation compared to soft and complaint HPE hydrogels. Overall, we showed that hydrogels made from HPE could be used for biomedical applications that require control cell adhesion and control release of hydrophobic clues. PMID:23394067

  7. Synthesis and characterization of magnetite nanoparticles encapsulated in a bovine hemoglobin microgel

    NASA Astrophysics Data System (ADS)

    Mody, Puja J.

    This study shows the successful synthesis and characterization of a novel material that is composed of iron oxide particles within a protein gel. During the synthesis, bovine hemoglobin surrounds the forming Fe 3O4 nanoparticles, resulting in a biocompatible hydrogel, which has the potential to be used as a targeted drug delivery vehicle and as an MRI contrast agent. The structure, size, and thermal stability of these hydrogel complexes were analyzed using a range of techniques. Powder x-ray diffraction and infrared spectroscopy indicated the presence of Fe3O 4 and hemoglobin without significant interactions between particles in the solid state. Microscopy analysis determined the average size of these microgel complexes to be 4-9 mum2 in area (˜2-3 mum in diameter), and DSC analysis indicated that none of the microgels exhibited a denaturing or unfolding transition below 54°C regardless of the iron: hemoglobin ratio. Initial testing has been performed on the ability of these materials to act as magnetically activated drug delivery vehicles. Other pertinent tests (for magnetic properties and MRI applicability) are currently proceeding at external labs.

  8. Tuning the Protein Corona of Hydrogel Nanoparticles: The Synthesis of Abiotic Protein and Peptide Affinity Reagents.

    PubMed

    O'Brien, Jeffrey; Shea, Kenneth J

    2016-06-21

    Nanomaterials, when introduced into a complex, protein-rich environment, rapidly acquire a protein corona. The type and amount of proteins that constitute the corona depend significantly on the synthetic identity of the nanomaterial. For example, hydrogel nanoparticles (NPs) such as poly(N-isopropylacrylamide) (NIPAm) have little affinity for plasma proteins; in contrast, carboxylated poly(styrene) NPs acquire a dense protein corona. This range of protein adsorption suggests that the protein corona might be "tuned" by controlling the chemical composition of the NP. In this Account, we demonstrate that small libraries of synthetic polymer NPs incorporating a diverse pool of functional monomers can be screened for candidates with high affinity and selectivity to targeted biomacromolecules. Through directed synthetic evolution of NP compositions, one can tailor the protein corona to create synthetic organic hydrogel polymer NPs with high affinity and specificity to peptide toxins, enzymes, and other functional proteins, as well as to specific domains of large proteins. In addition, many NIPAm NPs undergo a change in morphology as a function of temperature. This transformation often correlates with a significant change in NP-biomacromolecule affinity, resulting in a temperature-dependent protein corona. This temperature dependence has been used to develop NP hydrogels with autonomous affinity switching for the protection of proteins from thermal stress and as a method of biomacromolecule purification through a selective thermally induced catch and release. In addition to temperature, changes in pH or buffer can also alter a NP protein corona composition, a property that has been exploited for protein purification. Finally, synthetic polymer nanoparticles with low nanomolar affinity for a peptide toxin were shown to capture and neutralize the toxin in the bloodstream of living mice. While the development of synthetic polymer alternatives to protein affinity reagents is

  9. Characterizations of semi-interpenetrating polymer network hydrogels constructed with chitosan and polyacrylonitrile

    NASA Astrophysics Data System (ADS)

    Shin, Su Ryon; Yoon, Seoung Gil; Park, Sang Jun; Lee, Ki Jung; Lee, Chang Kee; Kim, Sun I.; Kim, Seon Jeong

    2003-07-01

    Temperature-, pH- and electrical-responsive semi-interpenetrating polymer network (semi-IPN) hydrogels constructed with chitosan and polyacrylonitrile (PAN) were studied. The swelling ratio of hydrogels depends on pH and temperature. The stimuli response of the semi-IPN hydrogel in electric fields was also investigated. When swollen, the semi-IPN was placed between a pair of electrodes, and it exhibited bending behavior upon the application of an electric field. The electro responsive behavior of the present semi-IPN was also affected by the electrolyte concentration of the external solution. The semi-IPN also showed various degrees of increase of bending behavior depending on the electrical stimulus.

  10. Preclinical characterization and safety of a novel hydrogel for augmenting dural repair

    NASA Astrophysics Data System (ADS)

    Strong, Michael J.; Carnahan, Michael A.; D'Alessio, Keith; Butlin, Jared D. G.; Butt, Mark T.; Asher, Anthony L.

    2015-09-01

    Cerebrospinal fluid (CSF) leakage is a potentially serious complication in surgical procedures involving opening of the dura mater. Although several materials have been developed to help achieve watertight dural closures, CSF leakages persist. The goal of this study was to evaluate the performance of a novel hydrogel designed to provide augmentation to standard methods of dural repair. Performance measures such as polymerization time, dimensional swelling, burst strength, and elasticity were examined in laboratory situations. Additionally, biocompatibility in an in vivo rat model was examined. The results demonstrate that this novel hydrogel has superior mechanical strength and tissue adherence with enhanced flexibility, reduced swelling, and quicker set time compared with existing hydrogel dural sealants approved for intra-cranial use. Furthermore, biocompatibility studies demonstrate that this compound is both non-toxic and non-immunogenic.

  11. Gamma ray-induced synthesis of hyaluronic acid/chondroitin sulfate-based hydrogels for biomedical applications

    NASA Astrophysics Data System (ADS)

    Zhao, Linlin; Gwon, Hui-Jeong; Lim, Youn-Mook; Nho, Young-Chang; Kim, So Yeon

    2015-01-01

    Hyaluronic acid (HA)/chondroitin sulfate (CS)/poly(acrylic acid) (PAAc) hydrogel systems were synthesized by gamma-ray irradiation without the use of additional initiators or crosslinking agents to achieve a biocompatible hydrogel system for skin tissue engineering. HA and CS derivatives with polymerizable residues were synthesized. Then, the hydrogels composed of glycosaminoglycans, HA, CS, and a synthetic ionic polymer, PAAc, were prepared using gamma-ray irradiation through simultaneous free radical copolymerization and crosslinking. The physicochemical properties of the HA/CS/PAAc hydrogels having various compositions were investigated to evaluate their feasibility as artificial skin substitutes. The gel fractions of the HA/CS/PAAc hydrogels increased in absorbed doses up to 15 kGy, and they exhibited 91-93% gel fractions under 15 kGy radiation. All of the HA/CS/PAAc hydrogels exhibited relatively high water contents of over 90% and reached an equilibrium swelling state within 24 h. The enzymatic degradation kinetics of the HA/CS/PAAc hydrogels depended on both the concentration of the hyaluronidase solution and the ratio of HA/CS/PAAc. The in vitro drug release profiles of the HA/CS/PAAc hydrogels were significantly influenced by the interaction between the ionic groups in the hydrogels and the ionic drug molecules as well as the swelling of the hydrogels. From the cytotoxicity results of human keratinocyte (HaCaT) cells cultured with extracts of the HA/CS/PAAc hydrogels, all of the HA/CS/PAAc hydrogel samples tested showed relatively high cell viabilities of more than 82%, and did not induce any significant adverse effects on cell viability.

  12. Multi-scale mechanical characterization of highly swollen photo-activated collagen hydrogels.

    PubMed

    Tronci, Giuseppe; Grant, Colin A; Thomson, Neil H; Russell, Stephen J; Wood, David J

    2015-01-01

    Biological hydrogels have been increasingly sought after as wound dressings or scaffolds for regenerative medicine, owing to their inherent biofunctionality in biological environments. Especially in moist wound healing, the ideal material should absorb large amounts of wound exudate while remaining mechanically competent in situ. Despite their large hydration, however, current biological hydrogels still leave much to be desired in terms of mechanical properties in physiological conditions. To address this challenge, a multi-scale approach is presented for the synthetic design of cyto-compatible collagen hydrogels with tunable mechanical properties (from the nano- up to the macro-scale), uniquely high swelling ratios and retained (more than 70%) triple helical features. Type I collagen was covalently functionalized with three different monomers, i.e. 4-vinylbenzyl chloride, glycidyl methacrylate and methacrylic anhydride, respectively. Backbone rigidity, hydrogen-bonding capability and degree of functionalization (F: 16 ± 12-91 ± 7 mol%) of introduced moieties governed the structure-property relationships in resulting collagen networks, so that the swelling ratio (SR: 707 ± 51-1996 ± 182 wt%), bulk compressive modulus (Ec: 30 ± 7-168 ± 40 kPa) and atomic force microscopy elastic modulus (EAFM: 16 ± 2-387 ± 66 kPa) were readily adjusted. Because of their remarkably high swelling and mechanical properties, these tunable collagen hydrogels may be further exploited for the design of advanced dressings for chronic wound care. PMID:25411409

  13. Multi-scale mechanical characterization of highly swollen photo-activated collagen hydrogels

    PubMed Central

    Tronci, Giuseppe; Grant, Colin A.; Thomson, Neil H.; Russell, Stephen J.; Wood, David J.

    2015-01-01

    Biological hydrogels have been increasingly sought after as wound dressings or scaffolds for regenerative medicine, owing to their inherent biofunctionality in biological environments. Especially in moist wound healing, the ideal material should absorb large amounts of wound exudate while remaining mechanically competent in situ. Despite their large hydration, however, current biological hydrogels still leave much to be desired in terms of mechanical properties in physiological conditions. To address this challenge, a multi-scale approach is presented for the synthetic design of cyto-compatible collagen hydrogels with tunable mechanical properties (from the nano- up to the macro-scale), uniquely high swelling ratios and retained (more than 70%) triple helical features. Type I collagen was covalently functionalized with three different monomers, i.e. 4-vinylbenzyl chloride, glycidyl methacrylate and methacrylic anhydride, respectively. Backbone rigidity, hydrogen-bonding capability and degree of functionalization (F: 16 ± 12–91 ± 7 mol%) of introduced moieties governed the structure–property relationships in resulting collagen networks, so that the swelling ratio (SR: 707 ± 51–1996 ± 182 wt%), bulk compressive modulus (Ec: 30 ± 7–168 ± 40 kPa) and atomic force microscopy elastic modulus (EAFM: 16 ± 2–387 ± 66 kPa) were readily adjusted. Because of their remarkably high swelling and mechanical properties, these tunable collagen hydrogels may be further exploited for the design of advanced dressings for chronic wound care. PMID:25411409

  14. Characterization of Lactate Sensors Based on Lactate Oxidase and Palladium Benzoporphyrin Immobilized in Hydrogels.

    PubMed

    Andrus, Liam P; Unruh, Rachel; Wisniewski, Natalie A; McShane, Michael J

    2015-01-01

    An optical biosensor for lactate detection is described. By encapsulating enzyme-phosphor sensing molecules within permeable hydrogel materials, lactate-sensitive emission lifetimes were achieved. The relative amount of monomer was varied to compare three homo- and co-polymer materials: poly(2-hydroxyethyl methacrylate) (pHEMA) and two copolymers of pHEMA and poly(acrylamide) (pAam). Diffusion analysis demonstrated the ability to control lactate transport by varying the hydrogel composition, while having a minimal effect on oxygen diffusion. Sensors displayed the desired dose-variable response to lactate challenges, highlighting the tunable, diffusion-controlled nature of the sensing platform. Short-term repeated exposure tests revealed enhanced stability for sensors comprising hydrogels with acrylamide additives; after an initial "break-in" period, signal retention was 100% for 15 repeated cycles. Finally, because this study describes the modification of a previously developed glucose sensor for lactate analysis, it demonstrates the potential for mix-and-match enzyme-phosphor-hydrogel sensing for use in future multi-analyte sensors. PMID:26198251

  15. Characterization of Lactate Sensors Based on Lactate Oxidase and Palladium Benzoporphyrin Immobilized in Hydrogels

    PubMed Central

    Andrus, Liam P.; Unruh, Rachel; Wisniewski, Natalie A.; McShane, Michael J.

    2015-01-01

    An optical biosensor for lactate detection is described. By encapsulating enzyme-phosphor sensing molecules within permeable hydrogel materials, lactate-sensitive emission lifetimes were achieved. The relative amount of monomer was varied to compare three homo- and co-polymer materials: poly(2-hydroxyethyl methacrylate) (pHEMA) and two copolymers of pHEMA and poly(acrylamide) (pAam). Diffusion analysis demonstrated the ability to control lactate transport by varying the hydrogel composition, while having a minimal effect on oxygen diffusion. Sensors displayed the desired dose-variable response to lactate challenges, highlighting the tunable, diffusion-controlled nature of the sensing platform. Short-term repeated exposure tests revealed enhanced stability for sensors comprising hydrogels with acrylamide additives; after an initial “break-in” period, signal retention was 100% for 15 repeated cycles. Finally, because this study describes the modification of a previously developed glucose sensor for lactate analysis, it demonstrates the potential for mix-and-match enzyme-phosphor-hydrogel sensing for use in future multi-analyte sensors. PMID:26198251

  16. Design, fabrication and characterization of oxidized alginate-gelatin hydrogels for muscle tissue engineering applications.

    PubMed

    Baniasadi, Hossein; Mashayekhan, Shohreh; Fadaoddini, Samira; Haghirsharifzamini, Yasamin

    2016-07-01

    In this study, we reported the preparation of self cross-linked oxidized alginate-gelatin hydrogels for muscle tissue engineering. The effect of oxidation degree (OD) and oxidized alginate/gelatin (OA/GEL) weight ratio were examined and the results showed that in the constant OA/GEL weight ratio, both cross-linking density and Young's modulus enhanced by increasing OD due to increment of aldehyde groups. Furthermore, the degradation rate was increased with increasing OD probably due to decrement in alginate molecular weight during oxidation reaction facilitated degradation of alginate chains. MTT cytotoxicity assays performed on Wharton's Jelly-derived umbilical cord mesenchymal stem cells cultured on hydrogels with OD of 30% showed that the highest rate of cell proliferation belong to hydrogel with OA/GEL weight ratio of 30/70. Overall, it can be concluded from all obtained results that the prepared hydrogel with OA/GEL weight ratio and OD of 30/70 and 30%, respectively, could be proper candidate for use in muscle tissue engineering. PMID:26916948

  17. Preparation and characterization of a composite hydrogel with graphene oxide as an acid catalyst.

    PubMed

    Jiang, Ting; Sui, Zhu-Yin; Yang, Quan-Sheng; Zhang, Xuetong; Han, Bao-Hang

    2015-04-28

    In this study, a facile method for synthesizing a novel graphene oxide/pyrrole-formaldehyde (GOP-1) composite hydrogel was developed via in situ polymerization of pyrrole and formaldehyde in the presence of graphene oxide sheets without any additional catalyst. During the polymerization, graphene oxide can act as a two-dimensional template to regulate the aggregation state of polymer and as an acid catalyst to accelerate the reaction rate of pyrrole and formaldehyde. The morphology and microstructure were investigated by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, respectively. The chemical properties were analyzed via X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. The freeze-dried GOP-1 composite hydrogel exhibited a large specific surface area, high nitrogen content, and three-dimensional network structure. Based on the above features, the freeze-dried GOP-1 composite hydrogel used as a gas adsorbent showed a high carbon dioxide uptake capacity at 1.0 bar and 273 K (11.1 wt%), in sharp contrast to that of graphene oxide (7.4 wt%). Furthermore, the as-prepared composite hydrogel may possess attractive potential in the fields of electrode material, tissue engineering, and water treatment. PMID:25760407

  18. Biocompatibility and Characterization of a Peptide Amphiphile Hydrogel for Applications in Peripheral Nerve Regeneration

    PubMed Central

    Black, Katie A.; Lin, Brian F.; Wonder, Emily A.; Desai, Seema S.; Chung, Eun Ji; Ulery, Bret D.; Katari, Ravi S.

    2015-01-01

    Peripheral nerve injury is a debilitating condition for which new bioengineering solutions are needed. Autografting, the gold standard in treatment, involves sacrifice of a healthy nerve and results in loss of sensation or function at the donor site. One alternative solution to autografting is to use a nerve guide conduit designed to physically guide the nerve as it regenerates across the injury gap. Such conduits are effective for short gap injuries, but fail to surpass autografting in long gap injuries. One strategy to enhance regeneration inside conduits in long gap injuries is to fill the guide conduits with a hydrogel to mimic the native extracellular matrix found in peripheral nerves. In this work, a peptide amphiphile (PA)-based hydrogel was optimized for peripheral nerve repair. Hydrogels consisting of the PA C16GSH were compared with a commercially available collagen gel. Schwann cells, a cell type important in the peripheral nerve regenerative cascade, were able to spread, proliferate, and migrate better on C16GSH gels in vitro when compared with cells seeded on collagen gels. Moreover, C16GSH gels were implanted subcutaneously in a murine model and were found to be biocompatible, degrade over time, and support angiogenesis without causing inflammation or a foreign body immune response. Taken together, these results help optimize and instruct the development of a new synthetic hydrogel as a luminal filler for conduit-mediated peripheral nerve repair. PMID:25626921

  19. Characterization of glycidyl methacrylate – Crosslinked hyaluronan hydrogel scaffolds incorporating elastogenic hyaluronan oligomers

    PubMed Central

    Ibrahim, S.; Kothapalli, C.R.; Kang, Q.K.; Ramamurthi, A.

    2013-01-01

    Prior studies on two-dimensional cell cultures suggest that hyaluronic acid (HA) stimulates cell-mediated regeneration of extracellular matrix structures, specifically those containing elastin, though such biologic effects are dependent on HA fragment size. Towards being able to regenerate three-dimensional (3-D) elastic tissue constructs, the present paper studies photo-crosslinked hydrogels containing glycidyl methacrylate (GM)-derivatized bio-inert high molecular weight(HMW)HA (1 × 106 Da) and a bioactive HA oligomer mixture (HA-o: MW ~0.75 kDa). The mechanical (rheology, degradation) and physical (apparent crosslinking density, swelling ratio) properties of the gels varied as a function of incorporated HA oligomer content; however, overall, the mechanics of these hydrogels were too weak for vascular applications as stand-alone materials. Upon in vivo subcutaneous implantation, only a few inflammatory cells were evident around GM–HA gels, however their number increased as HA-o content within the gels increased, and the collagen I distribution was uniform. Smooth muscle cells (SMC) were encapsulated into GM hydrogels, and calcein acetoxymethyl detection revealed that the cells were able to endure twofold the level of UV exposure used to crosslink the gels. After 21 days of culture, SMC elastin production, measured by immunofluorescence quantification, showed HA-o to increase cellular deposition of elastic matrix twofold relative to HA-o-free GM–HAgels. These results demonstrate that cell response to HA/HA-o is not altered by their methacrylation and photo-crosslinking into a hydrogel, and that HA-o incorporation into cell-encapsulating hydrogel scaffolds can be useful for enhancing their production of elastic matrix structures in a 3-D space, important for regenerating elastic tissues. PMID:20709199

  20. Characterization of glycidyl methacrylate - crosslinked hyaluronan hydrogel scaffolds incorporating elastogenic hyaluronan oligomers.

    PubMed

    Ibrahim, S; Kothapalli, C R; Kang, Q K; Ramamurthi, A

    2011-02-01

    Prior studies on two-dimensional cell cultures suggest that hyaluronic acid (HA) stimulates cell-mediated regeneration of extracellular matrix structures, specifically those containing elastin, though such biologic effects are dependent on HA fragment size. Towards being able to regenerate three-dimensional (3-D) elastic tissue constructs, the present paper studies photo-crosslinked hydrogels containing glycidyl methacrylate (GM)-derivatized bio-inert high molecular weight (HMW) HA (1 × 10(6)Da) and a bioactive HA oligomer mixture (HA-o: MW ∼0.75 kDa). The mechanical (rheology, degradation) and physical (apparent crosslinking density, swelling ratio) properties of the gels varied as a function of incorporated HA oligomer content; however, overall, the mechanics of these hydrogels were too weak for vascular applications as stand-alone materials. Upon in vivo subcutaneous implantation, only a few inflammatory cells were evident around GM-HA gels, however their number increased as HA-o content within the gels increased, and the collagen I distribution was uniform. Smooth muscle cells (SMC) were encapsulated into GM hydrogels, and calcein acetoxymethyl detection revealed that the cells were able to endure twofold the level of UV exposure used to crosslink the gels. After 21 days of culture, SMC elastin production, measured by immunofluorescence quantification, showed HA-o to increase cellular deposition of elastic matrix twofold relative to HA-o-free GM-HA gels. These results demonstrate that cell response to HA/HA-o is not altered by their methacrylation and photo-crosslinking into a hydrogel, and that HA-o incorporation into cell-encapsulating hydrogel scaffolds can be useful for enhancing their production of elastic matrix structures in a 3-D space, important for regenerating elastic tissues. PMID:20709199

  1. Synthesis of linear low-density polyethylene-g-poly (acrylic acid)-co-starch/organo-montmorillonite hydrogel composite as an adsorbent for removal of Pb(ΙΙ) from aqueous solutions.

    PubMed

    Irani, Maryam; Ismail, Hanafi; Ahmad, Zulkifli; Fan, Maohong

    2015-01-01

    The purpose of this work is to remove Pb(II) from the aqueous solution using a type of hydrogel composite. A hydrogel composite consisting of waste linear low density polyethylene, acrylic acid, starch, and organo-montmorillonite was prepared through emulsion polymerization method. Fourier transform infrared spectroscopy (FTIR), Solid carbon nuclear magnetic resonance spectroscopy (CNMR)), silicon(-29) nuclear magnetic resonance spectroscopy (Si NMR)), and X-ray diffraction spectroscope ((XRD) were applied to characterize the hydrogel composite. The hydrogel composite was then employed as an adsorbent for the removal of Pb(II) from the aqueous solution. The Pb(II)-loaded hydrogel composite was characterized using Fourier transform infrared spectroscopy (FTIR)), scanning electron microscopy (SEM)), and X-ray photoelectron spectroscopy ((XPS)). From XPS results, it was found that the carboxyl and hydroxyl groups of the hydrogel composite participated in the removal of Pb(II). Kinetic studies indicated that the adsorption of Pb(II) followed the pseudo-second-order equation. It was also found that the Langmuir model described the adsorption isotherm better than the Freundlich isotherm. The maximum removal capacity of the hydrogel composite for Pb(II) ions was 430mg/g. Thus, the waste linear low-density polyethylene-g-poly (acrylic acid)-co-starch/organo-montmorillonite hydrogel composite could be a promising Pb(II) adsorbent. PMID:25597658

  2. Enzyme Induced Formation of Monodisperse Hydrogel Nanoparticles Tunable in Size

    SciTech Connect

    Bocharova, Vera; Sharp, Danna; Jones, Aaron; Cheng, Shiwang; Griffin, Philip J.; Agapov, Alexander L.; Voylov, Dmitry; Wang, Yangyang; Kisliuk, Alexander; Melman, Artem; Sokolov, Alexei P.

    2015-03-09

    Here, we report a novel approach to synthesize monodisperse hydrogel nanoparticles that are tunable in size. The distinctive feature of our approach is the use of a multicopper oxidase enzyme, laccase, as both a biocatalyst and template for nanoparticle growth. We utilize the ferroxidase activity of laccase to initiate localized production of iron(III) cations from the oxidation of iron(II) cations. We demonstrate that nanoparticles are formed in a dilute polymer solution of alginate as a result of cross-linking between alginate and enzymatically produced iron(III) cations. Exerting control over the enzymatic reaction allows for nanometer-scale tuning of the hydrogel nanoparticle radii in the range of 30–100 nm. Moreover, the nanoparticles and their growth kinetics were characterized via dynamic light scattering, atomic force microscopy, and UV–vis spectroscopy. Our finding opens up a new avenue for the synthesis of tunable nanoscale hydrogel particles for biomedical applications.

  3. Characterization and manipulation of the in vivo host response and in vitro macrophage response to synthetic hydrogels

    NASA Astrophysics Data System (ADS)

    Lynn, Aaron David

    Tissue engineering hope to fill the donor gap between patient needing transplantation and donors able to provide organs. Many challenges exist in the engineering of replacement tissues such as cell sourcing and scaffold design. A particularly promising group of scaffolds used extensively in tissue engineering research are based on cross-linked poly(ethylene glycol) (PEG) hydrogels. Materials based on these gels have been selected for their tissue-like high water content, low cell toxicty, mild polymerization conditions and the ease with which their mechanical and chemical properties can be tuned. However, all materials which will ultimately be implanted into will elicit a host response. This reaction is initiated when a wound is created. It leads to bathing of the material in proteins from the blood, recruitment, attachment and interrogation of the material by macrophages, attempted degradation and phagocytosis, macrophage fusion into foreign body giant cells (FBGCs) and ultimately the "walling off" of the implant as a dense collagenous capsule surrounds the material restricting further interactions with the host. This foreign body response (FBR) is well studied and contributes significantly to premature failure of implanted medical devices. The research presented in this thesis aims to characterize the FBR to PEG-based tissue engineering scaffolds with the intention of uncovering mechanisms by which the response can be attenuated. To this end, implantation studies have been performed to gauge the severity of the foreign body response to these hydrogels and to establish to what degree modifications with the cell adhesion peptide alter this reaction in vivo. Additionally, in vitro models were established to study characteristics of the the early (< 1 week), middle (1-2 weeks) and late phases (> 2 weeks) of the FBR. Studies were performed to determine the potentially detrimental effects of macrophage interrogation of a PEG-based skin tissue engineering system

  4. Synthesis and Characterization of Nanowires

    SciTech Connect

    Musket, R.G.; Felter, T.; Quong, A.

    2000-03-01

    With the dimensions of components in microelectronic circuits shrinking, the phenomena associated with electronic conduction through wires and with device operation can be expected to change. For example, as the length of electrical conductors is reduced, ballistic transport will become the main mode of conduction. Sufficient reduction in the cross sectional area of conductors can lead to quantum confinement effects. Prior knowledge of the phenomena associated with decreasing size should help guide the designers of future, smaller devices in terms of geometry and materials. However, prior knowledge requires the availability of sufficiently small nanowires for experiments. To date, the smallest nanowires that have been fabricated and investigated had diameters of 8 nm. We propose to extend the investigation of these size-related phenomena by synthesizing, using a novel version of nuclear, or ion, track lithography and characterizing, physically and electrically, nanowires with diameters D of 1 to 5 nm and lengths L of 2 to 250 nm. Thus, by varying the dimensions of the nanowires, we will be able to determine experimentally when the ideas of macroscopic conductance break down and the conductance becomes dominated by quantum and ballistic effects. In our approach the nature of the small-diameter nanostructure formed can be controlled: Nanowires are formed when L/D is large, and quantum dots are formed when both L and D are small. Theoretical calculations will be performed to both guide and understand the experimental studies. We have examined several aspects of this challenging problem and generated some promising results, but the project was not extended for the second year as planned. Thus, we did not have sufficient resources to complete the proof of concept.

  5. Characterization of Molecular Transport in Ultrathin Hydrogel Coatings for Cellular Immunoprotection

    PubMed Central

    Lilly, Jacob L.; Romero, Gabriela; Xu, Weijie; Shin, Hainsworth Y.; Berron, Brad J.

    2015-01-01

    PEG hydrogels are routinely used in immunoprotection applications to hide foreign cells from a host immune system. Size dependent transport is typically exploited in these systems to prevent access by macromolecular elements of the immune system while allowing the transport of low molecular weight nutrients. This work studies a nanoscale hydrogel coating for improved transport of beneficial low molecular weight materials across thicker hydrogel coatings while completely blocking transport of undesired larger molecular weight materials. Coatings composed of PEG diacrylate of molecular weight 575 Da and 3500 Da were studied by tracking the transport of fluorescently-labeled dextrans across the coatings. The molecular weight of dextran at which the transport is blocked by these coatings are consistent with cutoff values in analogous bulk PEG materials. Additionally, the diffusion constants of 4 kDa dextrans across PEG 575 coatings (9.5×10−10 – 2.0×10−9 cm2/s) was lower than across PEG 3500 coatings (5.9 – 9.8×10−9 cm2/s), and these trends and magnitudes agree with bulk scale models. Overall, these nanoscale thin PEG diacrylate films offer the same size selective transport behavior of bulk PEG diacrylate materials, while the lower thickness translates directly to increased flux of beneficial low molecular weight materials. PMID:25592156

  6. ECM hydrogel for the treatment of stroke: Characterization of the host cell infiltrate.

    PubMed

    Ghuman, Harmanvir; Massensini, Andre R; Donnelly, Julia; Kim, Sung-Min; Medberry, Christopher J; Badylak, Stephen F; Modo, Michel

    2016-06-01

    Brain tissue loss following stroke is irreversible with current treatment modalities. The use of an acellular extracellular matrix (ECM), formulated to produce a hydrogel in situ within the cavity formed by a stroke, was investigated as a method to replace necrotic debris and promote the infiltration of host brain cells. Based on magnetic resonance imaging measurements of lesion location and volume, different concentrations of ECM (0, 1, 2, 3, 4, 8 mg/mL) were injected at a volume equal to that of the cavity (14 days post-stroke). Retention of ECM within the cavity occurred at concentrations >3 mg/mL. A significant cell infiltration into the ECM material in the lesion cavity occurred with an average of ∼36,000 cells in the 8 mg/mL concentration within 24 h. An infiltration of cells with distances of >1500 μm into the ECM hydrogel was observed, but the majority of cells were at the tissue/hydrogel boundary. Cells were typically of a microglia, macrophage, or neural and oligodendrocyte progenitor phenotype. At the 8 mg/mL concentration, ∼60% of infiltrating cells were brain-derived phenotypes and 30% being infiltrating peripheral macrophages, polarizing toward an M2-like anti-inflammatory phenotype. These results suggest that an 8 mg/mL ECM concentration promotes a significant acute endogenous repair response that could potentially be exploited to treat stroke. PMID:27031811

  7. Preparation, characterization and magnetic behavior of a spin-labelled physical hydrogel containing a chiral cyclic nitroxide radical unit fixed inside the gelator molecule.

    PubMed

    Takemoto, Yusa; Yamamoto, Takayuki; Ikuma, Naohiko; Uchida, Yoshiaki; Suzuki, Katsuaki; Shimono, Satoshi; Takahashi, Hiroki; Sato, Nobuhiro; Oba, Yojiro; Inoue, Rintaro; Sugiyama, Masaaki; Tsue, Hirohito; Kato, Tatsuhisa; Yamauchi, Jun; Tamura, Rui

    2015-07-21

    An optically active amphiphilic nitroxide radical compound [(S,S,R)-], which contains a paramagnetic (2S,5S)-2,5-dimethyl-2,5-diphenylpyrrolidine-N-oxyl radical group fixed in the inner position together with a hydrophobic long alkyl chain and a hydrophilic (R)-alanine residue in the opposite terminal positions, was found to serve as a low-molecular-weight gelator in H2O to give rise to a spin-labelled physical hydrogel. Characterization of the hydrogel was performed by microscopic (SEM, TEM and AFM) techniques, XRD and SAXS measurements, and IR, UV and CD spectroscopies. The gel-sol transition temperature was determined by EPR spectral line-width (ΔHpp) analysis. Measurement of the temperature dependence of relative paramagnetic susceptibility (χrel) for the hydrogel and sol phases was achieved by means of the double-integration of VT-EPR spectra. PMID:26073537

  8. Design and Characterization of Micro-Porous Hyaluronic Acid Hydrogels for in vitro Gene Transfer to mMSCs

    PubMed Central

    Tokatlian, Talar; Cam, Cynthia; Siegman, Shayne N.; Lei, Yuguo; Segura, Tatiana

    2013-01-01

    The effective and sustained delivery of DNA locally would increase the applicability of gene therapy in tissue regeneration and therapeutic angiogenesis. One promising approach is to use porous hydrogel scaffolds to encapsulate and deliver nucleotides in the form of nanoparticles to the affected sites. We have designed and characterized micro-porous (µ-pore) hyaluronic acid hydrogels which allow for effective cell seeding in vitro post scaffold fabrication and allow for cell spreading and proliferation without requiring high levels of degradation. These factors, coupled with high loading efficiency of DNA polyplexes using a previously developed caged nanoparticle encapsulation (CnE) technique, then allowed for long-term sustained transfection and transgene expression of incorporated mMSCs. In this study, we examined the effect of pore size on gene transfer efficiency and the kinetics of transgene expression. For all investigated pore sizes (30, 60, and 100 µm), encapsulated DNA polyplexes were released steadily starting by day 4 for up to 10 days. Likewise, transgene expression was sustained over this period, although significant differences between different pore sizes were not observed. Cell viability was also shown to remain high over time, even in the presence of high concentrations of DNA polyplexes. The knowledge acquired through this in vitro model can be utilized to design and better predict scaffold-mediated gene delivery for local gene therapy in an in vivo model where host cells infiltrate the scaffold over time. PMID:22820309

  9. Synthesis of photoresponsive hybrid alginate hydrogel with photo-controlled release behavior.

    PubMed

    Chiang, Chien-Ying; Chu, Chih-Chien

    2015-03-30

    A photoresponsive hybrid alginate hydrogel was successfully prepared by Ca(2+)-mediated crosslinking reaction with a mixture of β-cyclodextrin-grafted alginate (β-CD-Alg) and diazobenzene-modified poly(ethylene glycol) (Az2-PEG). The water-soluble Az2-PEG exhibits efficient trans-to-cis isomerization of the terminal azobenzene moieties under UV-light irradiation and readily switched back to the initial trans state under visible light. Because of low affinity between β-CD and cis-Az, the host-guest inclusion complex formed by β-CD and trans-Az gradually dissociates under UV-light exposure. Accordingly, the bulk gel exhibits substantial photo-induced transformation in gel morphology by the appearance of significant comb-like cavities. This photosensitive behavior accompanied by the structural degradation enables the rapid release of entrapped dye molecules under UV light stimulus. Moreover, an incident light with higher power and mild acidic environment are capable of accelerating the photo-triggered release, thus allowing the potential applications toward acute wound healing. PMID:25563940

  10. Hydrogels in Regenerative Medicine

    PubMed Central

    Slaughter, Brandon V.; Khurshid, Shahana S.; Fisher, Omar Z.; Khademhosseini, Ali

    2015-01-01

    Hydrogels, due to their unique biocompatibility, flexible methods of synthesis, range of constituents, and desirable physical characteristics, have been the material of choice for many applications in regenerative medicine. They can serve as scaffolds that provide structural integrity to tissue constructs, control drug and protein delivery to tissues and cultures, and serve as adhesives or barriers between tissue and material surfaces. In this work, the properties of hydrogels that are important for tissue engineering applications and the inherent material design constraints and challenges are discussed. Recent research involving several different hydrogels polymerized from a variety of synthetic and natural monomers using typical and novel synthetic methods are highlighted. Finally, special attention is given to the microfabrication techniques that are currently resulting in important advances in the field. PMID:20882499

  11. Mimicking of Chondrocyte Microenvironment Using In Situ Forming Dendritic Polyglycerol Sulfate-Based Synthetic Polyanionic Hydrogels.

    PubMed

    Dey, Pradip; Schneider, Tobias; Chiappisi, Leonardo; Gradzielski, Michael; Schulze-Tanzil, Gundula; Haag, Rainer

    2016-04-01

    A stable polymeric network that mimics the highly polyanionic extracellular cartilage matrix still remains a great challenge. The main aim of this study is to present the synthesis of dendritic polyglycerol sulfate (dPGS)-based in situ forming hydrogels using strain promoted azide-alkyne cycloaddition reactions. A real time rheological study has been used to characterize the hydrogel properties. The viability of encapsulated human chondrocytes in the different hydrogels are monitored using live-dead staining. Furthermore, type I and II collagen gene have been analyzed. Hydrogels with elastic moduli ranging from 1 to 5 kPa have been prepared by varying the dPGS amount. The chondrocyte viability in dPGS hydrogels is found to be higher than in pure PEG and alginate-based hydrogels after 21 d. The higher cell viability in the dPGS engineered hydrogels can be explained by the fact that dPGS can interact with different proteins responsible for cell growth and proliferation. PMID:26753995

  12. Facile synthesis of glucose-sensitive chitosan-poly(vinyl alcohol) hydrogel: Drug release optimization and swelling properties.

    PubMed

    Abureesh, Mosab Ali; Oladipo, Akeem Adeyemi; Gazi, Mustafa

    2016-09-01

    The study describes the development of glucose-sensitive hydrogel and optimization of bovine serum albumin release profile from the hydrogel. To enhance the glucose sensitivity and improve the swelling behaviors of the hydrogel system, boric acid crosslinking, and freeze-thawing cycle techniques were used to prepare chitosan-poly(vinyl alcohol) hydrogel. The structure of the resultant hydrogel was confirmed by scanning electron microscopy and Fourier transform infrared spectroscopy. The experimental results revealed that the swelling of the hydrogel was influenced by the pH of the medium, and the hydrogel displayed explicit glucose-sensitivity under physiological conditions. The values of the diffusion exponent range between 0.34 and 0.44 and the diffusion of water into the gel system are assumed to be pseudo-Fickian in nature. Under optimized conditions, the cumulative Bovine serum albumin (BSA) drug releases ranged between 69.33±1.95% and 86.45±1.16% at 37°C in the presence of glucose and pH 7.4, respectively. PMID:26459171

  13. Synthesis and Properties of Hemostatic and Bacteria-Responsive in Situ Hydrogels for Emergency Treatment in Critical Situations.

    PubMed

    Bu, Yazhong; Zhang, Licheng; Liu, Jianheng; Zhang, Lihai; Li, Tongtong; Shen, Hong; Wang, Xing; Yang, Fei; Tang, Peifu; Wu, Decheng

    2016-05-25

    Immediate hemorrhage control and infection prevention are pivotal for saving lives in critical situations such as battlefields, natural disasters, traffic accidents, and so on. In situ hydrogels are promising candidates, but their mechanical strength is often not strong enough for use in critical situations. In this study, we constructed three hydrogels with different amounts of Schiff-base moieties from 4-arm-PEG-NH2, 4-arm-PEG-NHS, and 4-arm-PEG-CHO in which vancomycin was incorporated as an antimicrobial agent. The hydrogels possess porous structures, excellent mechanical strength, and high swelling ratio. The cytotoxicity studies indicated that the composite hydrogel systems possess good biocompatibility. The Schiff bases incorporated improve the adhesiveness and endow the hydrogels with bacteria-sensitivity. The in vivo hemostatic and antimicrobial experiments on rabbits and pigs demonstrated that the hydrogels are able to aid in rapid hemorrhage control and infection prevention. In summary, vancomycin-loaded hydrogels may be excellent candidates as hemostatic and antibacterial materials for first aid treatment of the wounded in critical situations. PMID:27159886

  14. New antifouling silica hydrogel.

    PubMed

    Beltrán-Osuna, Ángela A; Cao, Bin; Cheng, Gang; Jana, Sadhan C; Espe, Matthew P; Lama, Bimala

    2012-06-26

    In this work, a new antifouling silica hydrogel was developed for potential biomedical applications. A zwitterionic polymer, poly(carboxybetaine methacrylate) (pCBMA), was produced via atom-transfer radical polymerization and was appended to the hydrogel network in a two-step acid-base-catalyzed sol-gel process. The pCBMA silica aerogels were obtained by drying the hydrogels under supercritical conditions using CO(2). To understand the effect of pCBMA on the gel structure, pCBMA silica aerogels with different pCBMA contents were characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and the surface area from Brauner-Emmet-Teller (BET) measurements. The antifouling property of pCBMA silica hydrogel to resist protein (fibrinogen) adsorption was measured using enzyme-linked immunosorbent assay (ELISA). SEM images revealed that the particle size and porosity of the silica network decreased at low pCBMA content and increased at above 33 wt % of the polymer. The presence of pCBMA increased the surface area of the material by 91% at a polymer content of 25 wt %. NMR results confirmed that pCBMA was incorporated completely into the silica structure at a polymer content below 20 wt %. A protein adsorption test revealed a reduction in fibrinogen adsorption by 83% at 25 wt % pCBMA content in the hydrogel compared to the fibrinogen adsorption in the unmodified silica hydrogel. PMID:22607091

  15. Design, synthesis, characterization and study of novel conjugated polymers

    SciTech Connect

    Chen, W.

    1997-06-24

    After introducing the subject of conjugated polymers, the thesis has three sections each containing a literature survey, results and discussion, conclusions, and experimental methods on the following: synthesis, characterization of electroluminescent polymers containing conjugated aryl, olefinic, thiophene and acetylenic units and their studies for use in light-emitting diodes; synthesis, characterization and study of conjugated polymers containing silole unit in the main chain; and synthesis, characterization and study of silicon-bridged and butadiene-linked polythiophenes.

  16. Synthesis, characterization and application of electrode materials

    SciTech Connect

    He, L.

    1995-07-07

    It has been known that significant advances in electrochemistry really depend on improvements in the sensitivity, selectivity, convenience, and/or economy of working electrodes, especially through the development of new working electrode materials. The advancement of solid state chemistry and materials science makes it possible to provide the materials which may be required as satisfactory electrode materials. The combination of solid state techniques with electrochemistry expands the applications of solid state materials and leads to the improvement of electrocatalysis. The study of Ru-Ti{sub 4}O{sub 7} and Pt-Ti{sub 4}O{sub 7} microelectrode arrays as introduced in paper 1 and paper 4, respectively, focuses on their synthesis and characterization. The synthesis is described by high temperature techniques for Ru or Pt microelectrode arrays within a conductive Ti{sub 4}O{sub 7} ceramic matrix. The characterization is based on the data obtained by x-ray diffractometry, scanning electron microscopy, voltammetry and amperometry. These microelectrode arrays show significant enhancement in current densities in comparison to solid Ru and Pt electrodes. Electrocatalysis at pyrochlore oxide Bi{sub 2}Ru{sub 2}O{sub 7.3} and Bi{sub 2}Ir{sub 2}O{sub 7} electrodes are described in paper 2 and paper 3, respectively. Details are reported for the synthesis and characterization of composite Bi{sub 2}Ru{sub 2}O{sub 7.3} electrodes. Voltammetric data are examined for evidence that oxidation can occur with transfer of oxygen to the oxidation products in the potential region corresponding to anodic discharge of H{sub 2}O with simultaneous evolution of O{sub 2}. Paper 3 includes electrocatalytic activities of composite Bi{sub 2}Ir{sub 2}O{sub 7} disk electrodes for the oxidation of I{sup -} and the reduction of IO{sub 3}{sup -}.

  17. Immobilization and characterization of beta-galactosidase in thermally reversible hydrogel beads.

    PubMed

    Park, T G; Hoffman, A S

    1990-01-01

    Beta-Galactosidase has been immobilized within thermally reversible hydrogel beads and has been studied in batch and packed bed reactor systems. The enzyme was entrapped in a copolymer hydrogel of N-isopropylacrylamide (NIPAAm) and acrylamide (AAm) as beads were formed in an inverse suspension polymerization. A reversible deswelling and reswelling of the hydrogel matrix was induced by first warming and then cooling through 37-40 degrees C, which is the lower critical solution temperature, LCST, of the backbone copolymer. The optimum temperature for maximum activity of the immobilized enzyme-gel bead system was found to be 30-35 degrees C in a batch mode and 40 degrees C in a packed bed reactor, which were both below the 50 degrees C optimum for the free enzyme. These differences are understandable, since the mass transfer rates of substrate and product within the pores of the gel matrix are controlled mainly by the temperature, so therefore it is the temperature which governs the overall activity of the immobilized enzyme system. It was also found that when the operational temperature in the packed bed reactor was cycled between temperatures below (35 degrees C) and above (45 degrees C) the copolymer gel LCST, the activity of the immobilized enzyme almost fully recovered after each cycle. In fact, the enzyme-gel system exhibited a complete "shut-off" in activity at 50 degrees C which was the temperature where the free enzyme showed its maximum activity. The thermal cycling operation of LCST enzyme-gel beads can be used to enhance overall activity and productivity of a packed bed reactor, when compared to isothermal operation of this reactor. This is due to the thermally induced "pumping" which enhances mass transfer rates of substrate in and product out of the gel beads. PMID:2105961

  18. Mechanical characterization of a bifunctional Tetronic hydrogel adhesive for soft tissues.

    PubMed

    Sanders, Lindsey; Stone, Roland; Webb, Kenneth; Mefford, Thompson; Nagatomi, Jiro

    2015-03-01

    Although a number of tissue adhesives and sealants for surgical use are currently available, attaining a useful balance in high strength, high compliance, and low swelling has proven difficult. Recent studies have demonstrated that a four-arm poly(propylene oxide)-poly(ethylene oxide) block copolymer, Tetronic, can be chemically modified to form a hydrogel tissue adhesive (Cho et al., Acta Biomater 2012;8:2223-2232; Barrett et al., Adv Health Mater 2012;1-11; Balakrishnan, Evaluating mechanical performance of hydrogel-based adhesives for soft tissue applications. Clemson University, All Theses, Paper 1574: Tiger Prints; 2013). Building on the success of these studies, this study explored bifunctionalization of Tetronic with acrylates for chemical crosslinking of the hydrogel and N-hydroxysuccinimide (NHS) for reaction with tissue amines. The adhesive bond strengths of various uni and bifunctional Tetronic blends (T1107 ACR: T1107 ACR/NHS) determined by lap shear testing ranged between 8 and 74 kPa, with the 75:25 (T1107 ACR: T1107 ACR/NHS) blend displaying the highest value. These results indicated that addition of NHS led to improvement of tissue bond strength over acrylation alone. Furthermore, ex vivo pressure tests using the rat bladder demonstrated that the bifunctional Tetronic adhesive exhibited high compliance and maintained pressures under hundreds of filling and emptying cycles. Together, the results of this study provided evidence that the bifunctional Tetronic adhesive with a proper blend ratio may be used to achieve an accurate balance in bulk and tissue bond strengths, as well as the compliance and durability for soft tissue such as the bladder. PMID:25111445

  19. Development and characterization of a novel hydrogel adhesive for soft tissue applications

    NASA Astrophysics Data System (ADS)

    Sanders, Lindsey Kennedy

    With laparoscopic and robotic surgical techniques advancing, the need for an injectable surgical adhesive is growing. To be effective, surgical adhesives for internal organs require bulk strength and compliance to avoid rips and tears, and adhesive strength to avoid leakage at the application site, while not hindering the natural healing process. Although a number of tissue adhesives and sealants approved by the FDA for surgical use are currently available, attaining a useful balance in all of these qualities has proven difficult, particularly when considering applications involving highly expandable tissue, such as bladder and lung. The long-term goal of this project is to develop a hydrogel-based tissue adhesive that provides proper mechanical properties to eliminate the need for sutures in various soft tissue applications. Tetronic (BASF), a 4-arm poly(propylene oxide)-poly(ethylene oxide) (PPO-PEO) block copolymer, has been selected as the base material for the adhesive hydrogel system. Solutions of Tetronic T1107 can support reverse thermal gelation at physiological temperatures, which can be combined with covalent crosslinking to achieve a "tandem gelation" process making it ideal for use as a tissue adhesive. The objective of this doctoral thesis research is to improve the performance of the hydrogel based tissue adhesive developed previously by Cho and co-workers by applying a multi-functionalization of Tetronic. Specifically, this research aimed to improve bonding strength of Tetronic tissue adhesive using bi-functional modification, incorporate hemostatic function to the bi-functional Tetronic hydrogel, and evaluate the safety of bi-functional Tetronic tissue adhesive both in vitro and in vivo. In summary, we have developed a fast-curing, mechanically strong hemostatic tissue adhesive that can control blood loss in wet conditions during wound treatment applications (bladder, liver and muscle). Specifically, the bi-functional Tetronic adhesive (TAS) with a

  20. New Synthesis Route of Hydrogel through A Bioinspired Supramolecular Approach: Gelation, Binding Interaction, and in Vitro Dressing.

    PubMed

    Cheng, Chieh; Tang, Meng-Che; Wu, Chung-Shu; Simon, Turibius; Ko, Fu-Hsiang

    2015-09-01

    Peptide-based supramolecular hydrogels have been comprehensively investigated in biomaterial applications because of their unique bioactivity, biofunctionality, and biocompatible features. However, the presence of organic building blocks in peptide-based hydrogels often results in low mechanical stability. To expand their practical use and range of applications, it is necessary to develop the tool kit available to prepare bioinspired, peptide-based supramolecular hydrogels with improved mechanical stability. In this paper, we present an innovative electrostatic and cross-linking approach in which naphthyl-Phe-Phe-Cys (NapFFC) oligopeptides are combined with gold nanoparticles (AuNPs) and calcium ions (Ca(2+)) to produce peptide-based supramolecular hydrogels. We further investigate the interactions among NapFFC, AuNPs and Ca(2+) by microscopy. The morphology of the nanofibrous network constructions and the binding forces exhibited from the hydrogel demonstrated that the combination of two mechanisms successfully enhanced the mechanical stability through the formation of a densely entangled fibrous network of peptide multimers that is attributed to the AuNP linkage and Ca(2+)-induced agglomeration. UV-vis spectrophotometry and fluorescence analysis were also used to demonstrate the enhanced stability of the hydrogel under various conditions such as thermal, solvent erosion, pH value and sonication. All results indicate that the presence of AuNPs and Ca(2+) can strengthen the prepared hydrogel by more than doubling the diameter of NapFFC nanofibers, enabling the formation of stronger frameworks and slowing the release of components. Further experiments confirmed that HeLa cells can grow on the bioinspired NapFFC-AuNP hydrogel and exhibit high cell viability and that these cells were killed on contact with a hydrogel containing a drug. Our peptide-based supramolecular hydrogels prepared from the observed electrostatic and cross-linking mechanisn exhibited a

  1. Organic hydrogels as potential sorbent materials for water purification

    NASA Astrophysics Data System (ADS)

    Linardatos, George; Bekiari, Vlasoula; Bokias, George

    2014-05-01

    the adsorption efficiency is the charge content of the hydrogel x, as well as the pH of the aqueous solution, since acrylic acid is a weak acid. ACKNOWLEDGMENTS. This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Archimedes III. Investing in knowledge society through the European Social Fund; research project Archimedes III: "Synthesis and characterization of novel nanostructured materials and study of their use as water purification systems".

  2. Preparation and characterization of nanosized P(NIPAM-MBA) hydrogel particles and adsorption of bovine serum albumin on their surface

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoli; Gu, Xiangling; Zhang, Lina; Kong, Xiang-Zheng

    2012-09-01

    Thermosensitive polymer hydrogel particles with size varying from 480 to 620 nm were prepared through precipitation copolymerization of N-isopropylacrylamide with N,N'-methylenebisacrylamide (MBA) in water with ammonium persulfate as the initiator. Only polymer hydrogels without any coagula were obtained when MBA concentration in the monomer mixture was kept between 2.5 and 10.0 wt%; with increased MBA concentration, the monomer conversion was enhanced, the size of the hydrogels was increased, and their shrinking was lessened when heated from 25°C to 40°C. Bovine serum albumin adsorption on the surface of the hydrogels of different MBA content was measured at different pH levels and under different temperatures. The results demonstrated that the adsorption of the protein on the hydrogels could be controlled by adjusting the pH, the temperature of adsorption, and the crosslinking in the hydrogels. The results were interpreted, and the mechanisms of the polymerization were proposed.

  3. Cellulose nanofibers reinforced sodium alginate-polyvinyl alcohol hydrogels: Core-shell structure formation and property characterization.

    PubMed

    Yue, Yiying; Han, Jingquan; Han, Guangping; French, Alfred D; Qi, Yadong; Wu, Qinglin

    2016-08-20

    Core-shell structured hydrogels consisting of a flexible interpenetrating polymer network (IPN) core and a rigid semi-IPN shell were prepared through chemical crosslinking of polyvinyl alcohol (PVA) and sodium alginate (SA) with Ca(2+) and glutaraldehyde. Short cellulose nanofibers (CNFs) extracted from energycane bagasse were incorporated in the hydrogel. The shell was micro-porous and the core was macro-porous. The hydrogels could be used in multiple adsorption-desorption cycles for dyes, and the maximum methyl blue adsorption capacity had a 10% increase after incorporating CNFs. The homogeneous distribution of CNFs in PVA-SA matrix generated additional hydrogen bonds among the polymer molecular chains, resulting in enhanced density, viscoelasticity, and mechanical strength for the hydrogel. Specifically, the compressive strength of the hydrogel reached 79.5kPa, 3.2 times higher than that of the neat hydrogel. PMID:27178920

  4. Synthesis and characterization of actinide nitrides

    SciTech Connect

    Jaques, Brian; Butt, Darryl P.; Marx, Brian M.; Hamdy, A.S.; Osterberg, Daniel; Balfour, Gordon

    2007-07-01

    A carbothermic reduction of the metal oxides in a hydrogen/nitrogen mixed gas stream prior to nitriding in a nitrogen gas stream was used to synthesize uranium nitride at 1500 deg. C, cerium nitride at 1400 deg. C, and dysprosium nitride at 1500 deg. C. Cerium nitride and dysprosium nitride were also synthesized via hydriding and nitriding the metal shavings at 900 deg. C and 1500 deg. C, respectively. Also, a novel ball-milling synthesis route was used to produce cerium nitride and dysprosium nitride from the metal shavings at room temperature. Dysprosium nitride was also produced by reacting the metal shavings in a high purity nitrogen gas stream at 1300 deg. C. All materials were characterized by phase analysis via X-ray diffraction. Only the high purity materials were further analyzed via chemical analysis to characterize the trace oxygen concentration. (authors)

  5. Biodegradable and semi-biodegradable composite hydrogels as bone substitutes: morphology and mechanical characterization.

    PubMed

    Sanginario, V; Ginebra, M P; Tanner, K E; Planell, J A; Ambrosio, L

    2006-05-01

    Biodegradable and semi-biodegradable composite hydrogels are proposed as bone substitutes. They consist of an hydrophilic biodegradable polymer (HYAFF 11) as matrix and two ceramic powders (alpha-TCP and HA) as reinforcement. Both components of these composites have been of great interest in biomedical applications due to their excellent biocompatibility and tissue interactions, however they have never been investigated as bone substitute composites. Morphological and mechanical analysis have shown that the two fillers behave in a very different way. In the HYAFF 11/alpha-TCP composite, alpha-TCP is able to hydrolyze in contact with water while in the HYAFF 11 matrix. As a result, the composite sets and hardens, and entangled CDHA crystals are formed in the hydrogel phase and increases in the mechanical properties are obtained. In the HYAFF11/HA composite the ceramic reinforcement acts as inert phase leading to lower mechanical properties. Both mechanical properties and microstructure analysis have demonstrated the possibility to design hydrophilic biodegradable composite structures for bone tissue substitution applications. PMID:16688585

  6. Mechanical Characterization of a Bi-functional Tetronic Hydrogel Adhesive for Soft Tissues

    PubMed Central

    Sanders, Lindsey; Stone, Roland; Webb, C. Kenneth; Mefford, O. Thompson; Nagatomi, Jiro

    2014-01-01

    Although a number of tissue adhesives and sealants for surgical use are currently available, attaining a useful balance in high strength, high compliance, and low swelling has proven difficult. Recent studies have demonstrated that a 4-arm poly(propylene oxide)-poly(ethylene oxide) (PPO-PEO) block copolymer, Tetronic, can be chemically modified to form a hydrogel tissue adhesive21–23. Building on the success of these studies, the present study explored bi-functionalization of Tetronic with acrylates for chemical crosslinking of the hydrogel and N-hydroxysuccinimide (NHS) for reaction with tissue amines. The adhesive bond strengths of various uni- and bi-functional Tetronic blends (T1107 ACR: T1107 ACR/NHS) determined by lap shear testing ranged between 8 and 74 kPa, with the 75:25 (T1107 ACR: T1107 ACR/NHS) blend displaying the highest value. These results indicated that addition of NHS led to improvement of tissue bond strength over acrylation alone Furthermore, ex vivo pressure tests using the rat bladder demonstrated that the bi-functional Tetronic adhesive exhibited high compliance and maintained pressures under hundreds of filling and emptying cycles. Together, the results of the present study provided evidence that the bi-functional Tetronic adhesive with a proper blend ratio may be used to achieve an accurate balance in bulk and tissue bond strengths, as well as the compliance and durability for soft tissue such as the bladder. PMID:25111445

  7. Preparation, characterization, and biocompatibility evaluation of poly(Nɛ-acryloyl-L-lysine)/hyaluronic acid interpenetrating network hydrogels.

    PubMed

    Cui, Ning; Qian, Junmin; Xu, Weijun; Xu, Minghui; Zhao, Na; Liu, Ting; Wang, Hongjie

    2016-01-20

    In the present study, poly(Nɛ-acryloyl-L-lysine)/hyaluronic acid (pLysAAm/HA) interpenetrating network (IPN) hydrogels were successfully fabricated through the combination of hydrazone bond crosslinking and photo-crosslinking reactions. The HA hydrogel network was first synthesized from 3,3'-dithiodipropionate hydrazide-modified HA and polyethylene glycol dilevulinate by hydrazone bond crosslinking. The pLysAAm hydrogel network was prepared from Nɛ-acryloyl-L-lysine and N,N'-bis(acryloyl)-(L)-cystine by photo-crosslinking. The resultant pLysAAm/HA hydrogels had a good shape recovery property after loading and unloading for 1.5 cycles (up to 90%) and displayed a highly porous microstructure. Their compressive moduli were at least 5 times higher than that of HA hydrogels. The pLysAAm/HA hydrogels had an equilibrium swelling ratio of up to 37.9 and displayed a glutathione-responsive degradation behavior. The results from in vitro biocompatibility evaluation with pre-osteoblasts MC3T3-E1 cells revealed that the pLysAAm/HA hydrogels could support cell viability and proliferation. Hematoxylin and eosin staining indicated that the pLysAAm/HA hydrogels allowed cell and tissue infiltration, confirming their good in vivo biocompatibility. Therefore, the novel pLysAAm/HA IPN hydrogels have great potential for bone tissue engineering applications. PMID:26572442

  8. Design, synthesis, and characterization of new phosphazene related materials, and study the structure property correlations

    NASA Astrophysics Data System (ADS)

    Tian, Zhicheng

    The work described in this thesis is divided into three major parts, and all of which involve the exploration of the chemistry of polyphosphazenes. The first part (chapters 2 and 3) of my research is synthesis and study polyphoshazenes for biomedical applications, including polymer drug conjugates and injectable hydrogels for drug or biomolecule delivery. The second part (chapters 4 and 5) focuses on the synthesis of several organic/inorganic hybrid polymeric structures, such as diblock, star, brush and palm tree copolymers using living cationic polymerization and atom transfer radical polymerization techniques. The last part (chapters 6 and 7) is about exploratory synthesis of new polymeric structures with fluorinated side groups or cycloaliphatic side groups, and the study of new structure property relationships. Chapter 1 is an outline of the fundamental concepts for polymeric materials, as such the history, important definitions, and some introductory material for to polymer chemistry and physics. The chemistry and applications of phopshazenes is also briefly described. Chapter 2 is a description of the design, synthesis, and characterization of development of a new class of polymer drug conjugate materials based on biodegradable polyphosphazenes and antibiotics. Poly(dichlorophosphazene), synthesized by a thermal ring opening polymerization, was reacted with up to 25 mol% of ciprofloxacin or norfloxacin and three different amino acid esters (glycine, alanine, or phenylalanine) as cosubstituents via macromolecular substitutions. Nano/microfibers of several selected polymers were prepared by an electrospinning technique. Chapter 3 is concerned with the development of a class of injectable and biodegradable hydrogels based on water-soluble poly(organophosphazenes) containing oligo(ethylene glycol) methyl ethers and glycine ethyl esters. The hydrogels can be obtained by mixing alpha-cyclodextrin aqueous solution and poly(organophosphazenes) aqueous solution in

  9. Characterization and cytocompatibility of thermosensitive hydrogel embedded with chitosan nanoparticles for delivery of bone morphogenetic protein-2 plasmid DNA.

    PubMed

    Li, Dan-Dan; Pan, Jian-Feng; Ji, Qiu-Xia; Yu, Xin-Bo; Liu, Ling-Shuang; Li, Hui; Jiao, Xiao-Ju; Wang, Lei

    2016-08-01

    A novel injectable chitosan thermosensitive hydrogel was designed as a target multi-effect scaffold for endogenous repair of the periodontium. The hydrogel complex was designed by embedding chitosan nanoparticles (CSn) loaded with bone morphogenetic protein-2 plasmid DNA (pDNA-BMP2) into a chitosan (CS)-based hydrogel with α,β-glycerophosphate (α,β-GP), termed CS/CSn(pDNA-BMP2)-GP. Characterization, the in vitro release profile for pDNA-BMP2, and cytocompatibility to human periodontal ligament cells (HPDLCs), were then conducted. The average diameter of the CSn(pDNA-BMP2) was 270.1 nm with a polydispersity index (PDI) of 0.486 and zeta potential of +27.0 mv. A DNase I protection assay showed that CSn could protect the pDNA-BMP2 from nuclease degradation. Encapsulation efficiency and loading capacity of CSn(pDNA-BMP2) were more than 80 and 30 %, respectively. The sol-gel transition time was only 3 min when CSn(pDNA-BMP2) was added into the CS/α,β-GP system. Scanning electron microscopy showed that CSn(pDNA-BMP2) was randomly dispersed in a network with regular holes and a porous structure. Weighting method showed the swelling ratio and degradation was faster in medium of pH 4.0 than pH 6.8. An in vitro pDNA-BMP2 release test showed that the cumulative release rate of pDNA-BMP2 was much slower from CS/CSn-GP than from CSn in identical release media. In release media with different pH, pDNA-BMP2 release was much slower at pH 6.8 than at pH 4.0. Three-dimensional culture with HPDLCs showed good cell proliferation and the Cell-Counting Kit-8 assay indicated improved cell growth with the addition of CSn(pDNA-BMP2) to CS/α,β-GP. In summary, the CS/CSn(pDNA-BMP2)-GP complex system exhibited excellent biological properties and cytocompatibility, indicating great potential as a gene delivery carrier and tissue regeneration scaffold for endogenous repair of the periodontium. PMID:27405491

  10. Biopharmaceutical profile of hydrogels containing pranoprofen-loaded PLGA nanoparticles for skin administration: In vitro, ex vivo and in vivo characterization.

    PubMed

    Abrego, Guadalupe; Alvarado, Helen; Souto, Eliana B; Guevara, Bessy; Bellowa, Lyda Halbaut; Garduño, Maria Luisa; Garcia, María Luisa; Calpena, Ana C

    2016-03-30

    Pranoprofen (PF)-loaded nanoparticles (PF-F1NPs and PF-F2NPs) have been formulated into blank hydrogels (HG_PF-F1NPs and HG_PF-F1NPs) or into hydrogels composed of 3% azone (HG_PF-F1NPs-Azone and HG_PF-F2NPs-Azone), as innovative strategy to improve the biopharmaceutical profile of the selected non-steroidal anti-inflammatory drug (Pranoprofen, PF) for topical application. The purpose of this approach has been to increase the contact of PF with the skin, improve its retention in deeper layers, thus enhancing its anti-inflammatory and analgesic effects. The physicochemical characterization of the developed hydrogels showed a non-Newtonian behaviour, typical of semi-solid formulations for skin administration, with sustained release profile. The results obtained from ex vivo skin human permeation and in vivo anti-inflammatory efficacy studies suggest that topical application of HG_PF-F2NPs has been more effective in the treatment of oedema on the skin' surface in comparison to other hydrogels. No signs of skin irritancy have been detected for all the semi-solid formulations containing 0% or 3% azone. PMID:26844786

  11. Synthesis and characterization of a new zeolite of the offretite type

    SciTech Connect

    Occelli, M.L.; Perrotta, A.J.

    1982-03-01

    Offretite is an hexagonal zeolite first discovered by Professor Gonnard in 1890 in amygdaloidal basalt at Mount Semiouse near Montbreson, France. Offretite has been synthesized by Rubin and Aiello and Barrer from aluminosilicate hydrogels in a TMA (tetramethylammonium)-KOH-NaOH mixed base system. Aiello and Barrer noted that this zeolite can be grown from gels in the presence of KOH-TMAOH but not in the presence of NaOH-TMAOH. Sand has shown that offretite can be synthesized without TMA-OH from NaOH-KOH solutions. The synthesis of offretite crystals always included the presence of potassium ions until fairly recently when Barrer and Sieber were able to crystallize this zeolite from a LiOH-CsOH-TMAOH containing hydrogel. It is the purpose of this paper to describe the Perrotta synthesis of a new zeolite of the offretite type crystallized from a potassium free, aluminosilicate hydrogel in the presence of Rb-TMA ions.

  12. Tools for Characterizing Bacterial Protein Synthesis Inhibitors

    PubMed Central

    Orelle, Cédric; Carlson, Skylar; Kaushal, Bindiya; Almutairi, Mashal M.; Liu, Haipeng; Ochabowicz, Anna; Quan, Selwyn; Pham, Van Cuong; Squires, Catherine L.; Murphy, Brian T.

    2013-01-01

    Many antibiotics inhibit the growth of sensitive bacteria by interfering with ribosome function. However, discovery of new protein synthesis inhibitors is curbed by the lack of facile techniques capable of readily identifying antibiotic target sites and modes of action. Furthermore, the frequent rediscovery of known antibiotic scaffolds, especially in natural product extracts, is time-consuming and expensive and diverts resources that could be used toward the isolation of novel lead molecules. In order to avoid these pitfalls and improve the process of dereplication of chemically complex extracts, we designed a two-pronged approach for the characterization of inhibitors of protein synthesis (ChIPS) that is suitable for the rapid identification of the site and mode of action on the bacterial ribosome. First, we engineered antibiotic-hypersensitive Escherichia coli strains that contain only one rRNA operon. These strains are used for the rapid isolation of resistance mutants in which rRNA mutations identify the site of the antibiotic action. Second, we show that patterns of drug-induced ribosome stalling on mRNA, monitored by primer extension, can be used to elucidate the mode of antibiotic action. These analyses can be performed within a few days and provide a rapid and efficient approach for identifying the site and mode of action of translation inhibitors targeting the bacterial ribosome. Both techniques were validated using a bacterial strain whose culture extract, composed of unknown metabolites, exhibited protein synthesis inhibitory activity; we were able to rapidly detect the presence of the antibiotic chloramphenicol. PMID:24041905

  13. Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

    SciTech Connect

    Michael Duane Determan

    2005-12-17

    The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi

  14. Green synthesis and characterization of graphene nanosheets

    SciTech Connect

    Tavakoli, Farnosh; Salavati-Niasari, Masoud; Badiei, Alireza; Mohandes, Fatemeh

    2015-03-15

    Highlights: • For the first time, we have synthesized graphene nanosheets in the presence of pomegranate juice. • Here pomegranate juice was used not only as reductant but also as capping agent. • FT-IR, XRD, SEM, EDS and TEM were used to characterize the samples. • According to TEM image, graphene nanosheet is individually exfoliated after stirring for 24 h. • As shown in the TEM image, graphene monolayer is obtained. - Abstract: For the first time, we have successfully synthesized graphene nanosheets in the presence of pomegranate juice. In this approach, pomegranate juice was used not only as reductant but also as capping agent to form graphene nanosheets. At first, the improved Hummer method to oxidize graphite for the synthesis of graphene oxide (GO) was applied, and then the as-produced graphene oxide was reduced by pomegranate juice to form graphene nanosheets. Fourier transformed infrared (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and raman were used to characterize the samples. The results obtained from the characterization techniques proved high purity of the final products.

  15. Synthesis and Characterization of Modified Phenylethynyl Imides

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Chang, A. C.

    1998-01-01

    As an ongoing effort to develop structural adhesives for high-performance aerospace applications, recent work has focused on phenylethynyl terminated imide (PETI) oligomers. The work reported herein involves the synthesis and characterization of a series of phenylethynyl containing oligomers designated LARC(TM) MPEI (modified phenylethynyl imide). These oligomers presumably contain mixtures of linear, branched and star-shaped molecules. The fully imidized polymers exhibited minimum melt viscosities as low as 600 poise at 335 C, significantly lower than equivalent molecular weight linear materials. Ti/Ti lap shear specimens processed at 288 C under 15 psi showed tensile shear strengths as high as approx. 6000 psi and 5200 psi at ambient temperature and 177 C respectively. The chemistry and properties of these new MPEIs are presented and compared with an optimized linear PETI, LARC(TM)PETI-5.

  16. Synthesis and characterization of functionalized magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Biswal, Dipti; Peeples, Brianna N.; Spence, Destiny D.; Peeples, Caryn; Bell, Crystal N.; Pradhan, A. K.

    2012-04-01

    Magnetic nanoparticles have been used in a wide array of industrial and biomedical applications due to their unique properties at the nanoscale level. They are extensively used in magnetic resonance imaging (MRI), magnetic hyperthermia treatment, drug delivery, and in assays for biological separations. Furthermore, superparamagnetic nanoparticles are of large interest for in vivo applications. However, these unmodified nanoparticles aggregate and consequently lose their superparamagnetic behaviors, due to high surface to volume ratio and strong dipole to dipole interaction. For these reasons, surface coating is necessary for the enhancement and effectiveness of magnetic nanoparticles to be used in various applications. In addition to providing increased stability to the nanoparticles in different solvents or media, stabilizers such as surfactants, organic/inorganic molecules, polymer and co-polymers are employed as surface coatings, which yield magnetically responsive systems. In this work we present the synthesis and magnetic characterization of Fe3O4 nanoparticles coated with 3-aminopropyltriethoxy silane (APS) and citric acid. The particles magnetic hysteresis was measured by a superconducting quantum interference device (SQUID) magnetometer with an in-plane magnetic field. The uncoated and coated magnetic nanoparticles were characterized by using fourier transform infrared (FTIR), UV-vis, X-ray diffraction, transmission electron microscopy, and thermo-gravimetric analysis.

  17. Synthesis of oxidized glycerol monooleate-chitosan polymer and its hydrogel formation for sustained release of trimetazidine hydrochloride.

    PubMed

    Zhang, Jianjun; Fu, Meng; Zhang, Minyan; Xu, Liang; Gao, Yuan

    2014-04-25

    In this paper, a lipid material glycerol monooleate was used as the starting material to synthesize the oxidized glycerol monooleate (OGMO). OGMO was subsequently linked to chitosan (CS) via imine bonds (-C=N-) to obtain a new chitosan-based polymer (OGMO-CS), which can form hydrogels rapidly in aqueous media. Scanning electron microscopy, swelling behavior studies and degradation kinetics studies were performed to demonstrate the effect of this synthetic modification on the hydrogels formation of chitosan network and in vitro drug release. The effects of OGMO-CS type, dry hydrogels percentage, release media and drug loading on the sustained release of the model drug trimetazidine hydrochloride were evaluated. The release profiles of the hydrogels could be described by the Peppas-Sahlin mechanism, a combination of Fickian diffusion and Case-II relaxation. Based on the fact that numerous pharmaceutical lipids are available, the present study may pave the way for other lipids to be employed as modifiers of chitosan for more innovative chitosan derivatives with versatile properties and pharmaceutical applications. PMID:24508554

  18. Characterization of Free Surface-Bound and Entrapped Water Environments in Poly(N-Isopropyl Acrylamide) Hydrogels via 1H HRMAS PFG NMR Spectroscopy

    DOE PAGESBeta

    Alam, Todd Michael; Childress, Kimberly Kay; Pastoor, Kevin; Rice, Charles

    2014-09-19

    We found that different water environments in poly(N-isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using 1H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro-gels. For photo-initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spin R2 relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. Furthermore, by combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self-diffusion rate for these differentmore » water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described.« less

  19. Characterization of Free Surface-Bound and Entrapped Water Environments in Poly(N-Isopropyl Acrylamide) Hydrogels via 1H HRMAS PFG NMR Spectroscopy

    SciTech Connect

    Alam, Todd Michael; Childress, Kimberly Kay; Pastoor, Kevin; Rice, Charles

    2014-09-19

    We found that different water environments in poly(N-isopropyl acrylamide) (PNIPAAm) hydrogels are identified and characterized using 1H high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR). Local water environments corresponding to a “free” highly mobile species, along with waters showing restricted dynamics are resolved in these swollen hydro-gels. For photo-initiated polymerized PNIPAAm gels, an additional entrapped water species is observed. Spin–spin R2 relaxation experiments support the argument of reduced mobility in the restricted and entrapped water species. Furthermore, by combining pulse field gradient techniques with HRMAS NMR it is possible to directly measure the self-diffusion rate for these different water environments. The behavior of the heterogeneous water environments through the lower critical solution temperature transition is described.

  20. Synthesis, characterization and optical applications of nanomaterials

    NASA Astrophysics Data System (ADS)

    Xu, Fen

    Nanomaterials have been studied extensively due to their potential application in electronics, photonics and nanodevices. There are a wide variety of methods developed to create the nano-scale materials. Chemical colloidal synthesis is the way most used since it is reproducible and high efficiency. Nanoparticles lie at the heart of nanoscience for their novel electronic, magnetic and optical properties. In this dissertation, there are two parts where researches have been performed based on the synthesis of metal and semiconductor nanoparticles. In part I, Semiconductor type-II core-shell quantum dots (QDs) ZnO-CdS have been synthesized by chemical colloidal method which was carried out in a two-step process. We initially synthesized ZnO core nanoparticles and overcoat them with CdS shell. UV-Visible spectra, photoluminescence spectra (PL), high resolution TEM images and X-ray microanalysis for composition studies of the core-shell nanoparticles were characterized. PL lifetime measurements showed this type-II ZnO-CdS core-shell QDs presented extended exciton lifetime due to the spatial separation of electrons and holes between the core and the shell, which opens various useful applications in biosensors and photovoltaic devices. In part II, normal Raman (NR) and surface enhanced Raman scattering (SERS) spectra of 3-hydroxyflavone (3-HF) have been measured. The SERS spectra were obtained both on a Ag electrode surface and on Ag colloidal nanoparticles. The experimental results support the DFT geometry calculations, which show that an adatom site at the vertex of Ag20 cluster binding with the 3-HF molecular plane tilted at an angle of about 53° to the surface is a low-energy structure. This is consistent with the enhancement of in-plane vibrational modes. Furthermore, the effect of fluence level on the discoloration of marble surfaces after the removal of the encrustation by 355 nm laser pulses was comparatively studied. Considering the thermochemical reaction

  1. Recent advances in green hydrogels from lignin: a review.

    PubMed

    Thakur, Vijay Kumar; Thakur, Manju Kumari

    2015-01-01

    Recently, biorenewable polymers from different natural resources have attracted a greater attention of the research community for different applications starting from biomedical to automotive. Lignin is the second most abundant non-food biomass next to cellulose in the category of biorenewable polymers and is abundantly available as byproduct of several industries involved in paper making, ethanol production, etc. The development of various green materials from lignin, which is most often considered as waste, is therefore of prime interest from environmental and economic points of view. Over the last few years, little studies have been made into the use of lignin as an indispensable component in the hydrogels. This article provides an overview of the research work carried out in the last few years on lignin based hydrogels. This article comprehensively reviews the potential efficacy of lignin in biopolymer based green hydrogels with particular emphasis on synthesis, characterization and applications. In this article, several examples of hydrogels synthesized using different types of lignin are discussed to illustrate the state of the art in the use of lignin. PMID:25304747

  2. Preparation and characterization of a novel sodium alginate incorporated self-assembled Fmoc-FF composite hydrogel.

    PubMed

    Gong, Xiao; Branford-White, Christopher; Tao, Lei; Li, Shubai; Quan, Jing; Nie, Huali; Zhu, Limin

    2016-01-01

    Dipeptides and their derivatives have attracted tremendous attention owning to their excellent abilities of self-assemble assembling into various structures which have great potentials for applications in biology and/or nanotechnology. In the present study, we dedicate to fabricate a rigid and structure controllable Fmoc-FF/SA composite hydrogel. We found that the modified dipeptide, fluorenyl-9-methoxycarbonyl (Fmoc)-diphenylalanine (Phe-Phe) can self-assemble into rigid hydrogels with structures of nanowires, layered thin films or honeycombs as the change of sodium alginate (SA) concentration. Meanwhile, CD-spectroscopy demonstrated that SA appeared to control the process, but it did not change the arrangement of the Fmoc-FF peptide. Our results demonstrated that the formed hydrogel showed physical and chemical stability as well as possessing good biocompatibility. Rheological measurements showed that the addition of SA could improve the stability of the hydrogel. Cell viability assay revealed that the Fmoc-FF and Fmoc-FF/SA hydrogels are both beneficial for cell proliferation in-vitro. Our results indicated that the fabricated Fmoc-FF/SA composite hydrogels could be used in tissue engineering and drug delivery in the future. PMID:26478335

  3. Preparation and characterization of nanosized P(NIPAM-MBA) hydrogel particles and adsorption of bovine serum albumin on their surface

    PubMed Central

    2012-01-01

    Thermosensitive polymer hydrogel particles with size varying from 480 to 620 nm were prepared through precipitation copolymerization of N-isopropylacrylamide with N,N′-methylenebisacrylamide (MBA) in water with ammonium persulfate as the initiator. Only polymer hydrogels without any coagula were obtained when MBA concentration in the monomer mixture was kept between 2.5 and 10.0 wt%; with increased MBA concentration, the monomer conversion was enhanced, the size of the hydrogels was increased, and their shrinking was lessened when heated from 25°C to 40°C. Bovine serum albumin adsorption on the surface of the hydrogels of different MBA content was measured at different pH levels and under different temperatures. The results demonstrated that the adsorption of the protein on the hydrogels could be controlled by adjusting the pH, the temperature of adsorption, and the crosslinking in the hydrogels. The results were interpreted, and the mechanisms of the polymerization were proposed. PMID:23006588

  4. Synthesis and characterization of ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Tsai, Poching

    Ferromagnetic nanocrystals with shape anisotropy have drawn great attention in the past decades because of their unique magnetic properties and for their potential applications in ultra-high-density magnetic recording media, exchange-coupled nanocomposite magnets and related nanodevices. In this thesis, synthesis and characterixation of ferromagnetic CoNi and CoFe nanowires are reported. CoNi nanocrystals with different size, shape and composition were successfully synthesized via a catalyst chemical solution method. It was found out that the structure and morphology can be controlled by altering the NaOH concentration, and the elongation of the nanowires can be adjusted by changing surfactants ratio and catalyst amount. Unlike the CoNi, CoFe nanocrystals were prepared by a non-catalyst chemistry solution method. The particle size and shape are controlled by varying parameters such as solvent amount, surfactant ratio, reducing agent and heating rate. Morphological, structural, and compositional characterizations of the nanoparticles were performed by using Transmission Electron Microscopy (TEM), high resolution TEM (HRTEM), and X-Ray Diffractometer (XRD). Magnetic properties of nanoparticles of different size were studied by Alternating Gradiant Magnetometer (AGM).

  5. : Synthesis, Characterization, and Enhanced Photocatalytic Activity

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Fu, Feng; Li, Wenhong

    2014-12-01

    3D hierarchical microspheres of Cu-loaded Bi2WO6 are successfully prepared by the hydrothermal synthesis method on a large scale. The as-prepared samples are characterized by UV-Vis DRS, BET, XRD, XPS, and SEM. The results reveal that the light absorption of Cu-loaded Bi2WO6 has higher intensity in the visible range and a bathochromic shift of the absorption edge compared to that of pure Bi2WO6. The photocatalytic activity is evaluated by phenol removal from aqueous solution under visible-light irradiation. The results demonstrate that loaded Cu significantly enhances the photocatalytic activity of Bi2WO6, for the loaded Cu acts as the electron receptor on the surface of Bi2WO6, and inhibits the recombination of photogenerated electron-hole. The content of loaded Cu has an impact on the catalytic activity, and the 1.0 wt.% Cu-loaded Bi2WO6 exhibits the best photocatalytic activity in the degradation of phenol. Furthermore, the reaction kinetics of phenol removal from aqueous solution over the Cu-loaded Bi2WO6 is established by the way of the Langmuir-Hinshelwood model. The results indicate that the process of photodegradation of phenol on Cu-loaded Bi2WO6 match the Langmuir-Hinshelwood kinetic model.

  6. Synthesis and Characterization of Processable Polyaniline Salts

    NASA Astrophysics Data System (ADS)

    Gul, Salma; Shah, Anwar-ul-Haq Ali; Bilal, Salma

    2013-06-01

    Polyaniline (PANI) is one of the most promising candidates for possible technological applications. PANI has potential applications in batteries, anion exchanger, tissue engineering, inhibition of steel corrosion, fuel cell, sensors and so on. However, its insolubility in common organic solvents limits its range of applications. In the present study an attempt has been made to synthesize soluble polyaniline salt via inverse polymerization pathway using benzoyl peroxide as oxidant and dodecylbenzenesulfonic acid (DBSA) as dopant as well as a surfactant. A mixture of chloroform and 2-butanol was used as dispersion medium for the first time. The influence of synthesis parameters such as concentration of aniline, benzoyl peroxide and DBSA on the yield and other properties of the resulting PANI salt was studied. The synthesized PANI salt was found to be completely soluble in DMSO, DMF, chloroform and in a mixture of toluene and 2-propanol. The synthesized polymer salt was also characterized with cyclic voltam-metry, SEM, XRD, UV-Vis spectroscopy and viscosity measurements. TGA was used to analyze the thermal properties of synthesized polymer. The extent of doping of the PANI salt was determined from UV-Vis spectra and TGA analysis. The activation energy for the degradation of the polymer was calculated with the help of TGA.

  7. Chemically Cross-Linked Poly(acrylic-co-vinylsulfonic) Acid Hydrogel for the Delivery of Isosorbide Mononitrate

    PubMed Central

    Ansari, Mahvash; Khan, Ikram Ullah

    2013-01-01

    We report synthesis, characterization, and drug release attributes of a series of novel pH-sensitive poly(acrylic-co-vinylsulfonic) acid hydrogels. These hydrogels were prepared by employing free radical polymerization using ethylene glycol dimethacrylate (EGDMA) and benzyl peroxide (BPO) as cross-linker and initiator, respectively. Effect of acrylic acid (AA), polyvinylsulfonic acid (PVSA), and EGDMA on prepared hydrogels was investigated. All formulations showed higher swelling at high pHs and vice versa. Formulations containing higher content of AA and EGDMA show reduced swelling, but one with higher content of PVSA showed increased swelling. Hydrogel network was characterized by determining structural parameters and loaded with isosorbide mononitrate. FTIR confirmed absence of drug polymer interaction while DSC and TGA demonstrated molecular dispersion of drug in a thermally stable polymeric network. All the hydrogel formulations exhibited a pH dependent release of isosorbide mononitrate which was found to be directly proportional to pH of the medium and PVSA content and inversely proportional to the AA contents. Drug release data were fitted to various kinetics models. Results indicated that release of isosorbide mononitrate from poly(AA-co-VSA) hydrogels was non-Fickian and that the mechanism was diffusion-controlled. PMID:24250265

  8. Synthesis and Characterization of Compounds Related to Lisinopril

    PubMed Central

    Raghava Reddy, Ambati V.; Garaga, Srinivas; Takshinamoorthy, Chandiran; Naidu, Andra; Dandala, Ramesh

    2016-01-01

    Lisinopril is a drug of the angiotensin-converting enzyme (ACE) inhibitor class that is primarily used in the treatment of hypertension. During the scale-up of the lisinopril process, one unknown impurity was observed and is identified. The present work describes the origin, synthesis, characterization, and control of this impurity. This paper also describes the synthesis and characterization of three other impurities listed in the European Pharmacopoeia 8.4 (Impurity C, D, and F). PMID:27222603

  9. Synthesis and characterization of ceria nanomaterials

    NASA Astrophysics Data System (ADS)

    Cheong Ng, Nitzia

    Cerium dioxide or ceria, CeO2, has been widely used in industry as catalyst for automotive exhaust controls, chemical mechanical polishing (CMP) slurries, and high temperature fuel cells because of its unique metal oxide properties. This well-known rare metal oxide has high thermal stability, electrical conductivity and chemical diffusivity. Proper synthesis method requires knowledge of reaction temperature, concentration, and time effects on the synthesis. In this work, ceria nanomaterials were prepared via the hydrothermal method using a Teflon autoclave. Cerium nitrate solution was used as the source and three different precursors: NaOH, H2O 2, and NH4OH were used as the oxidizing agents. CeO 2 nanoplates, nanocubes and nanorods were produced and studied using transmission electron microscopy (TEM), BET specific surface area, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Through characterization, CeO2 nanomaterials showed the presence of mixed valence states (Ce3+ and Ce4+) through XPS spectra. Deconvolution was performed to investigate the ratio of Ce 3+/Ce4+ concentration in the synthesized CeO2 nanostructures. Nanocubes showed a higher Ce3+ concentration. CeO2 nanomaterials were found to be mesoporous. Nanoplates synthesized with H2O2, and NH4OH were found with surface areas of 95.11 m2/g and 62.07 m2/g, respectively. Nanorods and nanocubes showed surface areas of 16.77 m2/g and 16.55 m2/g, respectively. The prepared ceria nanoplates, nanocubes and nanorods had crystallite size in the range of 5--25 nm and pore size range of 7--15 nm. XRD spectra confirmed that the peaks were indexed to the cubic phase of CeO2 with fluorite structure and with an average lattice parameter, 5.407 A. Higher Ce3+ concentration and exposed surface of crystalline planes suggest that nanorods are better catalyst for CO oxidation and oxygen storage capacity (OSC).

  10. Characterization and adsorption properties of a lanthanum-loaded magnetic cationic hydrogel composite for fluoride removal.

    PubMed

    Dong, Shuoxun; Wang, Yili

    2016-01-01

    In this study, a novel lanthanum-loaded magnetic cationic hydrogel (MCH-La) was synthesized for fluoride adsorption from drinking water. The adsorption kinetics, isotherms, and effects of pH and co-existing anions on fluoride uptake by MCH-La were evaluated. FTIR, Raman and XPS were used to analyze the fluoride adsorption mechanism of MCH-La. Results showed that MCH-La had positive zeta potential values of 23.6-8.0 mV at pH 3.0-11.0, with the magnitude of saturation magnetization up to 10.3 emu/g. The fluoride adsorption kinetics by MCH-La fitted well with the fractal-like-pseudo-second-order model, and the adsorption capacity reached 93% of the ultimate adsorption capacity within the first 10 min. The maximum fluoride adsorption capacity for MCH-La was 136.78 mg F(-)/g at an equilibrium fluoride concentration of 29.3 mg/L and pH 7.0. Equilibrium adsorption data showed that the Sips model was more suitable than the Langmuir and Freundlich models. MCH-La still had more than 100 mg of F(-)/g adsorption capacity at a strongly alkaline solution (pH > 10). The adsorption process was highly pH-dependent, and the optimal adsorption was attained at pH 2.8-4.0, corresponding to ligand exchange, electrostatic interactions, and Lewis acid-base interactions. With the exception of both anions of HCO3(-) and SiO4(4-), Cl(-), NO3(-), and SO4(2-) did not evidently prevent fluoride removal by MCH-La at their real concentrations in natural groundwater. The fluoride adsorption capacity of the regenerated MCH-La approached 70% of the fresh MCH-La from the second to fifth recycles. FTIR and Raman spectra revealed that C-O and CO functional groups on MCH contributed to the fluoride adsorption, this finding was also confirmed by the XPS F 1s spectra. Deconvolution of C 1s spectra before and after fluoride adsorption indicated that the carboxyl, anhydride, and phenol groups of MCH were involved in the fluoride removal. PMID:26613180

  11. Poloxamer 407/188 binary thermosensitive hydrogels as delivery systems for infiltrative local anesthesia: Physico-chemical characterization and pharmacological evaluation.

    PubMed

    Akkari, Alessandra C S; Papini, Juliana Z Boava; Garcia, Gabriella K; Franco, Margareth K K Dias; Cavalcanti, Leide P; Gasperini, Antonio; Alkschbirs, Melissa Inger; Yokaichyia, Fabiano; de Paula, Eneida; Tófoli, Giovana R; de Araujo, Daniele R

    2016-11-01

    In this study, we reported the development and the physico-chemical characterization of poloxamer 407 (PL407) and poloxamer 188 (PL188) binary systems as hydrogels for delivering ropivacaine (RVC), as drug model, and investigate their use in infiltrative local anesthesia for applications on the treatment of post-operative pain. We studied drug-micelle interaction and micellization process by light scattering and differential scanning calorimetry (DSC), the sol-gel transition and hydrogel supramolecular structure by small-angle-X-ray scattering (SAXS) and morphological evaluation by Scanning Electron Microscopy (SEM). In addition, we have presented the investigation of drug release mechanisms, in vitro/in vivo toxic and analgesic effects. Micellar dimensions evaluation showed the formation of PL407-PL188 mixed micelles and the drug incorporation, as well as the DSC studies showed increased enthalpy values for micelles formation after addition of PL 188 and RVC, indicating changes on self-assembly and the mixed micelles formation evoked by drug incorporation. SAXS studies revealed that the phase organization in hexagonal structure was not affected by RVC insertion into the hydrogels, maintaining their supramolecular structure. SEM analysis showed similar patterns after RVC addition. The RVC release followed the Higuchi model, modulated by the PL final concentration and the insertion of PL 188 into the system. Furthermore, the association PL407-PL188 induced lower in vitro cytotoxic effects, increased the duration of analgesia, in a single-dose model study, without evoking in vivo inflammation signs after local injection. PMID:27524024

  12. Development and initial characterization of a chemically stabilized elastin-glycosaminoglycan-collagen composite shape-memory hydrogel for nucleus pulposus regeneration.

    PubMed

    Mercuri, Jeremy; Addington, Caroline; Pascal, Richard; Gill, Sanjitpal; Simionescu, Dan

    2014-12-01

    Nucleus pulposus (NP) is a resilient and hydrophilic tissue which plays a significant role in the biomechanical function of the intervertebral disc (IVD). Destruction of the NP extracellular matrix (ECM) is observed during the early stages of IVD degeneration. Herein, we describe the development and initial characterization of a novel biomaterial which attempts to recreate the resilient and hydrophilic nature of the NP via the construction of a chemically stabilized elastin-glycosaminoglycan-collagen (EGC) composite hydrogel. Results demonstrated that a resilient, hydrophilic hydrogel which displays a unique "shape-memory" sponge characteristic could be formed from a blend of soluble elastin aggregates, chondroitin-6-sulfate, hyaluronic acid and collagen following freeze-drying, stabilization with a carbodiimide and penta-galloyl glucose-based fixative, and subsequent partial degradation with glycosaminoglycan degrading enzymes. The resultant material exhibited the ability to restore its original dimensions and water content following multi-cycle mechanical compression and illustrated resistance to accelerated enzymatic degradation. Preliminary in vitro studies utilizing human adipose derived stem cells (hADSCs) demonstrated that the material was cytocompatible and supported differentiation towards an NP cell-like phenotype. In vivo biocompatibility studies illustrated host cell infiltration and evidence of active remodeling following 4 weeks of implantation. Feasibility studies demonstrated that the EGC hydrogel could be delivered via minimally invasive methods. PMID:24497431

  13. Controlled release of theophylline from poly(vinyl alcohol) hydrogels/porous silicon nanostructured systems

    NASA Astrophysics Data System (ADS)

    Cervantes-Rincón, N.; Medellín-Rodríguez, F. J.; Escobar-Barrios, V. A.; Palestino, G.

    2013-03-01

    In this research, hybrid hydrogels of poly (vinyl alcohol)/ porous silicon (PSi)/theophylline were synthesized by the freezing and thawing method. We evaluated the influence of the synthesis parameters of the poly (vinyl alcohol) (PVA) hydrogels in relation to their ability to swell and drug released. The parameters studied (using an experimental design developed in Minitab 16) were the polymer concentration, the freezing temperature and the number of freezing/thawing (f/t) cycles. Nanostructured porous silicon particles (NsPSi) and theophylline were added within the polymer matrix to increase the drug charge and the polymer mechanical strength. The hybrid hydrogels were characterized by Infrared Spectroscopy Fourier Transform (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC), drug delivery kinetics were engineered according to the desired drug release schedule.

  14. Preparation and characterization of a novel pH-sensitive hydrogel obtained from UV light-induced polymerization

    NASA Astrophysics Data System (ADS)

    Tian, R. Q.; Zhao, Y. G.; Cui, Y. Q.; Zhang, X. Y.; Zhang, J.; Liang, X. Y.; Shang, Q.

    2015-05-01

    The main aim of this study was to develop a novel pH-sensitive hydrogel prepared via an UV light-induced polymerization. Single-factor experiments were performed to acquire the optimum formula of final poly(MAA-co-PEGMA) hydrogel. Fourier transform infrared spectroscopy (FTIR) spectra were employed to confirm the successful preparation of the designed copolymers. Inner morphologies of the polymeric hydrogels were observed via an S-4800 scanning electron microscope (SEM). Swelling and reversible swelling-shrinking studies were carried out in different phosphate buffer solution (PBS) with various pH values. Drug-loading tests were performed with bovine serum albumin (BSA) as a model drug. The in vitro release profile was also investigated in PBS with the pH values of 1.2 and 7.4. FTIR spectra confirmed the preparation of the poly(MAA-co-PEGMA) copolymers without any residual monomers. The typical space grid structures were observed from the SEM photographs of hydrogels. The obtained hydrogel showed an excellent pH-sensibility and reversible swelling-shrinking property. The maximum drug-loading (40.9 %) was gained from the BSA concentration of 50.0 mg/mL. During the releasing process, only 5.8 ± 0.9 % of BSA was released at pH 1.2, but 82.1 ± 6.2 % was diffused at pH 7.4. These data suggested that such medicated hydrogel could deliver BSA to alkaline conditions (e.g., intestinal environments) site-specifically, which protected BSA from destroying by gastric acid or pepsase. Therefore, such hydrogel had a significant meaning in theoretical research and practical application.

  15. Synthesis, characterization and applications of graphene architectures

    NASA Astrophysics Data System (ADS)

    Thomas, Abhay Varghese

    Graphene, a two--dimensional sheet of sp2 hybridized carbon atoms arranged in a honeycomb lattice structure, has garnered tremendous interest from the scientific community for its unique combination of properties. It has interesting electrical, thermal, optical and mechanical properties that scientists and engineers are trying to understand and harness to improve current products as well as focus on disruptive technologies that can be made possible by this next generation material. In this thesis the synthesis, characterization and applications of various graphene architectures were explored from the context of a bottom--up and top--down synthesis approach. The work is divided into three main chapters and each one deals with a unique architecture of graphene as well as its properties and an application to a real world problem. In Chapter 2, we focus on bottom--up synthesis of graphene sheets by chemical vapor deposition. We then studied the wetting properties of graphene coated surfaces. More specifically the wetting properties of single and multilayer graphene films on flat and nanoscale rough surfaces are explored and the insights gained are used in improving heat transfer performance of copper surfaces. Single layer graphene, on certain flat surfaces, was shown to exhibit `wetting transparency' as a result of its sheer thinness and this property is of interest in various wetting related applications. Surface protection from corrosion and/or oxidation without change in wetting properties is tremendously useful in multiple fields and we looked to apply this property to dehumidification of copper surfaces. The short time scales results demonstrated that graphene indeed served to prevent oxidation of the surface which in turn promoted increased heat transfer co--efficients with respect to the oxidized copper surfaces. Closer inspection of the surface over long time scales however revealed that the oxide layer changed the wetting properties and this was detrimental

  16. Enabling Surgical Placement of Hydrogels Through Achieving Paste-Like Rheological Behavior in Hydrogel Precursor Solutions.

    PubMed

    Beck, Emily C; Lohman, Brooke L; Tabakh, Daniel B; Kieweg, Sarah L; Gehrke, Stevin H; Berkland, Cory J; Detamore, Michael S

    2015-10-01

    Hydrogels are a promising class of materials for tissue regeneration, but they lack the ability to be molded into a defect site by a surgeon because hydrogel precursors are liquid solutions that are prone to leaking during placement. Therefore, although the main focus of hydrogel technology and developments are on hydrogels in their crosslinked form, our primary focus is on improving the fluid behavior of hydrogel precursor solutions. In this work, we introduce a method to achieve paste-like hydrogel precursor solutions by combining hyaluronic acid nanoparticles with traditional crosslinked hyaluronic acid hydrogels. Prior to crosslinking, the samples underwent rheological testing to assess yield stress and recovery using linear hyaluronic acid as a control. The experimental groups containing nanoparticles were the only solutions that exhibited a yield stress, demonstrating that the nanoparticulate rather than the linear form of hyaluronic acid was necessary to achieve paste-like behavior. The gels were also photocrosslinked and further characterized as solids, where it was demonstrated that the inclusion of nanoparticles did not adversely affect the compressive modulus and that encapsulated bone marrow-derived mesenchymal stem cells remained viable. Overall, this nanoparticle-based approach provides a platform hydrogel system that exhibits a yield stress prior to crosslinking, and can then be crosslinked into a hydrogel that is capable of encapsulating cells that remain viable. This behavior may hold significant impact for hydrogel applications where a paste-like behavior is desired in the hydrogel precursor solution. PMID:25691398

  17. Hydrothermal synthesis of pyrochlores and their characterization

    NASA Astrophysics Data System (ADS)

    Redkin, Alexander F.; Ionov, Andrey M.; Kotova, Nataliya P.

    2013-10-01

    Pyrochlores, microlites, and U-betafites of pyrochlore group minerals were obtained from mixing experiments of the corresponding oxides and fluorides by hydrothermal synthesis at T = 800 °C and P = 200 MPa in the solution of 1.0 M NaF. The presence of U4+ in pyrochlore does not affect the cell parameter, which for the phases of pyrochlore-microlite series is 10.42 ± 0.01 Å. In a system with an excess of UO2, pyrochlores and microlites, containing uranium up to 0.2-0.3 atoms per formula unit (apfu), are formed. In the uranium-free system of betafites composition, perovskites and Ti-bearing pyrochlores are formed. U-pyrochlores of betafite series, containing 2Ti = Nb + Ta in moles, have cubic cell parameters of 10.26 ± 0.02 Å and U4+ isomorphic capacity of 0.4-0.5 apfu. In the pyrochlore structure, U4+ may substitute for Ca2+ and Na+ cations in the eightfold site. In pyrochlores of pyrochlore-microlite series, Ca2+ is replaced by U4+, while in pyrochlores of betafite series, U4+ replaces Na+. Phases with pyrochlore structure, containing U5+ and U6+ in the sixfold site, usually occupied by Nb5+, Ta5+, and Ti4+, are formed under oxidizing conditions (Cu-Cu2O buffer). They are characterized by low content of Nb5+, Ta5+ (<0.1 apfu), and anomalous behavior of the crystal lattice (compression, instead of expansion). Under natural conditions, the formation of pyrochlores containing a significant amount of U5+ and U6+ is unlikely.

  18. Synthesis and characterization of mesoporous materials

    NASA Astrophysics Data System (ADS)

    Cheng, Wei

    Mesoporous materials are highly porous solids with pore sizes in the range of 20 to 500 A and a narrow pore size distribution. Creating a mesoporous morphology in transition metal oxides is expected to increase the kinetics of electrochemical photoelectrochemical processes due to the improved accessibility of electrolyte to electrode. The objective of the dissertation research is to prepare functional mesoporous materials based on transition metal oxides and to determine the effects of the mesoporous structure on the resulting charge transfer, electrochromism, and optical properties. In this dissertation, mesoporous tungsten oxide and niobium oxide were synthesized by incorporating tri-block copolymer surfactant templates into the sol-gel synthesis procedure. Both mesoporous materials have surface areas in the range of 130 m2/g with a narrow pore size distribution centered at ˜45A. Their electrochromic properties were characterized and found to be strongly influenced by the mesoporous morphology. Both mesoporous systems exhibit better electrochemical and optical reversibilities than the analogous sol-gel materials (without using surfactant) and the kinetics of bleaching is substantially faster. Coloration efficiencies for the mesoporous tungsten oxide and niobium oxide films are in the range of 16--37 cm 2/C and 12--16 cm2/C, respectively. Dye sensitized solar cells (DSSC) were fabricated using mesoporous niobium oxide as electrodes. Due to the higher surface area, the mesoporous electrodes have greater dye adsorption and electrolyte penetration compared to sol-gel electrodes, which leads to better electron injection, faster dye regeneration and thus, better cell performance. The mesoporous DSSC exhibits photocurrents of 2.9 mA and fill factors of 0.61. Open circuit voltages of the mesoporous DSSC are in the range of 0.6--0.83V.

  19. Preparation and characterization of a novel IPN hydrogel memberane of poly( N-isopropylacrylamide)/carboxymethyl chitosan (PNIPAAM/CMCS)

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Sun, Jie; Yang, Liming; Zhang, Qunfei; Zhu, Huina; Wu, Huifeng; Hoffman, Allan S.; Kaetsu, Isao

    2007-08-01

    A novel type of interpenetrating polymer networks (IPN) hydrogel membrane of poly( N-isopropylacrylamide)/carboxymethyl chitosan (PNIPAAm)/(CMCS) was prepared, and the effects of the feed ratio of components, swelling medium and irradiation dose on the swelling and deswelling properties of the hydrogel was systematically studied. The results showed that the introduction of CMCS did not shift the LCST (at 32 °C), which is similar to the pure PNIPAAm. The lowest swelling ratio was at pH 2. There was little influence of irradiation dose on the thermo- and pH-sensitivity of the IPN hydrogel, increasing dose only decreased the swelling ratio. The PNIPAAm:CMCS=1:4 w/w hydrogel was not thermo-sensitive in distilled water, whereas it showed a discontinuous volume phase transition in pH 2 and a continuous one in pH 8 buffer. Consequently, a combination of pH and temperature can be coupled to control the responsive behavior of these hydrogels.

  20. A Biocompatible and Biodegradable Protein Hydrogel with Green and Red Autofluorescence: Preparation, Characterization and In Vivo Biodegradation Tracking and Modeling

    PubMed Central

    Ma, Xiaoyu; Sun, Xiangcheng; Hargrove, Derek; Chen, Jun; Song, Donghui; Dong, Qiuchen; Lu, Xiuling; Fan, Tai-Hsi; Fu, Youjun; Lei, Yu

    2016-01-01

    Because of its good biocompatibility and biodegradability, albumins such as bovine serum albumin (BSA) and human serum albumin (HSA) have found a wide range of biomedical applications. Herein, we report that glutaraldehyde cross-linked BSA (or HSA) forms a novel fluorescent biological hydrogel, exhibiting new green and red autofluorescence in vitro and in vivo without the use of any additional fluorescent labels. UV-vis spectra studies, in conjunction with the fluorescence spectra studies including emission, excitation and synchronous scans, indicated that three classes of fluorescent compounds are presumably formed during the gelation process. SEM, FTIR and mechanical tests were further employed to investigate the morphology, the specific chemical structures and the mechanical strength of the as-prepared autofluorescent hydrogel, respectively. Its biocompatibility and biodegradability were also demonstrated through extensive in vitro and in vivo studies. More interestingly, the strong red autofluorescence of the as-prepared hydrogel allows for conveniently and non-invasively tracking and modeling its in vivo degradation based on the time-dependent fluorescent images of mice. A mathematical model was proposed and was in good agreement with the experimental results. The developed facile strategy to prepare novel biocompatible and biodegradable autofluorescent protein hydrogels could significantly expand the scope of protein hydrogels in biomedical applications. PMID:26813916

  1. A Biocompatible and Biodegradable Protein Hydrogel with Green and Red Autofluorescence: Preparation, Characterization and In Vivo Biodegradation Tracking and Modeling

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoyu; Sun, Xiangcheng; Hargrove, Derek; Chen, Jun; Song, Donghui; Dong, Qiuchen; Lu, Xiuling; Fan, Tai-Hsi; Fu, Youjun; Lei, Yu

    2016-01-01

    Because of its good biocompatibility and biodegradability, albumins such as bovine serum albumin (BSA) and human serum albumin (HSA) have found a wide range of biomedical applications. Herein, we report that glutaraldehyde cross-linked BSA (or HSA) forms a novel fluorescent biological hydrogel, exhibiting new green and red autofluorescence in vitro and in vivo without the use of any additional fluorescent labels. UV-vis spectra studies, in conjunction with the fluorescence spectra studies including emission, excitation and synchronous scans, indicated that three classes of fluorescent compounds are presumably formed during the gelation process. SEM, FTIR and mechanical tests were further employed to investigate the morphology, the specific chemical structures and the mechanical strength of the as-prepared autofluorescent hydrogel, respectively. Its biocompatibility and biodegradability were also demonstrated through extensive in vitro and in vivo studies. More interestingly, the strong red autofluorescence of the as-prepared hydrogel allows for conveniently and non-invasively tracking and modeling its in vivo degradation based on the time-dependent fluorescent images of mice. A mathematical model was proposed and was in good agreement with the experimental results. The developed facile strategy to prepare novel biocompatible and biodegradable autofluorescent protein hydrogels could significantly expand the scope of protein hydrogels in biomedical applications.

  2. Boron carbide nanowires: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  3. Preparation, characterization and protein sorption of photo-crosslinked cell membrane-mimicking chitosan-based hydrogels.

    PubMed

    Zhao, Yunfei; Ma, Liubo; Zeng, Rong; Tu, Mei; Zhao, Jianhao

    2016-10-20

    Photocrosslinkable biomimetic chitosan derivative, glycidyl methacrylate-phosphorylcholine-chitosan (PCCs-GMA) was synthesized through the combination of Atherton-Todd reaction for coupling phosphorylcholine and ring opening reaction of epoxides for attaching GMA, and confirmed by (1)H and (31)P NMR and Fourier transform infrared (FTIR) spectroscopy. The photo-crosslinking reaction of PCCs-GMA with different degree of substitution (DS) of GMA allowed the formation of biomimetic hydrogels with tunable mechanical and swelling properties. Cold crystallization behaviors ascribed to their restrained freezing bound water were investigated using differential scanning calorimetry (DSC). The rheological and swelling behaviors, hemolysis as well as protein sorption of PCCs-GMA hydrogels were investigated in terms of the DS of GMA, using fibrinogen, bovine serum albumin and lysozyme as model proteins. Low irreversible protein sorption and non hemolytic results indicated that photo-crosslinked PCCs-GMA hydrogels may offer a promising candidate material with resistance to protein fouling in biomedical applications. PMID:27474563

  4. A multimaterial bioink method for 3D printing tunable, cell-compatible hydrogels.

    PubMed

    Rutz, Alexandra L; Hyland, Kelly E; Jakus, Adam E; Burghardt, Wesley R; Shah, Ramille N

    2015-03-01

    A multimaterial bio-ink method using polyethylene glycol crosslinking is presented for expanding the biomaterial palette required for 3D bioprinting of more mimetic and customizable tissue and organ constructs. Lightly crosslinked, soft hydrogels are produced from precursor solutions of various materials and 3D printed. Rheological and biological characterizations are presented, and the promise of this new bio-ink synthesis strategy is discussed. PMID:25641220

  5. Synthesis and characterization of Schiff's bases of sulfamethoxazole

    PubMed Central

    2014-01-01

    Background Schiff's bases are excellent ligands which are synthesized from the condensation of primary amines with carbonyl groups. Findings The classical reaction for the synthesis of Schiff's bases in an ethanolic solution and glacial acetic acid as a catalyst was followed in the synthesis of substituted sulfamethoxazole compounds. Conclusions Some Schiff's bases containing sulfamethoxazole nucleus have been synthesized and characterized. The present compounds are hoped to be applied in the photostability of PVC. PMID:24576663

  6. Tannic acid functionalized graphene hydrogel for entrapping gold nanoparticles with high catalytic performance toward dye reduction.

    PubMed

    Luo, Jing; Zhang, Nan; Lai, Jianping; Liu, Ren; Liu, Xiaoya

    2015-12-30

    In this work, a simple, cost-effective, and environmental-friendly strategy was developed to synthesize gold nanoparticles (Au NPs) decorated graphene hydrogel with the use of tannic acid. This facile route involved the reduction of graphene oxide (GO) in the presence of tannic acid to form tannic acid functionalized graphene hydrogel, followed by loading and in situ reduction of AuCl4(-) ions in the graphene hydrogel network benefiting from the abundant phenol groups of tannic acid. Tannic acid (TA), a typical plant polyphenol widely present in woods, not only reduced GO and induced the self-assembly of reduced graphene oxide into graphene hydrogel, but also served as the reducing agent and stabilizer for the synthesis and immobilization of Au NPs, avoiding extra chemical reagent and any stabilizer. The obtained Au NPs decorated graphene hydrogel (Au@TA-GH) was fully characterized and exhibited much higher catalytic activities than the unsupported and other polymer-supported Au NPs toward the reduction of methylene blue (MB). In addition, the high catalytic activity of Au@TA-GH could withhold in different pH solution conditions. Another distinct advantage of Au@TA-GH as catalysts is that it can be easily recovered and reused for five cycles. PMID:26275351

  7. Controlled release of protein from biodegradable multi-sensitive injectable poly(ether-urethane) hydrogel.

    PubMed

    Li, Xiaomeng; Wang, Yangyun; Chen, Jiaming; Wang, Yinong; Ma, Jianbiao; Wu, Guolin

    2014-03-12

    The synthesis and characterization of multi-sensitive polymers for use as injectable hydrogels for controlled protein/drug delivery is reported. A series of biodegradable multi-sensitive poly(ether-urethane)s were prepared through a simple one-pot condensation of poly(ethylene glycol), 2,2'-dithiodiethanol, N-methyldiethanolamine, and hexamethylene diisocyanate. The sol-gel phase transition behaviors of the obtained copolymers were investigated. Experimental results showed that the aqueous medium comprising the multi-segment copolymers underwent a sol-to-gel phase transition with increasing temperature and pH. At a certain concentration, the copolymer solution could immediately change to a gel under physiological conditions (37 °C and pH 7.4), indicating their suitability as in situ injectable hydrogels in vivo. Insulin was used as a model protein drug for evaluation of the injectable hydrogels as a site-specific drug delivery system. The controlled release of insulin from the hydrogel devices was demonstrated by degradation of the copolymer, which is modulated via the 2,2'-dithiodiethanol content in the poly(ether-urethane)s. These hydrogels having multi-responsive properties may prove to be promising candidates for injectable and controllable protein drug delivery devices. PMID:24460175

  8. Timolol maleate release from hyaluronic acid-containing model silicone hydrogel contact lens materials.

    PubMed

    Korogiannaki, Myrto; Guidi, Giuliano; Jones, Lyndon; Sheardown, Heather

    2015-09-01

    This study was designed to assess the impact of a releasable wetting agent, such as hyaluronic acid (HA), on the release profile of timolol maleate (TM) from model silicone hydrogel contact lens materials. Polyvinylpyrrolidone (PVP) was used as an alternative wetting agent for comparison. The model lenses consisted of a hydrophilic monomer, either 2-hydroxyethyl methacrylate or N,N-dimethylacrylamide and a hydrophobic silicone monomer of methacryloxypropyltris (trimethylsiloxy) silane. The loading of the wetting and the therapeutic agent occurred during the synthesis of the silicone hydrogels through the method of direct entrapment. The developed materials were characterized by minimal changes in the water uptake, while lower molecular weight of HA improved their surface wettability. The transparency of the examined silicone hydrogels was found to be affected by the miscibility of the wetting agent in the prepolymer mixture as well as the composition of the developed silicone hydrogels. Sustained release of TM from 4 to 14 days was observed, with the drug transport occurring presumably through the hydrophilic domains of the silicone hydrogels. The release profile was strongly dependent on the hydrophilic monomer composition, the distribution of hydrophobic (silane) domains, and the affinity of the therapeutic agent for the silicone hydrogel matrix. Noncovalent entrapment of the wetting agent did not change the in vitro release duration and kinetics of TM, however the drug release profile was found to be controlled by the simultaneous release of TM and HA or PVP. In the case of HA, depending on the HA:drug ratio, the release rate was decreased and controlled by the release of HA, likely due to electrostatic interactions between protonated TM and anionic HA. Overall, partitioning of the drug within the hydrophilic domains of the silicone hydrogels as well as interactions with the wetting agent determined the drug release profile. PMID:25887216

  9. Chitosan-Iron Oxide Coated Graphene Oxide Nanocomposite Hydrogel: A Robust and Soft Antimicrobial Biofilm.

    PubMed

    Konwar, Achyut; Kalita, Sanjeeb; Kotoky, Jibon; Chowdhury, Devasish

    2016-08-17

    We report a robust biofilm with antimicrobial properties fabricated from chitosan-iron oxide coated graphene oxide nanocomposite hydrogel. For the first time, the coprecipitation method was used for the successful synthesis of iron oxide coated graphene oxide (GIO) nanomaterial. After this, films were fabricated by the gel-casting technique aided by the self-healing ability of the chitosan hydrogel network system. Both the nanomaterial and the nanocomposite films were characterized by techniques such as scanning electron microscopy, FT-IR spectroscopy, X-ray diffraction, and vibrating sample magnetometry. Measurements of the thermodynamic stability and mechanical properties of the films indictaed a significant improvement in their thermal and mechanical properties. Moreover, the stress-strain profile indicated the tough nature of the nanocomposite hydrogel films. These improvements, therefore, indicated an effective interaction and good compatibility of the GIO nanomaterial with the chitosan hydrogel matrix. In addition, it was also possible to fabricate films with tunable surface properties such as hydrophobicity simply by varying the loading percentage of GIO nanomaterial in the hydrogel matrix. Fascinatingly, the chitosan-iron oxide coated graphene oxide nanocomposite hydrogel films displayed significant antimicrobial activities against both Gram-positive and Gram-negative bacterial strains, such as methicillin-resistant Staphylococcus aureus, Staphylococcus aureus, and Escherichia coli, and also against the opportunistic dermatophyte Candida albicans. The antimicrobial activities of the films were tested by agar diffusion assay and antimicrobial testing based on direct contact. A comparison of the antimicrobial activity of the chitosan-GIO nanocomposite hydrogel films with those of individual chitosan-graphene oxide and chitosan-iron oxide nanocomposite films demonstrated a higher antimicrobial activity for the former in both types of tests. In vitro hemolysis

  10. Synthesis, Characterization and Chondroprotective Properties of a Hyaluronan Thioethyl Ether Derivative

    PubMed Central

    Serban, Monica A.; Yang, Guanghui; Prestwich, Glenn D.

    2008-01-01

    Hyaluronan (HA), a non-sulfated glycosaminoglycan, is widely used in the clinic for viscosurgery, viscosupplementation, and treatment of osteoarthritis. Four decades of chemical modification of HA have generated derivatives in which the biophysical and biochemical properties, as well as the rates of enzymatic degradation in vivo have been manipulated and tailored for specific clinical needs. One earlier modification adds multiple thiol groups to HA through hydrazide linkages, leading to a readily crosslinkable material for adhesion prevention and wound healing. We now describe the synthesis and chemical characterization of a novel thioethyl ether derivative of HA, HA–sulfhydryl (HASH), with a minimal tether between the HA and the thiol group. Unlike earlier thiol-modified HA derivatives, HASH cannot be readily crosslinked to form a hydrogel using either oxidative or bivalent electrophilic conditions, thus offering a unique polymeric polythiol that remains soluble. Moreover, HASH showed no cytotoxicity towards primary human fibroblasts and reduced the apoptosis rates of primary chondrocytes exposed to hydrogen peroxide in vitro. These properties foreshadow the clinical potential of HASH to moderate inflammation and to act as a chondroprotective agent in vivo. PMID:18158182

  11. Characterization of Hydrogels Formed via Intramolecular Folding and Consequent Self-Assembly of Beta-HAIRPIN Peptides

    NASA Astrophysics Data System (ADS)

    Ozbas, Bulent; Pakstis, Lisa; Pochan, Darrin J.; Rajagopal, Karthikan; Gill, Juliana; Schneider, Joel P.

    2003-03-01

    Stimuli-responsive and biocompatible networks formed via self-assembly serve great opportunities in tissue engineering and drug delivery applications. In this work we present the formation of hydrogels via the intramolecular folding and consequent self-assembly of 20 aminoacid long beta-Hairpin peptide molecules. These hairpin molecules are amphiphilic in nature with an alternating sequence of hydrophobic valine and hydrophilic lysine amino acids. These molecules are found to form hydrogels with a unique microstructure and nanostructure at different physical condition at low peptide concentrations ( ˜ 1 wt %). However, gelation is observed at high pH values ( ˜9) and at high salt concentrations ( ˜150 mM) where beta-sheet secondary structure due to hairpin folding is observed. The intimate relationship between beta-Hairpin molecule turn sequence and the consequent materials properties will be discussed. LSCM data reveals that hydrogel structure is heterogeneous at the microscale with water channels in the order of 10 μm. Cryo-TEM technique shows that the network is consists of interconnected fibrillar/tubular networks. The viscoelastic properties of the hydrogels, as measured by rheology. Importantly, the gel is also reversible with pH, returning to a viscosity of water with a drop in pH that unfolds, and disassembles, the hairpin molecules.

  12. Preparation and Characterization of Electrospun PLCL/Poloxamer Nanofibers and Dextran/Gelatin Hydrogels for Skin Tissue Engineering

    PubMed Central

    Sun, Hui; Xu, Feng

    2014-01-01

    In this study, two different biomaterials were fabricated and their potential use as a bilayer scaffold for skin tissue engineering applications was assessed. The upper layer biomaterial was a Poly(ε-caprolactone-co-lactide)/Poloxamer (PLCL/Poloxamer) nanofiber membrane fabricated using electrospinning technology. The PLCL/Poloxamer nanofibers (PLCL/Poloxamer, 9/1) exhibited strong mechanical properties (stress/strain values of 9.37±0.38 MPa/187.43±10.66%) and good biocompatibility to support adipose-derived stem cells proliferation. The lower layer biomaterial was a hydrogel composed of 10% dextran and 20% gelatin without the addition of a chemical crosslinking agent. The 5/5 dextran/gelatin hydrogel displayed high swelling property, good compressive strength, capacity to present more than 3 weeks and was able to support cells proliferation. A bilayer scaffold was fabricated using these two materials by underlaying the nanofibers and casting hydrogel to mimic the structure and biological function of native skin tissue. The upper layer membrane provided mechanical support in the scaffold and the lower layer hydrogel provided adequate space to allow cells to proliferate and generate extracellular matrix. The biocompatibility of bilayer scaffold was preliminarily investigated to assess the potential cytotoxicity. The results show that cell viability had not been affected when cocultured with bilayer scaffold. As a consequence, the bilayer scaffold composed of PLCL/Poloxamer nanofibers and dextran/gelatin hydrogels is biocompatible and possesses its potentially high application prospect in the field of skin tissue engineering. PMID:25405611

  13. Bacterial expression of self-assembling peptide hydrogelators

    NASA Astrophysics Data System (ADS)

    Sonmez, Cem

    For tissue regeneration and drug delivery applications, various architectures are explored to serve as biomaterial tools. Via de novo design, functional peptide hydrogel materials have been developed as scaffolds for biomedical applications. The objective of this study is to investigate bacterial expression as an alternative method to chemical synthesis for the recombinant production of self-assembling peptides that can form rigid hydrogels under physiological conditions. The Schneider and Pochan Labs have designed and characterized a 20 amino acid beta-hairpin forming amphiphilic peptide containing a D-residue in its turn region (MAX1). As a result, this peptide must be prepared chemically. Peptide engineering, using the sequence of MAX1 as a template, afforded a small family of peptides for expression (EX peptides) that have different turn sequences consisting of natural amino acids and amenable to bacterial expression. Each sequence was initially chemically synthesized to quickly assess the material properties of its corresponding gel. One model peptide EX1, was chosen to start the bacterial expression studies. DNA constructs facilitating the expression of EX1 were designed in such that the peptide could be expressed with different fusion partners and subsequently cleaved by enzymatic or chemical means to afford the free peptide. Optimization studies were performed to increase the yield of pure peptide that ultimately allowed 50 mg of pure peptide to be harvested from one liter of culture, providing an alternate means to produce this hydrogel-forming peptide. Recombinant production of other self-assembling hairpins with different turn sequences was also successful using this optimized protocol. The studies demonstrate that new beta-hairpin self-assembling peptides that are amenable to bacterial production and form rigid hydrogels at physiological conditions can be designed and produced by fermentation in good yield at significantly reduced cost when compared to

  14. Characterization of physicochemical properties of perfluorodecanoic acid-polyquaternium cellulose hydrogel.

    PubMed

    Bierbrauer, Karina L; Alasino, Roxana V; Strumia, Miriam C; Beltramo, Dante M

    2012-01-01

    We investigated the nature and stability of the interactions established between polyquaternium (PQ10) and perfluorodecanoic acid (PFDA) in terms of different variables such as composition, ionic strength, pH and temperature. The PQ10-PFDA complex formation is interpreted in view of electrostatic associations between carboxylic and quaternary amino group. The properties of the systems were characterized by rheology analysis. The adhesive properties of complex were also assessed. One of the macroscopic features of the new material formed in solution was the increase in viscosity from 6 Pas for 1% PQ10 (MW 1.7×10(6) g mol(-1)) to about 1000 Pas by the addition of enough PFDA to reach 1:0.5 ammonium:carboxylic group molar ratio. At this proportion, PQ10 and PFDA form a network structure with a maximum viscosity and storage modulus. This maximum coincides with an increased mucoadhesive work. PMID:21925848

  15. Templating hydrogels.

    PubMed

    Texter, John

    2009-03-01

    Templating processes for creating polymerized hydrogels are reviewed. The use of contact photonic crystals and of non-contact colloidal crystalline arrays as templates are described and applications to chemical sensing and device fabrication are illustrated. Emulsion templating is illustrated in the formation of microporous membranes, and templating on reverse emulsions and double emulsions is described. Templating in solutions of macromolecules and micelles is discussed and then various applications of hydrogel templating on surfactant liquid crystalline mesophases are illustrated, including a nanoscale analogue of colloidal crystalline array templating, except that the bead array in this case is a cubic array of nonionic micelles. The use of particles as templates in making core-shell and hollow microgel beads is described, as is the use of membrane pores as another illustration of confinement templating. PMID:19816529

  16. Characterization of slow-gelling alginate hydrogels for intervertebral disc tissue-engineering applications.

    PubMed

    Growney Kalaf, Emily A; Flores, Reynaldo; Bledsoe, J Gary; Sell, Scott A

    2016-06-01

    Reversal of intervertebral disc degeneration can have a potentially monumental effect on spinal health. As such, the goal of this research is to create an injectable, cellularized alginate-based nucleus pulposus that will restore disc function; with the primary goal of creating an alginate gel with tailorable rates of gelation to improve functionality over standard CaCl2 crosslinking techniques. Gelation characteristics of 1% sodium alginate were analyzed over various molar concentrations of a 1:2 ratio of CaCO3:glucono-δ-lactone (GDL), with 10% CaCl2 as the control crosslinker. Alginate construct characterization for all concentrations was performed via ultimate and cyclic compressive testing over a 28day degradation period in PBS. Dehydration, swell testing, and albumin release kinetics were determined, and cytotoxicity and cell homogeneity tests showed promise for cellularization strategies. Overall, the 30 and 60mM GDL alginate concentrations presented the most viable option for use in further studies, with a gelation time between 10 and 30min, low hysteresis over control, low percent change in thickness and weight under both PBS degradation and swelling conditions, and stable mechanical properties over 28days in vitro. PMID:27040212

  17. Ionotropically Gelled Novel Hydrogel Beads: Preparation, Characterization and In vitro Evaluation

    PubMed Central

    Patil, J. S.; Kamalapur, M. V.; Marapur, S. C.; Shiralshetti, S. S.

    2011-01-01

    Prolonged release drug delivery system of stavudine was made by ionotropic gelation and polyelectrolyte complexation technique. Cross-linking reinforced chitosan-gellan complex beads were prepared by gelation of anionic gellan gum, the primary polymer, with oppositely charged counter ion to form beads which were further complexed with chitosan as a polyelectrolyte. The effect of this polymer on release profile of drug was studied. Beads without chitosan complexation were also made. The reaction of chitosan-gellan complex dominates the formation of skin layer on the surface of beads. Stavudine an antiretroviral drug was selected as novel drug for the experiment. The final formulations were subjected to in vitro evaluation and several characterization studies. Batches with gellan gum shows Higuchi model, while chitosan-gellan shows zero order release. All the batches with copolymer showed sustained the drug release more than 12 h, whereas with gellan gum alone showed up to 10 h. Batches with chitosan showed maximum drug encapsulation efficiency. PMID:22923862

  18. On the development of multifunctional luminescent supramolecular hydrogel of gold and egg white.

    PubMed

    Patra, Sudeshna; Ravulapalli, Sathyavathi; Hahm, Myung Gwan; Tadi, Kiran Kumar; Narayanan, Tharangattu N

    2016-10-14

    Highly stable, luminescent, and printable/paintable supramolecular egg white hydrogel-based surface enhanced Raman scattering (SERS) matrix is created by an in situ synthesis of gold clusters inside a luminescent egg white hydrogel (Au-Gel). The synthesis of stable luminescent egg-white-based hydrogel, where the hydrogel can act as a three dimensional (3D) matrix, using a simple cross-linking chemistry, has promising application in the biomedical field including in 3D cell culturing. Furthermore, this functional hydrogel is demonstrated for micromolar-level detection of Rhodamine 6G using the SERS technique, where Au-Gel is painted over a flexible cellulose pad. PMID:27608886

  19. Synthesis, characterization and applications of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kanmukhla, Vikram Kumar

    In the past few years, the synthesis of magnetic nanoparticles has received considerable attention due to their potential use in clinical applications. Since the properties of these nanoparticles depend strongly on their size, shape and crystallinity, there is a need for a general method to produce these particles with a controlled size, shape and crystal type. Of the many magnetic materials (Co, Ni, and Fe), the magnetite (Fe3O 4) is least toxic and hence most promising for applications in medical diagnostics. Microemulsion-based synthesis utilizes the local aqueous environment within a reverse micelle as a nano-scale reactor and allows synthesizing nanoparticles with a hydrophilic surface for subsequent functionalization. By controlling the water-to-surfactant ratio, the type of surfactants, and the ionic strength of the aqueous core, one can control the size and shape of the resulting particles. We developed such a system that allows the multi-step synthesis of surface-functionalized, magnetic nanoparticles in a one-pot synthesis reaction. By altering the system chemistry, we were further able to produce either spheres or cylinders of controlled dimension in the size range of 5 nm to 30 nm. Using standard bio-conjugation techniques, we successfully immobilized an enzyme onto the nanoparticles. We also developed a theoretical model for the separation and fractionation of nanoparticles based on their size and magnetic properties. Using the multiphysics and finite element modeling capabilities of FEMLAB(TM), we solved the coupled system of PDEs describing the interaction of magnetic particles within a magnetic field for either static (cylindrical beaker) or convective flow (capillary) conditions. A net retention time as high as 310 s is achieved for 200 nm particles at field strength of 1250 kA/m. The model allows the design of a magnetic, field-flow fractionation (MFFF) system to separate nanoparticles by size.

  20. Synthesis and characterization of magnetite nanoparticles coated with lauric acid

    SciTech Connect

    Mamani, J.B.; Costa-Filho, A.J.; Cornejo, D.R.; Vieira, E.D.; Gamarra, L.F.

    2013-07-15

    Understanding the process of synthesis of magnetic nanoparticles is important for its implementation in in vitro and in vivo studies. In this work we report the synthesis of magnetic nanoparticles made from ferrous oxide through coprecipitation chemical process. The nanostructured material was coated with lauric acid and dispersed in aqueous medium containing surfactant that yielded a stable colloidal suspension. The characterization of magnetic nanoparticles with distinct physico-chemical configurations is fundamental for biomedical applications. Therefore magnetic nanoparticles were characterized in terms of their morphology by means of TEM and DLS, which showed a polydispersed set of spherical nanoparticles (average diameter of ca. 9 nm) as a result of the protocol. The structural properties were characterized by using X-ray diffraction (XRD). XRD pattern showed the presence of peaks corresponding to the spinel phase of magnetite (Fe{sub 3}O{sub 4}). The relaxivities r{sub 2} and r{sub 2}* values were determined from the transverse relaxation times T{sub 2} and T{sub 2}* at 3 T. Magnetic characterization was performed using SQUID and FMR, which evidenced the superparamagnetic properties of the nanoparticles. Thermal characterization using DSC showed exothermic events associated with the oxidation of magnetite to maghemite. - Highlights: • Synthesis of magnetic nanoparticles coated with lauric acid • Characterization of magnetic nanoparticles • Morphological, structural, magnetic, calorimetric and relaxometric characterization.

  1. Characterization of microstructure, viscoelasticity, heterogeneity and ergodicity in pectin-laponite-CTAB-calcium nanocomposite hydrogels.

    PubMed

    Joshi, Nidhi; Rawat, Kamla; Bohidar, H B

    2016-01-20

    In order to customize the viscoelastic properties of pectin gels, it is necessary to work on a composite platform. Herein, the gelation kinetics, and viscoelastic characterization of anionic polysaccharide pectin dispersion prepared in presence of nanoclay laponite are reported using dynamic light scattering and rheology measurements. The ratio Rg/Rh (Rg and Rh are radius of gyration and hydrodynamic radius respectively) determined from light scattering data revealed the presence of random coils of pectin chains inside the gel matrix. When nanoclay laponite was added to the pectin chains solution, two-phase separation was noticed instantaneously. Therefore, the surfactant cetyltrimethylammonium bromide [CTAB] was added to exfoliate the clay platelets in the dispersion, and also in its gel phase. The exfoliating agent cetyltrimethylammonium bromide ([CTAB]≈ cmc/10) helped to enhance the homogeneity and stability of the pectin-clay sols and gels. The storage and loss moduli (G' and G") of the composite gel changed significantly as function of nanoclay laponite content for concentration up to 0.03% (w/v) causing the softening of the gels (gel strength reduced by close to 50%) compared to pectin-calcium gel. However, as the concentration of nanoclay laponite was maintained between 0.01% and 0.03% (w/v), the gel rigidity (G') recovered by 30% (35-45 Pa). The transition from ergodic to non-ergodic state occurred during sol-gel transition owing to the presence of the nanoclay laponite. The gelation time was not too different from the ergodicity breaking time. Thus, the presence of nanoclay laponite in such minute concentration is shown to cause considerable change in the thermo-physical property of the composite gels. This material property modulation will facilitate designing of soft gels having storage modulus continuously varying in the wide range of 10-70 Pa while keeping the gelation temperature mostly unaltered. PMID:26572352

  2. Polymer-induced compression of biological hydrogels

    NASA Astrophysics Data System (ADS)

    Datta, Sujit; Preska Steinberg, Asher; Ismagilov, Rustem

    Hydrogels - such as mucus, blood clots, and the extracellular matrix - provide critical functions in biological systems. However, little is known about how their structure is influenced by many of the polymeric materials they come into contact with regularly. Here, we focus on one critically important biological hydrogel: colonic mucus. While several biological processes are thought to potentially regulate the mucus hydrogel structure, the polymeric composition of the gut environment has been ignored. We use Flory-Huggins solution theory to characterize polymer-mucus interactions. We find that gut polymers, including those small enough to penetrate the mucus hydrogel, can in fact alter mucus structure, changing its equilibrium degree of swelling and forcing it to compress. The extent of compression increases with increasing polymer concentration and size. We use experiments on mice to verify these predictions with common dietary and therapeutic gut polymers. Our results provide a foundation for investigating similar, previously overlooked, polymer-induced effects in other biological hydrogels.

  3. Hydrogels and their medical applications

    NASA Astrophysics Data System (ADS)

    Rosiak, Janusz M.; Yoshii, Fumio

    1999-05-01

    Biomaterials play a key role in most approaches for engineering tissues as substitutes for functional replacement, for components of devices related to therapy and diagnosis, for drug delivery systems and supportive scaffolds for guided tissue growth. Modern biomaterials could be composed of various components, e.g. metals, ceramics, natural tissues, polymers. In this last group, the hydrogels, hydrophilic polymeric gels with requested biocompatibility and designed interaction with living surrounding seem to be one of the most promising group of biomaterials. Especially, if they are formed by means of ionizing radiation. In early 1950s, the pioneers of the radiation chemistry of polymers began some experiments with radiation crosslinking of hydrophilic polymers. However, hydrogels were analyzed mainly from the point of view of the phenomenon associated with radiation synthesis, with topology of network and relation between radiation parameters of the processes. Fundamental monographs on radiation polymer physics and chemistry written by A. Charlesby (Atomic Radition and polymers, Pergamon Press, Oxford, 1960) and A. Chapiro (Radiation Chemistry of Polymeric Systems, Interscience, New York, 1962) proceed from this time. The noticeable interest in the application of radiation techniques to obtain hydrogels for biomedical purposes began in the late sixties as a result of the papers and patents invented by Japanese and American scientists, headed by Kaetsu in Japan and Hoffman in USA. Immobilization of biologically active species in hydrogel matrices, their use as drug delivery systems and enzyme traps as well as the modification of material surfaces to improve biocompatibility and their ability to bond antigens and antibodies had been the main subjects of these investigations. In this article a brief summary of investigations on mechanism and kinetics of radiation formation of hydrogels as well as some examples of commercialized hydrogel biomaterials have been

  4. Laser ablation synthesis and spectral characterization of ruby nanoparticles

    NASA Astrophysics Data System (ADS)

    Baranov, M. S.; Bardina, A. A.; Savelyev, A. G.; Khramov, V. N.; Khaydukov, E. V.

    2016-04-01

    The laser ablation method was implemented for synthesis of ruby nanoparticles. Nanoparticles were obtained by nanosecond ablation of bulk ruby crystal in 10% ethanol water solution. The nanoparticles enable water colloid stability and exhibit narrow photoluminescent line at 694 nm when pumped at blue-green spectral range. The ruby nanoparticles were characterized by SEM and Z-sizer.

  5. Synthesis and Characterization of Cellulose Derivatives for Water Repellent Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this presentation, we will discuss the synthesis and structural characterizations of nitro-benzyl cellulose (1), amino-benzyl cellulose (2) and pentafluoro –benzyl cellulose (3). All cellulose derivatives are synthesized by etherification process in lithium chloride/N,N-dimethylacetamide homogene...

  6. Synthesis and Characterization of Processable Polyimides with Enhanced Thermal Stability

    NASA Technical Reports Server (NTRS)

    Harris, Frank W.

    1999-01-01

    The following is a summary report of the research carried out under NASA Grant NAG-1-448. The work was divided into four major areas: 1) Enhanced polyimide processing through the use of reactive plasticizers 2) Development of processable polyhenylquinoxalines 3) Synthesis and characterization of perfluorovinylether-terminated imide oligomers and 4) Fluorosilicones containing perfuorocyclobutane rings.

  7. The synthesis and characterization of iron nanoparticles

    NASA Astrophysics Data System (ADS)

    Bennett, Tyler

    Nanoparticle synthesis has garnered attention for technological applications for catalysts, industrial processing, and medical applications. The size ranges for these is in the particles nanostructural domain. Pure iron nanoparticles have been of particular interest for their reactivity and relative biological inertness. Applications include cancer treatment and carrying medicine to a relevant site. Unfortunately, because of their reactivity, pure iron nanoparticles have been difficult to study. This is because of their accelerated tendency to form oxides in air, due to the increased surface area to volume ratio. Using synthesis processes with polyphenols or long chain amines, air stable iron nanoparticles have been produced with a diameter size range of ~ 2 to about ~10 nm, but apparently have transformed due to internal pressure and crystallographic defects to the FCC phase. The FCC crystals have been seen to form icosahedral and decahedral shapes. This size is within the range for use as a catalyst for the growth of both carbon nanotubes and boron nitride nanotubes as well for biomedical applications. The advantages of these kinds of catalysts are that nanotube growth can be for the first time separated from the catalyst formation. Additionally, the catalyst size can be preselected for a certain size nanotube to grow. In summary: (1) we found the size distributions of nanoparticles for various synthesis processes, (2) we discovered the right size range for growth of nanotubes from the iron nanoparticles, (3) the nanoparticles are under a very high internal pressure, (4) the nanoparticles are in the FCC phase, (5) they appear to be in icosahedral and decahedral structures, (6) they undergo room temperature twinning, (7) the FCC crystals are distorted due to carbon in octahedral sites, (8) the iron nanoparticles are stable in air, (9) adding small amounts of copper make the iron nanoparticles smaller.

  8. Synthesis and characterization of diallyl phthalate prepolymers

    SciTech Connect

    Baker, G.K.; Parker, B.G.

    1982-12-01

    Methods for the laboratory synthesis of diallyl phthalate prepolymers were evaluated. The chemical, physical, and molecular weight properties of several prepolymers synthesized were also evaluated and compared to those properties exhibited by Dapon 35 and Daiso 35, manufactured by FMC Corporation and Osaka-Soda, respectively. Glass-filled molding compounds from four of the prepolymers having molecular weight distributions ranging from 1.9 to 40.2 were prepared and tested at the Monsanto Research Corporation, Mound Facility. The processing characteristics and physical and electrical properties of two molding compounds were found to be comparable to similar compounds made from Dapon 35 and Daiso 35.

  9. Molybdenum oxide nanocubes: Synthesis and characterizations

    SciTech Connect

    Muthamizh, S.; Suresh, R.; Giribabu, K.; Manigandan, R.; Kumar, S. Praveen; Munusamy, S.; Narayanan, V.; Stephen, A.

    2015-06-24

    Molybdenum oxide nanoparticles were prepared by Solid state synthesis. The MoO{sub 3} nanoparticles were synthesized by using commercially available ammonium heptamolybdate. The XRD pattern reveals that the synthesized MoO{sub 3} has orthorhombic structure. In addition, lattice parameter values were also calculated using XRD data. The Raman analysis confirm the presence of Mo-O in MoO{sub 3} nanoparticles. DRS-UV analysis shows that MoO{sub 3} has a band gap of 2.89 eV. FE-SEM analysis confirms the material morphology in cubes with nano scale.

  10. Development and physical characterization of polymer-fish oil bigel (hydrogel/oleogel) system as a transdermal drug delivery vehicle.

    PubMed

    Rehman, Khurram; Mohd Amin, Mohd Cairul Iqbal; Zulfakar, Mohd Hanif

    2014-01-01

    Polymer-Fish oil bigel (hydrogel/oleogel colloidal mixture) was developed by using fish oil and natural (sodium alginate) and synthetic (hydroxypropyl methylcellulose) polymer for pharmaceutical purposes. The bigels were closely monitored and thermal, rheological and mechanical properties were compared with the conventional hydrogels for their potential use as an effective transdermal drug delivery vehicle. Stability of the fish oil fatty acids (especially eicosapentanoic acid, EPA and docosahexanoic acid, DHA) was determined by gas chromatography and the drug content (imiquimod) was assessed with liquid chromatography. Furthermore, in vitro permeation study was conducted to determine the capability of the fish oil-bigels as transdermal drug delivery vehicle. The bigels showed pseudoplastic rheological features, with excellent mechanical properties (adhesiveness, peak stress and hardness), which indicated their excellent spreadability for application on the skin. Bigels prepared with mixture of sodium alginate and fish oil (SB1 and SB2), and the bigels prepared with the mixture of hydroxypropyl methylcellulose and fish oil (HB1-HB3) showed high cumulative permeation and drug flux compared to hydrogels. Addition of fish oil proved to be beneficial in increasing the drug permeation and the results were statistically significant (p < 0.05, one-way Anova, SPSS 20.0). Thus, it can be concluded that bigel formulations could be used as an effective topical and transdermal drug delivery vehicle for pharmaceutical purposes. PMID:25252741

  11. Synthesis and Characterization of Smart Block Copolymers for Biomineralization and Biomedical Applications

    SciTech Connect

    Kanapathipillai, Mathumai

    2008-01-01

    pH of the solution. Polymers with polyzwitterions, anions and cations have been shown to exhibit pH responsive self assembly. Other stimuli responsive polymers include glucose sensitive polymers, calcium ion-sensitive polymers and so on. Progress in living radical polymerization (LRP) methods [10] has made it possible for the facile synthesis of these block copolymer systems with controlled molecular weights and well defined architectures. The overall theme of this work is to develop novel smart block copolymers for biomineralization and biomedical applications. Synthesis and characterization of self-assembling thermoreversible ionic block copolymers as templates in biomimetic nanocomposite synthesis using a bottom-up approach is a novel contribution in this respect. Further, we have extended these families of copolymers to include block copolymer-peptide conjugates to enhance biological specificity. Future directions on this work will focus on enhancing the polymer templating properties for biomineralization by expanding the family of block copolymers with organic polypeptides and biological polypeptide scaffolds as well as a detailed understanding of the polymer-inorganic nanocomposites at the molecular level using small angle scattering analysis. Glucose responsive polymer hydrogels for drug delivery, polymer-ligand conjugates for non-viral therapy and thermoresponsive injectable photocrosslinkable hydrogels for posttraumatic arthritis cartilage healing are other applications of these novel copolymers synthesized in our work.

  12. Characterization of recombinant human bone morphogenetic protein-2 delivery from injectable hyaluronan-based hydrogels by means of 125I-radiolabelling.

    PubMed

    Piskounova, Sonya; Gedda, Lars; Hulsart-Billström, Gry; Hilborn, Jöns; Bowden, Tim

    2014-10-01

    This study presents a thorough in vitro and in vivo characterization of the delivery of bone morphogenetic protein 2 (BMP-2) from a hyaluronan-based hydrogel system. The in vitro release of BMP-2 from similar hydrogels has previously been studied by enzyme-linked immunosorbent assay (ELISA), by which only a fraction of the loaded protein is detected. In the current study, (125) I radiolabelling was used instead to monitor BMP-2 in vitro and in vivo. To minimize protein loss during handling, (125) I-BMP-2 adsorption to different tubes was studied at different times and temperatures. The data showed that Protein LoBind tubes exhibited the lowest protein affinity. Furthermore, a biphasic release profile of biologically active BMP-2 was observed both in vitro and in vivo, with the initial fast phase during the first week, followed by a slower release during the remaining 3 weeks. The initial fast-release phase corresponded to the early bone formation observed after 8 days in an ectopic model in rats. Bone volume and mineral content increased until day 14, after which a decrease in bone volume was observed, possibly due to resorption in response to decreased amounts of released BMP-2. Overall, the results suggested that cautious protein handling and a reliable quantification technique are essential factors for successful design of a BMP-2 delivery system. PMID:22927307

  13. Green synthesis, characterization and evaluation of biocompatibility of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Ahamed, Maqusood; Majeed Khan, M. A.; Siddiqui, M. K. J.; AlSalhi, Mohamad S.; Alrokayan, Salman A.

    2011-04-01

    Although green synthesis of silver nanoparticles (Ag NPs) by various plants and microorganisms has been reported, the potential of plants as biological materials for the synthesis of nanoparticles and their compatibility to biological systems is yet to be fully explored. In this study, we report a simple green method for the synthesis of Ag NPs using garlic clove extract as a reducing and stabilizing agent. In addition to green synthesis, biological response of Ag NPs in human lung epithelial A549 cells was also assessed. Ag NPs were rapidly synthesized using garlic clove extract and the formation of nanoparticles was observed within 30 min. The green synthesized Ag NPs were characterized using UV-vis spectrum, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray energy-dispersive spectroscopy (EDX) and dynamic light scattering (DLS). Characterization data demonstrated that the particles were crystalline in nature and spherical shaped with an average diameter of 12 nm. Measurements of cell viability, cell membrane integrity and intracellular production of reactive oxygen species have shown that the green synthesized Ag NPs were nontoxic to human lung epithelial A549 cells. This study demonstrated a simple, cost-effective and environmentally benign synthesis of Ag NPs with excellent biocompatibility to human lung epithelial A549 cells. This preliminary in vitro investigation needs to be followed up by future studies with various biological systems.

  14. Enzyme Induced Formation of Monodisperse Hydrogel Nanoparticles Tunable in Size

    DOE PAGESBeta

    Bocharova, Vera; Sharp, Danna; Jones, Aaron; Cheng, Shiwang; Griffin, Philip J.; Agapov, Alexander L.; Voylov, Dmitry; Wang, Yangyang; Kisliuk, Alexander; Melman, Artem; et al

    2015-03-09

    Here, we report a novel approach to synthesize monodisperse hydrogel nanoparticles that are tunable in size. The distinctive feature of our approach is the use of a multicopper oxidase enzyme, laccase, as both a biocatalyst and template for nanoparticle growth. We utilize the ferroxidase activity of laccase to initiate localized production of iron(III) cations from the oxidation of iron(II) cations. We demonstrate that nanoparticles are formed in a dilute polymer solution of alginate as a result of cross-linking between alginate and enzymatically produced iron(III) cations. Exerting control over the enzymatic reaction allows for nanometer-scale tuning of the hydrogel nanoparticle radiimore » in the range of 30–100 nm. Moreover, the nanoparticles and their growth kinetics were characterized via dynamic light scattering, atomic force microscopy, and UV–vis spectroscopy. Our finding opens up a new avenue for the synthesis of tunable nanoscale hydrogel particles for biomedical applications.« less

  15. Preparation of hydrogels via ultrasonic polymerization.

    PubMed

    Cass, Peter; Knower, Warren; Pereeia, Eliana; Holmes, Natalie P; Hughes, Tim

    2010-02-01

    Several acrylic hydrogels were prepared via ultrasonic polymerization of water soluble monomers and macromonomers. Ultrasound was used to create initiating radicals in viscous aqueous monomer solutions using the additives glycerol, sorbitol or glucose in an open system at 37 degrees C. The water soluble additives were essential for the hydrogel production, glycerol being the most effective. Hydrogels were prepared from the monomers 2-hydroxyethyl methacrylate, poly(ethylene glycol) dimethacrylate, dextran methacrylate, acrylic acid/ethylene glycol dimethacrylate and acrylamide/bis-acrylamide. For example a 5% w/w solution of dextran methacrylate formed a hydrogel in 6.5min in a 70% w/w solution of glycerol in water at 37 degrees C with 20kHz ultrasound, 56Wcm(-2). The ultrasonic polymerization method described here has a wide range of applications such a biomaterial synthesis where initiators are not desired. PMID:19762267

  16. Synthesis and Characterization of β Nickel Niobate

    NASA Astrophysics Data System (ADS)

    Munsie, Timothy; Millington, Anna; Dabkowska, Hanna; Britten, Jim; Luke, Graeme

    2015-03-01

    Members of the niobate family (ANb2O6, A=Ni, Co, Fe, Mn) are known to crystallize in the columbite structure with zig-zag chains of the metallic and typically magnetic cation, giving rise to a quasi-one-dimensional magnetic system. In our attempts to synthesize NiNb2O6 in its columbite structure, we discovered a previously unreported allotrope, β-NiNb2O6, with a completely different crystalline structure, magnetic environment and magnetic properties. This talk will discuss the difficulties with respect to synthesis via the optical floating zone (OFZ) technique, the results of our structural refinement utilizing single crystal x-ray diffraction, and both magnetic and transport measurements of this materials physical properties.

  17. Synthesis and characterization of hybrid nanostructures

    PubMed Central

    Mokari, Taleb

    2011-01-01

    There has been significant interest in the development of multicomponent nanocrystals formed by the assembly of two or more different materials with control over size, shape, composition, and spatial orientation. In particular, the selective growth of metals on the tips of semiconductor nanorods and wires can act to couple the electrical and optical properties of semiconductors with the unique properties of various metals. Here, we outline our progress on the solution-phase synthesis of metal-semiconductor heterojunctions formed by the growth of Au, Pt, or other binary catalytic metal systems on metal (Cd, Pb, Cu)-chalcogenide nanostructures. We show the ability to grow the metal on various shapes (spherical, rods, hexagonal prisms, and wires). Furthermore, manipulating the composition of the metal nanoparticles is also shown, where PtNi and PtCo alloys are our main focus. The magnetic and electrical properties of the developed hybrid nanostructures are shown. PMID:22110873

  18. Black Phosphorus Nanosheets: Synthesis, Characterization and Applications.

    PubMed

    Eswaraiah, Varrla; Zeng, Qingsheng; Long, Yi; Liu, Zheng

    2016-07-01

    Black phosphorus (BP) is an emerging two-dimensional (2D) material with a natural bandgap, which has unique anisotropy and extraordinary physical properties. Due to its puckered structure, BP exhibits strong in-plane anisotropy unlike other layered materials. The bandgap tunability of BP enables a wide range of ultrafast electronics and high frequency optoelectronic applications ranging from telecommunications to thermal imaging covering the nearly entire electromagnetic spectrum, whereas no other 2D material has this functionality. Here, recent advances in the synthesis, fabrication, anisotropic physical properties, and BP-based devices including field effect transistors (FETs) and photodetectors, are discussed. Recent passivation approaches to address the degradation of BP, which is one of the main challenges to bring this material into real world applications, are also introduced. Finally, a comment is made on the recent developments in other emerging applications, future outlook and challenges ahead in BP research. PMID:27225670

  19. Gaseous detonation synthesis and characterization of nano-oxide

    NASA Astrophysics Data System (ADS)

    Yan, Honghao; Wu, Linsong; Li, Xiaojie; Wang, Xiaohong

    2015-07-01

    Gaseous detonation is a new method of heating the precursor of nanomaterials into gas, and integrating it with combustible gas as mixture to be detonated for the synthesis of nanomaterials. In this paper, the mixed gas of oxygen and hydrogen is used as the source for detonation, to synthesize nano TiO2, nano SiO2 and nano SnO2 through gaseous detonation method, characterization and analysis of the products, it was found that the products from gaseous detonation method were of high purity, good dispersion, smaller particle size and even distribution. It also shows that for the synthesis of nano-oxides, gaseous detonation is universal.

  20. Radiation synthesis of eco-friendly water reducing sulfonated starch/acrylic acid hydrogel designed for cement industry

    NASA Astrophysics Data System (ADS)

    Abd El-Rehim, H. A.; Hegazy, El-Sayed A.; Diaa, D. A.

    2013-04-01

    Starch was treated with chlorosulfonic acid to obtain sulfonated starch. Acrylic acid/sulfonated starch semi-interpenetrated network IPN of different compositions was prepared using ionizing radiation. Swelling of prepared IPNs at different environmental conditions was studied. The possible use of sulfonated starch/acrylic acid IPN as a water-retarding agent in the cement industry was investigated. ζ-potential measurements were used to determine the stability of the colloidal cement—SS/AA and cement -poly-naphthalene sulfonic acid (SNF) water retarding mixtures. Sulfonated starch/acrylic acid water-retarding property was influenced by hydrogel concentration and composition. Sulfonated starch/acrylic acid IPN admixture has a great effect on the cement initial setting time. Using 2% of SS/AA or SNF resulted in an increase in initial setting time by 2 and 1 h respectively, if compared with native cement initial setting time. The results showed that the synthetic commercial super-plasticizers could be replaced by an eco-friendly water-retarding sulfonated starch/acrylic acid IPN in the cement industry.

  1. Synthesis of cellulose-based superabsorbent hydrogels by high-energy irradiation in the presence of crosslinking agent

    NASA Astrophysics Data System (ADS)

    Fekete, Tamás; Borsa, Judit; Takács, Erzsébet; Wojnárovits, László

    2016-01-01

    Superabsorbent hydrogels were prepared from aqueous solutions of four cellulose derivatives (carboxymethylcellulose Na-salt - CMC, methylcellulose - MC, hydroxyethylcellulose - HEC and hydroxypropylcellulose - HPC) by gamma irradiation initiated crosslinking. CMC was used for the majority of the measurements. N,N'-methylene-bis-acrylamide (MBA) crosslinking agent was used to modify the gel properties. The crosslink density increased with the MBA concentration, leading to an improved gel fraction and lower water uptake. The crosslinking efficiency was the highest up to 1 w/wpolymer% MBA concentration. Very high MBA content (10 w/wpolymer%) led to a heterogeneous gel structure. Gelation also occurred under milder conditions in the presence of MBA: good gel properties were achieved at significantly lower doses and solute concentrations as compared to crosslinker-free solutions. The time required to reach maximum water uptake increased with the degree of swelling in equilibrium. Swelling properties of CMC gels with lower water uptake showed lower sensitivity to the ionic strength of the solvent.

  2. Anisotropic Gold Nanocrystals:. Synthesis and Characterization

    NASA Astrophysics Data System (ADS)

    Stiufiuc, R.; Toderas, F.; Iosin, M.; Stiufiuc, G.

    In this letter we report on successful preparation and characterization of anisotropic gold nanocrystals bio-synthesized by reduction of aqueous chloroaurate ions in pelargonium plant extract. The nanocrystals have been characterized by means of Transmission Electron Microscopy (TEM), UV-VIS absorption spectroscopy and tapping mode atomic force microscopy (TM-AFM). Using these investigation techniques, the successful formation of anisotropic single nanocrystals with the preferential growth direction along the gold (111) plane has been confirmed. The high detail phase images could give us an explanation concerning the growth mechanism of the nanocrystals.

  3. Synthesis and characterization of luminescent oxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Seo, Sooyeon

    Oxide nanocrystals with controlled geometries exhibit unique shape dependent optical and structural properties. Shape-controlled synthesis of rare earth doped gadolinium oxide (Gd2O3: Eu3+, Tb3+ or Er3+) and zinc gallate (ZnGa2O 4:Eu3+) nanocrystals by non-hydrolytic high temperature (˜300°C) methods are reported. Various shapes of Gd2O 3 nanocrystals were synthesized, including spheres and plates and advanced shapes such as curved rods and triangles. The nanocrystal shape was shown to be a function of the synthesis parameters, such as metal precursors (acetate, acetyl acetonate, chloride or octanoate) and surfactant type (tri-octyl phosphine oxide-TOPO, or hexadecanediol-HDD) and concentration (metal precursor: surfactant molar ratios of 1:2 to 1:5), as well as heating rate (5-25°C/min.) between pre-heat (200°C) and reaction (290°C) temperatures. The effects of these parameters upon nanocrystal shape were explained based on nucleation and growth of oxide nanocrystals. The photoluminescence intensity from Gd 2O3:Eu3+ was shown to increase as the concentration of dopant incorporated into the nanocrystals increased. The doping efficiency, defined to be the percentage of dopant incorporated into the nanocrystals, ranged from 0.57-6.1 mol%, was a function of shape of the Gd2O 3: Eu3 and was discussed in terms of the rate of reaction, product yield and crystal structure. To be used for labeling biomolecules such as DNA, RNA, or proteins, water soluble luminescent nanocrystals are required. Doped Gd2O 3 nanocrystals prepared by the non-hydrolytic hot solution method are hydrophobic and are not soluble in water due to organic surfactant encapsulation. A general strategy to convert hydrophobic luminescent nanocrystals (e.g. Gd 2O3) to water soluble particles by over-coating the hydrophobic surface with amphiphilic polymers is reported. Specifically, octylamine modified surfaces were coated with poly (acrylic acid) and water dispersions of Gd 2O3: Eu3+ were still

  4. Synthesis, Characteristics and Potential Application of Poly(β-Amino Ester Urethane)-Based Multiblock Co-Polymers as an Injectable, Biodegradable and pH/Temperature-Sensitive Hydrogel System.

    PubMed

    Huynh, Cong Truc; Nguyen, Minh Khanh; Jeong, In Ki; Kim, Sung Wan; Lee, Doo Sung

    2012-01-01

    Physical polymeric hydrogels have significant potential for use as injectable depot drug/protein-delivery systems. In this study, a series of novel injectable, biodegradable and pH/temperature-sensitive multiblock co-polymer physical hydrogels composed of poly(ethylene glycol) (PEG) and poly(β-amino ester urethane) (PEU) was synthesized by the polyaddition between the isocyanate groups of 1,6-diisocyanato hexamethylene and the hydroxyl groups of PEG and a synthesized monomer BTB (or ETE) in chloroform in the presence of dibutyltin dilaurate as a catalyst. The synthesized co-polymers were characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and gel-permeation chromatography. Aqueous solutions of the co-polymers showed a sol-to-gel phase transition with increasing pH and a gel-to-sol phase transition with increasing temperature. The gel regions covered the physiological conditions (37°C, pH 7.4) and could be controlled by changing the molecular weight of PEG, PEG/PEU ratio and co-polymer solution concentration. A gel formed rapidly in situ after injecting the co-polymer solution subcutaneously into SD rats and remained for more than 2 weeks in the body. The cytotoxicity tests confirmed the non-cytotoxicity of this co-polymer hydrogel. The controlled in vitro release of the model anticancer drug, doxorubicin, from this hydrogel occurred over a 7-day period. This hydrogel is a potential candidate for biomedical applications and drug/protein-delivery systems. PMID:21619729

  5. RF-interrogatable hydrogel-actuated biosensor

    SciTech Connect

    Hoel, Z; Wang, A W; Darrow, C B; Lee, A P; McConaghy, C F; Krulevitch, P; Gilman, A; Satcher, J H; Lane, S M

    2000-01-10

    The authors present a novel micromachined sensor that couples a swellable hydrogel with capacitive detection. The hydrogel swells in response to analyte concentration, exerting contact pressure on a deformable conducting membrane. Results are presented for characterization of a PHEMA hydrogel swelling in response to a calcium nitrate solution. Pressure-deflection measurements are performed on NiTi-based membranes. Hydrogel-actuated deflections of the membranes are measured. These measurements are correlated to determine the pressure generating characteristics of the hydrogel. Membrane deflection techniques have not previously been employed for hydrogel characterization. The PHEMA sample exhibited greatest sensitivity in the pH range of 6.0--6.5 and performed an average of 2.8 Joules of work per m{sup 3} per pH unit in response to ambient conditions over the pH range 3.5--6.5. The membrane deflections correspond to capacitive shifts of about 4 pF per pH unit for a capacitive transducer with initial gap of 100 {micro}m, capacitor plate area of 18.5 mm{sup 2} , and initial hydrogel volume of 11 {micro}L.

  6. Facile chemical synthesis and structure characterization of copper molybdate nanoparticles

    NASA Astrophysics Data System (ADS)

    Rahimi-Nasrabadi, Mehdi; Pourmortazavi, Seied Mahdi; Khalilian-Shalamzari, Morteza

    2015-03-01

    Experimental parameters of a synthesis route were optimized by Taguchi robust design for the facile and controllable synthesis of copper molybdate nanoparticles. CuMoO4 nanoparticles were synthesized by chemical precipitation followed by hydrothermal process. Effects of different parameters of synthesis procedure, i.e. concentrations of both reagents, copper feeding flow rate and temperature of reactor on the particle size of prepared copper molybdate nanoparticles were investigated. The results of statistical optimization revealed that the size of copper molybdate particles is dependent on the procedure variables involving copper concentrations, flow rate and temperature of the reactor; while, molybdate concentration has a no considerable role in determining the size of CuMoO4 particles. Based on the results obtained by statistical optimization process, the nanoparticles of copper molybdate were prepared and then their structure and chemical composition were characterized by various techniques, i.e. SEM, TEM, XRD, EDX, FT-IR, UV-Vis and photoluminescence spectroscopy.

  7. Magnetic and spectroscopic properties of Polyacrylamide-CoFe2O4 magnetic hydrogel

    NASA Astrophysics Data System (ADS)

    Alveroğlu, E.; Sözeri, H.; Kurtan, U.; Şenel, M.; Baykal, A.

    2013-03-01

    This study investigates synthesis and characterization of polyacrylamide (PAAm) hydrogels containing ferromagnetic CoFe2O4 nanoparticles. Structural, electrical, and magnetic characterization of the gels have been performed with X-ray powder diffractometry, Scanning electron microscopy, DC conductivity, magnetization and fluorescence spectroscopy techniques. Fluorescence and electrical measurements show that nanoparticles have trapped in the gel so they cannot move through the gel even if the gel is swollen and the voltage is applied. Pyranine molecules diffuse easily through the gel due to the presence of ferromagnetic nanoparticles. As number of diffused pyranine molecules increases current densities of the magnetic hydrogel increase. Magnetization measurements reveal that CoFe2O4 nanoparticles do not diffuse out of the gel during swelling. As a result, total magnetization of the gel do not change as volume of the gel increases.

  8. Synthesis and characterization of melanin in DMSO

    NASA Astrophysics Data System (ADS)

    Bronze-Uhle, Erika S.; Batagin-Neto, Augusto; Xavier, Pedro H. P.; Fernandes, Nicole I.; de Azevedo, Eduardo R.; Graeff, Carlos F. O.

    2013-09-01

    Recently soluble melanin derivatives have been obtained by a synthetic procedure carried out in DMSO (D-melanin). In this work a comparative study of the structural characteristics of synthetic melanin derivatives obtained by oxidation of L-DOPA in H2O and DMSO are presented. To this end, Fourier-transform infrared spectroscopy as well as proton and carbon nuclear magnetic resonance techniques has been employed. In addition, aging effects have been investigated for D-melanin. The results suggest that sulfonate groups (-SO2CH3) from the oxidation of DMSO, are incorporated into melanin, which confers protection to the phenolic hydroxyl group present in its structure. The solubility of D-melanin in DMSO is attributed to the presence of these groups. When D-melanin is left in air for long time periods, the sulfonate groups leave the structure, and an insoluble compound is obtained. NaOH and water have been used, in order to accelerate the release of the sulfonate groups attached to D-melanin, thereby corroborating the proposed structure and the synthesis mechanism.

  9. Synthesis Array Topology Metrics in Location Characterization

    NASA Astrophysics Data System (ADS)

    Shanmugha Sundaram, GA

    2015-08-01

    Towards addressing some of the fundamental mysteries in physics at the micro- and macro-cosm level, that form the Key Science Projects (KSPs) for the Square Kilometer Array (SKA; such as Probing the Dark Ages and the Epoch of Reionization in the course of an Evolving Universe; Galaxy Evolution, Cosmology, and Dark Energy; and the Origin and evolution of Cosmic Magnetism) a suitable interfacing of these goals has to be achieved with its optimally designed array configuration, by means of a critical evaluation of the radio imagingcapabilities and metrics. Of the two forerunner sites, viz. Australia and South Africa, where pioneering advancements to state-of-the-art in synthesis array radio astronomy instrumentation are being attempted in the form of pathfinders to the SKA, for its eventual deployment, a diversity of site-dependent topology and design metrics exists. Here, the particular discussion involves those KSPs that relate to galactic morphology and evolution, and explores their suitability as a scientific research goal from the prespective of the location-driven instrument design specification. Relative merits and adaptability with regard to either site shall be presented from invoking well-founded and established array-design and optimization principles designed into a customized software tool.

  10. Synthesis and Characterization of Injectable, Biodegradable, Phosphate-Containing, Chemically Cross-Linkable, Thermoresponsive Macromers for Bone Tissue Engineering

    PubMed Central

    2015-01-01

    Novel, injectable, biodegradable macromer solutions that form hydrogels when elevated to physiologic temperature via a dual chemical and thermo-gelation were fabricated and characterized. A thermogelling, poly(N-isopropylacrylamide)-based macromer with pendant phosphate groups was synthesized and subsequently functionalized with chemically cross-linkable methacrylate groups via degradable phosphate ester bonds, yielding a dual-gelling macromer. These dual-gelling macromers were tuned to have transition temperatures between room temperature and physiologic temperature, allowing them to undergo instantaneous thermogelation as well as chemical gelation when elevated to physiologic temperature. Additionally, the chemical cross-linking of the hydrogels was shown to mitigate hydrogel syneresis, which commonly occurs when thermogelling materials are raised above their transition temperature. Finally, degradation of the phosphate ester bonds of the cross-linked hydrogels yielded macromers that were soluble at physiologic temperature. Further characterization of the hydrogels demonstrated minimal cytotoxicity of hydrogel leachables as well as in vitro calcification, making these novel, injectable macromers promising materials for use in bone tissue engineering. PMID:24758298

  11. Synthesis and structural characterization of CZTS nanoparticles

    SciTech Connect

    Lydia, R.; Reddy, P. Sreedhara

    2013-06-03

    The CZTS nanoparticles were successfully synthesized by Chemical co-precipitation method with different pH values in the range of 6 to 8. The synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. XRD studies revealed that the CZTS nanoparticles exhibited Kesterite Structure with preferential orientation along the (112) direction. Sample at pH value of 7 reached the nearly stoichiometric ratio.

  12. Preparation of hyaluronic acid micro-hydrogel by biotin-avidin-specific bonding for doxorubicin-targeted delivery.

    PubMed

    Cui, Yuan; Li, Yanhui; Duan, Qian; Kakuchi, Toyoji

    2013-01-01

    Hyaluronic acid is a naturally ionic polysaccharide with cancer cell selectivity. It is an ideal candidate material for delivery of anticancer agents. In this study, hyaluronic acid (HA) micro-hydrogel loaded with anticancer drugs was prepared by the biotin-avidin system approach. Firstly, carboxyl groups on HA were changed into amino groups with adipic acid dihydrazide (ADH) to graft with biotin by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride named as HA-biotin. When HA-biotin solution mixed with doxorubicin hydrochloride (DOX·HCl) was blended with neutravidin, the micro-hydrogels would be formed with DOX loading. If excess biotin was added into the microgel, it would be disjointed, and DOX will be released quickly. The results of the synthesis procedure were characterized by (1)H-NMR and FTIR; ADH and biotin have been demonstrated to graft on the HA molecule. A field emission scanning electron microscope was used to observe morphologies of HA micro-hydrogels. Furthermore, the in vitro DOX release results revealed that the release behaviors can be adjusted by adding biotin. Therefore, the HA micro-hydrogel can deliver anticancer drugs efficiently, and the rate of release can be controlled by biotin-specific bonding with the neutravidin. Consequently, the micro-hydrogel will perform the promising property of switching in the specific site in cancer therapy. PMID:23179277

  13. Graphene synthesis and characterization on copper

    NASA Astrophysics Data System (ADS)

    Mohsin, Ali

    Graphene, two dimensional sheet of carbon atoms has recently gained attention as some of its properties are promising for electronics applications e.g. higher mobility that translates to higher operating frequency for devices geared towards radio frequency applications. Excellent optical transmittance combined with its semi metallic behavior makes it an important material for transparent contacts in solar cells. To bring graphene to the production level, synthesis methods are needed for its growth on wafer scale. It has been shown that chemical vapor deposition (CVD) is one of the techniques that can potentially synthesize wafer scale graphene. Recently copper has gained popularity as an important substrate material for graphene growth due to its lower carbon solubility, which allows better control over number of graphene layers. Here we report optimization of graphene growth on copper foils with our home made atmospheric pressure chemical vapor deposition (APCVD) setup. Graphene growth on copper under APCVD was non self-limiting similar to other reports. It was found that apart from growth parameters surface texture plays a very important role in graphene growth. In fact, few layer and bilayer graphene were obtained on the regions where copper surface was not uniform, confirmed by Raman spectroscopy. To improve copper surface texture thin layer of copper film was evaporated by electron beam evaporation before the graphene growth process. After this modification, monolayer graphene was obtained on areas as large as 300 microm x 300 microm confirmed by Raman area maps. Graphene transfer procedure was also optimized so that graphene on metal surface could be transferred to insulating substrate.

  14. Synthesis, characterization, and humidity sensing of metallophtalocyanines

    NASA Astrophysics Data System (ADS)

    Chakane, Sanjay D. S.; Jain, Shilpa; Bhoraskar, S. V.

    2001-03-01

    Metallophthalocyanines synthesized for different metals such as Ni, Cr, Ag, Mg, Cu, Cd, Al, etc by chemical methods were characterized with FTIR, UV etc. Sensing of humidity and different gases such as Nox, H2, O2, CO2, N2, ammonia, alcohol vapours etc were checked with 2-probe technique with monitoring change in resistance change. These samples have excellent stability against heat, light, air, and hence it has considerable attention for environmentally stable gas sensor. The electrical property of these samples were investigated at room temperature and at normal atmospheric pressure from low to 98% relative Humidity. It was observed that these samples shows good response and recovery for humidity sensing.

  15. Synthesis and characterization of aminated lignin.

    PubMed

    Pan, Hong; Sun, Gang; Zhao, Tao

    2013-08-01

    Amination of lignin can bring reactive amino groups onto the natural polymer and enable it to be employed in engineering materials. The amination reaction was successfully implemented after some of the hydroxyl groups on lignin were epoxidized. The resulted products showed a great quantity of primary amine group and secondary amine group which can be used as curing agents of epoxy resin. The results revealed that several factors including reaction temperature and time, as well as ratios of compounds, could influence the epoxidation and amination reactions. The resulted products were characterized by FT-IR spectra, (1)H NMR, (13)C NMR, element analysis, XPS and thermogravimetry analysis. PMID:23618954

  16. Preparation and characterization of pH-sensitive methyl methacrylate-g-starch/hydroxypropylated starch hydrogels: in vitro and in vivo study on release of esomeprazole magnesium.

    PubMed

    Kumar, Pankaj; Ganure, Ashok Laxmanrao; Subudhi, Bharat Bhushan; Shukla, Shubhanjali

    2015-06-01

    In the present study, novel hydrogels were prepared through graft copolymerization of methyl methacrylate onto starch and hydroxypropylated starch for intestinal drug delivery. The successful grafting has been confirmed by FTIR, NMR spectroscopy, and elemental analysis. Morphological examination of copolymeric hydrogels by scanning electron microscopy (SEM) confirms the macroporous nature of the copolymers. The high decomposition temperature was observed in thermograms indicating the thermal stability of the hydrogels. To attain a hydrogel with maximum percent graft yield, the impact of reaction variables like concentration of ceric ammonium nitrate as initiator and methyl methacrylate as monomer were consistently optimized. X-ray powder diffraction and differential scanning calorimetric analysis supported the successful entrapment of the drug moiety (esomeprazole magnesium; proton pump inhibitor) within the hydrogel network. Drug encapsulation efficiency of optimized hydrogels was found to be >78%. Furthermore, swelling capacity of copolymeric hydrogels exhibited a pH-responsive behavior which makes the synthesized hydrogels potential candidates for controlled delivery of medicinal agents. In vitro drug release was found to be sustained up to 14 h with 80-90% drug release in pH 6.8 solution; however, the cumulative release was 40-45% in pH 1.2. The gastrointestinal transit behavior of optimized hydrogel was determined by gamma scintigraphy, using (99m)Tc as marker. The amount of radioactive tracer released from the labeled hydrogel was minimal when the hydrogel was in the stomach, whereas it increased as hydrogel reached in intestine. Well-correlated results of in vitro and in vivo analysis proved their controlled release behavior with preferential delivery into alkaline pH environment. PMID:25787732

  17. Characterizing natural hydrogel for reconstruction of three-dimensional lymphoid stromal network to model T-cell interactions.

    PubMed

    Kim, Jiwon; Wu, Biming; Niedzielski, Steven M; Hill, Matthew T; Coleman, Rhima M; Ono, Akira; Shikanov, Ariella

    2015-08-01

    Hydrogels have been used in regenerative medicine because they provide a three-dimensional environment similar to soft tissues, allow diffusion of nutrients, present critical biological signals, and degrade via endogenous enzymatic mechanisms. Herein, we developed in vitro system mimicking cell-cell and cell-matrix interactions in secondary lymphoid organs (SLOs). Existing in vitro culture systems cannot accurately represent the complex interactions happening between T-cells and stromal cells in immune response. To model T-cell interaction in SLOs in vitro, we encapsulated stromal cells in fibrin, collagen, or fibrin-collagen hydrogels and studied how different mechanical and biological properties affect stromal network formation. Overall, fibrin supplemented with aprotinin was superior to collagen and fibrin-collagen in terms of network formation and promotion of T-cell penetration. After 8 days of culture, stromal networks formed through branching and joining with other adjacent cell populations. T-cells added to the newly formed stromal networks migrated and attached to stromal cells, similar to the T-cell zones of the lymph nodes in vivo. Our results suggest that the constructed three-dimensional lymphoid stromal network can mimic the in vivo environment and allow the modeling of T-cell interaction in SLOs. PMID:25649205

  18. Synthesis and characterization of nitrides of iridium and palladiums

    SciTech Connect

    Crowhurst, Jonathan C.; Goncharov, Alexander F.; Sadigh, B.; Zaug, J.M.; Aberg, D.; Meng, Yue; Prakapenka, Vitali B.

    2008-08-14

    We describe the synthesis of nitrides of iridium and palladium using the laser-heated diamond anvil cell. We have used the in situ techniques of x-ray powder diffraction and Raman scattering to characterize these compounds and have compared our experimental findings where possible to the results of first-principles theoretical calculations. We suggest that palladium nitride is isostructural with pyrite, while iridium nitride has a monoclinic symmetry and is isostructural with baddeleyite.

  19. Synthesis and characterization of responsive nanoporous materials

    NASA Astrophysics Data System (ADS)

    Abelow, Alexis Elizabeth

    This thesis describes the synthesis and properties of polymer or oligonucleotide-modified nanoporous membranes and nanopores which exhibit a response to external stimuli, synthesized with the intention of mimicking biological protein channels. The responsiveness of these systems arises as a function of the polymer or oligonucleotide modifier, which exhibit a change in conformation with exposure to temperature, pH, introduction of a small molecule, or electric potential. First, the transport of ions through supported silica colloidal films modified with poly(L-alanine) on platinum electrodes was studied using cyclic voltammetry. By monitoring the flux of a redox species through the polymer-modified colloidal film it is demonstrated that the polymer expands and contracts when the temperature was increased and decreased, respectively. We also observed an expansion and contraction as the pH was increased and decreased, respectively. Transport of a neutral dye molecule through free-standing silica colloidal films modified with poly(L-alanine) was also studied. As noted previously, the polymer expands and contracts as the pH is increased and decreased, respectively. Next, the transport was monitored through both silica colloidal film-modified Pt microelectrodes and Pt single nanopore electrodes as an oligonucleotide-based binder, or aptamer, was attached. The aptamer is responsive to a small molecule, cocaine where, in the absence of cocaine, only one "arm" of the aptamer is folded in on itself, leaving the rest of the chain partially unfolded, blocking the nanopores. However, when the cocaine molecule is introduced into solution, the aptamer folds completely in on itself, forming a three-armed structure with the small molecule encapsulated in the middle. This change in conformation is monitored by observing the change in transport of a redox species through the pores as cocaine is introduced into the system. We observed an increase rate of transport as the aptamer bound

  20. Synthesis, characterization and optical properties of nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Shoutian

    ZnO, Si, silica, Ge, Ga oxide, W oxide and Mo oxide nanoparticles have been synthesized and characterized, and their optical properties have been investigated. These particles were synthesized by a Laser Vaporization and Controlled Condensation (LVCC) technique in a modified diffusion cloud chamber. The particles deposited on smooth substrates reveal highly organized web-like structures with uniform micrometer size pores. The effect of solvents on the web-like structures was also investigated. ZnO nanoparticles were also prepared by wet chemical methods such as the reversed micelle and sol solutions technique. The photoluminescence quantum yield is enhanced 10 times once the surfaces of the ZnO nanoparticles are coated with a layer of stearate molecules. Many techniques have been used to characterize the nanoparticles. SEM gives information about particle size and morphology; X-ray diffraction and Raman spectroscopy determine the crystallinity and crystal structure; XPS and FTIR reveal the surface chemical composition; UV-vis spectroscopy and photoluminescence measurements characterize the optical properties of nanoparticles. Silica nanoparticles, prepared in an amorphous phase, show bright blue photoluminescence upon irradiation with UV light, but the luminescence has a very short lifetime (less than 20 ns). Si nanoparticles, with a diamond-like crystal phase, acquire oxidized-surfaces on exposure to air. The surface-oxidized Si nanocrystals show a short- lived blue emission characteristic of the SiO2 coating and a longer-lived red emission at room temperature. The lifetime of the red emission depends on the emission wavelength. Some substituted benzene molecules and tungsten oxide nanoparticles can quench the red photoluminescence of the Si nanocrystals. Tungsten oxide and molybdenum oxide nanoparticles show photochromic properties: they change color to blue when irradiated. The photons drive a transition from one chemical state to another. The color change of

  1. One-pot synthesis of 3-dimensional reduced graphene oxide-based hydrogel as support for microbe immobilization and BOD biosensor preparation.

    PubMed

    Liu, Ling; Zhai, Junfeng; Zhu, Chengzhou; Gao, Ying; Wang, Yue; Han, Yanchao; Dong, Shaojun

    2015-01-15

    We report a hydrothermal method to prepare reduced graphene oxide (rGO)-based hydrogel (Gel(rGONR)), using neutral red (NR) to mediate the assembly of rGO sheets and tune the pore size of Gel(rGONR). A series of techniques including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and BET were employed to characterize the physico-chemical properties of Gel(rGONR). A large pore size of up to 20 µm and interconnected porous structure of Gel(rGONR) were obtained. Gel(rGONR) was used as a support for immobilizing microbe (denoted as Gel(rGONR-M)), which showed ~3.3 times more load mass of microbe than commonly used supports (i.e., activated carbon and carbon fiber felt) and 2.5 times higher biodegradation efficiency (BE) than carbon fiber felt. Further use of Gel(rGONR-M) as a biocatalyst for establishing a BOD biosensor exhibits a linear range of 2-64 mg O L(-1) and a detection limit 0.4 mg O L(-1) for glucose-glutamic acid (GGA). Moreover, our proposed BOD detection strategy shows a long-term viability over one year and stability up to 2 months with a relative standard deviation of 2.1%. Our results demonstrated the great potential of employing Gel(rGONR) as a microbe-immobilization support for biosensor development. PMID:25129511

  2. Synthesis and characterization of biocompatible magnetic glyconanoparticles

    NASA Astrophysics Data System (ADS)

    Kekkonen, Viktoria; Lafreniere, Nelson; Ebara, Mitsuhiro; Saito, Atsuhiro; Sawa, Yoshiki; Narain, Ravin

    2009-05-01

    Magnetic glyconanoparticles were synthesized via the co-precipitation method. Iron (II) and iron (III) chloride were co-precipitated out of solution by the addition of ammonium hydroxide in an aqueous solution containing carbohydrate stabilizers such as D-gluconic acid, lactobionic acid and Ficoll ® at 75-80 °C. Stable magnetic glyconanoparticles were formed in a simple and direct process. Dynamic light scattering and transmission electron microscopy were used to characterize the surface-coated magnetic nanoparticles. In vitro cell viability studies of the glyconanoparticles were conducted with the mouse fibroblast cell lines. The magnetic glyconanoparticles revealed to be non-toxic at a concentration as high as 0.1 mg/mL.

  3. Synthesis and characterization of tannin grafted polycaprolactone.

    PubMed

    Song, Ping; Jiang, Suchen; Ren, Yajun; Zhang, Xue; Qiao, Tiankui; Song, Xiaofeng; Liu, Qimin; Chen, Xuesi

    2016-10-01

    Tannin and biodegradable polyester have attracted increasing interest for biomedical applications. To improve their compatibility, a novel tannin grafted polycaprolactone (TA-g-PCL) has been synthesized via ring-opening polymerization reaction. The structure of the product is characterized with FTIR, (1)H NMR and GPC. GPC results show that the experimental molecular weight is far less than the theoretical due to complicated stereo structure and large steric hindrance of tannic molecule, but the polydispersity of the product is narrow. At 115.76:1 of molar ratio of CL to tannin, molecular weight of the product reaches the maximum. Thermodynamics properties and dissolubility of TA-g-PCL are closely related to its molecular weight. With PCL molecular chain grows, TA-g-PCL changes from amorphous form to crystalline structure, and its dissolubility in chloroform is also enhanced significantly. PMID:27388129

  4. Synthesis and Characterization of New Topological Insulators

    NASA Astrophysics Data System (ADS)

    Segawa, Kouji

    2012-02-01

    In this talk, I will show detailed information on synthesizing process and characterization results of new topological insulator (TI) materials with interesting properties. Among the synthesized materials, TlBiSe2 was the first ternary TI and has the largest bulk band gap [1], TlBi(S1-x,Sex)2 presents a topological phase transition with unexpected Dirac mass [2], BiTe2Se presents a large bulk resistivity [3], and Bi1.5Sb0.5Te1.7Se1.3 has finally achieved the surface-dominated transport in bulk single crystals [4]. It is essentially easy to grow single crystals of all the chalcogenides above, because those compounds melt congruently at relatively low temperatures. Therefore, the melt-growth method is applicable if the raw materials are in a sealed condition, e.g., in a quartz tube. However, crucial techniques for obtaining high-quality samples vary between the systems. Besides the growth method, characterizations of the transport properties, ARPES, the X-ray diffraction, and quantitative chemical analysis will also be presented. [4pt] This work is in collaboration with A. A. Taskin, S. Sasaki, Zhi Ren, K. Eto, T. Minami, and Y. Ando (Osaka Univ.), and T. Sato, S. Souma, H. Guo, K. Sugawara, K. Kosaka and K. Nakayama, and T. Takahashi (Tohoku Univ.). [4pt] [1] T. Sato, Kouji Segawa, T. Takahashi, Y. Ando et al., Phys. Rev. Lett. 105, 136802 (2010). [2] T. Sato, Kouji Segawa, Y. Ando, T. Takahashi et al., Nature Physics, 7, 840 (2011). [3] Zhi Ren, Kouji Segawa, Y. Ando et al., Phys. Rev. B (Rapid Comm.) 82, 241306(R) (2010). [4] A. A. Taskin, Kouji Segawa, and Y. Ando et al., Phys. Rev. Lett. 107, 016801 (2011).

  5. Synthetic Biodegradable Hydrogels with Excellent Mechanical Properties and Good Cell Adhesion Characteristics Obtained by the Combinatorial Synthesis of Photo-Cross-Linked Networks.

    PubMed

    Zant, Erwin; Grijpma, Dirk W

    2016-05-01

    Major drawbacks of synthetic hydrogels are their poor mechanical properties and their limited ability to allow cell attachment and proliferation. By photo-cross-linking mixtures of dimethacrylate-functionalized oligomers (macromers) in a combinatorial manner in solution, synthetic hydrogels with high water uptake and the remarkable ability to promote cell adhesion and proliferation were prepared. A total of 255 different networks based on poly(trimethylene carbonate) (PTMC)-, poly(d,l-lactide) (PDLLA)-, poly(ε-caprolactone) (PCL)- and poly(ethylene glycol) (PEG) macromers were synthesized simultaneously and screened for their ability to allow the adhesion of human mesenchymal stem cells (hMSCs) in a high throughput-like manner. Of these networks, several hydrogels could be identified that were able to take up large amounts of water while at the same time allowed the adhesion of cells. By synthesizing these hydrogel networks anew and analyzing the cell adhesion and proliferation behavior of human mesenchymal stem cells to these synthetic hydrogels in more detail, it was confirmed that mixed-macromer hydrogel networks prepared from equal amounts of PTMC-dMA 4k, PDLLA-dMA 4k, PCL-dMA 4k, PEG-dMA 4k, and PEG-dMA 10k and hydrogel networks prepared from PTMC-dMA 4k, PDLLA 4k, PEG-dMA 4k, PTMC-dMA 10k and PEG-dMA 10k were highly hydrophilic (water uptake was respectively 181 ± 2 and 197 ± 18 wt % water) and allowed very good cell adhesion and proliferation. Furthermore, these networks were extremely resilient in the hydrated state, with tearing energies of respectively 0.64 ± 0.34 and 0.27 ± 0.04 kJ/m(2). This is much higher than other synthetic hydrogels described in literature and close to articular cartilage (1 kJ/m(2)). PMID:27077699

  6. Radiation-induced synthesis and swelling properties of p(2-hydroxyethyl methacrylate/itaconic acid/oligo (ethylene glycol) acrylate) terpolymeric hydrogels

    NASA Astrophysics Data System (ADS)

    Micic, M.; Stamenic, D.; Suljovrujic, E.

    2012-09-01

    Since it is presumed that by incorporation of pH-responsive (IA) and temperature-responsive (OEGA) co-monomers, it is possible to prepare P(HEMA/IA/OEGA) hydrogels with dual (pH and thermo) responsiveness, the main purpose of our study is to investigate the influence of different mole fractions of IA and especially OEGA on the diversity of the swelling properties of the obtained hydrogels. For that reason, a series of terpolymeric hydrogels with different mole ratios of 2-hydroxyethyl methacrylate (HEMA), itaconic acid (IA) and oligo(ethylene glycol) acrylates (OEGA) was synthesised by gamma radiation. The obtained hydrogels were characterised by swelling studies in the wide pH (2.2-9.0) and temperature range (20-70 °C), confirming dual (pH and thermo) responsiveness and a large variation in the swelling capability. It was observed that the equilibrium swelling of P(HEMA/IA/OEGA) hydrogels, for a constant amount of IA, increased progressively with an increase in OEGA share. On the other hand, the dissociation of carboxyl groups from IA occurs at pH>4; therefore, small mole fractions of IA render good pH sensitivity and a large increase in the swelling capacity of these hydrogels at higher pH values. Additional characterisation of structure and properties was conducted by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and mechanical measurements, confirming that the inherent properties of P(HEMA/IA/OEGA) hydrogels can be significantly tuned by variation in their composition. According to all presented, it seems that the obtained hydrogels can be a beneficial synergetic combination for controlled delivery of bioactive molecules such as drugs, peptides, proteins, etc.

  7. Antifungal hydrogels

    PubMed Central

    Zumbuehl, Andreas; Ferreira, Lino; Kuhn, Duncan; Astashkina, Anna; Long, Lisa; Yeo, Yoon; Iaconis, Tiffany; Ghannoum, Mahmoud; Fink, Gerald R.; Langer, Robert; Kohane, Daniel S.

    2007-01-01

    Fungi are increasingly identified as major pathogens in bloodstream infections, often involving indwelling devices. Materials with antifungal properties may provide an important deterrent to these infections. Here we describe amphogel, a dextran-based hydrogel into which amphotericin B is adsorbed. Amphogel kills fungi within 2 h of contact and can be reused for at least 53 days without losing its effectiveness against Candida albicans. The antifungal material is biocompatible in vivo and does not cause hemolysis in human blood. Amphogel inoculated with C. albicans and implanted in mice prevents fungal infection. Amphogel also mitigates fungal biofilm formation. An antifungal matrix with these properties could be used to coat a variety of medical devices such as catheters as well as industrial surfaces. PMID:17664427

  8. Rheological properties of peptide-based hydrogels for biomedical and other applications†

    PubMed Central

    Yan, Congqi; Pochan, Darrin J.

    2011-01-01

    Peptide-based hydrogels are an important class of biomaterials finding use in food industry and potential use in tissue engineering, drug delivery and microfluidics. A primary experimental method to explore the physical properties of these hydrogels is rheology. A fundamental understanding of peptide hydrogel mechanical properties and underlying molecular mechanisms is crucial for determining whether these biomaterials are potentially suitable for biotechnological uses. In this critical review, we cover the literature containing rheological characterization of the physical properties of peptide and polypeptide-based hydrogels including hydrogel bulk mechanical properties, gelation mechanisms, and the behavior of hydrogels during and after flow. PMID:20422104

  9. Synthesis and characterizations of novel polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Chanthad, Chalathorn

    Polymer electrolytes are an important component of many electrochemical devices. The ability to control the structures, properties, and functions of polymer electrolytes remains a key subject for the development of next generation functional polymers. Taking advantage of synthetic strategies is a promising approach to achieve the desired chemical structures, morphologies, thermal, mechanical, and electrochemical properties. Therefore, the major goal of this thesis is to develop synthetic methods for of novel proton exchange membranes and ion conductive membranes. In Chapter 2, new classes of fluorinated polymer- polysilsesquioxane nanocomposites have been designed and synthesized. The synthetic method employed includes radical polymerization using the functional benzoyl peroxide initiator for the telechelic fluorinated polymers with perfluorosulfonic acids in the side chains and a subsequent in-situ sol-gel condensation of the prepared triethoxylsilane-terminated fluorinated polymers with alkoxide precursors. The properties of the composite membranes have been studied as a function of the content and structure of the fillers. The proton conductivity of the prepared membranes increases steadily with the addition of small amounts of the polysilsesquioxane fillers. In particular, the sulfopropylated polysilsesquioxane based nanocomposites display proton conductivities greater than Nafion. This is attributed to the presence of pendant sulfonic acids in the fillers, which increases ion-exchange capacity and offers continuous proton transport channels between the fillers and the polymer matrix. The methanol permeability of the prepared membranes has also been examined. Lower methanol permeability and higher electrochemical selectivity than those of Nafion have been demonstrated in the polysilsesquioxane based nanocomposites. In Chapter 3, the synthesis of a new class of ionic liquid-containing triblock copolymers with fluoropolymer mid-block and imidazolium methacrylate

  10. Synthesis and characterization of thermoplastic polyphenoxyquinoxalines

    NASA Astrophysics Data System (ADS)

    Erdem, Haci Bayram

    This research was divided into two main parts. In the first part, a new facile route to relatively inexpensive thermoplastic polyphenoxyquinoxalines was developed. The synthetic route involves the aromatic nucleophilic substitution reaction of bisphenols with 2,3-dichloroquinoxaline. The dichloro monomer was prepared in two steps. In the first step, oxalic acid was condensed with o-phenylenediamine to give 2,3-dihydroxyquinoxaline. In the second step, 2,3-dihydroxyquinoxaline was treated with thionyl chloride to give 2,3-dichloroquinoxaline. This monomer was successfully polymerized with bisphenol-A, bisphenol-S, hexafluorobisphenol-A and 9,9-bis(4-hydroxyphenyl)fluorenone. Hydroquinone and biphenol, however, can not be polymerized to high molecular weight polymers because of the premature precipitation of crystalline oligomers. The glass transition temperatures of the high molecular weight polymers prepared from a series of bisphenols range from 191 °C to 279 °C, and their thermal decomposition temperatures are around 500 °C. The polymers are soluble in a wide range of solvents and can be solution-cast into thin films that are colorless and transparent. The polymers have tensile strengths ranging from 61 to 107 MPa, and tensile moduli ranging from 3.5 to 2.3 GPa. The synthesis of polymer obtained from 2,3-dichloroquinoxaline and bisphenol-A was scaled up to afford 500 g of material. This polymer is a thermoplastic with a melt-viscosity less than 1000 Pa.s. at 300 °C. The notched Izod impact strength of injection-molded samples of this polymer is 40.7 J/m. In the second part of this research, the synthetic method has been modified to allow the preparation of quinoxaline containing polyimides. Thus, 2,3-dichloroquinoxaline was treated either with p-nitrophenol followed by reduction of nitro groups, or with p-aminophenols to directly obtain the desired 2,3-(4-aminophenoxy)quinoxaline. This diamine was polymerized with 3,3',4,4'-biphenyldianhydride, 4

  11. Synthesis of "click" alginate hydrogel capsules and comparison of their stability, water swelling, and diffusion properties with that of Ca(+2) crosslinked alginate capsules.

    PubMed

    Breger, Joyce C; Fisher, Benjamin; Samy, Raghu; Pollack, Steven; Wang, Nam Sun; Isayeva, Irada

    2015-07-01

    Ionically crosslinked alginate hydrogels have been extensively explored for encapsulation and immunoisolation of living cells/tissues to develop implantable cell therapies, such as islet encapsulation for bioartificial pancreas. Chemical instability of these hydrogels during long-term implantation hinders the development of viable cell therapy. The exchange between divalent crosslinking ions (e.g., Ca(+2) ) with monovalent ions from physiological environment causes alginate hydrogels to degrade, resulting in exposure of the donor tissue to the host's immune system and graft failure. The goal of this study was to improve stability of alginate hydrogels by utilizing covalent "click" crosslinking while preserving other biomedically viable hydrogel properties. Alginate was first functionalized to contain either pendant alkyne or azide functionalities, and subsequently reacted via "click" chemistry to form "click" gel capsules. Alginate functionalization was confirmed by NMR and gel permeation chromatography. When compared with Ca(+2) capsules, "click" capsules exhibited superior stability in ionic media, while showing higher permeability to small size diffusants and similar molecular weight cut-off and water swelling. Physicochemical properties of "click" alginate hydrogels demonstrate their potential utility for therapeutic cell encapsulation and other biomedical applications. PMID:25286444

  12. The effect of calcium chloride concentration on alginate/Fmoc-diphenylalanine hydrogel networks.

    PubMed

    Çelik, Ekin; Bayram, Cem; Akçapınar, Rümeysa; Türk, Mustafa; Denkbaş, Emir Baki

    2016-09-01

    Peptide based hydrogels gained a vast interest in the tissue engineering studies thanks to great superiorities such as biocompatibility, supramolecular organization without any need of additional crosslinker, injectability and tunable nature. Fmoc-diphenylalanine (FmocFF) is one of the earliest and widely used example of these small molecule gelators that have been utilized in biomedical studies. However, Fmoc-peptides are not feasible for long term use due to low stability and weak mechanical properties at neutral pH. In this study, Fmoc-FF dipeptides were mechanically enhanced by incorporation of alginate, a biocompatible and absorbable polysaccharide. The binary hydrogel is obtained via molecular self-assembly of FmocFF dipeptide in alginate solution followed by ionic crosslinking of alginate moieties with varying concentrations of calcium chloride. Hydrogel characterization was evaluated in terms of morphology, viscoelastic moduli and diffusional phenomena and the structures were tested as 3D scaffolds for bovine chondrocytes. In vitro evaluation of scaffolds lasted up to 14days and cell viability, sulphated glycosaminoglycan (sGAG) levels, collagen type II synthesis were determined. Our results showed that alginate incorporation into FmocFF hydrogels leads to better mechanical properties and higher stability with good biocompatibility. PMID:27207058

  13. Synthesis and characterization of chitosan alkyl urea.

    PubMed

    Wang, Jing; Jiang, Ji-Zhou; Chen, Wei; Bai, Zheng-Wu

    2016-07-10

    Chitosan is a versatile material employed for various purposes in many fields including the development of chiral stationary phases for enantioseparation. Chitosan alkyl urea is a kind of intermediate used to prepare enantioseparation materials. In order to synthesize the intermediates, in the present work, a new way to prepare chitosan alkyl urea has been established: chitosan was first reacted with methyl chloroformate yielding N-methoxyformylated chitosan, which was then converted to chitosan alkyl urea through amine-ester exchange reaction. With a large excess of methyl chloroformate and primary amine of low stereohindrance, the amino group in chitosan could be almost completely converted to ureido group. The as-prepared chitosan alkyl urea derivatives were characterized by IR, (1)H NMR, (13)C NMR,(1)H-(1)H COSY and (1)H-(13)C HSQC NMR spectra. The chemical shifts of hydrogen and carbon atoms of glucose unit were assigned. It was found that the degree of substitution was obviously lower if cyclopropyl amine, aniline, tert-butyl amine and diethyl amine were used as reactants for the amine-ester exchange reaction. The reason was explained with the aid of theoretical calculations. PMID:27106154

  14. Polypeptide Grafted Hyaluronan: Synthesis and Characterization

    SciTech Connect

    Wang, Xiaojun; Messman, Jamie M; Mays, Jimmy; Baskaran, Durairaj

    2010-01-01

    Poly(L-leucine) grafted hyaluronan (HA-g-PLeu) has been synthesized via a Michael addition reaction between primary amine terminated poly(L-leucine) and acrylate-functionalized HA (TBAHA-acrylate). The precursor hyaluronan was first functionalized with acrylate groups by reaction with acryloyl chloride in the presence of triethylamine in N,N-dimethylformamide. 1H NMR analysis of the resulting product indicated that an increase in the concentration of acryloylchoride with respect to hydroxyl groups on HA has only a moderate effect on functionalization efficiency, f. A precise control of stoichiometry was not achieved, which could be attributed to partial solubility of intermolecular aggregates and the hygroscopic nature of HA. Michael addition at high [PLeu- NH2]/[acrylate]TBAHA ratios gave a molar grafting ratio of only 0.20 with respect to the repeat unit of HA, indicating grafting limitation due to insolubility of the grafted HA-g-PLeu. Soluble HA-g-PLeu graft copolymers were obtained for low grafting ratios (<0.039) with <8.6% by mass of PLeu and were characterized thoroughly using light scattering, 1H NMR, FT-IR, and AFM techniques. Light scattering experiments showed a strong hydrophobic interaction between PLeu chains, resulting in aggregates with segregated nongrafted HA segments. This yields local networks of aggregates, as demonstrated by atomic force microscopy. Circular dichroism spectroscopy showed a -sheet conformation for aggregates of poly(L-leucine).

  15. Synthesis and optical characterization of interactive nanosystems

    NASA Astrophysics Data System (ADS)

    Yasmin, Zannatul

    The use of interactive nanosystems (INSs) has unique advantages in sensing applications. Due to their multivalent interactions and stimuli responsiveness i.e. chemical, optical, pH, these adaptive networks can enhance sensing applications. In this work, two distinct INSs are synthesized and the interparticle interactions are probed optically. One of them is the gold nanoparticles based INS in presence of the biomolecule, glutathione. Their unique optical properties and surface binding affinity to thiol-containing glutathione provide an intriguing opportunity to probe bio-systems. The second one is the rare earth oxides/fluorides conjugated with gold nanoparticles based INS which exhibit tunabilty in their multi-wavelength absorbance and emission through coupling with the surface plasmon resonance of gold nanoparticles. The conjugation of these two interactive particles is uniquely synthesized in the presence of the bio-polymer chitosan. This structure displays tunable optical properties. The two novel INSs presented are characterized through their optical signatures using various spectroscopies including a novel approach developed in this work that comprises an all optical photoacoustic spectroscopy (AOPAS). The AOPAS technique is used to determine the unique characteristics of these INSs in aqueous environments by measuring their optical properties in situ. Additionally, we expect the AOPAS technique will provide unique information about nano-bio interfaces and the usefulness of INS as sensors in biological systems without the artifacts limiting the use of current methods, such as fluorescence-based indicators.

  16. Synthesis and characterization of luminescence magnetic nanocomposite

    NASA Astrophysics Data System (ADS)

    Kiplagat, Ayabei; Onani, Martin O.; Meyer, Mervin; Akenga, Teresa A.; Dejene, Francis B.

    2016-01-01

    We report a new type of indium based quantum dots which were conjugated to the magnetic Fe2O3 nanoparticles. They were characterized by photoluminescence (PL), high resolution transmission electron microscopy (HRTEM), superconducting quantum interference device (SQUID) and fourier transform infra-red (FTIR). The photoluminescence characteristics of the coupled and uncoupled indium based quantum dots were investigated to determine whether the fluorescing property could be retained in the bifunctional system. Generally, the PL intensity of the quantum dots was observed to reduce significantly and with huge red shift most probably due to quenching effects for the MNPs. The average size of the coupled nanoparticles were found to range between 4 and 5 nm for the quantum dots and range of 6-13 nm for the Fe2O3 magnetic nanoparticles as revealed by both HRTEM and XRD. The highest magnetic saturation reached for both bare and functionalized magnetic nanoparticles was 68.58 emu/g. The FTIR data revealed that the postulated functional groups were actually present in both the bare and functionalized nanoparticles. For instance, Fe-O was observed at around 580 cm-1, O-H at 3432 cm-1 and thiol group at 2929 cm-1 for meso-2,3-dimercaptosuccinic acid capped Fe2O3 magnetic nanoparticles. The energy dispersive spectroscopy (EDS) also confirmed that all the elements of the nanocomposite were actually present in the designed material.

  17. Glyconanomaterials: Synthesis, Characterization, and Ligand Presentation

    PubMed Central

    Wang, Xin

    2010-01-01

    Glyconanomaterials, nanomaterials carrying surface-tethered carbohydrate ligands, have emerged and demonstrated increasing potential in biomedical imaging, therapeutics, and diagnostics. These materials combine the unique properties of nanometer-scale objects with the ability to present multiple copies of carbohydrate ligands, greatly enhancing the weak affinity of individual ligands to their binding partners. Critical to the performance of glyconanomaterials is the proper display of carbohydrate ligands, taking into consideration of the coupling chemistry, the type and length of the spacer linkage, and the ligand density. This article provides an overview of the coupling chemistry for attaching carbohydrate ligands to nanomaterials, and discusses the need for thorough characterization of glyconanomaterials, especially quantitative analyses of the ligand density and binding affinities. Using glyconanoparticles synthesized by a versatile photocoupling chemistry, methods for determining the ligand density by colorimetry and the binding affinity with lectins by a fluorescence competition assay are determined. The results show that the multivalent presentation of carbohydrate ligands significantly enhances the binding affinity by several orders of magnitude in comparison to the free ligands in solution. The effect is sizeable even at low surface ligand density. The type and length of the spacer linkage also affect the binding affinity, with the longer linkage promoting the association of bound ligands with the corresponding lectins. PMID:20301131

  18. Synthesis and characterization of struvite nano particles

    NASA Astrophysics Data System (ADS)

    Rathod, K. R.; Jogiya, B. V.; Chauhan, C. K.; Joshi, M. J.

    2015-06-01

    Struvite, Ammonium Magnesium Phosphate Hexahydrate [(AMPH) - (NH4)MgPO4.6(H2O)], is one of the fascinating inorganic phosphate minerals. Struvite is one of the components of the urinary stones. Struvite occurs as crystallites in urine and grows as a type of kidney stone. In this study, struvite nano particles were synthesized by wet chemical technique. The aqueous solutions containing dissolved Mg(CH3COO)2.4H2O and (NH4)H2PO4 mixed at the Mg/P molar ratio of 1.00. The synthesized struvite nano particles were characterized by XRD, FT-IR, Thermal Analysis and TEM. From XRD, crystal structure of the nano particle was found to be orthorhombic and crystalline size was found to be within 11 to 26 nm. The FT-IR spectrum for the struvite nano particles confirmed the presence of a water molecule and metal-oxygen stretching vibration, O-H stretching and bending, N-H bending and stretching, P-O bending and stretching vibrations. The Thermal Analysis was carried out from room temperature to 900°C. From TEM analysis, particle size was 23 to 30 nm. All the results were compared with bulk struvite.

  19. Terpolymer smart gels: synthesis and characterizations

    NASA Astrophysics Data System (ADS)

    Bag, Dibyendu S.; Alam, Sarfaraz; Mathur, G. N.

    2004-10-01

    Two smart terpolymer gels, MS-1 and MS-2, were synthesized such that the same gel can respond to more than one external environmental condition, such as pH, temperature, solvent composition, electric field. So two terpolymers gels of vinyl monomers such as sodium acrylate, acrylamide and N-isopropyl acrylamide were synthesized by using ammonium persulfate (APS) as an initiator, N,N,N',N'-tetramethyl ethylene diamine (TMEDA) as an accelerator and methylene bisacrylamide as a cross-linker. These terpolymers were characterized by elemental and Fourier transform infrared analysis. The swelling behavior of these terpolymer smart gels was evaluated by changing the pH, temperature and solvent composition. The variation of the swelling behavior with time was evaluated in an aqueous medium at room temperature. The time taken for maximum swelling (tm) was about 20 min for the gel MS-2. However the tm value for the gel MS-1 is higher than that of MS-2. The swelling behavior remains almost unchanged over a temperature range of 22-50 °C for both the gels. The discontinuous volume transitions were observed at pH 7.6 and 8.2 for the two gels, MS-1 and MS-2, respectively. The gel MS-1 suddenly shrinks below and swells above pH 7.6. Correspondingly, the pH is 8.2 for the case of MS-2. Volume transitions in an acetone-water mixture were also observed for these gels. The swelling behaviors of these two smart gels are almost parallel above the 40% acetone concentration.

  20. Synthesis and characterization of diatom inspired nanocomposites

    NASA Astrophysics Data System (ADS)

    Gutu, Timothy

    This dissertation addresses the investigation of two novel methods to synthesize composite nanomaterials inspired by marine microalgae called diatoms. Diatoms are inspirational sources of silica structures, ordered at micro- to nanoscale, that possess unique optical properties. The fabrication of nanomaterials with well-defined and controllable micro-to nanoscale features has been of great interest for chemical, optical, electronic, catalytic, environmental, and medical applications. While bottom-up and top-down approaches have been extensively used to fabricate two-dimensional structures and devices, there is a need for inexpensive methods to mass-produce complex micro- to nanoscale structures with a variety of three-dimensional (3D) morphologies at high degrees of precision, reproducibility, and chemical tailorability. To explore the fabrication of 3D nanostructures, this study harnessed the biomineralization capacity of diatom cell cultures to fabricate Si-Ge oxide nanocomposites on one hand and the chemical bath deposition on the other hand. A two-stage photobioreactor strategy was used to metabolically insert nanostructured germanium into the silica microstructure of diatom of diatom Pinnularia sp. In the first stage, diatom cells were grown to the point of silicon starvation. In the second stage, a pulse of silicon and germanium solution was added to the silicon-starved cells. Various electron microscopy techniques were utilized to validate the extent of the insertion and the subsequent incorporation of germanium into the diatom silica matrix. In the second method to form diatom inspired nanocomposites, we utilize a simple, inexpensive chemical bath deposition technique to deposit a cadmium sulfide nanocrystals on the patterned surface of diatom biosilica. A parametric investigation of the factors affecting the chemical bath process was carried out. The morphology, structural and compositional properties of the composites were characterized by electron

  1. Synthesis and characterization of nanocrystalline silicide compounds

    SciTech Connect

    Karen, B.

    1992-01-03

    This thesis involves the investigation into the production of nanocrystalline silicide compounds by radio frequency inductively coupled plasma (RF-ICP) and mechanical milling. A system constructed which utilized a RF-ICP, a powder feed system and a condensation / collection chamber to produce nanocrystalline materials. Several silicides, such as Ti{sub 5}Si{sub 3}, Cr{sub 3}Si and MoSi{sub 2}, were fed into the plasma were they vaporized. The vaporized material then passed into a connecting chamber, where it condensed out of the vapor phase and the resulting powder was collected. Much of the work conducted was in designing and building of the systems components. This was followed by establishing the plasmas operating parameters. The material collected from the ICP chamber was then compared to material produced by mechanical milling. The material produced by both methods were characterized by x-ray diffraction, scanning and transmission-electron microscopy, and energy dispersive spectroscopy. The results indicate that it is possible to produce nanocrystalline material by mechanical milling; however, there is a significant amount of contamination from the milling ball and milling container. The results also show that the Ti{sub 5}Si{sub 3} and Cr{sub 3}Si compounds can be produced in nanocrystalline form by the ICP method. The resultant material collected from the ICP chamber following the MoSi{sub 2} run consisted of nanocrystalline Si and crystalline, Mo rich Si compound. Inductively coupled plasma - atomic emission spectroscopy (ICP-AES) was also used to observe the powders as they passed through the plasma. The resulting data indicates that each compound was vaporized and dissociated in the plasma. The following thesis describes the apparatus and experimental procedure used in producing nanocrystals.

  2. Facile preparation of photodegradable hydrogels by photopolymerization

    PubMed Central

    Ki, Chang Seok; Shih, Han; Lin, Chien-Chi

    2013-01-01

    Photodegradable hydrogels have emerged as a powerful material platform for studying and directing cell behaviors, as well as for delivering drugs. The premise of this technique is to use a cytocompatible light source to cleave linkers within a hydrogel, thus causing reduction of matrix stiffness or liberation of matrix-tethered biomolecules in a spatial-temporally controlled manner. The most commonly used photodegradable units are molecules containing nitrobenzyl moieties that absorb light in the ultraviolet (UV) to lower visible wavelengths (~280 to 450 nm). Because photodegradable linkers and hydrogels reported in the literature thus far are all sensitive to UV light, highly efficient UV-mediated photopolymerizations are less likely to be used as the method to prepare these hydrogels. As a result, currently available photodegradable hydrogels are formed by redox-mediated radical polymerizations, emulsion polymerizations, Michael-type addition reactions, or orthogonal click chemistries. Here, we report the first photodegradable poly(ethylene glycol)-based hydrogel system prepared by step-growth photopolymerization. The model photolabile peptide cross-linkers, synthesized by conventional solid phase peptide synthesis, contained terminal cysteines for step-growth thiol-ene photo-click reactions and a UV-sensitive 2-nitrophenylalanine residue in the peptide backbone for photo-cleavage. Photolysis of this peptide was achieved through adjusting UV light exposure time and intensity. Photopolymerization of photodegradable hydrogels containing photolabile peptide cross-linkers was made possible via a highly efficient visible light-mediated thiol-ene photo-click reaction using a non-cleavage type photoinitiator eosin-Y. Rapid gelation was confirmed by in situ photo-rheometry. Flood UV irradiation at controlled wavelength and intensity was used to demonstrate the photodegradability of these photopolymerized hydrogels. PMID:23894212

  3. Bio-mediated synthesis, characterization and cytotoxicity of gold nanoparticles.

    PubMed

    Klekotko, Magdalena; Matczyszyn, Katarzyna; Siednienko, Jakub; Olesiak-Banska, Joanna; Pawlik, Krzysztof; Samoc, Marek

    2015-11-21

    We report here a "green" approach for the synthesis of gold nanoparticles (GNPs) in which the Mentha piperita extract was applied for the bioreduction of chloroauric acid and the stabilization of the formed nanostructures. The obtained GNPs were characterized by UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). The reduction of gold ions with the plant extract leads to the production of nanoparticles with various shapes (spherical, triangular and hexagonal) and sizes (from 10 to 300 nm). The kinetics of the reaction was monitored and various conditions of the synthesis were investigated. As a result, we established protocols optimized towards the synthesis of nanospheres and nanoprisms of gold. The cytotoxic effect of the obtained gold nanoparticles was studied by performing MTT assay, which showed lower cytotoxicity of the biosynthesized GNPs compared to gold nanorods synthesized using the usual seed-mediated growth. The results suggest that the synthesis using plant extracts may be a useful method to produce gold nanostructures for various biological and medical applications. PMID:26456245

  4. Synthesis and characterization of nitrogen substituted zeolites

    NASA Astrophysics Data System (ADS)

    Dogan, Fulya

    The interest in basic solid materials, particularly for basic zeolites has considerably increased in the last two decades because of their potential use in catalysis and separation. Basic zeolites have most often been obtained by ion-exchange or impregnation with alkali metal cations or grafting of organic bases onto zeolite pore walls. Such materials often suffer from instability and/or pore blockage, because none of these approaches places basic sites directly into the zeolite framework. Recently zeolitic materials have been made with some of the bridging oxygen atoms in Si--O--Si and/or Si--O--Al linkages replaced by NH groups, i.e. by substitution of framework oxygen by nitrogen. As a result, the basic strength of the framework increases due to the lower electronegativity of nitrogen with respect to oxygen. In this study, solid base catalysts are obtained by nitrogen substitution of the faujasite type of zeolites under ammonia flow at high temperatures. The efficiency of the reaction is tested by using zeolites with different aluminum contents and extraframework cations and varying the reaction conditions such as ammonia flow rate, reaction temperature and duration. The characterization studies show that high levels of nitrogen substitution can be achieved while maintaining porosity, particularly for NaY and low-aluminum HY zeolites, without a significant loss in the crystallinity. 27Al and 29 Si MAS NMR experiments performed on the nitrogen substituted zeolites show dealumination of the framework and preferential substitution for Si--OH--Al sites at the early stages of the reaction (temperatures at 750--800 °C). No preference is seen for reactions performed at higher temperatures and longer reaction times (e.g., 850 °C and 48 h). X-ray PDF analysis performed on the modified zeolites show that the Si-N distance in the 1st shell is longer than Si-O bond distance and Si-Si/Al bond distance of the Si-O/N-Si/Al linkage decreases, as an indication of a decrease in

  5. Synthesis and characterization of nanosized lead oxide

    NASA Astrophysics Data System (ADS)

    Laak, Sheau Tyan

    Nanosized lead oxide as well as copper-doped lead oxide are prepared using two different synthetic techniques; hydrothermal and precipitation. The precipitation method involves simply reacting lead (IV) acetate with distilled water. On the other hand, the hydrothermal process used an autoclave with the presence of Polyvinyl Pyrrolidone (PVP) to prepare lead oxide (PbO 2) hollow spheres, and lead oxide (Pb3O4) microtubes at reaction temperatures of 90°C and 180°C, respectively. Characterization of the synthesized material was carried out using X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Scanning Electron Microscopy (SEM). X-Ray Diffraction shows that the prepared lead oxides using the hydrothermal process with a reaction a temperature of 90°C is crystalline α PbO 2. SEM shows that the prepared particles are hollow spheres. It also shows uniformity in shape and size. In contrast, X-Ray Diffraction and SEM show that the prepared lead oxide using the hydrothermal process with a reaction temperature of 180°C is nanofiber crystalline α PbO2. It also shows uniformity in shape and size. As to the precipitation method, X-Ray Diffraction shows that the sample is crystalline β PbO2. X-Ray Diffraction revealed that these lead oxides show two different transitions, from β PbO2 to Pb3O4, and Pb3O4 to PbO. These observations were supported by TGA and DTA at 400°C and 700°C, respectively. SEM analysis shows that the prepared β PbO2 sample does not show uniformity, neither in size nor in shape. Indeed, particles appear to congregate and form much larger particles. The results from our study suggest that simple precipitation can lead to the product of PbO2, it however cannot guarantee uniformity. The use of an autoclave in the presence of a polymer such as PVP allowed the precipitation of uniform nano PbO2. In addition, the temperature appeared to affect the morphology of the final product. When low temperature is

  6. A three-dimensional bioprinting system for use with a hydrogel-based biomaterial and printing parameter characterization.

    PubMed

    Song, Seung-Joon; Choi, Jaesoon; Park, Yong-Doo; Lee, Jung-Joo; Hong, So Young; Sun, Kyung

    2010-11-01

    Bioprinting is an emerging technology for constructing tissue or bioartificial organs with complex three-dimensional (3D) structures. It provides high-precision spatial shape forming ability on a larger scale than conventional tissue engineering methods, and simultaneous multiple components composition ability. Bioprinting utilizes a computer-controlled 3D printer mechanism for 3D biological structure construction. To implement minimal pattern width in a hydrogel-based bioprinting system, a study on printing characteristics was performed by varying printer control parameters. The experimental results showed that printing pattern width depends on associated printer control parameters such as printing flow rate, nozzle diameter, and nozzle velocity. The system under development showed acceptable feasibility of potential use for accurate printing pattern implementation in tissue engineering applications and is another example of novel techniques for regenerative medicine based on computer-aided biofabrication system. PMID:21092048

  7. Stearate organogel-gelatin hydrogel based bigels: physicochemical, thermal, mechanical characterizations and in vitro drug delivery applications.

    PubMed

    Sagiri, Sai Sateesh; Singh, Vinay K; Kulanthaivel, Senthilguru; Banerjee, Indranil; Basak, Piyali; Battachrya, M K; Pal, Kunal

    2015-03-01

    Over the past decade, researchers have been trying to develop alternative gel based formulations in comparison to the traditional hydrogels and emulgels. In this perspective, bigels were synthesized by mixing gelatin hydrogel and stearic acid based organogel by hot emulsification method. Two types of bigels were synthesized using sesame oil and soy bean oil based stearate organogels. Gelatin based emulgels prepared using sesame oil and soy bean oil were used as the controls. Microscopic studies revealed that the bigels contained aggregates of droplets, whereas, emulgels showed dispersed droplets within the continuum phase. The emulgels showed higher amount of leaching of oils, whereas, the leaching of the internal phase was negligible from the bigels. Presence of organogel matrix within the bigels was confirmed by XRD, FTIR and DSC methods. Bigels showed higher mucoadhesive and mechanical properties compared to emulgels. Cyclic creep-recovery and stress relaxation studies confirmed the viscoelastic nature of the formulations. Four elemental Burger's model was employed to analyze the cyclic creep-recovery data. Cyclic creep-recovery studies suggested that the deformation of the bigels were lower due to the presence of the organogels within its structure. The formulations showed almost 100% recovery after the creep stage and can be explained by the higher elastic nature of the formulations. Stress relaxation study showed that the relaxation time was higher in the emulgels as compared to the bigels. Also, the % relaxation was higher in emulgels suggesting its fluid dominant nature. The in vitro biocompatibility of the bigels was checked using human epidermal keratinocyte cell line (HaCaT). Both emulgels and bigels were biocompatible in nature. The in vitro drug (ciprofloxacin) release behavior indicated non-Fickian diffusion of the drug from the matrices. The drug release showed good antimicrobial effect against Escherichia coli. Based on the results, it was concluded

  8. Characterization and assessment of a novel poly(ethylene oxide)/polyurethane composite hydrogel (Aquavene) as a ureteral stent biomaterial.

    PubMed

    Gorman, S P; Tunney, M M; Keane, P F; Van Bladel, K; Bley, B

    1998-03-15

    The effective long-term use of indwelling ureteral stents is often hindered by the formation of encrusting deposits which may cause obstruction and blockage of the stent. Development of improved ureteral stent biomaterials capable of preventing or reducing encrustation is therefore particularly desirable. In this study, the suitability as a ureteral stent biomaterial of Aquavene, a novel poly(ethylene oxide)/polyurethane composite hydrogel was compared with that of silicone and polyurethane, two materials widely employed in ureteral stent manufacture. Examination of Aquavene in dry and hydrated states by confocal laser scanning microscopy, scanning electron microscopy, and atomic force microscopy showed the presence of numerous channels within a cellular matrix structure. The channel size increased considerably to as much as 10 microm in diameter in the hydrated state. Aquavene provided superior resistance to encrustation and intraluminal blockage over a 24-week period in a simulated urine flow model. Unobstructed urine flow continued with Aquavene at 24 weeks, whereas silicone and polyurethane stents became blocked with encrustation at 8 and 10 weeks, respectively. Weight loss within Aquavene on the order of 9% (w/w) over the 24-week flow period indicates that extraction of the noncrosslinked poly(ethylene oxide) hydrogel may be responsible for the prevention of encrustation blockage of this biomaterial. In the dry state, Aquavene was significantly harder than either silicone or polyurethane, as shown by Young's modulus, and rapidly became soft on hydration. These additional properties of Aquavene would facilitate ease of stent insertion in the dry state past obstructions in the ureter and provide improved patient comfort on subsequent biomaterial hydration in situ. Aquavene is a promising candidate for use in the urinary tract, as it is probable that effective long-term urine drainage would be maintained in vivo. Further evaluation of this novel biomaterial is

  9. Nanoscale Synthesis and Characterization Laboratory Annual Report 2007

    SciTech Connect

    Hamza, A V

    2008-04-07

    The Nanoscale Synthesis and Characterization Laboratory's (NSCL) primary mission is to create and advance interdisciplinary research and development opportunities in nanoscience and technology. The NSCL is delivering on its mission providing Laboratory programs with scientific solutions through the use of nanoscale synthesis and characterization. While this annual report summarizes 2007 activities, we have focused on nanoporous materials, advanced high strength, nanostructured metals, novel 3-dimensional lithography and characterization at the nanoscale for the past 3 years. In these three years we have synthesized the first monolithic nanoporous metal foams with less than 10% relative density; we have produced ultrasmooth nanocrystalline diamond inertial confinement fusion capsules; we have synthesized 3-dimensional graded density structures from full density to 5% relative density using nanolithography; and we have established ultrasmall angle x-ray scattering as a non-destructive tool to determine the structure on the sub 300nm scale. The NSCL also has a mission to recruit and to train personnel for Lab programs. The NSCL continues to attract talented scientists to the Laboratory. Andrew Detor from Massachusetts Institute of Technology, Sutapa Ghosal from the University of California, Irvine, Xiang Ying Wang from Shanghai Institute of Technology, and Arne Wittstock from University of Bremen joined the NSCL this year. The NSCL is pursuing four science and technology themes: nanoporous materials, advanced nanocrystalline materials, novel three-dimensional nanofabrication technologies, and nondestructive characterization at the mesoscale. The NSCL is also pursuing building new facilities for science and technology such as nanorobotics and atomic layer deposition.

  10. Synthesis, Characterization, and Properties of Zero-Valent Iron Nanoparticles

    SciTech Connect

    Baer, Donald R.; Tratnyek, P. G.; Qiang, You; Amonette, James E.; Linehan, John C.; Sarathy, Vaishnavi; Nurmi, J. T.; Wang, Chong M.; Antony, Jiji

    2007-04-04

    This chapter provides an overview of synthesis, characterization and property measurements techniques important for making understanding the nature of zero valent iron nanoparticles. The chemical reactivity of nanometer-sized materials can be quite different from that of either bulk forms of a material or the individual atoms and molecules that comprise it. Advances in our ability to synthesize, visualize, characterize and model these materials have created new opportunities to control the rates and products of chemical reactions in ways not previously possible. Zero valent iron (ZVI), including non-nanoparticle forms for iron, is one of the most promising remediation technologies for the removal of mobile chlorinated hydrocarbons and reducible inorganic anions for ground water. ZVI nanoparticles may have great potential to assist environmental remediation, but there are significant scientific and technological questions that remain to be answered. Understanding of ZVI reactive metal core-shell nanoparticles requires use of particles that are as well characterized and understood as possible. In this chapter we describe the issues and provide examples that include synthesis of nanoparticles, analytical characterization of the particles and finally measurements of their chemical properties.

  11. Synthesis and Characterization of Functionalized Metal-organic Frameworks

    PubMed Central

    Karagiaridi, Olga; Bury, Wojciech; Sarjeant, Amy A.; Hupp, Joseph T.; Farha, Omar K.

    2014-01-01

    Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy. PMID:25225784

  12. Synthesis and characterization of iodinated polyurethane with inherent radiopacity.

    PubMed

    Kiran, S; James, Nirmala R; Joseph, Roy; Jayakrishnan, A

    2009-10-01

    The synthesis and characterization of polyurethane (PU) with excellent radiopacity for medical and allied applications are reported. Bisphenol-A (BPA) was iodinated to obtain 4,4'-isopropylidinedi-(2,6-diiodophenol) (IBPA) which was used as a chain extender for the preparation of a radiopaque PU. The PU was prepared by reacting 4,4'-methylenebis(phenyl isocyanate) (MDI), poly(tetramethylene glycol) (PTMG) and IBPA in 2.2:1.2:1 molecular ratio and is characterized by infrared spectroscopy (IR), thermogravimetry (TGA), dynamic mechanical analysis (DMA), energy dispersive X-ray analysis (EDX), gel permeation chromatography (GPC) and X-radiography. X-ray images showed that the PU prepared using IBPA as the chain extender is highly radiopaque. An in vitro cytotoxicity test using L929 mouse fibroblast cells shows that the PU is non-cytotoxic. The outlined synthesis of a PU with radiocontrast properties opens up the possibility of synthesizing many different kinds of radiopaque PUs with desirable range of physical properties exploiting the versatility in their chemical synthesis. PMID:19596151

  13. Synthesis and characterization of copper 4-carboxyphenylphosphonates

    SciTech Connect

    Zima, Vitezslav; Svoboda, Jan; Benes, Ludvik; Melanova, Klara; Trchova, Miroslava; Ruzicka, Ales

    2009-11-15

    Three new copper 4-carboxyphenylphosphonates with formulae Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}).2H{sub 2}O, Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}) and Cu{sub 3}(OOCC{sub 6}H{sub 4}PO{sub 3}){sub 2}.3H{sub 2}O were prepared and characterized by thermogravimetric analysis, X-ray diffraction analysis, energy-dispersive X-ray microanalysis and infrared spectroscopy. The preparation conditions of Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}).2H{sub 2}O and Cu{sub 3}(OOCC{sub 6}H{sub 4}PO{sub 3}){sub 2}.3H{sub 2}O differ in the acidity of the reaction mixture, where Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}) was prepared under hydrothermal conditions. Copper 4-carboxyphenylphosphonate with formula Cu{sub 3}(OOCC{sub 6}H{sub 4}PO{sub 3}){sub 2}.3H{sub 2}O reacts with 4-carboxyphenylphosphonic acid to form Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}).2H{sub 2}O. Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}).2H{sub 2}O is orthorhombic, space group Pbcn (no. 60), a=8.234(2) A, b=9.438(2) A, c=24.899(5) A. Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}) crystallizes in the monoclinic space group P2{sub 1}/c (no. 14), a=19.0951(3), b=8.0968(4), c=5.2111(11) A, beta=94.914(6){sup o}, Z=4. Its layered structure is composed of distorted CuO{sub 6} octahedra arranged hexagonally in a gibbsite-like manner around two phosphonate groups, which have their carboxyphenyl groups extending into the space above and below the copper-phosphonate layer. Infrared spectra indicate that for both Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}).2H{sub 2}O and Cu(HOOCC{sub 6}H{sub 4}PO{sub 3}) the acid hydrogen is present at the carboxyl group and not at the phosphonic group. - Graphical abstract: Three new copper carboxyphenylphosphonates were synthesized. Layered structure of one of them, CuH(OOCC{sub 6}H{sub 4}PO{sub 3}), is composed of CuO{sub 6} octahedra arranged hexagonally around two phosphonate groups, which have their carboxyphenyl groups extending into the space above and below the copper-phosphonate layer.

  14. Development and characterization of a novel, antimicrobial, sterile hydrogel dressing for burn wounds: single-step production with gamma irradiation creates silver nanoparticles and radical polymerization.

    PubMed

    Boonkaew, Benjawan; Barber, Philip M; Rengpipat, Sirirat; Supaphol, Pitt; Kempf, Margit; He, Jibao; John, Vijay T; Cuttle, Leila

    2014-10-01

    Patients with burn wounds are susceptible to wound infection and sepsis. This research introduces a novel burn wound dressing that contains silver nanoparticles (SNPs) to treat infection in a 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS-Na(+) ) hydrogel. Silver nitrate was dissolved in AMPS-Na(+) solution and then exposed to gamma irradiation to form SNP-infused hydrogels. The gamma irradiation results in a cross-linked polymeric network of sterile hydrogel dressing and a reduction of silver ions to form SNPs infused in the hydrogel in a one-step process. About 80% of the total silver was released from the hydrogels after 72 h immersion in simulated body fluid solution; therefore, they could be used on wounds for up to 3 days. All the hydrogels were found to be nontoxic to normal human dermal fibroblast cells. The silver-loaded hydrogels had good inhibitory action against Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus. Results from a pilot study on a porcine burn model showed that the 5-mM silver hydrogel was efficient at preventing bacterial colonization of wounds, and the results were comparable to the commercially available silver dressings (Acticoat(TM) , PolyMem Silver(®) ). These results support its use as a potential burn wound dressing. PMID:25079080

  15. Biopolymeric receptor for peptide recognition by molecular imprinting approach--synthesis, characterization and application.

    PubMed

    Singh, Lav Kumar; Singh, Monika; Singh, Meenakshi

    2014-12-01

    The present work is focused on the development of a biocompatible zwitterionic hydrogel for various applications in analytical chemistry. Biopolymer chitosan was derivatized to obtain a series of zwitterionic hydrogel samples. Free amino groups hanging on the biopolymeric chain were reacted with γ-butyrolactone to quaternize the N-centers of polymeric chain. N,N-methylene-bis-acrylamide acts as a crosslinker via Michael-type addition in the subsequent step and facilitated gelation of betainized chitosan. These biopolymeric hydrogel samples were fully characterized by FTIR, (1)H NMR, (13)C NMR spectra, SEM and XRD. Hydrogels were further characterized for their swelling behavior at varying parameters. The extent of swelling was perceived to be dictated by solvent composition such as pH, ionic strength and temperature. This valuable polymeric format is herein chosen to design an artificial receptor for dipeptide 'carnosine', which has adequate societal significance to be analytically determined, by molecular imprinting. Electrostatic interactions along with complementary H-bonding and other hydrophobic interactions inducing additional synergetic effect between the template (carnosine) and the imprinted polymer led to the formation of imprinted sites. The MIP was able to selectively and specifically take up carnosine from aqueous solution quantitatively. Thus prepared MIPs were characterized by FTIR spectroscopy, SEM providing evidence for the quality and quantity of imprinted gels. The binding studies showed that the MIP illustrated good recognition for carnosine as compared to non-imprinted polymers (NIPs). Detection limit was estimated as 3.3 μg mL(-1). Meanwhile, selectivity experiments demonstrated that imprinted gel had a high affinity to carnosine in the presence of close structural analogues (interferrants). PMID:25491843

  16. Enzymatic formation of a novel cell-adhesive hydrogel based on small peptides with a laterally grafted l-3,4-dihydroxyphenylalanine group

    NASA Astrophysics Data System (ADS)

    Xu, J. X.; Zhou, Z.; Wu, B.; He, B. F.

    2014-01-01

    We rationally designed a bioadhesive supramolecular hydrogel by introducing l-3,4-dihydroxylphenylalanine (DOPA) groups while properly integrating the enzymatic reactions and self-assembly processes. The effective presence of the catechol groups successfully promoted the adhesion and proliferation of human fibroblast cells.We rationally designed a bioadhesive supramolecular hydrogel by introducing l-3,4-dihydroxylphenylalanine (DOPA) groups while properly integrating the enzymatic reactions and self-assembly processes. The effective presence of the catechol groups successfully promoted the adhesion and proliferation of human fibroblast cells. Electronic supplementary information (ESI) available: Detailed experimental procedures, synthesis and characterization of the compounds and hydrogel preparation. See DOI: 10.1039/c3nr04528e

  17. Synthesis procedure optimization and characterization of europium (III) tungstate nanoparticles

    NASA Astrophysics Data System (ADS)

    Rahimi-Nasrabadi, Mehdi; Pourmortazavi, Seied Mahdi; Ganjali, Mohammad Reza; Reza Banan, Ali; Ahmadi, Farhad

    2014-09-01

    Taguchi robust design as a statistical method was applied for the optimization of process parameters in order to tunable, facile and fast synthesis of europium (III) tungstate nanoparticles. Europium (III) tungstate nanoparticles were synthesized by a chemical precipitation reaction involving direct addition of europium ion aqueous solution to the tungstate reagent solved in an aqueous medium. Effects of some synthesis procedure variables on the particle size of europium (III) tungstate nanoparticles were studied. Analysis of variance showed the importance of controlling tungstate concentration, cation feeding flow rate and temperature during preparation of europium (III) tungstate nanoparticles by the proposed chemical precipitation reaction. Finally, europium (III) tungstate nanoparticles were synthesized at the optimum conditions of the proposed method. The morphology and chemical composition of the prepared nano-material were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and fluorescence.

  18. Synthesis and Structural Characterization of Orthorhombic Vanadium Oxide Nanorods

    NASA Astrophysics Data System (ADS)

    Garcia, L. M.; Chavira, E.; Santiago-Jacinto, P.; Rendon, L.; Marinero, E. E.; Tejada, A.; Fregoso-Israel, E.; Flores, C.

    2012-02-01

    Nanorod structures for Li storage are of interest for rechargeable battery applications. Vanadium pentoxide is a promising battery cathode material and in this work we report on the synthesis of V2O5 orthorhombic single crystal and polycrystalline nanorods by the sol-gel polymerizing acryl amide method via ethylenediamine tetra acetic acid EDTA assisted hydrothermal process. In order to determine the thermodynamic stability of nanostructured polymorphs vanadates, heat treatments were performed from 450 C to 500 ^oC with annealing times ranging from 48 to 72 h. The morphologies and structures of the nanorods were characterized by XRD, SEM and HRTEM. Thermo Gravimetric Analysis (TGA) was employed to monitor reaction mass losses during the course of the synthesis. Nanorod diameters ranging from 50 to 150 nm were observed. The lengths and diameter of the rods depended on the conditions of the preparation, such as concentration, and reaction time.

  19. New Synthesis of TATB. Scaleup and Product Characterization

    SciTech Connect

    Schmidt, R.D.; Mitchell, A.R.; Lee, G.S.; Pagoria, P.F.; Coburn, M.D.; Quinlan, W.T.; Thorpe, R.; Cates, M.

    2000-03-15

    At the 29th International Annual Conference of ICT (1998), the authors described the results of laboratory-scale process development studies for a new synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). This new synthesis approach--which uses vicarious nucleophilic substitution (VNS) methodology--converts picramide to TATB in high yield, and potentially at lower cost and with few environmental effects than existing synthetic approaches. In this report they describe results of their work on producing TATB by the VNS method at the pilot plant scale. They will discuss structure and control of impurities, changes in yield/quality with reaction conditions, choice of solvents, workup and product isolation, safety, and environmental considerations. Product characterization (particle size, DSC, HPLC, etc.) as well as small-scale safety and performance testing is also discussed.

  20. Synthesis and characterization of luminescent aluminium selenide nanocrystals

    SciTech Connect

    Balitskii, O.A.; Demchenko, P.Yu.; Mijowska, E.; Cendrowski, K.

    2013-02-15

    Highlights: ► Synthesis procedure of size and sharp controlled Al{sub 2}Se{sub 3} nanocrystals is introduced. ► Obtained nanoparticles are highly crystalline of hexagonal wurtzite type. ► Colloidal Al{sub 2}Se{sub 3} nanocrystals are highly luminescent in the near UV spectral region. ► They can be implemented in light emitters/collectors, concurring with II–VI nanodots. -- Abstract: We propose the synthesis and characterization of colloidal aluminium selenide nanocrystals using trioctylphosphine as a solvent. The nanoparticles have several absorption bands in the spectral region 330–410 nm and are bright UV-blue luminescent, which is well demanded in light collecting and emitting devices, e.g. for tuning their spectral characteristics to higher energy solar photons.

  1. Green synthesis and characterization of se nanoparticles and nanorods

    NASA Astrophysics Data System (ADS)

    Chen, Huiyu; Yoo, Ji-Beom; Liu, Yaqing; Zhao, Guizhe

    2011-12-01

    Selenium nanoparticles and nanorods were successfully prepared in a mixed solvent of ethylene glycol and water at a relatively low temperature of 85°C. No other surfactant or template was employed, and glucose was used as a green and mild reducing reagent in the current synthesis. The volume ratio of ethylene glycol to water played an important role for controlling the shapes of selenium products. The obtained selenium samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectra, and UV-vis absorption spectra. The evolution process from amorphous selenium to a trigonal phase complied with a "solid-solution-solid" formation mechanism. HRTEM and SAED results indicate that the trigonal selenium nanorods grow along the [001] direction. This method might provide an environmentally-friendly and low cost route for the synthesis of other related nanomaterials with controlled morphologies.

  2. Preparation and characterization of gatifloxacin-loaded sodium alginate hydrogel membranes supplemented with hydroxypropyl methylcellulose and hydroxypropyl cellulose polymers for wound dressing

    PubMed Central

    Prabu, Durai; Majdalawieh, Amin F.; Abu-Yousef, Imad A.; Inbasekaran, Kadambari; Balasubramaniam, Tharani; Nallaperumal, Narayanan; Gunasekar, Conjeevaram J.

    2016-01-01

    Introduction: The aim of this study is to evaluate gatifloxacin-loaded sodium alginate hydrogel membranes, supplemented with glycerol (a plasticizer), glutaraldehyde (a cross-linking agent), and hydroxypropyl methylcellulose (HPMC) or hydroxypropyl cellulose (HPC) polymers, as potential wound dressing materials based on their physicochemical properties and the sustain-release phenomenon. Materials and Methods: The physicochemical properties of the prepared hydrogel membranes were evaluated by several methods including Fourier transform infrared and differential scanning calorimetry. Different techniques were used to assess the swelling behavior, tensile strength and elongation, % moisture absorption, % moisture loss, water vapor transmission rate (WVTR), and microbial penetration for the hydrogel membranes. In vitro gatifloxacin release from the hydrogel membranes was examined using the United States Pharmacopeia XXIII dissolution apparatus. Four kinetics models (zero-order, first-order, Higuchi equation, and Korsmeyer-Peppas equation) were applied to study drug release kinetics. Results: The addition of glycerol, glutaraldehyde, HPMC, and HPC polymers resulted in a considerable increase in the tensile strength and flexibility/elasticity of the hydrogel membranes. WVTR results suggest that hydrated hydrogel membranes can facilitate water vapor transfer. None of the hydrogel membranes supported microbial growth. HPMC-treated and HPC-treated hydrogel membranes allow slow, but sustained, release of gatifloxacin for 48 h. Drug release kinetics revealed that both diffusion and dissolution play an important role in gatifloxacin release. Conclusions: Given their physicochemical properties and gatifloxacin release pattern, HPMC-treated and HPC-treated hydrogel membranes exhibit effective and sustained drug release. Furthermore, HPMC-treated and HPC-treated hydrogel membranes possess physiochemical properties that make them effective and safe wound dressing materials. PMID

  3. Controlling the shell formation in hydrothermally reduced graphene hydrogel.

    PubMed

    Hu, Kaiwen; Xie, Xingyi; Cerruti, Marta; Szkopek, Thomas

    2015-05-26

    Graphene hydrogels/aerogels are emerging three-dimensional graphene macroscopic assemblies of potential use in many applications including energy storage, pollutant adsorption, and gas sensing. In this Letter, we identify, characterize and control the formation of the exterior shell structure of graphene hydrogels prepared via hydrothermal reduction of graphene oxide. Unlike the porous bulk of the hydrogel, the shell is a compact, highly ordered layer with a higher electrical conductivity. Shell formation is dependent upon the surface anchoring of graphene oxide at the liquid-air and liquid-container interfaces. By purposefully weakening surface anchoring of graphene oxide using mild thermal or chemical prereduction method prior to hydrothermal reduction, we have succeeded in completely suppressing shell formation in the graphene hydrogel. The resulting graphene hydrogel shows a lower volume reduction with a porous bulk structure immediately accessible from the surface, in contrast to graphene hydrogels prepared under conventional conditions. PMID:25942331

  4. Functional Metal Oxide Nanostructures: Their Synthesis, Characterization, and Energy Applications

    NASA Astrophysics Data System (ADS)

    Iyer, Aparna

    This research focuses on studying metal oxides (MnO 2, Co3O4, MgO, Y2O3) for various applications including water oxidation and photocatalytic oxidation, developing different synthesis methodologies, and presenting detailed characterization studies of these metal oxides. This research consists of three major parts. The first part is studying novel applications and developing a synthesis method for manganese oxide nanomaterials. Manganese oxide materials were studied for renewable energy applications by using them as catalysts for water oxidation reactions. In this study, various crystallographic forms of manganese oxides (amorphous, 2D layered, 1D 2 x 2 tunnel structures) were evaluated for water oxidation catalysis. Amorphous manganese oxides (AMO) were found to be catalytically active for chemical and photochemical water oxidation compared to cryptomelane type tunnel manganese oxides (2 x 2 tunnels; OMS2) or layered birnessite (OL-1) materials. Detailed characterization was done to establish a correlation between the properties of the manganese oxide materials and their catalytic activities in water oxidation. The gas phase photocatalytic oxidation of 2-propanol under visible light was studied using manganese oxide 2 x 2 tunnel structures (OMS-2) as catalysts (Chapter 3). The reaction is 100% selective to acetone. As suggested by the photocatalytic and characterization data, important factors for the design of active OMS-2 photocatalysts are synthesis methodology, morphology, mixed valency and the release of oxygen from the OMS-2 structure. Manganese oxide octahedral molecular sieves (2 x 2 tunnels; OMS-2) with self-assembled dense or hollow sphere morphologies were fabricated via a room temperature ultrasonic atomization assisted synthesis (Chapter 4). The properties and catalytic activities of these newly developed materials were compared with that of OMS-2 synthesized by conventional reflux route. These materials exhibit exceptionally high catalytic activities

  5. Fabrication and characterization of superparamagnetic and thermoresponsive hydrogels based on oleic-acid-coated Fe 3O 4 nanoparticles, hexa(ethylene glycol) methyl ether methacrylate and 2-(acetoacetoxy)ethyl methacrylate

    NASA Astrophysics Data System (ADS)

    Papaphilippou, Petri C.; Pourgouris, Antonis; Marinica, Oana; Taculescu, Alina; Athanasopoulos, George I.; Vekas, Ladislau; Krasia-Christoforou, Theodora

    2011-03-01

    Stimuli-responsive hydrogel nanocomposites comprised of swollen polymer networks, in which magnetic nanoparticles are embedded, are a relatively new class of "smart" soft materials presenting a significant impact on various technological and biomedical applications. A novel approach for the fabrication of hydrogel nanocomposites exhibiting temperature- and magneto-responsive behavior involves the random copolymerization of hexa(ethylene glycol) methyl ether methacrylate (HEGMA, hydrophilic, thermoresponsive) and 2-(acetoacetoxy)ethyl methacrylate (AEMA, hydrophobic, metal-chelating) in the presence of preformed oleic-acid-coated magnetite nanoparticles (OA·Fe 3O 4). In total, two series of hydrogel nanocomposites have been prepared in two different solvent systems: ethyl acetate (series A) and tetrahydrofuran (series B). The degrees of swelling (DSs) of all conetworks were determined in organic and in aqueous media. The nanocrystalline phase adopted by the embedded magnetic nanoparticles was investigated by X-ray diffraction (XRD) spectroscopy. The obtained diffraction patterns indicated the presence of magnetite (Fe 3O 4). Deswelling kinetic studies that were carried out at ˜60 °C in water demonstrated the thermoresponsive properties of the hydrogel nanocomposites, attributed to the presence of the hexaethylene glycol side chains within the conetworks. Moreover, thermal gravimetric analysis (TGA) measurements showed that these materials exhibited superior thermal stability compared to the pristine hydrogels. Further to the characterization of compositional and thermal properties, the assessment of magnetic characteristics by vibrational sample magnetometry (VSM) disclosed superparamagnetic behavior. The tunable superparamagnetic behavior exhibited by these materials depending on the amount of magnetic nanoparticles incorporated within the networks combined with their thermoresponsive properties may allow for their future exploitation in the biomedical field.

  6. Design properties of hydrogel tissue-engineering scaffolds

    PubMed Central

    Zhu, Junmin; Marchant, Roger E

    2011-01-01

    This article summarizes the recent progress in the design and synthesis of hydrogels as tissue-engineering scaffolds. Hydrogels are attractive scaffolding materials owing to their highly swollen network structure, ability to encapsulate cells and bioactive molecules, and efficient mass transfer. Various polymers, including natural, synthetic and natural/synthetic hybrid polymers, have been used to make hydrogels via chemical or physical crosslinking. Recently, bioactive synthetic hydrogels have emerged as promising scaffolds because they can provide molecularly tailored biofunctions and adjustable mechanical properties, as well as an extracellular matrix-like microenvironment for cell growth and tissue formation. This article addresses various strategies that have been explored to design synthetic hydrogels with extracellular matrix-mimetic bioactive properties, such as cell adhesion, proteolytic degradation and growth factor-binding. PMID:22026626

  7. Hydrogels in Healthcare: From Static to Dynamic Material Microenvironments

    PubMed Central

    Kirschner, Chelsea M.; Anseth, Kristi S.

    2013-01-01

    Advances in hydrogel design have revolutionized the way biomaterials are applied to address biomedical needs. Hydrogels were introduced in medicine over 50 years ago and have evolved from static, bioinert materials to dynamic, bioactive microenvironments, which can be used to direct specific biological responses such as cellular ingrowth in wound healing or on-demand delivery of therapeutics. Two general classes of mechanisms, those defined by the user and those dictated by the endogenous cells and tissues, can control dynamic hydrogel microenvironments. These highly tunable materials have provided bioengineers and biological scientists with new ways to not only treat patients in the clinic but to study the fundamental cellular responses to engineered microenvironments as well. Here, we provide a brief history of hydrogels in medicine and follow with a discussion of the synthesis and implementation of dynamic hydrogel microenvironments for healthcare-related applications. PMID:23929381

  8. Electrochemical synthesis and characterization of zinc oxalate nanoparticles

    SciTech Connect

    Shamsipur, Mojtaba; Roushani, Mahmoud; Pourmortazavi, Seied Mahdi

    2013-03-15

    Highlights: ► Synthesis of zinc oxalate nanoparticles via electrolysis of a zinc plate anode in sodium oxalate solutions. ► Design of a Taguchi orthogonal array to identify the optimal experimental conditions. ► Controlling the size and shape of particles via applied voltage and oxalate concentration. ► Characterization of zinc oxalate nanoparticles by SEM, UV–vis, FT-IR and TG–DTA. - Abstract: A rapid, clean and simple electrodeposition method was designed for the synthesis of zinc oxalate nanoparticles. Zinc oxalate nanoparticles in different size and shapes were electrodeposited by electrolysis of a zinc plate anode in sodium oxalate aqueous solutions. It was found that the size and shape of the product could be tuned by electrolysis voltage, oxalate ion concentration, and stirring rate of electrolyte solution. A Taguchi orthogonal array design was designed to identify the optimal experimental conditions. The morphological characterization of the product was carried out by scanning electron microscopy. UV–vis and FT-IR spectroscopies were also used to characterize the electrodeposited nanoparticles. The TG–DTA studies of the nanoparticles indicated that the main thermal degradation occurs in two steps over a temperature range of 350–430 °C. In contrast to the existing methods, the present study describes a process which can be easily scaled up for the production of nano-sized zinc oxalate powder.

  9. Synthesis and characterization of in situ photogelable polysaccharide derivative for drug delivery.

    PubMed

    Hu, Rong; Chen, Yu-Yun; Zhang, Li-Ming

    2010-06-30

    A novel polysaccharide derivative with photoreactivity was prepared by the conjugation of carboxymethylated chitosan with N-hydroxyl succinimide-activated nitrocinnamate in the presence of N,N-dicyclohexylcarbodiimide, and characterized by IR, (1)H NMR, UV-vis and rheological analyses. It was found that such a modified polysaccharide could exhibit an unique photogelation ability in the absence of potentially toxic photoinitiator or catalyst and be suitable particularly for the in situ preparation of photocrosslinked hydrogel biomaterials. By changing the photoirradiation time and incorporated nitrocinnamate content, its photogelation property could be modulated. For the resultant hydrogels incorporated with various nitrocinnamate contents, their properties such as swelling, viscoelasticity, in vitro biodegradation and drug release were investigated. In addition, the photogelation mechanism of this polysaccharide derivative was also discussed. PMID:20399843

  10. Catalysis of Supramolecular Hydrogelation.

    PubMed

    Trausel, Fanny; Versluis, Frank; Maity, Chandan; Poolman, Jos M; Lovrak, Matija; van Esch, Jan H; Eelkema, Rienk

    2016-07-19

    One often thinks of catalysts as chemical tools to accelerate a reaction or to have a reaction run under more benign conditions. As such, catalysis has a role to play in the chemical industry and in lab scale synthesis that is not to be underestimated. Still, the role of catalysis in living systems (cells, organisms) is much more extensive, ranging from the formation and breakdown of small molecules and biopolymers to controlling signal transduction cascades and feedback processes, motility, and mechanical action. Such phenomena are only recently starting to receive attention in synthetic materials and chemical systems. "Smart" soft materials could find many important applications ranging from personalized therapeutics to soft robotics to name but a few. Until recently, approaches to control the properties of such materials were largely dominated by thermodynamics, for instance, looking at phase behavior and interaction strength. However, kinetics plays a large role in determining the behavior of such soft materials, for instance, in the formation of kinetically trapped (metastable) states or the dynamics of component exchange. As catalysts can change the rate of a chemical reaction, catalysis could be used to control the formation, dynamics, and fate of supramolecular structures when the molecules making up these structures contain chemical bonds whose formation or exchange are susceptible to catalysis. In this Account, we describe our efforts to use synthetic catalysts to control the properties of supramolecular hydrogels. Building on the concept of synthesizing the assembling molecule in the self-assembly medium from nonassembling precursors, we will introduce the use of catalysis to change the kinetics of assembler formation and thereby the properties of the resulting material. In particular, we will focus on the synthesis of supramolecular hydrogels where the use of a catalyst provides access to gel materials with vastly different appearance and mechanical

  11. Studying functional properties of hydrogel and silicone-hydrogel contact lenses with PALS, MIR and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Filipecki, J.; Sitarz, M.; Kocela, A.; Kotynia, K.; Jelen, P.; Filipecka, K.; Gaweda, M.

    2014-10-01

    Determination of free volume holes of the hydrogel and silicone-hydrogel polymer contact lenses were investigated. Two types of polymer contact lenses were used as materials: the first is a hydrogel contact lenses Proclear family (Omafilcon A), while the second is a silicone-hydrogel contact lens of the family Biofinity (Comfilcon A). Positron annihilation lifetime spectroscopy PALS was used to characterize geometrical sizes and fraction of the free volume holes in the investigated samples. There is a clear difference in the free volume sizes and their fractions between silicone-hydrogel and polymer hydrogel contact lenses which in turn are connected with oxygen permeability in these lenses. Apart from that, spectroscopic (middle infrared) MIR and Raman examinations were carried out in order to demonstrate the differences of the water content in the test contact lenses.

  12. Mechanical Behavior of Tough Hydrogels for Structural Applications

    NASA Astrophysics Data System (ADS)

    Illeperuma, Widusha Ruwangi Kaushalya

    Hydrogels are widely used in many commercial products including Jell-O, contact lenses, and superabsorbent diapers. In recent decades, hydrogels have been under intense development for biomedical applications, such as scaffolds in tissue engineering, carriers for drug delivery, and valves in microfluidic systems. But the scope is severely limited as conventional hydrogels are weak and brittle and are not very stretchable. This thesis investigates the approaches that enhance the mechanical properties of hydrogels and their structural applications. We discov¬ered a class of exceptionally stretchable and tough hydrogels made from poly-mers that form networks via ionic and covalent crosslinks. Although such a hydrogel contains ~90% water, it can be stretched beyond 20 times its initial length, and has a fracture energy of ~9000 J/m2. The combination of large stretchability, remarkable toughness, and recoverability of stiffness and toughness, along with easy synthesis makes this material much superior over existing hydrogels. Extreme stretchability and blunted crack tips of these hydrogels question the validity of traditional fracture testing methods. We re-examine a widely used pure shear test method to measure the fracture energy. With the experimental and simulation results, we conclude that the pure shear test method can be used to measure fracture energy of extremely stretchable materials. Even though polyacrylamide-alginate hydrogels have an extremely high toughness, it has a relatively low stiffness and strength. We improved the stiffness and strength by embedding fibers. Most hydrogels are brittle, allowing the fibers to cut through the hydrogel when the composite is loaded. But tough hydrogel composites do not fail by the fibers cutting the hydrogel; instead, it undergoes large deforming by fibers sliding through the matrix. Hydrogels were not considered as materials for structural applications. But with enhanced mechanical properties, they have opened up

  13. Synthesis and characterization of advanced materials for Navy applications

    SciTech Connect

    Covino, J.

    1993-12-31

    This paper addresses the synthesis of ceramics and ceramic coatings, via the sol-gel process for use in specific Navy applications. Among the specific applications are: coatings for electrocromic devices; laser gyro bodies, hermetic coatings for optical fibers for use in ocean environments; coating development for advanced light weight structural applications; and incorporation of organic and inorganic dyes in silica based ceramics for laser applications. It will also address the characterization of these systems as well as advanced structural materials with respect to durability, chemical stability, optical properties and other properties which are more specific to their applications and end use.

  14. Synthesis and characterization of Mn-Bi alloy

    SciTech Connect

    Mishra, Ashutosh; Patil, Harsha; Jain, G.; Mishra, N.

    2012-06-05

    High purity MnBi low temperature phase has been prepared and analyzed using X-ray diffraction, Lorentz-Polarization Factor and Fourier transforms infrared measurement. After synthesis of samples structural characterization has done on samples by X-ray diffraction, which shows that after making the bulk sample is in no single phase MnBi has been prepared by sintering Mn and Bi powders. By Lorentz-Polarization Factor is affecting the relative intensity of diffraction lines on a powder form. And by FTIR which shows absorption peaks of MnBi alloys.

  15. A new photosensitive dielectric insulating polyester film: Synthesis and characterization

    SciTech Connect

    Shi, F.F.; Economy, J.E.

    1996-10-01

    In this paper, we described the synthesis and the characterization of a new dielectric insulating film prepared from a photosensitive polyester. The unique feature of this new photosensitive polyester film is that it can be foamed when cured at 280{degrees}C though interchain transesterification reaction. This process can reduce the dielectric constant of the film to 2.5. Some important properties, such as photosensitivity, thermal stability, mechanical properties of this new dielectric insulating polymer film were discussed. The preliminary results show a good resolution and an acceptable profile of this new insulator after foaming.

  16. PtCo/Au nanocomposite: Synthesis, characterization, and magnetic properties

    NASA Astrophysics Data System (ADS)

    Dai, Jingtao; Du, Yukou; Wang, Fangwei; Yang, Ping

    2007-09-01

    Magnetic PtCo/Au nanocomposites with narrow size distribution were synthesized in a reverse micelle, followed by a post-synthesis handling of the stabilizer-exchange technique. The PtCo/Au nanocomposites were characterized by ultraviolet visible spectroscopy, X-ray diffraction and transmission electron microscopy, respectively. Superconducting quantum interference device studies revealed that the nanocomposites were superparamagnetic above the blocking temperature ( TB=69 K), while the samples were ferromagnetic with Hc (628 Oe) and Ms (2.97 emu /g) at 5 K.

  17. Synthesis and characterization of Bi-Te-Se thermoelectric materials

    SciTech Connect

    Tripathi, S. K.; Kumari, Ankita; Ridhi, R.; Kaur, Jagdish

    2015-08-28

    Bismuth Telluride (Bi{sub 2}Te{sub 3}) and its related alloys act as a promising thermoelectric material and preferred over other thermoelectric materials due to their high stability and efficiency under ambient conditions. In the present work, we have reported economical, environment friendly and low-temperature aqueous chemical method for the synthesis of Bi-Se-Te alloy. The prepared samples are characterized by X-Ray Diffraction to investigate the structural properties and UV-Visible spectroscopy for the spectroscopic analysis. The absorption spectrum reveals the sensitivity in the ultraviolet as well as in visible region.

  18. Synthesis and characterization of novel cardanol based benzoxazines.

    PubMed

    Minigher, Andrea; Benedetti, Elena; De Giacomo, Ornela; Campaner, Pietro; Aroulmoji, Vincent

    2009-04-01

    Benzoxazines are a class of phenolic compounds extensively studied in polymer science because of their properties as fiber reinforcements, fire-retardants and curing agents. In this article is described a solvent-less process, based on a Mannich reaction involving a primary amine and an aldehyde, for the preparation of new benzoxazines deriving from cardanol (a well known phenol obtained as a renewable organic resource and harmful by-product of the cashew industry). Particular attention is given to the synthesis and chemical characterization (both by 1H NMR spectroscopy and HPLC), while the thermal polymerization process has been monitored by differential scanning calorimetry. PMID:19475998

  19. Synthesis and Characterization of Furazan Energetics ADAAF and DOATF

    NASA Astrophysics Data System (ADS)

    Veauthier, Jacqueline M.; Chavez, David E.; Tappan, Bryce C.; Parrish, Damon A.

    2010-06-01

    The synthesis and structural characterization of bis[4-aminofurazanyl-3-azoxy]azofurazan (ADAAF) and 3,4:7,8:11,12:15,16-tetrafurazano-1,2,5,6,9,10,13,14-octaazacyclohexadeca-1,3,5,7,9,11,13,15-octaene-1,10-dioxide (DOATF) are described. Explosive sensitivity properties of both materials were determined. The heat of formation of ADAAF was measured to be 300 kcal/mol and the detonation velocity and pressure of ADAAF were measured to be 7.88 km/s and 299 kbar, respectively, at 94% theoretical maximum density. We also investigated the burning rate characteristics of ADAAF.

  20. Designing tragacanth gum based sterile hydrogel by radiation method for use in drug delivery and wound dressing applications.

    PubMed

    Singh, Baljit; Varshney, Lalit; Francis, Sanju; Rajneesh

    2016-07-01

    Present article discusses synthesis and characterization of the sterile and pure hydrogel wound dressings which were prepared through radiation method by using polyvinyl alcohol (PVA), tragacanth gum (TG) and sodium alginate (SA). The polymer films were characterized by SEM, Cryo-SEM, FTIR, solid state C(13) NMR and XRD, TGA, and DSC. Some important biological properties such as O2 permeability, water vapor transmission rate, microbial permeability, haemolysis, thrombogenic behavior, antioxidant activity, bio-adhesion and mechanical properties were also studied. The hydrogel film showed thrombogenicity (82.43±1.54%), haemolysis (0.83±0.09%), oxygen permeability (6.433±0.058mg/L) and water vapor permeability (197.39±25.34g/m(2)/day). Hydrogel films were found biocompatible and impermeable to microbes. The release of antibiotic drug moxifloxacin occurred through non-Fickian mechanism and release profile was best fitted in Hixson-Crowell model for drug release. Overall, these results indicate the suitability of these hydrogels in wound dressing applications. PMID:27020943

  1. Design and synthesis of target-responsive hydrogel for portable visual quantitative detection of uranium with a microfluidic distance-based readout device.

    PubMed

    Huang, Yishun; Fang, Luting; Zhu, Zhi; Ma, Yanli; Zhou, Leiji; Chen, Xi; Xu, Dunming; Yang, Chaoyong

    2016-11-15

    Due to uranium's increasing exploitation in nuclear energy and its toxicity to human health, it is of great significance to detect uranium contamination. In particular, development of a rapid, sensitive and portable method is important for personal health care for those who frequently come into contact with uranium ore mining or who investigate leaks at nuclear power plants. The most stable form of uranium in water is uranyl ion (UO2(2+)). In this work, a UO2(2+) responsive smart hydrogel was designed and synthesized for rapid, portable, sensitive detection of UO2(2+). A UO2(2+) dependent DNAzyme complex composed of substrate strand and enzyme strand was utilized to crosslink DNA-grafted polyacrylamide chains to form a DNA hydrogel. Colorimetric analysis was achieved by encapsulating gold nanoparticles (AuNPs) in the DNAzyme-crosslinked hydrogel to indicate the concentration of UO2(2+). Without UO2(2+), the enzyme strand is not active. The presence of UO2(2+) in the sample activates the enzyme strand and triggers the cleavage of the substrate strand from the enzyme strand, thereby decreasing the density of crosslinkers and destabilizing the hydrogel, which then releases the encapsulated AuNPs. As low as 100nM UO2(2+) was visually detected by the naked eye. The target-responsive hydrogel was also demonstrated to be applicable in natural water spiked with UO2(2+). Furthermore, to avoid the visual errors caused by naked eye observation, a previously developed volumetric bar-chart chip (V-Chip) was used to quantitatively detect UO2(2+) concentrations in water by encapsulating Au-Pt nanoparticles in the hydrogel. The UO2(2+) concentrations were visually quantified from the travelling distance of ink-bar on the V-Chip. The method can be used for portable and quantitative detection of uranium in field applications without skilled operators and sophisticated instruments. PMID:27209576

  2. Sol - Gel synthesis and characterization of magnesium peroxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Jaison, J.; Ashok raja, C.; Balakumar, S.; Chan, Y. S.

    2015-04-01

    Magnesium peroxide is an excellent source of oxygen in agriculture applications, for instance it is used in waste management as a material for soil bioremediation to remove contaminants from polluted underground water, biological wastes treatment to break down hydrocarbon, etc. In the present study, sol-gel synthesis of magnesium peroxide (MgO2) nanoparticles is reported. Magnesium peroxide is odourless; fine peroxide which releases oxygen when reacts with water. During the sol-gel synthesis, the magnesium malonate intermediate is formed which was then calcinated to obtain MgO2 nanoparticles. The synthesized nanoparticles were characterized using Thermo gravimetric -Differential Thermal Analysis (TG- DTA), X-Ray Diffraction studies (XRD) and High Resolution Transmission Electron Microscope (HRTEM). Our study provides a clear insight that the formation of magnesium malonate during the synthesis was due to the reaction between magnesium acetate, oxalic acid and ethanol. In our study, we can conclude that the calcination temperature has a strong influence on particle size, morphology, monodispersity and the chemistry of the particles.

  3. Hydrogel membranes of PVAl/ clay by gamma radiation

    NASA Astrophysics Data System (ADS)

    de Oliveira, M. J. A.; Parra, D. F.; Amato, V. S.; Lugão, A. B.

    2013-03-01

    In the last decades several studies concerning the new methods for drug delivery system have been investigated. A new field known as "smart therapy" involves devices and drug delivery systems to detect, identify and treat the site affected by the disease, not interfering with the biological system. Cutaneous Leishmaniasis is an endemic disease that is characterized by the development of single or multiple localized lesions on exposed areas of skin and one coetaneous treatment could be a potential solution. The aim of this study was to obtain polymeric hydrogel matrices of poly(vinylalcohol)(PVAl) and chitosan with inorganic nanoparticles, which can release a drug according to the need of the treatment of injury caused by leishmania on the skin. The hydrogels matrices were obtained with PVAl/ chitosan and PVAl/ chitosan 0.5; 1.0 and 1.5% laponite RD clay, crosslinked by ionizing gamma radiation with dose of 25 kGy. The techniques used for characterization were swelling, gel fraction, Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TGA). After synthesis, the samples were immersed in distilled water and weighed in periods of time until 60 h for the swelling determination. The obtained results have indicated that the swelling of the membranes increases with clay concentration, in consequence of ionic groups present in the clay.

  4. Preparation, modification, and characterization of alginate hydrogel with nano-/microfibers: a new perspective for tissue engineering.

    PubMed

    Santana, Bianca Palma; Nedel, Fernanda; Piva, Evandro; de Carvalho, Rodrigo Varella; Demarco, Flávio Fernando; Carreño, Neftali Lenin Villarreal

    2013-01-01

    We aimed to develop an alginate hydrogel (AH) modified with nano-/microfibers of titanium dioxide (nfTD) and hydroxyapatite (nfHY) and evaluated its biological and chemical properties. Nano-/microfibers of nfTD and nfHY were combined with AH, and its chemical properties were evaluated by FTIR spectroscopy, X-ray diffraction, energy dispersive X-Ray analysis, and the cytocompatibility by the WST-1 assay. The results demonstrate that the association of nfTD and nfHY nano-/microfibers to AH did not modified the chemical characteristics of the scaffold and that the association was not cytotoxic. In the first 3 h of culture with NIH/3T3 cells nfHY AH scaffolds showed a slight increase in cell viability when compared to AH alone or associated with nfTD. However, an increase in cell viability was observed in 24 h when nfTD was associated with AH scaffold. In conclusion our study demonstrates that the combination of nfHY and nfTD nano-/microfibers in AH scaffold maintains the chemical characteristics of alginate and that this association is cytocompatible. Additionally the combination of nfHY with AH favored cell viability in a short term, and the addition of nfTD increased cell viability in a long term. PMID:23862142

  5. Enzymatic regulation of functional vascular networks using gelatin hydrogels

    PubMed Central

    Chuang, Chia-Hui; Lin, Ruei-Zeng; Tien, Han-Wen; Chu, Ya-Chun; Li, Yen-Cheng; Melero-Martin, Juan M.; Chen, Ying-Chieh

    2015-01-01

    To manufacture tissue engineering-based functional tissues, scaffold materials that can be sufficiently vascularized to mimic the functionality and complexity of native tissues are needed. Currently, vascular network bioengineering is largely carried out using natural hydrogels as embedding scaffolds, but most natural hydrogels have poor mechanical stability and durability, factors that critically limit their widespread use. In this study, we examined the suitability of gelatin-phenolic hydroxyl (gelatin-Ph) hydrogels that can be enzymatically crosslinked, allowing tuning of the storage modulus and the proteolytic degradation rate, for use as injectable hydrogels to support the human progenitor cell-based formation of a stable and mature vascular network. Porcine gelatin-Ph hydrogels were found to be cytocompatible with human blood-derived endothelial colony-forming cells and white adipose tissue-derived mesenchymal stem cells, resulting in >87% viability, and cell proliferation and spreading could be modulated by using hydrogels with different proteolytic degradability and stiffness. In addition, gelatin was extracted from mouse dermis and murine gelatin-Ph hydrogels were prepared. Importantly, implantation of human cell-laden porcine or murine gelatin-Ph hydrogels into immunodeficient mice resulted in the rapid formation of functional anastomoses between the bioengineered human vascular network and the mouse vasculature. Furthermore, the degree of enzymatic crosslinking of the gelatin-Ph hydrogels could be used to modulate cell behavior and the extent of vascular network formation in vivo. Our report details a technique for the synthesis of gelatin-Ph hydrogels from allogeneic or xenogeneic dermal skin and suggests that these hydrogels can be used for biomedical applications that require the formation of microvascular networks, including the development of complex engineered tissues. PMID:25749296

  6. Resilient self-assembling hydrogels from block copolypeptide amphiphiles

    NASA Astrophysics Data System (ADS)

    Nowak, Andrew Paul

    The ability to produce well defined synthetic polypeptides has been greatly improved by the discovery of transition metal species that mediate the controlled polymerization of N-carboxyanhydrides (NCAs). These metal species create a living polymerization system by producing control over chain length, low polydispersities, and the ability to form complex block architectures. We have applied this system to the synthesis of block copolypeptide amphiphiles. Initial block copolymers synthesized were composed of hydrophilic, cationic poly(L-Lysine) combined with hydrophobic, alpha-helical poly(L-Leucine). These Lysine- block-Leucine copolypeptides were found to form stiff, clear hydrogels at low concentration (˜1 wt%) in low ionic strength water. Based on this unexpected result we used the flexibility of our transition metal polymerization chemistry to better understand the nature and mechanisms of gel formation in these materials. Systematic changes to the original Lysine-block-Leucine copolypeptides were made by altering overall chain size, relative block length, polyelectrolyte charge, and hydrophobic secondary structure. Rheological characterization revealed that the strength of these hydrogels was primarily dependent on degree of polymerization, relative block length, and a well ordered secondary structure in the hydrophobic segment. The Lysine-block-Leucine hydrogels were formed by direct addition of water to dry polypeptide material which swelled to homogeneously fill the entire volume of liquid with no special processing. CryoTEM showed a percolating cellular network at ˜100nm that appears to be comprised of both membranes and fibers. Larger length scales studied with Laser Scanning Confocal Microscopy revealed a spontaneously formed microporous network with large (˜10mum) water rich voids. These hydrogels also displayed interesting mechanical properties including rapid recovery of solid like behavior after being sheared to a liquid and mechanical stability

  7. Synthesis and characterization of nanorods for magnetic rotational spectroscopy

    SciTech Connect

    Aprelev, Pavel; Gu, Yu; Burtovyy, Ruslan; Luzinov, Igor; Kornev, Konstantin G.

    2015-08-21

    Magnetic rotational spectroscopy (MRS) with magnetic nanoprobes is a powerful method for in-situ characterization of minute amounts of complex fluids. In MRS, a uniformly rotating magnetic field rotates magnetic micro- or nano-probes in the liquid and one analyzes the features of the probe rotation to extract rheological parameters of liquids. Magnetic properties of nanoprobes must be well characterized and understood to make results reliable and reproducible. Ni and Co nanorods synthesized by electrochemical template synthesis in alumina membranes are discussed in applications to MRS. We employ alternating gradient field magnetometry, X-ray diffraction, and magnetic force microscopy to evaluate and compare properties of these nanorods and study their performance as the MRS probes. It is shown that nickel nanorods do not seem to violate any assumptions of the MRS rigid dipole theory, while cobalt nanorods do.

  8. Synthesis and characterization of nanorods for magnetic rotational spectroscopy

    NASA Astrophysics Data System (ADS)

    Aprelev, Pavel; Gu, Yu; Burtovyy, Ruslan; Luzinov, Igor; Kornev, Konstantin G.

    2015-08-01

    Magnetic rotational spectroscopy (MRS) with magnetic nanoprobes is a powerful method for in-situ characterization of minute amounts of complex fluids. In MRS, a uniformly rotating magnetic field rotates magnetic micro- or nano-probes in the liquid and one analyzes the features of the probe rotation to extract rheological parameters of liquids. Magnetic properties of nanoprobes must be well characterized and understood to make results reliable and reproducible. Ni and Co nanorods synthesized by electrochemical template synthesis in alumina membranes are discussed in applications to MRS. We employ alternating gradient field magnetometry, X-ray diffraction, and magnetic force microscopy to evaluate and compare properties of these nanorods and study their performance as the MRS probes. It is shown that nickel nanorods do not seem to violate any assumptions of the MRS rigid dipole theory, while cobalt nanorods do.

  9. Synthesis and characterization of novel cellulose ether sulfates.

    PubMed

    Rohowsky, Juta; Heise, Katja; Fischer, Steffen; Hettrich, Kay

    2016-05-20

    The synthesis and characterization of novel cellulose sulfate derivatives was reported. Various cellulose ethers were prepared in a homogeneous reaction with common sulfating agents. The received product possess different properties in dependence on the reaction conditions like sulfating agent, solvent, reaction time and reaction temperature. The cellulose ether sulfates are all soluble in water, they rheological behavior could be determined by viscosity measurements and the determination of the sulfur content by elemental analysis lead to a resulting degree of substitution ascribed to sulfate groups (DSSul) of the product. A wide range of products from DSSul 0.1 to DSSul 2.7 will be obtained. Furthermore the cellulose sulfate ethers could be characterized by Raman spectroscopy. PMID:26917374

  10. Synthesis and Characterization of a Nanocrystalline Thoria Aerogel

    SciTech Connect

    Reibold, R A; Satcher, Jr, J H; Baumann, T F; Simpson, R L; Poco, J F

    2004-02-04

    We report the synthesis and characterization for the first example of a low-density nanocrystalline thoria aerogel. The monolithic aerogels were prepared through the solgel polymerization of hydrated thorium nitrate in ethanol using ammonium hydroxide and propylene oxide as gelation initiators. The dried ThO{sub 2} aerogel was characterized by high-resolution transmission electron microscopy (HRTEM) and nitrogen adsorption/desorption analyses. The aerogel network was determined to be composed of spherical primary particles with features in the 5-20 nm range. These particles were also determined to be highly crystalline as evidenced by the higher magnification TEM examination. The thoria aerogel possesses high surface area (120 m{sup 2}/g) and pore diameters in the micro- and mesoporous range.

  11. Synthesis and characterization of acidic mesoporous borosilicate thin films.

    PubMed

    Xiu, Tongping; Liu, Qian; Wang, Jiacheng

    2009-02-01

    Work on the synthesis and characterization of acidic wormhole-like ordered mesoporous borosilicate thin films (MBSTFs) on silicon wafers is described in this paper. The MBSTFs coated by the dip-coating method were prepared through an evaporation-induced self-assembly (EISA) process using nonionic block copolymers as structure-directing agents. Fourier transform infrared (FT-IR) spectroscopy confirmed the formation of borosiloxane bonds (Si-O-B). High-resolution transmission electron microscopy (HRTEM) and N2 sorption evidenced a wormhole-like mesoporous structure in the MBSTFs obtained. Scanning electron microscopy (SEM) images of the cross sections and surfaces of the samples showed that MBSTFs on silicon wafers were continuous, homogeneous and did not crack. The acidic properties of the MBSTFs were characterized by FT-IR spectra of chemisorbed pyridine. The MBSTFs thus prepared may find their future applications in many fields including chemical sensors, catalysis, optical coating, molecule separation, etc. PMID:19441565

  12. Sundew-Inspired Adhesive Hydrogels Combined with Adipose-Derived Stem Cells for Wound Healing.

    PubMed

    Sun, Leming; Huang, Yujian; Bian, Zehua; Petrosino, Jennifer; Fan, Zhen; Wang, Yongzhong; Park, Ki Ho; Yue, Tao; Schmidt, Michael; Galster, Scott; Ma, Jianjie; Zhu, Hua; Zhang, Mingjun

    2016-01-27

    The potential to harness the unique physical, chemical, and biological properties of the sundew (Drosera) plant's adhesive hydrogels has long intrigued researchers searching for novel wound-healing applications. However, the ability to collect sufficient quantities of the sundew plant's adhesive hydrogels is problematic and has eclipsed their therapeutic promise. Inspired by these natural hydrogels, we asked if sundew-inspired adhesive hydrogels could overcome the drawbacks associated with natural sundew hydrogels and be used in combination with stem-cell-based therapy to enhance wound-healing therapeutics. Using a bioinspired approach, we synthesized adhesive hydrogels comprised of sodium alginate, gum arabic, and calcium ions to mimic the properties of the natural sundew-derived adhesive hydrogels. We then characterized and showed that these sundew-inspired hydrogels promote wound healing through their superior adhesive strength, nanostructure, and resistance to shearing when compared to other hydrogels in vitro. In vivo, sundew-inspired hydrogels promoted a "suturing" effect to wound sites, which was demonstrated by enhanced wound closure following topical application of the hydrogels. In combination with mouse adipose-derived stem cells (ADSCs) and compared to other therapeutic biomaterials, the sundew-inspired hydrogels demonstrated superior wound-healing capabilities. Collectively, our studies show that sundew-inspired hydrogels contain ideal properties that promote wound healing and suggest that sundew-inspired-ADSCs combination therapy is an efficacious approach for treating wounds without eliciting noticeable toxicity or inflammation. PMID:26731614

  13. Temperature, pH and redox responsive cellulose based hydrogels for protein delivery.

    PubMed

    Dutta, Sujan; Samanta, Pousali; Dhara, Dibakar

    2016-06-01

    Cellulose based hydrogels are important due to their biocompatibility, non-toxicity and natural origin. In this work, a new set of pH, temperature and redox responsive hydrogels were prepared from carboxymethylcellulose (CMC) and poly(N-isopropylacrylamide). Copolymeric (CP) hydrogels were synthesized by copolymerizing N-isopropylacrylamide (NIPA) and methacrylated carboxymethylcellulose, semi-interpenetrating network (SIPN) hydrogels were prepared by polymerizing NIPA in presence of CMC. Two types of cross-linkers were used viz. N,N'-methylenebisacrylamide (BIS) and N,N'-bis(acryloyl)cystamine (CBA), a redox sensitive cross-linker. The structures of the hydrogels were characterized by FTIR and SEM studies. The CP hydrogels were found to be more porous than corresponding SIPNs which resulted in higher swelling for the CP hydrogels. Swelling for both the hydrogels were found to increase with CMC content. While the swelling of SIPN hydrogels showed discontinuous temperature dependency, CP hydrogels showed gradual decrease in water retention values with increase in temperature. CBA cross-linked hydrogels showed higher swelling in comparison to BIS cross-linked hydrogels. Additionally, lysozyme was loaded in the hydrogels and its in vitro release was studied in various pH, temperature and in presence of a reducing agent, glutathione (GSH). The release rate was found to be maximum at lower temperature, lower pH and in presence of GSH. PMID:26896728

  14. Hierarchical nanostructured conducting polymer hydrogel with high electrochemical activity

    PubMed Central

    Pan, Lijia; Yu, Guihua; Zhai, Dongyuan; Lee, Hye Ryoung; Zhao, Wenting; Liu, Nian; Wang, Huiliang; Tee, Benjamin C.-K.; Shi, Yi; Cui, Yi; Bao, Zhenan

    2012-01-01

    Conducting polymer hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels and organic conductors and have been used in many applications such as bioelectronics and energy storage devices. They are often synthesized by polymerizing conductive polymer monomer within a nonconducting hydrogel matrix, resulting in deterioration of their electrical properties. Here, we report a scalable and versatile synthesis of multifunctional polyaniline (PAni) hydrogel with excellent electronic conductivity and electrochemical properties. With high surface area and three-dimensional porous nanostructures, the PAni hydrogels demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (∼480 F·g-1), unprecedented rate capability, and cycling stability (∼83% capacitance retention after 10,000 cycles). The PAni hydrogels can also function as the active component of glucose oxidase sensors with fast response time (∼0.3 s) and superior sensitivity (∼16.7 μA·mM-1). The scalable synthesis and excellent electrode performance of the PAni hydrogel make it an attractive candidate for bioelectronics and future-generation energy storage electrodes. PMID:22645374

  15. Supported Molecular Catalysts: Synthesis, in-situ Characterization and Performance

    SciTech Connect

    James F. Haw

    2010-12-14

    The technological advantages of solid catalysts (robustness for operation at high temperatures, lack of corrosion, and ease of separation of products) can be combined with the advantages of soluble catalysts (e.g., selectivity) by synthesis of structurally discrete, nearly uniform catalysts on supports. Our goal is to synthesize, characterize, test, and model such catalysts and their reactions, thereby opening a door to unprecedented fundamental understanding of the properties of such materials. We employ molecular chemistry in nano-scale cages of zeolites and on surfaces of tailored porous solids for the precise synthesis of catalysts with discrete, uniform, well-defined sites, primarily mononuclear metal complexes, characterizing them (sometimes in the functioning state) with a broad range of complementary experimental techniques and using computational chemistry to interpret the results, map out reaction paths, provide bases for the design of new catalysts, improve methods of data analysis, and identify key experiments. The effort is directly in support of DOE's energy, environmental, and national security missions as well as the support of DOE’s basic science mission to develop the tools and understanding needed for the success of the applied mission areas. The research is demonstrating progress in understanding, modeling, and controlling chemical reactivity at interfaces to develop a fundamental understanding of how to control catalytic reactions for a broad range of applications.

  16. Biodegradable HEMA-based hydrogels with enhanced mechanical properties.

    PubMed

    Moghadam, Mohamadreza Nassajian; Pioletti, Dominique P

    2016-08-01

    Hydrogels are widely used in the biomedical field. Their main purposes are either to deliver biological active agents or to temporarily fill a defect until they degrade and are followed by new host tissue formation. However, for this latter application, biodegradable hydrogels are usually not capable to sustain any significant load. The development of biodegradable hydrogels presenting load-bearing capabilities would open new possibilities to utilize this class of material in the biomedical field. In this work, an original formulation of biodegradable photo-crosslinked hydrogels based on hydroxyethyl methacrylate (HEMA) is presented. The hydrogels consist of short-length poly(2-hydroxyethyl methacrylate) (PHEMA) chains in a star shape structure, obtained by introducing a tetra-functional chain transfer agent in the backbone of the hydrogels. They are cross-linked with a biodegradable N,O-dimethacryloyl hydroxylamine (DMHA) molecule sensitive to hydrolytic cleavage. We characterized the degradation properties of these hydrogels submitted to mechanical loadings. We showed that the developed hydrogels undergo long-term degradation and specially meet the two essential requirements of a biodegradable hydrogel suitable for load bearing applications: enhanced mechanical properties and low molecular weight degradation products. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1161-1169, 2016. PMID:26061346

  17. Physically crosslinked-sacran hydrogel films for wound dressing application.

    PubMed

    Wathoni, Nasrul; Motoyama, Keiichi; Higashi, Taishi; Okajima, Maiko; Kaneko, Tatsuo; Arima, Hidetoshi

    2016-08-01

    The thin hydrogel films consisting of water-swollen polymer networks can potentially be applied for biomedical fields. Recently, natural polysaccharides have great attentions to be developed as wound healing and protection. In the present study, we newly prepared and characterized a physically crosslinked-hydrogel film composed of a novel megamolecular polysaccharide sacran for wound dressing application. We successfully fabricated a physically crosslinked-sacran hydrogel film by a solvent-casting method. The thickness of a sacran hydrogel film was lower than that of a sodium alginate (Na-alginate) film. Importantly, the swollen ratio of a sacran hydrogel film in water at 24h was 19-fold, compared to initial weight. Meanwhile, a Na-alginate hydrogel film was completely broken apart after rehydration. Moreover, a sacran hydrogel film did not show any cytotoxicity on NIH3T3 cells, a murine fibroblast cell line. The in vivo skin hydration study revealed that a sacran hydrogel film significantly increased the moisture content on hairless mice skin and considerably improved wound healing ability, compared to control (non-treated), probably due to not only the moisturing effect but also the anti-inflammatory effect of sacran. These results suggest that sacran has the potential properties as a basic biomaterial in a hydrogel film for wound dressing application. PMID:27151668

  18. Preparation and characterization of poly(2-acrylamido-2-methylpropane-sulfonic acid)/Chitosan hydrogel using gamma irradiation and its application in wastewater treatment

    NASA Astrophysics Data System (ADS)

    Gad, Y. H.

    2008-09-01

    Radiation grafting of chitosan with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) has been successfully performed. The effect of absorbed dose (kGy) and the chitosan:AMPS ratio on graft hydrogelization was studied. The structure of the prepared hydrogel was confirmed using infrared spectroscopy (IR). Thermal properties were simultaneously studied by thermogravimetric analysis (TGA). The effect of the polymerization variables on the swelling % of the prepared hydrogel was investigated. The highest equilibrium degree of swelling (38.6 g/g) and gel % (94.7%) of the prepared chitosan-AMPS hydrogel was at 40% AMPS and absorbed dose of 10 kGy. The removal of methylene blue, acid red dye, Cd (II) and Cr (III) from composed wastewater was also investigated. The effect of pH, the chitosan:AMPS ratio and the concentration of the pollutant on the adsorption process were studied.

  19. Biomimetic hydrogel materials

    DOEpatents

    Bertozzi, Carolyn; Mukkamala, Ravindranath; Chen, Qing; Hu, Hopin; Baude, Dominique

    2000-01-01

    Novel biomimetic hydrogel materials and methods for their preparation. Hydrogels containing acrylamide-functionalized carbohydrate, sulfoxide, sulfide or sulfone copolymerized with a hydrophilic or hydrophobic copolymerizing material selected from the group consisting of an acrylamide, methacrylamide, acrylate, methacrylate, vinyl and a derivative thereof present in concentration from about 1 to about 99 wt %. and methods for their preparation. The method of use of the new hydrogels for fabrication of soft contact lenses and biomedical implants.

  20. Biomimetic Hydrogel Materials

    DOEpatents

    Bertozzi, Carolyn , Mukkamala, Ravindranath , Chen, Oing , Hu, Hopin , Baude, Dominique

    2003-04-22

    Novel biomimetic hydrogel materials and methods for their preparation. Hydrogels containing acrylamide-functionalized carbohydrate, sulfoxide, sulfide or sulfone copolymerized with a hydrophilic or hydrophobic copolymerizing material selected from the group consisting of an acrylamide, methacrylamide, acrylate, methacrylate, vinyl and a derivative thereof present in concentration from about 1 to about 99 wt %. and methods for their preparation. The method of use of the new hydrogels for fabrication of soft contact lenses and biomedical implants.

  1. Synthesis and characterization of pure Cu and CuO nano particles by solution combustion synthesis

    NASA Astrophysics Data System (ADS)

    Patil, Sarika P.; Patil, Shital P.; Puri, V. R.; Jadhav, L. D.

    2013-06-01

    The Cu and CuO nano particles were prepared by using solution combustion technique with copper nitrate as an oxidizer and citric acid as the fuel. The solution combustion synthesis (SCS) method provides the advanced ceramics, nano-composites and catalyst materials and also produces homogeneous, crystalline and un-agglomerated multi-component oxides. The pure CuO nano particles were prepared for rich oxidant to fuel ratio. As prepared powder were further calcined at 600 °C for 2 hrs. The powder was characterized by different techniques such as XRD, TG-DTA, and SEM etc.

  2. Photonic hydrogel sensors.

    PubMed

    Yetisen, Ali K; Butt, Haider; Volpatti, Lisa R; Pavlichenko, Ida; Humar, Matjaž; Kwok, Sheldon J J; Koo, Heebeom; Kim, Ki Su; Naydenova, Izabela; Khademhosseini, Ali; Hahn, Sei Kwang; Yun, Seok Hyun

    2016-01-01

    Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified. PMID:26485407

  3. Antifouling properties of hydrogels

    NASA Astrophysics Data System (ADS)

    Murosaki, Takayuki; Ahmed, Nafees; Gong, Jian Ping

    2011-12-01

    Marine sessile organisms easily adhere to submerged solids such as rocks, metals and plastics, but not to seaweeds and fishes, which are covered with soft and wet 'hydrogel'. Inspired by this fact, we have studied long-term antifouling properties of hydrogels against marine sessile organisms. Hydrogels, especially those containing hydroxy group and sulfonic group, show excellent antifouling activity against barnacles both in laboratory assays and in the marine environment. The extreme low settlement on hydrogels in vitro and in vivo is mainly caused by antifouling properties against the barnacle cypris.

  4. Removal of dyes from water using chitosan hydrogel/SiO2 and chitin hydrogel/SiO2 hybrid materials obtained by the sol-gel method.

    PubMed

    Copello, Guillermo J; Mebert, Andrea M; Raineri, M; Pesenti, Mariela P; Diaz, Luis E

    2011-02-15

    This work describes the synthesis of chitosan hydrogel/SiO(2) and chitin hydrogel/SiO(2) hybrid mesoporous materials obtained by the sol-gel method for their use as biosorbents. Their adsorption capabilities against four dyes (Remazol Black B, Erythrosine B, Neutral Red and Gentian Violet) were compared in order to evaluate chitin as a plausible replacement for chitosan considering its efficiency and lower cost. Both chitin and chitosan were used in the form of hydrogels. This allowed full compatibility with the ethanol release from tetraethoxysilane. The hybrid materials were characterized by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Nitrogen Adsorption Isotherms and (13)C solid-state Nuclear Magnetic Resonance. Adsorption experimental data were analyzed using Langmuir, Freundlich and Dubinin-Radushkevich isotherm models along with the evaluation of adsorption energy and standard free energy (ΔG(0)). The adsorption was observed to be pH dependent. The main mechanism of dye adsorption was found to be a spontaneous charge associated interaction, except for EB adsorption on chitin/SiO(2) matrix, which showed to involve a lower energy physical adsorption interaction. Aside from highly charged dyes the chitin containing matrix has similar or higher adsorption capacity than the chitosan one. PMID:21163576

  5. Hydrogels derived from demineralized and decellularized bone extracellular matrix

    PubMed Central

    Sawkins, M.J.; Bowen, W.; Dhadda, P.; Markides, H.; Sidney, L.E.; Taylor, A.J.; Rose, F.R.A.J.; Badylak, S.F.; Shakesheff, K.M.; White, L.J.

    2013-01-01

    The extracellular matrix (ECM) of mammalian tissues has been isolated, decellularized and utilized as a scaffold to facilitate the repair and reconstruction of numerous tissues. Recent studies have suggested that superior function and complex tissue formation occurred when ECM scaffolds were derived from site-specific homologous tissues compared with heterologous tissues. The objectives of the present study were to apply a stringent decellularization process to demineralized bone matrix (DBM), prepared from bovine bone, and to characterize the structure and composition of the resulting ECM materials and DBM itself. Additionally, we sought to produce a soluble form of DBM and ECM which could be induced to form a hydrogel. Current clinical delivery of DBM particles for treatment of bone defects requires incorporation of the particles within a carrier liquid. Differences in osteogenic activity, inflammation and nephrotoxicity have been reported with various carrier liquids. The use of hydrogel forms of DBM or ECM may reduce the need for carrier liquids. DBM and ECM hydrogels exhibited sigmoidal gelation kinetics consistent with a nucleation and growth mechanism, with ECM hydrogels characterized by lower storage moduli than the DBM hydrogels. Enhanced proliferation of mouse primary calvarial cells was achieved on ECM hydrogels, compared with collagen type I and DBM hydrogels. These results show that DBM and ECM hydrogels have distinct structural, mechanical and biological properties and have the potential for clinical delivery without the need for carrier liquids. PMID:23624219

  6. Conductive PANi/PEGDA macroporous hydrogels for nerve regeneration.

    PubMed

    Guarino, Vincenzo; Alvarez-Perez, Marco Antonio; Borriello, Anna; Napolitano, Teresa; Ambrosio, Luigi

    2013-01-01

    Only recently polymers with intrinsic conductive properties have been studied in relation to their incorporation into bioactive scaffolds for use in tissue engineering. The reason for this interest is that such scaffolds could electrically stimulate cells and thus regulate specific cellular activities, and by this means influence the process of regeneration of those tissues that respond to electrical impulses. In our work, macroporous hydrogels are developed with controlled pore morphology and conductive properties to enable sufficient cell signaling to supply events inherent to nerve regeneration. A hybrid material has been prepared by in situ precipitation of polyaniline (PANi) in polyethyleneglycol diacrylate (PEGDA) solution, followed by crosslinking via UV irradiation. A porous architecture, characterized by macropores from 136 μm to 158 μm in size, has been achieved by sodium chloride particle leaching. In this work, we demonstrate that PANi synthesis and hydrogel crosslinking combine to enable the design of materials with suitable conductive behaviour. The presence of PANi evidently increased the electrical conductivity of the hybrid material from (1.1 ± 0.5) × 10(-3) mS/cm with a PANi content of 3wt%. The hydrophilic nature of PANi also enhanced water retention/proton conductivity by more than one order of magnitude. In vitro studies confirmed that 3 wt% PANi also improve the biological response of PC12 and hMSC cells. Hybrid PANi/PEGDA macroporous hydrogels supplement new functionalities in terms of morphological and conductive properties, both of which are essential prerequisites to drive nerve cells in regenerative processes. PMID:23184787

  7. Characterization and sonochemical synthesis of black phosphorus from red phosphorus

    NASA Astrophysics Data System (ADS)

    Aldave, Sandra H.; Yogeesh, Maruthi N.; Zhu, Weinan; Kim, Joonseok; Sonde, Sushant S.; Nayak, Avinash P.; Akinwande, Deji

    2016-03-01

    Phosphorene is a new two-dimensional material which is commonly prepared by exfoliation from black phosphorus bulk crystals that historically have been synthesized from white phosphorus under high-pressure conditions. The few layers of phosphorene have a direct band gap in the range of 0.3-2 eV and high mobility at room temperature comparable to epitaxial graphene. These characteristics can be used for the design of high speed digital circuits, radio frequency circuits, flexible and printed systems, and optoelectronic devices. In this work, we synthesized black phosphorus from red phosphorus, which is a safer solid precursor, using sonochemistry. Furthermore, via a variety of microscopy and spectroscopy techniques, we report characterization results of the sonochemically synthesized black phosphorus in addition to the commercial black phosphorus. Finally, we describe the air stability of black phosphors and the crystalline structure of the synthesized material. This is the first result of sonochemical or solution-based synthesis of black phosphorus based on readily available low-cost red phosphorus. This solution-based synthesis of black phosphorus is suitable for printable applications of nanomaterial.

  8. Characterization of Aphanizomenon ovalisporum amidinotransferase involved in cylindrospermopsin synthesis

    PubMed Central

    Barón-Sola, Ángel; Gutiérrez-Villanueva, Miguel A; del Campo, Francisca F; Sanz-Alférez, Soledad

    2013-01-01

    An increasing abundance of Aphanizomenon ovalisporum in water bodies from diverse world regions has been reported in the last few years, with the majority of the isolated strains producing the toxin cylindrospermopsin (CYN), leading to a rise in ecological and health risks. The understanding of CYN synthesis is crucial in the control of CYN production. An amidinotransferase (AMDT) seems to be the first enzyme involved in the synthesis of CYN. In this study, we have cloned and overexpressed the aoaA gene from the constitutive CYN producer A. ovalisporum UAM-MAO. The recombinant purified AoaA was characterized, confirming that it is an l-arginine:glycine AMDT. It shows an optimal activity between 32 and 37°C, at pH from 8 to 9. The activity exhibits a mixed (ping-pong/sequential) kinetic mechanism, and is inhibited by the reaction product guanidine acetate (GAA) in a noncompetitive manner. Mg2+ stimulates AoaA activity while Co2+ and Mn2+ inhibit it. AoaA conserves the critical residues of the catalytic site and substrate specificity of AMDTs, as the previously reported AMDT from Cylindrospermopsis raciborskii Cyr. Both proteins can be included in a new group of prokaryotic AMDTs involved in CYN production. PMID:23533111

  9. Synthesis and characterization of nucleobase-carbon nanotube hybrids.

    PubMed

    Singh, Prabhpreet; Kumar, Jitendra; Toma, Francesca Maria; Raya, Jesus; Prato, Maurizio; Fabre, Bruno; Verma, Sandeep; Bianco, Alberto

    2009-09-23

    We report the synthesis and characterization of adenine-single-walled carbon nanotube (SWCNT) hybrid materials, where for the first time nucleobases are covalently attached to the exosurface of SWCNTs. The structural properties of all hybrids have been characterized using usual spectroscopic and microscopic techniques. The degree of functional groups for functionalized SWCNTs (f-SWCNTs) 2a and 2b is one adenine group for each 26 and 37 carbon atoms, respectively. Solid-state magic angle spinning (13)C NMR spectroscopy (MAS NMR) and electrochemistry have been also applied for the characterization of these f-SWCNTs. AFM images of f-SWCNT 2b showed an interesting feature of horizontally aligned nanotubes along the surface when deposited on highly oriented pyrolytic graphite surface. Furthermore, we evaluated the coordinating ability of these hybrid materials toward silver ions, and interestingly, we found a pattern of silver nanoparticles localized over the surface of the carbon nanotube network. The presence of aligned and randomly oriented CNTs and their ability to coordinate with metal ions make this class of materials very interesting for applications in the development of novel electronic devices and as new supports for different catalytic transformations. PMID:19673527

  10. Synthesis and Characterization of Bulk BC8 Si

    NASA Astrophysics Data System (ADS)

    Zhang, Haidong; Strobel, Timothy

    Silicon, an essential element for modern industry, has several allotropes existing at ambient conditions. Among them, one of the most important phases is the metastable Si-III (BC8) structure. Although it has been known since 1960s, experimental characterization of its properties is still rare primarily due to lack of large bulk samples. Common methods produce BC8 Si samples with the size of micrometers in dimension, preventing definitive experimental measurements. In this work we report synthesis of phase pure bulk BC8 Si with the size of a few millimeters through the multi-anvil press method. The structure was confirmed by powder X-ray diffraction and further supported by the Raman spectrum. Its electrical resistance exhibits clear temperature dependence, increasing from 300 K to 2K. A crossover region occurs around 80 K to 100 K, showing a stronger dependence below 80 K. We also report its optical properties, thermal stability and phonon density of states.

  11. Synthesis, Characterization and Application Of PbS Quantum Dots

    SciTech Connect

    Sarma, Sweety; Datta, Pranayee; Barua, Kishore Kr.; Karmakar, Sanjib

    2009-06-29

    Lead Chalcogenides (PbS, PbSe, PbTe) quantum dots (QDs) are ideal for fundamental studies of strongly quantum confined systems with possible technological applications. Tunable electronic transitions at near--infrared wavelengths can be obtained with these QDs. Applications of lead chalcogenides encompass quite a good number of important field viz. the fields of telecommunications, medical electronics, optoelectronics etc. Very recently, it has been proposed that 'memristor'(Memory resistor) can be realized in nanoscale systems with coupled ionic and electronic transports. The hystersis characteristics of 'memristor' are observed in many nanoscale electronic devices including semiconductor quantum dot devices. This paper reports synthesis of PbS QDs by chemical route. The fabricated samples are characterized by UV-Vis, XRD, SEM, TEM, EDS, etc. Observed characteristics confirm nano formation. I-V characteristics of the sample are studied for investigating their applications as 'memristor'.

  12. Nanoscale Synthesis and Characterization Laboratory Annual Report 2005

    SciTech Connect

    Hamza, A V; Lesuer, D R

    2006-01-03

    The Nanoscale Synthesis and Characterization Laboratory's (NSCL) primary mission is to create and advance interdisciplinary research and development opportunities in nanoscience and technology. The initial emphasis of the NSCL has been on development of scientific solutions in support of target fabrication for the NIF laser and other stockpile stewardship experimental platforms. Particular emphasis has been placed on the design and development of innovative new materials and structures for use in these targets. Projects range from the development of new high strength nanocrystalline alloys to graded density materials to high Z nanoporous structures. The NSCL also has a mission to recruit and train personnel for Lab programs such as the National Ignition Facility (NIF), Defense and Nuclear Technologies (DNT), and Nonproliferation, Arms control and International security (NAI). The NSCL continues to attract talented scientists to the Laboratory.

  13. Synthesis of Polymeric Microgels and their Characterization with Light Scattering

    NASA Astrophysics Data System (ADS)

    Gunder, Christian; Streletzky, Kiril A.; Freeman, Krista; Mino, Janna

    Polymeric microgels were synthesized in by chemically crosslinking hydroxypropylcellulose (HPC) chains in aqueous solutions of sodium hydroxide at temperatures above the low critical solution temperature (LCST) of HPC. In order to create a narrower size distribution of HPC microgels, surfactant was added. It was found that the LCST of the solution moved from 40C up to 80C with an increase in surfactant concentration from 0 to 12 g/l. Formed microgels were characterized by dynamic light scattering (DLS). Microgel solutions synthesized resulted in reasonably monodispersed nanoparticles with Rh of 90-150 nm below the transition, and Rh of 50-90 nm above the transition. The effect of synthesis temperature and crosslinker concentration on microgel size, polydispersity, and swelling ratio were also studied.

  14. Coats from Myxococcus xanthus: characterization and synthesis during myxospore differentiation.

    PubMed

    Kottel, R H; Bacon, K; Clutter, D; White, D

    1975-10-01

    An extracellular coat from glycerol-induced myxospores of Myxococcus xanthus has been isolated and characterized. Coats were examined chemically and by using both transmission and scanning electron microscopy. On a dry weight basis, approximately 75% of the coat is polysaccharide composed entirely of galactosamine and glucose. The remainder of the coat is protein (14%), glycine (8%), and organic phosphorus (less than 1%). Coats remained morphologically intact despite boiling in 10 M urea, sodium lauryl sulfate plus beta-mercaptoethanol, or extraction with warm phenol. Coats also resisted digestion with a variety of proteolytic and polysaccharide degrading enzymes. Synthesis of myxospore coat begins approximately 1 h after the addition of glycerol to a culture. One portion of the coat is complete by 5 to 6 h but additional material consisting primarily of glucose is added after 8 h. PMID:809426

  15. Synthesis and Characterization of Carbazole-Linked Porphyrin Tweezers.

    PubMed

    Chang, Yi; Michelin, Clément; Bucher, Léo; Desbois, Nicolas; Gros, Claude P; Piant, Sébastien; Bolze, Frédéric; Fang, Yuanyuan; Jiang, Xiaoqin; Kadish, Karl M

    2015-08-17

    Herein the synthesis, spectroscopic characterization, two-photon absorption and electrochemical properties of 3,6-disubstituted carbazole tweezers is reported. A dimer resulting from a Glaser homocoupling was isolated during a Sonogashira coupling reaction between a diethynyl-carbazole spacer and a 5-bromo-triarylporphyrin and the properties of this original compound were compared with the 3,6-disubstituted carbazole bisporphyrin tweezers. The dyads reported herein present a two-photon absorption maximum at 920 nm with two-photon absorption cross-section in the 1200 GM range. Despite a strong linear absorption in the Soret region and moderate fluorescence quantum yield, they both lead to a high brightness reaching 30 000 M(-1)  cm(-1) . PMID:26177731

  16. Synthesis and Characterization of Modified Phenylethynyl Terminated Polyimides

    NASA Technical Reports Server (NTRS)

    Chang, Alice C.

    1998-01-01

    As an ongoing effort to develop structural adhesives for high performance aerospace applications, recent work has focused on phenylethynyl terminated imide (PETI) oligomers. The work reported herein involves the synthesis and characterization of a series of phenylethynyl containing oligomers designated LARC (TM) MPEI (Modified Phenylethynyl Terminated Polyimide). These oligomers contain mixtures of linear, branched and star-shaped molecules. The fully imidized polymers exhibited minimum melt viscosity as low as 600 poise at 335 C. Ti/Ti lap shear specimens processed at 288 C under 15 psi showed tensile shear strength of approx. 6000 psi and 5200 psi at ambient and 350 F temperatures, respectively. The chemistry and properties of these new MPEIs are presented and compared to an optimized linear PETI, LaRC(Tm) -PETI-5.

  17. Synthesis and Characterization of SF-PPV-I

    NASA Technical Reports Server (NTRS)

    Wang, Y.; Fan, Z.; Taft, C.; Sun, S.

    2001-01-01

    Conjugated electro-active polymers find their potential applications in developing variety inexpensive and flexible shaped electronic and photonic devices, such as photovoltaic or photo/electro light emitting devices. In many of these opto-electronic polymeric materials, certain electron rich donors and electron deficient acceptors are needed in order to fine-tune the electronic or photonic properties of the desired materials and structures. While many donor type of conjugated polymers have been widely studied and developed in the past decades, there are relatively fewer acceptor type of conjugated polymers have been developed. Key acceptor type conjugated polymers developed so far include C60 and CN-PPV, and each has its limitations. Due to the complexity and diversity of variety future electronic materials and structural needs, alternative and synthetically amenable acceptor conjugated polymers need to be developed. In this paper, we present the synthesis and characterization of a new acceptor conjugated polymer, a sulfone derivatized polyphenylenevinylene "SF-PPV".

  18. Synthesis, characterization, and antimicrobial properties of copper nanoparticles

    PubMed Central

    Usman, Muhammad Sani; Zowalaty, Mohamed Ezzat El; Shameli, Kamyar; Zainuddin, Norhazlin; Salama, Mohamed; Ibrahim, Nor Azowa

    2013-01-01

    Copper nanoparticle synthesis has been gaining attention due to its availability. However, factors such as agglomeration and rapid oxidation have made it a difficult research area. In the present work, pure copper nanoparticles were prepared in the presence of a chitosan stabilizer through chemical means. The purity of the nanoparticles was authenticated using different characterization techniques, including ultraviolet visible spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The antibacterial as well as antifungal activity of the nanoparticles were investigated using several microorganisms of interest, including methicillin-resistant Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Salmonella choleraesuis, and Candida albicans. The effect of a chitosan medium on growth of the microorganism was studied, and this was found to influence growth rate. The size of the copper nanoparticles obtained was in the range of 2–350 nm, depending on the concentration of the chitosan stabilizer. PMID:24293998

  19. Antibacterial gold nanoparticles-biomass assisted synthesis and characterization.

    PubMed

    Badwaik, Vivek D; Willis, Chad B; Pender, Dillon S; Paripelly, Rammohan; Shah, Monic; Kherde, Yogesh A; Vangala, Lakshmisri M; Gonzalez, Matthew S; Dakshinamurthy, Rajalingam

    2013-10-01

    Xylose is a natural monosaccharide found in biomass such as straw, pecan shells, cottonseed hulls, and corncobs. Using this monosaccharide, we report the facile, green synthesis and characterization of stable xylose encapsulated gold nanoparticles (Xyl-GNPs) with potent antibacterial activity. Xyl-GNPs were synthesized using the reduction property of xylose in an aqueous solution containing choloraurate anions carried out at room temperature and atmospheric pressure. These nanoparticles were stable and near spherical in shape with an average diameter of 15 +/- 5 nm. Microbiological assay results showed the concentration dependent antibacterial activity of these particles against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) bacteria. Thus the facile, environmentally friendly Xyl-GNPs have many potential applications in chemical and biomedical industries, particularly in the development of antibacterial agents in the field of biomedicine. PMID:24015501

  20. Synthesis and characterization of a new silicone multiblock polymer

    SciTech Connect

    Riley, M.O.; Kolb, J.R.; Jessop, E.S.

    1982-05-10

    The Lawrence Livermore National Laboratory (LLNL) has an active interest in the synthesis of new polysiloxanes as base polymers for cellular silicone materials. These elastomers have properties uniquely suited to very specific engineering requirements. While the polymers which we have prepared via random equilibrium of various cyclic tetrasiloxanes have adequate properties for certain applications, there is evidence to suggest that alternating block polysiloxanes prepared via condensation-polymerization techniques have properties more suited to our end uses as flexible foam materials (cushions). The synthetic sequence developed to prepare these materials involves reactions of functionally terminated (silylamino and silanol) polysiloxane oligomers to produce alternating multiblock (ABAB...) materials of high molecular weight. Dialkylamines are condensation byproducts in this reaction. The analysis and characterization of these multiblock polymers is reported.

  1. Exchange-coupled nanocomposites: chemical synthesis, characterization and applications.

    PubMed

    Liu, Fei; Hou, Yanglong; Gao, Song

    2014-12-01

    Nanocomposites containing soft and hard magnetic phases have attracted immense attention for energy-related and biomedical applications. With exchange coupling between nanoscale grains in the composites, magnetization of the soft magnetic phase can rotate coherently with that of the hard magnetic phase. In particular, good control of the soft and hard phases at the nanoscale in the composites is of great importance for effective exchange coupling, allowing us to make the best of the strengths of soft and hard magnetic phases and to optimize the magnetic properties for targeted applications. In this review, we present the recent progress in the chemical synthesis and applications of exchange-coupled nanocomposites. Firstly, the principle of nanomagnetism and exchange coupling is introduced. Secondly, the characterization of exchange-coupled nanocomposites is summarized. Thirdly, the chemical methods for the production of different exchange-coupled nanocomposites are presented. Finally, applications of exchange-coupled nanocomposites in magnetic energy storage and biomedicine are addressed. PMID:25130706

  2. Boron-based nanostructures: Synthesis, functionalization, and characterization

    NASA Astrophysics Data System (ADS)

    Bedasso, Eyrusalam Kifyalew

    Boron-based nanostructures have not been explored in detail; however, these structures have the potential to revolutionize many fields including electronics and biomedicine. The research discussed in this dissertation focuses on synthesis, functionalization, and characterization of boron-based zero-dimensional nanostructures (core/shell and nanoparticles) and one-dimensional nanostructures (nanorods). The first project investigates the synthesis and functionalization of boron-based core/shell nanoparticles. Two boron-containing core/shell nanoparticles, namely boron/iron oxide and boron/silica, were synthesized. Initially, boron nanoparticles with a diameter between 10-100 nm were prepared by decomposition of nido-decaborane (B10H14) followed by formation of a core/shell structure. The core/shell structures were prepared using the appropriate precursor, iron source and silica source, for the shell in the presence of boron nanoparticles. The formation of core/shell nanostructures was confirmed using high resolution TEM. Then, the core/shell nanoparticles underwent a surface modification. Boron/iron oxide core/shell nanoparticles were functionalized with oleic acid, citric acid, amine-terminated polyethylene glycol, folic acid, and dopamine, and boron/silica core/shell nanoparticles were modified with 3-(amino propyl) triethoxy silane, 3-(2-aminoethyleamino)propyltrimethoxysilane), citric acid, folic acid, amine-terminated polyethylene glycol, and O-(2-Carboxyethyl)polyethylene glycol. A UV-Vis and ATR-FTIR analysis established the success of surface modification. The cytotoxicity of water-soluble core/shell nanoparticles was studied in triple negative breast cancer cell line MDA-MB-231 and the result showed the compounds are not toxic. The second project highlights optimization of reaction conditions for the synthesis of boron nanorods. This synthesis, done via reduction of boron oxide with molten lithium, was studied to produce boron nanorods without any

  3. Bacterial cellulose based hydrogel (BC-g-AA) and preliminary result of swelling behavior

    NASA Astrophysics Data System (ADS)

    Hakam, Adil; Lazim, Azwan Mat; Abdul Rahman, I. Irman

    2013-11-01

    In this study, hydrogel based on Bacterial cellulose (BC) or local known as Nata de Coco, which grafted with monomer: Acrylic acid (AA) is synthesis by using gamma radiation technique. These hydrogel (BC-g-AA) has unique characteristic whereby responsive to pH buffer solution.

  4. Bacterial cellulose based hydrogel (BC-g-AA) and preliminary result of swelling behavior

    SciTech Connect

    Hakam, Adil; Lazim, Azwan Mat; Abdul Rahman, I. Irman

    2013-11-27

    In this study, hydrogel based on Bacterial cellulose (BC) or local known as Nata de Coco, which grafted with monomer: Acrylic acid (AA) is synthesis by using gamma radiation technique. These hydrogel (BC-g-AA) has unique characteristic whereby responsive to pH buffer solution.

  5. N-succinyl chitosan–dialdehyde starch hybrid hydrogels for biomedical applications

    PubMed Central

    Kamoun, Elbadawy A.

    2015-01-01

    A new class of injectable, biocompatible and biodegradable hydrogel is reported. This hydrogel is derived from N-succinyl chitosan (SCS) mixed with water-soluble dialdehyde starch (DAS) without using a conventional chemical crosslinker. The hybrid hydrogel is formed owing to the Schiff’s base reaction between amine groups of SCS and dialdehyde groups of DAS to form —CH 000000000000 000000000000 000000000000 111111111111 000000000000 111111111111 000000000000 000000000000 000000000000 N— group. SCS, DAS, and SCS–DAS hybrid hydrogels were synthesized and then characterized by FTIR analysis spectroscopy. The influence of SCS:DAS ratio in hybrid polymers solution on physicochemical properties of resultant hydrogels (e.g. gelation time, gel fraction (%) and equilibrium swelling ratio), surface morphology, in vitro weight loss (%), and mechanical stability was examined. The results demonstrated that SCS content has a profound role for forming tighter crosslinked hybrid hydrogels, where the increase of SCS content reduces the time for hydrogel forming. Also, the water uptake and hydrolytic weight loss decrease. Meanwhile, the DAS content increases, and mechanical properties of SCS–DAS hybrid hydrogels decrease. Curcumin release profile and adhered HGF cells on hydrogel surface sharply influenced the SCS portion in hybrid hydrogel composition. The SCS–DAS hybrid hydrogel properties afforded a possible opportunity to be used as a covalent in situ forming hybrid hydrogels in biomedical applications such as, tissue engineering and cartilage repair. PMID:26843972

  6. Antibacterial and conductive injectable hydrogels based on quaternized chitosan-graft-polyaniline/oxidized dextran for tissue engineering.

    PubMed

    Zhao, Xin; Li, Peng; Guo, Baolin; Ma, Peter X

    2015-10-15

    Biomaterials with injectability, conductivity and antibacterial effect simultaneously have been rarely reported. Herein, we developed a new series of in situ forming antibacterial conductive degradable hydrogels using quaternized chitosan (QCS) grafted polyaniline with oxidized dextran as crosslinker. The chemical structures, morphologies, electrochemical property, conductivity, swelling ratio, rheological property, in vitro biodegradation and gelation time of hydrogels were characterized. Injectability was verified by in vivo subcutaneous injection on a Sprague Dawley rat. The antibacterial activity of the hydrogels was firstly evaluated employing antibacterial assay using Escherichia coli and Staphylococcus aureus in vitro. The hydrogels containing polyaniline showed enhanced antibacterial activity compared to QCS hydrogel, especially for hydrogels with 3 wt% polyaniline showing 95 kill% and 90kill% for E. coli and S. aureus, respectively. Compared with QCS hydrogel, the hydrogels with 3 wt% polyaniline still showed enhanced antibacterial activity for E. coli in vivo. The adipose-derived mesenchymal stem cells (ADMSCs) were used to evaluate the cytotoxicity of the hydrogels and hydrogels with polyaniline showed better cytocompatibility than QCS hydrogel. The electroactive hydrogels could significantly enhance the proliferation of C2C12 myoblasts compared to QCS hydrogel. This work opens the way to fabricate in situ forming antibacterial and electroactive degradable hydrogels as a new class of bioactive scaffolds for tissue regeneration applications. PMID:26272777

  7. Preparation of supramolecular hydrogel-enzyme hybrids exhibiting biomolecule-responsive gel degradation.

    PubMed

    Shigemitsu, Hajime; Fujisaku, Takahiro; Onogi, Shoji; Yoshii, Tatsuyuki; Ikeda, Masato; Hamachi, Itaru

    2016-09-01

    Hydrogelators are small, self-assembling molecules that form supramolecular nanofiber networks that exhibit unique dynamic properties. Development of supramolecular hydrogels that degrade in response to various biomolecules could potentially be used for applications in areas such as drug delivery and diagnostics. Here we provide a synthetic procedure for preparing redox-responsive supramolecular hydrogelators that are used to create hydrogels that degrade in response to oxidizing or reducing conditions. The synthesis takes ∼2-4 d, and it can potentially be carried out in parallel to prepare multiple hydrogelator candidates. This described solid-phase peptide synthesis protocol can be used to produce previously described hydrogelators or to construct a focused molecular library to efficiently discover and optimize new hydrogelators. In addition, we describe the preparation of redox-responsive supramolecular hydrogel-enzyme hybrids that are created by mixing aqueous solutions of hydrogelators and enzymes, which requires 2 h for completion. The resultant supramolecular hydrogel-enzyme hybrids exhibit gel degradation in response to various biomolecules, and can be rationally designed by connecting the chemical reactions of the hydrogelators with enzymatic reactions. Gel degradation in response to biomolecules as triggers occurs within a few hours. We also describe the preparation of hydrogel-enzyme hybrids arrayed on flat glass slides, enabling high-throughput analysis of biomolecules such as glucose, uric acid, lactate and so on by gel degradation, which is detectable by the naked eye. The protocol requires ∼6 h to prepare the hydrogel-enzyme hybrid array and to complete the biomolecule assay. PMID:27560177

  8. Hydrogels Constructed from Engineered Proteins.

    PubMed

    Li, Hongbin; Kong, Na; Laver, Bryce; Liu, Junqiu

    2016-02-24

    Due to their various potential biomedical applications, hydrogels based on engineered proteins have attracted considerable interest. Benefitting from significant progress in recombinant DNA technology and protein engineering/design techniques, the field of protein hydrogels has made amazing progress. The latest progress of hydrogels constructed from engineered recombinant proteins are presented, mainly focused on biorecognition-driven physical hydrogels as well as chemically crosslinked hydrogels. The various bio-recognition based physical crosslinking strategies are discussed, as well as chemical crosslinking chemistries used to engineer protein hydrogels, and protein hydrogels' various biomedical applications. The future perspectives of this fast evolving field of biomaterials are also discussed. PMID:26707834

  9. A mathematical model for electrical impedance spectroscopy of zwitterionic hydrogels.

    PubMed

    Feicht, Sarah E; Khair, Aditya S

    2016-08-17

    We report a mathematical model for ion transport and electrical impedance in zwitterionic hydrogels, which possess acidic and basic functional groups that carry a net charge at a pH not equal to the isoelectric point. Such hydrogels can act as an electro-mechanical interface between a relatively hard biosensor and soft tissue in the body. For this application, the electrical impedance of the hydrogel must be characterized to ensure that ion transport to the biosensor is not significantly hindered. The electrical impedance is the ratio of the applied voltage to the measured current. We consider a simple model system, wherein an oscillating voltage is applied across a hydrogel immersed in electrolyte and sandwiched between parallel, blocking electrodes. We employ the Poisson-Nernst-Planck (PNP) equations coupled with acid-base dissociation reactions for the charge on the hydrogel backbone to model the ionic transport across the hydrogel. The electrical impedance is calculated from the numerical solution to the PNP equations and subsequently analyzed via an equivalent circuit model to extract the hydrogel capacitance, resistance, and the capacitance of electrical double layers at the electrode-hydrogel interface. For example, we predict that an increase in pH from the isoelectric point, pH = 6.4 for a model PCBMA hydrogel, to pH = 8 reduces the resistance of the hydrogel by ∼40% and increases the double layer capacitance by ∼250% at an electrolyte concentration of 0.1 mM. The significant impact of charged hydrogel functional groups to the impedance is damped at higher electrolyte concentration. PMID:27464763

  10. Hypoxia-Inducible Hydrogels

    PubMed Central

    Park, Kyung Min; Gerecht, Sharon

    2014-01-01

    Oxygen is vital for the existence of all multicellular organisms, acting as a signaling molecule regulating cellular activities. Specifically, hypoxia, which occurs when the partial pressure of oxygen falls below 5%, plays a pivotal role during development, regeneration, and cancer. Here we report a novel hypoxia-inducible (HI) hydrogel composed of gelatin and ferulic acid that can form hydrogel networks via oxygen consumption in a laccase-mediated reaction. Oxygen levels and gradients within the hydrogels can be accurately controlled and precisely predicted. We demonstrate that HI hydrogels guide vascular morphogenesis in vitro via hypoxia-inducible factors activation of matrix metalloproteinases and promote rapid neovascularization from the host tissue during subcutaneous wound healing. The HI hydrogel is a new class of biomaterials that may prove useful in many applications, ranging from fundamental studies of developmental, regenerative and disease processes through the engineering of healthy and diseased tissue models towards the treatment of hypoxia-regulated disorders. PMID:24909742

  11. Chitosan Hydrogel in combination with Nerolidol for healing wounds.

    PubMed

    Ferreira, Maria Onaira Gonçalves; Leite, Layara Lorrana Ribeiro; de Lima, Idglan Sá; Barreto, Humberto Medeiros; Nunes, Lívio César Cunha; Ribeiro, Alessandra Braga; Osajima, Josy Anteveli; da Silva Filho, Edson Cavalcanti

    2016-11-01

    Chitosan is a natural polymer with antibacterial property, that is biodegradable, extremely abundant and non-toxic. This study aimed to develop and characterize chitosan hydrogels in combination with nerolidol, in order to optimize the antimicrobial and healing properties. The hydrogels were prepared using a reaction of the chitosan with acetic acid solution, followed by the addition of 2 or 4% of the nerolidol. Using thermogravimetry, differential scanning calorimetry and infrared spectroscopy, the incorporation of nerolidol in the hydrogel was confirmed. Direct contact tests using hydrogels and Staphylococcus aureus showed a synergistic effect in the materials, enabling total inhibition of bacterial growth. The hydrogel containing 2% nerolidol showed excellent healing effects. The beginning of re-epithelialization and reorganization of collagen was already observed on the 7th day of treatment. The material created proofed to be promising as a healing and antibacterial agent. PMID:27516288

  12. Metallic glass nanofibers in future hydrogel-based scaffolds.

    PubMed

    Sadeghian, Ramin Banan; Ahadian, Samad; Yaginuma, Shin; Ramón-Azcón, Javier; Liang, Xiaobin; Nakajima, Ken; Shiku, Hitoshi; Matsue, Tomokazu; Nakayama, Koji S; Khademhosseini, Ali

    2014-01-01

    Electrically conductive reinforced hydrogels offer a wide range of applications as three-dimensional scaffolds in tissue engineering. We report electrical and mechanical characterization of methacrylated gelatin (GelMA) hydrogel, containing palladium-based metallic glass nanofibers (MGNF). Also we show that the fibers are biocompatible and C2C12 myoblasts in particular, planted into the hybrid hydrogel, tend to attach to and elongate along the fibers. The MGNFs in this work were created by gas atomization. Ravel of fibers were embedded in the GelMA prepolymer in two different concentrations (0.5 and 1.0 mg/ml), and then the ensemble was cured under UV light, forming the hybrid hydrogel. The conductivity of the hybrid hydrogel was proportional to the fiber concentration. PMID:25571184

  13. Multiscale Surface-Attached Hydrogel Thin Films with Tailored Architecture.

    PubMed

    Chollet, Benjamin; Li, Mengxing; Martwong, Ekkachai; Bresson, Bruno; Fretigny, Christian; Tabeling, Patrick; Tran, Yvette

    2016-05-11

    A facile route for the fabrication of surface-attached hydrogel thin films with well-controlled chemistry and tailored architecture on wide range of thickness from nanometers to micrometers is reported. The synthesis, which consists in cross-linking and grafting the preformed and ene-reactive polymer chains through thiol-ene click chemistry, has the main advantage of being well-controlled without the addition of initiators. As thiol-ene click reaction can be selectively activated by UV-irradiation (in addition to thermal heating), micropatterned hydrogel films are easily synthesized. The versatility of our approach is illustrated by the possibility to fabricate various chemical polymer networks, like stimuli-responsive hydrogels, on various solid substrates, such as silicon wafers, glass, and gold surfaces. Another attractive feature is the development of new complex hydrogel films with targeted architecture. The fabrication of various architectures for polymer films is demonstrated: multilayer hydrogel films in which single-networks are stacked one onto the other, interpenetrating networks films with mixture of two networks in the same layer, and nanocomposite hydrogel films where nanoparticles are stably trapped inside the mesh of the network. Thanks to its simplicity and its versatility this novel approach to surface-attached hydrogel films should have a strong impact in the area of polymer coatings. PMID:27008162

  14. Synthesis and Characterization of Polydiacetylene Films and Nanotubes

    PubMed Central

    Gatebe, Erastus; Herron, Hayley; Zakeri, Rashid; Rajasekaran, Pradeep Ramiah; Aouadi, Samir; Kohli, Punit

    2009-01-01

    We report here the synthesis and characterization of polydiacetylene (PDA) films and nanotubes using layer-by-layer (LBL) chemistry. 10,12-Docosadiyndioic acid (DCDA) monomer was self-assembled on flat surfaces and inside of nanoporous alumina templates. UV irradiation of DCDA provided polymerized-DCDA (PDCDA) films and nanotubes. We have used zirconium-carboxylate interlayer chemistry to synthesize PDCDA multilayers on flat surfaces and in nanoporous template. PDCDA multilayers were characterized using optical (UV–vis, fluorescence, ellipsometry, FTIR) spectroscopies, ionic current–voltage (I–V) analysis, and scanning electron microscopy. Ellipsometry, FTIR, electronic absorption and emission spectroscopies showed a uniform DCDA deposition at each deposition cycle. Our optical spectroscopic analysis indicates that carboxylate-zirconium interlinking chemistry is robust. To explain the disorganization in the alkyl portion of PDCDA multilayer films, we propose carboxylate-zirconium interlinkages act as “locks” in between PDCDA layers which restrict the movement of alkyl portion in the films. Because of this locking, the induced-stresses in the polymer chains can not be efficiently relieved. Our ionic resistance data from I–V analysis correlate well with calculated resistance at smaller number of PDCDA layers but significantly deviated for thicker PDCDA nanotubes. These differences were attributed to ion-blocking because some of the PDCDA nanotubes were totally closed and the nonohmic and permselective ionic behaviors when the diameter of the pores approaches the double-layer thickness of the solution inside of the nanotubes. PMID:18823090

  15. Synthesis and characterization of N-doped zinc oxide nanotetrapods

    NASA Astrophysics Data System (ADS)

    Al Rifai, S. A.; Kulnitskiy, B. A.

    2016-05-01

    Nitrogen-doped (N-doped) self-assembled nanotetrapods ZnO were synthesized via chemical vapor deposition process using N2O as a dopant source via vapor-solid (VS) growth. The decomposition of N2O gas giving NO and NO2 during the synthesis provided successful N-doping of the sample. All samples (N-doped and undoped) were characterized by XRD, SEM, TEM, EDX, photoluminescence (PL), Fourier transform infrared (FT-IR), and diffuse reflection spectra. After nitrogen-doping process, N-doped ZnO samples show the change in structural and optical properties. The detailed structure and the growth mechanism of individual ZnO tetrapod is characterized by TEM and SEM investigations. The TEM study gives the direct assumption about the formation of zincblende (sphalerite) structure on the initial stage of growth of N-doped tetrapods. Besides, SEM observation indicated that tetrapods have perfect tetrahedral symmetry. N-Doped ZnO samples exhibit a broad orange-red PL emission band, peaking near 2.1 eV, in good agreement with the deep-acceptor model for the nitrogen impurity. An IR absorption peak at 3146 cm-1 at room temperature was observed for N-doped sample. This peak has been unambiguously assigned to N-H complex.

  16. Synthesis and characterization of porous hydroxyapatite and hydroxyapatite coatings

    SciTech Connect

    Nieh, T G; Choi, B W; Jankowski, A F

    2000-10-25

    A technique is developed to construct bulk hydroxyapatite (HAp) with different cellular structures. The technique involves the initial synthesis of nanocrystalline hydroxyapatite powder from an aqueous solution using water-soluble compounds and then followed by spray drying into agglomerated granules. The granules were further cold pressed and sintered into bulks at elevated temperatures. The sintering behavior of the HAp granules was characterized and compared with those previously reported. Resulting from the fact that the starting HAp powders were extremely fine, a relatively low activation energy for sintering was obtained. In the present study, both porous and dense structures were produced by varying powder morphology and sintering parameters. Porous structures consisting of open cells were constructed. Sintered structures were characterized using scanning electron microscopy and x-ray tomography. In the present paper, hydroxyapatite coatings produced by magnetron sputtering on silicon and titanium substrates will also be presented. The mechanical properties of the coatings were measured using nanoindentation techniques and microstructures examined using transmission electron microscopy.

  17. Synthesis and characterization of anodized titanium-oxide nanotube arrays

    SciTech Connect

    Hu, Michael Z.; Lai, Peng; Bhuiyan, Md S; Tsouris, Costas; Gu, Baohua; Paranthaman, Mariappan Parans; Gabitto, Jorge; Harrison, L. D.

    2009-01-01

    Anodized titanium-oxide containing highly ordered, vertically oriented TiO2 nanotube arrays is a nanomaterial architecture that shows promise for diverse applications. In this paper, an anodization synthesis using HF-free aqueous solution is described. The anodized TiO2 film samples (amorphous, anatase, and rutile) on titanium foils were characterized with scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Additional characterization in terms of photocurrent generated by an anode consisting of a titanium foil coated by TiO2 nanotubes was performed using an electrochemical cell. A platinum cathode was used in the electrochemical cell. Results were analyzed in terms of the efficiency of the current generated, defined as the ratio of the difference between the electrical energy output and the electrical energy input divided by the input radiation energy, with the goal of determining which phase of TiO2 nanotubes leads to more efficient hydrogen production. It was determined that the anatase crystalline structure converts light into current more efficiently and is therefore a better photocatalytic material for hydrogen production via photoelectrochemical splitting of water.

  18. Injectable micellar supramolecular hydrogel for delivery of hydrophobic anticancer drugs.

    PubMed

    Fu, CuiXiang; Lin, XiaoXiao; Wang, Jun; Zheng, XiaoQun; Li, XingYi; Lin, ZhengFeng; Lin, GuangYong

    2016-04-01

    In this paper, an injectable micellar supramolecular hydrogel composed of α-cyclodextrin (α-CD) and monomethoxy poly(ethylene glycol)-b-poly(ε-caplactone) (MPEG5000-PCL5000) micelles was developed by a simple method for hydrophobic anticancer drug delivery. By mixing α-CD aqueous solution and MPEG5000-PCL5000 micelles, an injectable micellar supramolecular hydrogel could be formed under mild condition due to the inclusion complexation between α-CD and MPEG segment of MPEG5000-PCL5000 micelles. The resultant supramolecular hydrogel was thereafter characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The effect of α-CD amount on the gelation time, mechanical strength and thixotropic property was studied by a rheometer. Payload of hydrophobic paclitaxel (PTX) to supramolecular hydrogel was achieved by encapsulation of PTX into MPEG5000-PCL5000 micelles prior mixing with α-CD aqueous solution. In vitro release study showed that the release behavior of PTX from hydrogel could be modulated by change the α-CD amount in hydrogel. Furthermore, such supramolecular hydrogel could enhance the biological activity of encapsulated PTX compared to free PTX, as indicated by in vitro cytotoxicity assay. All these results indicated that the developed micellar supramolecular hydrogel might be a promising injectable drug delivery system for anticancer therapy. PMID:26886821

  19. Injectable hybrid hydrogels of hyaluronic Acid crosslinked by well-defined synthetic polycations: preparation and characterization in vitro and in vivo.

    PubMed

    Cross, Daisy; Jiang, Xiaoze; Ji, Weihang; Han, Wenqing; Wang, Chun

    2015-05-01

    An injectable hybrid hydrogel system was developed consisting of hyaluronic acid (HA) crosslinked by well-defined block copolymers of the cationic poly(2-aminoethyl methacrylate) (PAEM) and polyethylene glycol (PEG). Robust, shear-thinning hybrid hydrogel was produced by mixing HA and 4-arm star PEG-PAEM block copolymer at 1:1 charge ratio. The encapsulation and release of highly viable human mesenchymal stem cells in physiological media was demonstrated. After subcutaneous injection of the hybrid gel in mice, mild but resolvable inflammatory response was observed. This hybrid gel could serve as a model system for studying structure-function relationship of polyelectrolyte hydrogels and as a practical injectable biomaterial for medical applications. PMID:25630277

  20. Synthesis and characterization of hexaarylbenzenes with five or six different substituents enabled by programmed synthesis

    NASA Astrophysics Data System (ADS)

    Suzuki, Shin; Segawa, Yasutomo; Itami, Kenichiro; Yamaguchi, Junichiro

    2015-03-01

    Since its discovery in 1825, benzene has served as one of the most used and indispensable building blocks of chemical compounds, ranging from pharmaceuticals and agrochemicals to plastics and those used in organic electronic devices. Benzene has six hydrogen atoms that can each be replaced by different substituents, which means that the structural diversity of benzene derivatives is intrinsically extraordinary. The number of possible substituted benzenes from n different substituents is (2n + 2n2 + 4n3 + 3n4 + n6)/12. However, owing to a lack of general synthetic methods for making multisubstituted benzenes, this potentially huge structural diversity has not been fully exploited. Here, we describe a programmed synthesis of hexaarylbenzenes using C-H activation, cross-coupling and [4+2] cycloaddition reactions. The present method allows for the isolation and structure-property characterization of hexaarylbenzenes with distinctive aryl substituents at all positions for the first time. Moreover, the established protocol can be applied to the synthesis of tetraarylnaphthalenes and pentaarylpyridines.

  1. Hydrothermal synthesis and characterization of zirconia based catalysts

    SciTech Connect

    Caillot, T. Salama, Z.; Chanut, N.; Cadete Santos Aires, F.J.; Bennici, S.; Auroux, A.

    2013-07-15

    In this work, three equimolar mixed oxides ZrO{sub 2}/CeO{sub 2}, ZrO{sub 2}/TiO{sub 2}, ZrO{sub 2}/La{sub 2}O{sub 3} and a reference ZrO{sub 2} have been synthesized by hydrothermal method. The structural and surface properties of these materials have been fully characterized by X-ray diffraction, transmission electron microscopy, surface area measurement, chemical analysis, XPS, infrared spectroscopy after adsorption of pyridine and adsorption microcalorimetry of NH{sub 3} and SO{sub 2} probe molecules. All investigated mixed oxides are amphoteric and possess redox centers on their surface. Moreover, hydrothermal synthesis leads to catalysts with higher surface area and with better acid–base properties than classical coprecipitation method. Both Lewis and Brønsted acid sites are present on the surface of the mixed oxides. Compared to the other samples, the ZrO{sub 2}/TiO{sub 2} material appears to be the best candidate for further application in acid–base catalysis. - Graphical abstract: Mesoporous amorphous phase with a high surface area of titania zirconia mixed oxide obtained by hydrothermal preparation. - Highlights: • Three zirconia based catalysts and a reference were prepared by hydrothermal synthesis. • Mixed oxides present larger surface areas than the reference ZrO{sub 2}. • ZrO{sub 2}/TiO{sub 2} catalyst presents a mesoporous structure with high surface area. • ZrO{sub 2}/TiO{sub 2} catalyst presents simultaneously strong acidic and basic properties.

  2. Vanadium oxide based materials: Synthesis, characterization and gas sensing properties

    NASA Astrophysics Data System (ADS)

    Ayesh, Samar I.

    In recent years, the demand for gas sensors based on safety and process control requirements has been expanding. The reason for such demand sterns from environmental and safety concerns since the toxic gases released from automobile exhausts and chemical plants can directly or indirectly pollute our environment and affect our health. Among the chemicals studied, nitrogen oxide (NOx) gases are among the most dangerous air pollutants. Transition metal oxide clusters (or polyoxometalates) provide an exciting opportunity for the design and synthesis of a new generation of materials for efficient NOx sensing. Polyoxometalates are an important and fast emerging class of compounds that exhibit many remarkable properties. Chapter 1 provides introduction and background of chemical sensors. It describes the need for gas sensors and the current status of research in the area of NOx gas sensors in particular. A description of polyoxmetalates and their relevance as potential novel gas sensor materials is also given. Chapter 2 describes the synthesis and characterization by FTIR spectroscopy, elemental analysis, thermogravimetric analysis, manganometric titration, bond valence sum calculation, temperature dependent magnetic properties studies, electron paramagnetic resonance, and complete single crystal X-ray diffraction analysis of newly prepared vanadium oxide based-systems that have been discovered during the course of this work. First, the system containing arrays of decavanadates networked by extensive hydrogen bonding with cyclic nitrogen bases are described. This is followed by the mixed-valence vanadium oxide cluster, [VV 13VIV3O42(Cl)]-7, containing a hitherto unknown vanadium oxide framework structure. Finally the synthesis of 3D-framework materials is described. These compounds have highly symmetrical closely related three-dimensional framework structures consisting vanadium oxide shells {V18O42(XO4)} linked via heterometallic atoms {M' = Cd, Zn} into three

  3. Synthesis and characterization of aluminosilicate catalyst impregnated by nickel oxide

    NASA Astrophysics Data System (ADS)

    Maulida, Iffana Dani; Sriatun, Taslimah

    2015-09-01

    Aluminosilicate as a catalyst has been synthesized by pore-engineering using CetylTrimethylAmmonium-Bromide (CTAB) as templating agent. It can produce bigger aluminosilicate pore therefore it will be more suitable for bulky molecule. The aims of this research are to synthesize aluminosilicate supported by Nickel, using CTAB surfactant as templating agent for larger pore radius than natural zeolite and characterize the synthesis product, consist of total acid sites and surface area characteristic. This research has been done with following steps. First, making sodium silicate and sodium aluminate. Second, aluminosilicate was synthesized by direct methods, calcined at 550, 650 and 750°C variation temperature, characterized product by X-RD and FTIR spectrometer. Third, NiCl2 was impregnated to the aluminosilicate that has the best cristallinity and main TO4 functional groups product (550 sample). Variation of NiCl2:aluminosilicate (w/w) ratio were 25%:75%, 50%:50% and 75%:25%. Last but not least characterization of catalytic properties was performed. It comprised total acidity test (gravimetric method) and Surface Area Analyzer. The result shows that the product synthesized by direct method at 550oC calcination temperature has the best cristallinity and main functional groups of TO4. The highest total acid sites was 31.6 mmole/g (Imp-A sample). Surface Area Analyzer shows that Imp-B sample has the best pore distribution and highest total pore volume and specific surface area with value 32.424 cc/g and 46.8287 m2/g respectively. We can draw the conclusion that the most potential catalyst is Imp-A sample compared to Imp-B and Imp-C because it has the highest total acid sites. However the most effective catalyst used for product selectivity was Imp-B sample among all samples.

  4. β-Cyclodextrin hydrogels for the ocular release of antibacterial thiosemicarbazones.

    PubMed

    Glisoni, Romina J; García-Fernández, María J; Pino, Marylú; Gutkind, Gabriel; Moglioni, Albertina G; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Sosnik, Alejandro

    2013-04-01

    Two types of hydrophilic networks with conjugated beta-cyclodextrin (β-CD) were developed with the aim of engineering useful platforms for the localized release of an antimicrobial 5,6-dimethoxy-1-indanone N4-allyl thiosemicarbazone (TSC) in the eye and its potential application in ophthalmic diseases. Poly(2-hydroxyethyl methacrylate) soft contact lenses (SCLs) displaying β-CD, namely pHEMA-co-β-CD, and super-hydrophilic hydrogels (SHHs) of directly cross-linked hydroxypropyl-β-CD were synthesized and characterized regarding their structure (ATR/FT-IR), drug loading capacity, swelling and in vitro release in artificial lacrimal fluid. Incorporation of TSC to the networks was carried out both during polymerization (DP method) and after synthesis (PP method). The first method led to similar drug loads in all the hydrogels, with minor drug loss during the washing steps to remove unreacted monomers, while the second method evidenced the influence of structural parameters on the loading efficiency (proportion of CD units, mesh size, swelling degree). Both systems provided a controlled TSC release for at least two weeks, TSC concentrations (up to 4000μg/g dry hydrogel) being within an optimal therapeutic window for the antimicrobial ocular treatment. Microbiological tests against P. aeruginosa and S. aureus confirmed the ability of TSC-loaded pHEMA-co-β-CD network to inhibit bacterial growth. PMID:23499082

  5. Thermal-Responsive Behavior of a Cell Compatible Chitosan/Pectin Hydrogel.

    PubMed

    Birch, Nathan P; Barney, Lauren E; Pandres, Elena; Peyton, Shelly R; Schiffman, Jessica D

    2015-06-01

    Biopolymer hydrogels are important materials for wound healing and cell culture applications. While current synthetic polymer hydrogels have excellent biocompatibility and are nontoxic, they typically function as a passive matrix that does not supply any additional bioactivity. Chitosan (CS) and pectin (Pec) are natural polymers with active properties that are desirable for wound healing. Unfortunately, the synthesis of CS/Pec materials have previously been limited by harsh acidic synthesis conditions, which further restricted their use in biomedical applications. In this study, a zero-acid hydrogel has been synthesized from a mixture of chitosan and pectin at biologically compatible conditions. For the first time, we demonstrated that salt could be used to suppress long-range electrostatic interactions to generate a thermoreversible biopolymer hydrogel that has temperature-sensitive gelation. Both the hydrogel and the solution phases are highly elastic, with a power law index of close to -1. When dried hydrogels were placed into phosphate buffered saline solution, they rapidly rehydrated and swelled to incorporate 2.7× their weight. As a proof of concept, we removed the salt from our CS/Pec hydrogels, thus, creating thick and easy to cast polyelectrolyte complex hydrogels, which proved to be compatible with human marrow-derived stem cells. We suggest that our development of an acid-free CS/Pec hydrogel system that has excellent exudate uptake, holds potential for wound healing bandages. PMID:25932898

  6. Preparation and characterization of hybrid pH-sensitive hydrogels of chitosan-co-acrylic acid for controlled release of verapamil.

    PubMed

    Ranjha, Nazar M; Ayub, Gohar; Naseem, Shahzad; Ansari, Muhammad Tayyab

    2010-10-01

    In the present work crosslinked hydrogels based on chitosan (CS) and acrylic acid (AA) were prepared by free radical polymerization with various feed compositions using N,N methylenebisacrylamide (MBA) as crosslinking agent. Benzoyl peroxide was used as catalyst. Fourier transform infrared spectra (FTIR) confirmed the formation of the crosslinked hydrogels. This hydrogel is formed due to electrostatic interaction between cationic groups in CS and anionic groups in AA. Prepared hydrogels were used for dynamic and equilibrium swelling studies. For swelling behavior, effect of pH, polymeric and monomeric compositions and degree of crosslinking were investigated. Swelling studies were performed in USP phosphate buffer solutions of varying pH 1.2, 5.5, 6.5 and 7.5. Results showed that swelling increased by increasing AA contents in structure of hydrogels in solutions of higher pH values. This is due to the presence of more carboxylic groups available for ionization. On the other hand by increasing the chitosan content swelling increased in a solution of acidic pH, but this swelling was not significant and it is due to ionization of amine groups present in the structure of hydrogel. Swelling decreased with increase in crosslinking ratio owing to tighter hydrogel structure. Porosity and sol-gel fraction were also measured. With increase in CS and AA contents porosity and gel fraction increased, whereas by increasing MBA content porosity decreased and gel fraction increased. Furthermore, diffusion coefficient (D) and the network parameters i.e., the average molecular weight between crosslinks (M(c)), polymer volume fraction in swollen state (V(2s)), number of repeating units between crosslinks (M(r)) and crosslinking density (q) were calculated using Flory-Rehner theory. Selected samples were loaded with a model drug verapamil. Release of verapamil depends on the ratios of CS/AA, degree of crosslinking and pH of the medium. The release mechanisms were studied by fitting

  7. Synthesis and characterization of macromolecular layers grafted to polymer surfaces

    NASA Astrophysics Data System (ADS)

    Burtovyy, Oleksandr

    The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility. Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to polymer substrates. Specifically, attachment of functional polymers via a "grafting to" approach has been extensively studied using PET and nylon model substrates. First, poly(glycidyl methacrylate) was used to introduce permanent functionalities to the model substrates by anchoring it to model films. Then, three different functional polymers were grafted on top of the previous layer. As one part of this study, the temperature and time dependence of grafting functional layers were studied. The surface coverage by hydrophobic polymer was determined from experimental data and predicted by a model. In general, the model has a high degree of predictive capability. Next, surface modification of polymeric fibers and membranes is presented as an important application of the polymer thin layers targeted in the study. Specifically, the procedures developed for surface modification of model substrates was employed for modification of PET, nylon, and cotton fabrics as well as PET track-etched membranes. Since epoxy groups are highly reactive in various chemical reactions, the approach becomes virtually universal, allowing both various surfaces and end-functionalized macromolecules to be used in the grafted layer synthesis. PET

  8. Synthesis and characterization of tridecameric Group 13 hydroxide clusters

    NASA Astrophysics Data System (ADS)

    Mensinger, Zachary Lee

    In the research area of Group 13 hydroxide clusters, progress is often hampered by difficult and inefficient synthetic procedures. This has greatly limited the numerous potential applications of Group 13 hydroxide compounds, many of which require large amounts of material. Most relevant to this dissertation is their application as precursors for high quality amorphous metal oxide thin films. Addressing this issue, this dissertation presents a series of Group 13 containing hydroxide compounds of general formula [M13(mu 3-OH)6(mu-OH)18(H2O)24](NO 3)15 which are generated through an efficient, scalable synthetic procedure. Throughout this dissertation, the compounds are generally referred to by their metal content, i.e. [Ga13(mu3-OH) 6(mu-OH)18(H2O)24](NO3) 15 is designated as Ga13. Chapter I reviews the literature of inorganic and ligand-supported Group 13 hydroxide compounds with the aim of identifying common structural trends in metal composition and coordinating ligands. This summary is limited to clusters of aluminum, gallium, and indium. Chapter II describes in detail the synthesis and characterization of one such cluster, Al13. Following this in Chapter III is the description of the first heterometallic Group 13 hydroxide compound, Ga7In 6, which along with Ga13 was used as a precursor material for metal oxide thin films in collaboration with Professor Doug Keszler at Oregon State University. Chapter IV describes a series of six Ga/In compounds, as well as two Al/In compounds. Included in this chapter is an analysis of the heat-induced decomposition properties of the Ga/In clusters. Understanding such thermal decomposition is particularly relevant for the use of these compounds as precursor materials, as an annealing step is used to condense the films. Chapter V addresses the potential for post-synthetic modification of the compounds through metal and ligand exchange reactions, an area that also addresses the issue of solution stability of the structures

  9. Synthesis and characterization of zeolites prepared from industrial fly ash.

    PubMed

    Franus, Wojciech; Wdowin, Magdalena; Franus, Małgorzata

    2014-09-01

    In this paper, we present the possibility of using fly ash to produce synthetic zeolites. The synthesis class F fly ash from the Stalowa Wola SA heat and power plant was subjected to 24 h hydrothermal reaction with sodium hydroxide. Depending on the reaction conditions, three types of synthetic zeolites were formed: Na-X (20 g fly ash, 0.5 dm(3) of 3 mol · dm(-3) NaOH, 75 °C), Na-P1 (20 g fly ash, 0.5 dm(3) of 3 mol · dm(-3) NaOH, 95 °C), and sodalite (20 g fly ash, 0.8 dm(3) of 5 mol · dm(-3) NaOH + 0.4 dm(3) of 3 mol · dm(-3) NaCl, 95 °C). As synthesized materials were characterized to obtain mineral composition (X-ray diffractometry, Scanning electron microscopy-energy dispersive spectrometry), adsorption properties (Brunauer-Emmett-Teller surface area, N2 isotherm adsorption/desorption), and ion exchange capacity. The most effective reaction for zeolite preparation was when sodalite was formed and the quantitative content of zeolite from X-ray diffractometry was 90 wt%, compared with 70 wt% for the Na-X and 75 wt% for the Na-P1. Residues from each synthesis reaction were the following: mullite, quartz, and the remains of amorphous aluminosilicate glass. The best zeolitic material as characterized by highest specific surface area was Na-X at almost 166 m(2) · g(-1), while for the Na-P1 and sodalite it was 71 and 33 m(2) · g(-1), respectively. The ion exchange capacity decreased in the following order: Na-X at 1.8 meq · g(-1), Na-P1 at 0.72 meq · g(-1), and sodalite at 0.56 meq · g(-1). The resulting zeolites are competitive for commercially available materials and are used as ion exchangers in industrial wastewater and soil decontamination. PMID:24838802

  10. Porous Polyelectrolyte Hydrogels With Enhanced Swelling Properties Prepared Via Thermal Reverse Casting Technique

    NASA Astrophysics Data System (ADS)

    Salerno, Aurelio; Netti, Paolo A.

    2010-06-01

    In this work we investigated the preparation and characterization of porous polyelectrolyte hydrogels via thermal reverse casting technique. Polyacrylamide hydrogels were synthesized by free-radical crosslinking polymerization into the space of an agarose gel which, after the setting of the chemical gel, was removed to allow the formation of an interconnected porosity pathway. Two different monomer/agarose solution ratios were selected for the reverse casting process and, the resulting hydrogels characterized in terms of morphological, micro-structural and thermal properties, as well as swelling capability in solutions at different ionic strength. The results of this study demonstrated that proposed technique allowed the design of porous polyacrylamide hydrogels with well controlled pore structures. Furthermore, if compared to non porous polyacrylamide hydrogel, the as obtained hydrogels were characterized by enhanced swelling properties and that, these properties were fine tuned by the appropriate selection of the templating agent concentration.

  11. Linking the foreign body response and protein adsorption to PEG-based hydrogels using proteomics

    PubMed Central

    Swartzlander, Mark D.; Barnes, Christopher A.; Blakney, Anna K.; Kaar, Joel L.; Kyriakides, Themis R.; Bryant, Stephanie J.

    2015-01-01

    Poly(ethylene glycol) (PEG) hydrogels with their highly tunable properties are promising implantable materials, but as with all non-biological materials, they elicit a foreign body response (FBR). Recent studies, however, have shown that incorporating the oligopeptide RGD into PEG hydrogels reduces the FBR. To better understand the mechanisms involved and the role of RGD in mediating the FBR, PEG, PEG-RGD and PEG-RDG hydrogels were investigated. After a 28-day subcutaneous implantation in mice, a thinner and less dense fibrous capsule formed around PEG-RGD hydrogels, while PEG and PEG-RDG hydrogels exhibited stronger, but similar FBRs. Protein adsorption to the hydrogels, which is considered the first step in the FBR, was also characterized. In vitro experiments confirmed that serum proteins adsorbed to PEG-based hydrogels and were necessary to promote macrophage adhesion to PEG and PEG-RDG, but not PEG-RGD hydrogels. Proteins adsorbed to the hydrogels in vivo were identified using liquid chromatography-tandem mass spectrometry. The majority (245) of the total proteins (≥300) that were identified was present on all hydrogels with many proteins being associated with wounding and acute inflammation. These findings suggest that the FBR to PEG hydrogels may be mediated by the presence of inflammatory-related proteins adsorbed to the surface, but that macrophages appear to sense the underlying chemistry, which for RGD improves the FBR. PMID:25522962

  12. Synthesis and characterization of advanced nanomaterials for energy applications

    NASA Astrophysics Data System (ADS)

    Xie, Ming

    Energy is essential for life. It is thus important to continue understanding how to reduce energy consumption, and increase energy generation. The use of nanoscale materials (nanomaterials) are expected to reduce resources and energy needed in fabricating electrical and electronic devices and help in reducing energy consumption. For example, boron nitride nanotubes (BNNTs) which have uniform band structures, are expected to find application in nanoscale electronic and optoelectronic devices. These devices will have smaller dimension, cost fewer resources and less energy to fabricate, and consume less energy due to minimum electron scattering in their ideally defect-free tubular structures. On the other hand, nanomaterials are also expected to improve the performance of thermoelectric devices that can convert heat into energy. In this thesis, we first investigated low-temperature synthesis of BNNTs (Chapter 1). Effects of substrate temperatures, bias voltages, and catalysts are discussed and a selective-phase growth model is proposed. During the course of this investigation, we discovered Si nanotubes (SiNTs) by catalytic plasma treatment (Chapter 2). The detailed growth parameters and characterizations are presented and a modified growth model is discussed. In addition, electronic properties are measured by AFM. Since Si has exceptional thermoelectric properties, the newly discovered SiNTs are prospects for related applications. We have thus evaluated the potential conversion efficiency and production cost of various nanostructured thermoelectric materials (Chapter 3 and 4). Based on state-of-the-art dish-stirling systems, we evaluate the feasibility of replacing stirling engines by thermoelectric modules. Finally, we have decided to investigate the properties of boron-nanocarbon ensembles (Chapter 5 and 6) as prospective thermoelectric materials. Detailed characterizations includes SEM, HRTEM, Raman, XRD are presented. Seebeck coefficient and electrical

  13. Synthesis and characterization of thermoresponsive copolymers for drug delivery.

    PubMed

    Aerry, Swati; De, Arnab; Kumar, Ajeet; Saxena, Amit; Majumdar, D K; Mozumdar, Subho

    2013-07-01

    We report the synthesis and characterization of two nontoxic, thermogelling drug delivery systems which are liquid at room temperatures but become a gel at physiological temperature (37°C) potentially leading to release of a drug molecule. We selected temperature as the stimulus for drug release as it is physiologically invariant. A free radical polymerization of N-isopropylacrylamide (NIPAM) and N-vinylpyrrolidone (VP) was carried out under nitrogen atmosphere in double-distilled water at two different temperatures (30°C and 70°C), and the copolymers obtained were characterized by various analytical techniques. The molar ratios of the two monomers were altered with increasing NIPAM content and their cloud point temperature or least critical solution temperature (LCST) was determined. The copolymer at 9:1 ratio of NIPAM to VP resulted in the formation of nanoparticle-based gel (NG1) at 30°C; however, at 70°C, a microgel (MG1) was formed. The LCST of the nanogel and microgel was 33.5-34°C and 36.5-37°C, respectively. Thus, both the copolymers are water soluble at room temperature, but distinct phases appear at physiological temperatures. We hypothesized that these copolymers on entrapment with a drug could be used for topical application to the skin or eye for controlled drug delivery applications. Toxicological studies revealed that the copolymers are nontoxic in HeLa cells. Finally, our experiments show that a model drug [bovine serum albumin (BSA)] is released at 37°C with zero-order kinetics and confirmed using multiple well-known mathematical models. PMID:23255175

  14. Synthesis and characterization of porous Mo-W oxide nanostructures.

    PubMed

    Paraguay-Delgado, F; Verde, Y; Cizniega, E; Lumbreras, J A; Alonso-Nuñez, G

    2008-12-01

    The present study reports the synthesis method, microstructure characterization, and thermal stability of nanostructured porous mixed oxide (MoO3-WO3) at 550 and 900 degrees C of annealing. The material was synthesized using a hydrothermal method. The precursor was prepared by aqueous solution using ammonium heptamolibdate and ammonium metatungstate, with an atomic ratio of Mo/W = 1. The pH was adjusted to 5, and then the solution was transferred to a teflon-lined stainless steel autoclave and heated at 200 degrees C for 48 h. The resultant material was washed using deionized water. The specific surface area, morphology, composition, and microstructure before and after annealing were studied by N2 physisorption, scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and X-Ray diffraction (XRD). The initial synthesized materials showed low crystallinity and high specific surface area around (141 m2/g). After thermal annealing the material showed higher crystallinity and diminished its specific surface area drastically. PMID:19205219

  15. Synthesis and characterization of MoS2 nanosheets.

    PubMed

    Deokar, G; Vignaud, D; Arenal, R; Louette, P; Colomer, J-F

    2016-02-19

    Here, we report on the synthesis of MoS2 nanosheets using a simple two-step additive-free growth technique. The as-synthesized nanosheets were characterized to determine their structure and composition, as well as their optical properties. The MoS2 nanosheets were analyzed by scanning electron microscopy, transmission electron microscopy (TEM), including high-resolution scanning TEM imaging and energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL). The as-produced MoS2 nanosheets are vertically aligned with curved edges and are densely populated. The TEM measurements confirmed that the nanosheets have the 2H-MoS2 crystal structure in agreement with the Raman results. The XPS results revealed the presence of high purity MoS2. Moreover, a prominent PL similar to mechanically exfoliated few and mono-layer MoS2 was observed for the as-grown nanosheets. For the thin (≤50 nm) nanosheets, the PL feature was observed at the same energy as that for a direct band-gap monolayer MoS2 (1.83 eV). Thus, the as-produced high-quality, large-area, MoS2 nanosheets could be potentially useful for various optoelectronic and catalysis applications. PMID:26789493

  16. Synthesis and characterization of MoS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Deokar, G.; Vignaud, D.; Arenal, R.; Louette, P.; Colomer, J.-F.

    2016-02-01

    Here, we report on the synthesis of MoS2 nanosheets using a simple two-step additive-free growth technique. The as-synthesized nanosheets were characterized to determine their structure and composition, as well as their optical properties. The MoS2 nanosheets were analyzed by scanning electron microscopy, transmission electron microscopy (TEM), including high-resolution scanning TEM imaging and energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL). The as-produced MoS2 nanosheets are vertically aligned with curved edges and are densely populated. The TEM measurements confirmed that the nanosheets have the 2H-MoS2 crystal structure in agreement with the Raman results. The XPS results revealed the presence of high purity MoS2. Moreover, a prominent PL similar to mechanically exfoliated few and mono-layer MoS2 was observed for the as-grown nanosheets. For the thin (≤50 nm) nanosheets, the PL feature was observed at the same energy as that for a direct band-gap monolayer MoS2 (1.83 eV). Thus, the as-produced high-quality, large-area, MoS2 nanosheets could be potentially useful for various optoelectronic and catalysis applications.

  17. Synthesis, characterization, biological evaluation and molecular docking of steroidal spirothiazolidinones

    NASA Astrophysics Data System (ADS)

    Shamsuzzaman; Abdul Baqi, Khan A. A.; Ali, Abad; Asif, Mohd; Mashrai, Ashraf; Khanam, Hena; Sherwani, Asif; Yaseen, Zahid; Owais, Mohammad

    2015-04-01

    The present work describes a convenient synthesis of steroidal spirothiazolidinone derivatives (3, 10-12) in a two-step process. All the newly synthesized compounds have been characterized by means of elemental analyses, IR, 1H NMR, 13C NMR and MS. Lipinski's 'Rule of Five' analysis and biological score predicted higher intrinsic quality of the synthesized compounds and revealed that these compounds have good passive oral absorption. The DNA binding studies of the synthesized compounds with CT-DNA were carried out by UV-vis and fluorescence spectroscopy. The molecular docking study suggested electrostatic interaction between synthesized compounds and nucleotide base pairs. The antitumor activity was tested in vitro against human leukemia cancer cell (Jurkat) and blood peripheral mononuclear normal cell (PBMCs) lines by MTT method. In addition, apoptosis and nonenzymatic degradation of DNA have been investigated. The acetylcholinesterase (AChE) inhibitor activities of the derivatives were also evaluated using Ellman's method. The present study has shown that steroidal spirothiazolidinone derivatives (3, 10-12) can be used as template to design more potent and selective cytotoxic and AChE inhibition agents through modification and derivatization.

  18. Synthesis, characterization, applications, and challenges of iron oxide nanoparticles

    PubMed Central

    Ali, Attarad; Zafar, Hira; Zia, Muhammad; ul Haq, Ihsan; Phull, Abdul Rehman; Ali, Joham Sarfraz; Hussain, Altaf

    2016-01-01

    Recently, iron oxide nanoparticles (NPs) have attracted much consideration due to their unique properties, such as superparamagnetism, surface-to-volume ratio, greater surface area, and easy separation methodology. Various physical, chemical, and biological methods have been adopted to synthesize magnetic NPs with suitable surface chemistry. This review summarizes the methods for the preparation of iron oxide NPs, size and morphology control, and magnetic properties with recent bioengineering, commercial, and industrial applications. Iron oxides exhibit great potential in the fields of life sciences such as biomedicine, agriculture, and environment. Nontoxic conduct and biocompatible applications of magnetic NPs can be enriched further by special surface coating with organic or inorganic molecules, including surfactants, drugs, proteins, starches, enzymes, antibodies, nucleotides, nonionic detergents, and polyelectrolytes. Magnetic NPs can also be directed to an organ, tissue, or tumor using an external magnetic field for hyperthermic treatment of patients. Keeping in mind the current interest in iron NPs, this review is designed to report recent information from synthesis to characterization, and applications of iron NPs. PMID:27578966

  19. Zinc impregnated cellulose nanocomposites: Synthesis, characterization and applications

    NASA Astrophysics Data System (ADS)

    Ali, Attarad; Ambreen, Sidra; Maqbool, Qaisar; Naz, Sania; Shams, Muhammad Fahad; Ahmad, Madiha; Phull, Abdul Rehman; Zia, Muhammad

    2016-11-01

    Nanocomposite materials have broad applicability due to synergistic effect of combined components. In present investigation, cellulose isolated from citrus peel waste is used as a supporting material; impregnation of zinc oxide nanoparticles via co-precipitation method. The characterization of nano composite is carried out through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and Thermo-gravimetric analysis (TGA) resulting less than 10 μm cellulose fiber and approx. 50 nm ZnO NPs. Zinc oxide impregnated cellulose (ZnO-Cel) exhibited significant bacterial devastation property when compared to ZnO NPs or Cellulose via disc diffusion and colony forming unit methods. In addition, the ZnO-Cel exhibited significant total antioxidant, and minor DPPH free radical scavenging and total reducing power activities. The nano composite also showed time dependent increase in photocatalytic by effectively degrading methylene blue dye up to 69.5% under sunlight irradiation within 90 min. The results suggest effective utilization of cellulose obtained from citrus waste and synthesis of pharmacologically important nano-composites that can be exploited in wound dressing; defence against microbial attack and healing due to antioxidative property, furthermore can also be used for waste water treatment.

  20. Graphene Oxide: Synthesis, Characterization, Electronic Structure, and Applications

    NASA Astrophysics Data System (ADS)

    Stewart, Derek A.; Mkhoyan, K. Andre

    While graphite oxide was first identified in 1855 [1, 2], the recent discovery of stable graphene sheets has led to renewed interest in the chemical structure and potential applications of graphene oxide sheets. These structures have several physical properties that could aid in the large scale development of a graphene electronics industry. Depending on the degree of oxidization, graphene oxide layers can be either semiconducting or insulating and provide an important complement to metallic graphene layers. In addition, the electronic and optical properties of these films can be controlled by the selective removal or addition of oxygen. For example, selective oxidationof graphene sheets could lead to electronic circuit fabrication on the scale of a single atomic layer. Graphene oxide is also dispersible in water and other solvents and this provides a facile route for graphene deposition on a wide range of substrates for macroelectronics applications. Although graphite oxide has been known for roughly 150 years, key questions remain in regards to its chemical structure, electronic properties, and fabrication. Answering these issues has taken on special urgency with the development of graphene electronics. In this chapter, we will provide an overview of the field with special focus on synthesis, characterization, and first principles analysis of bonding and electronic structures. Finally, we will also address some of the most promising applications for graphene oxide in electronics and other industries.

  1. Fluorescent nanosensors for intracellular measurements: synthesis, characterization, calibration, and measurement

    PubMed Central

    Desai, Arpan S.; Chauhan, Veeren M.; Johnston, Angus P. R.; Esler, Tim; Aylott, Jonathan W.

    2013-01-01

    Measurement of intracellular acidification is important for understanding fundamental biological pathways as well as developing effective therapeutic strategies. Fluorescent pH nanosensors are an enabling technology for real-time monitoring of intracellular acidification. The physicochemical characteristics of nanosensors can be engineered to target specific cellular compartments and respond to external stimuli. Therefore, nanosensors represent a versatile approach for probing biological pathways inside cells. The fundamental components of nanosensors comprise a pH-sensitive fluorophore (signal transducer) and a pH-insensitive reference fluorophore (internal standard) immobilized in an inert non-toxic matrix. The inert matrix prevents interference of cellular components with the sensing elements as well as minimizing potentially harmful effects of some fluorophores on cell function. Fluorescent nanosensors are synthesized using standard laboratory equipment and are detectable by non-invasive widely accessible imaging techniques. The outcomes of studies employing this technology are dependent on reliable methodology for performing measurements. In particular, special consideration must be given to conditions for sensor calibration, uptake conditions and parameters for image analysis. We describe procedures for: (1) synthesis and characterization of polyacrylamide and silica based nanosensors, (2) nanosensor calibration and (3) performing measurements using fluorescence microscopy. PMID:24474936

  2. Synthesis and Characterization of Crystalline Silicon Carbide Nanoribbons

    PubMed Central

    2010-01-01

    In this paper, a simple method to synthesize silicon carbide (SiC) nanoribbons is presented. Silicon powder and carbon black powder placed in a horizontal tube furnace were exposed to temperatures ranging from 1,250 to 1,500°C for 5–12 h in an argon atmosphere at atmospheric pressure. The resulting SiC nanoribbons were tens to hundreds of microns in length, a few microns in width and tens of nanometers in thickness. The nanoribbons were characterized with electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, and were found to be hexagonal wurtzite–type SiC (2H-SiC) with a growth direction of . The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated. A vapor–solid reaction dominated nanoribbon growth mechanism was discussed. PMID:20676202

  3. Synthesis and Characterization of Crystalline Silicon Carbide Nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Huan; Ding, Weiqiang; He, Kai; Li, Ming

    2010-08-01

    In this paper, a simple method to synthesize silicon carbide (SiC) nanoribbons is presented. Silicon powder and carbon black powder placed in a horizontal tube furnace were exposed to temperatures ranging from 1,250 to 1,500°C for 5-12 h in an argon atmosphere at atmospheric pressure. The resulting SiC nanoribbons were tens to hundreds of microns in length, a few microns in width and tens of nanometers in thickness. The nanoribbons were characterized with electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, and were found to be hexagonal wurtzite-type SiC (2H-SiC) with a growth direction of [10bar{1}0] . The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated. A vapor-solid reaction dominated nanoribbon growth mechanism was discussed.

  4. Synthesis, physicochemical, structural and rheological characterizations of carboxymethyl xanthan derivatives.

    PubMed

    Yahoum, Madiha M; Moulai-Mostefa, Nadji; Le Cerf, Didier

    2016-12-10

    The aim of this work was to synthesize a carboxymethylated xanthan (CMXG) via an etherification reaction between different ratios (2, 4, and 6) of xanthan gum (XG) and monochloroacetic acid (MCAA) using the Williamson synthesis method. The synthetized products were characterized in terms of their physico-chemical and rheological properties. Both FTIR and proton nuclear magnetic resonance (H(1) NMR) analyses confirmed the grafting of carboxymethyl groups on xanthan hydroxyl groups. The obtained results demonstrated that the degree of substitution was proportional to the chloroacetic acid and xanthan gum ratios. The obtained carboxymethyl derivatives presented greater hydrophilicity and lower molecular weights with increasing degrees of substitution than native xanthan gum. The rheological study revealed that the viscosity of the CMXG derivatives decreased with the degree of substitution and with the conservation of the shear-thinning and weak gel behaviours. The flow curves suggested the existence of two different populations of particles consisting of CMXG particles with a smaller average size and a second population formed by the residual fractions of native XG particles. It was also found that the elastic modulus of XG was largely higher than that of the CMXG derivatives and decreased with increasing DS. For the CMXG derivatives, two regions of viscoelastic behaviour were observed, which were separated by a crossover point corresponding to the critical frequency and relaxation time, i.e., the time required for stress relaxation. PMID:27577918

  5. Synthesis and characterization of magnetic nanoparticles embedded in polyacrylonitrile nanofibers

    NASA Astrophysics Data System (ADS)

    Munteanu, Daniel; Ion, Rodica-Mariana; Cocina, George-Costel

    2010-11-01

    Nanomedicine is defined as the monitoring, repair, construction, and control of human biological systems at the molecular level using engineered nanodevices and nanostructures. Polyacrylonitrile (PAN) solution containing the iron oxide precursor iron (III) was electrospun and thermally treated to produce electrically conducting, magnetic carbon nanofiber mats with hierarchical pore structures. This paper discusses the synthesis of magnetite (Fe3O4) nanoparticles with mean crystallite size of 10 nm with polyacrylonitrile (PAN) as the protecting agent, creating nanofiber. The morphology and material properties of the resulting multifunctional nanofiber including the surface area were examined using various characterization techniques. Optical microscopy images show that uniform fibers were produced with a fiber diameter of ~600 nm, and this uniform fiber morphology is maintained after graphitization with a fiber diameter of ~330 nm. X-ray diffraction (XRD) studies reveal the size of Fe3O4 crystals. A combination of XRD and electron microscopy experiments reveals the formation of pores with graphitic nanoparticles in the walls as well as the formation of magnetite nanoparticles distributed throughout the fibers.

  6. Synthesis, NMR characterization, and a simple application of lithium borotritide

    SciTech Connect

    Than, Chit; Morimoto, Hiromi; Andres, H.

    1996-12-13

    LiBH{sub 4} is a powerful and selective reagent for regiospecific reduction reactions. A simple synthesis of LiB{sup 3}H{sub 4} at near theoretical specific radioactivity is reported. The authors have treated Li{sup 3}H synthesized from tritium gas ({sup 3}H{sub 2}, {approximately}98%) with BBr{sub 3} to produce LiB{sup 3}H{sub 4} (specific activity = 4120 GBq/mmol = 110 Ci/mmol. The maximum theoretical specific activity of LiB{sup 3}H{sub 4} is 4252 GBq/mmol = 115.04 Ci/mmol; 1 matom of {sup 3}H = 1063 GBq = 28.76 Ci.) The tritium labeling performance of the reagent was tested by an exemplary reduction of 2-naphthaldehyde to 2-naphthalenemethanol. LiB{sup 3}H{sub 4} and the reduction products were characterized by a combination of {sup 1}H, {sup 3}H, and {sup 11}B NMR techniques, as appropriate. 35 refs., 1 fig.

  7. N-Methylmelamines: Synthesis, Characterization, and Physical Properties.

    PubMed

    List, Manuela; Puchinger, Helmut; Gabriel, Herbert; Monkowius, Uwe; Schwarzinger, Clemens

    2016-05-20

    N-Methylmelamines have recently gained importance as valuable compounds for manufacturing modified melamine formaldehyde resins and other polymer building blocks. A great advantage of these polymers is the reduction of the carcinogenic formaldehyde. Selecting the polymerization processes (e.g., substance polymerization, polymerization in solution) and controlling the polymerization reaction and properties of these novel materials requires knowledge of the properties of the individual melamine derivatives used as new building blocks. All possible permutations of N-methylmelamines were prepared, and reaction progress was monitored by GC/MS. 2,4,6-Tris(dimethylamino)-1,3,5-triazine was prepared to complete the series; this is, however, also a possible byproduct in various synthesis routes. The reaction conditions were optimized to obtain high yields of each derivative with the highest possible purity. The substances were characterized by NMR and IR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. In addition, physical properties, such as solubility, melting points, and pKb values, were determined. The number of amino-, methylamino-, and dimethylamino groups has a significant effect on these properties. In summary, we found that by increasing the number of amino- and methylamino groups, solubility and pKb increase. With increasing number of amino groups, the compounds tend to form hydrogen bonds, and thus, the melting point shifts to higher temperature ranges where they start to decompose. PMID:27100712

  8. Synthesis and characterization of reduced tungsten sulfide cluster complexes

    SciTech Connect

    Zhang, Xiang.

    1991-06-27

    Reduction of tungsten(IV) chloride with metals was studied in order to find a high-yield and convenient preparation of {alpha}-tungsten (II) chloride. The reduction of tungsten(IV) chloride with iron metal proved to be the most convenient and reliable synthesis, with a good yield of 60%. The reactions between {alpha}-tungsten(II) chloride and sodium hydrosulfide were investigated. Complete substitution of sulfide for chloride in W{sub 6}Cl{sub 8}{sup 4+} was achieved in the presence of sodium n-butoxide in pyridine solution. Single crystals were grown at elevated temperature (200{degrees}C) in pyridine, and the structure of W{sub 6}S{sub 8}(py){sub 6} was determined by single crystal x-ray techniques. The triethylphosphine (PEt{sub 3}) and tetrahydrothiophene (THT) complexes of W{sub 6}S{sub 8} were established by ligand displacement of pyridine in W{sub 6}S{sub 8}(py){sub 6}. Structures for both W{sub 6}S{sub 8}(PEt{sub 3}){sub 6}. 1.44CH{sub 2}Cl{sub 2} and W{sub 6}S{sub 8}(THT){sub 6} were determined by single crystal x-ray diffraction. These molecular complexes of the W{sub 6}S{sub 8} cluster were also characterized by infrared spectroscopy. 86 refs., 19 figs., 22 tabs.

  9. A new class of pegylated plasmonic liposomes: synthesis and characterization.

    PubMed

    Stiufiuc, Rares; Iacovita, Cristian; Stiufiuc, Gabriela; Florea, Adrian; Achim, Marcela; Lucaciu, Constantin M

    2015-01-01

    The multifunctional nanoobjects that can be controlled, manipulated and triggered using external stimuli represent very promising candidates for nanoscale therapeutic and diagnostic applications. In this study we report the successful synthesis and characterization of a new class of very stable multifunctional nanoobjects, containing cationic liposomes decorated with PEGylated gold nanoparticles (PEGAuNPs). The multifunctional hybrid nanoobjects (mHyNp) were prepared by taking advantage of the electrostatic interactions between small unilamelar cationic liposomes and negatively charged gold nanoparticles. The mHyNps have been investigated by UV-VIS absorption spectroscopy, Dynamic Light Scattering (DLS), Zeta Potential Measurements and Transmission Electron Microscopy (TEM). The TEM images clearly revealed the attachment of individual gold nanoparticles onto the spherical outer surface of the cationic liposomes which was also confirmed by DLS and UV-VIS data. Furthermore, the plasmonic properties of the hybrid complexes have been evaluated by using the Surface Enhanced Raman Spectroscopy (SERS) technique. It is shown that PEG mediated interaction between the liposomes and the gold nanoparticles enabled the recording of the SER spectra of the liposomes in aqueous environment, thus demonstrating the plasmonic properties of the hybrids. PMID:25310578

  10. Synthesis and characterization of covalently bound benzocaine graphite oxide derivative

    NASA Astrophysics Data System (ADS)

    Kabbani, Ahmad; Kabbani, Mohamad; Safadi, Khadija

    2015-09-01

    Graphite oxide (GO) derived materials include chemically functionalize or reduced graphene oxide (exfoliated from GO) sheets, assembled paper-like forms , and graphene-based composites GO consists of intact graphitic regions interspersed with sp3-hybridized carbons containing hydroxyl and epoxide functional groups on the top and bottom surfaces of each sheet and sp2-hybridized carbons containing carboxyl and carbonyl groups mostly at the sheet edges. Hence, GO is hydrophilic and readily disperses in water to form stable colloidal suspensions Due to the attached oxygen functional groups, GO was used to prepare different derivatives which result in some physical and chemical properties that are dramatically different from their bulk counterparts .The present work discusses the covalent cross linking of graphite oxide to benzocaine or ethyl ester of para-aminobenzoic acid,structure I,used in many over-the-counter ointment drug.Synthesis is done via diazotization of the amino group.The product is characterized via IR,Raman, X-ray photoelectron spectroscopy as well as electron microscopy.

  11. Synthesis and Characterization of Mixed Metal Oxide Nanocomposite Energetic Materials

    SciTech Connect

    Gash, A; Pantoya, M; Jr., J S; Zhao, L; Shea, K; Simpson, R; Clapsaddle, B

    2003-11-18

    In the field of composite energetic materials, properties such as ingredient distribution, particle size, and morphology, affect both sensitivity and performance. Since the reaction kinetics of composite energetic materials are typically controlled by the mass transport rates between reactants, one would anticipate new and potentially exceptional performance from energetic nanocomposites. We have developed a new method of making nanostructured energetic materials, specifically explosives, propellants, and pyrotechnics, using sol-gel chemistry. A novel sol-gel approach has proven successful in preparing metal oxide/silicon oxide nanocomposites in which the metal oxide is the major component. Two of the metal oxides are tungsten trioxide and iron(III) oxide, both of which are of interest in the field of energetic materials. Furthermore, due to the large availability of organically functionalized silanes, the silicon oxide phase can be used as a unique way of introducing organic additives into the bulk metal oxide materials. As a result, the desired organic functionality is well dispersed throughout the composite material on the nanoscale. By introducing a fuel metal into the metal oxide/silicon oxide matrix, energetic materials based on thermite reactions can be fabricated. The resulting nanoscale distribution of all the ingredients displays energetic properties not seen in its microscale counterparts due to the expected increase of mass transport rates between the reactants. The synthesis and characterization of these metal oxide/silicon oxide nanocomposites and their performance as energetic materials will be discussed.

  12. Synthesis and spectral characterization of environmentally responsive fluorescent deoxycytidine analogs

    PubMed Central

    Elmehriki, Adam AH; Suchý, Mojmír; Chicas, Kirby J; Wojciechowski, Filip; Hudson, Robert HE

    2014-01-01

    Herein, we describe the synthesis and spectroscopic properties of five novel pyrrolodeoxycytidine analogs, and the related 5-(1-pyrenylethynyl)-2’-deoxycytidine analog; as well as fluorescence characterization of 5-(p-methoxyphenylethynyl)-2’-deoxyuridine. Within this series of compounds, rigidification of the structure from 6-phenylpyrrolodeoxycytidine to 5,6-benzopyrroldeoxycytidine made remarkable improvement of the fluorescence quantum yield (Φ ~1, EtOH) and substantially increased the Stokes shift. Exchange of the phenyl group of 6-phenylpyrrolodeoxycytidine for other heterocycles (benzofuryl or indolyl) produced an increase in the extinction coefficient at the excitation wavelength while preserving high quantum yields. The steady-state fluorescence response to the environment was determined by sensitivity of Stokes shift to solvent polarity. The effect of solvent polarity on fluorescence emission intensity was concurrently examined and showed that 5,6-benzopyrrolodeoxycytidine is highly sensitive to the presence of water. On the other hand, the previously synthesized 5-(p-methoxyphenylethynyl)-2’-deoxyuridine was found to be sensitive to solvent viscosity indicating molecular rotor behavior. PMID:25483932

  13. Synthesis and characterization of Ti-Ta-Nb-Mn foams.

    PubMed

    Aguilar, C; Guerra, C; Lascano, S; Guzman, D; Rojas, P A; Thirumurugan, M; Bejar, L; Medina, A

    2016-01-01

    The unprecedented increase in human life expectancy have produced profound changes in the prevailing patterns of disease, like the observed increased in degenerative disc diseases, which cause degradation of the bones. Ti-Nb-Ta alloys are promising materials to replace the damaged bone due to their excellent mechanical and corrosion resistance properties. In general metallic foams are widely used for medical application due to their lower elastic moduli compare to bulk materials. In this work we studied the synthesis of 34Nb-29Ta-xMn (x: 2, 4 and 6 wt.% Mn) alloy foams (50% v/v) using ammonium hydrogen carbonate as a space holder. Alloys were produced through mechanical alloying in a planetary mill for 50h. Green compacts were obtained by applying 430 MPa pressure. To remove the space holder from the matrix the green compacts were heated to 180 °C for 1.5h and after sintered at 1300 °C for 3h. Foams were characterized by x-ray diffraction, scanning, transmission electron microscopy and optical microscopy. The elastic modulus of the foam was measured as ~30 GPa, and the values are almost equal to the values predicted using various theoretical models. PMID:26478329

  14. Synthesis, characterization, applications, and challenges of iron oxide nanoparticles.

    PubMed

    Ali, Attarad; Zafar, Hira; Zia, Muhammad; Ul Haq, Ihsan; Phull, Abdul Rehman; Ali, Joham Sarfraz; Hussain, Altaf

    2016-01-01

    Recently, iron oxide nanoparticles (NPs) have attracted much consideration due to their unique properties, such as superparamagnetism, surface-to-volume ratio, greater surface area, and easy separation methodology. Various physical, chemical, and biological methods have been adopted to synthesize magnetic NPs with suitable surface chemistry. This review summarizes the methods for the preparation of iron oxide NPs, size and morphology control, and magnetic properties with recent bioengineering, commercial, and industrial applications. Iron oxides exhibit great potential in the fields of life sciences such as biomedicine, agriculture, and environment. Nontoxic conduct and biocompatible applications of magnetic NPs can be enriched further by special surface coating with organic or inorganic molecules, including surfactants, drugs, proteins, starches, enzymes, antibodies, nucleotides, nonionic detergents, and polyelectrolytes. Magnetic NPs can also be directed to an organ, tissue, or tumor using an external magnetic field for hyperthermic treatment of patients. Keeping in mind the current interest in iron NPs, this review is designed to report recent information from synthesis to characterization, and applications of iron NPs. PMID:27578966

  15. Synthesis, characterization and biological activities of curcumin nanospheres.

    PubMed

    Arunraj, T R; Sanoj Rejinold, N; Mangalathillam, Sabitha; Saroj, Soumya; Biswas, Raja; Jayakumar, R

    2014-02-01

    Curcumin is one of the most versatile compounds obtained from Curcuma longa. The major obstacle in the therapeutic use of curcumin is its aqueous solubility. To enhance its aqueous solubility and biological activities, we prepared curcumin nanospheres (CNSs) by wet milling-solvent evaporation technique without any surfactants. In this study, we have focused on the synthesis, characterization and biological effects of CNSs. DLS and SEM analyses showed 50-80 nm spherical shaped CNSs with a zeta potential of -31.65 mV. FTIR revealed that there were no structural changes to CNSs. Antibacterial and antifungal studies proved that CNSs were much more effective than curcumin against Escherichia coil, Staphylococcus aureus and Candida albicans. Antioxidant activity of CNSs showed promising result for therapeutic applications. The in vitro anti-inflammatory studies proved that CNSs possessed enhanced anti-inflammatory effect against protein denaturation. Cytotoxicity and uptake of CNSs showed more toxicity on cancer cells (T47D, MG63, A375) sparing normal HDF and IEC cell lines. Skin permeation studies showed CNSs retained at different layers of pig skin. These results give clear evidence for their use against microbial and fungal skin infections as well as cancer treatment. PMID:24738332

  16. Synthesis and characterization of furazan energetics ADAAF and DOATF

    SciTech Connect

    Veauthier, Jaqueline M; Chavez, David E; Tappan, Bryce C; Parrish, Damon

    2009-01-01

    The synthesis and structural characterization of bis[4-aminofurazanyl-3-azoxy]azofurazan (ADAAF) and 3,4:7,8:11,12:15,16-tetrafurazano-1,2,5,6,9,10,13,14-octaazacyclohexadeca-1,3,5,7,9,11,13,15-octaene-1,10-dioxide (DOATF) are described. Explosive sensitivity properties of both materials were determined. The heat of formation of ADAAF was measured to be 300 kcal/mol while the detonation velocity and pressure of ADAAF were measured to be 7.88 km/s and 299 kbar, respectively at 94% theoretical maximum density. We also investigated the burning rate characteristics of ADAAF. We have reported two new synthetic procedures and the first X-ray crystal structures for the azoxyfurazan compounds ADAAF (4) and DOATF (5). These new energetic materials were found to be significantly more sensitive to mechanical initiation than DAAF (3) and the heat of formation of 4 was found to be nearly three times that of 3. The detonation velocity and pressure for 4 are comparable to 2 while its burning rate characteristics are similar to HMX. Further studies to elucidate sensitivity behavior are ongoing.

  17. Encapsulated Nanoparticle Synthesis and Characterization for Improved Storage Fluids: Preprint

    SciTech Connect

    Glatzmaier, G. C.; Pradhan, S.; Kang, J.; Curtis, C.; Blake, D.

    2010-10-01

    Nanoparticles are typically composed of 50--500 atoms and exhibit properties that are significantly different from the properties of larger, macroscale particles that have the same composition. The addition of these particles to traditional fluids may improve the fluids' thermophysical properties. As an example, the addition of a nanoparticle or set of nanoparticles to a storage fluid may double its heat capacity. This increase in heat capacity would allow a sensible thermal energy storage system to store the same amount of thermal energy in half the amount of storage fluid. The benefit is lower costs for the storage fluid and the storage tanks, resulting in lower-cost electricity. The goal of this long-term research is to create a new class of fluids that enable concentrating solar power plants to operate with greater efficiency and lower electricity costs. Initial research on this topic developed molecular dynamic models that predicted the energy states and transition temperatures for these particles. Recent research has extended the modeling work, along with initiating the synthesis and characterization of bare metal nanoparticles and metal nanoparticles that are encapsulated with inert silica coatings. These particles possess properties that make them excellent candidates for enhancing the heat capacity of storage fluids.

  18. A novel fluorogenic substrate for ribonucleases. Synthesis and enzymatic characterization.

    PubMed Central

    Zelenko, O; Neumann, U; Brill, W; Pieles, U; Moser, H E; Hofsteenge, J

    1994-01-01

    The synthesis and enzymatic characterization of DUPAAA, a novel fluorogenic substrate for RNases of the pancreatic type is described. It consists of the dinucleotide uridylyl-3',5'-deoxyadenosine to which a fluorophore, o-aminobenzoic acid, and a quencher, 2,4-dinitroaniline, have been attached by means of phosphodiester linkages. Due to intramolecular quenching the intact substrate displayed very little fluorescence. Cleavage of the phosphodiester bond at the 3'-side of the uridylyl residue by RNase caused a 60-fold increase in fluorescence. This allowed the continuous and highly sensitive monitoring of enzyme activity. The substrate was turned over efficiently by RNases of the pancreatic type, but no cleavage was observed with the microbial RNase T1. Compared to the dinucleotide substrate UpA, the specificity constant with RNase A, RNase PL3 and RNase U(s) increased 6-, 18-, and 29-fold, respectively. These differences in increased catalytic efficiency most likely reflect differences in the importance of subsites on the enzyme in the binding of elongated substrates. Studies on the interactions of RNase inhibitor with RNase A using DUPAAA as a reporter substrate showed that it was well suited for monitoring this very tight protein-protein interaction using pre-steady-state kinetic methods. PMID:8052528

  19. Hydrothermal synthesis and characterization of zirconia based catalysts

    NASA Astrophysics Data System (ADS)

    Caillot, T.; Salama, Z.; Chanut, N.; Cadete Santos Aires, F. J.; Bennici, S.; Auroux, A.

    2013-07-01

    In this work, three equimolar mixed oxides ZrO2/CeO2, ZrO2/TiO2, ZrO2/La2O3 and a reference ZrO2 have been synthesized by hydrothermal method. The structural and surface properties of these materials have been fully characterized by X-ray diffraction, transmission electron microscopy, surface area measurement, chemical analysis, XPS, infrared spectroscopy after adsorption of pyridine and adsorption microcalorimetry of NH3 and SO2 probe molecules. All investigated mixed oxides are amphoteric and possess redox centers on their surface. Moreover, hydrothermal synthesis leads to catalysts with higher surface area and with better acid-base properties than classical coprecipitation method. Both Lewis and Brønsted acid sites are present on the surface of the mixed oxides. Compared to the other samples, the ZrO2/TiO2 material appears to be the best candidate for further application in acid-base catalysis.

  20. Synthesis, Characterization and Reactivity of a Hexane-Soluble Silver Salt

    ERIC Educational Resources Information Center

    Stockland, Robert A. Jr.; Wilson, Brian D.; Goodman, Caton C.; Giese, Barret J.; Shrimp, Frederick L., II

    2007-01-01

    The connectivity of a hexane-soluble silver salt is established by using NMR spectroscopy to describe the synthesis, characterization and reactivity of the salt. The results found hexane-soluble silver to be an effective transfer agent.

  1. Hydrogel Actuation by Electric Field Driven Effects

    NASA Astrophysics Data System (ADS)

    Morales, Daniel Humphrey

    Hydrogels are networks of crosslinked, hydrophilic polymers capable of absorbing and releasing large amounts of water while maintaining their structural integrity. Polyelectrolyte hydrogels are a subset of hydrogels that contain ionizable moieties, which render the network sensitive to the pH and the ionic strength of the media and provide mobile counterions, which impart conductivity. These networks are part of a class of "smart" material systems that can sense and adjust their shape in response to the external environment. Hence, the ability to program and modulate hydrogel shape change has great potential for novel biomaterial and soft robotics applications. We utilized electric field driven effects to manipulate the interaction of ions within polyelectrolyte hydrogels in order to induce controlled deformation and patterning. Additionally, electric fields can be used to promote the interactions of separate gel networks, as modular components, and particle assemblies within gel networks to develop new types of soft composite systems. First, we present and analyze a walking gel actuator comprised of cationic and anionic gel legs attached by electric field-promoted polyion complexation. We characterize the electro-osmotic response of the hydrogels as a function of charge density and external salt concentration. The gel walkers achieve unidirectional motion on flat elastomer substrates and exemplify a simple way to move and manipulate soft matter devices in aqueous solutions. An 'ionoprinting' technique is presented with the capability to topographically structure and actuate hydrated gels in two and three dimensions by locally patterning ions induced by electric fields. The bound charges change the local mechanical properties of the gel to induce relief patterns and evoke localized stress, causing rapid folding in air. The ionically patterned hydrogels exhibit programmable temporal and spatial shape transitions which can be tuned by the duration and/or strength of

  2. PVD synthesis and high-throughput property characterization of NiFeCr alloy libraries

    SciTech Connect

    Rar, A.; Frafjord, J. J.; Fowlkes, Jason D.; Specht, E. D.; Rack, P. D.; Santella, M. L.; Bei, H.; George, E. P.; Pharr, G. M.

    2004-12-16

    Three methods of alloy library synthesis, thick-layer deposition followed by interdiffusion, composition-spread codeposition and electron-beam melting of thick deposited layers, have been applied to Ni-Fe-Cr ternary and Ni-Cr binary alloys. Structural XRD mapping and mechanical characterization by means of nanoindentation have been used to characterize the properties of the libraries. The library synthesis methods are compared from the point of view of the structural and mechanical information they can provide.

  3. Synthesis and Characterization of Organic Impurities in Bortezomib Anhydride Produced by a Convergent Technology

    PubMed Central

    Ivanov, Andrey S.; Shishkov, Sergey V.; Zhalnina, Anna A.

    2012-01-01

    A profile of impurities in bortezomib anhydride, produced by a recently developed convergent technology, has been characterized. HPLC-MS analysis of the drug essence revealed three impurities: an epimer of bortezomib, resulting from partial racemization of l-phenylalanine’s stereogenic center during the chemical synthesis, and two epimeric products of oxidative degradation of bortezomib, in which boron is replaced by the OH group. The impurities were obtained by chemical synthesis and characterized by physical methods. PMID:22396904

  4. Synthesis, characterization, and reactivity of pentamethylcyclopentadienyl complexes of divalent cobalt and nickel

    SciTech Connect

    Smith, M.E.

    1993-10-01

    The thesis is divided into the following 4 chapters: synthesis, characterization, and reactivity of trinuclear pentamethylcyclopentadienyl cobalt and nickel clusters with triply-bridging methylidyne groups; chemical and physical properties of pentamethylcyclopentadienyl acetylacetonate complexes of Co(II) and Ni(II); synthesis, characterization, and reactivity of pentamethylcyclopentadienyl halide complexes of Co and Ni; and crystallographic studies of distortions in metallocenes with C{sub 5}-symmetrical cyclopentadienyl rings.

  5. Injectable, degradable, electroactive nanocomposite hydrogels containing conductive polymer nanoparticles for biomedical applications

    PubMed Central

    Wang, Qinmei; Wang, Qiong; Teng, Wei

    2016-01-01

    Injectable electroactive hydrogels (eGels) are promising in regenerative medicine and drug delivery, however, it is still a challenge to obtain such hydrogels simultaneously possessing other properties including uniform structure, degradability, robustness, and biocompatibility. An emerging strategy to endow hydrogels with desirable properties is to incorporate functional nanoparticles in their network. Herein, we report the synthesis and characterization of an injectable hydrogel based on oxidized alginate (OA) crosslinking gelatin reinforced by electroactive tetraaniline-graft-OA nanoparticles (nEOAs), where nEOAs are expected to impart electroactivity besides reinforcement without significantly degrading the other properties of hydrogels. Assays of transmission electron microscopy, 1H nuclear magnetic resonance, and dynamic light scattering reveal that EOA can spontaneously and quickly self-assemble into robust nanoparticles in water, and this nanoparticle structure can be kept at pH 3~9. Measurement of the gel time by rheometer and the stir bar method confirms the formation of the eGels, and their gel time is dependent on the weight content of nEOAs. As expected, adding nEOAs to hydrogels does not cause the phase separation (scanning electron microscopy observation), but it improves mechanical strength up to ~8 kPa and conductivity up to ~10−6 S/cm in our studied range. Incubating eGels in phosphate-buffered saline leads to their further swelling with an increase of water content <6% and gradual degradation. When growing mesenchymal stem cells on eGels with nEOA content ≤14%, the growth curves and morphology of cells were found to be similar to that on tissue culture plastic; when implanting these eGels on a chick chorioallantoic membrane for 1 week, mild inflammation response appeared without any other structural changes, indicating their good in vitro and in vivo biocompatibility. With injectability, uniformity, degradability, electroactivity, relative

  6. Injectable, degradable, electroactive nanocomposite hydrogels containing conductive polymer nanoparticles for biomedical applications.

    PubMed

    Wang, Qinmei; Wang, Qiong; Teng, Wei

    2016-01-01

    Injectable electroactive hydrogels (eGels) are promising in regenerative medicine and drug delivery, however, it is still a challenge to obtain such hydrogels simultaneously possessing other properties including uniform structure, degradability, robustness, and biocompatibility. An emerging strategy to endow hydrogels with desirable properties is to incorporate functional nanoparticles in their network. Herein, we report the synthesis and characterization of an injectable hydrogel based on oxidized alginate (OA) crosslinking gelatin reinforced by electroactive tetraaniline-graft-OA nanoparticles (nEOAs), where nEOAs are expected to impart electroactivity besides reinforcement without significantly degrading the other properties of hydrogels. Assays of transmission electron microscopy, (1)H nuclear magnetic resonance, and dynamic light scattering reveal that EOA can spontaneously and quickly self-assemble into robust nanoparticles in water, and this nanoparticle structure can be kept at pH 3~9. Measurement of the gel time by rheometer and the stir bar method confirms the formation of the eGels, and their gel time is dependent on the weight content of nEOAs. As expected, adding nEOAs to hydrogels does not cause the phase separation (scanning electron microscopy observation), but it improves mechanical strength up to ~8 kPa and conductivity up to ~10(-6) S/cm in our studied range. Incubating eGels in phosphate-buffered saline leads to their further swelling with an increase of water content <6% and gradual degradation. When growing mesenchymal stem cells on eGels with nEOA content ≤14%, the growth curves and morphology of cells were found to be similar to that on tissue culture plastic; when implanting these eGels on a chick chorioallantoic membrane for 1 week, mild inflammation response appeared without any other structural changes, indicating their good in vitro and in vivo biocompatibility. With injectability, uniformity, degradability, electroactivity, relative

  7. Synthesis and characterization of low-dimensional molecular magnetic materials

    NASA Astrophysics Data System (ADS)

    Liu, Chen

    This dissertation presents experimental results from the synthesis and structural, magnetic characterization of representative low-dimensional molecule-based magnetic materials. Most of the materials reported in this dissertation, both coordination polymers and cuprate, are obtained as the result of synthesizing and characterizing spin ladder systems; except the material studied in Chapter 2, ferricenyl(III)trisferrocenyl(II)borate, which is not related to the spin ladder project. The interest in spin ladder systems is due to the discovery of high-temperature superconductivity in doped cuprates possessing ladder-like structures, and it is hoped that investigation of the magnetic behavior of ladder-like structures will help us understand the mechanism of high-temperature superconductivity. Chapter 1 reviews fundamental knowledge of molecular magnetism, general synthetic strategies for low-dimensional coordination polymers, and a brief introduction to the current status of research on spin ladder systems. Chapter 2 presents a modified synthetic procedure of a previously known monomeric complex, ferricenyl(III)trisferrocenyl(II)borate, 1. Its magnetic properties were characterized and previous results have been disproved. Chapter 3 investigates the magnetism of [CuCl2(CH3CN)] 2, 2, a cuprate whose structure consists of isolated noninterpenetrating ladders formed by the stacking of Cu(II) dimers. This material presents an unexpected ferromagnetic interaction both within the dimeric units and between the dimers, and this behavior has been rationalized based on the effect of its terminal nonbridging ligands. In Chapter 4, the synthesis and magnetism of two ladder-like coordination polymers, [Co(NO3)2(4,4'-bipyridine) 1.5(MeCN)]n, 3, and Ni2(2,6-pyridinedicarboxylic acid)2(H2O)4(pyrazine), 4, are reported. Compound 3 possesses a covalent one-dimensional ladder structure in which Co(II) ions are bridged through bipyridine molecules. Compared to the materials discussed in

  8. Synthesis and Characterization of Polymer-Templated Magnetic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Tamakloe, Beatrice

    This research reports on the investigation into the synthesis and stabilization of iron oxide nanoparticles for theranostic applications using amine-epoxide polymers. Although theranostic agents such as magnetic nanoparticles have been designed and developed for a few decades, there is still more work that needs to be done with the type of materials that can be used to stabilize or functionalize these particles if they are to be used for applications such as drug delivery, imaging and hyperthermia. For in-vivo applications, it is crucial that organic coatings enclose the nanoparticles in order to prevent aggregation and facilitate efficient removal from the body as well as protect the body from toxic material. The objective of this thesis is to design polymer coated magnetite nanoparticles with polymers that are biocompatible and can stabilize the iron oxide nanoparticle to help create mono-dispersed particles in solution. It is desirable to also have these nanoparticles possess high magnetic susceptibility in response to an applied magnetic field. The co-precipitation method was selected because it is probably the simplest and most efficient chemical pathway to obtain magnetic nanoparticles. In literature, cationic polymers such as Polyethylenimine (PEI), which is the industry standard, have been used to stabilize IONPs because they can be used in magnetofections to deliver DNA or RNA. PEI however is known to interact very strongly with proteins and is cytotoxic, so as mentioned previously the Iron Oxide nanoparticles (IONPs) synthesized in this study were stabilized with amine-epoxide polymers because of the limitations of PEI. Four different amine-epoxide polymers which have good water solubility, biodegradability and less toxic than PEI were synthesized and used in the synthesis and stabilization of the magnetic nanoparticles and compared to PEI templated IONPs. These polymer-templated magnetic nanoparticles were also characterized by size, surface charge, Iron

  9. Synthesis and characterization of two dimensional transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Gao, Jian

    Two-dimensional transition metal dichalcogenides (TMDs) are an emerging class of atomically thin semiconductors that show potential in next-generation electronics, optoelectronics, and energy storage batteries. The successful synthesis and doping of TMDs is the key to their applications. I have synthesized monolayer MoS2, WS2, and multilayer ReS2 flakes by CVD, and studied an unprecedented one-pot synthesis for transition-metal substitution doping in large-area, synthetic monolayer TMDs. Electron microscopy, optical and electronic transport characterization a