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Sample records for based crosslinked deoxyribonucleic

  1. Performance of an electro-optic waveguide modulator fabricated using a deoxyribonucleic-acid-based biopolymer

    NASA Astrophysics Data System (ADS)

    Heckman, Emily M.; Grote, James G.; Hopkins, F. Kenneth; Yaney, Perry P.

    2006-10-01

    An electro-optic (EO) planar waveguide modulator using a deoxyribonucleic acid (DNA)-based biopolymer for both the waveguide core and cladding layers has been fabricated and its performance evaluated. A cross-linked DNA-surfactant biopolymer was used for the top and bottom cladding layers and the core layer was a cross-linked DNA-surfactant biopolymer with 3wt% Disperse Red 1. The EO coefficient r33 was induced through contact poling. The fabricated device was found to exhibit EO modulating behavior. Using an estimated value of r33=0.5pm/V, a sine-squared fit to the modulating data was obtained with Vπ=263V±10%.

  2. Deoxyribonucleic acid base compositions of dermatophytes.

    PubMed

    Davison, F D; Mackenzie, D W; Owen, R J

    1980-06-01

    DNA was extracted and purified from 55 dermatophyte isolates representing 34 species of Trichophyton, Microsporum and Epidermophyton. The base compositions of the chromosomal DNA were determined by CsCl density gradient centrifugation and were found to be in the narrow range of 48.7 to 50.3 mol % G + C. A satellite DNA component assumed to be of mitochondrial origin was present in most strains, with a G + C content ranging from 14.7 to 30.8 mol % G + C. Heterogeneity in microscopic and colonial characteristics was not reflected in differences in the mean G + C content of the chromosomal DNAs. Strains varied in the G + C contents of satelite DNA, but these did not correlate with traditional species concepts.

  3. A novel chaotic based image encryption using a hybrid model of deoxyribonucleic acid and cellular automata

    NASA Astrophysics Data System (ADS)

    Enayatifar, Rasul; Sadaei, Hossein Javedani; Abdullah, Abdul Hanan; Lee, Malrey; Isnin, Ismail Fauzi

    2015-08-01

    Currently, there are many studies have conducted on developing security of the digital image in order to protect such data while they are sending on the internet. This work aims to propose a new approach based on a hybrid model of the Tinkerbell chaotic map, deoxyribonucleic acid (DNA) and cellular automata (CA). DNA rules, DNA sequence XOR operator and CA rules are used simultaneously to encrypt the plain-image pixels. To determine rule number in DNA sequence and also CA, a 2-dimension Tinkerbell chaotic map is employed. Experimental results and computer simulations, both confirm that the proposed scheme not only demonstrates outstanding encryption, but also resists various typical attacks.

  4. Agreement Between Deoxyribonucleic Acid Base Composition and Taxometric Classification of Gram-Positive Cocci1

    PubMed Central

    Silvestri, L. G.; Hill, L. R.

    1965-01-01

    Silvestri, L. G. (Università Statale, Milan, Italy), and L. R. Hill. Agreement between deoxyribonucleic acid base composition and taxometric classification of gram-positive cocci. J. Bacteriol. 90:136–140. 1965.—It had been previously proposed, from taxometric analyses, that gram-positive, catalase-positive cocci be divided into two subgroups. Thirteen strains, representative of both subgroups, were examined for deoxyribonucleic acid (DNA) base composition, determined from melting temperatures. Per cent GC (guanine + cytosine/total bases) values fell into two groups: 30.8 to 36.5% GC and 69 to 75% GC. Strains with low per cent GC values belonged to the Staphylococcus aureus–S. saprophyticus–S. lactis taxometric subgroups, and those with high per cent GC values belonged to the S. roseus–S. afermentans subgroup. The hypothetical nature of any classification is emphasized, and, in the present work, the hypothesis derived from taxometric analyses of division into two subgroups is confirmed by the study of DNA base ratios. The two subgroups correspond, respectively, to the genera Staphylococcus and Micrococcus. PMID:16562008

  5. BASE COMPOSITION OF THE DEOXYRIBONUCLEIC ACID OF SULFATE-REDUCING BACTERIA.

    PubMed

    SIGAL, N; SENEZ, J C; LEGALL, J; SEBALD, M

    1963-06-01

    Sigal, Nicole (Laboratoire de Chimie Bactérienne du CNRS, Marseille, France), Jacques C. Senez, Jean Le Gall, and Madeleine Sebald. Base composition of the deoxyribonucleic acid of sulfate-reducing bacteria. J. Bacteriol. 85:1315-1318. 1963-The deoxyribonucleic acid constitution of several strains of sulfate-reducing bacteria has been analytically determined. The results of these studies show that this group of microorganisms includes at least four subgroups characterized by significantly different values of the adenine plus thymine to guanine plus cytosine ratio. The nonsporulated forms with polar flagellation, containing both cytochrome c(3) and desulfoviridin, are divided into two subgroups. One includes the fresh-water, nonhalophilic strains with base ratio from 0.54 to 0.59, and the other includes the halophilic or halotolerant strains with base ratio from 0.74 to 0.77. The sporulated, peritrichous strains without cytochrome and desulfoviridin ("nigrificans" and "orientis") are distinct from the above two types and differ from each other, having base ratios of 1.20 and 1.43, respectively.

  6. Optoelectronic studies on heterocyclic bases of deoxyribonucleic acid for DNA photonics.

    PubMed

    El-Diasty, Fouad; Abdel-Wahab, Fathy

    2015-10-01

    The optoelectronics study of large molecules, particularly π-stacking molecules, such as DNA is really an extremely difficult task. We perform first electronic structure calculations on the heterocyclic bases of 2'-deoxyribonucleic acid based on Lorentz-Fresnel dispersion theory. In the UV-VIS range of spectrum, many of the optoelectronic parameters for DNA four bases namely adenine, guanine, cytosine and thymine are calculated and discussed. The results demonstrate that adenine has the highest hyperpolarizability, whereas thymine has the lowest hyperpolarizability. Cytosine has the lower average oscillator energy and the higher lattice energy. Thymine infers the most stable nucleic base with the lower phonon energy. Thymine also has the highest average oscillator energy and the lower lattice energy. Moreover, the four nucleic acid bases have large band gap energies less than 5 eV with a semiconducting behavior. Guanine shows the smallest band gap and the highest Fermi level energy, whereas adenine elucidates the highest band gap energy.

  7. Deoxyribonucleic Acid Base Sequence Homologies of Some Budding and Prosthecate Bacteria

    PubMed Central

    Moore, Richard L.; Hirsch, Peter

    1972-01-01

    The genetic relatedness of a number of budding and prosthecate bacteria was determined by deoxyribonucleic acid (DNA) homology experiments of the direct binding type. Strains of Hyphomicrobium sp. isolated from aquatic habitats were found to have relatedness values ranging from 9 to 70% with strain “EA-617,” a subculture of the Hyphomicrobium isolated by Mevius from river water. Strains obtained from soil enrichments had lower values with EA-617, ranging from 3 to 5%. Very little or no homology was detected between the amino acid-utilizing strain Hyphomicrobium neptunium and other Hyphomicrobium strains, although significant homology was observed with the two Hyphomonas strains examined. No homology could be detected between prosthecate bacteria of the genera Rhodomicrobium, Prosthecomicrobium, Ancalomicrobium, or Caulobacter, and Hyphomicrobium strain EA-617 or H. neptunium LE-670. The grouping of Hyphomicrobium strains by their relatedness values agrees well with a grouping according to the base composition of their DNA species. It is concluded that bacteria possessing cellular extensions represent a widely diverse group of organisms. PMID:5018022

  8. Heat shock protein 70 stimulation of the deoxyribonucleic acid base excision repair enzyme polymerase β

    PubMed Central

    Mendez, Frances; Kozin, Elliott; Bases, Robert

    2003-01-01

    Base excision repair (BER) of damaged deoxyribonucleic acid (DNA) is a multistep process during which potentially lethal abasic sites temporarily exist. Repair of these lesions is greatly stimulated by heat shock protein 70 (Hsp70), which enhances strand incision and removal of the abasic sites by human apurinic-apyrimidinic endonuclease (HAP1). The resulting single-strand gaps must then be filled in. Here, we show that Hsp70 and its 48- and 43-kDa N-terminal domains greatly stimulated filling in the single-strand gaps by DNA polymerase β, a novel finding that extends the role of Hsps in DNA repair. Incorporation of deoxyguanosine monophosphate (dGMP) to fill in single-strand gaps in DNA phagemid pBKS by DNA polymerase β was stimulated by Hsp70. Truncated proteins derived from the C-terminus of Hsp70 as well as unrelated proteins were less effective, but proteins derived from the N-terminus of Hsp70 remained efficient stimulators of DNA polymerase β repair of DNA single-strand gaps. In agreement with these results, repair of a gap in a 30-bp oligonucleotide by polymerase β also was strongly stimulated by Hsp70 although not by a truncated protein from the C-terminus of Hsp70. Sealing of the repaired site in the oligonucleotide by human DNA ligase 1 was not specifically stimulated by Hsp-related proteins. Results presented here now implicate and extend the role of Hsp70 as a partner in the enzymatic repair of damaged DNA. The participation of Hsp70 jointly with base excision enzymes improves repair efficiency by mechanisms that are not yet understood. PMID:14627201

  9. BASE COMPOSITION OF DEOXYRIBONUCLEIC ACID OF SULFATE-REDUCING BACTERIA DEDUCED FROM BUOYANT DENSITY MEASUREMENTS IN CESIUM CHLORIDE

    PubMed Central

    Saunders, Grady F.; Campbell, L. Leon; Postgate, John R.

    1964-01-01

    Saunders, Grady F. (University of Illinois, Urbana), L. Leon Campbell, and John R. Postgate. Base composition of deoxyribonucleic acid of sulfate-reducing bacteria deduced from buoyant density measurements in cesium chloride. J. Bacteriol. 87:1073–1078. 1964.—The base composition of the deoxyribonucleic acid (DNA) of sulfate-reducing bacteria was calculated from buoyant density measurements in CsCl. The sporulating sulfate-reducing bacteria fell into two groups: Desulfovibrio orientis with a DNA base composition of 42% guanine plus cytosine (G + C), and Clostridium nigrificans with a DNA base composition of 45% G + C. The mesophilic relative of C. nigrificans had a DNA base composition of 46% G + C. Thirty strains of nonsporulating sulfate-reducing bacteria called D. desulfuricans were studied. They fell into three groups as judged by DNA base composition: group I (11 strains), 60 to 62% G + C; group II (13 strains), 54 to 56% G + C; and group III (6 strains), 46 to 47% G + C. These data underline the need for a taxonomic revision of this group of microorganisms. PMID:5874533

  10. High mobility organic field-effect transistor based on water-soluble deoxyribonucleic acid via spray coating

    SciTech Connect

    Shi, Wei; Han, Shijiao; Huang, Wei; Yu, Junsheng

    2015-01-26

    High mobility organic field-effect transistors (OFETs) by inserting water-soluble deoxyribonucleic acid (DNA) buffer layer between electrodes and pentacene film through spray coating process were fabricated. Compared with the OFETs incorporated with DNA in the conventional organic solvents of ethanol and methanol: water mixture, the water-soluble DNA based OFET exhibited an over four folds enhancement of field-effect mobility from 0.035 to 0.153 cm{sup 2}/Vs. By characterizing the surface morphology and the crystalline structure of pentacene active layer through atomic force microscope and X-ray diffraction, it was found that the adoption of water solvent in DNA solution, which played a key role in enhancing the field-effect mobility, was ascribed to both the elimination of the irreversible organic solvent-induced bulk-like phase transition of pentacene film and the diminution of a majority of charge trapping at interfaces in OFETs.

  11. Deoxyribonucleic Acid Base Composition and Biochemical Properties of Certain Coagulase-Negative Enterotoxigenic Cocci

    PubMed Central

    Lotter, Leonard P.; Genigeorgis, Constantin A.

    1975-01-01

    Eight coagulase-negative, enterotoxigenic strains of cocci and one weakly coagulase-positive strain isolated from a number of different sources, including cases of food poisoning incidents, were evaluated for their relationship to Staphylococcus aureus on the basis of deoxyribonucleic acid (DNA) buoyant density and physiological studies. One strain of cocci produced enterotoxins A and C, two strains produced types B and C, four strains produced only type C, and one strain only type D. The enterotoxin produced by one strain of cocci was serologically untypable. None of the test organisms produced detectable amounts of enterotoxin in broth cultures. The test strains of cocci exhibited the following profile: all produced catalase; all grew anaerobically and fermented glucose; five were sensitive to lysostaphin; the percentage of guanine plus cytosine content of their DNA varied from 32.7 to 37.6; five produced acid from mannitol both aerobically and anaerobically; two formed δ-hemolysin; five produced phosphatase and acetoin; and all produced heat-stable nuclease. None of the organisms exhibited typical characteristics of S. aureus, S. epidermidis, or S. saprophyticus. On the basis of the present data and data reported elsewhere, these organisms should be considered as variants or mutants of S. aureus. PMID:803812

  12. Deoxyribonucleic acid base composition and biochemical properties of certain coagulase-negative enterotoxigenic cocci.

    PubMed

    Lotter, L P; Genigeorgis, C A

    1975-02-01

    Eight coagulase-negative, enterotoxigenic strains of cocci and one weakly coagulase-positive strain isolated from a number of different sources, including cases of food poisoning incidents, were evaluated for their relationship to Staphylococcus aureus on the basis of deoxyribonucleic acid (DNA) buoyant density and physiological studies. One strain of cocci produced enterotoxins A and C, two strains produced types B and C, four strains produced only type C, and one strain only type D. The enterotoxin produced by one strain of cocci was serologically untypable. None of the test organisms produced detectable amounts of enterotoxin in broth cultures. The test strains of cocci exhibited the following profile: all produced catalase; all grew anaerobically and fermented glucse; five were sensitive to lysostaphin; the percentage of guanine plus cytosine content of their DNA varied from 32.7 to 37.6; five produced acid from mannitol both aerobically and anaerobically; two formed delta-hemolysin; five produced phosphatase and acetoin; and all produced heat-stable nuclease. None of the organisms exhibited typical characteristics of S. aureus, S. epidermidis, or S. saprophyticus. On the basis of the present data and data reported elsewhere, these organisms should be considered as variants or mutants of S. aureus.

  13. Biodegradable, hydrophobic coatings based on crosslinked polycaprolactone

    SciTech Connect

    Koenig, M.F.

    1993-12-31

    Crosslinked poly(caprolactone) (PCL) has been explored as a hydrophobic and biodegradable coating for hydrophilic substrates. Crosslinking of PCL is known to retard its degradation rate, but does not affect its biodegradability. The cross-linking efficiencies of several organic peroxides have been determined for PCL. This has been accomplished by calculating the crosslink density (M{sub c} from dynamic mechanical data) for a given molar concentration of organic peroxide. Various thicknesses of crosslinked PCL have been coated on several different hydrophilic substrates, including paper, MaterBi (regsign), and PCL/starch composites. The hydrophobicity of the coating has been measured by following the weight gain of the coated samples upon exposure to water and a high relative humidity for various lengths of time. Results show that a coating as thin as 10 {mu}m reduces water absorption of paper by a factor of five, and thicker coatings (0.25 mm) by more than two orders of magnitude.

  14. Attitude to Human Papillomavirus Deoxyribonucleic Acid-Based Cervical Cancer Screening in Antenatal Care in Nigeria: A Qualitative Study.

    PubMed

    Filade, Temitope E; Dareng, Eileen O; Olawande, Toyosi; Fagbohun, Tolani A; Adebayo, Amos O; Adebamowo, Clement A

    2017-01-01

    Human papillomavirus (HPV) deoxyribonucleic acid (DNA)-based testing is increasingly used for cervical cancer screening in developed countries, but the best approach to utilizing it in low- and middle-income countries (LMIC) is unclear. Incorporation of HPV DNA-based testing into routine antenatal care (ANC) is a potential yet poorly explored strategy for cervical cancer screening in LMIC. We explored the attitude of health care workers and pregnant women to the incorporation of HPV DNA-based tests into routine ANC in Nigeria. We conducted nine focus group discussions with 82 pregnant women and 13 in-depth interviews with obstetricians and midwives at four health care facilities in Abuja, Nigeria. We used qualitative content analysis to analyze the data and the theory of planned behavior as a theoretical framework to examine the responses. Pregnant women expressed a favorable attitude toward HPV DNA testing for cervical cancer screening as part of routine ANC. Acceptability of this approach was motivated by the expected benefits from early detection and treatment of cervical cancer. The factors most commonly cited as likely to influence acceptability and uptake of HPV DNA-based tests are recommendations by their care providers and mandating testing as part of ANC services. Discussants mentioned lack of awareness and affordability as factors that may inhibit uptake of HPV DNA-based cervical cancer screening. Midwives expressed concerns about the safety of sampling procedure in pregnancy, while obstetricians fully support the integration of HPV DNA-based testing into routine ANC. Our results show that incorporating HPV DN-based cervical cancer screening into routine ANC is acceptable to pregnant women and health care providers. Making the test affordable and educating health care workers on its efficacy and safety if performed during ANC will enhance their willingness to recommend it and increase its uptake.

  15. Crosslinked anion exchange membranes with primary diamine-based crosslinkers for vanadium redox flow battery application

    NASA Astrophysics Data System (ADS)

    Cha, Min Suc; Jeong, Hwan Yeop; Shin, Hee Young; Hong, Soo Hyun; Kim, Tae-Ho; Oh, Seong-Geun; Lee, Jang Yong; Hong, Young Taik

    2017-09-01

    A series of polysulfone-based crosslinked anion exchange membranes (AEMs) with primary diamine-based crosslinkers has been prepared via simple a crosslinking process as low-cost and durable membranes for vanadium redox flow batteries (VRFBs). Chloromethylated polysulfone is used as a precursor polymer for crosslinked AEMs (CAPSU-x) with different degrees of crosslinking. Among the developed AEMs, CAPSU-2.5 shows outstanding dimensional stability and anion (Cl-, SO42-, and OH-) conductivity. Moreover, CAPSU-2.5 exhibits much lower vanadium ion permeability (2.72 × 10-8 cm2 min-1) than Nafion 115 (2.88 × 10-6 cm2 min-1), which results in an excellent coulombic efficiency of 100%. The chemical and operational stabilities of the membranes have been investigated via ex situ soaking tests in 0.1 M VO2+ solution and in situ operation tests for 100 cycles, respectively. The excellent chemical, physical, and electrochemical properties of the CAPSU-2.5 membrane make it suitable for use in VRFBs.

  16. Reversible phospholipid nanogels for deoxyribonucleic acid fragment size determinations up to 1500 base pairs and integrated sample stacking.

    PubMed

    Durney, Brandon C; Bachert, Beth A; Sloane, Hillary S; Lukomski, Slawomir; Landers, James P; Holland, Lisa A

    2015-06-23

    Phospholipid additives are a cost-effective medium to separate deoxyribonucleic acid (DNA) fragments and possess a thermally-responsive viscosity. This provides a mechanism to easily create and replace a highly viscous nanogel in a narrow bore capillary with only a 10°C change in temperature. Preparations composed of dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) self-assemble, forming structures such as nanodisks and wormlike micelles. Factors that influence the morphology of a particular DMPC-DHPC preparation include the concentration of lipid in solution, the temperature, and the ratio of DMPC and DHPC. It has previously been established that an aqueous solution containing 10% phospholipid with a ratio of [DMPC]/[DHPC]=2.5 separates DNA fragments with nearly single base resolution for DNA fragments up to 500 base pairs in length, but beyond this size the resolution decreases dramatically. A new DMPC-DHPC medium is developed to effectively separate and size DNA fragments up to 1500 base pairs by decreasing the total lipid concentration to 2.5%. A 2.5% phospholipid nanogel generates a resolution of 1% of the DNA fragment size up to 1500 base pairs. This increase in the upper size limit is accomplished using commercially available phospholipids at an even lower material cost than is achieved with the 10% preparation. The separation additive is used to evaluate size markers ranging between 200 and 1500 base pairs in order to distinguish invasive strains of Streptococcus pyogenes and Aspergillus species by harnessing differences in gene sequences of collagen-like proteins in these organisms. For the first time, a reversible stacking gel is integrated in a capillary sieving separation by utilizing the thermally-responsive viscosity of these self-assembled phospholipid preparations. A discontinuous matrix is created that is composed of a cartridge of highly viscous phospholipid assimilated into a separation matrix

  17. Deoxyribonucleic acid base composition and taxonomy of Moniliella and allied genera.

    PubMed

    de Hoog, G S; Guého, E

    1984-01-01

    DNA base compositions of representative (type) strains of Moniliella, Trichosporonoides and Hyalodendron were determined. Within Trichosporonoides over 16% variance was found. Most species separated well, but M. suaveolens showed considerable heterogeneity. The standard 2% G + C differences for species distinction is probably not applicable to these yeasts. The new combination M. pollinis is proposed for M. tomentosa var. pollinis on the basis of slight ecological, morphological and physiological differences, supported by a marked difference in % G + C.

  18. Determination of the base composition of deoxyribonucleic acid by measurement of the adenine-granine ratio.

    PubMed

    Kirk, J T

    1967-11-01

    A method is described for determination of the base composition (as guanine+cytosine or adenine+thymine content) of DNA by accurate measurement of the adenine/guanine ratio. The DNA is hydrolysed with 0.03n-hydrochloric acid for 40min. to release the purines. The hydrolysate is subjected to ion-exchange chromatography on Zeo-Karb 225. Apurinic acids are eluted with 0.03n-hydrochloric acid and then guanine and adenine are eluted separately with 2n-hydrochloric acid. Guanine and adenine are each collected as a single fraction, and the amount of base in each case is determined by measuring the volume and the extinction at suitable wavelengths. For use in the calculations, millimolar extinction coefficients in 2n-hydrochloric acid of 12.09 for adenine at 262mmu, and 10.77 for guanine at 248mmu, were determined with authentic samples of bases. The method gives extremely reproducible results: from 12 determinations with calf thymus DNA the adenine/guanine molar ratio had a standard deviation of 0.011; this corresponds to a standard deviation in guanine+cytosine content of 0.2% guanine+cytosine.

  19. Determination of the base composition of deoxyribonucleic acid by measurement of the adenine/guanine ratio

    PubMed Central

    Kirk, J. T. O.

    1967-01-01

    A method is described for determination of the base composition (as guanine+cytosine or adenine+thymine content) of DNA by accurate measurement of the adenine/guanine ratio. The DNA is hydrolysed with 0·03n-hydrochloric acid for 40min. to release the purines. The hydrolysate is subjected to ion-exchange chromatography on Zeo-Karb 225. Apurinic acids are eluted with 0·03n-hydrochloric acid and then guanine and adenine are eluted separately with 2n-hydrochloric acid. Guanine and adenine are each collected as a single fraction, and the amount of base in each case is determined by measuring the volume and the extinction at suitable wavelengths. For use in the calculations, millimolar extinction coefficients in 2n-hydrochloric acid of 12·09 for adenine at 262mμ, and 10·77 for guanine at 248mμ, were determined with authentic samples of bases. The method gives extremely reproducible results: from 12 determinations with calf thymus DNA the adenine/guanine molar ratio had a standard deviation of 0·011; this corresponds to a standard deviation in guanine+cytosine content of 0·2% guanine+cytosine. PMID:5626094

  20. Transcription of single base oligonucleotides by ribonucleic acid-directed deoxyribonucleic acid polymerase.

    PubMed Central

    Falvey, A K; Weiss, G B; Krueger, L J; Kantor, J A; Anderson, W F

    1976-01-01

    The synthesis of DNA products complementary to artificial templates by the enzyme RNA-directed DNA polymerase isolated from avian myeloblastosis virus has been studied. Of the single base polyribonucleotides, poly (rC), poly(rA), and poly(rI) were active while poly (rG) and poly (rU) were almost inactive. The minimum length showing activity for an oligo (rC) template was 9; the minimum primer length of oligo(dG) was 3 or 4. In order to examine the fidelity of transcription, single base oligoribonucleotides of defined length were studied. Using (rC)13 as template and (dG)8as primer, the oligo (dG) product coelectrophoresed with the template. However, using (rA)-20 as template and (dT)10 as primer, a large (10-16s) product was formed. Similarly, using oligo (rI) (2.5S) as template and (dC)10 as primer, a large (greater than 22s) product was formed. No significant activity was obtained with oligo (rU) templates. RNA-directed DNA polymerase transcribes the various oligonucleotides differently: slippage with oligo (rA) and oligo (rI), faithful transcription with oligo (rC), and poor transcription with oligo (rU). PMID:55999

  1. Base composition, size and sequence similarities of genoma deoxyribonucleic acids from clinical isolates of Pseudomonas putrefaciens.

    PubMed

    Owen, R J; Legors, R M; Lapage, S P

    1978-01-01

    The mean base compositions of DNA from 27 strains of Pseudomonas putrefaciens, P. rubescens and P. piscicida ranged from 43-4 to 53-2 mol% GC with genome sizes from 3.04 X 10(9) to 4.23 X 10(9) daltons. On the basis of in vitro DNA-DNA binding, estimated spectrophotometrically from initial renaturation rates, P. putrefaciens strains were heterogenous in the extent to which they shared similar nucleotide sequences, and were divided into four DNA homology groups. The DNA characteristics of strains in these groups correlated with several biochemical characteristics that facilitated identification of clinical isolates of P. putrefaciens. The two species P. putrefaciens and P. rubescens appear to be synonymous and none of the four groups of P. putrefaciens was related in DNA sequences to P. pisicida. Pseudomonas putrefaciens should theretofore be retained as a single species and characteristics for identifying the various groups within the species are listed.

  2. Graphene-based polyaniline arrays for deoxyribonucleic acid electrochemical sensor: effect of nanostructure on sensitivity.

    PubMed

    Yang, Tao; Meng, Le; Zhao, Jinlong; Wang, Xinxing; Jiao, Kui

    2014-01-01

    DNA detection sensitivity can be improved by carefully controlling the texture of the sensor substrate, which was normally investigated on metal or metal oxide nanostructured platform. Morphology effects on the biofunctionalization of polymer micro/nanoelectrodes have not been investigated in detail. To extend this topic, we used graphene oxide (GNO) as the supporting material to prepare graphene-based polyaniline nanocomposites with different morphologies as a model for comparing their DNA sensing behaviors. Owing to GNO serving as an excellent support or template for nucleation and growth of polyaniline (PANI), PANI nanostructures grown on GNO substrate were successfully obtained. However, if GNO supporting was absent, the obtained PANI nanowires showed a connected network. Furthermore, adjustment of reaction time can be used for dominating the topographies of PANI-GNO nanocomposites, meaning that different reaction times resulted in various formations of PANI-GNO nanocomposites, including small horns (5 and 12 h), vertical arrays (18 h), and nanotips (24 h). The next-step electrochemical data showed that the DNA electrochemical sensors constructed on the different morphologies possessed different ssDNA surface coverage and hybridization efficiency. Compared with other morphologies of PANI-GNO nanocomposite (5, 12, and 24 h), vertical arrays (18 h) exhibited the highest sensitivity (2.08 × 10(-16) M, 2 orders of magnitude lower than others). It is can be concluded that this nanocomposite with higher surface area and more accessible space can provide an optimal balance for DNA immobilization and DNA hybridization detection.

  3. To Cross-Link or Not to Cross-Link? Cross-Linking Associated Foreign Body Response of Collagen-Based Devices

    PubMed Central

    Delgado, Luis M.; Bayon, Yves; Pandit, Abhay

    2015-01-01

    Collagen-based devices, in various physical conformations, are extensively used for tissue engineering and regenerative medicine applications. Given that the natural cross-linking pathway of collagen does not occur in vitro, chemical, physical, and biological cross-linking methods have been assessed over the years to control mechanical stability, degradation rate, and immunogenicity of the device upon implantation. Although in vitro data demonstrate that mechanical properties and degradation rate can be accurately controlled as a function of the cross-linking method utilized, preclinical and clinical data indicate that cross-linking methods employed may have adverse effects on host response, especially when potent cross-linking methods are employed. Experimental data suggest that more suitable cross-linking methods should be developed to achieve a balance between stability and functional remodeling. PMID:25517923

  4. Biocompatible thermoresponsive PEGMA nanoparticles crosslinked with cleavable disulfide-based crosslinker for dual drug release.

    PubMed

    Ulasan, Mehmet; Yavuz, Emine; Bagriacik, Emin Umit; Cengeloglu, Yunus; Yavuz, Mustafa Selman

    2015-01-01

    Smart materials have been attracting much attention because of their stimuli responsive nature. We have synthesized biocompatible thermoresponsive crosslinked poly(ethylene glycol) methyl ether methacrylate (PEGMA)-co-vinyl pyrrolidone nanoparticles (PEGMA NPs) using disulfide-based crosslinker by surfactant-free emulsion polymerization method. Particle characterization studies were carried out by dynamic light scattering, and scanning electron microscopy. Polymerization kinetics, effect of crosslinker and initiator concentrations on both average hydrodynamic diameter and polydispersity index were investigated. Hydrodynamic diameters of thermoresponsive PEGMA NPs were decreased from 210 nm to 90 nm upon heating over the lowest critical solution temperature (LCST). Disulfide crosslinked PEGMA NPs were demonstrated as a dual delivery system. Rhodamine B, a model of small-sized drug molecule, and poly(ethylene glycol) (PEG)-alizarin yellow, a model of large drug molecule, were loaded into PEGMA NPs where LCST of these NPs was tuned to 37°C, the body temperature. The rhodamine B was released from PEGMA NPs upon heating to 39°C. Then, PEG-alizarin content was released by subsequent degradation of nanoparticles using dithiothreitol (DTT), which reduces disulfide bonds to thiols. Furthermore, cytotoxicity studies of PEGMA NPs were carried out in 3T3 cells, which resulted in no toxic effect on the cells.

  5. Crosslinking of polynorbornene based dielectrics for application in microelectronics

    NASA Astrophysics Data System (ADS)

    Chiniwalla, Punit Paresh

    2001-07-01

    structure (polymer over metal lines on a cured polymer base) are investigated for both polynorbornene systems. Films that possess lower levels of crosslinking exhibited significant surface topography distortions. It is proposed that these distortions are the result of extraction of solvent during processing of subsequent layers over metal lines into a crosslinked underlying layer.

  6. Crosslinkable fumed silica-based nanocomposite electrolytes: role of methacrylate monomer in formation of crosslinked silica network

    NASA Astrophysics Data System (ADS)

    Yerian, Jeffrey A.; Khan, Saad A.; Fedkiw, Peter S.

    The electrochemical and rheological properties of composite polymer electrolytes (CPEs) based on fumed silica with tethered crosslinkable groups are reported. These silica nanoparticles are dispersed in electrolytes consisting of poly(ethylene glycol) dimethyl ether (PEGdm)+lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to which various methacrylate monomers, such as methyl (MMA), ethyl (EMA), butyl (BMA), n-hexyl (HMA), and n-dodecyl (DMA) methacrylate, are added. The methacrylate monomer facilitates creation of chemical crosslinks between fumed silica particles and formation of a crosslinked network. In this study, the effects of concentration and alkyl chain length of the monomers on conductivity, dynamic rheology, open-circuit interfacial stability, and cell voltage in lithium-lithium cell cycling are examined. Increasing the length of the monomer alkyl chain enhances both conductivity and elastic modulus of the crosslinked CPE. In contrast, increasing monomer concentration results in higher elastic modulus, but reduced conductivity. Lithium-lithium cell cycling and open-circuit interfacial stability results did not correlate with alkyl chain length. That is, for the lithium-lithium cycling studies, all crosslinked samples exhibit higher half-cycle voltage compared to non-crosslinked samples; however, the open-circuit interfacial stability of CPEs containing BMA and HMA exhibit improved stability compared to the other monomers and the CPE without monomer.

  7. Electroluminescent devices based on cross-linked polymer blends

    NASA Astrophysics Data System (ADS)

    Bozano, Luisa D.; Carter, Kenneth R.; Lee, Victor Y.; Miller, Robert D.; DiPietro, Richard; Scott, J. Campbell

    2003-09-01

    We report the electrical and optical properties of two-component blends of electron and hole transporting materials in single and bilayer structures for organic light emitting diode (OLED) applications. The materials considered were a blue-emitting bipolar transporting polyfluorene, poly(9,9-di-n-hexylfluorene) (DHF), and a hole-transporting material, poly-[4-nhexyltriphenylamine] (HTPA). We compare the steady state OLED performance, transport, and optical properties of devices and describe morphology studies of the polymer films based on cross-linkable (x) blends with the analogous non-cross-linkable blends. The cross-linkable blends exhibit highest efficiency at low concentrations of the hole transporting material. At these concentrations the single layer OLEDs reach efficiencies greater than 0.1%, and are higher than for single layer x-DHF or the binary non-cross-linkable blend by more than an order of magnitude. Bilayer structures with homogeneous x-HTPA as hole transport layer show efficiencies between 0.08% and 0.96%, depending on the blend concentration in the emitting layer and on the top contact. We interpret these results in terms of the relative degree of phase segregation in the cross-linked networks versus the non-cross-linkable blends.

  8. Electrophoresis-Enhanced Detection of Deoxyribonucleic Acids on a Membrane-Based Lateral Flow Strip Using Avian Influenza H5 Genetic Sequence as the Model

    PubMed Central

    Wu, Jui-Chuang; Chen, Chih-Hung; Fu, Ja-Wei; Yang, Huan-Ching

    2014-01-01

    This study reports a simple strategy to detect a deoxyribonucleic acid (DNA) on a membrane-based lateral flow (MBLF) strip without tedious gel preparation, gel electrophoresis, and EtBr-staining processes. The method also enhances the detection signal of the genetic sample. A direct electric field was applied over two ends of the MBLF strips to induce an electrophoresis of DNAs through the strips. The signal enhancement was demonstrated by the detection of the H5 subtype of avian influenza virus (H5 AIV). This approach showed an excellent selectivity of H5 AIV from other two control species, Arabidopsis thaliana and human PSMA5. It also showed an effective signal repeatability and sensitivity over a series of analyte concentrations. Its detection limit could be enhanced, from 40 ng to 0.1 ng by applying 12 V. The nano-gold particles for the color development were labeled on the capture antibody, and UV-VIS and TEM were used to check if the labeling was successful. This detection strategy could be further developed to apply on the detection of drug-allergic genes at clinics or detection of infectious substances at incident sites by a simple manipulation with an aid of a mini-PCR machine and auxiliary kits. PMID:24603637

  9. Highly Sensitive Detection of Deoxyribonucleic Acid Hybridization Using Au-Gated AlInN/GaN High Electron Mobility Transistor-Based Sensors

    NASA Astrophysics Data System (ADS)

    Zhan, Xiang-Mi; Hao, Mei-Lan; Wang, Quan; Li, Wei; Xiao, Hong-Ling; Feng, Chun; Jiang, Li-Juan; Wang, Cui-Mei; Wang, Xiao-Liang; Wang, Zhan-Guo

    2017-03-01

    Gallium nitride- (GaN) based high electron mobility transistors (HEMTs) provide a good platform for biological detection. In this work, both Au-gated AlInN/GaN HEMT and AlGaN/GaN HEMT biosensors are fabricated for the detection of deoxyribonucleic acid (DNA) hybridization. The Au-gated AlInN/GaN HEMT biosensor exhibits higher sensitivity in comparison with the AlGaN/GaN HEMT biosensor. For the former, the drain-source current ( {V}{DS}=0.5 V) shows a clear decrease of 69 μA upon the introduction of 1 μmolL {}-1 (μM) complimentary DNA to the probe DNA at the sensor area, while for the latter it is only 38 μA. This current reduction is a notable indication of the hybridization. The high sensitivity can be attributed to the thinner barrier of the AlInN/GaN heterostructure, which makes the two-dimensional electron gas channel more susceptible to a slight change of the surface charge. Supported by the National Key Research and Development Program of China under Grant Nos 2016YFB0400104 and 2016YFB0400301, the National Natural Sciences Foundation of China under Grant No 61334002, and the National Science and Technology Major Project.

  10. UV written waveguides using crosslinkable PMMA-based copolymers

    NASA Astrophysics Data System (ADS)

    Koo, Jae-Sun; Smith, Peter G. R.; Williams, Richard B.; Riziotis, Christos; Grossel, Martin C.

    2003-09-01

    Crosslinkable copolymers poly(methylmethacrylate/2-methacryloylethylmethacrylate) (P(MMA/MAOEMA)) were developed for waveguide applications. P(MMA/MAOEMA) can crosslink under either UV exposure or heating. The UV-induced refractive index change in unreacted P(MMA/MAOEMA) is found to depend on the fluence. UV exposure of thermally crosslinked P(MMA/MAOEMA) can induce further structure change and thus index change, and therefore, was found to be useful for creating the core layers in optical waveguides. The photosensitivity of the thermally crosslinked polymers is sufficient for the fabrication of low loss (<1 dB/cm) channel waveguides in the thermally crosslinked copolymer system.

  11. Synthesis and Characterization of Gelatin-Based Crosslinkers for the Fabrication of Superabsorbent Hydrogels

    PubMed Central

    Amonpattaratkit, Penphitcha; Khunmanee, Sureerat; Kim, Dong Hyun; Park, Hansoo

    2017-01-01

    In this work, crosslinkers were prepared by conjugating high- and low-molecular-weight gelatin with different mole ratios of itaconic acid (IA) with double bonds. Then, the gelatin-itaconic acid (gelatin-IA) crosslinkers were compared with the gelatin-methacrylate (gelatin-MA) crosslinkers. The molecular weights and structures of gelatin-MA and gelatin-IA were confirmed using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). Additionally, the swelling ratio and biodegradation properties of the hydrogels using IA as starting monomers and gelatin-IA and gelatin-MA as crosslinkers were investigated. Both hydrogels prepared with high and low molecular weights of gelatin-IA showed higher swelling ratios than those prepared with the gelatin-MA. The results also showed that absorbent hydrogels with different biodegradabilities and swelling ratios could be prepared by changing the ratio of the gelatin-based crosslinkers. PMID:28773186

  12. A crosslinker based on a tethered electrophile for mapping kinase-substrate networks.

    PubMed

    Riel-Mehan, Megan M; Shokat, Kevan M

    2014-05-22

    Despite the continuing progress made toward mapping kinase signaling networks, there are still many phosphorylation events for which the responsible kinase has not yet been identified. We are interested in addressing this problem through forming covalent crosslinks between a peptide substrate and the corresponding phosphorylating kinase. Previously we reported a dialdehyde-based kinase-binding probe capable of such a reaction with a peptide containing a cysteine substituted for the phosphorylatable ser/thr/tyr residue. Here, we examine the yield of a previously reported dialdehyde-based probe and report that the dialdehyde-based probes possess a significant limitation in terms of crosslinked kinase-substrate product yield. To address this limitation, we developed a crosslinking scheme based on a kinase activity-based probe, and this crosslinker provides an increase in efficiency and substrate specificity, including in the context of cell lysate.

  13. Fundamental insight into the effect of carbodiimide crosslinking on cellular recognition of collagen-based scaffolds.

    PubMed

    Bax, Daniel V; Davidenko, Natalia; Gullberg, Donald; Hamaia, Samir W; Farndale, Richard W; Best, Serena M; Cameron, Ruth E

    2017-02-01

    Research on the development of collagen constructs is extremely important in the field of tissue engineering. Collagen scaffolds for numerous tissue engineering applications are frequently crosslinked with 1-ethyl-3-(3-dimethylaminopropyl-carbodiimide hydrochloride (EDC) in the presence of N-hydroxy-succinimide (NHS). Despite producing scaffolds with good biocompatibility and low cellular toxicity the influence of EDC/NHS crosslinking on the cell interactive properties of collagen has been overlooked. Here we have extensively studied the interaction of model cell lines with collagen I-based materials after crosslinking with different ratios of EDC in relation to the number of carboxylic acid residues on collagen. Divalent cation-dependent cell adhesion, via integrins α1β1, α2β1, α10β1 and α11β1, were sensitive to EDC crosslinking. With increasing EDC concentration, this was replaced with cation-independent adhesion. These results were replicated using purified recombinant I domains derived from integrin α1 and α2 subunits. Integrin α2β1-mediated cell spreading, apoptosis and proliferation were all heavily influenced by EDC crosslinking of collagen. Data from this rigorous study provides an exciting new insight that EDC/NHS crosslinking is utilising the same carboxylic side chain chemistry that is vital for native-like integrin-mediated cell interactions. Due to the ubiquitous usage of EDC/NHS crosslinked collagen for biomaterials fabrication this data is essential to have a full understanding in order to ensure optimized collagen-based material performance.

  14. Determination of triadimenol based on the quenching effect on resonance light scattering from the triadimenol-deoxyribonucleic acid-hydrochloric acid system.

    PubMed

    Du, Fengpei; Luo, Xiaolin; Jiang, Guibin; Hou, Shicong; Liu, Gang; Ren, Liping; Zhang, Li; Huang, Qin; Jie, Nianqin

    2007-05-01

    Analysis of triadimenol was carried out using deoxyribonucleic acids (DNA) via the resonance light scattering (RLS) technique. After adding triadimenol into aqueous medium of pH 1.72, the RLS of DNA was remarkably quenched. A resonance light scattering peak at 310 nm was found, and the quenched intensity of RLS at this wavelength was proportional to the concentration of triadimenol. The linear range of the calibration curve was approximately 0-3 microg mL-1 with a detection limit (S/N=3) of 0.07 microg mL-1. The triadimenol in samples of water, cucumber and human serum was determined. The results were satisfactory, and the recovery rates were in the range of 96.3-106.0%, 94.8-105.9% and 92.3-100.5%, respectively. The interaction mechanism was also studied.

  15. An Invisible Bend Sensor Based on Porous Crosslinked Polyelectrolyte Film

    SciTech Connect

    Zhang, Q.; Saraf, Laxmikant V.; Smith, James R.; Jha, P.; Hua, Feng

    2009-04-29

    This paper describes the fabrication of a porous cross-linked polyelectrolyte membrane and the characterization of its humidity sensitivity performance. Electrostatic self-assembly, combined with acid treatment, and post-deposition annealing produced the membrane. The fabrication process offers the ability to control the thickness of the membrane, as well as enabling the engineering of the humidity sensitivity properties. A transparent humidity sensor was fabricated by integrating the membrane into a capacitive structure. In order to improve the moisture absorption and diffusion, both the polyelectrolyte layer and the electrode were made porous. The membrane was cross-linked to enhance the durability in high humid environments. Such a polyelectrolyte membrane showed high sensitivity to relative humidity variation over a range of 25-99%. The see-through property of the structure adds extra features and benefits to the sensor.

  16. Crosslinker effects on functional properties of alginate/N-succinylchitosan based hydrogels.

    PubMed

    Straccia, Maria Cristina; Romano, Ida; Oliva, Adriana; Santagata, Gabriella; Laurienzo, Paola

    2014-08-08

    In this paper, physico-chemical, mechanical and antimicrobial properties of hydrogels based on alginate/N-succinylchitosan blends crosslinked by calcium or zinc ions containing cellulose microfibers were investigated and discussed. With respect to plain alginate hydrogels, the addition of N-succinylchitosan significantly improved properties such as swelling degree and stability in saline solution. The water vapour transmission rate confirmed that all the hydrogels were able to assure a moist wound environment. Morphological analysis showed a good embedding of fibres within the zinc crosslinked hydrogels. In addition, zinc-crosslinked hydrogels evidenced antimicrobial activity against two common skin pathogenic bacteria, Staphylococcus aureus and Escherichia coli. Cytotoxicity assays proved that the amount of zinc released is slightly over the toxic level. Overall, the characteristics of the zinc-crosslinked hydrogels showed their potential interest as materials for wound dressing. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Novel chitosan-based films cross-linked by genipin with improved physical properties.

    PubMed

    Jin, J; Song, M; Hourston, D J

    2004-01-01

    Novel cross-linked chitosan-based films were prepared using the solution casting technique. A naturally occurring and nontoxic cross-linking agent, genipin, was used to form the chitosan and chitosan/poly(ethylene oxide) (PEO) blend networks, where two types of PEO were used, one with a molecular weight of 20 000 g/mol (HPEO) and the other of 600 g/mol (LPEO). Genipin is used in traditional Chinese medicine and extracted from gardenia fruit. Importantly, it overcomes the problem of physiological toxicity inherent in the use of some common synthetic chemicals as cross-linking agents. The mechanical properties and the stability in water of cross-linked and un-crosslinked chitosan and chitosan/PEO blend films were investigated. It was shown that, compared to the transparent yellow, un-cross-linked chitosan/PEO blend films, the genipin-cross-linked chitosan-based film, blue in color, was more elastic, was more stable, and had better mechanical properties. Genipin-cross-linking produced chitosan networks that were insoluble in acidic and alkaline solutions but were able to swell in these aqueous media. The swelling characteristics of the films exhibit sensitivity to the environmental pH and temperature. The surface properties of the films were also examined by contact angle measurements using water and mixtures of water/ethanol. The results showed that, with the one exception of cross-linked pure chitosan in 100% water, the cross-linked chitosan and chitosan/PEO blends were more hydrophobic than un-crosslinked ones.

  18. Nonprotein Based Enrichment Method to Analyze Peptide Cross-Linking in Protein Complexes

    PubMed Central

    Yan, Funing; Che, Fa-Yun; Rykunov, Dmitry; Nieves, Edward; Fiser, Andras; Weiss, Louis M.; Angeletti, Ruth Hogue

    2009-01-01

    Cross-linking analysis of protein complexes and structures by tandem mass spectrometry (MS/MS) has advantages in speed, sensitivity, specificity, and the capability of handling complicated protein assemblies. However, detection and accurate assignment of the cross-linked peptides are often challenging due to their low abundance and complicated fragmentation behavior in collision-induced dissociation (CID). To simplify the MS analysis and improve the signal-to-noise ratio of the cross-linked peptides, we developed a novel peptide enrichment strategy that utilizes a cross-linker with a cryptic thiol group and using beads modified with a photocleavable cross-linker. The functional cross-linkers were designed to react with the primary amino groups in proteins. Human serum albumin was used as a model protein to detect intra- and intermolecular cross-linkages. Use of this protein-free selective retrieval method eliminates the contamination that can result from avidin–biotin based retrieval systems and simplifies data analysis. These features may make the method suitable to investigate protein–protein interactions in biological samples. PMID:19642656

  19. Ultra thin hydro-films based on lactose-crosslinked fish gelatin for wound healing applications.

    PubMed

    Etxabide, Alaitz; Vairo, Claudia; Santos-Vizcaino, Edorta; Guerrero, Pedro; Pedraz, Jose Luis; Igartua, Manoli; de la Caba, Koro; Hernandez, Rosa Maria

    2017-09-15

    This study focuses on the development and characterization of an ultra thin hydro-film based on lactose-mediated crosslinking of fish gelatin by Maillard reaction. Lactose results in the only efficient crosslinker able to produce resistant to handling hydro-films when compared to conventional crosslinkers such as glutaraldehyde or genipin (tested at 25 and 37°C in phosphate buffer saline solution (PBS)).The disappearance of the peak related to the N-containing groups (XPS) and the images obtained by SEM and AFM demonstrate the highly ordered nano-scaled structure of lactose-crosslinked gelatin, confirming the crosslinking efficiency. This dressing presents high hydrophilicity and mild occlusivity, as shown by the swelling curve (max swelling at 5min) and by the occlusion factor of 25.17±0.99%, respectively. It demonstrates high stability to hydrolysis or cell-mediated degradation. Moreover, ISO 10993-5:2009 biocompatibility assay results in undetectable cytotoxicity effects. Spreading, adhesion and proliferation assays confirm the excellent adaptability of the cells onto the hydro-film surface without invading the dressing. Finally, the hydro-film enables the controlled delivery of therapeutic factors, such as the epidermal growth factor (EGF). This study demonstrates that lactose-mediated crosslinking is able to produce ultra thin gelatin hydro-films with suitable properties for biomedical applications, such as wound healing. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Antifouling coatings based on covalently cross-linked agarose film via thermal azide-alkyne cycloaddition.

    PubMed

    Xu, Li Qun; Pranantyo, Dicky; Neoh, Koon-Gee; Kang, En-Tang; Teo, Serena Lay-Ming; Fu, Guo Dong

    2016-05-01

    Coatings based on thin films of agarose-poly(ethylene glycol) (Agr-PEG) cross-linked systems are developed as environmentally-friendly and fouling-resistant marine coatings. The Agr-PEG cross-linked systems were prepared via thermal azide-alkyne cycloaddition (AAC) using azido-functionalized Agr (AgrAz) and activated alkynyl-containing poly(2-propiolamidoethyl methacrylate-co-poly(ethylene glycol)methyl ether methacrylate) P(PEMA-co-PEGMEMA) random copolymers as the precursors. The Agr-PEG cross-linked systems were further deposited onto a SS surface, pre-functionalized with an alkynyl-containing biomimetic anchor, dopamine propiolamide, to form a thin film after thermal treatment. The thin film-coated SS surfaces can effectively reduce the adhesion of marine algae and the settlement of barnacle cyprids. Upon covalent cross-linking, the covalently cross-linked Agr-PEG films coated SS surfaces exhibit good stability in flowing artificial seawater, and enhanced resistance to the settlement of barnacle cyprids, in comparison to that of the surfaces coated with physically cross-linked AgrAz films.

  1. Crosslinking of micropatterned collagen-based nerve guides to modulate the expected half-life.

    PubMed

    Salvatore, L; Madaghiele, M; Parisi, C; Gatti, F; Sannino, A

    2014-12-01

    The microstructural, mechanical, compositional, and degradative properties of a nerve conduit are known to strongly affect the regenerative process of the injured peripheral nerve. Starting from the fabrication of micropatterned collagen-based nerve guides, according to a spin-casting process reported in the literature, this study further investigates the possibility to modulate the degradation rate of the scaffolds over a wide time frame, in an attempt to match different rates of nerve regeneration that might be encountered in vivo. To this aim, three different crosslinking methods, that is, dehydrothermal (DHT), carbodiimide-based (EDAC), and glutaraldehyde-based (GTA) crosslinking, were selected. The elastically effective degree of crosslinking, attained by each method and evaluated according to the classical rubber elasticity theory, was found to significantly tune the in vitro half-life (t1/2 ) of the matrices, with an exponential dependence of the latter on the crosslink density. The high crosslinking efficacy of EDAC and GTA treatments, respectively threefold and fourfold when compared to the one attained by DHT, led to a sharp increase of the corresponding in vitro half-lives (ca., 10, 172, and 690 h, for DHT, EDAC, and GTA treated matrices, respectively). As shown by cell viability assays, the cytocompatibility of both DHT and EDAC treatments, as opposed to the toxicity of GTA, suggests that such methods are suitable to crosslink collagen-based scaffolds conceived for clinical use. In particular, nerve guides with expected high residence times in vivo might be produced by finely controlling the biocompatible reaction(s) adopted for crosslinking.

  2. ROMP-based thermosetting polymers from modified castor oil with various cross-linking agents

    NASA Astrophysics Data System (ADS)

    Ding, Rui

    Polymers derived from bio-renewable resources are finding an increase in global demand. In addition, polymers with distinctive functionalities are required in certain advanced fields, such as aerospace and civil engineering. In an attempt to meet both these needs, the goal of this work aims to develop a range of bio-based thermosetting matrix polymers for potential applications in multifunctional composites. Ring-opening metathesis polymerization (ROMP), which recently has been explored as a powerful method in polymer chemistry, was employed as a unique pathway to polymerize agricultural oil-based reactants. Specifically, a novel norbornyl-functionalized castor oil alcohol (NCA) was investigated to polymerize different cross-linking agents using ROMP. The effects of incorporating dicyclopentadiene (DCPD) and a norbornene-based crosslinker (CL) were systematically evaluated with respect to curing behavior and thermal mechanical properties of the polymers. Isothermal differential scanning calorimetry (DSC) was used to investigate the conversion during cure. Dynamic DSC scans at multiple heating rates revealed conversion-dependent activation energy by Ozawa-Flynn-Wall analysis. The glass transition temperature, storage modulus, and loss modulus for NCA/DCPD and NCA/CL copolymers with different cross-linking agent loading were compared using dynamic mechanical analysis. Cross-link density was examined to explain the very different dynamic mechanical behavior. Mechanical stress-strain curves were developed through tensile test, and thermal stability of the cross-linked polymers was evaluated by thermogravimetric analysis to further investigate the structure-property relationships in these systems.

  3. Crosslinking method of hyaluronic-based hydrogel for biomedical applications

    PubMed Central

    Khunmanee, Sureerat; Jeong, Younghyen; Park, Hansoo

    2017-01-01

    In the field of tissue engineering, there is a need for advancement beyond conventional scaffolds and preformed hydrogels. Injectable hydrogels have gained wider admiration among researchers as they can be used in minimally invasive surgical procedures. Injectable gels completely fill the defect area and have good permeability and hence are promising biomaterials. The technique can be effectively applied to deliver a wide range of bioactive agents, such as drugs, proteins, growth factors, and even living cells. Hyaluronic acid is a promising candidate for the tissue engineering field because of its unique physicochemical and biological properties. Thus, this review provides an overview of various methods of chemical and physical crosslinking using different linkers that have been investigated to develop the mechanical properties, biodegradation, and biocompatibility of hyaluronic acid as an injectable hydrogel in cell scaffolds, drug delivery systems, and wound healing applications. PMID:28912946

  4. Ruthenium-catalyzed photo cross-linking of fibrin-based engineered tissue

    PubMed Central

    Bjork, Jason W.; Johnson, Sandra L.; Tranquillo, Robert T.

    2012-01-01

    Most cross-linking methods utilize chemistry or physical processes that are detrimental to cells and tissue development. Those that are not as harmful often do not provide a level of strength that ultimately meets the required application. The purpose of this work was to investigate the use of a ruthenium-sodium persulfate cross-linking system to form dityrosine in fibrin-based engineered tissue. By utilizing the tyrosine residues inherent to fibrin and cell-deposited proteins, at least 3-fold mechanical strength increases and 10-fold stiffness increases were achieved after cross-linking. This strengthening and stiffening effect was found to increase with culture duration prior to cross-linking such that physiologically relevant properties were obtained. Fibrin was not required for this effect as demonstrated by testing with collagen-based engineered tissue. Cross-linked tissues were implanted subcutaneously and shown to have minimal inflammation after 30 days, similar to non-cross-linked controls. Overall, the method employed is rapid, non-toxic, minimally inflammatory, and is capable of increasing strength and stiffness of engineered tissues to physiological levels. PMID:21196047

  5. Control of crosslinking for tailoring collagen-based scaffolds stability and mechanics

    PubMed Central

    Davidenko, N.; Schuster, C.F.; Bax, D.V.; Raynal, N.; Farndale, R.W.; Best, S.M.; Cameron, R.E.

    2015-01-01

    We provide evidence to show that the standard reactant concentrations used in tissue engineering to cross-link collagen-based scaffolds are up to 100 times higher than required for mechanical integrity in service, and stability against degradation in an aqueous environment. We demonstrate this with a detailed and systematic study by comparing scaffolds made from (a) collagen from two different suppliers, (b) gelatin (a partially denatured collagen) and (c) 50% collagen–50% gelatin mixtures. The materials were processed, using lyophilisation, to produce homogeneous, highly porous scaffolds with isotropic architectures and pore diameters ranging from 130 to 260 μm. Scaffolds were cross-linked using a carbodiimide treatment, to establish the effect of the variations in crosslinking conditions (down to very low concentrations) on the morphology, swelling, degradation and mechanical properties of the scaffolds. Carbodiimide concentration of 11.5 mg/ml was defined as the standard (100%) and was progressively diluted down to 0.1%. It was found that 10-fold reduction in the carbodiimide content led to the significant increase (almost 4-fold) in the amount of free amine groups (primarily on collagen lysine residues) without compromising mechanics and stability in water of all resultant scaffolds. The importance of this finding is that, by reducing cross-linking, the corresponding cell-reactive carboxylate anions (collagen glutamate or aspartate residues) that are essential for integrin-mediated binding remain intact. Indeed, a 10-fold reduction in carbodiimide crosslinking resulted in near native-like cell attachment to collagen scaffolds. We have demonstrated that controlling the degree of cross-linking, and hence retaining native scaffold chemistry, offers a major step forward in the biological performance of collagen- and gelatin-based tissue engineering scaffolds. Statement of Significance This work developed collagen and gelatine-based scaffolds with structural

  6. Anti-crease finishing of cotton fabrics based on crosslinking of cellulose with acryloyl malic acid.

    PubMed

    Qi, Huan; Huang, Yangen; Ji, Bolin; Sun, Gang; Qing, Feng-Ling; Hu, Chunyan; Yan, Kelu

    2016-01-01

    Maleic acid (MA) has been explored to replace formaldehyde-based dimethylol dihydroxy ethylene urea (DMDHEU) for cotton anti-crease finishing. However, the resilience of treated fabrics was not satisfactorily improved. In this study, acryloyl malic acid (AMA) was synthesized and applied on fabrics as a novel crosslinking agent. The results showed that both crease recovery angle and whiteness index of treated samples were higher than those of MA in the presence/absence of catalyst sodium hypophosphite (SHP). Chemical structure of AMA was confirmed by NMR and MS spectra. The possible crosslinking mechanism between AMA and cellulose was investigated by means of (13)C NMR, MS, FTIR and phosphorus content analyses. It was found that AMA could form ester bonds with cellulose by formation of anhydride intermediate. Meanwhile, additional reaction of double bonds on AMA with another molecule or PH of SHP residual has also contributed to the crosslinking. A reaction equation was proposed based on the analyses.

  7. Effect of crosslinking in chitosan/aloe vera-based membranes for biomedical applications.

    PubMed

    Silva, S S; Caridade, S G; Mano, J F; Reis, R L

    2013-10-15

    The positive interaction between polysaccharides with active phytochemicals found in medicinal plants may represent a strategy to create active wound dressing materials useful for skin repair. In the present work, blended membranes composed of chitosan (Cht) and aloe vera gel were prepared through the solvent casting, and were crosslinked with genipin to improve their properties. Topography, swelling, wettability, mechanical properties and in vitro cellular response of the membranes were investigated. With the incorporation of aloe vera gel into chitosan solution, the developed chitosan/aloe-based membranes displayed increased roughness and wettability; while the genipin crosslinking promoted the formation of stiffer membranes in comparison to those of the non-modified membranes. Moreover, in vitro cell culture studies evidenced that the L929 cells have high cell viability, confirmed by MTS test and calcein-AM staining. The findings suggested that both blend compositions and crosslinking affected the physico-chemical properties and cellular behavior of the developed membranes.

  8. Mechanism-based protein cross-linking probes to investigate carrier protein-mediated biosynthesis.

    PubMed

    Worthington, Andrew S; Rivera, Heriberto; Torpey, Justin W; Alexander, Matthew D; Burkart, Michael D

    2006-12-20

    Fatty acid, polyketide, and nonribosomal peptide biosynthetic enzymes perform structural modifications upon small molecules that remain tethered to a carrier protein. This manuscript details the design and analysis of cross-linking substrates that are selective for acyl carrier proteins and their cognate condensing enzymes. These inactivators are engineered through a covalent linkage to fatty acid acyl carrier protein via post-translational modification to contain a reactive probe that traps the active site cysteine residue of ketosynthase domains. These proteomic tools are applied to Escherichia coli fatty acid synthase enzymes, where KASI and KASII selectively cross-link ACP-bound epoxide and chloroacrylate moieties. These mechanism-based, protein-protein fusion reagents also demonstrated cross-linking of KASI to type II polyketide ACPs, while nonribosomal peptide carrier proteins showed no reactivity. Similar investigations into protein-protein interactions, proximity effects, and substrate specificities will be required to complete the mechanistic understanding of these pathways.

  9. Carbon Nanofiber Incorporated Silica Based Aerogels with Di-Isocyanate Cross-Linking

    NASA Technical Reports Server (NTRS)

    Vivod, Stephanie L.; Meador, Mary Ann B.; Capadona, Lynn A.; Sullivan, Roy M.; Ghosn, Louis J.; Clark, Nicholas; McCorkle, Linda

    2008-01-01

    Lightweight materials with excellent thermal insulating properties are highly sought after for a variety of aerospace and aeronautic applications. (1) Silica based aerogels with their high surface area and low relative densities are ideal for applications in extreme environments such as insulators for the Mars Rover battery. (2) However, the fragile nature of aerogel monoliths prevents their widespread use in more down to earth applications. We have shown that the fragile aerogel network can be cross-linked with a di-isocyanate via amine decorated surfaces to form a conformal coating. (3) This coating reinforces the neck regions between secondary silica particles and significantly strengthens the aerogels with only a small effect on density or porosity. Scheme 1 depicts the cross-linking reaction with the di-isocyanate and exhibits the stages that result in polymer cross-linked aerogel monoliths.

  10. Conformational analysis of a covalently cross-linked Watson-Crick base pair model.

    PubMed

    Jensen, Erik A; Allen, Benjamin D; Kishi, Yoshito; O'Leary, Daniel J

    2008-11-15

    Low-temperature NMR experiments and molecular modeling have been used to characterize the conformational behavior of a covalently cross-linked DNA base pair model. The data suggest that Watson-Crick or reverse Watson-Crick hydrogen bonding geometries have similar energies and can interconvert at low temperatures. This low-temperature process involves rotation about the crosslink CH(2)C(5') (psi) carbon-carbon bond, which is energetically preferred over the alternate CH(2)N(3) (phi) carbon-nitrogen bond rotation.

  11. Biodegradable Photo-Crosslinked Thin Polymer Networks Based on Vegetable Oil Hydroxyfatty Acids

    USDA-ARS?s Scientific Manuscript database

    Novel crosslinked thin polymer networks based on vegetable oil hydroxyfatty acids (HFAs) were prepared by UV photopolymerization and their mechanical properties were evaluated. Two raw materials, castor oil and 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) were used as sources of mono- and di-HFAs, r...

  12. Fabrication of starch-based microparticles by an emulsification-crosslinking method

    USDA-ARS?s Scientific Manuscript database

    Starch-based microparticles (MPs) fabricated by a water-in-water (w/w) emulsification-crosslinking method could be used as a controlled-release delivery vehicle for food bioactives. Due to the processing route without the use of toxic organic solvents, it is expected that these microparticles can be...

  13. Self-crosslinking for dimensionally stable and solvent-resistant quaternary phosphonium based hydroxide exchange membranes

    SciTech Connect

    Gu, S; Cai, R; Yan, YS

    2011-01-01

    A simple self-crosslinking strategy, without the needs of a separate crosslinker or a catalyst, is reported here. The crosslinking drastically lowers the water swelling ratio (e.g., 5-10 folds reduction) and provides excellent solvent-resistance. The self-crosslinked membrane (DCL: 5.3%) shows the highest IEC-normalized hydroxide conductivity among all crosslinked HEMs reported.

  14. Is dialdehyde starch a valuable cross-linking agent for collagen/elastin based materials?

    PubMed

    Skopinska-Wisniewska, J; Wegrzynowska-Drzymalska, K; Bajek, A; Maj, M; Sionkowska, A

    2016-04-01

    Collagen and elastin are the main structural proteins in mammal bodies. They provide mechanical support, strength, and elasticity to various organs and tissues, e.g. skin, tendons, arteries, and bones. They are readily available, biodegradable, biocompatible and they stimulate cell growth. The physicochemical properties of collagen and elastin-based materials can be modified by cross-linking. Glutaraldehyde is one of the most efficient cross-linking agents. However, the unreacted molecules can be released from the material and cause cytotoxic reactions. Thus, the aim of our work was to investigate the influence of a safer, macromolecular cross-linking agent--dialdehyde starch (DAS). The properties of hydrogels based on collagen/elastin mixtures (95/5, 90/10) containing 5 and 10% of DAS and neutralized via dialysis against deionized water were tested. The homogenous, transparent, stiff hydrogels were obtained. The DAS addition causes the formation of intermolecular cross-linking bonds but does not affect the secondary structure of the proteins. As a result, the thermal stability, mechanical strength, and, surprisingly, swelling ability increased. At the same time, the surface properties test and in vitro study show that the materials are attractive for 3T3 cells. Moreover, the materials containing 10% of DAS are more resistant to enzymatic degradation.

  15. Synthesis of temperature and pH-responsive crosslinked micelles from polypeptide-based graft copolymer.

    PubMed

    Zhao, Changwen; He, Pan; Xiao, Chunsheng; Gao, Xiaoye; Zhuang, Xiuli; Chen, Xuesi

    2011-07-15

    A polypeptide-based double hydrophilic graft copolymer was synthesized by the sequential grafting of poly(N-isopropylacrylamide) (PNIPAM) and 2-hydroxyethyl methacrylate (HEMA) onto poly(l-glutamic acid) (PGA) backbone. The copolymers were sensitive to both temperature and pH. The phase transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering (DLS). The light transmittance decrease of the copolymers at temperature above lower critical solution temperature (LCST) was remarkably weakened at pH around 6.5 due to the coil to α helix change of PGA chain induced by pH. The copolymers can self-assembly into micelles with PNIPAM cores in the aqueous solution at pH 8.0 and 60°C. Subsequently, polymerization of HEMA led to the facile preparation of crosslinked micelles, which were observed directly by transmission electron microscopy (TEM). The temperature controlled shrinkage behaviors of crosslinked micelles highly depended on the pH values of the solution. The crosslinked micelles aggregated at pH 5.0 due to the increased hydrophobic interactions among them induced by the protonation of PGA component. These crosslinked micelles have promising applications as intelligent drug delivery vehicles. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Cross-linked high conductive membranes based on water soluble ionomer for high performance proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Guo, Xin; Zhang, Gang; Ni, Jing; Zhao, Chengji; Liu, Zhongguo; Zhang, Liyuan; Li, Mingyu; Xu, Shuai; Na, Hui

    2013-11-01

    In this paper, a series of proton exchange membranes prepared by “Click Reaction” are reported. The cross-linked membranes are based on water soluble sulfonated poly (ether ether ketone) containing dipropenyl groups (SDPEEK-nE/nH). Compared with self-crosslinked membranes (SDPEEK-nS), this “Click” cross-linked membranes using 1,2-Ethanedithiol and 1,6-Hexanedithiol as the cross-linker exhibit extremely reduced water uptake and swelling ratio. The lowest proton conductivity at 80 °C of the “Click” cross-linked membranes reaches to 0.168 S cm-1, and the highest methanol permeability of the “Click” cross-linked SDPEEK-8E is only 4.13 × 10-7 cm2 s-1, which is 5 times lower than that of Nafion 117 membrane. All the results imply that the cross-linked membranes with novel thiol cross-linker are promising alternative material for fuel cell application.

  17. Radiation-crosslinking of shape memory polymers based on poly(vinyl alcohol) in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Basfar, A. A.; Lotfy, S.

    2015-01-01

    Shape memory polymers based on poly(vinyl alcohol) (SM-PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA) and multi-wall carbon nanotubes (MWCNTs) crosslinked by ionizing radiation were investigated. Chemical-crosslinking of PVA by glutaraldehyde in the presence of CEA and MWCNTs was also studied. The swelling and gel fraction of the radiation-crosslinked SM-PVA and chemically crosslinked systems were evaluated. Analysis of the swelling and gel fraction revealed a significant reduction in swelling and an increase in the gel fraction of the material that was chemically crosslinked with glutaraldehyde. The radiation-crosslinked SM-PVA demonstrated 100% gelation at an irradiation dose of 50 kGy. In addition, radiation-crosslinked SM-PVA exhibited good temperature responsive shape-memory behavior. A scanning electron microscopy (SEM) analysis was performed. The thermal properties of radiation-crosslinked SM-PVA were investigated by a thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The ability of the material to return or store energy (E‧), to its ability to lose energy (E″), and the ratio of these effects (Tanδ), which is called damping were examined via DMA. The temperature of Tanδ in the radiation-crosslinked SM-PVA decreased significantly by 6 and 13 °C as a result of the addition of MWCNTs. In addition, the temperature of Tanδ for SM-PVA increased as the irradiation dose increased. These radiation-crosslinked SM-PVA materials show promising shape-memory behavior based on the range of temperatures at which Tanδ appears.

  18. Cell-free deoxyribonucleic acid as a prognostic marker of bowel ischemia in patients with small bowel obstruction.

    PubMed

    Netz, Uri; Perry, Zvi; Mizrahi, Solly; Kirshtein, Boris; Czeiger, David; Sebbag, Gilbert; Reshef, Avraham; Douvdevani, Amos

    2017-08-07

    Patients with strangulation small bowel obstruction are at a high risk for serious morbidity and mortality due to ischemic bowel. Measuring serum, cell-free deoxyribonucleic acid levels could help recognize early cell death. Our hypothesis was that small bowel ischemia or necrosis is associated with increases in serum cell-free deoxyribonucleic acid and that recovery is associated with a decrease in cell-free deoxyribonucleic acid levels. A prospective cohort study in addition to standard treatment of patients admitted with a diagnosis of small bowel obstruction. The participants were divided into groups depending on the presence of ischemic or necrotic bowel according to operative and clinical outcome. Clinical data and serum-based cell-free deoxyribonucleic acid levels were compared. Cell-free deoxyribonucleic acid levels from these 2 groups also were compared with a third group of healthy controls. In the study, 58 patients were enrolled, and 18 patients (31%) underwent operation. During the operative procedure, ischemic or necrotic bowel was found in 10 cases (17%). Serum levels of cell-free deoxyribonucleic acid at the time of admission in the ischemic/necrotic bowel group were increased compared with patients with well perfused or spontaneously recovered bowel (P = .03). Cell-free deoxyribonucleic acid levels decreased on the day after admission in 88% of the nonoperated patients. No significant differences were found in demographics, medical background, imaging performed, and cause of obstruction nor in clinical admission data. Surgeons currently rely on imprecise clinical parameters, including degree of pain, abdominal tenderness, leukocytosis etc to decide when operative intervention is needed. The association of cell-free deoxyribonucleic acid with small bowel obstruction, ischemia, and recovery supports our hypothesis and suggests that this biomarker is a potential surrogate of small bowel perfusion. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Role of Ribonucleic Acid Synthesis in Replication of Deoxyribonucleic Acid

    PubMed Central

    Pato, Martin L.

    1975-01-01

    An experiment previously interpreted to show a ribonucleic acid requirement for propagation of deoxyribonucleic replication is reexamined and the earlier interpretation is shown to be incorrect. PMID:1090599

  20. Crosslinked hydrogels based on biological macromolecules with potential use in skin tissue engineering.

    PubMed

    Vulpe, Raluca; Popa, Marcel; Picton, Luc; Balan, Vera; Dulong, Virginie; Butnaru, Maria; Verestiuc, Liliana

    2016-03-01

    Zero-length crosslinked hydrogels have been synthesized by covalent linking of three natural polymers (collagen, hyaluronic acid and sericin), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The hydrogels have been investigated by FT-IR spectroscopy, microcalorimetry, in vitro swelling, enzymatic degradation, and in vitro cell viability studies. The obtained crosslinked hydrogels showed a macroporous structure, high swelling degree and in vitro enzymatic resistance compared to uncrosslinked collagen. The in vitro cell viability studies performed on normal human dermal fibroblasts assessed the sericin proliferation properties indicating a potential use of the hydrogels based on collagen, hyaluronic acid and sericin in skin tissue engineering. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks

    PubMed Central

    Jha, Amit K.; Hule, Rohan A.; Jiao, Tong; Teller, Sean S.; Clifton, Rodney J.; Duncan, Randall L.; Pochan, Darrin J.; Jia, Xinqiao

    2009-01-01

    We have created a new class of hyaluronic acid (HA)-based hydrogel materials with HA hydrogel particles (HGPs) embedded in and covalently cross-linked to a secondary network. HA HGPs with an average diameter of ∼900 nm and narrow particle size distribution were synthesized using a refined reverse micelle polymerization technique. The average mesh size of the HGPs was estimated to be approximately 5.5 to 7.0 nm by a protein uptake experiment. Sodium periodate oxidation not only introduced aldehyde groups to the particles but also reduced the average particle size. The aldehyde groups generated were used as reactive handles for subsequent cross-linking with an HA derivative containing hydrazide groups. The resulting macroscopic gels contain two distinct hierarchical networks (doubly cross-linked networks, DXNs): one within individual particles and another among different particles. Bulk gels (BGs) formed by direct mixing of HA derivatives with mutually reactive groups were included for comparison. The hydrogel microstructures were collectively characterized by microscopy and neutron scattering techniques. Their viscoelasticity was quantified at low frequencies (0.1−10 Hz) using a controlled stress rheometer and at high frequencies (up to 200 Hz) with a home-built torsional wave apparatus. Both BGs and DXNs are stable elastic gels that become stiffer at higher frequencies. The HA-based DXN offers unique structural hierarchy and mechanical properties that are suitable for soft tissue regeneration. PMID:20046226

  2. Rheological study of in-situ crosslinkable hydrogels based on hyaluronanic acid, collagen and sericin.

    PubMed

    Vulpe, Raluca; Le Cerf, Didier; Dulong, Virginie; Popa, Marcel; Peptu, Catalina; Verestiuc, Liliana; Picton, Luc

    2016-12-01

    The elaboration of chemically crosslinked hydrogels based on collagen (C), hyaluronanic acid (HA) and sericin (S) with different polymer ratios was investigated by in-situ rheology. This reaction was performed via amide or ester bond reaction activated by carbodiimide, in pure water. Prior to molecule crosslinking, the rheological behaviour of the biopolymers (alone or in mixture) was characterized in a semi-dilute concentration regime. Both flow and dynamic measurements showed that uncrosslinked collagen alone appears to be rather elastic with yield stress properties, whereas uncrosslinked HA alone appears to be rather shear thinning and viscoelastic in agreement with entangled polymer behaviour. Sericin exhibited Newtonian low viscosity behaviour according to its very low molar mass. Before crosslinking, HA exhibited viscoelastic behaviour at concentrations above the critical entangled concentration (C*) in the mixtures, thus HA shows promise as a matrix for future crosslinked networks, whereas sericin did not significantly modify the rheology. During the reaction, followed by rheology, the kinetics were slower for pure HA systems compared with the mixtures (i.e., with added collagen and/or to a lesser extent sericin). At the same time, the final network of hydrogels (i.e., the elastic modulus) was more structured in the mixture based systems. This result is explained by ester bonds (the only possibility for pure HA systems), which are less favourable and reactive than amide bonds (possible with sericin and collagen). The presence of collagen in the HA matrix reinforced the hydrogel network. SEM studies confirmed the structure of the hydrogels, and in vitro degradability was globally consistent with the effect of the selected enzyme according to the hydrogel composition. All the elaborated hydrogels were non-cytotoxic in vitro. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Acid–base bifunctional shell cross-linked micelle nanoreactor for one-pot tandem reaction

    DOE PAGES

    Lee, Li -Chen; Lu, Jie; Weck, Marcus; ...

    2015-12-29

    In shell cross-linked micelles (SCMs) containing acid sites in the shell and base sites in the core are prepared from amphiphilic poly(2-oxazoline) triblock copolymers. These materials are utilized as two-chamber nanoreactors for a prototypical acid-base bifunctional tandem deacetalization-nitroaldol reaction. Furthermore, the acid and base sites are localized in different regions of the micelle, allowing the two steps in the reaction sequence to largely proceed in separate compartments, akin to the compartmentalization that occurs in biological systems.

  4. 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.

  5. Mechanical properties and failure analysis of visible light crosslinked alginate-based tissue sealants.

    PubMed

    Charron, Patrick N; Fenn, Spencer L; Poniz, Alex; Oldinski, Rachael A

    2016-06-01

    Moderate to weak mechanical properties limit the use of naturally-derived tissue sealants for dynamic medical applications, e.g., sealing a lung leak. To overcome these limitations, we developed visible-light crosslinked alginate-based hydrogels, as either non-adhesive methacrylated alginate (Alg-MA) hydrogel controls, or oxidized Alg-MA (Alg-MA-Ox) tissue adhesive tissue sealants, which form covalent bonds with extracellular matrix (ECM) proteins. Our study investigated the potential for visible-light crosslinked Alg-MA-Ox hydrogels to serve as effective surgical tissue sealants for dynamic in vivo systems. The Alg-MA-Ox hydrogels were designed to be an injectable system, curable in situ. Burst pressure experiments were conducted on a custom-fabricated burst pressure device using constant air flow; burst pressure properties and adhesion characteristics correlated with the degrees of methacrylation and oxidation. In summary, visible light crosslinked Alg-MA-Ox hydrogel tissue sealants form effective seals over critically-sized defects, and maintain pressures up to 50mm Hg. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Mechanical Properties and Failure Analysis of Visible Light Crosslinked Alginate-Based Tissue Sealants

    PubMed Central

    Charron, Patrick; Fenn, Spencer L.; Poniz, Alex; Oldinski, Rachael A.

    2016-01-01

    Moderate to weak mechanical properties limit the use of naturally-derived tissue sealants for dynamic medical applications, e.g., sealing a lung leak. To overcome these limitations, we developed visible-light crosslinked alginate-based hydrogels, as either non-adhesive methacrylated alginate (Alg-MA) hydrogel controls, or oxidized Alg-MA (Alg-MA-Ox) tissue adhesive tissue sealants, which form covalent bonds with extracellular matrix (ECM) proteins. Our study investigated the potential for visible-light crosslinked Alg-MA-Ox hydrogels to serve as effective surgical tissue sealants for dynamic in vivo systems. The Alg-MA-Ox hydrogels were designed to be an injectable system, curable in situ. Burst pressure experiments were conducted on a custom-fabricated burst pressure device using constant air flow; burst pressure properties and adhesion characteristics correlated with the degrees of methacrylation and oxidation. In summary, visible light crosslinked Alg-MA-Ox hydrogel tissue sealants form effective seals over critically-sized defects, and maintain pressures up to 50 mm Hg. PMID:26897093

  7. Diffusion Coefficients of Water and Leachables in Methacrylate-based Crosslinked Polymers using Absorption Experiments

    PubMed Central

    Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette

    2012-01-01

    The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10−8 cm2/sec (co-monomer TMTMA) to 3.15 × 10−8 cm2/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R2 = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R2 = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592

  8. Low molecular weight PEIs modified by hydrazone-based crosslinker and betaine as improved gene carriers.

    PubMed

    Fang, Gang; Zeng, Fang; Yu, Changmin; Wu, Shuizhu

    2014-10-01

    Low-molecular-weight polyethyleneimine (LMW PEI) exhibits poorer transfection efficiency but lower cytotoxicity compared to high-molecular-weight polyethyleneimine (such as PEI 25kDa). To enhance the gene transfection performance of LMW PEI, we herein demonstrate a new strategy for modifying LMW PEI. A crosslinker containing an acid-labile hydrazone bond (hydrazone-based crosslinker) was synthesized and used to crosslink PEI 1.8kDa and convert it into higher-molecular-weight polycations. And the crosslinked polycations were further modified by incorporating a betaine monomer [N,N-dimethyl(acrylamidopropyl)ammonium propane sulfonate, DMAAPS] onto their surfaces. The molar percentages of the incorporated betaine molecules to amino groups on the polycations were determined as 21.2%, 36.0% and 77.2%, respectively. Molecular weights of the modified polycations were measured using capillary viscometry at pH 7.4 and 5.0, respectively, and the degradation of the polymers in acidic solution was confirmed. The PEIs modified with hydrazone and betaine (PEI-Hdz-DMAAPS) exhibit much lower cytotoxicity than PEI 25K, and they also show no or little hemolytic effect with their hemolysis rates around 5%. PEI-Hdz-DMAAPS21.2%/DNA and PEI-Hdz-DMAAPS36.0%/DNA complexes exhibit high transfection efficiencies, which are comparable to or higher than that of PEI 25K/DNA complex in the absence or presence of 10% serum. With these improved gene delivery properties, the PEI-Hdz-DMAAPS samples have great potential for serving as efficient gene carriers. This strategy may provide some insights for constructing some other biocompatible materials.

  9. Sugar-based crosslinker forms a stable atelocollagen hydrogel that is a favorable microenvironment for 3D cell culture.

    PubMed

    Kamimura, Wataru; Koyama, Hiroyuki; Miyata, Tetsuro; Takato, Tsuyoshi

    2014-12-01

    We created sugar-based crosslinkers for precise chemical crosslinking of atelocollagen to form a stable hydrogel microenvironment for three-dimensional (3D) cell culture. Crosslinkers were synthesized by partially oxidizing glucose, fructose, maltose, sucrose, or raffinose with periodate. The partial oxidization of sugar generated multiple aldehydes in the molecule, which acted as multifunctional crosslinkers, allowing atelocollagen to form chemical hydrogels. The crosslink reaction of atelocollagen was competitively suppressed by the addition of amino acid-rich medium, enabling flexible control of 3D molecular density in the acquired hydrogel. To evaluate structural stability, ultrasonic stress was loaded onto the acquired hydrogel and sequential measurement of water content showed that the crosslinking considerably stabilized the hydrogel structure. The effectiveness of the atelocollagen hydrogel as a 3D culture scaffold was analyzed by embedding and culturing endothelial cells or cardiomyocytes in it. Endothelial cells formed 3D capillary-like structures at 12 h, and cardiomyocytes formed a beating 3D netlike structure by 7 days. These findings suggest that crosslinked atelocollagen hydrogel effectively functions as a stable scaffold in 3D culture.

  10. Identification of Cross-Linked Peptides after Click-Based Enrichment Using Sequential Collision-Induced Dissociation and Electron Transfer Dissociation Tandem Mass Spectrometry

    SciTech Connect

    Chowdhury, Saiful M.; Du, Xiuxia; Tolic, Nikola; Wu, Si; Moore, Ronald J.; Mayer, M. Uljana; Smith, Richard D.; Adkins, Joshua N.

    2009-07-01

    Chemical cross-linking combined with mass spectrometric analysis is emerging as a powerful technique for protein-protein interaction and protein structure elucidation studies.1 Cross-linkers covalently link two interacting proteins, often with chemistries specific to certain amino acid side chains. After enzymatic digestion of the proteins, the resulting cross-linked peptides can be subjected to analysis by LC-MS(/MS) to identify cross-linked species.2,3 For studying protein interactions using chemical cross-linking towards global discovery-based applications, the critical needs are the development of cross-linkers that are highly specific, amenable to LC-MS/MS, and resulting spectra are interpretable by bioinformatics tools to automatically assign cross-linked peptides with high confidence.4-10 As recently mentioned by Aebersold and co-workers, due to the low relative abundances of cross-linking products compared to their unmodified counterparts, enrichment of cross-linked species is also highly desirable to improve the likelihood of unambiguous identification of cross-linked peptides.6 Most of the currently available enrichable cross-linkers are bulky and are not amenable to studying protein-protein interactions in vivo. To discover protein-protein interactions with high confidence, there is a need for chemical cross-linkers that can effectively label protein complexes, utilize mass spectrometry based bottom-up proteomics analysis pipelines and also contains enrichment functionality.

  11. Chitosan-based membranes with different ionic crosslinking density for pharmaceutical and industrial applications.

    PubMed

    Gierszewska, Magdalena; Ostrowska-Czubenko, Jadwiga

    2016-11-20

    Chitosan membranes (Ch), ionically crosslinked with pentasodium tripolyphosphate (TPP), were prepared using chitosan of medium and high molecular weight of similar degree of deacetylation and different crosslinking conditions. An effect of synthesis conditions (pH of crosslinking TPP solution equal to 5.5 and 9.0) on molecular and supermolecular structure and on crosslinking density of Ch/TPP membranes was confirmed using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) method and energy dispersive X-ray (EDX) spectrometry. Atomic-force microscopy (AFM) and contact angle measurements indicated some differences in membrane roughness and hydrophilicity. The state of water in non-crosslinked and ionically crosslinked Ch membranes containing different amount of water was investigated by low temperature differential scanning calorimetry (DSC) measurements. DSC analysis confirmed presence of freezing and non-freezing water in non-crosslinked and ionically crosslinked membranes. The amount of non-freezing water generally decreased after Ch crosslinking and was affected by crosslinking conditions and crosslinking density. Molecular weight of Ch had only slight influence on all characterized properties of ionically crosslinked membranes.

  12. Preparation and properties of photo-crosslinkable hydrogel based on photopolymerizable chitosan derivative.

    PubMed

    Qi, Zaiqian; Xu, Juan; Wang, Zhiliang; Nie, Jun; Ma, Guiping

    2013-02-01

    Photopolymerizable chitosan derivative was synthesized by chitosan and methyl acroloyl glycine (MAG). The chemical structures and physical properties were characterized by FT-IR, (1)H NMR, XRD and TGA. The thermal stability of chitosan derivative was lower than chitosan. The chitosan derivative was amorphous compared with the high degree crystallization of chitosan. The hydrogels were prepared based on chitosan derivative via photopolymerization with different concentrations of photoinitiator 2959. The surface of hydrogel showed porous network and the pore size distribution tended to become homogeneous with the increase of the concentration of 2959, while the swelling property decreased due to more crosslinking. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. A strong integrated strength and toughness artificial nacre based on dopamine cross-linked graphene oxide.

    PubMed

    Cui, Wei; Li, Mingzhu; Liu, Jiyang; Wang, Ben; Zhang, Chuck; Jiang, Lei; Cheng, Qunfeng

    2014-09-23

    Demands of the strong integrated materials have substantially increased across various industries. Inspired by the relationship of excellent integration of mechanical properties and hierarchical nano/microscale structure of the natural nacre, we have developed a strategy for fabricating the strong integrated artificial nacre based on graphene oxide (GO) sheets by dopamine cross-linking via evaporation-induced assembly process. The tensile strength and toughness simultaneously show 1.5 and 2 times higher than that of natural nacre. Meanwhile, the artificial nacre shows high electrical conductivity. This type of strong integrated artificial nacre has great potential applications in aerospace, flexible supercapacitor electrodes, artificial muscle, and tissue engineering.

  14. Synthesis and characterization of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases

    PubMed Central

    Luo, Hao; Ma, Lianjia; Zhang, Yu; Carr, Peter W.

    2011-01-01

    A novel type of silica-based sulfonate-modified reversed phase (−SO3-HC-C8 ) has been synthesized; it is based on a newly developed acid stable “hyper-crosslinked” C8 derivatized reversed phase, denoted HC-C8. The −SO3-HC-C8 phases containing controlled amounts of sulfonyl groups were made by sulfonating the aromatic hyper-crosslinked network of the HC-C8 phase at different temperatures. The −SO3-HC-C8 phases are only slightly less hydrophobic than the parent HC-C8 phase. The added sulfonyl groups provide a unique strong cation-exchange selectivity to the hydrophobic hyper-crosslinked substrate as indicated by the very large C coefficient as shown by Snyder’s hydrophobic subtraction reversed-phase characterization method. This cation-exchange activity clearly distinguishes the sulfonated phase from all other reversed phases as confirmed by the extraordinary high values of Snyder’s column comparison function Fs. In addition, as was found in previous studies of silica-based and zirconia-based reversed phases, a strong correlation between the cation-exchange interaction and hydrophobic interaction was observed for these sulfonated phases in studies of the retention of cationic solutes. The overall chromatographic selectivity of these −SO3-HC-C8 phases is greatly enhanced by its high hydrophobicity through a “hydrophobically assisted” ion-exchange retention process. PMID:18207150

  15. Crosslinked basement membrane-based coatings enhance glucose sensor function and continuous glucose monitoring in vivo.

    PubMed

    Klueh, Ulrike; Ludzinska, Izabela; Czajkowski, Caroline; Qiao, Yi; Kreutzer, Donald L

    2017-09-05

    Overcoming sensor-induced tissue reactions is an essential element of achieving successful continuous glucose monitoring (CGM) in the management of diabetes, particularly when used in closed loop technology. Recently, we demonstrated that basement membrane (BM)-based glucose sensor coatings significantly reduced tissue reactions at sites of device implantation. However, the biocompatible BM-based biohydrogel sensor coating rapidly degraded over a less than a 3-week period, which effectively eliminated the protective sensor coating. In an effort to increase the stability and effectiveness of the BM coating, we evaluated the impact of crosslinking BM utilizing glutaraldehyde as a crosslinking agent, designated as X-Cultrex. Sensor performance (nonrecalibrated) was evaluated for the impact of these X-Cultrex coatings in vitro and in vivo. Sensor performance was assessed over a 28-day time period in a murine CGM model and expressed as mean absolute relative difference (MARD) values. Tissue reactivity of Cultrex-coated, X-Cultrex-coated, and uncoated glucose sensors was evaluated over a 28-day time period in vivo using standard histological techniques. These studies demonstrated that X-Cultrex-based sensor coatings had no effect on glucose sensor function in vitro. In vivo, glucose sensor performance was significantly enhanced following X-Cultrex coating throughout the 28-day study. Histological evaluations of X-Cultrex-treated sensors demonstrated significantly less tissue reactivity when compared to uncoated sensors. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2017. © 2017 Wiley Periodicals, Inc.

  16. A novel crosslinking strategy for preparing poly(vinyl alcohol)-based proton-conducting membranes with high sulfonation

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-En; Lin, Chi-Wen; Hwang, Bing-Joe

    This study synthesizes poly(vinyl alcohol) (PVA)-based polymer electrolyte membranes by a two-step crosslinking process involving esterization and acetal ring formation reactions. This work also uses sulfosuccinic acid (SSA) as the first crosslinking agent to form an inter-crosslinked structure and a promoting sulfonating agent. Glutaraldehyde (GA) as the second crosslinking agent, reacts with the spare OH group of PVA and forms, not only a dense structure at the outer membrane surface, but also a hydrophobic protective layer. Compared with membranes prepared by a traditional one-step crosslinking process, membranes prepared by the two-step crosslinking process exhibit excellent dissolution resistance in water. The membranes become water-insoluble even at a molar ratio of SO 3H/PVA-OH as high as 0.45. Moreover, the synthesized membranes also exhibit high proton conductivities and high methanol permeability resistance. The current study measures highest proton conductivity of 5.3 × 10 -2 S cm -1 at room temperature from one of the synthesized membranes, higher than that of the Nafion ® membrane. Methanol permeability of the synthesized membranes measures about 1 × 10 -7 cm 2 S -1, about one order of magnitude lower than that of the Nafion ® membrane.

  17. Electrochemical deoxyribonucleic acid biosensor based on the self-assembly film with nanogold decorated on ionic liquid modified carbon paste electrode.

    PubMed

    Gao, Hongwei; Qi, Xiaowei; Chen, Ying; Sun, Wei

    2011-10-17

    An electrochemical DNA biosensor was fabricated by self-assembling probe single-stranded DNA (ssDNA) with a nanogold decorated on ionic liquid modified carbon paste electrode (IL-CPE). IL-CPE was fabricated using 1-butylpyridinium hexafluorophosphate as the binder and the gold nanoparticles were electrodeposited on the surface of IL-CPE (Au/IL-CPE). Then mercaptoacetic acid was self-assembled on the Au/IL-CPE to obtain a layer of modified film, and the ssDNA probe was further covalently-linked with mercaptoacetic acid by the formation of carboxylate ester with the help of N-(3-dimethylamino-propyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The hybridization reaction with the target ssDNA was monitored with methylene blue (MB) as the electrochemical indicator. Under the optimal conditions, differential pulse voltammetric responses of MB was proportional to the specific ssDNA arachis sequences in the concentration range from 1.0×10(-11) to 1.0×10(-6) mol L(-1) with the detection limit as 1.5×10(-12) mol L(-1) (3σ). This electrochemical DNA sensor exhibited good stability and selectivity with the discrimination ability of the one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction product of arachis Arabinose operon D gene was successfully detected by the proposed method, which indicated that the electrochemical DNA sensor designed in this paper could be further used for the detection of specific ssDNA sequence. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Semiconductor sensor embedded microfluidic chip for protein biomarker detection using a bead-based immunoassay combined with deoxyribonucleic acid strand labeling.

    PubMed

    Lin, Yen-Heng; Peng, Po-Yu

    2015-04-15

    Two major issues need to be addressed in applying semiconductor biosensors to detecting proteins in immunoassays. First, the length of the antibody on the sensor surface surpasses the Debye lengths (approximately 1 nm, in normal ionic strength solution), preventing certain specifically bound proteins from being tightly attached to the sensor surface. Therefore, these proteins do not contribute to the sensor's surface potential change. Second, these proteins carry a small charge and can be easily affected by the pH of the surrounding solution. This study proposes a magnetic bead-based immunoassay using a secondary antibody to label negatively charged DNA fragments for signal amplification. An externally imposed magnetic force attaches the analyte tightly to the sensor surface, thereby effectively solving the problem of the analyte protein's distance to the sensor surface surpassing the Debye lengths. In addition, a normal ion intensity buffer can be used without dilution for the proposed method. Experiments revealed that the sensitivity can be improved by using a longer DNA fragment for labeling and smaller magnetic beads as solid support for the antibody. By using a 90 base pair DNA label, the signal was 15 times greater than that without labeling. In addition, by using a 120 nm magnetic bead, a minimum detection limit of 12.5 ng mL(-1) apolipoprotein A1 can be measured. Furthermore, this study integrates a semiconductor sensor with a microfluidic chip. With the help of microvalves and micromixers in the chip, the length of the mixing step for each immunoassay has been reduced from 1h to 20 min, and the sample volume has been reduced from 80 μL to 10 μL. In practice, a protein biomarker in a urinary bladder cancer patient's urine was successfully measured using this technique. This study provides a convenient and effective method to measure protein using a semiconductor sensor.

  19. Physically Cross-linked Polymer Binder Induced by Reversible Acid-Base Interaction for High-Performance Silicon Composite Anodes.

    PubMed

    Lim, Sanghyun; Chu, Hodong; Lee, Kukjoo; Yim, Taeeun; Kim, Young-Jun; Mun, Junyoung; Kim, Tae-Hyun

    2015-10-28

    Silicon is greatly promising for high-capacity anode materials in lithium-ion batteries (LIBs) due to their exceptionally high theoretical capacity. However, it has a big challenge of severe volume changes during charge and discharge, resulting in substantial deterioration of the electrode and restricting its practical application. This conflict requires a novel binder system enabling reliable cyclability to hold silicon particles without severe disintegration of the electrode. Here, a physically cross-linked polymer binder induced by reversible acid-base interaction is reported for high performance silicon-anodes. Chemical cross-linking of polymer binders, mainly based on acidic polymers including poly(acrylic acid) (PAA), have been suggested as effective ways to accommodate the volume expansion of Si-based electrodes. Unlike the common chemical cross-linking, which causes a gradual and nonreversible fracturing of the cross-linked network, a physically cross-linked binder based on PAA-PBI (poly(benzimidazole)) efficiently holds the Si particles even after the large volume changes due to its ability to reversibly reconstruct ionic bonds. The PBI-containing binder, PAA-PBI-2, exhibited large capacity (1376.7 mAh g(-1)), high Coulombic efficiency (99.1%) and excellent cyclability (751.0 mAh g(-1) after 100 cycles). This simple yet efficient method is promising to solve the failures relating with pulverization and isolation from the severe volume changes of the Si electrode, and advance the realization of high-capacity LIBs.

  20. Photopolymerizable nanogels as macromolecular precursors to covalently crosslinked water-based networks.

    PubMed

    Dailing, Eric A; Setterberg, Whitney K; Shah, Parag K; Stansbury, Jeffrey W

    2015-07-28

    We present a strategy for directly and efficiently polymerizing aqueous dispersions of reactive nanogels into covalently crosslinked polymer networks with properties that are determined by the initial chemical and physical nanogel structure. This technique can extend the range of achievable properties and architectures for networks formed in solution, particularly in water where monomer selection for direct polymerization and the final network properties are quite limited. Nanogels were initially obtained from a solution polymerization of a hydrophilic monomethacrylate and either a hydrophilic PEG-based dimethacrylate or a more hydrophobic urethane dimethacrylate, which produced globular particles with diameters of 10-15 nm with remarkably low polydispersity in some cases. Networks derived from a single type of nanogel or a blend of nanogels with different chemistries when dispersed in water gelled within minutes when exposed to low intensity UV light. Modifying the nanogel structure changes both covalent and non-covalent secondary interactions in the crosslinked networks and reveals critical design criteria for the development of networks from highly internally branched, nanoscale prepolymer precursors.

  1. Continuous Sensing Photonic Lab-on-a-Chip Platform Based on Cross-Linked Enzyme Crystals.

    PubMed

    Conejero-Muriel, Mayte; Rodríguez-Ruiz, Isaac; Verdugo-Escamilla, Cristóbal; Llobera, Andreu; Gavira, José A

    2016-12-06

    Microfluidics or lab-on-a-chip technology offer clear advantages over conventional systems such as a dramatic reduction of reagent consumption or a shorter analysis time, which are translated into cost-effective systems. In this work, we present a photonic enzymatic lab-on-a-chip reactor based on cross-linked enzyme crystals (CLECs), able to work in continuous flow, as a highly sensitive, robust, reusable, and stable platform for continuous sensing with superior performance as compared to the state of the art. The microreactor is designed to facilitate the in situ crystallization and crystal cross-linking generating enzymatically active material that can be stored for months/years. Thus, and by means of monolithically integrated micro-optics elements, continuous enzymatic reactions can be spectrophotometrically monitored. Lipase, an enzyme with industrial significance for catalyzed transesterification, hydrolysis, and esterification reactions, is used to demonstrate the potential of the microplatforms as both a continuous biosensor and a microreactor for the synthesis of high value compounds.

  2. Transglutaminase crosslinked pectin- and chitosan-based edible films: a review.

    PubMed

    Porta, Raffaele; Mariniello, Loredana; Di Pierro, Prospero; Sorrentino, Angela; Giosafatto, Concetta Valeria L

    2011-03-01

    The production of biodegradable and edible films with desired mechanical characteristics and gas barrier properties represents one of the most advanced challenges in the field of food wrapping and coating. New edible films can serve not only to provide food with physical protection but also to reduce loss of their moisture, to restrict absorption of oxygen, to lessen migration of lipids, to improve their mechanical handling features, and as materials, to apply in direct contact with internal food to realize a multilayer food packaging. Polymers derived from natural products, like carbohydrates and proteins, offer the greatest opportunities as component of edible films since their biodegradability and environmental compatibility are assured and they can also supplement the nutritional value of specific foods. However, excessive water solubility and poor water vapor barrier properties, and often poor mechanical resistance, have their application limited until the present time. Numerous studies have been carried out to improve their properties by preparing composite and multi-component films or by physically and chemically crosslinking their natural components. In the present review we summarize the main results obtained by crosslinking with the enzyme transglutaminase different proteins contained in multi-component pectin- and chitosan-based edible films, having the aim to create environmentally-friendly "bioplastics" with mechanical and permeability properties similar to the ones exhibited by plastics of petrochemical origin.

  3. Photopolymerizable Nanogels as Macromolecular Precursors to Covalently Crosslinked Water-Based Networks

    PubMed Central

    Dailing, Eric A.; Setterberg, Whitney K.; Shah, Parag K.; Stansbury, Jeffrey W.

    2015-01-01

    We present a strategy for directly and efficiently polymerizing aqueous dispersions of reactive nanogels into covalently crosslinked polymer networks with properties that are determined by the initial chemical and physical nanogel structure. This technique can extend the range of achievable properties and architectures for networks formed in solution, particularly in water where monomer selection for direct polymerization and the final network properties are quite limited. Nanogels were initially obtained from a solution polymerization of a hydrophilic monomethacrylate and either a hydrophilic PEG-based dimethacrylate or a more hydrophobic urethane dimethacrylate, which produced globular particles with diameters of 10–15 nm with remarkably low polydispersity in some cases. Networks derived from a single type of nanogel or a blend of nanogels with different chemistries when dispersed in water gelled within minutes when exposed to low intensity UV light. Modifying the nanogel structure changes both covalent and non-covalent secondary interactions in the crosslinked networks and reveals critical design criteria for the development of networks from highly internally branched, nanoscale prepolymer precursors. PMID:26075300

  4. Remarkable swelling capability of amino acid based cross-linked polymer networks in organic and aqueous medium.

    PubMed

    Roy, Saswati Ghosh; Haldar, Ujjal; De, Priyadarsi

    2014-03-26

    This work reports design and synthesis of side chain amino acid based cross-linked polymeric gels, able to switch over from organogel to hydrogel by a simple deprotection reaction and showing superabsorbancy in water. Amino acid based methacrylate monomers, tert-butoxycarbonyl (Boc)-l/d-alanine methacryloyloxyethyl ester (Boc-l/d-Ala-HEMA), have been polymerized in the presence of a cross-linker via conventional free radical polymerization (FRP) and the reversible addition-fragmentation chain transfer (RAFT) technique for the synthesis of cross-linked polymer gels. The swelling behaviors of these organogels are investigated in organic solvents, and they behave as superabsorbent materials for organic solvents such as dichloromethane, acetone, tetrahydrofuran, etc. Swollen cross-linked polymer gels release the absorbed organic solvent rapidly. After Boc group deprotection from the pendant alanine moiety, the organogels transform to the hydrogels due to the formation of side chain ammonium (-NH3(+)) groups, and these hydrogels showed a significantly high swelling ratio (∼560 times than their dry volumes) in water. The morphology of organogels and hydrogels is studied by field emission scanning electron microscopy (FE-SEM). Amino acid based cross-linked gels could find applications as absorbents for oil spilled on water as well as superabsorbent hydrogels.

  5. The relative contribution of calcium, zinc and oxidation-based cross-links to the stiffness of Arion subfuscus glue.

    PubMed

    Braun, M; Menges, M; Opoku, F; Smith, A M

    2013-04-15

    Metal ions are present in many different biological materials, and are capable of forming strong cross-links in aqueous environments. The relative contribution of different metal-based cross-links was measured in the defensive glue produced by the terrestrial slug Arion subfuscus. This glue contains calcium, magnesium, zinc, manganese, iron and copper. These metals are essential to the integrity of the glue and to gel stiffening. Removal of all metals caused at least a 15-fold decrease in the storage modulus of the glue. Selectively disrupting cross-links involving hard Lewis acids such as calcium reduced the stiffness of the glue, while disrupting cross-links involving borderline Lewis acids such as zinc did not. Calcium is the most common cation bound to the glue (40 mmol l(-1)), and its charge is balanced primarily by sulphate at 82-84 mmol l(-1). Thus these ions probably play a primary role in bringing polymers together directly. Imine bonds formed as a result of protein oxidation also contribute substantially to the stiffness of the glue. Disrupting these bonds with hydroxylamine caused a 33% decrease in storage modulus of the glue, while stabilizing them by reduction with sodium borohydride increased the storage modulus by 40%. Thus a combination of metal-based bonds operates in this glue. Most likely, cross-links directly involving calcium play a primary role in bringing together and stabilizing the polymer network, followed by imine bond formation and possible iron coordination.

  6. Gel-based chemical cross-linking analysis of 20S proteasome subunit-subunit interactions in breast cancer.

    PubMed

    Song, Hai; Xiong, Hua; Che, Jing; Xi, Qing-Song; Huang, Liu; Xiong, Hui-Hua; Zhang, Peng

    2016-08-01

    The ubiquitin-proteasome system plays a pivotal role in breast tumorigenesis by controlling transcription factors, thus promoting cell cycle growth, and degradation of tumor suppressor proteins. However, breast cancer patients have failed to benefit from proteasome inhibitor treatment partially due to proteasome heterogeneity, which is poorly understood in malignant breast neoplasm. Chemical crosslinking is an increasingly important tool for mapping protein three-dimensional structures and proteinprotein interactions. In the present study, two cross-linkers, bis (sulfosuccinimidyl) suberate (BS(3)) and its water-insoluble analog disuccinimidyl suberate (DSS), were used to map the subunit-subunit interactions in 20S proteasome core particle (CP) from MDA-MB-231 cells. Different types of gel electrophoresis technologies were used. In combination with chemical cross-linking and mass spectrometry, we applied these gel electrophoresis technologies to the study of the noncovalent interactions among 20S proteasome subunits. Firstly, the CP subunit isoforms were profiled. Subsequently, using native/SDSPAGE, it was observed that 0.5 mmol/L BS(3) was a relatively optimal cross-linking concentration for CP subunit-subunit interaction study. 2-DE analysis of the cross-linked CP revealed that α1 might preinteract with α2, and α3 might pre-interact with α4. Moreover, there were different subtypes of α1α2 and α3α4 due to proteasome heterogeneity. There was no significant difference in cross-linking pattern for CP subunits between BS(3) and DSS. Taken together, the gel-based characterization in combination with chemical cross-linking could serve as a tool for the study of subunit interactions within a multi-subunit protein complex. The heterogeneity of 20S proteasome subunit observed in breast cancer cells may provide some key information for proteasome inhibition strategy.

  7. Paper based colorimetric biosensing platform utilizing cross-linked siloxane as probe.

    PubMed

    Zhou, Miao; Yang, Minghui; Zhou, Feimeng

    2014-05-15

    Paper based colorimetric biosensing platform utilizing cross-linked siloxane 3-aminopropyltriethoxysilane (APTMS) as probe was developed for the detection of a broad range of targets including H2O2, glucose and protein biomarker. APTMS was extensively used for the modification of filter papers to develop paper based analytical devices. We discovered when APTMS was cross-linked with glutaraldehyde (GA), the resulting complex (APTMS-GA) displays brick-red color, and a visual color change was observed when the complex reacted with H2O2. By integrating the APTMS-GA complex with filter paper, the modified paper enables quantitative detection of H2O2 through the monitoring of the color intensity change of the paper via software Image J. Then, with the immobilization of glucose oxidase (GOx) onto the modified paper, glucose can be detected through the detection of enzymatically generated H2O2. For protein biomarker prostate specific antigen (PSA) assay, we immobilized capture, not captured anti-PSA antibody (Ab1) onto the paper surface and using GOx modified gold nanorod (GNR) as detection anti-PSA antibody (Ab2) label. The detection of PSA was also achieved via the liberated H2O2 when the GOx label reacted with glucose. The results demonstrated the possibility of this paper based sensor for the detection of different analytes with wide linear range. The low cost and simplicity of this paper based sensor could be developed for "point-of-care" analysis and find wide application in different areas. © 2013 Published by Elsevier B.V.

  8. Crosslinked Polyamide

    DOEpatents

    Huang, Zhi H.; McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

    2002-06-04

    A crosslinked polyamide material and a process for preparing the crosslinked polyamide material are disclosed. The crosslinked polyamide material comprises a crosslinked chemical combination of (1) a polyamide of the formula: ##STR1## wherein n is between about 50 and 10,000, wherein each R is between 1 and 50 carbon atoms alone and is optionally substituted with heteroatoms, oxygen, nitrogen, sulfur, or phosphorus and combinations thereof, wherein multiple of the R are in vertically aligned spaced relationship along a backbone forming the polyamide, and wherein two or more of the R contain an amino group; and (2) a crosslinking agent containing at least two functional groups capable of reacting with the amino groups of the polyamide. In one embodiment of the invention, the crosslinking agent is an aliphatic or aromatic isocyanate compound having 2 or more --N.dbd.C.dbd.O groups. In another embodiment of the invention, the crosslinking agent is an aliphatic aldehyde or aromatic aldehyde compound having 2 or more --CHO groups. In still another embodiment of the invention, the crosslinking agent is selected from a phosphine having the general formula (A).sub.2 P(B) and mixtures thereof, wherein A is hydroxyalkyl, and B is hydroxyalkyl, alkyl, or aryl. In yet another embodiment of the invention, the crosslinking agent is selected from the group consisting of epoxy resins having more than one epoxide group per molecule.

  9. Effect of base sequence on the DNA cross-linking properties of pyrrolobenzodiazepine (PBD) dimers.

    PubMed

    Rahman, Khondaker M; James, Colin H; Thurston, David E

    2011-07-01

    Pyrrolo[2,1-c][1,4]benzodiazepine (PBD) dimers are synthetic sequence-selective DNA minor-groove cross-linking agents that possess two electrophilic imine moieties (or their equivalent) capable of forming covalent aminal linkages with guanine C2-NH(2) functionalities. The PBD dimer SJG-136, which has a C8-O-(CH(2))(3)-O-C8'' central linker joining the two PBD moieties, is currently undergoing phase II clinical trials and current research is focused on developing analogues of SJG-136 with different linker lengths and substitution patterns. Using a reversed-phase ion pair HPLC/MS method to evaluate interaction with oligonucleotides of varying length and sequence, we recently reported (JACS, 2009, 131, 13 756) that SJG-136 can form three different types of adducts: inter- and intrastrand cross-linked adducts, and mono-alkylated adducts. These studies have now been extended to include PBD dimers with a longer central linker (C8-O-(CH(2))(5)-O-C8'), demonstrating that the type and distribution of adducts appear to depend on (i) the length of the C8/C8'-linker connecting the two PBD units, (ii) the positioning of the two reactive guanine bases on the same or opposite strands, and (iii) their separation (i.e. the number of base pairs, usually ATs, between them). Based on these data, a set of rules are emerging that can be used to predict the DNA-interaction behaviour of a PBD dimer of particular C8-C8' linker length towards a given DNA sequence. These observations suggest that it may be possible to design PBD dimers to target specific DNA sequences.

  10. In situ-forming click-crosslinked gelatin based hydrogels for 3D culture of thymic epithelial cells.

    PubMed

    Truong, Vinh X; Hun, Michael L; Li, Fanyi; Chidgey, Ann P; Forsythe, John S

    2016-07-21

    Hydrogels prepared from naturally derived gelatin can provide a suitable environment for cell attachment and growth, making them favourable materials in tissue engineering. However, physically crosslinked gelatin hydrogels are not stable under physiological conditions while chemical crosslinking of gelatin by radical polymerization may be harmful to cells. In this study, we attached the norbornene functional group to gelatin, which was subsequently crosslinked with a polyethylene glycol (PEG) linker via the nitrile oxide-norbornene click reaction. The rapid crosslinking process allows the hydrogel to be formed within minutes of mixing the polymer solutions under physiological conditions, allowing the gels to be used as injectable materials. The hydrogels properties including mechanical strength, swelling and degradation, can be tuned by changing either the ratio of the reacting groups or the total concentration of the polymer precursors. Murine embryonic fibroblastic cells cultured in soft gels (2 wt% of gelatin and 1 wt% of PEG linker) demonstrated high cell viability as well as similar phenotypic profiles (PDGFRα and MTS15) to Matrigel cultures over 5 days. Thymic epithelial cell and fibroblast co-cultures produced epithelial colonies in these gels following 7 days incubation. These studies demonstrate that gelatin based hydrogels, prepared using "click" crosslinking, provide a robust cell culture platform with retained benefits of the gelatin material, and are therefore suitable for use in various tissue engineering applications.

  11. Chondroitin Sulfate-Based Biocompatible Crosslinker Restores Corneal Mechanics and Collagen Alignment.

    PubMed

    Wang, Xiaokun; Majumdar, Shoumyo; Ma, Garret; Sohn, Jeeyeon; Yiu, Samuel C; Stark, Walter; Al-Qarni, Awad; Edward, Deepak P; Elisseeff, Jennifer H

    2017-08-01

    To evaluate the crosslinking effect of functionalized chondroitin sulfate (CS) in an ex vivo rabbit cornea model. Chondroitin sulfate molecules were chemically modified with the N-hydroxysuccinimide (NHS) group. Enucleated rabbit eyes were crosslinked with 2, 5, or 10 mg/mL CS-NHS solution for 30 or 60 minutes. The CS-NHS penetration, corneal swelling ratio, Young's modulus, and ultrastructure of the crosslinked corneas were characterized. In addition, rabbit corneas were further treated with a collagenase-chondroitinase solution to create an ex vivo keratoconus (KC)-like model. The KC model corneas were crosslinked with a standard riboflavin-ultraviolet (UV) method or alternatively with CS-NHS. Corneal mechanics, ultrastructure, and keratocyte gene expression were evaluated after UV and CS-NHS crosslinking. CS-NHS effectively penetrated into the corneal stroma within 60 minutes of treatment initiation. CS-NHS crosslinking reduced the swelling ratio by 35%, increased Young's modulus by 20%, and increased collagen fibril diameter and density. CS-NHS crosslinking improved corneal mechanics of KC model corneas to levels comparable to those with UV crosslinking. Moreover, CS-NHS crosslinking demonstrated significant downregulation of proinflammatory gene expression of keratocytes, indicating a potential protective effect imparted by CS-NHS during crosslinking. Our results demonstrated that CS-NHS can reinforce normal and KC model corneal mechanics, and restore collagen density and alignment in KC model corneas without causing extensive keratocyte apoptosis and proinflammatory gene upregulation. Therefore, CS-NHS crosslinking can potentially provide an effective, safe, and biocompatible means of corneal reinforcement.

  12. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles.

    PubMed

    Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A

    2015-12-04

    Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries.

  13. N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters.

    PubMed

    Goerz, Oliver; Ritter, Helmut

    2014-01-01

    Isosorbide was esterified with acryloyl chloride and crotonic acid yielding isosorbide diacrylate (9a) and isosorbide dicrotonate (9b), which were reacted with benzaldehyde oxime in the presence of zinc(II) iodide and boron triflouride etherate as catalysts to obtain N-alkylated dinitrones 10a/b. Poly(isosorbide itaconite -co- succinate) 13 as a bio-based unsaturated polyester was cross-linked by a 1,3-dipolar cycloaddition with the received dinitrones 10a/b. The 1,3-dipolar cycloaddition led to a strong change of the mechanical properties which were investigated by rheological measurements. Nitrones derived from methyl acrylate (3a) and methyl crotonate (3b) were used as model systems and reacted with dimethyl itaconate to further characterize the 1,3-dipolaric cycloaddition.

  14. Gold nanoprobe-based non-crosslinking hybridization for molecular diagnostics.

    PubMed

    Larguinho, Miguel; Canto, Rafaela; Cordeiro, Milton; Pedrosa, Pedro; Fortuna, Andreia; Vinhas, Raquel; Baptista, Pedro V

    2015-01-01

    Non-crosslinking (NCL) approaches using DNA-modified gold nanoparticles for molecular detection constitute powerful tools with potential implications in clinical diagnostics and tailored medicine. From detection of pathogenic agents to identification of specific point mutations associated with health conditions, these methods have shown remarkable versatility and simplicity. Herein, the NCL hybridization assay is broken down to the fundamentals behind its assembly and detection principle. Gold nanoparticle synthesis and derivatization is addressed, emphasizing optimal size homogeneity and conditions for maximum surface coverage, with direct implications in downstream detection. The detection principle is discussed and the advantages and drawbacks of different NCL approaches are discussed. Finally, NCL-based applications for molecular detection of clinically relevant loci and potential integration into more complex biosensing platforms, projecting miniaturization and portability are addressed.

  15. A self-healable and highly stretchable supercapacitor based on a dual crosslinked polyelectrolyte

    PubMed Central

    Huang, Yan; Zhong, Ming; Huang, Yang; Zhu, Minshen; Pei, Zengxia; Wang, Zifeng; Xue, Qi; Xie, Xuming; Zhi, Chunyi

    2015-01-01

    Superior self-healability and stretchability are critical elements for the practical wide-scale adoption of personalized electronics such as portable and wearable energy storage devices. However, the low healing efficiency of self-healable supercapacitors and the small strain of stretchable supercapacitors are fundamentally limited by conventional polyvinyl alcohol-based acidic electrolytes, which are intrinsically neither self-healable nor highly stretchable. Here we report an electrolyte comprising polyacrylic acid dual crosslinked by hydrogen bonding and vinyl hybrid silica nanoparticles, which displays all superior functions and provides a solution to the intrinsic self-healability and high stretchability problems of a supercapacitor. Supercapacitors with this electrolyte are non-autonomic self-healable, retaining the capacitance completely even after 20 cycles of breaking/healing. These supercapacitors are stretched up to 600% strain with enhanced performance using a designed facile electrode fabrication procedure. PMID:26691661

  16. New design of shape memory polymers based on natural rubber crosslinked via oxa-Michael reaction.

    PubMed

    Lin, Tengfei; Ma, Siwei; Lu, Yang; Guo, Baochun

    2014-04-23

    Shape memory polymers (SMPs) based on natural rubber were fabricated by crosslinking epoxidized natural rubber with zinc diacrylate (ZDA) using the oxa-Michael reaction. These SMPs possessed excellent shape fixity and recovery. The glass transition largely accounted for the fixing of the SMPs temporary shape. Increasing the ZDA content allowed the trigger temperature (20-46 °C) and recovery time (14-33 s) of the SMPs to be continuously tuned. Nanosized silica (nanosilica) was incorporated into the neat polymers to further increase the flexibility and tune the recovery stress. The nanosilica-SMPs exhibited exceptionally high strength in a rubbery state (>20 MPa). The nanosilica-SMPs exhibited high transparency, making them suitable in visible heat-shrinkable tubes.

  17. A self-healable and highly stretchable supercapacitor based on a dual crosslinked polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Huang, Yan; Zhong, Ming; Huang, Yang; Zhu, Minshen; Pei, Zengxia; Wang, Zifeng; Xue, Qi; Xie, Xuming; Zhi, Chunyi

    2015-12-01

    Superior self-healability and stretchability are critical elements for the practical wide-scale adoption of personalized electronics such as portable and wearable energy storage devices. However, the low healing efficiency of self-healable supercapacitors and the small strain of stretchable supercapacitors are fundamentally limited by conventional polyvinyl alcohol-based acidic electrolytes, which are intrinsically neither self-healable nor highly stretchable. Here we report an electrolyte comprising polyacrylic acid dual crosslinked by hydrogen bonding and vinyl hybrid silica nanoparticles, which displays all superior functions and provides a solution to the intrinsic self-healability and high stretchability problems of a supercapacitor. Supercapacitors with this electrolyte are non-autonomic self-healable, retaining the capacitance completely even after 20 cycles of breaking/healing. These supercapacitors are stretched up to 600% strain with enhanced performance using a designed facile electrode fabrication procedure.

  18. Thermo- and photo-driven soft actuators based on crosslinked liquid crystalline polymers

    NASA Astrophysics Data System (ADS)

    Gu, Wei; Wei, Jia; Yu, Yanlei

    2016-09-01

    Crosslinked liquid crystalline polymers (CLCPs) are a type of promising material that possess both the order of liquid crystals and the properties of polymer networks. The anisotropic deformation of the CLCPs takes place when the mesogens experience order to disorder change in response to external stimuli; therefore, they can be utilized to fabricate smart actuators, which have potential applications in artificial muscles, micro-optomechanical systems, optics, and energy-harvesting fields. In this review the recent development of thermo- and photo-driven soft actuators based on the CLCPs are summarized. Project supported by the National Natural Science Foundation of China (Grant Nos. 21134003, 21273048, 51225304, and 51203023) and Shanghai Outstanding Academic Leader Program, China (Grant No. 15XD1500600).

  19. Design and preparation of novel polyarylene ether materials based on Diels-Alder reaction as the crosslinker for electrooptical modulators

    NASA Astrophysics Data System (ADS)

    Gao, Wu; Hou, Wenjun; Zhen, Zhen; Liu, Xinhou; Liu, Jialei; Fedorchuk, A. A.; Czaja, P.

    2016-07-01

    Novel crosslinkable organic linear electro-optical (EO) material based on polyarylene ether as the main chain host polymer was designed and prepared. The host polymer with rigid aromatic has demonstrated a good compatibility with the guest chromophore. Long side chain with anthracene ensured the crosslinkable reaction and appropriate glass transition temperature of the host polymer (55 °C). The EO r33 tensor coefficient for this novel EO material has been magnitude of 66 pm/V at 1310 nm and the excellent long term stability at 85 °C. These parameters permit to consider their application in fabrication of organic electro optical devices. The semi-empirical and DFT quantum chemical simulations were performed for 4 principal chromophores to clarify a role of cross-linker in the enhancement of the ground state dipole moments and effective hyperpolarizabilities.

  20. Differential tandem mass spectrometry-based cross-linker: a new approach for high confidence in identifying protein cross-linking

    PubMed Central

    Chakrabarty, Jayanta K.; Naik, Aishwarya G.; Fessler, Michael B.; Munske, Gerhard R.; Chowdhury, Saiful M.

    2017-01-01

    Chemical cross-linking and mass spectrometry are now widely used to analyze large-scale protein-protein interactions. The major challenge in cross-linking approaches is the complexity of the mass spectrometric data. New approaches are required that can identify cross-linked peptides with high-confidence and establish a user-friendly analysis protocol for the biomedical scientific community. Here, we introduce a novel cross-linker that can be selectively cleaved in the gas phase using two differential tandem mass-spectrometric fragmentation methods, such as collision-induced or electron transfer dissociation (CID and ETD). This technique produces two signature mass spectra of the same cross-linked peptide, thereby producing high confidence in identifying the sites of interaction. Further tandem mass spectrometry can also give additional confidence on the peptide sequences. We demonstrate a proof-of-concept for this method using standard peptides and proteins. Peptides and proteins were cross-linked and their fragmentation characteristics were analyzed using CID and ETD tandem mass spectrometry. Two sequential cleavages unambiguously identified cross-linked peptides. In addition, the labeling efficiency of the new cross-linker was evaluated in macrophage immune cells after stimulation with the microbial ligand lipopolysaccharide and subsequent pulldown experiments with biotin-avidin affinity chromatography. We believe this strategy will help advance insights into the structural biology and systems biology of cell signaling. PMID:27649375

  1. Photochemical cross-linking for collagen-based scaffolds: a study on optical properties, mechanical properties, stability, and hematocompatibility.

    PubMed

    Chan, B P; Hui, T Y; Chan, O C M; So, K-F; Lu, W; Cheung, K M C; Salomatina, E; Yaroslavsky, A

    2007-01-01

    Collagen presents an attractive biomaterial for tissue engineering because of its excellent biocompatibility and negligible immunogenicity. However, some intrinsic features related to the mechanical stability and thrombogenicity limit its applications in orthopedic and vascular tissue engineering. Photochemical cross-linking is an emerging technique able to stabilize tissue grafts and improve the physicochemical properties of collagen-based structures. However, other important properties of collagen-based structures and the effect of processing parameters on these properties have not been explored. In this study, we aim to investigate the dose dependence of tensile and swelling properties on two parameters, namely, laser energy fluence and rose Bengal photosensitizer concentration. We also study the compression properties using cyclic compression test, long-term stability using subcutaneous implantation, and hematocompatibility using platelets adhesion test, of cross-linked collagen structures. Moreover, because limited optical penetration in turbid media is the major obstacle for light-based techniques, we also characterize the optical properties, which partially determine the effective optical penetration depth in collagen gel samples, during photochemical cross-linking. Laser energy fluence and rose Bengal concentration are important parameters affecting the cross-linking efficiency, which was characterized as the mechanical and the swelling properties, in a dose-dependent manner. Under the experimental conditions in this study, the peak fluence was 12.5 J/cm2 and the minimal rose Bengal concentration for effective cross-linking was >0.00008% (0.786 micromol). Photochemical cross-linking also enhanced the compression strength and long-term stability of collagen structures without compromising the tissue compatibility. Furthermore, photochemical cross-linking reduced platelet adhesion and abolished fibrin mesh formation, thereby improving the hematocompatibility

  2. Long-term durability of HT-PEM fuel cells based on thermally cross-linked polybenzimidazole

    NASA Astrophysics Data System (ADS)

    Søndergaard, Tonny; Cleemann, Lars Nilausen; Becker, Hans; Aili, David; Steenberg, Thomas; Hjuler, Hans Aage; Seerup, Larisa; Li, Qingfeng; Jensen, Jens Oluf

    2017-02-01

    Long-term durability of high temperature polymer electrolyte membrane fuel cells based on thermally cross-linked polybenzimidazole membranes was studied and compared with reference membranes based on linear polybenzimidazole. The test was conducted at 160 °C under constant load currents of 200 mA cm-2 for periods of 1000, 4400, and 13,000 h. Extensive beginning-of-life (BoL) and end-of-test (EoT) characterisation was carried out, and disturbance of the steady state operated cells was minimised by limiting in-line diagnostics to the low-invasive technique of electrochemical impedance spectroscopy (EIS). Up until the operating time of 9200 h, the cell equipped with the cross-linked membrane showed an average degradation rate of 0.5 μV h-1, compared to 2.6 μV h-1 for the reference membrane, though parallel tests for a shorter period of time showed deviations, likely due to malfunctioning contact between layers or cell components. For the full test period of 13,000 h, the average voltage decay rate was about 1.4 and 4.6 μV h-1 for cells equipped with cross-linked and linear polybenzimidazole membranes, respectively. EIS and post-test analysis revealed that the cross-linked membrane showed better stability in terms of area specific resistance due to improved acid retention characteristics.

  3. Light-Switchable Self-Healing Hydrogel Based on Host-Guest Macro-Crosslinking.

    PubMed

    Yang, Qiaofeng; Wang, Ping; Zhao, Chuanzhuang; Wang, Wenqin; Yang, Jingfa; Liu, Qiao

    2017-03-01

    A self-healing hydrogel is prepared by crosslinking acrylamide with a host-guest macro-crosslinker assembled from poly(β-cyclodextrin) nanogel and azobenzeneacrylamide. The photoisomerizable azobenzene moiety can change its binding affinity with β-cyclodextrin, therefore the crosslinking density and rheology property of the hydrogel can be tuned with light stimulus. The hydrogel can repair its wound autonomously through the dynamic host-guest interaction. In addition, the wounded hydrogel will lose its ability of self-healing when exposed to ultraviolet light, and the self-healing behavior can be recovered upon the irradiation of visible light. The utilizing of host-guest macro-crosslinking approach manifests the as-prepared hydrogel reversible and light-switchable self-healing property, which would broaden the potential applications of self-healing polymers.

  4. Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

    NASA Astrophysics Data System (ADS)

    Abd El-Rehim, H. A.

    2005-10-01

    Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers.

  5. Maximizing Deoxyribonucleic Acid Yield from Dried Blood Spots

    PubMed Central

    Lane, Julie A.; Noble, Janelle A.

    2010-01-01

    Background One source of deoxyribonucleic acid (DNA) for genetic studies is the utilization of dried blood spots stored on paper cards (Guthrie cards) collected shortly after birth. These cards represent an important source of material for epidemiologic and population-based genetic studies. Extraction of DNA from these cards can lead to variable amounts of recovered DNA. We report here results of our efforts to maximize yield from this valuable, but nonrenewable, resource. Method Commercial methods of DNA extraction from blood cards were used, and protocol modifications were introduced that enhanced DNA yield. Results Use of a commercial solvent prior to DNA extraction steps gave greater yields than extraction without the solvent. Modification of the elution step by use of prewarmed extraction buffer and a soaking step at an elevated temperature increased yield by 6- to 10-fold. Conclusions The modified DNA extraction method yielded as much as 660 ng of DNA from a single 5-mm-diameter punch of a blood spot card. The DNA performed well in downstream, polymerase chain reaction-based applications. PMID:20307384

  6. Positive tone cross-linked resists based on photoacid inhibition of cross linking

    NASA Astrophysics Data System (ADS)

    Lawson, Richard A.; Chun, Jun Sung; Neisser, Mark; Tolbert, Laren M.; Henderson, Clifford L.

    2014-03-01

    A resist imaging design that utilizes photoacid inhibition of cationic polymerization and cross-linking during a postexposure bake step has been studied. The key to the design approach is the use of two different polymerization catalysts/initiators: (1) a photoacid produced from a photoacid generator (PAG) upon exposure of the resist that can result in polymerization and cross-linking of the resist matrix and (2) a thermal cross-linking catalyst (TCC) designed to thermally catalyze epoxide-phenol cross-linking. The TCC can be chosen from a variety of compounds such as triphenylphosphine (TPP) or imidazole. When only one of these catalysts (e.g TPP or photoacid) is present in an epoxide and phenol containing resist matrix, it will individually catalyze cross-linking. When they are present together, they effectively quench one another and little to no cross-linking occurs. This approach can be used to switch the tone of a resist from negative (photoacid catalyzed) to positive (TCC catalyzed and photoacid inhibited). The effect of the ratio of TCC:PAG was examined and the optimal ratio for positive tone behavior was determined. Resist contrast can be modified by optimization of epoxide:phenol ratio in the formulation. Dual tone behavior with positive tone at low dose and negative tone at higher doses can be observed in certain formulation conditions. Initial EUV patterning shows poor results, but the source of the poor imaging is not yet understood.

  7. Stable Bioactive Enzyme-Containing Multilayer Films Based on Covalent Cross-Linking from Mussel-Inspired Adhesives.

    PubMed

    Longo, Johan; Garnier, Tony; Mateescu, Mihaela; Ponzio, Florian; Schaaf, Pierre; Jierry, Loïc; Ball, Vincent

    2015-11-17

    The use of immobilized enzymes is mandatory for the easy separation of the enzyme, the unreacted substrates, and the obtained products to allow repeated enzymatic assays without cumbersome purification steps. The immobilization procedure is however critical to obtain a high fraction of active enzyme. In this article, we present an enzyme immobilization strategy based on a catechol functionalized alginate. We demonstrate that alkaline phosphatase (ALP) remains active in multilayered films made with alginate modified with catechol moieties (AlgCat) for long duration, that is, up to 7 weeks, provided the multilayered architecture is cross-linked with sodium periodate. This cross-linking reaction allows to create covalent bonds between the amino groups of ALP and the quinone group carried by the modified alginate. In the absence of cross-linking, the enzymatic activity is rapidly lost and this reduction is mainly due to enzyme desorption. We also show that NaIO4 cross-linked (AlgCat-Alp)n films can be freeze-dried and reused at least 3 weeks later without lost in enzymatic activity.

  8. Physical Cross-Linking Starch-Based Zwitterionic Hydrogel Exhibiting Excellent Biocompatibility, Protein Resistance, and Biodegradability.

    PubMed

    Ye, Lei; Zhang, Yabin; Wang, Qiangsong; Zhou, Xin; Yang, Boguang; Ji, Feng; Dong, Dianyu; Gao, Lina; Cui, Yuanlu; Yao, Fanglian

    2016-06-22

    In this work, a novel starch-based zwitterionic copolymer, starch-graft-poly(sulfobetaine methacrylate) (ST-g-PSBMA), was synthesized via Atom Transfer Radical Polymerization. Starch, which formed the main chain, can be degraded completely in vivo, and the pendent segments of PSBMA endowed the copolymer with excellent protein resistance properties. This ST-g-PSBMA copolymer could self-assemble into a physical hydrogel in normal saline, and studies of the formation mechanism indicated that the generation of the physical hydrogel was driven by electrostatic interactions between PSBMA segments. The obtained hydrogels were subjected to detailed analysis by scanning electron microscopy, swelling ratio, protein resistance, and rheology tests. Toxicity and hemolysis analysis demonstrated that the ST-g-PSBMA hydrogels possess excellent biocompatibility and hemocompatibility. Moreover, the cytokine secretion assays (IL-6, TNF-α, and NO) confirmed that ST-g-PSBMA hydrogels had low potential to trigger the activation of macrophages and were suitable for in vivo biomedical applications. On the basis of these in vitro results, the ST-g-PSBMA hydrogels were implanted in SD rats. The tissue responses to hydrogel implantation and the hydrogel degradation in vivo were determined by histological analysis (Hematoxylin and eosin, Van Gieson, and Masson's Trichrome stains). The results presented in this study demonstrate that the physical cross-linking, starch-based zwitterionic hydrogels possess excellent protein resistance, low macrophage-activation properties, and good biocompatibility, and they are a promising candidate for an in vivo biomedical application platform.

  9. Cyclodextrin/dextran based hydrogels prepared by cross-linking with sodium trimetaphosphate.

    PubMed

    Wintgens, Véronique; Lorthioir, Cédric; Dubot, Pierre; Sébille, Bernard; Amiel, Catherine

    2015-11-05

    Novel βCD-based hydrogels have been synthesized using sodium trimetaphosphate (STMP) as non-toxic reagent. Straightforward mixing of βCD with dextran and STMP in basic aqueous media led to hydrogels incorporating dextran chains, phosphate groups and βCD units. The hydrogels have been characterized by swelling measurements, XPS and (31)P NMR. The swelling ratio was correlated to the content in phosphated groups, which give a polyelectrolyte character to these hydrogels. The significant rise of the swelling ratio with the βCD content increase has been attributed to a decrease of the number of phosphate-based crosslinks, the βCD units playing the role of dangling ends in the tridimensional network. Their loading capacity and their release properties have been investigated for methylene blue and benzophenone in order to demonstrate their potentiality for drug delivery. Through different interaction mechanisms, electrostatic and inclusion complex interactions, these compounds are loaded with different efficiencies. The release involves deswelling, diffusion mechanisms and partition equilibrium.

  10. Investigation of Biological Adhesives and Polyurea Crosslinked Silica-Based Aerogels

    NASA Astrophysics Data System (ADS)

    Lyons, Laura; Cauble, Meagan; Cole, Judith; Sabri, Firouzeh

    2009-11-01

    One of the key steps towards developing new technology for nerve repair is to look at the interaction mechanism and strength of biological components with the material under investigation. The existing technology for peripheral nerve repair relies on suturing techniques for attaching and immobilization of the implant. It is also limited to connecting two nerve components only, through a cylindrical-shaped unit which we will refer to as 1-D. The focus of our work is to develop an aerogel-based printed circuit board (PCB) system for precise guidance of multiple (n-D) neuronal components, simultaneously. Here we report on the adhesion strength of sciatic nerve segments removed from cadaver Sprague Dawley rats and the surface of treated and untreated polyurea cross-linked silica-based aerogels. The adhesion strength of the nerve to the aerogel surface was studied under varying environmental conditions as well as surface coating types. The coatings tested were basement membrane extract (BME), Cell Tak, and the combination. Since the mechanism of adhesion to cells and other surfaces is different and non-competing for BME and Cell Tak it is expected that a stronger adhesion should be accomplished by combining these two adhesives. The effect of temperature, nerve elasticity, and ionic concentration on the strength of adhesion was investigated also and will be reported.

  11. A Crosslinked HA-Based Hydrogel Ameliorates Dry Eye Symptoms in Dogs

    PubMed Central

    Williams, David L.; Mann, Brenda K.

    2013-01-01

    Keratoconjunctivitis sicca, commonly referred to as dry eye or KCS, can affect both humans and dogs. The standard of care in treating KCS typically includes daily administration of eye drops to either stimulate tear production or to hydrate and lubricate the corneal surface. Lubricating eye drops are often applied four to six times daily for the life of the patient. In order to reduce this dosing regimen yet still provides sufficient hydration and lubrication, we have developed a crosslinked hydrogel based on a modified, thiolated hyaluronic acid (HA), xCMHA-S. This xCMHA-S gel was found to have different viscosity and rheologic behavior than solutions of noncrosslinked HA. The gel was also able to increase tear breakup time in rabbits, indicating a stabilization of the tear film. Further, in a preliminary clinical study of dogs with KCS, the gel significantly reduced the symptoms associated with KCS within two weeks while only being applied twice daily. The reduction of symptoms combined with the low dosing regimen indicates that this gel may lead to both improved patient health and owner compliance in applying the treatment. PMID:23840213

  12. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles

    PubMed Central

    Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A.

    2015-01-01

    Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries. PMID:26634644

  13. A Highly Elastic and Rapidly Crosslinkable Elastin-Like Polypeptide-Based Hydrogel for Biomedical Applications

    PubMed Central

    Zhang, Yi-Nan; Avery, Reginald K.; Vallmajo-Martin, Queralt; Assmann, Alexander; Vegh, Andrea; Memic, Adnan; Olsen, Bradley D.

    2015-01-01

    Elastin-like polypeptides (ELPs) are promising for biomedical applications due to their unique thermoresponsive and elastic properties. ELP-based hydrogels have been produced through chemical and enzymatic crosslinking or photocrosslinking of modified ELPs. Herein, a photocrosslinked ELP gel using only canonical amino acids is presented. The inclusion of thiols from a pair of cysteine residues in the ELP sequence allows disulfide bond formation upon exposure to UV light, leading to the formation of a highly elastic hydrogel. The physical properties of the resulting hydrogel such as mechanical properties and swelling behavior can be easily tuned by controlling ELP concentrations. The biocompatibility of the engineered ELP hydrogels is shown in vitro as well as corroborated in vivo with subcutaneous implantation of hydrogels in rats. ELP constructs demonstrate long-term structural stability in vivo, and early and progressive host integration with no immune response, suggesting their potential for supporting wound repair. Ultimately, functionalized ELPs demonstrate the ability to function as an in vivo hemostatic material over bleeding wounds. PMID:26523134

  14. Synthesis and characterization of psyllium-NVP based drug delivery system through radiation crosslinking polymerization

    NASA Astrophysics Data System (ADS)

    Singh, Baljit; Kumar, S.

    2008-08-01

    In order to develop the hydrogels meant for the drug delivery, we have prepared psyllium- N-vinylpyrrolidone (NVP) based hydrogels by radiation induced crosslinking. Polymers were characterized with SEMs, FTIR and swelling studies. Swelling of the hydrogels was studied as a function of monomer concentration, total radiation dose, temperature, pH and [NaCl] of the swelling medium. The swelling kinetics of the hydrogels and release dynamics of anticancer model drug (5-fluorouracil) from the hydrogels have been carried out for the evaluation of swelling and drug release mechanism. It has been observed that diffusion exponent ' n' have 0.8, 0.9, 0.8 and gel characteristics constant ' k' have 9.22 × 10 -3, 2.06 × 10 -3, 11.72 × 10 -3 values for the release of drug from the drug loaded hydrogels in distilled water, pH 2.2 buffer and pH 7.4 buffer, respectively. The present study shows that the release of drug from the hydrogels occurred through Non-Fickian diffusion mechanism.

  15. Ultrasonic elasticity determination of 45S5 Bioglass(®)-based scaffolds: influence of polymer coating and crosslinking treatment.

    PubMed

    Li, Wei; Pastrama, Maria-Ioana; Ding, Yaping; Zheng, Kai; Hellmich, Christian; Boccaccini, Aldo R

    2014-12-01

    Highly porous 45S5 Bioglass(®)-based scaffolds with interconnected pore structure are promising candidates for bone tissue engineering due to their bioactivity, biocompatibility, osteogenic and angiogenic effects. In the present study, to ensure the mechanical competence of the 45S5 Bioglass(®)-based scaffolds, their stiffness was adjusted by applying polymer coatings and further crosslinking treatment. A non-destructive ultrasonic technique was used to determine the stiffness of the scaffolds. The stiffness of uncoated scaffolds was shown to increase by applying polymer coatings, and a further increase was achieved by crosslinking the used polymer coatings. All uncoated and polymer-coated scaffolds were confirmed to exhibit stiffness values in the range of reported values in the literature for cancellous bone. A statistical evaluation of combined multiscale ultrasound-nanoindentation measurements indicated that the stiffness of the coated scaffold is directly dependent on the stiffness of the polymer coating.

  16. Data of thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid as crosslinking agent

    PubMed Central

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-01-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: “Biodegradable and non-retrogradable eco-films based on starch–glycerol with citric acid as crosslinking agent” González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature. PMID:27158645

  17. Data of thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid as crosslinking agent.

    PubMed

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-06-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: "Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent" González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature.

  18. 21 CFR 528.1070 - Bc6 recombinant deoxyribonucleic acid construct.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... ANIMALS § 528.1070 Bc6 recombinant deoxyribonucleic acid construct. (a) Specifications and indications for use. Five copies of a human Bc6 recombinant deoxyribonucleic acid (rDNA) construct located at the GTC... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Bc6 recombinant deoxyribonucleic acid...

  19. A novel crosslinking method for improved tear resistance and biocompatibility of tissue based biomaterials.

    PubMed

    Tam, Hobey; Zhang, Will; Feaver, Kristen R; Parchment, Nathaniel; Sacks, Michael S; Vyavahare, Naren

    2015-10-01

    Over 300,000 heart valve replacements are performed annually to replace stenotic and regurgitant heart valves. Bioprosthetic heart valves (BHVs), derived from glutaraldehyde crosslinked (GLUT) porcine aortic valve leaflets or bovine pericardium are often used. However, valve failure can occur within 12-15 years due to calcification and/or progressive degeneration. In this study, we have developed a novel fabrication method that utilizes carbodiimide, neomycin trisulfate, and pentagalloyl glucose crosslinking chemistry (TRI) to better stabilize the extracellular matrix of porcine aortic valve leaflets. We demonstrate that TRI treated leaflets show similar biomechanics to GLUT crosslinked leaflets. TRI treated leaflets had better resistance to enzymatic degradation in vitro and demonstrated better tearing toughness after challenged with enzymatic degradation. When implanted subcutaneously in rats for up to 90 days, GLUT control leaflets calcified heavily while TRI treated leaflets resisted calcification, retained more ECM components, and showed better biocompatibility.

  20. A novel crosslinking method for improved tear resistance and biocompatibility of tissue based biomaterial

    PubMed Central

    Tam, Hobey; Zhang, Will; Feaver, Kristen R.; Parchment, Nathaniel; Sacks, Michael S.; Vyavahare, Naren

    2015-01-01

    Over 300,000 heart valve replacements are performed annually to replace stenotic and regurgitant heart valves. Bioprosthetic heart valves (BHVs), derived from glutaraldehyde crosslinked (GLUT) porcine aortic valve leaflets or bovine pericardium are often used. However, valve failure can occur within 12–15 years due to calcification and/or progressive degeneration. In this study, we have developed a novel fabrication method that utilizes carbodiimide, neomycin trisulfate, and pentagalloyl glucose crosslinking chemistry (TRI) to better stabilize the extracellular matrix of porcine aortic valve leaflets. We demonstrate that TRI treated leaflets show similar biomechanics to GLUT crosslinked leaflets. TRI treated leaflets had better resistance to enzymatic degradation in vitro and demonstrated better tearing toughness after challenged with enzymatic degradation. When implanted subcutaneously in rats for up to 90 days, GLUT control leaflets calcified heavily while TRI treated leaflets resisted calcification, retained more ECM components, and showed better biocompatibility. PMID:26196535

  1. Interactions of carcinogens with DNA (deoxyribonucleic acid)

    SciTech Connect

    Broyde, S.; Shapiro, R.

    1989-10-01

    The principal goal of this research has been the determination of the conformational changes produced in DNA by the covalent binding of a carcinogenic aromatic amine, and the correlation of these changes with the mutations and carcinogenic effects initiated by the same substances. To this end, we have devised new synthetic methods for the preparation of oligonucleotides modified by derivatives af 4-aminobiphenyl and aniline. We have also performed potential energy minimization studies on the above substances and on single and double stranded DNA fragments bearing the above amines as well as acetylaminofluorene, aminofluorene, aminopyrene and the antibiotic mitomycin. Our computations have been carried out on DOE supercomputers using our program, DUPLEX. We have defined a number of novel structures for these modified DNAs, including Hoogsteen, wedge'' (see below) denatured, cross-linked and intercalated forms. Some suggestions have been made about the relation of these forms to mutagenesis. 7 refs.

  2. Spectroscopic evaluation of polyurea crosslinked aerogels, as a substitute for RTV-based chromatic calibration targets for spacecraft

    NASA Astrophysics Data System (ADS)

    Sabri, F.; Leventis, N.; Hoskins, J.; Schuerger, A. C.; Sinden-Redding, M.; Britt, D.; Duran, R. A.

    2011-02-01

    Room temperature vulcanizing (RTV)-based components have been used on Mars Pathfinder, the Mars rovers, Spirit and Opportunity, as well as the Phoenix Lander as a support matrix for pigmented panoramic camera calibration targets. RTV 655 has demonstrated superiority to other polymers due to its unique range of material properties namely mechanical stability between -115 and 204 °C and UV radiation tolerance. As a result, it has been the number one choice for many space-related missions. However, due to the high mass density and the natural tendency for electrostatic charging RTV materials have caused complications by attracting and retaining dust particles (Sabri et al., 2008). In the current project we have investigated the relevant properties of polymer-reinforced (crosslinked) silica aerogels with the objective of substituting RTV-based calibration targets with an aerogel based design. The lightweight, mechanical strength, ability to accept color pigments, and extremely low dust capture makes polyurea crosslinked aerogels a strong candidate as a chromatic standard for extraterrestrial missions. For this purpose, the reflection spectra, gravimetric analysis, and low temperature response of metal oxide pigmented, polyurea crosslinked silica aerogels have been investigated and reported here.

  3. Ribonucleotides Covalently Linked to Deoxyribonucleic Acid in T4 Bacteriophage

    PubMed Central

    Speyer, J. F.; Chao, J.; Chao, L.

    1972-01-01

    Bacteriophage T4 was grown in the presence of labeled uridine. The deoxyribonucleic acid (DNA) of the phage was shown to contain covalently attached ribonucleotides. The label appears not to be internal in the DNA strands. Presumably, it is at the ends of the DNA strands and this may be related to DNA initiation. PMID:4564585

  4. Cytocompatible in situ cross-linking of degradable LbL films based on thiol-exchange reaction.

    PubMed

    Yang, Sung Ho; Choi, Jinsu; Palanikumar, L; Choi, Eun Seong; Lee, Juno; Kim, Juan; Choi, Insung S; Ryu, Ja-Hyoung

    2015-08-01

    Formation of both mechanically durable and programmably degradable layer-by-layer (LbL) films in a biocompatible fashion has potential applications in cell therapy, tissue engineering, and drug-delivery systems, where the films are interfaced with living cells. In this work, we developed a simple but versatile method for generating in situ cross-linked and responsively degradable LbL films, based on the thiol-exchange reaction, under highly cytocompatible conditions (aqueous solution at pH 7.4 and room temperature). The cytocompatibility of the processes was confirmed by coating individual yeast cells with the cross-linked LbL films and breaking the films on demand, while maintaining the cell viability. In addition, the processes were applied to the controlled release of an anticancer drug in the HeLa cells.

  5. Evaluation of gentamicin and lidocaine release profile from gum acacia-crosslinked-poly(2-hydroxyethylmethacrylate)-carbopol based hydrogels.

    PubMed

    Singh, Baljit; Dhiman, Abhishek

    2017-01-27

    In this manuscript an attempt has been made to incorporate both, antibiotic agent 'gentamicin' and pain relieving agent 'lidocaine' into the gum acacia-poly(2-hydroxyethylmethacrylate)-carbopol based hydrogel for wound dressing application. Drug release, gel strength, network parameter, antimicrobial activity and biodegradation properties of hydrogel have been evaluated. Porous microstructure of the hydrogel was observed in cryo-SEM images. The hydrogel showed mesh size 37.29 nm, cross-link density 2.19× 10-5 mol/cm3, molecular weight between two cross-links 60.25× 10-3 g/mol and gel strength 0.625±0.112 N in simulated wound fluid. The hydrogels were evaluated as a drug carrier for model drugs gentamicin and lidocaine. The release of these drugs occurred through Fickian diffusion mechanism and release profile of the drugs was best fitted in first order kinetic model.

  6. Plasticization and crosslinking effects of acetone-formaldehyde and tannin resins on wheat protein-based natural polymers.

    PubMed

    Zhang, Xiaoqing; Do, My Dieu

    2009-07-06

    Efficient plasticization and sufficient crosslinking were achieved by using an acetone-formaldehyde (AF) resin as an additive in the thermal processing of wheat protein-based natural polymers. The mobile AF resin and its strong intermolecular interactions with a wheat protein matrix produced sufficient flexibility for the plastics, while the covalent bonds formed between AF and the protein chains also caused the water-soluble resin to be retained in the materials under wet conditions. The mechanical properties of the materials were also enhanced as an additional benefit due to the formation of crosslinked networks through the polymer matrix. Tensile strength was further enhanced when using AF in conjunction with tannin resin (AFTR) in the systems as rigid aromatic structures were formed in the crosslinking segments. Different components in wheat proteins (WPs) or wheat gluten (WG) (e.g., proteins, residual starch and lipids) displayed different capabilities in interaction and reaction with the AFTR additives, and thus resulted in different performances when the ratio of these components varied in the materials. The application of the AFTR additives provides a feasible methodology to thermally process wheat protein-based natural polymers with improved mechanical performance and water-resistant properties.

  7. Divinyl sulfone cross-linked cyclodextrin-based polymeric materials: synthesis and applications as sorbents and encapsulating agents.

    PubMed

    Morales-Sanfrutos, Julia; Lopez-Jaramillo, Francisco Javier; Elremaily, Mahmoud A A; Hernández-Mateo, Fernando; Santoyo-Gonzalez, Francisco

    2015-02-19

    The aim of this study was to evaluate the crosslinking abilities of divinyl sulfone (DVS) for the preparation of novel water-insoluble cyclodextrin-based polymers (CDPs) capable of forming inclusion complexes with different guest molecules. Reaction of DVS with native α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and/or starch generates a variety of homo- and hetero-CDPs with different degrees of crosslinking as a function of the reactants' stoichiometric ratio. The novel materials were characterized by powder X-ray diffraction, electron microscopy and for their sorption of phenol and 4-nitrophenol. They were further evaluated as sorbents with phenolic pollutants (bisphenol A and β-naphthol) and bioactive compounds (the hormone progesterone and curcumin). Data obtained from the inclusion experiments show that the degree of cross-linking has a minor influence on the yield of inclusion complex formation and highlight the important role of the CDs, supporting a sorption process based on the formation of inclusion complexes. In general, the inclusion processes are better described by a Freundlich isotherm although an important number of them can also be fitted to the Langmuir isotherm with R2 ≥ 0.9, suggesting a sorption onto a monolayer of homogeneous sites.

  8. Development of horseradish peroxidase-based cross-linked enzyme aggregates and their environmental exploitation for bioremediation purposes.

    PubMed

    Bilal, Muhammad; Iqbal, Hafiz M N; Hu, Hongbo; Wang, Wei; Zhang, Xuehong

    2017-03-01

    In the present study, horseradish peroxidase (HRP), in-house isolated crude cocktail enzyme, from Armoracia rusticana was cross-linked using a new type of cross-linking agent, i.e., ethylene glycol-bis [succinic acid N-hydroxysuccinimide, (EG-NHS)], which is mild in nature as compared to the glutaraldehyde (GA). The HRP-immobilized cross-linked enzyme aggregates (HRP-CLEAs) were developed using a wider range of EG-NHS and notably no adverse effect was observed. In a comparative evaluation, in the case of EG-NHS, a high-level stability in the residual activity was recorded, whereas a sharp decrease was observed in the case of glutaraldehyde. Following initial cross-linker evaluation, the HRP-CLEAs were tested to investigate their bio-catalytic efficacy for bioremediation purposes using a newly developed packed bed reactor system (PBRS). A maximal of 94.26% degradation of textile-based methyl orange dye was recorded within the shortest time frame, following 91.73% degradation of basic red 9, 84.35% degradation of indigo, 81.47% degradation of Rhodamin B, and 73.6% degradation of Rhodamine 6G, respectively, under the same working environment. Notably, the HRP-CLEAs retained almost 60% of its original activity after methyl orange dye degradation in seven consecutive cycles using PBRS. Furthermore, after HRP-CLEAs-mediated treatment in the PBRS, a significant toxicity reduction in the dye samples was recorded as compared to their pristine counterparts. In conclusion, the results suggest that the newly developed HRP-CLEAs have a great potential for industrial exploitation, to tackle numerous industrial dye-based emergent pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. New physically and chemically crosslinked hyaluronate (HA)-based hydrogels for cartilage repair.

    PubMed

    Huin-Amargier, Cécile; Marchal, Philippe; Payan, Elisabeth; Netter, Patrick; Dellacherie, Edith

    2006-02-01

    When dissolved in aqueous solutions, sodium hyaluronate substituted with low amounts of alkyl chains [amphiphilic hyaluronate (HA)] can give rise to hydrogels thanks to intermolecular reversible hydrophobic interactions, leading to a three-dimensional (3D) network. Such hydrogels possess shear-thinning properties and can thus be injected in cartilage defect to promote chondrocyte proliferation and cartilage repair. However, these hydrogels are only physically crosslinked and can progressively loose their 3D structure when they are in contact with aqueous fluids. To overcome this drawback, HA derivatives substituted with dodecyl chains were chemically crosslinked by a difunctional reagent, tetraethylene glycol ditosylate (TEG-diOTs). To preserve the shear-thinning properties of amphiphilic HA, small amounts of TEG-diOTs were used so as to obtain a low chemical crosslinking ratio. After optimization of the synthesis parameters, aqueous solutions of the HA derivatives, crosslinked both physically and chemically, were obtained, with rheological properties improved compared to the amphiphilic polymers. As the hydrogels are aimed to cartilage repair, they were sterilized by wet heating; the effect of this treatment on the polymer characteristics was analyzed by different techniques. A similar study was carried out on HA derivatives stored under conditions mimicking physiological ones. (c) 2005 Wiley Periodicals, Inc.

  10. Development and characterization of films based on chemically cross-linked gliadins.

    PubMed

    Hernández-Muñoz, Pilar; Kanavouras, Antonis; Lagaron, José M; Gavara, Rafael

    2005-10-19

    The aim of the present work has been to study the possibility of obtaining modified gliadin films with improved water resistance and mechanical properties by means of promoting intermolecular covalent bonds between polypeptide chains. Prior to casting films, formaldehyde, glutaraldehyde, and glyoxal were used to cross-link proteins at concentrations ranging from 1% to 4% (grams per 100 g of protein). Mechanical properties (tensile strength and elongation at break), water vapor permeability, moisture sorption isotherms, and optical properties of the films produced were evaluated as a function of the cross-linker used. Experimental results showed that some properties of gliadin films were considerably modified. Cross-linking improved the water resistance of films, avoiding their disintegration. Their water barrier properties were also enhanced, but their moisture sorption properties remained unchanged. Formaldehyde imparted greater mechanical strength to films than glutaraldehyde or glyoxal, increasing tensile strength values 10-fold. Addition of the cross-linkers at concentrations in excess of 2.5% did not further improve the mechanical or barrier properties. However, modification with glutaraldehyde or glyoxal imparted an increasingly yellowish tint to the films.

  11. Biodegradable Chitosan-Based Ambroxol Hydrochloride Microspheres: Effect of Cross-Linking Agents

    PubMed Central

    Gangurde, HH; Chavan, NV; Mundada, AS; Derle, DV; Tamizharasi, S

    2011-01-01

    The objective of this study was to investigate the influence of type of cross-linking method used on the properties of ambroxol hydrochloride microspheres such as encapsulation efficiency, particle size, and drug release. Microspheres were prepared by solvent evaporation technique using chitosan as a matrix-forming agent and cross-linked using formaldehyde and heat treatment. Morphological and physicochemical properties of microspheres were then investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR) spectroscopy. The cross-linking of chitosan takes place at the free amino group because of formation of imine bond as evidenced by FTIR. The DSC, XRD, and FTIR analysis showed that chitosan microspheres cross linked by heating were superior in properties and performance as compared to the microspheres cross-linked using formaldehyde. SEM results revealed that heat-treated microspheres were spherical, discrete having smooth, and porous structure. The particle size and encapsulation efficiencies of the prepared chitosan microspheres ranged between 10.83–24.11 μm and 39.73μ80.56%, respectively. The drug release was extended up to 12 h, and the kinetics of the drug release was obeying Higuchi kinetic proving diffusion-controlled drug release. PMID:21607049

  12. Preparation of novel ferrocene-based shell cross-linked thermoresponsive hybrid micelles with antitumor efficacy.

    PubMed

    Wei, Hua; Quan, Chang-Yun; Chang, Cong; Zhang, Xian-Zheng; Zhuo, Ren-Xi

    2010-04-29

    The shell cross-linked (SCL) thermoresponsive hybrid poly(N-isopropylacrylamide-co-aminoethyl methacrylate)-b-polymethyl methacrylate (P(NIPAAm-co-AMA)-b-PMMA) micelle consisting of a cross-linked thermoresponsive hybrid shell and a hydrophobic core domain was fabricated via a two-step process: micellization of P(NIPAAm-co-AMA)-b-PMMA in aqueous solution followed by cross-linking of the hydrophilic shell layer via the amidation reaction between the amine groups of AMA units and the carboxylic acid functions of 1,1'-ferrocenedicarboxylic acid. The SCL micelle showed reversible dispersion/aggregation in response to the temperature cycles through the lower critical solution temperature (LCST) of the thermoresponsive hybrid shell at around 36 degrees C, observed by turbidity measurements and dynamic light scattering (DLS). Besides the usage as an inorganic difunctional cross-linker, the inorganic ferrocene segment further endowed the SCL hybrid micelle with the antitumor efficacy, namely, the resulting SCL micelle exhibited a remarkable cytotoxic effect for HeLa cells with a very low IC50. The results showed that the SCL hybrid micelle developed in this study could be potentially used as an antitumor agent, which is unique compared to the conventional tumor therapy by using the antitumor drug loaded in the micellar core.

  13. Highly robust hydrogels via a fast, simple and cytocompatible dual crosslinking-based process.

    PubMed

    Costa, Ana M S; Mano, João F

    2015-11-07

    A highly robust hydrogel device made from a single biopolymer formulation is reported. Owing to the presence of covalent and non-covalent crosslinks, these engineered systems were able to (i) sustain a compressive strength of ca. 20 MPa, (ii) quickly recover upon unloading, and (iii) encapsulate cells with high viability rates.

  14. Genetic Control of the Secondary Modification of Deoxyribonucleic Acid in Escherichia coli1

    PubMed Central

    Mamelak, Linda; Boyer, Herbert W.

    1970-01-01

    The wild-type restriction and modification alleles of Escherichia coli K-12 and B were found to have no measurable effect on the patterns of methylated bases in the deoxyribonucleic acid (DNA) of these strains. The genetic region controlling the methylation of cytosine in E. coli K-12 was mapped close to his, and the presence or absence of this gene in E. coli B or E. coli K had no effect on the restriction and modification properties of these strains. Thus, only a few of the methylated bases in the DNA of these strains are involved in host modification, and the biological role of the remainder remains obscure. PMID:4919756

  15. Stabilizing and destabilizing effects of arginine on deoxyribonucleic acid.

    PubMed

    Arakawa, Tsutomu; Hirano, Atsushi; Shiraki, Kentaro; Kita, Yoshiko; Koyama, A Hajime

    2010-03-01

    Aqueous arginine solution now finds a wide range of applications in biotechnology fields, including protein refolding, chromatography and virus inactivation. While progress has been made for mechanistic understanding of the effects of arginine on proteins, we have little understanding on how arginine inactivates viruses. One of the viral components is nucleic acid. We have examined the effects of arginine on the structure and thermal stability of calf thymus deoxyribonucleic acid (DNA) using circular dichroism (CD). Both NaCl and arginine reduced CD intensity. At low concentrations, arginine showed a stronger effect on CD intensity than NaCl. Both NaCl and arginine sharply increased the melting temperature at low concentrations (below 0.25 M). However, they had an opposite effect at higher concentrations. Above this concentration, NaCl gradually increased the melting temperature, leading to the onset melting temperature above 90 degrees C. On the other hand, the thermal stability in the presence of arginine reached a maximum at 0.2-0.5 M, after which further addition of arginine caused decreased melting temperature. It is most likely that the increased melting temperature at low concentration is due to electrostatic stabilization of DNA structure by both NaCl and arginine and that the opposite effects at higher salt concentration are due to salt-specific effects, i.e., stabilizing (salting-out) effects of NaCl and destabilizing (salting-in) effects of arginine. Solubility measurements of nucleic acid bases showed that arginine, but not NaCl, increases the solubilities of the bases, supporting their effects on DNA stability at higher concentration.

  16. Removing Cr(VI) from aqueous solutions using a functional ionic liquid-based cross-linked polymer.

    PubMed

    Gao, Hejun; Wang, Yun; Zheng, Liqiang

    2014-05-01

    A novel functional ionic liquid-based cross-linked polymer was synthesized from 1-aminoethyl-3-vinylimidazolium chloride hydrochloride and divinylbenzene. The physicochemical properties of the adsorbent were investigated using scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The adsorption capacity of the novel cross-linked polymer with respect to Cr(VI) was investigated using a batch adsorption procedure and the kinetics and thermodynamics of the adsorption process were further investigated. It was found that the adsorption kinetics was well fitted by a pseudo-second-order model and the adsorption isotherms agreed well with the Langmuir model. The maximum adsorption capacity after 5 min at room temperature (25 °C) was found to be 391.4 mg/g, which was much better than the most of the previously reported adsorbents. The adsorption process was found to be dominated by electrostatic interactions. The introduction of functional ionic liquid moieties into cross-linked poly(divinylbenzene) polymer constitutes a new and efficient kind of adsorbent. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Self-Healing and Thermo-Responsive Dual-Crosslinked Alginate Hydrogels based on Supramolecular Inclusion Complexes

    PubMed Central

    Miao, Tianxin; Fenn, Spencer L.; Charron, Patrick N.; Oldinski, Rachael A.

    2015-01-01

    β-cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of non-polar guest molecules to form non-covalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically-crosslinked hydrogel networks upon mixing with a guest molecule. Herein describes the development and characterization of self-healing, thermo-responsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic® F108 (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)). The mechanics, flow characteristics, and thermal response were contingent on the polymer concentrations, and the host-guest molar ratio. Transient and reversible physical crosslinking between host and guest polymers governed self-assembly, allowing flow under shear stress, and facilitating complete recovery of the material properties within a few seconds of unloading. The mechanical properties of the dual-crosslinked, multi-stimuli responsive hydrogels were tuned as high as 30 kPa at body temperature, and are advantageous for biomedical applications such as drug delivery and cell transplantation. PMID:26509214

  18. Influence of surfactant on dynamics of photoinduced motions in a dye-doped deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Jaroslaw; Parafiniuk, Kacper; Miniewicz, Andrzej; Rau, Ileana; Kajzar, Francois; Niziol, Jacek; Hebda, Edyta; Pielichowski, Jan; Sahraoui, Bouchta

    2012-10-01

    Pure deoxyribonucleic acid (DNA) is known to be soluble in water only and exhibits poor temperature stability. In contrary, it is well known that the complex of DNA - with cetyltrimethyl ammonium (CTMA) is soluble in alcohols and can be processed into very good optical quality thin films by solution casting and spin deposition. Despite the success of DNA-CTMA, there is still need for new cationic surfactants which would extend the range of available solvents for DNA complex. We test and present experimental results of influence of new surfactants based on benzalkonium chloride (BA), and didecyldimethylammonium chloride (DDCA) for applications in all optical switching.

  19. Facile fabrication of AIE-based stable cross-linked fluorescent organic nanoparticles for cell imaging.

    PubMed

    Zhang, Xiqi; Zhang, Xiaoyong; Yang, Bin; Hui, Junfeng; Liu, Meiying; Wei, Yen

    2014-04-01

    An aggregation induced emission dye (RNH2) with two amino end-groups was facilely incorporated into stable cross-linked fluorescent organic nanoparticles via room temperature anhydride ring-opening polymerization and consecutive cross-linking with polyethylene polyamine. Thus obtained RO-OA-PEPA FONs were characterized by a series of techniques including (1)H nuclear magnetic resonance, Fourier transform infrared spectroscopy, UV-vis absorption spectrum, fluorescent spectroscopy and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of RO-OA-PEPA FONs were further investigated to explore their potential biomedical application. We demonstrated that such FONs showed high-water dispersibility, strong red fluorescence, stable uniform morphology (100-200 nm) and excellent biocompatibility, making them promising for cell imaging application. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Intrinsically stretchable transparent electrodes based on silver-nanowire-crosslinked-polyacrylate composites.

    PubMed

    Hu, Weili; Niu, Xiaofan; Li, Lu; Yun, Sungryul; Yu, Zhibin; Pei, Qibing

    2012-08-31

    Stretchable transparent composites have been synthesized consisting of a silver nanowire (AgNW) network embedded in the surface layer of a crosslinked poly(acrylate) matrix. The interpenetrating networks of AgNWs and the crosslinked polymer matrix lead to high surface conductivity, high transparency, and rubbery elasticity. The presence of carboxylic acid groups on the polymer chains enhances the bonding between AgNWs and the polymer matrix, and further increases the stretchability of the composites. The sheet resistance of the composite electrode increases by only 2.3 times at 50% strain. Repeated stretching to 50% strain and relaxation only causes a small increase of the sheet resistance after 600 cycles. The morphology of the composites during reversible stretching and relaxation has been investigated to expound the conductivity changes.

  1. Intrinsically stretchable transparent electrodes based on silver-nanowire-crosslinked-polyacrylate composites

    NASA Astrophysics Data System (ADS)

    Hu, Weili; Niu, Xiaofan; Li, Lu; Yun, Sungryul; Yu, Zhibin; Pei, Qibing

    2012-08-01

    Stretchable transparent composites have been synthesized consisting of a silver nanowire (AgNW) network embedded in the surface layer of a crosslinked poly(acrylate) matrix. The interpenetrating networks of AgNWs and the crosslinked polymer matrix lead to high surface conductivity, high transparency, and rubbery elasticity. The presence of carboxylic acid groups on the polymer chains enhances the bonding between AgNWs and the polymer matrix, and further increases the stretchability of the composites. The sheet resistance of the composite electrode increases by only 2.3 times at 50% strain. Repeated stretching to 50% strain and relaxation only causes a small increase of the sheet resistance after 600 cycles. The morphology of the composites during reversible stretching and relaxation has been investigated to expound the conductivity changes.

  2. Effect of citric acid crosslinking cellulose-based hydrogels on osteogenic differentiation.

    PubMed

    Raucci, M G; Alvarez-Perez, M A; Demitri, C; Giugliano, D; De Benedictis, V; Sannino, A; Ambrosio, L

    2015-06-01

    Understanding the relationships between material surface properties and cellular responses is essential to designing optimal material surfaces for implantation and tissue engineering. In this study, cellulose hydrogels were crosslinked using a non-toxic and natural component namely citric acid. The chemical treatment induces COOH functional groups that improve the hydrophilicity, roughness, and materials rheological properties. The physiochemical, morphological, and mechanical analyses were performed to analyze the material surface before and after crosslinking. This approach would help determine if the effect of chemical treatment on cellulose hydrogel improves the hydrophilicity, roughness, and rheological properties of the scaffold. In this study, it was demonstrated that the biological responses of human mesenchymal stem cell with regard to cell adhesion, proliferation, and differentiation were influenced in vitro by changing the surface chemistry and roughness. © 2014 Wiley Periodicals, Inc.

  3. Extrahelical cytosine bases in DNA duplexes containing d[GCC](n).d[GCC](n) repeats: detection by a mechlorethamine crosslinking reaction.

    PubMed

    Rojsitthisak, P; Romero, R M; Haworth, I S

    2001-11-15

    The cytosine-cytosine (C-C) pair is one of the least stable DNA mismatch pairs. The bases of the C-C mismatch are only weakly hydrogen bonded, and previous work has shown that, in certain sequence contexts, they can become unstacked from the core helix, and adopt an 'extrahelical' location. Here, using DNA duplexes with d[GCC](n).d[GCC](n) fragments containing C-C mismatches in a 1,4 bp relationship, we show that cytosine bases of different formal mismatch pairs can be crosslinked by mechlorethamine. For example, in the duplex d[CTCTCGCCGCCGCCGTATC].d[GATACGCCGCCGCCGAGAG], where underlined cytosine bases are present as the formal C-C mismatch pairs C(7)-C(32), C(10)-C(29) and C(13)-C(26), we show that two mechlorethamine crosslinks form between C(13) and C(29) and between C(10) and C(32), in addition to crosslinks at C(7)-C(32), C(10)-C(29) and C(13)-C(26) (we have reported previously the crosslinking of formal C-C pairs by mechlorethamine). We interpret the formation of the C(13)-C(29) and C(10)-C(32) crosslinks as evidence of an extrahelical location of the crosslinkable cytosines. Such extrahelical cytosine bases have been observed previously for a single C-C mismatch pair (in the so-called E-motif conformation). In the E-motif, the extrahelical cytosines are folded back towards the 5'-end of the duplex, consistent with our crosslinking data, and also consistent with the absence of C(7)-C(29) and C(10)-C(26) crosslinks in the current work. Hence, our data provide evidence for an extended E-motif DNA (eE-DNA) conformation in short d[GCC](n).d[GCC](n) repeat fragments, and raise the possibility that such structures might occur in much longer d[GCC](n).d[GCC](n) repeat tracts.

  4. Structure-based non-canonical amino acid design to covalently crosslink an antibody-antigen complex.

    PubMed

    Xu, Jianqing; Tack, Drew; Hughes, Randall A; Ellington, Andrew D; Gray, Jeffrey J

    2014-02-01

    Engineering antibodies to utilize non-canonical amino acids (NCAA) should greatly expand the utility of an already important biological reagent. In particular, introducing crosslinking reagents into antibody complementarity determining regions (CDRs) should provide a means to covalently crosslink residues at the antibody-antigen interface. Unfortunately, finding the optimum position for crosslinking two proteins is often a matter of iterative guessing, even when the interface is known in atomic detail. Computer-aided antibody design can potentially greatly restrict the number of variants that must be explored in order to identify successful crosslinking sites. We have therefore used Rosetta to guide the introduction of an oxidizable crosslinking NCAA, l-3,4-dihydroxyphenylalanine (l-DOPA), into the CDRs of the anti-protective antigen scFv antibody M18, and have measured crosslinking to its cognate antigen, domain 4 of the anthrax protective antigen. Computed crosslinking distance, solvent accessibility, and interface energetics were three factors considered that could impact the efficiency of l-DOPA-mediated crosslinking. In the end, 10 variants were synthesized, and crosslinking efficiencies were generally 10% or higher, with the best variant crosslinking to 52% of the available antigen. The results suggest that computational analysis can be used in a pipeline for engineering crosslinking antibodies. The rules learned from l-DOPA crosslinking of antibodies may also be generalizable to the formation of other crosslinked interfaces and complexes.

  5. Microporous Organic Polymers Based on Hyper-Crosslinked Coal Tar: Preparation and Application for Gas Adsorption.

    PubMed

    Gao, Hui; Ding, Lei; Bai, Hua; Li, Lei

    2017-02-08

    Hyper-crosslinked polymers (HCPs) are promising materials for gas capture and storage, but high cost and complicated preparation limit their practical application. In this paper, a new type of HCPs (CTHPs) was synthesized through a one-step mild Friedel-Crafts reaction with low-cost coal tar as the starting material. Chloroform was utilized as both solvent and crosslinker to generate a three-dimensional crosslinked network with abundant micropores. The maximum BET surface area of the prepared CTHPs could reach up to 929 m(2)  g(-1) . Owing to the high affinity between the heteroatoms on the coal-tar building blocks and the CO2 molecules, the adsorption capacity of CTHPs towards CO2 reached up to 14.2 wt % (1.0 bar, 273 K) with a high selectivity (CO2 /N2 =32.3). Furthermore, the obtained CTHPs could adsorb 1.27 wt % H2 at 1.0 bar and 77.3 K, and also showed capacity for the capture of high organic vapors at room temperature. In comparison with other reported porous organic polymers, CTHPs have the advantages of low-cost, easy preparation, and high gas-adsorption performance, making them suitable for mass production and practical use in the future.

  6. Nanofiltration membranes based on polyvinylidene fluoride nanofibrous scaffolds and crosslinked polyethyleneimine networks

    NASA Astrophysics Data System (ADS)

    Park, Seong-Jik; Cheedrala, Ravi Kumar; Diallo, Mamadou S.; Kim, Changmin; Kim, In S.; Goddard, William A.

    2012-07-01

    In this article, we describe the synthesis of new and ion-selective nanofiltration (NF) membranes using polyvinylidene fluoride (PVDF) nanofibers and hyperbranched polyethylenimine (PEI) as building blocks. These new nanofibrous composite (NFC) membranes consist of crosslinked hyperbranched PEI networks supported by PVDF nanofibrous scaffolds that are electrospun onto commercial PVDF microfiltration (MF) membranes. A major objective of our study was to fabricate positively charged NF membranes that can be operated at low pressure with high water flux and improved rejection for monovalent cations. To achieve this, we investigated the effects of crosslinker chemistry on membrane properties (morphology, composition, hydrophobicity, and zeta potential) and membrane performance (salt rejection and permeate flux) in aqueous solutions (2,000 mg/L) of four salts (NaCl, MgCl2, Na2SO4, and MgSO4) at pH 4, 6, and 8. We found that an NFC-PVDF membrane with a network of PEI macromolecules crosslinked with trimesoyl chloride has a high water flux ( 30 L m-2 h-1) and high rejections for MgCl2 ( 88 %) and NaCl ( 65 %) at pH 6 using a pressure of 7 bar. The overall results of our study suggest that PVDF nanofibers and hyperbranched PEI are promising building blocks for the fabrication of high performance NF membranes for water purification.

  7. Fragmentation behavior of a thiourea-based reagent for protein structure analysis by collision-induced dissociative chemical cross-linking.

    PubMed

    Müller, Mathias Q; Dreiocker, Frank; Ihling, Christian H; Schäfer, Mathias; Sinz, Andrea

    2010-08-01

    The fragmentation behavior of a novel thiourea-based cross-linker molecule specifically designed for collision-induced dissociation (CID) MS/MS experiments is described. The development of this cross-linker is part of our ongoing efforts to synthesize novel reagents, which create either characteristic fragment ions or indicative constant neutral losses (CNLs) during tandem mass spectrometry allowing a selective and sensitive analysis of cross-linked products. The new derivatizing reagent for chemical cross-linking solely contains a thiourea moiety that is flanked by two amine-reactive N-hydroxy succinimide (NHS) ester moieties for reaction with lysines or free N-termini in proteins. The new reagent offers simple synthetic access and easy structural variation of either length or functionalities at both ends. The thiourea moiety exhibits specifically tailored CID fragmentation capabilities--a characteristic CNL of 85 u--ensuring a reliable detection of derivatized peptides by both electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry and as such possesses a versatile applicability for chemical cross-linking studies. A detailed examination of the CID behavior of the presented thiourea-based reagent reveals that slight structural variations of the reagent will be necessary to ensure its comprehensive and efficient application for chemical cross-linking of proteins.

  8. Formation of wheat-protein-based biomaterials through polymer grafting and crosslinking reactions to introduce new functional properties.

    PubMed

    Kurniawan, Lusiana; Qiao, Greg G; Zhang, Xiaoqing

    2009-01-09

    An insoluble wheat proteins-based polymer networks with new functional groups and positive charges were prepared through grafting-coupling reactions. The networks were also flexible with a lower glass transition temperature since the existence of the grafted mobile segments. The multi-component/multi-phase systems became relatively homogeneous on a scale of 20-30 nm due to strong intermolecular interactions and chemical cross-linking in the materials. This demonstrates that the grafting-coupling reaction is an effective methodology to develop biomaterials with modified functional and mechanical properties from proteins.

  9. Shell cross-linked micelle-based nanoreactors for the substrate-selective hydrolytic kinetic resolution of epoxides.

    PubMed

    Liu, Yu; Wang, Yu; Wang, Yufeng; Lu, Jie; Piñón, Victor; Weck, Marcus

    2011-09-14

    Shell cross-linked micelles (SCMs) containing Co(III)-salen cores were prepared from amphiphilic poly(2-oxazoline) triblock copolymers. The catalytic activity of these nanoreactors for the hydrolytic kinetic resolution of various terminal epoxides was investigated. The SCM catalysts showed high catalytic efficiency and, more significantly, substrate selectivity based on the hydrophobic nature of the epoxide. Moreover, because of the nanoscale particle size and the high stability, the catalyst could be recovered easily by ultrafiltration and reused with high activity for eight cycles.

  10. Fundamental Interaction Between Au Nanoparticles and Deoxyribonucleic Acid (DNA)

    DTIC Science & Technology

    2010-06-01

    Fundamental Interaction Between Au Nanoparticles and Deoxyribonucleic Acid (DNA) by Molly Karna, Govind Mallick, and Shashi P. Karna ARL...Karna Science and Mathematics Academy at Aberdeen High School Govind Mallick and Shashi P. Karna Weapons and Materials Research Directorate, ARL...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Molly Karna, Govind Mallick, and Shashi P. Karna 5d. PROJECT NUMBER 5e. TASK NUMBER

  11. Synthesis, characterization, and DNA adsorption studies of ampholytic model conetworks based on cross-linked star copolymers.

    PubMed

    Georgiou, Theoni K; Patrickios, Costas S

    2008-02-01

    Five model conetworks based on cross-linked star ampholytic copolymers were synthesized by group transfer polymerization. The ampholytic copolymers were based on two hydrophilic monomers: the positively ionizable 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the negatively ionizable methacrylic acid (MAA). Ethylene glycol dimethacrylate was used as the cross-linker. These five ampholytic model conetworks were isomers based on equimolar DMAEMA-MAA copolymer stars of different architectures: heteroarm (two), star block (two), and statistical. The two networks based on the homopolymer stars were also synthesized. The MAA units were introduced via the polymerization of tetrahydropyranyl methacrylate and the acid hydrolysis of the latter after network formation. All the precursors to the (co)networks were characterized in terms of their molecular weights using gel permeation chromatography (GPC). The mass of the extractables from the (co)networks was measured and characterized in terms of molecular weight and composition using GPC and proton nuclear magnetic resonance (1H NMR) spectroscopy, respectively. The degrees of swelling (DS) of all the ampholytic conetworks were measured as a function of pH and were found to present a minimum at a pH value which was taken as the isoelectric point, pI. The DS and the pI values did not present a dependence on conetwork architecture. Finally, DNA adsorption studies onto the ampholyte conetworks indicated that DNA binding was governed by electrostatics.

  12. Characterization of Biosensors Based on Recombinant Glutamate Oxidase: Comparison of Crosslinking Agents in Terms of Enzyme Loading and Efficiency Parameters

    PubMed Central

    Ford, Rochelle; Quinn, Susan J.; O’Neill, Robert D.

    2016-01-01

    Amperometric l-glutamate (Glu) biosensors, based on both wild-type and a recombinant form of l-glutamate oxidase (GluOx), were designed and characterized in terms of enzyme-kinetic, sensitivity and stability parameters in attempts to fabricate a real-time Glu monitoring device suitable for future long-term detection of this amino acid in biological and other complex media. A comparison of the enzyme from these two sources showed that they were similar in terms of biosensor performance. Optimization of the loading of the polycationic stabilization agent, polyethyleneimine (PEI), was established before investigating a range of crosslinking agents under different conditions: glutaraldehyde (GA), polyethylene glycol (PEG), and polyethylene glycol diglycidyl ether (PEGDE). Whereas PEI-free biosensor designs lost most of their meager Glu sensitivity after one or two days, configurations with a 2:5 ratio of dip-evaporation applications of PEI(1%):GluOx(400 U/mL) displayed a 20-fold increase in their initial sensitivity, and a decay half-life extended to 10 days. All the crosslinkers studied had no effect on initial Glu sensitivity, but enhanced biosensor stability, provided the crosslinking procedure was carried out under well-defined conditions. The resulting biosensor design based on the recombinant enzyme deposited on a permselective layer of poly-(ortho-phenylenediamine), PoPD/PEI2/GluOx5/PEGDE, displayed good sensitivity (LOD < 0.2 μM), response time (t90% < 1 s) and stability over a 90-day period, making it an attractive candidate for future long-term monitoring of Glu concentration dynamics in complex media. PMID:27669257

  13. Fabrication and properties of magnetorheological elastomers based on CR/ENR self-crosslinking blends

    NASA Astrophysics Data System (ADS)

    Wang, Yonghong; Zhang, Xinru; Oh, Jaeeung; Chung, Kyungho

    2015-09-01

    Magnetorheological elastomers (MREs) are intelligent materials, which are widely used as dampers to eliminate vibration. In this study, a new kind of MREs was designed using carbonyl iron particles (CIPs), carbon black (CB) and self-crosslinking blends, which were fabricated by reacting polychloroprene rubber with epoxidized natural rubber (CR/ENR blends). The interaction mechanism among CIPs, CB and a matrix in the fabrication process was discussed in detail. The morphology of isotropic MREs (i-MREs) and anisotropic MREs (a-MREs) was observed by scanning electron microscopy (SEM). The effect of CIP volume content on the mechanical properties of MREs was investigated. The effect of CIP volume content on the shear storage modulus, MR effect and loss factor was studied using a modified dynamic mechanical analyzer (DMA). The results revealed that the chain-like distribution of CIPs became more pronounced with increasing CIP content in a-MREs, whereas CIPs distributed uniformly in i-MREs. CIPs and CB bonded well with the rubber matrix as a result of their surface attraction effect to CR and ENR molecular chains. Therefore, MREs had excellent mechanical properties. The promoting effect of CB and CIPs on the self-crosslinking reaction was verified by crosslink density assessment. The shear storage modulus of MREs increased with the increase of CIP content, and the MR effect of i-MREs remarkably increased, while a-MREs decreased due to the obvious increase in initial storage modulus with increasing CIP content. The loss factor of MREs decreased obviously with the increase of CIP content.

  14. Synthesis and properties of novel 2'-C,4'-C-ethyleneoxy-bridged 2'-deoxyribonucleic acids with exocyclic methylene groups.

    PubMed

    Osawa, Takashi; Obika, Satoshi; Hari, Yoshiyuki

    2016-10-12

    Three 2'-C,4'-C-ethyleneoxy-bridged 2'-deoxyribonucleic acids possessing six-membered bridges with 6'-oxygen and 8'-exocyclic methylene groups (methylene-EoDNAs) were designed and synthesized in nine to ten steps from 5-methyluridine. The methylene-EoDNA-modified oligonucleotides showed excellent binding affinity with target ssRNA and extremely high nuclease resistance compared with natural oligonucleotides. These results proved the potential of methylene-EoDNAs for nucleic acid based technology.

  15. Identification of Crosslinked Peptides after Click-based Enrichment Using Sequential CID and ETD Tandem Mass Spectrometry

    PubMed Central

    Chowdhury, Saiful M.; Du, Xiuxia; Tolić, Nikola; Wu, Si; Moore, Ronald J.; Mayer, M. Uljana; Smith, Richard D.; Adkins, Joshua N.

    2010-01-01

    Chemical crosslinking combined with mass spectrometry can be a powerful approach for the identification of protein-protein interactions and for providing constraints on protein structures. However, enrichment of crosslinked peptides is crucial to reduce sample complexity before mass spectrometric analysis. In addition compact crosslinkers are often preferred to provide short spacer lengths, surface accessibility to the protein complexes, and must have reasonable solubility under condition where the native complex structure is stable. In this study, we present a novel compact crosslinker that contains two distinct features: 1) an alkyne tag and 2) a small molecule detection tag (NO2-) to maintain reasonable solubility in water. The alkyne tag enables enrichment of the crosslinked peptide after proteolytic cleavage after coupling of an affinity tag using alkyne-azido click chemistry. Neutral loss of the small NO2- moiety provides a secondary means of detecting crosslinked peptides in MS/MS analyses, providing additional confidence in peptide identifications. We show the labeling efficiency of this crosslinker, which we termed CLIP (Click-enabled Linker for Interacting Proteins) using ubiquitin. The enrichment capability of CLIP is demonstrated for crosslinked ubiquitin in highly complex E. coli cell lysates. Sequential CID-MS/MS and ETD-MS/MS of inter-crosslinked peptides (two peptides connected with a crosslinker) are also demonstrated for improved automated identification of crosslinked peptides. PMID:19496583

  16. Evaluation of thermally crosslinkable chitosan-based nanofibrous mats for the removal of metal ions.

    PubMed

    Huang, Chih-Hao; Hsieh, Te-Hsien; Chiu, Wen-Yen

    2015-02-13

    Environmentally sensitive composite nanofibrous mats capable of metal ion adsorption were successfully prepared via electrospinning. The composite nanofibers were fabricated with different ratios of chitosan to thermo-responsive polymer, poly(N-isopropylacrylamide-co-N-methylolacrylamide) (poly(NIPAAm-co-NMA), PNN). NMA provided the function of thermal crosslinking of the nanofibrous mats to form water-stable nanofibers in aqueous solution. Subsequently, glutaraldehyde was used as a secondary crosslinking agent to increase the gel fraction of the nanofibrous mats. The morphology changes of the nanofibers in different environments were studied. Comparing the nanofibrous mats and films of the same material, the fibrous mats showed significantly increased adsorption of Cu(II). The adsorption amount of Cu(II) on the chitosan/PNN (50/50) nanofibrous mats could reach 79±2 mg/g-mats, and its desorption was relatively effective. The incorporation of poly(NIPAAm-co-NMA) significantly improved the desorption of Cu(II) from the nanofibrous mats. The chitosan/PNN fibrous mats maintained the capacity of Cu(II) adsorption for 4-time regeneration. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Thermally cross-linkable hole transport polymers for solution-based organic light-emitting diodes.

    PubMed

    Cha, Seung Ji; Cho, Se-Na; Lee, Woo-Hyung; Chung, Ha-Seul; Kang, In-Nam; Suh, Min Chul

    2014-04-01

    Two thermally cross-linkable hole transport polymers that contain phenoxazine and triphenylamine moieties, X-P1 and X-P2, are developed for use in solution-processed multi-stack organic light-emitting diodes (OLEDs). Both X-P1 and X-P2 exhibit satisfactory cross-linking and optoelectronic properties. The highest occupied molecular orbital (HOMO) levels of X-P1 and X-P2 are -5.24 and -5.16 eV, respectively. Solution-processed super yellow polymer devices (ITO/X-P1 or X-P2/PDY-132/LiF/Al) with X-P1 or X-P2 hole transport layers of various thicknesses are fabricated with the aim of optimizing the device characteristics. The fabricated multi-stack yellow devices containing the newly synthesized hole transport polymers exhibit satisfactory currents and power efficiencies. The optimized X-P2 device exhibits a device efficiency that is dramatically improved by more than 66% over that of a reference device without an HTL.

  18. PEG-Based Hydrogels with Collagen Mimetic Peptide-Mediated and Tunable Physical Crosslinks

    PubMed Central

    Stahl, Patrick J.; Romano, Nicole H.; Wirtz, Denis; Yu, S. Michael

    2010-01-01

    Mechanical properties of tissue scaffolds have major effects on the morphology and differentiation of cells. In contrast to two-dimensional substrates, local biochemical and mechanical properties of three-dimensional hydrogels are difficult to control due to the geometrical confinement. We designed synthetic 3D hydrogels featuring complexes of four-arm poly(ethylene glycol) (PEG) and collagen mimetic peptides (CMPs) that form hydrogels via physical crosslinks mediated by thermally reversible triple helical assembly of CMPs. Here we present the fabrication of various PEG-CMP 3D hydrogels and their local mechanical properties determined by particle tracking microrheology. Results show that CMP mediated physical crosslinks can be disrupted by altering the temperature of the gel or by adding free CMPs that compete for triple helix formation. This allowed modulation of both bulk and local stiffness as well as the creation of stiffness gradients within the PEG-CMP hydrogel, which demonstrates its potential as a novel scaffold for encoding physico-chemical signals for tissue formation. PMID:20715762

  19. Column adsorption of perchlorate by amine-crosslinked biopolymer based resin and its biological, chemical regeneration properties.

    PubMed

    Song, Wen; Xu, Xing; Tan, Xin; Wang, Yan; Ling, Jianya; Gao, Baoyu; Yue, Qinyan

    2015-01-22

    Column adsorption of perchlorate by amine-crosslinked biopolymer based resin was investigated by considering the bed depth, stream flow rate and influent pH. The empty bed contact time (EBCT) increased with the growth of bed depths, meanwhile rising flow rate at constant bed depth (3.4 cm) decreased the breakthrough time. It was observed that perchlorate adsorption capacity was optimum at neutral condition (pH: 6.0, 170.4 mg/g), and decreased at acidic (pH: 3.0, 96.4 mg/g) or alkalic (pH: 12.0, 72.8 mg/g) influents. The predominant strains of the acclimated sludge for resin biological regeneration were the β-subclass of Proteobacteria. Biological regeneration of the saturated amine-crosslinked biopolymer based resin with mixed bacteria have shown its merit with regeneration and biological perchlorate destruction simultaneously, although its regeneration efficiency was only 61.2-84.1% by contrast to chemical regeneration with efficiency more than 95%. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Analysis of the addition of a crosslinking agent in pyrromethene-HEMA based photopolymerizable holographic recording materials

    NASA Astrophysics Data System (ADS)

    Blaya, S.; Acebal, P.; Carretero, L.; Madrigal, R. F.; Murciano, A.; Fimia, A.

    2011-06-01

    In this work, we present the analysis of a photopolymerizable system based on pyrromethene dye (PM567) acting as a photoinitiator and HEMA as monomer both of them dissolved in a dry polymeric matrix of PMMA. Previously, we reported the recording of diffraction gratings in this composition, resulting in diffraction efficiencies near 60 % with exposures of 1 J/cm2 in materials with thicknesses around 500 microns. Although, the mentioned response (best) was observed at low intensities but at higher ones lower diffraction efficiencies were reached. Furthermore, in all the studied cases inhibition periods with asymmetrical angular selectivity curves were obtained. Since, in order to solve the mentioned drawbacks, the aim of this work is to analyze the effect of the addition of a crosslinking agent (PETA) in a photopolymerizable holographic material based on a pyrromethene dye (PM567) acting as a photoinitiator and HEMA as monomer both of them dissolved in a dry polymeric matrix of PMMA. For this, diffraction gratings were recorded at different intensities and the energetic evolution of the diffraction efficiency as well as the observed inhibition period were studied as a function of the concentration of crosslinking agent. Moreover, the experimental angular selectivity curves were theoretically analyzed by the model of Kubota and Uchida, and as a result information such as the effective thickness, fringe bending and non-uniform index modulation against the thickness of grating was obtained.

  1. Modulated in Vitro Biocompatibility of a Unique Cross-Linked Salicylic Acid-Poly(ε-caprolactone)-Based Biodegradable Polymer.

    PubMed

    Bhaskar, Nitu; Padmavathy, Nagarajan; Jain, Shubham; Bose, Suryasarathi; Basu, Bikramjit

    2016-11-02

    Herein, we report the development of a unique architecture by chemically cross-linking salicylic acid (SA)-based poly(anhydride ester) onto a biodegradable amine-functionalized poly(caprolactone) (PCL), using lactic acid as a spacer. The ester and amide linkages in the SA-PCL polymer, synthesized through melt condensation, were confirmed by NMR and FT-IR spectroscopic techniques. The enzymatic and nonenzymatic hydrolytic degradation profile exhibited linear degradation kinetics over an extended time period (>5 weeks). The compatibility and growth of C2C12 myoblast cells were found to be significantly improved on the fast-degrading SA-PCL substrates compared to those over neat PCL and amine-functionalized PCL. Further, the decreased red blood cell damage, illustrated by 0.39% hemolysis activity and a minimal number of platelet adhesion on a SA-PCL polymeric surface confirmed good hemocompatibility of the as-synthesized polymer. Together with a moderate bactericidal property, the spectrum of properties of this novel polymer can be attributed to the synergistic effect of the presence of chemical moieties of SA and amine groups in PCL. In summary, it is considered that a SA-PCL-based cross-linked composite can be utilized as a new biodegradable polymer.

  2. Aromatic nitrogen mustard-based prodrugs: activity, selectivity, and the mechanism of DNA cross-linking.

    PubMed

    Chen, Wenbing; Han, Yanyan; Peng, Xiaohua

    2014-06-10

    Three novel H2O2-activated aromatic nitrogen mustard prodrugs (6-8) are reported. These compounds contain a DNA alkylating agent connected to a H2O2-responsive trigger by different electron-withdrawing linkers so that they are inactive towards DNA but can be triggered by H2O2 to release active species. The activity and selectivity of these compounds towards DNA were investigated by measuring DNA interstrand cross-link (ICL) formation in the presence or absence of H2O2. An electron-withdrawing linker unit, such as a quaternary ammonia salt (6), a carboxyamide (7), and a carbonate group (8), is sufficient to deactivate the aromatic nitrogen mustard resulting in less than 1.5 % cross-linking formation. However, H2O2 can restore the activity of the effectors by converting a withdrawing group to a donating group, therefore increasing the cross-linking efficiency (>20 %). The stability and reaction sites of the ICL products were determined, which revealed that alkylation induced by 7 and 8 not only occurred at the purine sites but also at the pyrimidine site. For the first time, we isolated and characterized the monomer adducts formed between the canonical nucleosides and the aromatic nitrogen mustard (15) which supported that nitrogen mustards reacted with dG, dA, and dC. The activation mechanism was studied by NMR spectroscopic analysis. An in vitro cytotoxicity assay demonstrated that compound 7 with a carboxyamide linker dramatically inhibited the growth of various cancer cells with a GI50 of less than 1 μM, whereas compound 6 with a charged linker did not show any obvious toxicity in all cell lines tested. These data indicated that a neutral carboxyamide linker is preferable for developing nitrogen mustard prodrugs. Our results showed that 7 is a potent anticancer prodrug that can serve as a model compound for further development. We believe these novel aromatic nitrogen mustards will inspire further and effective applications.

  3. Direct comparison of two albumin-based paclitaxel-loaded nanoparticle formulations: is the crosslinked version more advantageous?

    PubMed

    Li, Chunlei; Li, Yanhui; Gao, Yuqing; Wei, Na; Zhao, Xi; Wang, Caixia; Li, Yongfeng; Xiu, Xian; Cui, Jingxia

    2014-07-01

    Nanoparticles using albumin as particle matrix have entered the mainstream of drug delivery. It was reported that non-crosslinked albumin nanoparticles were unstable in circulation and could deliver drugs into tumor through gp60/SPARC pathway; in contrast, the delivery of drugs with stable nanoparticles was dependent on enhanced permeability and retention effect. Thus, it is questionable which kind of nanoparticles was more advantageous. Two versions of albumin-bound paclitaxel nanoparticles were prepared. In vitro, the non-crosslinked particles could rapidly disintegrate and the crosslinked was stable. The pharmacokinetics of both formulations was different especially at early time and the non-crosslinked particles were cleared rapidly. After non-crosslinked particle treatment paclitaxel had a tendency to accumulate into heart and kidney and following therapy with the crosslinked particles, paclitaxel was liable to be delivered into lung, spleen and liver. The delivery efficiency of paclitaxel into tumor following the non-crosslinked particle treatment was greater than that of the crosslinked (p<0.05), thus resulting in a considerably improved antineoplastic activity. Moreover, the non-crosslinked formulation was only slightly more toxic. It was concluded that the non-crosslinked formulation was more advantageous for the delivery of paclitaxel and our conclusion might be generalized to other lipophilic drugs delivered with albumin nanoparticles.

  4. Particulate Composite Materials: Numerical Modeling of a Cross-Linked Polymer Reinforced With Alumina-Based Particles

    NASA Astrophysics Data System (ADS)

    Máša, B.; Náhlík, L.; Hutař, P.

    2013-09-01

    The macroscopic mechanical properties of a particulate composite under uniaxial tensile loading have been estimated. The composite studied consisted of a polymer matrix in a rubbery state (polymethylmethacrylate - PMMA) and alumina-based particles (Al2O3). A numerical modeling by using the finite-element method (FEM) was performed to determine the stress-strain behavior of the particulate composite. The numerical simulation took into account the hyperelastic properties of the cross-linked polymer matrix, which was described by the three-parameter Mooney-Rivlin material model. A representative volume element (RVE) was chosen for FE analyses to model the microstructure of the composite. Various compositions of particles and their different shape and orientation were considered in the study. Various directions of loading of the RVE were also investigated. A progressive damage model was implemented into the numerical models. The mechanical characteristics obtained from computations, which included the damage model, were compared with experimental data, and a good agreement has been found to exist between them. The procedure presented can be used for estimating the mechanical properties of new particulate composites with a cross-linked polymer matrix, and it also contributes to the clarification of damage development and failure in composites of the type studied.

  5. 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

  6. Novel semi-IPN based on crosslinked carboxymethyl starch and clay for the in vitro release of theophylline.

    PubMed

    Anirudhan, T S; Parvathy, J

    2014-06-01

    A novel semi-interpenetrating polymer network (IPN) based on crosslinked carboxymethyl starch (CL-CMS) and montmorillonite (MMT) was prepared, where carboxymethylation occurs as a result of the reaction between native starch and monochloroacetic acid in isopropanol/water medium at 60°C. The carboxymethyl starch is further crosslinked and made into a semi-IPN with MMT for the release of theophylline. The drug carrier was characterized using FTIR, XRD and surface analysis using SEM. Studies including physio-chemical analysis, swelling behavior, encapsulation efficiency, effect of MMT content, effect of ionic strength and in vitro drug release were carried out. Theophylline encapsulation of up to 74% was achieved and drug release was monitored in SGF (pH 1.2) and SIF (pH 7.4). Results show that the matrix releases drug at a much faster rate in the basic medium than in the acidic medium, thereby holding the promise of developing the semi-IPN system as a potential candidate for the release of theophylline. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Characterization of superabsorbent hydrogel based on epichlorohydrin crosslink and carboxymethyl functionalization of cassava starch

    NASA Astrophysics Data System (ADS)

    Muharam, S.; Yuningsih, L. M.; Sumitra, M. R.

    2017-07-01

    Superabsorbent hydrogel was prepared by epichlorohydrin crosslink of cassava starch. Their swelling improved with added carboxymethyl group on the starch-epichlorohydrin structure. The structure and properties of starch-epichlorohydrin-carboxymethyl hydrogel were measured by SEM, FTIR, water and physiological solution absorption test and water retention test. The result showed that hydrogel displayed macroporous with heterogenous distribution and irregular surface was formed by epichlorohydrin and carboxymethyl bond in the structure of hydrogel. It was confirmed also by the FTIR spectra. The swelling ratio of starch-epichlorohydrin hydrogel to the water is 518 % and increased to 1,028.5 % with carboxymethyl addition on the structure. The best influence of the physiological solution to the swelling ratio of starch-epichlorohydrin-carboxymethyl hydrogel is urea solution. The water retention of starch-epichlorohydrin-carboxymethyl hydrogel in NaCl solution is better than in CaCl2 solution.

  8. Cross-linking by protein oxidation in the rapidly setting gel-based glues of slugs

    PubMed Central

    Bradshaw, Andrew; Salt, Michael; Bell, Ashley; Zeitler, Matt; Litra, Noelle; Smith, Andrew M.

    2011-01-01

    SUMMARY The terrestrial slug Arion subfuscus secretes a glue that is a dilute gel with remarkable adhesive and cohesive strength. The function of this glue depends on metals, raising the possibility that metal-catalyzed oxidation plays a role. The extent and time course of protein oxidation was measured by immunoblotting to detect the resulting carbonyl groups. Several proteins, particularly one with a relative molecular mass (Mr) of 165×103, were heavily oxidized. Of the proteins known to distinguish the glue from non-adhesive mucus, only specific size variants were oxidized. The oxidation appears to occur within the first few seconds of secretion. Although carbonyls were detected by 2,4-dinitrophenylhydrazine (DNPH) in denatured proteins, they were not easily detected in the native state. The presence of reversible cross-links derived from carbonyls was tested for by treatment with sodium borohydride, which would reduce uncross-linked carbonyls to alcohols, but stabilize imine bonds formed by carbonyls and thus lead to less soluble complexes. Consistent with imine bond formation, sodium borohydride led to a 20–35% decrease in the amount of soluble protein with a Mr of 40–165 (×103) without changing the carbonyl content per protein. In contrast, the nucleophile hydroxylamine, which would competitively disrupt imine bonds, increased protein solubility in the glue. Finally, the primary amine groups on a protein with a Mr of 15×103 were not accessible to acid anhydrides. The results suggest that cross-links between aldehydes and primary amines contribute to the cohesive strength of the glue. PMID:21525316

  9. Cross-linking by protein oxidation in the rapidly setting gel-based glues of slugs.

    PubMed

    Bradshaw, Andrew; Salt, Michael; Bell, Ashley; Zeitler, Matt; Litra, Noelle; Smith, Andrew M

    2011-05-15

    The terrestrial slug Arion subfuscus secretes a glue that is a dilute gel with remarkable adhesive and cohesive strength. The function of this glue depends on metals, raising the possibility that metal-catalyzed oxidation plays a role. The extent and time course of protein oxidation was measured by immunoblotting to detect the resulting carbonyl groups. Several proteins, particularly one with a relative molecular mass (M(r)) of 165 x 10³, were heavily oxidized. Of the proteins known to distinguish the glue from non-adhesive mucus, only specific size variants were oxidized. The oxidation appears to occur within the first few seconds of secretion. Although carbonyls were detected by 2,4-dinitrophenylhydrazine (DNPH) in denatured proteins, they were not easily detected in the native state. The presence of reversible cross-links derived from carbonyls was tested for by treatment with sodium borohydride, which would reduce uncross-linked carbonyls to alcohols, but stabilize imine bonds formed by carbonyls and thus lead to less soluble complexes. Consistent with imine bond formation, sodium borohydride led to a 20-35% decrease in the amount of soluble protein with a M(r) of 40-165 (x 10³) without changing the carbonyl content per protein. In contrast, the nucleophile hydroxylamine, which would competitively disrupt imine bonds, increased protein solubility in the glue. Finally, the primary amine groups on a protein with a M(r) of 15 x 10³ were not accessible to acid anhydrides. The results suggest that cross-links between aldehydes and primary amines contribute to the cohesive strength of the glue.

  10. Application of Markov chain to the pattern of mitochondrial deoxyribonucleic acid mutations

    NASA Astrophysics Data System (ADS)

    Vantika, Sandy; Pasaribu, Udjianna S.

    2014-03-01

    This research explains how Markov chain used to model the pattern of deoxyribonucleic acid mutations in mitochondrial (mitochondrial DNA). First, sign test was used to see a pattern of nucleotide bases that will appear at one position after the position of mutated nucleotide base. Results obtained from the sign test showed that for most cases, there exist a pattern of mutation except in the mutation cases of adenine to cytosine, adenine to thymine, and cytosine to guanine. Markov chain analysis results on data of mutations that occur in mitochondrial DNA indicate that one and two positions after the position of mutated nucleotide bases tend to be occupied by particular nucleotide bases. From this analysis, it can be said that the adenine, cytosine, guanine and thymine will mutate if the nucelotide base at one and/or two positions after them is cytosine.

  11. Collagen cross-linking using riboflavin and ultraviolet-a for corneal thinning disorders: an evidence-based analysis.

    PubMed

    Pron, G; Ieraci, L; Kaulback, K

    2011-01-01

    The main objectives for this evidence-based analysis were to determine the safety and effectiveness of photochemical corneal collagen cross-linking with riboflavin (vitamin B(2)) and ultraviolet-A radiation, referred to as CXL, for the management of corneal thinning disease conditions. The comparative safety and effectiveness of corneal cross-linking with other minimally invasive treatments such as intrastromal corneal rings was also reviewed. The Medical Advisory Secretariat (MAS) evidence-based analysis was performed to support public financing decisions. SUBJECT OF THE EVIDENCE-BASED ANALYSIS: The primary treatment objective for corneal cross-linking is to increase the strength of the corneal stroma, thereby stabilizing the underlying disease process. At the present time, it is the only procedure that treats the underlying disease condition. The proposed advantages for corneal cross-linking are that the procedure is minimally invasive, safe and effective, and it can potentially delay or defer the need for a corneal transplant. In addition, corneal cross-linking does not adversely affect subsequent surgical approaches, if they are necessary, or interfere with corneal transplants. The evidence for these claims for corneal cross-linking in the management of corneal thinning disorders such as keratoconus will be the focus of this review. The specific research questions for the evidence review were as follows: TECHNICAL: How technically demanding is corneal cross-linking and what are the operative risks? What is known about the broader safety profile of corneal cross-linking?Effectiveness - Corneal Surface Topographic Affects:What are the corneal surface remodeling effects of corneal cross-linking?Do these changes interfere with subsequent interventions, particularly corneal transplant known as penetrating keratoplasty (PKP)?Effectiveness -Visual Acuity:What impacts does the remodeling have on visual acuity?Are these impacts predictable, stable, adjustable and

  12. Migration of melamine from can coatings cross-linked with melamine-based resins, into food simulants and foods.

    PubMed

    Bradley, E L; Castle, L; Day, J S; Leak, J

    2011-02-01

    Resins based on melamine-formaldehyde and related analogues such as methylolated melamine are used to cross-link coatings used inside food cans and on the metal closures of glass jars. Thirteen commercially coated cans and closures representing 80% of the European market were tested using simulants under realistic industrial heat-processing conditions for canned and jarred foods. The food simulants and the retort conditions used were 3% acetic acid for 1 h at 100 °C and 10% ethanol for 1 h at 130 °C. The highest migration level seen for melamine into simulant was 332 µg kg⁻¹. There was no detectable migration of the melamine analogues cyanuric acid (<1 µg kg⁻¹) or ammelide (<5 µg kg⁻¹) from any sample. Twelve of the thirteen samples released no detectable ammeline (<5 µg kg⁻¹) but the coating giving the highest release of melamine did also release ammeline at 8 µg kg⁻¹ with the higher of the two process temperatures used. Migration experiments into food simulant and foods themselves were then conducted using two experimental coatings made using amino-based cross-linking resins. Coated metal panels were exposed to the food simulant 10% (v/v) aqueous ethanol and to three foodstuffs under a range of time and temperature conditions both in the laboratory and in a commercial food canning facility using proprietary time and temperature conditions. The highest migration into a food was 152 µg kg⁻¹ from the first coating processed for a long time at a moderate sterilisation temperature. The highest migration into simulant was also from this coating at 220 µg kg⁻¹ when processed at 134 °C for 60 min, dropping to 190 µg k⁻¹ when processed at 123 °C for 70 min. Migration from the second coating was quite uniformly two to three times lower under all tests. These migration results were significantly higher than the levels of melamine extractable using 95% ethanol at room temperature. The experiments show that commercial canning and retorting

  13. The binding of echinomycin to deoxyribonucleic acid.

    PubMed Central

    Wakelin, S P; Waring, M J

    1976-01-01

    Echinomycin is a peptide antibiotic which binds strongly to double-helical DNA up to a limit of approximately one molecule per five base-pairs. There is no detectable interaction with rRNA and only extremely feeble non-specific interaction with poly(rA)-poly(rU). Heat denaturation of DNA greatly decreases the binding, and similarly limited interaction is observed with naturally occurring single-stranded DNA. Association constants for binding to nine double-helical DNA species from different sources are presented; they vary by a factor of approximately 10, but are not simply related to the gross base composition. The interaction with DNA is ionic-strength-dependent, the binding constant falling by a factor of 4 when the ionic strength is raised from 0.01 to 0.10mol/litre. From the effect of temperature on the association constant for calf thymus DNA, the enthalpy of interaction is calculated to be about -13kJ/mol (-3kcal/mol). Binding of echinomycin persists in CsCl gradients and the buoyant density of nicked bacteriophage PM2 DNA is decreased by 25 mg/ml. Echinomycin interacts strongly with certain synthetic poly-deoxynucleotides, the binding constant decreasing in the order poly(dG)-poly(dC) greater than poly(dG-dC) greater than poly(dA-dT). For the latter two polymers the number of base-pairs occluded per bound antibiotic molecule is calculated to be three, whereas for poly(dG)-poly(dC) it is estimated to be four to five. Poly(dA)-poly(dT) and poly(dI)-poly(dC) interact only very weakly with the antibiotic. Poly(dI-dC) interacts to a slightly greater extent, but the binding curve is quite unlike that seen with the three strongly binding synthetic polynucleotides. Echinomycin affects the supercoiling of closed circular duplex bacteriophage PM2 DNA in the characteristic fashion of intercalating drugs. At low ionic strength the unwinding angle is almost twice that of ethidium. Likewise the extension of the helix, determined from changes in the viscosity of rod

  14. In vitro cytotoxicity of injectable and biodegradable poly(propylene fumarate)-based networks: unreacted macromers, cross-linked networks, and degradation products.

    PubMed

    Timmer, Mark D; Shin, Heungsoo; Horch, R Adam; Ambrose, Catherine G; Mikos, Antonios G

    2003-01-01

    This study evaluates the in vitro biocompatibility of an injectable and biodegradable polymeric network based on poly(propylene fumarate) (PPF) and the cross-linking agent PPF-diacrylate (PPF-DA). Using a methyl tetrazolium (MTT) assay, the effect of the concentrations of PPF and PPF-DA on the cytotoxicity of its unreacted macromers, cross-linked networks, and degradation products was examined. The influence of network structure properties on cell viability and attachment to the cross-linked material was also investigated. The unreacted macromers exhibited a time- and dose-dependent cytotoxic response that increased with more PPF-DA in the mixture. Conversely, the cross-linked networks formed with more PPF-DA did not demonstrate an adverse response because increases in conversion and cross-linking density prevented the extraction of toxic products. Fibroblast attachment was observed on the PPF/PPF-DA networks with the highest double bond conversions. The degradation products, obtained from the complete breakdown of the networks in basic conditions, displayed a dose-dependent cytotoxic response. These results show that there are concerns regarding the biocompatibility of injectable, biodegradable PPF/PPF-DA networks but also sheds light onto potential mechanisms to reduce the cytotoxic effects.

  15. Surface Charges and Shell Crosslinks Each Play Significant Roles in Mediating Degradation, Biofouling, Cytotoxicity and Immunotoxicity for Polyphosphoester-based Nanoparticles

    PubMed Central

    Elsabahy, Mahmoud; Zhang, Shiyi; Zhang, Fuwu; Deng, Zhou J.; Lim, Young H.; Wang, Hai; Parsamian, Perouza; Hammond, Paula T.; Wooley, Karen L.

    2013-01-01

    The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications. PMID:24264796

  16. Surface charges and shell crosslinks each play significant roles in mediating degradation, biofouling, cytotoxicity and immunotoxicity for polyphosphoester-based nanoparticles.

    PubMed

    Elsabahy, Mahmoud; Zhang, Shiyi; Zhang, Fuwu; Deng, Zhou J; Lim, Young H; Wang, Hai; Parsamian, Perouza; Hammond, Paula T; Wooley, Karen L

    2013-11-22

    The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications.

  17. Surface Charges and Shell Crosslinks Each Play Significant Roles in Mediating Degradation, Biofouling, Cytotoxicity and Immunotoxicity for Polyphosphoester-based Nanoparticles

    NASA Astrophysics Data System (ADS)

    Elsabahy, Mahmoud; Zhang, Shiyi; Zhang, Fuwu; Deng, Zhou J.; Lim, Young H.; Wang, Hai; Parsamian, Perouza; Hammond, Paula T.; Wooley, Karen L.

    2013-11-01

    The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications.

  18. Polymer electrolyte based on crosslinked poly(glycidyl methacrylate) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

    SciTech Connect

    Fei, Beatrice Wong Chui; Hanifah, Sharina Abu; Ahmad, Azizan; Hassan, Nur Hasyareeda

    2015-09-25

    Polymer electrolytes based on crosslinked poly(glycidyl methacrylate) as polymer host and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) as incorporated salt were prepared by in-situ photopolymerization technique. The complexes with different mass ratio of glycidyl methacrylate (GMA) monomer to BmimTFSI were investigated. The ionic conductivity of the polymer electrolyte was increased and reach the highest value of 7.50 × 10{sup −4} S cm{sup −1} at the ratio of 3:7 (GMA: BmimTFSI). The interaction between the polymer host and ionic liquid was proved by Attenuated Total Reflectance-Fourier Transformation Infra-Red Spectroscopy (ATR-FTIR). Meanwhile, the X-ray diffraction analysis shows the amorphousity of the polymer electrolyte film increase with the ionic liquid ratio.

  19. Translational termination in Escherichia coli: three bases following the stop codon crosslink to release factor 2 and affect the decoding efficiency of UGA-containing signals.

    PubMed Central

    Poole, E S; Major, L L; Mannering, S A; Tate, W P

    1998-01-01

    The observations that the Escherichia coli release factor 2 (RF2) crosslinks with the base following the stop codon (+4 N), and that the identity of this base strongly influences the decoding efficiency of stop signals, stimulated us to determine whether there was a more extended termination signal for RF2 recognition. Analysis of the 3' contexts of the 1248 genes in the E.coli genome terminating with UGA showed a strong bias for U in the +4 position and a general bias for A and against C in most positions to +10, consistent with the concept of an extended sequence element. Site-directed crosslinking occurred to RF2 from a thio-U sited at the +4, +5 and +6 bases following the UGA stop codon but not beyond (+7 to +10). Varying the +4 to +6 bases modulated the strength of the crosslink from the +1 invariant U to RF2. A strong selection bias for particular bases in the +4 to +6 positions of certain E. coli UGANNN termination sites correlated in some cases with crosslinking efficiency to RF2 and in vivo termination signal strength. These data suggest that RF2 may recognise at least a hexanucleotide UGA-containing sequence and that particular base combinations within this sequence influence termination signal decoding efficiency. PMID:9461453

  20. Protein-Sized Bright Fluorogenic Nanoparticles Based on Cross-Linked Calixarene Micelles with Cyanine Corona.

    PubMed

    Shulov, Ievgen; Rodik, Roman V; Arntz, Youri; Reisch, Andreas; Kalchenko, Vitaly I; Klymchenko, Andrey S

    2016-12-19

    The key challenge in the field of fluorescent nanoparticles (NPs) for biological applications is to achieve superior brightness for sizes equivalent to single proteins (3-7 nm). We propose a concept of shell-cross-linked fluorescent micelles, in which PEGylated cyanine 3 and 5 bis-azides form a covalently attached corona on micelles of amphiphilic calixarene bearing four alkyne groups. The fluorescence quantum yield of the obtained monodisperse NPs, with a size of 7 nm, is a function of viscosity and reached up to 15 % in glycerol. In the on-state they are circa 2-fold brighter than quantum dots (QD-585), which makes them the smallest PEGylated organic NPs of this high brightness. FRET between cyanine 3 and 5 cross-linkers at the surface of NPs suggests their integrity in physiological media, organic solvents, and living cells, in which the NPs rapidly internalize, showing excellent imaging contrast. Calixarene micelles with a cyanine corona constitute a new platform for the development of protein-sized ultrabright fluorescent NPs.

  1. Smart nanocomposite hydrogels based on azo crosslinked graphene oxide for oral colon-specific drug delivery

    NASA Astrophysics Data System (ADS)

    Hou, Lin; Shi, Yuyang; Jiang, Guixiang; Liu, Wei; Han, Huili; Feng, Qianhua; Ren, Junxiao; Yuan, Yujie; Wang, Yongchao; Shi, Jinjin; Zhang, Zhenzhong

    2016-08-01

    A safe and efficient nanocomposite hydrogel for colon cancer drug delivery was synthesized using pH-sensitive and biocompatible graphene oxide (GO) containing azoaromatic crosslinks as well as poly (vinyl alcohol) (PVA) (GO-N=N-GO/PVA composite hydrogels). Curcumin (CUR), an anti-cancer drug, was encapsulated successfully into the hydrogel through a freezing and thawing process. Fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy were performed to confirm the formation and morphological properties of the nanocomposite hydrogel. The hydrogels exhibited good swelling properties in a pH-sensitive manner. Drug release studies under conditions mimicking stomach to colon transit have shown that the drug was protected from being released completely into the physiological environment of the stomach and small intestine. In vivo imaging analysis, pharmacokinetics and a distribution of the gastrointestinal tract experiment were systematically studied and evaluated as colon-specific drug delivery systems. All the results demonstrated that GO-N=N-GO/PVA composite hydrogels could protect CUR well while passing through the stomach and small intestine to the proximal colon, and enhance the colon-targeting ability and residence time in the colon site. Therefore, CUR loaded GO-N=N-GO/PVA composite hydrogels might potentially provide a theoretical basis for the treatment of colon cancer with high efficiency and low toxicity.

  2. Fracture Simulation of Highly Crosslinked Polymer Networks: Triglyceride-Based Adhesives

    NASA Astrophysics Data System (ADS)

    Lorenz, Christian; Stevens, Mark; Wool, Richard

    2003-03-01

    The ACRES program at the U. of Delaware has shown that triglyceride oils derived from plants are a favorable alternative to the traditional adhesives. The triglyceride networks are formed from an initial mixture of styrene monomers, free-radical initiators and triglycerides. We have performed simulations to study the effect of physical composition and physical characteristics of the triglyceride network on the strength of triglyceride network. A coarse-grained, bead-spring model of the triglyceride system is used. The average triglyceride consists of 6 beads per chain, the styrenes are represented as a single bead and the initiators are two bead chains. The polymer network is formed using an off-lattice 3D Monte Carlo simulation, in which the initiators activate the styrene and triglyceride reactive sites and then bonds are randomly formed between the styrene and active triglyceride monomers producing a highly crosslinked polymer network. Molecular dynamics simulations of the network under tensile and shear strains were performed to determine the strength as a function of the network composition. The relationship between the network structure and its strength will also be discussed.

  3. Multiblock Copolymer-Based Dual Dynamic Disulfide and Supramolecular Crosslinked Self-Healing Networks.

    PubMed

    An, So Young; Noh, Seung Man; Oh, Jung Kwon

    2017-04-01

    A new multiblock copolymer self-healing strategy is reported that centers on the synthesis of block copolymers designed with different self-healing motifs incorporated into individual blocks. As a proof of concept, a novel pentablock copolymer (ABCBA) consisting of a poly(ethylene glycol) middle block and self-healable symmetric blocks of a polymethacrylate with pendant disulfide linkages and carboxylic acids is synthesized by a combination of consecutive controlled radical polymerization with hydrolytic cleavage. Disulfide exchange reactions of pendant disulfide linkages and metal-ligand interactions of pendant carboxylic acids with ferric ions allow for the formation of dual crosslinked networks with dynamic disulfide and supramolecular crosslinkages. The resultant networks possessing self-healing viscoelasticity enable self-healing on macroscale damages through supramolecular metal-ligand interactions and disulfide exchange reactions at room or moderate temperatures. These preliminary results suggest that the strategy can offer the versatility in the development of multifunctional self-healable materials in dual or multiple self-healable mechanisms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Antimicrobial Properties of Microparticles Based on Carmellose Cross-Linked by Cu2+ Ions

    PubMed Central

    Kejdušová, Martina; Vysloužil, Jakub; Kubová, Kateřina; Celer, Vladimír; Krásna, Magdaléna; Pechová, Alena; Vyskočilová, Věra; Košťál, Vratislav

    2015-01-01

    Carmellose (CMC) is frequently used due to its high biocompatibility, biodegradability, and low immunogenicity for development of site-specific or controlled release drug delivery systems. In this experimental work, CMC dispersions in two different concentrations (1% and 2%) cross-linked by copper (II) ions (0.5, 1, 1.5, or 2.0 M CuCl2) were used to prepare microspheres with antimicrobial activity against Escherichia coli and Candida albicans, both frequently occurring pathogens which cause vaginal infections. The microparticles were prepared by an ionotropic gelation technique which offers the unique possibility to entrap divalent copper ions in a CMC structure and thus ensure their antibacterial activity. Prepared CMC microspheres exhibited sufficient sphericity. Both equivalent diameter and copper content were influenced by CMC concentration, and the molarity of copper (II) solution affected only the copper content results. Selected samples exhibited stable but pH-responsive behaviour in environments which corresponded with natural (pH 4.5) and inflamed (pH 6.0) vaginal conditions. All the tested samples exhibited proven substantial antimicrobial activity against both Gram-negative bacteria Escherichia coli and yeast Candida albicans. Unexpectedly, a crucial parameter for microsphere antimicrobial activity was not found in the copper content but in the swelling capacity of the microparticles and in the degree of CMC surface shrinking. PMID:26090444

  5. Antimicrobial Properties of Microparticles Based on Carmellose Cross-Linked by Cu(2+) Ions.

    PubMed

    Kejdušová, Martina; Vysloužil, Jakub; Kubová, Kateřina; Celer, Vladimír; Krásna, Magdaléna; Pechová, Alena; Vyskočilová, Věra; Košťál, Vratislav

    2015-01-01

    Carmellose (CMC) is frequently used due to its high biocompatibility, biodegradability, and low immunogenicity for development of site-specific or controlled release drug delivery systems. In this experimental work, CMC dispersions in two different concentrations (1% and 2%) cross-linked by copper (II) ions (0.5, 1, 1.5, or 2.0 M CuCl₂) were used to prepare microspheres with antimicrobial activity against Escherichia coli and Candida albicans, both frequently occurring pathogens which cause vaginal infections. The microparticles were prepared by an ionotropic gelation technique which offers the unique possibility to entrap divalent copper ions in a CMC structure and thus ensure their antibacterial activity. Prepared CMC microspheres exhibited sufficient sphericity. Both equivalent diameter and copper content were influenced by CMC concentration, and the molarity of copper (II) solution affected only the copper content results. Selected samples exhibited stable but pH-responsive behaviour in environments which corresponded with natural (pH 4.5) and inflamed (pH 6.0) vaginal conditions. All the tested samples exhibited proven substantial antimicrobial activity against both Gram-negative bacteria Escherichia coli and yeast Candida albicans. Unexpectedly, a crucial parameter for microsphere antimicrobial activity was not found in the copper content but in the swelling capacity of the microparticles and in the degree of CMC surface shrinking.

  6. Constitutive Modeling of Crosslinked Nanotube Materials

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Frankland, S. J. V.; Herzog, M. N.; Gates, T. S.; Fay, C. C.

    2004-01-01

    A non-linear, continuum-based constitutive model is developed for carbon nanotube materials in which bundles of aligned carbon nanotubes have varying amounts of crosslinks between the nanotubes. The model accounts for the non-linear elastic constitutive behavior of the material in terms of strain, and is developed using a thermodynamic energy approach. The model is used to examine the effect of the crosslinking on the overall mechanical properties of variations of the crosslinked carbon nanotube material with varying degrees of crosslinking. It is shown that the presence of the crosslinks has significant effects on the mechanical properties of the carbon nanotube materials. An increase in the transverse shear properties is observed when the nanotubes are crosslinked. However, this increase is accompanied by a decrease in axial mechanical properties of the nanotube material upon crosslinking.

  7. Comparative evaluation of shear compressive bond strength between cross-linked acrylic resin denture base and cross-linked acrylic resin teeth with different modifcations of their ridge lap surfaces.

    PubMed

    Sadar, Leena; Dhume, Swaroop; Maniar, Neena; Prakash Patil, Jeevan; Rane, Prasad; Gandhewar, Mahesh

    2013-09-01

    A major problem commonly observed in denture wearer is the detachment of artifcial tooth/teeth from acrylic denture base. The problem was grave when porcelain teeth used along with the then available denture base materials. The bond formed was purely mechanical and hence debonding of teeth from denture base was a frequent occurrence. Inspite of chemical union between acrylic resin teeth and acrylic denture base material, detachment of teeth particularly anterior teeth is a frequent observation. The objective of the study is to study the effect of change in the surface treatment and surface confguration of ridge lap surface of the teeth on retention of cross-linked acrylic teeth on cross-linked acrylic resin denture base. Sixty specimens were tested for the shear compressive bond strength using instron universal testing machine in KN. Statistical analysis is used. The fndings were analyzed using one-way analysis of variance (ANOVA) and 't' test. Slight modifcation in the ridge lap surface of artifcial teeth alters the strength of the shear compressive bond. Sand papering of ridge lap surfaces improves the shear compressive bond then the one without any modifcation. Maximum shear compressive bond strength can be increased by application of monomer.

  8. recA gene product is responsible for inhibition of deoxyribonucleic acid synthesis after ultraviolet irradiation.

    PubMed Central

    Trgovcević, Z; Petranović, D; Petranović, M; Salaj-Smic, E

    1980-01-01

    Deoxyribonucleic acid synthesis after ultraviolet irradiation was studied in wild-type, uvrA, recB, recA recB, and recA Escherichia coli strains. Inhibition of deoxyribonucleic acid synthesis, which occurs almost immediately after exposing the cells to ultraviolet radiation, depends on the functional gene recA. PMID:6997276

  9. Petite mutation in yeast. II. Isolation of mutants containing mitochondrial deoxyribonucleic acid of reduced size.

    PubMed

    Goldring, E S; Grossman, L I; Marmur, J

    1971-07-01

    A series of petite mutants of Saccharomyces cerevisiae, generated after treatment for various times with ethidium bromide, was isolated, and the mitochondrial deoxyribonucleic acid size for each member was estimated. It was found that, as the treatment time with ethidium bromide was increased, the mitochondrial deoxyribonucleic acid isolated from the petite series was increasingly reduced in size.

  10. Incorporation of Deoxyribonucleic Acid Precursors by T4 Deoxyribonucleic Acid-Protein Complexes Retained on Glass Fiber Filters

    PubMed Central

    Miller, Robert C.; Kozinski, Andrzej W.

    1970-01-01

    Bacteriophage T4 deoxyribonucleic acid (DNA)-protein complexes were retained preferentially on glass fiber filters. DNA polymerase activity in the complex was detected through the incorporation of 3H-labeled DNA precursors. The primer-product DNA hybridized with both phage and Escherichia coli DNA. Density labeling experiments showed that about 30% of incorporated 3H-deoxyadenosine triphosphate was found in DNA which hybridized with phage DNA; this DNA was found to be covalently attached to the primer DNA. PMID:5497903

  11. Reversible bond formation enables the replication and amplification of a crosslinking salen complex as an orthogonal base pair

    NASA Astrophysics Data System (ADS)

    Kaul, Corinna; Müller, Markus; Wagner, Mirko; Schneider, Sabine; Carell, Thomas

    2011-10-01

    The universal genetic code relies on two hydrogen-bonded Watson-Crick base pairs that can form 64 triplet codons. This places a limit on the number of amino acids that can be encoded, which has motivated efforts to create synthetic base pairs that are orthogonal to the natural ones. An additional base pair would result in another 61 triplet codons. Artificial organic base pairs have been described in enzymatic incorporation studies, and inorganic T-Hg-T and C-Ag-C base pairs have been reported to form in primer extension studies. Here, we demonstrate a metal base pair that is fully orthogonal and can be replicated, and can even be amplified by polymerase chain reaction in the presence of the canonical pairs dA:dT and dG:dC. Crystal structures of a dS-Cu-dS base pair inside a polymerase show that reversible chemistry is possible directly inside the polymerase, which enables the efficient copying of the inorganic crosslink. The results open up the possibility of replicating and amplifying artificial inorganic DNA nanostructures by extending the genetic alphabet.

  12. Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

    NASA Astrophysics Data System (ADS)

    Lu, Canhui; Zhang, Xinxing; Zhang, Wei

    2015-05-01

    The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

  13. Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

    SciTech Connect

    Lu, Canhui; Zhang, Xinxing; Zhang, Wei

    2015-05-22

    The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

  14. Heritable and cancer risks of exposures to anticancer drugs: inter-species comparisons of covalent deoxyribonucleic acid-binding agents.

    PubMed

    Vogel, E W; Barbin, A; Nivard, M J; Stack, H F; Waters, M D; Lohman, P H

    1998-05-25

    In the past years, several methodologies were developed for potency ranking of genotoxic carcinogens and germ cell mutagens. In this paper, we analyzed six sub-classes of covalent deoxyribonucleic acid (DNA) binding antineoplastic drugs comprising a total of 37 chemicals and, in addition, four alkyl-epoxides, using four approaches for the ranking of genotoxic agents on a potency scale: the EPA/IARC genetic activity profile (GAP) database, the ICPEMC agent score system, and the analysis of qualitative and quantitative structure-activity and activity-activity relationships (SARs, AARs) between types of DNA modifications and genotoxic endpoints. Considerations of SARs and AARs focused entirely on in vivo data for mutagenicity in male germ cells (mouse, Drosophila), carcinogenicity (TD50s) and acute toxicity (LD50s) in rodents, whereas the former two approaches combined the entire database on in vivo and in vitro mutagenicity tests. The analysis shows that the understanding and prediction of rank positions of individual genotoxic agents requires information on their mechanism of action. Based on SARs and AARs, the covalent DNA binding antineoplastic drugs can be divided into three categories. Category 1 comprises mono-functional alkylating agents that primarily react with N7 and N3 moieties of purines in DNA. Efficient DNA repair is the major protective mechanism for their low and often not measurable genotoxic effects in repair-competent germ cells, and the need of high exposure doses for tumor induction in rodents. Due to cell type related differences in the efficiency of DNA repair, a strong target cell specificity in various species regarding the potency of these agents for adverse effects is found. Three of the four evaluation systems rank category 1 agents lower than those of the other two categories. Category 2 type mutagens produce O-alkyl adducts in DNA in addition to N-alkyl adducts. In general, certain O-alkyl DNA adducts appear to be slowly repaired, or

  15. Cross-linking characterization of polymers based on their optical dispersion utilizing a white-light interferometer

    NASA Astrophysics Data System (ADS)

    Taudt, Ch.; Baselt, T.; Oreski, G.; Hirschl, Ch.; Koch, E.; Hartmann, P.

    2015-05-01

    This work analyses samples of the widely used encapsulant of photovoltaics modules, ethylene vinyl acetate (EVA). The samples were cross-linked using a lamination technique for different curing times (0 - 20 minutes). The cross-linking characterization is done by determinating the material dispersion with the aid of a combined temporal- and spectral domain white-light interferometer. With the proposed technique it was possible to discriminate the differences in crosslinking for the given curing times. One important feature of this approach is the possibility to perform space resolved measurements of the crosslinking state with μm-resolution. Furthermore the paper discusses the mathematical analysis and processing of measurement data and shows a prototype solution for the fast and automated data acquisition for industrial application.

  16. Global Membrane Protein Interactome Analysis using In vivo Crosslinking and Mass Spectrometry-based Protein Correlation Profiling*

    PubMed Central

    Larance, Mark; Kirkwood, Kathryn J.; Tinti, Michele; Brenes Murillo, Alejandro; Ferguson, Michael A. J.; Lamond, Angus I.

    2016-01-01

    We present a methodology using in vivo crosslinking combined with HPLC-MS for the global analysis of endogenous protein complexes by protein correlation profiling. Formaldehyde crosslinked protein complexes were extracted with high yield using denaturing buffers that maintained complex solubility during chromatographic separation. We show this efficiently detects both integral membrane and membrane-associated protein complexes,in addition to soluble complexes, allowing identification and analysis of complexes not accessible in native extracts. We compare the protein complexes detected by HPLC-MS protein correlation profiling in both native and formaldehyde crosslinked U2OS cell extracts. These proteome-wide data sets of both in vivo crosslinked and native protein complexes from U2OS cells are freely available via a searchable online database (www.peptracker.com/epd). Raw data are also available via ProteomeXchange (identifier PXD003754). PMID:27114452

  17. Photochemical Inactivation of Deoxyribonucleic and Ribonucleic Acid Viruses by Chlorpromazine

    PubMed Central

    Hanson, Carl Veith

    1979-01-01

    Chlorpromazine, a widely used tranquilizing drug of the phenothiazine group, was found to be a very potent photochemical inactivator of both deoxyribonucleic acid and ribonucleic acid viruses in the presence of long-wave ultraviolet light (320 to 380 nm). Neither the light alone nor chlorpromazine alone caused any appreciable inactivation. The known chlorpromazine photoreactions with nucleic acids are somewhat similar to those of psoralen (furocoumarin) derivatives. As in the case of the psoralens, chlorpromazine is capable of photoinactivating viruses totally within a few minutes under near-physiological or other gentle conditions. The antiviral effects of the chlorpromazine photoreaction could make it valuable for the development of inactivated viral vaccines as well as for use in the photochemotherapy of viral dermatoses. PMID:464574

  18. Role of deoxyribonucleic acid technology in forensic dentistry.

    PubMed

    Datta, Pankaj; Datta, Sonia Sood

    2012-01-01

    In the last few years, Deoxyribonucleic Acid (DNA) analysis methods have been applied to forensic cases. Forensic dental record comparison has been used for human identification in cases where destruction of bodily tissues or prolonged exposure to the environment has made other means of identification impractical, that is, after fire exposure or mass disaster. Teeth play an important role in identification and criminology, due to their unique characteristics and relatively high degree of physical and chemical resistance. The use of a DNA profile test in forensic dentistry offers a new perspective in human identification. The DNA is responsible for storing all the genetic material and is unique to each individual. The currently available DNA tests have high reliability and are accepted as legal proofs in courts. This article gives an overview of the evolution of DNA technology in the last few years, highlighting its importance in cases of forensic investigation.

  19. Electrical conduction in macroscopically oriented deoxyribonucleic and hyaluronic acid samples

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Lahajnar, Gojmir; Filipič, Cene; Podgornik, Rudolf; Nordenskiöld, Lars; Korolev, Nikolay; Rupprecht, Allan

    2005-04-01

    Measurements of the quasistatic and frequency dependent electrical conductivity below 1 MHz were carried out on wet-spun, macroscopically oriented, calf thymus deoxyribonucleic (DNA) and umbilical cord hyaluronic acid (HA) bulk samples. The frequency dependence of the electrical conductivity in the frequency range of approximately 10-3-106Hz of both materials is surprisingly rather similar. Temperature dependence of the quasistatic electrical conductivity above the low temperature saturation plateau can be well described by the activated Arrhenius law with the activation energy of ≈0.8eV for both DNA and HA. We discuss the meaning of these findings for the possible conduction mechanism in these particular charged polyelectrolytes.

  20. Role of deoxyribonucleic acid technology in forensic dentistry

    PubMed Central

    Datta, Pankaj; Datta, Sonia Sood

    2012-01-01

    In the last few years, Deoxyribonucleic Acid (DNA) analysis methods have been applied to forensic cases. Forensic dental record comparison has been used for human identification in cases where destruction of bodily tissues or prolonged exposure to the environment has made other means of identification impractical, that is, after fire exposure or mass disaster. Teeth play an important role in identification and criminology, due to their unique characteristics and relatively high degree of physical and chemical resistance. The use of a DNA profile test in forensic dentistry offers a new perspective in human identification. The DNA is responsible for storing all the genetic material and is unique to each individual. The currently available DNA tests have high reliability and are accepted as legal proofs in courts. This article gives an overview of the evolution of DNA technology in the last few years, highlighting its importance in cases of forensic investigation. PMID:23087582

  1. Designer reagents for mass spectrometry-based proteomics: clickable cross-linkers for elucidation of protein structures and interactions.

    PubMed

    Sohn, Chang Ho; Agnew, Heather D; Lee, J Eugene; Sweredoski, Michael J; Graham, Robert L J; Smith, Geoffrey T; Hess, Sonja; Czerwieniec, Gregg; Loo, Joseph A; Heath, James R; Deshaies, Raymond J; Beauchamp, J L

    2012-03-20

    We present novel homobifunctional amine-reactive clickable cross-linkers (CXLs) for investigation of three-dimensional protein structures and protein-protein interactions (PPIs). CXLs afford consolidated advantages not previously available in a simple cross-linker, including (1) their small size and cationic nature at physiological pH, resulting in good water solubility and cell-permeability, (2) an alkyne group for bio-orthogonal conjugation to affinity tags via the click reaction for enrichment of cross-linked peptides, (3) a nucleophilic displacement reaction involving the 1,2,3-triazole ring formed in the click reaction, yielding a lock-mass reporter ion for only clicked peptides, and (4) higher charge states of cross-linked peptides in the gas-phase for augmented electron transfer dissociation (ETD) yields. Ubiquitin, a lysine-abundant protein, is used as a model system to demonstrate structural studies using CXLs. To validate the sensitivity of our approach, biotin-azide labeling and subsequent enrichment of cross-linked peptides are performed for cross-linked ubiquitin digests mixed with yeast cell lysates. Cross-linked peptides are detected and identified by collision induced dissociation (CID) and ETD with linear quadrupole ion trap (LTQ)-Fourier transform ion cyclotron resonance (FTICR) and LTQ-Orbitrap mass spectrometers. The application of CXLs to more complex systems (e.g., in vivo cross-linking) is illustrated by Western blot detection of Cul1 complexes including known binders, Cand1 and Skp2, in HEK 293 cells, confirming good water solubility and cell-permeability.

  2. A photochemical crosslinking technology for tissue engineering: enhancement of the physico-chemical properties of collagen-based scaffolds

    NASA Astrophysics Data System (ADS)

    Chan, Barbara P.

    2005-04-01

    Collagen gel is a natural biomaterial commonly used in tissue engineering because of its close resemblance to nature, negligible immunogenecity and excellent biocompatibility. However, unprocessed collagen gel is mechanically weak, highly water binding and vulnerable to chemical and enzymatic attacks that limits its use in tissue engineering in particular tissues for weight-bearing purposes. The current project aimed to strengthen and stabilize collagen scaffolds using a photochemical crosslinking technique. Photochemical crosslinking is rapid, efficient, non-thermal and does not involve toxic chemicals, comparing with other crosslinking methods such as glutaraldehyde and gamma irradiation. Collagen scaffolds were fabricated using rat-tail tendon collagen. An argon laser was used to process the collagen gel after equilibrating with a photosensitizing reagent. Scanning electronic microscope was used to characterize the surface and cross-sectional morphology of the membranes. Physico-chemical properties of the collagen scaffolds such as water-binding capacity, mechanical properties and thermostability were studied. Photochemical crosslinking significantly reduced the water-binding capacity, a parameter inversely proportional to the extent of crosslinking, of collagen scaffolds. Photochemical crosslinking also significantly increased the ultimate stress and tangent modulus at 90% of the rupture strain of the collagen scaffolds. Differential scanning calorimetry analysis showed a significantly higher shrinkage temperature and absence of the denaturation peak during the thermoscan comparing with the controls. This means greater thermostability in the photochemically crosslinked collagen scaffolds. This study demonstrates that the photochemical crosslinking technology is able to enhance the physicochemical propterties of collagen scaffolds by strengthening, stabilizing and controlling the swelling ratio of the collagen scaffolds so as to enable their use for tissue

  3. DNA-protein crosslinks processed by nucleotide excision repair and homologous recombination with base and strand preference in E. coli model system.

    PubMed

    Fang, Qingming

    2013-01-01

    Bis-electrophiles including dibromoethane and epibromohydrin can react with O(6)-alkylguanine-DNA alkyltransferase (AGT) and form AGT-DNA crosslinks in vitro and in vivo. The presence of human AGT (hAGT) paradoxically increases the mutagenicity and cytotoxicity of bis-electrophiles in cells. Here we establish a bacterial system to study the repair mechanism and cellular responses to DNA-protein crosslinks (DPCs) in vivo. Results show that both nucleotide excision repair (NER) and homologous recombination (HR) pathways can process hAGT-DNA crosslinks with HR playing a dominant role. Mutation spectra show that HR has no strand preference but NER favors processing of the DPCs in the transcribed strand; UvrA, UvrB and Mfd can interfere with small size DPCs but only UvrA can interfere with large size DPCs in the transcribed strand processed by HR. Further, we found that DPCs at TA deoxynucleotide sites are very inefficiently processed by NER and the presence of NER can interfere with these DNA lesions processed by HR. These data indicate that NER and HR can process DPCs cooperatively and competitively and NER processes DPCs with base and strand preference. Therefore, the formation of hAGT-DNA crosslinks can be a plausible and specific system to study the repair mechanism and effects of DPCs precisely in vivo.

  4. Fabrication and characterization of a self-crosslinking chitosan hydrogel under mild conditions without the use of strong bases.

    PubMed

    Xu, Yongxiang; Han, Jianmin; Lin, Hong

    2017-01-20

    Self-crosslinking chitosan hydrogels are a highly suitable material for biomedical applications owing to their biodegradability and biocompatibility. However, strong bases, such as sodium hydroxide, which are often used in the preparation of such hydrogels, are known to affect biocompatibility and even destroy the bioactive factors or drug payload of the hydrogel. In the present study, strong bases were replaced by sodium chloride (NaCl) and phosphate buffer saline (PBS, pH=7.4), which were used as gelling solutions for hydrogel fabrication via the freeze-melting-neutralization method. Non-cytotoxicity was showed in MTT assay for hydrogel. Our findings suggest that hydrogel microstructure and physical properties may be adjusted by modifying parameters, such as concentration, temperature, and pH, during the gelling process. Furthermore, the present hydrogel was found to exhibit pH-and ionic strength-responsive properties and may be utilized as a stimulus-responsive material for biomedical applications such as controlled drug release.

  5. Endonuclease from Micrococcus luteus Which Has Activity Toward Ultraviolet-Irradiated Deoxyribonucleic Acid: Its Action on Transforming Deoxyribonucleic Acid

    PubMed Central

    Setlow, R. B.; Setlow, Jane K.; Carrier, W. L.

    1970-01-01

    An endonuclease purified from Micrococcus luteus makes single-strand breaks in ultraviolet (UV)-irradiated, native deoxyribonucleic acid (DNA). The purified endonuclease is able to reactivate UV-inactivated transforming DNA of Haemophilus influenzae, especially when the DNA is assayed on a UV-sensitive mutant of H. influenzae. After extensive endonuclease action, there is a loss of transforming DNA when assayed on both UV-sensitive and -resistant cells. The endonuclease does not affect unirradiated DNA. The results indicate that the endonuclease function is involved in the repair of biological damage resulting from UV irradiation and that the UV-sensitive mutant is deficient in this step. We interpret the data as indicating that the various steps in the repair of DNA must be well coordinated if repair is to be effective. PMID:4314478

  6. Application of Silica-Based Hyper-Crosslinked Sulfonate-Modified Reversed Stationary Phases for Separating Highly Hydrophilic Basic Compounds

    PubMed Central

    Luo, Hao; Ma, Lianjia; Paek, Changyub; Carr, Peter W.

    2008-01-01

    The separation and determination of hydrophilic basic compounds are of great importance in many fields including clinical and biological research, pharmaceutical development and forensic analysis. However, the most widely used analytical separation technique in these disciplines, reversed-phase liquid chromatography (RPLC), usually does not provide sufficient retention for several of the important classes of highly hydrophilic basic compounds including catecholamines, many drug metabolites and many drugs of abuse. Commonly eluents having little or no organic modifier and/or strong ion pairing agents must be used to achieve sufficient retention and separation. Use of highly aqueous eluents can lead to column failure by dewetting, resulting in poor retention, selectivity, reproducibility and slow recovery of performance. The use of a strong ion pairing agent to increase retention renders the separation incompatible with mass spectrometric detection and complicates preparative separations. This paper describes the successful applications of a novel type of silica-based, hyper-crosslinked, sulfonate-modified reversed stationary phase, denoted as −SO3-HC-C8-L, for the separation of highly hydrophilic cations and related compounds by a hydrophobically assisted cation-exchange mechanism. Compared to conventional reversed-phases, the −SO3-HC-C8-L phase showed significantly improved retention and separation selectivity. Concurrently, due to the presence of both cation-exchange and reversed-phase retention mechanisms and the high acid stability of hyper-crosslinked phases, the separation can be optimized by changing the type or concentration of ionic additive or organic modifier, and by varying the column temperature. In addition, gradients generated by programming the concentration of either the ionic additive or the organic modifier can be applied to reduce the analysis time without compromising resolution. Furthermore, remarkably different chromatographic

  7. Resist surface crosslinking using amine-based reactive rinses to mitagate pattern collapse in thin film lithography

    NASA Astrophysics Data System (ADS)

    Yeh, Wei-Ming; Lawson, Richard A.; Tolbert, Laren M.; Henderson, Clifford L.

    2012-03-01

    As the semiconductor industry continues to push to smaller critical dimensions, pattern collapse during lithographic processing caused by unbalanced capillary forces during the final rinse and drying process has become an important problem that can limit the practical resolution of a resist material to feature sizes larger than its intrinsic resolution limit. One of the primary modes of pattern collapse is via elastoplastic pattern deformation which is strongly related to the mechanical properties of the resist. One approach to mitigating such collapse problems is to enhance the mechanical properties of the resist features. Since such modification of resist physical properties for pattern collapse purposes is difficult to achieve through modified formulation of the resist itself (i.e. due to the complex set of requirements that a resist must satisfy and the complex set of physical and chemical phenomena that underlie the imaging processing itself), we have pursued an alternative strategy for improving the resist mechanical properties after features are developed in the film but before they are rinsed and dried. The family of techniques being developed in this work function through the use of aqueous compatible reactive rinse solutions that can be applied to developed resist features while they are wet during normal rinse processing on a track system. By applying these techniques during the rinse process, the resist features can be strengthened before they are subjected to significant capillary forces during the final drying step. In this work, the use of diamine compounds to reactively crosslink the surface of resists containing carboxylic acid groups through formation of amide bonds using carbodiimide chemistry has been explored. One advantage of this approach is that it is an aqueous process that should be easily compatible with high volume, track-based lithographic processes. Contact angle studies and x-ray photoelectron spectroscopy (XPS) were used to

  8. Self-assembled ternary complexes of neutral liposomes, deoxyribonucleic acid, and bivalent metal cations. Promising vectors for gene transfer?

    NASA Astrophysics Data System (ADS)

    Bruni, P.; Pisani, M.; Amici, A.; Marchini, C.; Montani, M.; Francescangeli, O.

    2006-02-01

    By means of synchrotron x-ray diffraction we demonstrate the self-assembled formation of the neutral ternary dioleoyl-phosphatidylcholine-deoxyribonucleic acid (plasmid)-Me2+ (Me=Ca and Mn) complexes in the liquid-crystalline Lα phase. We also report an attempt of an in vitro transfection on mouse fibroplast NIH 3T3 cell lines, which shows the capability of these complexes to transfect DNA. Based on the reported results, efficient encapsulation of DNA plasmids in these ternary neutral complexes may represent an important alternative to current systemic gene approaches.

  9. Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent.

    PubMed

    Seligra, Paula González; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-03-15

    Biodegradable and non-retrogradable starch-glycerol based films were obtained using citric acid (CA) as crosslinking agent at 75°C. This material allowed decreasing water vapor permeability (WVP) more than 35%, remained amorphous for at least 45 days as a result of the network formed by the CA that avoided starch retrogradation and maintained the degradability in compost, occurring only six days after the films without citric acid. A simulation of the gelatinization process of starch-glycerol with and without CA, using a differential thermal analysis device, showed that the system with CA completed the gelatinization 5°C before than the other and, CA first reacted with glycerol and then starch-glycerol-CA reaction occurred. The temperature at which the gelatinization process was carried out was critical to obtain the best results. An increase of gelatinization process temperature at 85°C in system with CA, led to a worsening on WVP and its integrity after a swelling process with dimethylsulphoxide (DMSO), compared to the films processed at 75°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Nanomechanical properties of mineralised collagen microfibrils based on finite elements method: biomechanical role of cross-links.

    PubMed

    Barkaoui, Abdelwahed; Hambli, Ridha

    2014-01-01

    Hierarchical structures in bio-composites such as bone tissue have many scales or levels and synergic interactions between the different levels. They also have a highly complex architecture in order to fulfil their biological and mechanical functions. In this study, a new three-dimensional (3D) model based on the finite elements (FEs) method was used to model the relationship between the hierarchical structure and the properties of the constituents at the sub-structure scale (mineralised collagen microfibrils) and to investigate their apparent nanomechanical properties. The results of the proposed FE simulations show that the elastic properties of microfibrils depend on different factors such as the number of cross-links, the mechanical properties and the volume fraction of phases. The results obtained under compression loading at a small deformation < 2% show that the microfibrils have a Young's modulus (Ef) ranging from 0.4 to 1.16 GPa and a Poisson's ratio ranging from 0.26 to 0.3. These results are in excellent agreement with experimental data (X-ray, AFM and MEMS) and molecular simulations.

  11. Adsorption of nitrate from aqueous solution by magnetic amine-crosslinked biopolymer based corn stalk and its chemical regeneration property.

    PubMed

    Song, Wen; Gao, Baoyu; Xu, Xing; Wang, Fang; Xue, Nan; Sun, Shenglei; Song, Wuchang; Jia, Ruibao

    2016-03-05

    A novel adsorbent of magnetic amine-crosslinked biopolymer based corn stalk (MAB-CS) was synthesized and used for nitrate removal from aqueous solution. The characters and adsorption mechanisms of this bio-adsorbent were determined by using VSM, TGA, XRD, SEM, TEM, FT-IR and XPS, respectively. The results revealed that the saturated magnetization of MAB-CS reached 6.25 emu/g. Meanwhile, the studies of various factors indicated that this novel magnetic bio-adsorbent performed well over a considerable wide pH range of 6.0 ∼ 9.0, and the presence of PO4(3-) and SO4(2-) would markedly decrease the nitrate removal efficiency. Furthermore, the nitrate adsorption by MAB-CS perfectly fitted the Langmuir isotherm model (R(2)=0.997-0.999) and pseudo second order kinetic model (R(2)=0.953-0.995). The calculated nitrate adsorption capacity of MAB-CS was 102.04 mg/g at 318 K by Langmuir model, and thermodynamic study showed that nitrate adsorption is an spontaneous endothermic process. The regeneration experiments indicated its merit of regeneration and stability with the recovery efficient of 118 ∼ 147%. By integrating the experimental results, it was found that the removal of nitrate was mainly via electrostatic attraction and ion exchange. And this novel bio-adsorbent prepared in this work could achieve effective removal of nitrate and rapid separation from effluents simultaneously.

  12. HPMC-based gastroretentive dual working matrices coated with Ca(+2) ion crosslinked alginate-fenugreek gum gel membrane.

    PubMed

    Bera, Hriday; Gaini, Chakravarthy; Kumar, Sanoj; Sarkar, Srimanta; Boddupalli, Shashank; Ippagunta, Sohitha Reddy

    2016-10-01

    Novel alginate-fenugreek gum (FG) gel membrane coated hydroxypropylmethylcellulose (HPMC) based matrix tablets were developed for intragastric quetiapine fumarate (QF) delivery by combining floating and swelling mechanisms. The effects of polymer blend ratios [HPMC K4M:HPMC E15] and citric acid contents on time taken for 50% drug release (t50%, min) and drug release at 8h (Q8h, %) were studied to optimize the core tablets by 3(2) factorial design. The optimized tablets (F-O) exhibited t50% of 247.67±3.51min and Q8h of 71.11±0.32% with minimum errors in prediction. The optimized tablets were coated with Ca(+2) ions crosslinked alginate-FG gel membrane by diffusion-controlled interfacial complexation technique. The biopolymeric-coated optimized matrices exhibited superior buoyancy, preferred swelling characteristics and slower drug release rate. The drug release profiles of the QF-loaded uncoated and coated optimized matrices were best fitted in Korsmeyer-Peppas model with anomalous diffusion driven mechanism. The uncoated and coated tablets containing QF were also characterized for drug-excipients compatibility, thermal behaviour and surface morphology by FTIR, DSC and SEM analyses, respectively. Thus, the newly developed alginate-FG gel membrane coated HPMC matrices are appropriate for intragastric delivery of QF over a prolonged period of time with greater therapeutic benefits. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. 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.

  14. Robust, tough and anti-fatigue cationic latex composite hydrogels based on dual physically cross-linked networks.

    PubMed

    Gu, Song; Duan, Lijie; Ren, Xiuyan; Gao, Guang Hui

    2017-04-15

    Dual physically cross-linked hydrogels, which are triggered by cationic latexes as hydrophobic association and ionic crosslinking centers, were easily fabricated via a one-pot in situ polymerization method. First, the hydrophobic alkyl chains of hydrophobic monomers are adsorbed on the surface of latex microspheres and stabilized in the presence of surfactants, forming hydrophobic association centers as the first physical crosslinking points. Meanwhile, the anionic sulfate radicals dissociated by persulphate are attracted towards the cationic molecular chains of latex microspheres through ionic interactions, forming the secondary physical crosslinking centers, and initiate the copolymerization between acrylamide and hydrophobic vinyl monomers. The fabricated hydrogel exhibited high tensile strength of 1.32MPa, a remarkable toughness of 4.53MJm(-3), excellent self-recovery properties and fatigue resistance. Therefore, the current work provides a promising strategy for designing novel hydrogels via multiple physical interactions and devoid of any chemical crosslinking. The novel design of hydrogels can enhance their mechanical properties and expand their biomedical applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. High-Strength, Tough, Fatigue Resistant, and Self-Healing Hydrogel Based on Dual Physically Cross-Linked Network.

    PubMed

    Gong, Zhengyu; Zhang, Guoping; Zeng, Xiaoliang; Li, Jinhui; Li, Gang; Huang, Wangping; Sun, Rong; Wong, Chingping

    2016-09-14

    Hydrogels usually suffer from low mechanical strength, which largely limit their application in many fields. In this Research Article, we prepared a dual physically cross-linked hydrogel composed of poly(acrylamide-co-acrylic acid) (PAM-co-PAA) and poly(vinyl alcohol) (PVA) by simple two-steps methods of copolymerization and freezing/thawing. The hydrogen bond-associated entanglement of copolymer chains formed as cross-linking points to construct the first network. After being subjected to the freezing/thawing treatment, PVA crystalline domains were formed to serve as knots of the second network. The hydrogels were demonstrated to integrate strength and toughness (1230 ± 90 kPa and 1250 ± 50 kJ/m(3)) by the introduction of second physically cross-linked network. What̀s more, the hydrogels exhibited rapid recovery, excellent fatigue resistance, and self-healing property. The dynamic property of the dual physically cross-linked network contributes to the excellent energy dissipation and self-healing property. Therefore, this work provides a new route to understand the toughness mechanism of dual physically cross-linked hydrogels, hopefully promoting current hydrogel research and expanding their applications.

  16. Cross-linked, biodegradable, cytocompatible salicylic acid based polyesters for localized, sustained delivery of salicylic acid: an in vitro study.

    PubMed

    Chandorkar, Yashoda; Bhagat, Rajesh K; Madras, Giridhar; Basu, Bikramjit

    2014-03-10

    In order to suppress chronic inflammation while supporting cell proliferation, there has been a continuous surge toward development of polymers with the intention of delivering anti-inflammatory molecules in a sustained manner. In the above backdrop, we report the synthesis of a novel, stable, cross-linked polyester with salicylic acid (SA) incorporated in the polymeric backbone and propose a simple synthesis route by melt condensation. The as-synthesized polymer was hydrophobic with a glass transition temperature of 1 °C, which increases to 17 °C upon curing. The combination of NMR and FT-IR spectral techniques established the ester linkages in the as-synthesized SA-based polyester. The pH-dependent degradation rate and the rate of release of salicylic acid from the as-synthesized SA-based polymer were studied at physiological conditions in vitro. The polyester underwent surface erosion and exhibited linear degradation kinetics in which a change in degradation rate is observed after 4-10 days and 24% mass loss was recorded after 4 months at 37 °C and pH 7.4. The delivery of salicylic acid also showed a similar change in slopes, with a sustained release rate of 3.5% in 4 months. The cytocompatibility studies of these polyesters were carried out with C2C12 murine myoblast cells using techniques like MTT assay and flow cytometry. Our results strongly suggest that SA-based polyester supports cell proliferation for 3 days in culture and do not cause cell death (<7%), as quantified by propidium iodide (PI) stained cells. Hence, these polyesters can be used as implant materials for localized, sustained delivery of salicylic acid and have applications in adjuvant cancer therapy, chronic wound healing, and as an alternative to commercially available polymers like poly(lactic acid) and poly(glycolic acid) or their copolymers.

  17. A homogeneous hemin/G-quadruplex DNAzyme based turn-on chemiluminescence aptasensor for interferon-gamma detection via in-situ assembly of luminol functionalized gold nanoparticles, deoxyribonucleic acid, interferon-gamma and hemin.

    PubMed

    Jiang, Jie; He, Yi; Yu, Xiuxia; Zhao, Jinyang; Cui, Hua

    2013-08-12

    A homogeneous hemin/G-quadruplex DNAzyme (HGDNAzyme) based turn-on chemiluminescence aptasensor for interferon-gamma (IFN-γ) detection is developed, via dynamic in-situ assembly of luminol functionalized gold nanoparticles (lum-AuNPs), DNA, IFN-γ and hemin. The G-quadruplex oligomer of the HGDNAzyme was split into two halves, which was connected with the complementary sequence of P1 (IFN-γ-binding aptamer) to form the oligonucleotide P2. P2 hybridized with IFN-γ-binding aptamer and meanwhile assembled onto lum-AuNPs through biotin-streptavidin specific interaction. When IFN-γ was recognized by aptamer, P2 was released into the solution. The two lateral portions of P2 combined with hemin to yield the catalytic hemin/G-quadruplex DNAzyme, which amplified the luminol oxidation for a turn-on chemiluminescence signaling. Based on this strategy, the homogeneous aptasensor enables the facile detection of IFN-γ in a range of 0.5-100 nM. Moreover, the aptasensor showed high sensitivity (0.4 nM) and satisfactory specificity, pointing to great potential applications in clinical analysis. Copyright © 2013. Published by Elsevier B.V.

  18. Unambiguous typing of canine adenovirus isolates by deoxyribonucleic acid restriction-endonuclease analysis.

    PubMed Central

    Assaf, R; Marsolais, G; Yelle, J; Hamelin, C

    1983-01-01

    Viral deoxyribonucleic acid extracted from a limited number of cells infected with canine adenovirus type 1 or type 2 was cleaved with several restriction endonucleases. Agarose gel electrophoresis of the limit digests showed stable differences between the canine adenovirus type 1 and type 2 cleavage patterns. Rapid and accurate typing of large numbers of clinical isolates may thus be done by deoxyribonucleic acid restriction-endonuclease analysis. Images Fig. 1. Fig. 2. PMID:6321002

  19. Optical laser cross-link in space-based systems used for satellite communications

    NASA Astrophysics Data System (ADS)

    Panahi, Allen; Kazemi, Alex A.

    2010-04-01

    Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept to fruition in civilian and government non-classified projects. Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Laser Communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. This paper will focus on the requirements of the space-based lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space communications. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. Also discussed are the critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful inter-satellite communications system.

  20. Positive-tone dry-develop resist based on crosslinking a phenolic resin

    NASA Astrophysics Data System (ADS)

    MacDonald, Scott A.; Larson, Carl E.; Schlosser, Hubert; Brock, Phillip J.; Clecak, Nicholas J.; Frechet, Jean M. J.

    1993-09-01

    We have previously shown that a copolymer of p-hydroxstyrene and p-acetoxymethylstyrene can be used as a sensitive deep UV resist. In that study we demonstrated that a formulation of this copolymer and an onium salt could be exposed, baked and developed in aqueous base to yield a high resolution negative tone relief image. In this paper we discuss a gas phase silylation process that converts this negative tone solvent-developable resist system into a positive tone dry-developable resist system. We have used an FT-IR microscope, coupled to a motorized X-Y stage, to study the silylation process as a function of UV exposure dose and silylation processing parameters. By altering the copolymer ratio, we found that resist contrast increased when the amount of acetoxymethylstyrene increased. This resist system and dry develop process were used to print 0.35 micrometers images at a DUV dose of approximately 25 mJ/cm2.

  1. Probing the Selectivity and Protein•Protein Interactions of a Non-Reducing Fungal Polyketide Synthase Using Mechanism-Based Crosslinkers

    PubMed Central

    Bruegger, Joel; Haushalter, Bob; Vagstad, Anna; Shakya, Gaurav; Mih, Nathan; Townsend, Craig A.; Burkart, Michael D.; Tsai, Shiou-Chuan

    2013-01-01

    SUMMARY Protein•protein interactions, which often involve interactions between an acyl carrier protein (ACP) and its partner enzymes, are important for coordinating polyketide biosynthesis. However, the nature of such interactions is not well understood, especially in the fungal non-reducing polyketide synthases (NR-PKSs) that biosynthesize toxic and pharmaceutically important polyketides. Here, we employ a mechanism-based crosslinker to successfully probe ACP and ketosynthase (KS) domain interactions in NR-PKSs. We found that crosslinking efficiency is closely correlated with the strength of ACP•KS interactions, and that KS demonstrates strong starter unit selectivity. We further identified positively charged surface residues by KS mutagenesis, which mediate key interactions with the negatively-charged ACP surface. Such complementary/matching contact pairs can serve as “adapter surfaces” for future efforts to generate new polyketides using NR-PKSs. PMID:23993461

  2. Deformation-strength properties in the tension of cross-linked polymers based on mixtures of epoxide and epoxy-oligoether oligomers

    SciTech Connect

    Markevich, M.A.

    1992-05-01

    Epoxy network polymers are finding increasing use as adhesives, sealing and impregnating compounds, binders in composites and filled materials, protective and insulating coatings in the radio and electronics industries, and other applications. Broad use reflects their high strength and ductility properties, good electric and dielectic properties, elasticity, ability to adhere to a wide range of materials, chemical stability, etc. However, one of the main shortcomings of epoxide cross-linked polymers is their low fracture strain in tension. Their low impact strength is also a problem. To improve the strength and ductility properties of cross-linked epoxides, use is made of mixtures of oligomers of adherent molecular weights. The oligomers may be either of the same chemical nature or may have different molecular structures and functionalities. In the present article, the author reports the results of a study of the strength and ductility properties of mixtures of epoxide polygomers based on diphenylolpropane (E-40, molecular weight 600) and epichlorohydrin (Oksilin-5, molecular weight 2200) coated with diethylenetriamine. The composition of the mixtures is varied broadly in the study. The choice of an epoxidized oligoether was dictated by the fact that cross-linked polymers based on it should exhibit greater elongation. Moreover, the use of mixtures of epoxide oligomers of different types makes it possible to modify both the microscopic (density, free volume, temperature transitions, etc.) and macroscopic properties (Young`s modulus elongation, short- and long-term strength, impact strength) of cross linked polymers.

  3. Space-based laser cross-link systems used in satellite communications

    NASA Astrophysics Data System (ADS)

    Panahi, Allen; Kazemi, Alex A.

    2009-05-01

    Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept to fruition in civilian and government-non classified projects. Laser Communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. This paper will focus on the requirements of the spacebased lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space communications. Also discussed are the critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful inter-satellite communications system.

  4. Biodegradable and injectable in situ cross-linking chitosan-hyaluronic acid based hydrogels for postoperative adhesion prevention.

    PubMed

    Li, Ling; Wang, Ning; Jin, Xun; Deng, Rui; Nie, Shihong; Sun, Lu; Wu, Qinjie; Wei, Yuquan; Gong, Changyang

    2014-04-01

    Postsurgical peritoneal adhesions are very common and serious complication after surgery. Biodegradable and injectable hydrogels derived from natural polysaccharides are ideal biomaterials for prevention of postoperative adhesion. In this work, we report a class of injectable, biodegradable, and non-toxic hydrogel derived from N, O-carboxymethyl chitosan (NOCC) and aldehyde hyaluronic acid (A-HA), without requirement of any chemical linkers or radiant light sources. NOCC was prepared by introducing carboxymethyl groups to the N-position and the O-position of chitosan, and A-HA was prepared using periodate oxidation method. The gelation is attributed to the Schiff base between the amino groups of NOCC and aldehyde groups in A-HA, and the hydrogel precursors cross-linked to form a flexible hydrogel. NOCC, A-HA, and NOCC/A-HA hydrogel extract exhibited very low cytotoxicity and hemolysis, and the acute toxicity tests showed that the hydrogel was non-toxic. Besides, the highly porous three-dimensional hydrogel can supported the growth and proliferation of the cells encapsulated in the hydrogels, but was not favorable for the attachment of fibroblasts to the surface, suggesting that the NOCC/A-HA hydrogel can be developed for adhesion prevention. The hydrogel was susceptible to the lysozyme and can be degraded within 2 weeks in vivo. Furthermore, we employed a rat model of sidewall defect-cecum abrasion to investigate the efficacy of NOCC/A-HA hydrogel in preventing post-operative peritoneal adhesions. A significant reduction of peritoneal adhesion formation was found in the NOCC/A-HA-treated group, compared with commercial hyaluronic acid (HA) hydrogel group and normal saline group. In addition, the potential anti-adhesion mechanism of NOCC/A-HA hydrogel was discussed, which may attribute to the combination of barrier function and bioactivity of NOCC and A-HA. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Absence of Strand Breaks in Deoxyribonucleic Acid Treated with Metronidazole

    PubMed Central

    LaRusso, Nicholas F.; Tomasz, Maria; Kaplan, David; Müller, Miklós

    1978-01-01

    The deoxyribonucleic acid (DNA)-degrading potential of metronidazole was evaluated in vitro by three techniques: determination of melting curve, measurement of viscosity, and centrifugation in neutral or alkaline sucrose gradients. Studies were performed on calf thymus DNA and on 3H-labeled or unlabeled pneumococcal and T7 phage DNA after treatment with metronidazole alone or metronidazole reduced by sodium dithionite in the presence of DNA. This latter process is known to elicit covalent binding of metronidazole to DNA. Reduced or unreduced metronidazole had no effect on the melting properties, viscosity, or sedimentation velocity of the nucleic acids studied. Sodium dithionite alone, however, caused a 25% decrease in the intrinsic viscosity of pneumococcal DNA, and decreased the sedimentation velocity of pneumococcal and T7 phage DNA in both neutral and alkaline sucrose gradients. These data suggest that degradation of DNA is not important in the interaction of metronidazole with nucleic acids, an interaction assumed relevant to the cytotoxic, radiosensitizing, and mutagenic activities of this compound. PMID:626487

  6. A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nano hydroxyapatite, crosslinked with chromium acetate, as scaffold for cartilage regeneration

    NASA Astrophysics Data System (ADS)

    Koushki, N.; Tavassoli, H.; Katbab, A. A.; Katbab, P.; Bonakdar, S.

    2015-05-01

    Polymer scaffolds are applied in the field of tissue engineering as three dimensional structures to organize cells and present stimuli to direct generation of a desired damaged tissue. In situ gelling scaffolds have attracted great attentions, as they are structurally similar to the extra cellular matrix (ECM). In the present work, attempts have been made to design and fabricate a new injectable and crosslinkable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), chromium acetate as crosslink agent and nanocrystalline hydroxyapatite (nHAp) as reinforcing and bioactive agent for repair and regeneration of damaged cartilage. The distinct characteristic of HPAM is the presence of carboxylate anion groups on its backbone which allows to engineer the structure of the hydrogel for the desired bioactivity with appropriate cells differentiation towards both soft and hard (bone) tissues. The synthesized hydrogel exhibited bifunctional behavior which was derived by its biphasic structure in which one phase was loaded with nano hydroxyapatite to provide integration capability by subchondral bones and fix the hydrogel at cartilage defect without a need for suturing. The other phase differentiates the rabbit adipogenic mesenchymal stem cells (MSCs) towards soft tissue. Rheomechanical spectrometry (RMS) was employed to study the kinetic of the gelation including induction time and rate, as well as to measure the ultimate elastic modulus of the optimum crosslinked hydrogel. Surface tension measurement was also performed to tailor the surface characteristics of the gels. In vitro culturing of the cells inside the crosslinked hydrogel revealed high viability and high differentiation of the encapsulated rabbit stem cells, providing that the chromium acetate level was kept below 0.2 wt%. Based on the obtained results, the designed and fabricated biphasic hydrogel exhibited high potential as carrier for the stem cells for cartilage tissue engineering application

  7. Semi-interpenetrating solid polymer electrolyte based on thiol-ene cross-linker for all-solid-state lithium batteries

    NASA Astrophysics Data System (ADS)

    Suk, Jungdon; Lee, Yu Hwa; Kim, Do Youb; Kim, Dong Wook; Cho, Song Yun; Kim, Ji Man; Kang, Yongku

    2016-12-01

    We developed highly promising solid polymer electrolytes (SPEs) based on a novel cross-linker containing star-shaped phosphazene with poly(ethylene oxide) (PEO) branches with very high ionic conductivity (7.6 × 10-4 S cm-1), improved mechanical stability, and good electrochemical stability for all-solid-state lithium batteries. In particular, allyl groups were introduced at the ends of the cross-linker in order to overcome the easy self-polymerization of existing cross-linking acrylate end groups. A novel semi-interpenetrating network (semi-IPN) SPE was prepared by in-situ radical polymerization of a precursor solution containing lithium salt, poly(ethylene glycol) dimethyl ether as a plasticizer, and a mixture of pentaerythritol tetrakis(3-mercaptopropionate) and a synthesized hexakis(allyloxy)cyclotriphosphazene (thiol-ene PAL) as the cross-linker. Batteries employing LiFePO4 as the cathode, lithium foil as the anode, and the SPE thin film as the electrolyte were assembled and tested. At ambient temperature, the initial discharge capacity was 147 mAh/g at 0.1 °C and 132 mAh/g at 0.5 °C, and 97% of the capacity was retained at the 100th cycle. All-solid-state pouch-package lithium cells assembled with the SPEs exhibited stable electrochemical performance, even under a severely wrinkled state. These outstanding properties of SPEs based on thiol-ene PAL demonstrate feasibility for practical battery applications with improved reliability and safety.

  8. Influence of natural and synthetic crosslinking reagents on the structural and mechanical properties of chitosan-based hybrid hydrogels.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M

    2016-10-20

    The objective of this work was to correlate the physical and chemical properties of chitosan/poly(vinyl alcohol)/genipin (CS/PVA/GEN) and chitosan/poly(vinyl alcohol)/glutaraldehyde (CS/PVA/GA) hydrogels with their structural and mechanical responses. In addition, their molecular structures were determined and confirmed using FTIR spectroscopy. The results indicated that the hybrid hydrogels crosslinked with genipin showed similar crystallinity, thermal properties, elongation ratio and structural parameters as those crosslinked with glutaraldehyde. However, it was found that the elastic moduli of the two hybrid hydrogels were slightly different: 2.82±0.33MPa and 2.08±0.11MPa for GA and GEN, respectively. Although the hybrid hydrogels crosslinked with GEN presented a lower elastic modulus, the main advantage is that GEN is five to ten thousand times less cytotoxic than GA. This means that the structural and mechanical properties of hybrid hydrogels crosslinked with GEN can easily be tuned and could have potential applications in the tissue engineering, regenerative medicine, food, agriculture and environmental industries. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Semi-Interpenetrating polymer network hydrogels based on aspen hemicellulose and chitosan: Effect of crosslinking sequence on hydrogel properties

    Treesearch

    Muzaffer Ahmet Karaaslan; Mandla A. Tshabalala; Gisela. Buschle-Diller

    2012-01-01

    Semi-interpenetrating network hydrogel films were prepared using hemicellulose and chemically crosslinked chitosan. Hemicellulose was extracted from aspen by using a novel alkaline treatment and characterized by HPSEC, and consisted of a mixture of high and low molecular weight polymeric fractions. HPLC analysis of the acid hydrolysate of the hemicellulose showed that...

  10. Fabrication of poly(propylene fumarate)-based orthopaedic implants by photo-crosslinking through transparent silicone molds.

    PubMed

    Timmer, Mark D; Carter, Cory; Ambrose, Catherine G; Mikos, Antonios G

    2003-11-01

    This work presents a new molding process for photo-crosslinked, degradable polymeric networks of poly(propylene fumarate) (PPF) and the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA). Transparent room temperature vulcanizing silicone molds were fabricated for parts ranging from simple test coupons to orthopaedic implants. The PPF/PPF-DA resin blend was injected into the cavity and photo-crosslinked as light was transmitted through the mold wall. The volumetric shrinkage, mechanical properties, and the effects of gamma sterilization were reported for molded PPF/PPF-DA networks prepared with varying compositions of the two polymer components. The shrinkage decreased while the mechanical properties displayed a general increasing trend when more of the crosslinking agent was incorporated into the network. Gamma irradiation resulted in an improvement of the mechanical properties. In addition, PPF/PPF-DA replicates of a 70:30 poly(L/DL-lactide) biodegradable fixation plate and a bone allograft interbody fusion spacer were produced to evaluate the performance of PPF/PPF-DA as an orthopaedic implant and allow for a comparison to be made with materials that have been established for clinical use.

  11. Dynamic Cross-Linking of Polymeric Binders Based on Host-Guest Interactions for Silicon Anodes in Lithium Ion Batteries.

    PubMed

    Kwon, Tae-woo; Jeong, You Kyeong; Deniz, Erhan; AlQaradawi, Siham Y; Choi, Jang Wook; Coskun, Ali

    2015-11-24

    We report supramolecular cross-linking of polymer binders via dynamic host-guest interactions between hyperbranched β-cyclodextrin polymer and a dendritic gallic acid cross-linker incorporating six adamantane units for high-capacity silicon anodes. Calorimetric analysis in the solution phase indicates that the given host-guest complexation is a highly spontaneous and enthalpically driven process. These findings are further verified by carrying out gelation experiments in both aqueous and organic media. The dynamic cross-linking process enables intimate silicon-binder interaction, structural stability of electrode film, and controlled electrode-electrolyte interface, yielding enhanced cycling performance. Control experiments using both α, γ-CDp with different cavity sizes and a guest molecule incorporating a single adamantane unit verified that the enhanced cycle life originates from the host-guest interaction between β-cyclodextrin and adamantane. The impact of the dynamic cross-linking is maximized at an optimal stoichiometry between the two components. Importantly, the present investigation proves that the molecular-level tuning of the host-guest interactions can be translated directly to the cycling performance of silicon anodes.

  12. Preparation and characterization of structured hydrogel microparticles based on cross-linked hyperbranched polyglycerol.

    PubMed

    Oudshoorn, Marion H M; Penterman, Roel; Rissmann, Robert; Bouwstra, Joke A; Broer, Dirk J; Hennink, Wim E

    2007-11-06

    The aim of this work was to obtain well-defined HyPG-MA (methacrylated hyperbranched polyglycerol) microparticles with uniform sizes. Therefore, three different preparation methods were evaluated. First, we assessed a micromolding technique using rigid SU-8 (a photoresist based on epoxies) grids. Independent of the surface treatment of the SU-8 grid or the type of polymer used, approximately 50% of the microgels remained attached to the SU-8 grid or broke into smaller particles during the release process in which drying of the gels was followed by a sonication process. Although 90% methacrylate conversion could be obtained, this method has some additional drawbacks as the obtained dried microgels did not rehydrate completely after the drying step. Second, a soft micromolding technique was evaluated using elastomeric PDMS (poly(dimethyl siloxane)) grids. The use of these flexible grids resulted in a high yield (80-90% yield; >90% methacrylate conversion) of microgels with a well-defined size and shape (squares 100 microm x 100 microm x 50 microm or hexagons with Ø 30 microm and a thickness of 20 microm) without the occurrence of water evaporation. However, a number of particles showed a less-defined shape as not all grids could be filled well. The microgels showed restricted swelling, implying that these gels are dimensionally stable. Third, an alternative method referred to as photolithography was evaluated. This method was suitable to tailor accurately the size and shape of HyPG-MA microgels and additionally gained 100% yield. Well-defined HyPG-MA microgels in the size range of 200-1400 microm (thickness of 6, 20, or 50 microm), with a methacrylate conversion of >90%, could easily be prepared by adding an inhibitor (e.g., 1% (w/v) of vitamin C) to the polymer solution to inhibit dark polymerization. Microgels in the size range of 30-100 microm (>90% conversion) could only be obtained when applying the photomask in direct contact with the polymer solution and

  13. Injectable biodegradable polymer composites based on poly(propylene fumarate) crosslinked with poly(ethylene glycol)-dimethacrylate.

    PubMed

    He, S; Yaszemski, M J; Yasko, A W; Engel, P S; Mikos, A G

    2000-12-01

    New injectable, in situ crosslinkable biodegradable polymer composites were investigated consisting of poly(propylene fumarate) (PPF), poly(ethylene glycol)-dimethacrylate (PEG-DMA), and beta-tricalcium phosphate (beta-TCP). We examined the effects of the PEG-DMA/PPF double-bond ratio and beta-TCP content on the crosslinking characteristics of the composites including the maximum crosslinking temperature and the gel point, as well as the properties of the crosslinked composites such as the compressive strength and modulus, and the water-holding capacity. The maximum crosslinking temperature was constant averaging 39.7 degrees C for the composite formulations tested. The gel points varied from 8.0 +/- 1.0 to 12.6 +/- 2.5 min and were not affected by the relative amounts of PEG-DMA. The compressive strength at yield of PEG-DMA/PPF composites without beta-TCP increased from 5.9 +/- 1.0 to 11.2 +/- 2.2 MPa as the double-bond ratio of PEG-DMA/PPF increased from 0.38 to 1.88. An increase in compressive modulus was also observed from 30.2 +/- 3.5 to 58.4 +/- 6.2 MPa for the same range of the PEG-DMA/PPF double-bond ratio. Also, the addition of beta-TCP (33 wt%) enhanced the mechanical properties of all composites. The equilibrium water content of networks without beta-TCP increased from 21.7 +/- 0.2 to 30.6 +/- 0.2% for a double-bond ratio of PEG-DMA/PPF ranging from 0.38 to 1.88. However, the mechanical properties of the swollen composites under compression were smaller than the dry ones. These data demonstrate the feasibility of fabricating injectable biodegradable polymer composites with engineered mechanical properties for orthopedic tissue engineering.

  14. Dehydration of an ethanol/water azeotrope through alginate-DNA membranes cross-linked with metal ions by pervaporation.

    PubMed

    Uragami, Tadashi; Banno, Masashi; Miyata, Takashi

    2015-12-10

    To obtain high dehydration membranes for an ethanol/water azeotrope, dried blend membranes prepared from mixtures of sodium alginate (Alg-Na) and sodium deoxyribonucleate (DNA-Na) were cross-linked by immersing in a methanol solution of CaCl2 or MaCl2. In the dehydration of an ethanol/water azeotropic mixture by pervaporation, the effects of immersion time in methanol solution of CaCl2 or MaCl2 on the permeation rate and water/ethanol selectivity through Alg-DNA/Ca(2+) and Alg-DNA/Mg(2+) cross-linked membranes were investigated. Alg-DNA/Mg(2+) cross-linked membrane immersed for 12h in methanol solution of MaCl2 exhibited the highest water/ethanol selectivity. This results from depressed swelling of the membranes by formation of a cross-linked structure. However, excess immersion in solution containing cross-linker led to an increase in the hydrophobicity of cross-linked membrane. Therefore, the water/ethanol selectivity of Alg-DNA/Mg(2+) cross-linked membranes with an excess immersion in cross-linking solution was lowered. The relationship between the structure of Alg-DNA/Ca(2+) and Alg-DNA/Mg(2+) cross-linked membranes and their permeation and separation characteristics during pervaporation of an ethanol/water azeotropic mixture is discussed in detail.

  15. "One-step" preparation of thiol-ene clickable PEG-based thermoresponsive hyperbranched copolymer for in situ crosslinking hybrid hydrogel.

    PubMed

    Dong, Yixiao; Saeed, Aram Omer; Hassan, Waqar; Keigher, Catherine; Zheng, Yu; Tai, Hongyun; Pandit, Abhay; Wang, Wenxin

    2012-01-01

    A well-defined poly(ethylene glycol) based hyperbranched thermoresponsive copolymer with high content of acrylate vinyl groups was synthesized via a "one-pot and one-step" deactivation enhanced atom transfer radical polymerization approach, which provided an injectable and in situ crosslinkable system via Michael-type thiol-ene reaction with a thiol-modified hyaluronan biopolymer. The hyperbranched structure, molecular weight, and percentage of vinyl content of the copolymer were characterized by gel permeation chromatography and (1)H NMR. The lower critical solution temperature of this copolymer is close to body temperature, which can result in a rapid thermal gelation at 37 °C. The scanning electron microscopy analysis of crosslinked hydrogel showed the network formation with porous structure, and 3D cell culture study demonstrated the good cell viability after the cells were embedded inside the hydrogel. This injectable and in situ crosslinking hybrid hydrogel system offers great promise as a new class of hybrid biomaterials for tissue engineering.

  16. Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M; Velasquillo, C; García-Carvajal, Z Y; García-López, J; Ortega-Sánchez, C; Ibarra, C; Luna-Bárcenas, G; Solís-Arrieta, L

    2014-01-01

    The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications.

  17. In Situ Synthesis of Imidazolium-Crosslinked Ionogels via Debus-Radziszewski Reaction Based on PAMAM Dendrimers in Imidazolium Ionic liquid.

    PubMed

    Zhao, Xiaomeng; Guo, Shufei; Li, Hao; Liu, Jiahang; Liu, Xinxin; Song, Hongzan

    2017-09-12

    This study reports a remarkably facile method to synthesize novel ionogels with imidazolium cycle crosslinks based on polyamidoamine (PAMAM) dendrimers via one-pot, modified Debus-Radziszewski reaction in ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). High room temperature ionic conductivity (up to 6.8 mS cm(-1) ) is achieved, and more remarkably, it can still exceed 1 mS cm(-1) when the dendrimer content reached 70% because PAMAM dendrimers are completely amorphous with many cavities and the newly formed imidazolium crosslinks contains ions. The elastic modulus of these ionogels can exceed 10(6) Pa due to the newly-formed rigid imidazolium crosslinks. Crucially, these ionogels are robust gels even at temperatures up to 160 °C. Such novel ionogels with high ionic conductivity, tunable modulus, and flexibility are desirable for use in high-temperature flexible electrochemical devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Preparation and evaluation of BSA-based hydrosol nanoparticles cross-linked with genipin for oral administration of poorly water-soluble curcumin.

    PubMed

    Shahgholian, Narges; Rajabzadeh, Ghadir; Malaekeh-Nikouei, Bizhan

    2017-11-01

    One of the most interesting functions of albumin is the ability to interact with bioactive compounds. This study describes preparation of protein-based nanoparticles (NPs) for the preparation of solid dispersion of curcumin (CN). Fabrication of hydrosol system of dispersed CN in bovine serum albumin (BSA) was approached, followed by cross-linking with glutaraldehyde (Gta). Response surface methodology (RSM) was used to investigate the influence of input factors (pH, CN content and organic phase ratio (r)), on the particle size and CN entrapment efficiency (EE). Particle size, EE and CN loading efficiency (LE) at optimum condition (pH 7, r 10% and 3.4mg of CN content), were found to be in the range of 153-184.4nm, 72.54%, and 14.508μg/mg, respectively. In the optimum formulation, genipin (Gnp) was used at three different levels (0.1-0.2 and 0.3% w/w of BSA), as a safe, natural cross-linker instead of toxic Gta, to address the limitation of oral delivery purpose. AFM and SEM analysis revealed the spherical and smooth surface of Nps. Ninhydrin (NHD) assay and FT-IR analysis confirmed the cross-linking between BSA and Gnp. In vitro release studies ensure the efficiency of the formulation for sustained release of soluble CN. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. The development of non-toxic ionic-crosslinked chitosan-based microspheres as carriers for the controlled release of silk sericin.

    PubMed

    Aramwit, Pornanong; Ekasit, Sanong; Yamdech, Rungnapha

    2015-10-01

    Silk sericin is recently shown to possess various biological activities for biomedical applications. While various sericin carriers were developed for drug delivery system, very few researches considered sericin as a bioactive molecule itself. In this study, sericin incorporated in the chitosan-based microspheres was introduced as a bioactive molecule and bioactive carrier at the same time. The chitosan/sericin (CH/SS) microspheres at different composition (80/20, 70/30, 60/40, and 50/50) were successfully fabricated using anhydroustri-polyphosphate (TPP) as a polyanionic crosslinker. The microspheres with an average size of 1-4 μm and narrow size distribution were obtained. From FT-IR spectra, the presence of both chitosan and sericin in the microspheres confirmed the occurrence of ionic interaction that crosslink them within the microspheres. We also found that the CH/SS microspheres prepared at 50/50 could encapsulate sericin at the highest percentage (37.28%) and release sericin in the most sustained behavior, possibly due to the strong ionic interaction of the positively charged chitosan and the negatively charged sericin. On the other hand, the composition of CH/SS had no effect on the degradation rate of microspheres. All microspheres continuously degraded and remained around 20% after 14 days of enzymatic degradation. This explained that the ionic crosslinkings between chitosan and sericin could be demolished by the enzyme and hydrolysis. Furthermore, we have verified that all CH/SS microspheres at any concentrations showed non-toxicity to L929 mouse fibroblast cells. Therefore, we suggested that the non-toxic ionic-crosslinked CH/SS microspheres could be incorporated in wound dressing material to achieve the sustained release of sericin for accelerated wound healing.

  20. First-trimester fetal sex prediction by deoxyribonucleic acid analysis of maternal peripheral blood.

    PubMed

    Falcinelli, C; Battafarano, S; Neri, C; Mazza, V; Ranzi, A; Volpe, A; Forabosco, A

    1999-09-01

    We investigated whether the number of weeks of gestation influences the accuracy of first-trimester fetal sex prediction by analysis of deoxyribonucleic acid extracted from whole maternal blood. A comparison was also made to determine whether a difference exists between this approach and the deoxyribonucleic acid analysis of transcervical cells performed on the same group of subjects. Deoxyribonucleic acid was isolated from 50 maternal blood samples taken between gestational weeks 7 and 11. The sex of the fetus was assessed by nested polymerase chain reaction specific for the amelogenin gene. A receiver-operating characteristic curve analysis was used to correlate the accuracy of fetal gender prediction with the gestational age and also to compare the goodness of the 2 methods under investigation. Analysis of the receiver-operating characteristic curve provided a cutoff value of 9 weeks 4 days of gestation for both tests, indicating that a higher degree of accuracy in the sex assignment was obtained in those samples taken before or at this time. However, this difference was statistically significant only for analysis of deoxyribonucleic acid from maternal blood. The comparison between tests of deoxyribonucleic acid from maternal blood and from transcervical cells showed that the first approach is better, although a statistically significant difference was not found. Analysis of maternal blood deoxyribonucleic acid is a better approach than analysis of trans-cervical cell deoxyribonucleic acid in fetal sex prediction. The highest degree of accuracy is obtained when blood is drawn before 10 weeks of gestation. This can be important when sampling of chorionic villi should be avoided because of the risk of an X-linked disease when the fetal sex is female.

  1. DNA Gel with dynamic cross-links

    NASA Astrophysics Data System (ADS)

    Park, Chang-Young; Fygenson, Deborah; Saleh, Omar

    2014-03-01

    The mechanical properties of a living cell are strongly related to the cytoskeletal network, which is comprised of diverse protein filaments connected by cross-linking proteins, some of which are dynamic. Gels comprised of dynamic cross-linkers exhibit unique mechanical properties not seen in those using permanent cross-linkers. To investigate the effect of a dynamic cross-linker on mechanical properties of a material, we have synthesized biopolymer gels with a well-known semi-flexible biopolymer, DNA, and probed the mechanics of the system using microrheological techniques. We discuss these results in comparison to cytoskeletal systems, and seek to establish universal principles of dynamic cross-link based gels. This work was supported by the NSF-funded UCSB MRSEC program, Award No. DMR-0520415.

  2. pH-responsive deoxyribonucleic acid capture/release by polydopamine functionalized magnetic nanoparticles.

    PubMed

    Wang, Yu; Ma, Xiangdong; Ding, Chun; Jia, Li

    2015-03-03

    Polydopamine functionalized magnetic nanoparticles (PDA@Fe3O4) were prepared and characterized by transmission electron microscopy, scanning electron microscopy, zeta potential and vibrating sample magnetometry. They were found to enable highly efficient capture of genomic deoxyribonucleic acid (DNA). The adsorption capacity of PDA@Fe3O4 for genomic DNA can reach 161 mg g(-1). The extraction protocol used aqueous solutions for DNA binding to and releasing from the surface of the magnetic particles based on the pH inducing the charge switch of amino and phenolic hydroxyl groups on PDA@Fe3O4. The extracted DNA with high quality (A260/A280=1.80) can be directly used as templates for polymerase chain reaction (PCR) followed by capillary electrophoresis (CE) analysis. None of the toxic chemical reagents and PCR inhibitors was used throughout the whole procedure. PDA@Fe3O4 based magnetic solid phase extraction (MSPE) method was superior to those using commercial kit and traditional phenol-chloroform extraction methods in yield of DNA. The developed PDA@Fe3O4 based MSPE-PCR-CE method was applied for simultaneous and fast detection of Listeria monocytogenes and Escherichia coli O157:H7 in milk. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Motion of megabase deoxyribonucleic acid during field-inversion gel electrophoresis: Investigation by nonlocal Monte Carlo

    NASA Astrophysics Data System (ADS)

    Duke, T. A. J.; Viovy, J. L.

    1992-06-01

    We give a detailed description of a new Monte Carlo method for the simulation of the forced dynamics of long chain polymers in a constrictive environment. The model is based on the reptation theory but admits, in addition, the possibility that loops of the chain (``hernias'') may escape laterally out of the tube. A discrete representation of the molecule, in which individual chain segments are either taut or slack, permits the extensional mode of the molecule within the tube to be taken into consideration. The dynamics is modeled by the nonlocal hopping of ``defects'' (regions of slack) along the chain, with Monte Carlo rules based on the stochastic equations of motion of the taut portions of the molecule. We use the technique to investigate the motion of long deoxyribonucleic acid (DNA) molecules, containing millions of base pairs, during field-inversion gel electrophoresis. For the pulse ratios most commonly used in practice, we find that the separation patterns display two regions of band-inversion. This anomalous behavior is linked to the strong transient response of the molecules when the field is reversed; sudden field inversion induces the formation of a chain configuration shaped like an extended V after an interval of time that increases linearly with the chain length. The DNA molecules that have the minimum and the maximum migration speeds are those whose transient response times are approximately equal to the forward and the reverse pulse time, respectively.

  4. Development of a glucose oxidase-based biocatalyst adopting both physical entrapment and crosslinking, and its use in biofuel cells.

    PubMed

    Chung, Yongjin; Ahn, Yeonjoo; Christwardana, Marcelinus; Kim, Hansung; Kwon, Yongchai

    2016-04-28

    New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL(-1), they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/[GOx/PEI/CNT]) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/[GOx/PEI/CNT], including 4 mg mL(-1) GOx displays a high electron transfer rate, followed by excellent catalytic activity and EBC performance.

  5. Influence of cross-linkers on the cohesive and adhesive self-healing ability of polysulfide-based thermosets.

    PubMed

    Lafont, U; van Zeijl, H; van der Zwaag, S

    2012-11-01

    Synthetic systems with intrinsic self-repairing or self-healing abilities have emerged during the past decade. In this work, the influence of the cross-linker and chain rigidity on the healing ability of thermoset rubbers containing disulfide bonds have been investigated. The produced materials exhibit adhesive and cohesive self-healing properties. The recovery of these two functionalities upon the thermally triggered healing events has shown to be highly dependent on the network cross-link density and chain rigidity. As a result, depending on the rubber thermoset intrinsic physical properties, the thermal mending leading to full cohesive recovery can be achieved in 20-300 min at a modest healing temperature of 65 °C. The adhesive strength ranges from 0.2 to 0.5 MPa and is fully recovered even after multiple failure events.

  6. Thiouracil cross-linking mass spectrometry: a cell-based method to identify host factors involved in viral amplification.

    PubMed

    Lenarcic, Erik M; Landry, Dori M; Greco, Todd M; Cristea, Ileana M; Thompson, Sunnie R

    2013-08-01

    Eukaryotic RNA viruses are known to utilize host factors; however, the identity of these factors and their role in the virus life cycle remain largely undefined. Here, we report a method to identify proteins bound to the viral RNA during amplification in cell culture: thiouracil cross-linking mass spectrometry (TUX-MS). TUX-MS relies on incorporation of a zero-distance cross-linker into the viral RNA during infection. Proteins bound to viral RNA are cross-linked prior to cell lysis, purified, and identified using mass spectrometry. Using the TUX-MS method, an unbiased screen for poliovirus (PV) host factors was conducted. All host and viral proteins that are known to interact with the poliovirus RNA were identified. In addition, TUX-MS identified an additional 66 host proteins that have not been previously described in poliovirus amplification. From these candidates, eight were selected and validated. Furthermore, we demonstrate that small interfering RNA (siRNA)-mediated knockdown of two of these uncharacterized host factors results in either a decrease in copy number of positive-stranded RNA or a decrease in PV translation. These data demonstrate that TUX-MS is a robust, unbiased method to identify previously unknown host cell factors that influence virus growth. This method is broadly applicable to a range of RNA viruses, such as flaviviruses, alphaviruses, picornaviruses, bunyaviruses, and coronaviruses.

  7. Thiouracil Cross-Linking Mass Spectrometry: a Cell-Based Method To Identify Host Factors Involved in Viral Amplification

    PubMed Central

    Lenarcic, Erik M.; Landry, Dori M.; Greco, Todd M.; Cristea, Ileana M.

    2013-01-01

    Eukaryotic RNA viruses are known to utilize host factors; however, the identity of these factors and their role in the virus life cycle remain largely undefined. Here, we report a method to identify proteins bound to the viral RNA during amplification in cell culture: thiouracil cross-linking mass spectrometry (TUX-MS). TUX-MS relies on incorporation of a zero-distance cross-linker into the viral RNA during infection. Proteins bound to viral RNA are cross-linked prior to cell lysis, purified, and identified using mass spectrometry. Using the TUX-MS method, an unbiased screen for poliovirus (PV) host factors was conducted. All host and viral proteins that are known to interact with the poliovirus RNA were identified. In addition, TUX-MS identified an additional 66 host proteins that have not been previously described in poliovirus amplification. From these candidates, eight were selected and validated. Furthermore, we demonstrate that small interfering RNA (siRNA)-mediated knockdown of two of these uncharacterized host factors results in either a decrease in copy number of positive-stranded RNA or a decrease in PV translation. These data demonstrate that TUX-MS is a robust, unbiased method to identify previously unknown host cell factors that influence virus growth. This method is broadly applicable to a range of RNA viruses, such as flaviviruses, alphaviruses, picornaviruses, bunyaviruses, and coronaviruses. PMID:23740976

  8. Exceptionally stable polymer electrolyte for a lithium battery based on cross-linking by a residue-free process

    NASA Astrophysics Data System (ADS)

    Daigle, Jean-Christophe; Asakawa, Yuichiro; Vijh, Ashok; Hovington, Pierre; Armand, Michel; Zaghib, Karim

    2016-11-01

    In this paper, we report the synthesis of cross-linked copolymers of glycidyl methacrylate (GMA) and poly (ethylene glycol) methyl methacrylate (PEGMA) for use as solid polymer electrolytes (SPE). The cross-linking is performed with volatile ethylene diamine, thus preventing the accumulation of undesirable precursors in the final membrane. The structure of the cross-linked polymer electrolyte was investigated by 13C solid NMR and its physical properties were examined by DSC, TGA and stress-strain tests. The ionic conductivities were determined by AC Impedance, which showed that the SPEs have good conductivities (10-5 Scm-1) at 80 °C. The highest capacity measured with these polymers was 151 mAh g-1 at C/6 and 80 °C for a LFP/SPE/Lithium battery. The retention capacity is high, at 97% after 80 cycles at different rates of cycling. The Young's modulus of the membranes is as high as 1 GPa. The SEM images showed no evidence of lithium dendrites and no degradation after cycling. Therefore, the polymer is a good candidate for battery operation over a long time. Especially important is the ability of this polymer to prevent growth of dendrites on the Li-metal electrode.

  9. PEG-detachable and acid-labile cross-linked micelles based on orthoester linked graft copolymer for paclitaxel release

    NASA Astrophysics Data System (ADS)

    Yuan, Zhefan; Huang, Jingyi; Liu, Jing; Cheng, Sixue; Zhuo, Renxi; Li, Feng

    2011-08-01

    Polyethylene glycol detachable graft copolymer, mPEG-g-p(NAS-co-BMA), was synthesized by grafting 2-(ω-methoxy)PEGyl-1,3-dioxan-5-ylamine onto poly(N-(acryloyloxy)succinimide-co-butyl methacrylate). Pseudo in situ cross-linking of the mPEG-g-p(NAS-co-BMA) was performed in dimethylformamide phosphate buffer (v/v = 1/1) by an acid-labile diamine cross-linker bearing two symmetrical cyclic orthoesters. The cross-linked (CL) micelles with different contents of mPEG segments represented different morphologies. The CL micelles containing approximately one mPEG segment exhibited 'echini' morphology whereas the CL micelle with approximately three mPEG segments formed nanowires. The hydrolysis rate of the CL micelles is highly pH-dependent and much more rapid at mild acid than physiological conditions. Hydrolyzates of the CL micelles formed vesicles because new amphiphilic copolymers were formed. Paclitaxel (PTX) was successfully loaded into the CL micelles and a controlled and pH-dependent release behavior was observed. No obvious cytotoxicity was found for the CL micelles at concentration as high as 800 mg l - 1.

  10. Synthesis and characterization of glutaraldehyde-based crosslinked gelatin as a local hemostat sponge in surgery: an in vitro study.

    PubMed

    Imani, Rana; Rafienia, Mohammad; Emami, Shahriar Hojjati

    2013-01-01

    In this study, preparation and characterization of soft crosslinked gelatin sponge for blood hemostasis application was considered. The effects of gelatin and crosslinker concentrations and altering freeze-drying temperature on sponges' density and structure, water absorption ability and biodegradation, cytotoxicity, mechanical properties and hemostatic effect were investigated. The density measurement indicated that the density of freeze-dried sponges increased when the freezing temperature was lowered. Scanning electron microscope and optical microscope images showed that gelatin sponges had uniform small pores (60 μm) after freezing at liquid nitrogen (-196°C). Biodegradation study demonstrated that the crosslinked sponges containing 1% and 2% gelatin lost respectively nearly 40 to 70% of their weight during 24 h. Prepared sponges showed desired water absorption ability (30-40 times of own dry weight) improved by lowering glutaraldehyde concentration. Cell toxicity was not detected in any of the samples. Compression modulus of sponges decreased four times (160 to 40 kPa) as the gelatin content varied from 2 to 1% w/v. Hemostasis study confirmed that the hemolytic ability of sponges increased through raising gelatin content and porosity of sponge. We suggest using gelatin sponges containing 1% w/v gelatin, 0.5% w/v glutaraldehyde frozen in liquid nitrogen, as a potential substitution for local hemostat absorbable sponge.

  11. Mass Spectrometry Based Proteomics Study of Cisplatin-Induced DNA-Protein Cross-Linking in Human Fibrosarcoma (HT1080) Cells.

    PubMed

    Ming, Xun; Groehler, Arnold; Michaelson-Richie, Erin D; Villalta, Peter W; Campbell, Colin; Tretyakova, Natalia Y

    2017-04-17

    Platinum-based antitumor drugs such as 1,1,2,2-cis-diamminedichloroplatinum(II) (cisplatin), carboplatin, and oxaliplatin are currently used to treat nearly 50% of all cancer cases, and novel platinum based agents are under development. The antitumor effects of cisplatin and other platinum compounds are attributed to their ability to induce interstrand DNA-DNA cross-links, which are thought to inhibit tumor cell growth by blocking DNA replication and/or preventing transcription. However, platinum agents also induce significant numbers of unusually bulky and helix-distorting DNA-protein cross-links (DPCs), which are poorly characterized because of their unusual complexity. We and others have previously shown that DPCs block DNA replication and transcription and causes toxicity in human cells, potentially contributing to the biological effects of platinum agents. In the present work, we have undertaken a system-wide investigation of cisplatin-mediated DNA-protein cross-linking in human fibrosarcoma (HT1080) cells using mass spectrometry-based proteomics. DPCs were isolated from cisplatin-treated cells using a modified phenol/chloroform DNA extraction in the presence of protease inhibitors. Proteins were released from DNA strands and identified by mass spectrometry-based proteomics and immunological detection. Over 250 nuclear proteins captured on chromosomal DNA following treatment with cisplatin were identified, including high mobility group (HMG) proteins, histone proteins, and elongation factors. To reveal the exact molecular structures of cisplatin-mediated DPCs, isotope dilution HPLC-ESI(+)-MS/MS was employed to detect 1,1-cis-diammine-2-(5-amino-5-carboxypentyl)amino-2-(2'-deoxyguanosine-7-yl)-platinum(II) (dG-Pt-Lys) conjugates between the N7 guanine of DNA and the ε-amino group of lysine. Our results demonstrate that therapeutic levels of cisplatin induce a wide range of DPC lesions, which likely contribute to both target and off target effects of this

  12. Protein cross-linking in food.

    PubMed

    Gerrard, J A; Meade, S J; Miller, A G; Brown, P K; Yasir, S B M; Sutton, K H; Newberry, M P

    2005-06-01

    The aims of this paper are (1) to probe the relationship between molecular structure and protein cross-linking ability for a range of small molecules; (2) to establish whether this relationship holds within a food matrix; and (3) to test the impact of Maillard cross-linking on food functionality, particularly texture, in wheat- and soy-based food systems. A variety of molecules were obtained, either commercially or via organic synthesis. Cross-linking ability was tested using our standard model system, employing ribonuclease A and analyzing the results by SDS-PAGE. Molecules of varying reactivity were tested in wheat- and soy-based products, and the changes in functionality were correlated with changes in protein cross-linking. No simple relationship was found between molecular structure and ability to cross-link ribonuclease. Only the most reactive reagents were able to cross-link within the food matrix. Nevertheless, a low degree of cross-linking was shown to have significant consequences on the properties of wheat- and soy-based foods, suggesting that the Maillard reaction may represent a means to control food texture.

  13. Characterisation of the DNA sequence specificity, cellular toxicity and cross-linking properties of novel bispyridine-based dinuclear platinum complexes.

    PubMed

    Johnson, Ben W; Murray, Vincent; Temple, Mark D

    2016-05-25

    The anti-tumour activity of cisplatin is thought to be a result of its capacity to form DNA adducts which prevent cellular processes such as DNA replication and transcription. These DNA adducts can effectively induce cancer cell death, however, there are a range of clinical side effects and drug resistance issues associated with its use. In this study, the biological properties of three novel dinuclear platinum-based compounds (that contain alkane bridging linkers of eight, ten and twelve carbon atoms in length) were characterised to assess their potential as anticancer agents. The properties of these compounds were determined using a DNA template containing seven tandem telomeric repeat sequences. A linear amplification reaction was used in combination with capillary electrophoresis to quantify the sequence specificity of DNA adducts formed by these compounds at base pair resolution. The DNA cross-linking ability of these compounds was assessed using denaturing agarose gel electrophoresis and cytotoxicity was determined in HeLa cells using a colorimetric cell viability assay. The dinuclear compounds were found to preferentially form DNA adducts at guanine bases and they exhibited different damage intensity profiles at the telomeric repeat sequences compared to that of cisplatin. The dinuclear compounds were found to exhibit a low level of cytotoxicity relative to cisplatin and their cytotoxicity increased as the linker length increased. Conversely, the interstrand cross-linking efficiency of the dinuclear compounds increased as the linker length decreased and the compound with the shortest alkane linker was six-fold more effective than cisplatin. Since the bifunctional compounds exhibit variation in sequence specificity of adduct formation and a greater ability to cross-link DNA relative to cisplatin they warrant further investigation towards the goal of developing new cancer chemotherapeutic agents.

  14. Study on the interaction of morphine chloride with deoxyribonucleic acid by fluorescence method

    NASA Astrophysics Data System (ADS)

    Li, J. F.; Dong, C.

    2009-01-01

    The mode and mechanism of the interaction of morphine chloride, an important alkaloid compound to calf thymus deoxyribonucleic acid (ct DNA) was investigated from absorption and fluorescence titration techniques. Hypochromic effect was founded in the absorption spectra of morphine when concentration of DNA increased. The decreased fluorescence study revealed non-cooperative binding of the morphine to DNA with an affinity of 3.94 × 10 3 M -1, and the stoichiometry of binding was characterized to be about one morphine molecule per nucleotide. Stern-Volmer plots at different temperatures proved that the quenching mechanism was static. Ferrocyanide quenching study showed that the magnitude of KSV of the bound morphine was lower than that of the free one. In addition, it was found that ionic strength could affect the binding of morphine and DNA. Fluorescence polarization and denatured DNA studies also applied strong evidences that morphine molecule was partially intercalated between every alternate base pairs of ct DNA. As observed from above experiments, intercalation was well supported as the binding mode of morphine and ct DNA.

  15. Integrity of nuclear genomic deoxyribonucleic acid in cooked meat: Implications for food traceability.

    PubMed

    Aslan, O; Hamill, R M; Sweeney, T; Reardon, W; Mullen, A M

    2009-01-01

    It is essential to isolate high-quality DNA from muscle tissue for PCR-based applications in traceability of animal origin. We wished to examine the impact of cooking meat to a range of core temperatures on the quality and quantity of subsequently isolated genomic (specifically, nuclear) DNA. Triplicate steak samples were cooked in a water bath (100 degrees C) until their final internal temperature was 75, 80, 85, 90, 95, or 100 degrees C, and DNA was extracted. Deoxyribonucleic acid quantity was significantly reduced in cooked meat samples compared with raw (6.5 vs. 56.6 ng/microL; P < 0.001), but there was no relationship with cooking temperature. Quality (A(260)/A(280), i.e., absorbance at 260 and 280 nm) was also affected by cooking (P < 0.001). For all 3 genes, large PCR amplicons (product size >800 bp) were observed only when using DNA from raw meat and steak cooked to lower core temperatures. Small amplicons (<200 bp) were present for all core temperatures. Cooking meat to high temperatures thus resulted in a reduced overall yield and probable fragmentation of DNA to sizes less than 800 bp. Although nuclear DNA is preferable to mitochondrial DNA for food authentication, it is less abundant, and results suggest that analyses should be designed to use small amplicon sizes for meat cooked to high core temperatures.

  16. Coordination of deoxyribonucleic acid by ions of alkaline-earth elements

    SciTech Connect

    Tikhonova, L.I.

    1986-05-01

    The interaction of deoxyribonucleic acid (DNA) isolated from salmonid fish milt with Ca/sup 2 +/ and Sr/sup 2 +/ has been studied by conductometric, ion-exchange, and spectroscopic (circular dichroism, CD) methods at ambient ionic strengths equal to 0.0025, 0.0036, 0.0005, 0.01, and 0.165 (NaCl) and pH 6.5-6.6 and and.4 (buffer). The molecular weights of the biopolymer were 9.1 x 10/sup 6/ and 15.35 x 10/sup 6/ (ion exchange was carried out with the native and denatured forms with the use of /sup 45/Ca and /sup 85/Sr). The discontinuities on the conductometric titration curves correspond to M/sup 2 +/:DNA ratios equal to 0.125, 0.3, and 0.5. The calculated values of the associated constants are close for the two samples in the native and denatured forms over a broad range of concentrations of the cations. An anticooperature process has been established in the interaction of the cations with phosphate groups in both forms of the biopolymer. It has been concluded that the phosphate groups and purine bases of the DNA participate in coordination when the ionic strength is low or when the excess of the cations is great (..mu.. = 0.165). This attests to the influence of the concentration of the sodium ion on the interaction processes of DNA.

  17. Particle acceleration for delivery deoxyribonucleic acid vaccine into skin in vivo

    NASA Astrophysics Data System (ADS)

    Xinglong, Yu; Xiwen, Zhang; Yuan, Wang; Junshi, Xie; Pengfei, Hao

    2001-08-01

    Skin represents an important immunogenic inductive site, 3%-4% epidermis cells are special antigen-presenting cells. Deoxyribonucleic acid (DNA) vaccine can elicit vigorous immune responses in epidermis cells. The means of delivering DNA vaccine into epidermis cells becomes an important step in DNA vaccine applications. This article presents a new type of gene gun based on the principle of two-stage injector acceleration. DNA coated particles are attached on an screen-type carrier located at the negative pressure inlet, the particles will be sucked into the accelerating channel by negative pressure and be accelerated at a great speed. FLUENT, a computation fluid dynamic application software is used to simulate the flow condition of the injector. Distribution of Mach number, total pressure on exit cross section, and negative pressure on negative pressure inlet are analyzed, by which the process of acceleration of particles is determined. We also measured these parameters in this study. The data show that the particle velocity can be up to 500 m/s and the particles distribute evenly over a circle of Φ 20 mm. The numerical simulation results coincide with experimental data well. Therefore, the results of numerical simulation can be served as guidance for an optimal design of the gene gun and for practical operations. When gene coated particles are distributed evenly, they can penetrate into or even through epidermis cells where the gene can be expressed and subsequently elicits host immune responses. This device may be evaluated in human objects in future.

  18. Crosslinkable low bandgap polymers for organic solar cells

    NASA Astrophysics Data System (ADS)

    Strohriegl, Peter; Saller, Christina; Knauer, Philipp; Köhler, Anna; Hahn, Tobias; Fischer, Florian; Kahle, Frank-Julian

    2016-09-01

    We present a number of polyfluorene based conjugated polymers with crosslinkable acrylate and oxetane units. These polymers can be crosslinked by free radical polymerization in the case of acrylates and by cationic ring opening polymerization for oxetanes. Upon polymerization densely crosslinked networks are formed which are completely insoluble. We show that the diffusion coefficient of C60 in polyfluorene is reduced by a factor of 1000 by crosslinking. MIS-CELIV measurements are used to monitor changes in the charge carrier mobility upon crosslinking. It shows that using appropriate conditions, e.g. low initiator concentrations or thermal crosslinking, the charge carrier mobility is not reduced by crosslinking. Solution processed three layer organic solar cells were realized with a crosslinkable fluorene based copolymer containing acrylate groups. The efficiency is increased from 1.4% for the reference to 1.8% in the three layer cell with a crosslinked exciton blocking layer. A critical issue of BHJ cells is the instability of the morphology of the polymer:fullerene blend over long operation times at elevated temperature. We present a crosslinkable derivative of the low bandgap polymer PFDTBT which contains oxetane units. BHJ cells with the crosslinked PFDTBT derivative and PCBM were tested in accelerated aging experiments at 100 °C for times up to 100 h. Stabilization was clearly observed in crosslinked BHJ cells compared to the non-crosslinked reference. We show for the first time that oxetane containing polymers can be thermally crosslinked without any added initiator. Initiator free crosslinking is particularly attractive as it avoids the formation of decomposition products, and thus potential electron traps and quenching sites from the initiator.

  19. Desmosine-Inspired Cross-Linkers for Hyaluronan Hydrogels

    NASA Astrophysics Data System (ADS)

    Hagel, Valentin; Mateescu, Markus; Southan, Alexander; Wegner, Seraphine V.; Nuss, Isabell; Haraszti, Tamás; Kleinhans, Claudia; Schuh, Christian; Spatz, Joachim P.; Kluger, Petra J.; Bach, Monika; Tussetschläger, Stefan; Tovar, Günter E. M.; Laschat, Sabine; Boehm, Heike

    2013-06-01

    We designed bioinspired cross-linkers based on desmosine, the cross-linker in natural elastin, to prepare hydrogels with thiolated hyaluronic acid. These short, rigid cross-linkers are based on pyridinium salts (as in desmosine) and can connect two polymer backbones. Generally, the obtained semi-synthetic hydrogels are form-stable, can withstand repeated stress, have a large linear-elastic range, and show strain stiffening behavior typical for biopolymer networks. In addition, it is possible to introduce a positive charge to the core of the cross-linker without affecting the gelation efficiency, or consequently the network connectivity. However, the mechanical properties strongly depend on the charge of the cross-linker. The properties of the presented hydrogels can thus be tuned in a range important for engineering of soft tissues by controlling the cross-linking density and the charge of the cross-linker.

  20. Preparation of a calcium carbonate-based bone substitute with cinnamaldehyde crosslinking agent with potential anti-inflammatory properties.

    PubMed

    Dewi, Anne Handrini; Ana, Ika Dewi; Jansen, John

    2017-04-01

    Calcium sulfate (CS), also known as POP (Plaster of Paris) is a self-setting, biocompatible, and osteoconductive biomaterial with a long history for the treatment of skeletal defects. However, CS cements show a too fast resorption rate and are unable to provide a long-term 3D framework during the osteogenesis process. In our previous studies, it was found that the incorporation of CaCO3 and CaCO3 hydrogel provided enhanced mechanical and degradation properties of POP composites. Furthermore, it was also found that the use of cinnamaldehyde to crosslink CaCO3 hydrogel may have some advantages, for example to crosslink the hydrogel and to act as anti-inflammatory control agent. The objective of the current study was to evaluate the effect of adding cinnamaldehyde crosslinked CaCO3 hydrogel into POP on the diametral tensile strength, weight loss, age swelling, degradation, cinnamaldehyde release, and porosity. The following composites were prepared: POP/HCin-025 (25% addition of hydrogel microsphere) and POP/HCin-050 (50% addition of hydrogel microsphere). The composites were assessed on their diametral tensile strength, weight loss of the POP composite, age swelling, degradation of the hydrogel CaCO3 , cinnamaldehyde release, and porosity, as well as XRD-patterns and FT-IR spectra. It was confirmed from the study that incorporation of cinnamaldehyde into CaCO3 hydrogel system significantly increased the mechanical strength of the POP composite. Weight loss, swelling ratio in both acid to neutral pH, and biodegradability of the POP composites were controllable by the addition of cinnamaldehyde-CaCO3 hydrogel. Moreover, the cinnamaldehyde incorporated into the hydrogel was proven to be released in a controlled manner. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1055-1062, 2017.

  1. Development of a glucose oxidase-based biocatalyst adopting both physical entrapment and crosslinking, and its use in biofuel cells

    NASA Astrophysics Data System (ADS)

    Chung, Yongjin; Ahn, Yeonjoo; Christwardana, Marcelinus; Kim, Hansung; Kwon, Yongchai

    2016-04-01

    New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL-1, they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/[GOx/PEI/CNT]) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/[GOx/PEI/CNT], including 4 mg mL-1 GOx displays a high electron transfer rate, followed by excellent catalytic activity and EBC performance.New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL-1, they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/[GOx/PEI/CNT]) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/[GOx/PEI/CNT], including 4 mg mL-1 GOx displays a high

  2. Study of cross-linking process in grafted polyethylene and ethylene based copolymer using a phase resolved photoacoustic method

    NASA Astrophysics Data System (ADS)

    Dias, D. T.; Medina, A. N.; Baesso, M. L.; Bento, A. C.; Porto, M. F.; Muniz, E. C.; Rubira, A. F.

    2003-01-01

    In this work, the phase resolved photoacoustic method has been employed to monitor water saturated vapor cross linking in both copolymer and grafted polyethylene. The overtone bands and stretching frequencies combinations of the -Si-OH, =CH2, -CH3, and -CH2-CH3 were monitored and analyzed accordingly to a 32 factorial design with nine samples. The results showed that the cross-linking processes were more efficient when the samples were prepared at 80 °C with the catalyst in the concentration range between 3% and 5% for grafted PE, while 70 °C was the best temperature to obtain copolymer.

  3. Selective formation of organo, organo-aqueous, and hydro gel-like materials from partially hydrolysed poly(vinyl acetate)s based on different boron-containing crosslinkers.

    PubMed

    Angelova, L V; Leskes, M; Berrie, B H; Weiss, R G

    2015-07-07

    Viscoelastic, gel-like, polymeric dispersions (HVPDs) can be prepared by crosslinking polyols with borax or boric acid in water under alkaline conditions. Rheologically similar HVPDs have been prepared in organic liquids containing no water or hydroxylic groups through crosslinking partially or fully hydrolysed poly(vinyl acetate)s with trimethyl borate, boric acid, or borax. The organo-HVPDs are water-sensitive and rheoreversible on exposure to water. They were characterised rheologically and by solution and solid-state (11)B NMR spectroscopy. Spectroscopic analyses show the presence of mono- and di-diol crosslinks, as well as non-crosslinked boron species in HVPDs prepared with trimethyl borate or boric acid. The number of crosslinks in organo-HVPDs prepared with borax increased over the course of several days. Results from solution and solid-state (11)B NMR spectroscopy are comparable; no solid-like component was detectable. We demonstrate that hydro, organo, or organo-aqueous HVPDs can be obtained from partially hydrolysed poly(vinyl acetate)s by 'tuning' the structure of the boron-based crosslinker.

  4. Synthesis, Characterisation, and Evaluation of a Cross-Linked Disulphide Amide-Anhydride-Containing Polymer Based on Cysteine for Colonic Drug Delivery

    PubMed Central

    Lim, Vuanghao; Peh, Kok Khiang; Sahudin, Shariza

    2013-01-01

    The use of disulphide polymers, a low redox potential responsive delivery, is one strategy for targeting drugs to the colon so that they are specifically released there. The objective of this study was to synthesise a new cross-linked disulphide-containing polymer based on the amino acid cysteine as a colon drug delivery system and to evaluate the efficiency of the polymers for colon targeted drug delivery under the condition of a low redox potential. The disulphide cross-linked polymers were synthesised via air oxidation of 1,2-ethanedithiol and 3-mercapto-N-2-(3-mercaptopropionamide)-3-mercapto propionic anhydride (trithiol monomers) using different ratio combinations. Four types of polymers were synthesised: P10, P11, P151, and P15. All compounds synthesised were characterised by NMR, IR, LC-MS, CHNS analysis, Raman spectrometry, SEM-EDX, and elemental mapping. The synthesised polymers were evaluated in chemical reduction studies that were performed in zinc/acetic acid solution. The suitability of each polymer for use in colon-targeted drug delivery was investigated in vitro using simulated conditions. Chemical reduction studies showed that all polymers were reduced after 0.5–1.0 h, but different polymers had different thiol concentrations. The bacterial degradation studies showed that the polymers were biodegraded in the anaerobic colonic bacterial medium. Degradation was most pronounced for polymer P15. This result complements the general consensus that biodegradability depends on the swellability of polymers in an aqueous environment. Overall, these results suggest that the cross-linked disulphide-containing polymers described herein could be used as coatings for drugs delivered to the colon. PMID:24351841

  5. Synthesis, characterisation, and evaluation of a cross-linked disulphide amide-anhydride-containing polymer based on cysteine for colonic drug delivery.

    PubMed

    Lim, Vuanghao; Peh, Kok Khiang; Sahudin, Shariza

    2013-12-18

    The use of disulphide polymers, a low redox potential responsive delivery, is one strategy for targeting drugs to the colon so that they are specifically released there. The objective of this study was to synthesise a new cross-linked disulphide-containing polymer based on the amino acid cysteine as a colon drug delivery system and to evaluate the efficiency of the polymers for colon targeted drug delivery under the condition of a low redox potential. The disulphide cross-linked polymers were synthesised via air oxidation of 1,2-ethanedithiol and 3-mercapto-N-2-(3-mercaptopropionamide)-3-mercapto propionic anhydride (trithiol monomers) using different ratio combinations. Four types of polymers were synthesised: P10, P11, P151, and P15. All compounds synthesised were characterised by NMR, IR, LC-MS, CHNS analysis, Raman spectrometry, SEM-EDX, and elemental mapping. The synthesised polymers were evaluated in chemical reduction studies that were performed in zinc/acetic acid solution. The suitability of each polymer for use in colon-targeted drug delivery was investigated in vitro using simulated conditions. Chemical reduction studies showed that all polymers were reduced after 0.5-1.0 h, but different polymers had different thiol concentrations. The bacterial degradation studies showed that the polymers were biodegraded in the anaerobic colonic bacterial medium. Degradation was most pronounced for polymer P15. This result complements the general consensus that biodegradability depends on the swellability of polymers in an aqueous environment. Overall, these results suggest that the cross-linked disulphide-containing polymers described herein could be used as coatings for drugs delivered to the colon.

  6. Solvent- and phase-controlled photochirogenesis. Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by cyclic nigerosylnigerose-based nanosponges crosslinked by pyromellitate.

    PubMed

    Wei, Xueqin; Liang, Wenting; Wu, Wanhua; Yang, Cheng; Trotta, Francesco; Caldera, Fabrizio; Mele, Andrea; Nishimoto, Tomoyuki; Inoue, Yoshihisa

    2015-03-14

    Cyclic nigerosylnigerose (CNN), a saucer-shaped cyclic tetrasaccharide with a shallow concave surface, was reacted with pyromellitic dianhydride in 1:2 and 1:4 ratios to give two CNN-based polymers of different degrees of crosslinking, both of which swelled upon soaking in water, acting as a ‘nanosponge’ (NS). These NSs evolved several phases from isotropic solution to flowing and rigid gels via suspension by gradually increasing the concentration in water. The CNN-NSs thus prepared effectively mediated the enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to chiral (E)-isomer (1E). The enantiomeric excess (ee) of 1E obtained was a critical function of the solvent composition and the phase evolved at different CNN-NS concentrations in water. In isotropic solution, the enantioselectivity was generally low (−4% to +6% ee) but the chiral sense of 1E was inverted by increasing the methanol content. Interestingly, the product's ee was controlled more dramatically by the phase evolved, as was the case with the cyclodextrin-based nanosponge (CD-NS) reported previously. Thus, the ee of 1E was low in solution and suspension, but suddenly leaped at the phase border of flowing gel and rigid gel to give the highest ee of 22–24%, which are much higher than those obtained with CD-NSs (6–12% ee), revealing the positive roles of the chiral void space formed upon gelation of the crosslinked saccharide polymer.

  7. Oxidatively Generated Guanine(C8)-Thymine(N3) Intrastrand Cross-links in Double-stranded DNA Are Repaired by Base Excision Repair Pathways.

    PubMed

    Talhaoui, Ibtissam; Shafirovich, Vladimir; Liu, Zhi; Saint-Pierre, Christine; Akishev, Zhiger; Matkarimov, Bakhyt T; Gasparutto, Didier; Geacintov, Nicholas E; Saparbaev, Murat

    2015-06-05

    Oxidatively generated guanine radical cations in DNA can undergo various nucleophilic reactions including the formation of C8-guanine cross-links with adjacent or nearby N3-thymines in DNA in the presence of O2. The G*[C8-N3]T* lesions have been identified in the DNA of human cells exposed to oxidative stress, and are most likely genotoxic if not removed by cellular defense mechanisms. It has been shown that the G*[C8-N3]T* lesions are substrates of nucleotide excision repair in human cell extracts. Cleavage at the sites of the lesions was also observed but not further investigated (Ding et al. (2012) Nucleic Acids Res. 40, 2506-2517). Using a panel of eukaryotic and prokaryotic bifunctional DNA glycosylases/lyases (NEIL1, Nei, Fpg, Nth, and NTH1) and apurinic/apyrimidinic (AP) endonucleases (Apn1, APE1, and Nfo), the analysis of cleavage fragments by PAGE and MALDI-TOF/MS show that the G*[C8-N3]T* lesions in 17-mer duplexes are incised on either side of G*, that none of the recovered cleavage fragments contain G*, and that T* is converted to a normal T in the 3'-fragment cleavage products. The abilities of the DNA glycosylases to incise the DNA strand adjacent to G*, while this base is initially cross-linked with T*, is a surprising observation and an indication of the versatility of these base excision repair proteins.

  8. Synthesis, Characterization, and Cross-Linking Strategy of a Quercetin-Based Epoxidized Monomer as a Naturally-Derived Replacement for BPA in Epoxy Resins.

    PubMed

    Kristufek, Samantha L; Yang, Guozhen; Link, Lauren A; Rohde, Brian J; Robertson, Megan L; Wooley, Karen L

    2016-08-23

    The natural polyphenolic compound quercetin was functionalized and cross-linked to afford a robust epoxy network. Quercetin was selectively methylated and functionalized with glycidyl ether moieties using a microwave-assisted reaction on a gram scale to afford the desired monomer (Q). This quercetin-derived monomer was treated with nadic methyl anhydride (NMA) to obtain a cross-linked network (Q-NMA). The thermal and mechanical properties of this naturally derived network were compared to those of a conventional diglycidyl ether bisphenol A-derived counterpart (DGEBA-NMA). Q-NMA had similar thermal properties [i.e., glass transition (Tg ) and decomposition (Td ) temperatures] and comparable mechanical properties (i.e., Young's Modulus, storage modulus) to that of DGEBA-NMA. However, it had a lower tensile strength and higher flexural modulus at elevated temperatures. The application of naturally derived, sustainable compounds for the replacement of commercially available petrochemical-based epoxies is of great interest to reduce the environmental impact of these materials. Q-NMA is an attractive candidate for the replacement of bisphenol A-based epoxies in various specialty engineering applications.

  9. Bio-Based Artificial Nacre with Excellent Mechanical and Barrier Properties Realized by a Facile In Situ Reduction and Cross-Linking Reaction.

    PubMed

    Shahzadi, Kiran; Mohsin, Imran; Wu, Lin; Ge, Xuesong; Jiang, Yijun; Li, Hui; Mu, Xindong

    2017-01-24

    Demands for high strength integrated materials have substantially increased across various kinds of industries. Inspired by the relationship of excellent integration of mechanical properties and hierarchical nano/microscale structure of the natural nacre, a simple and facile method to fabricate high strength integrated artificial nacre based on sodium carboxymethylcellulose (CMC) and borate cross-linked graphene oxide (GO) sheets has been developed. The tensile strength and toughness of cellulose-based hybrid material reached 480.5 ± 13.1 MPa and 11.8 ± 0.4 MJm(-3) by a facile in situ reduction and cross-linking reaction between CMC and GO (0.7%), which are 3.55 and 6.55 times that of natural nacre. This hybrid film exhibits better thermal stability and flame retardancy. More interestingly, the hybrid material showed good water stability compared to that in the original water-soluble CMC. This type of hybrid has great potential applications in aerospace, artificial muscle, and tissue engineering.

  10. Thermosensitivity of N-isopropylacrylamide hydrogels cross-linked with degradable cross-linker.

    PubMed

    Pérez, Paloma; Gallardo, Alberto; Corrigan, Owen I; Román, Julio San

    2008-01-01

    Thermosensitive N-isopropylacrylamide (NIPA)-based hydrogels have been prepared using a biodegradable pseudo-peptide (DMTLT, a tri-molecular adduct of tyrosine, lysine, tyrosine) as cross-linker. This new cross-linker provides a similar cross-linking efficiency as N,N' methylenbisacrylamide (BIS) (a standard biostable cross-linker) used as reference. The amount of DMTLT has shown to modulate, in addition to the cross-linking density, the transition temperature (the higher the amount of DMTLT, the lower the transition temperature), as well as the morphology and the whole aqueous behaviour. The incorporation of hydrophilic N,N'-dimethylacrylamide (DMA) increases the transition temperature, as expected. Finally, the matrices have exhibited in aqueous media a well-defined pulsatile behaviour in swelling and release of benzoic acid and dextran as models of ionisable molecules and non-ionisable macromolecules.

  11. Influence of surfactant on dynamics of photoinduced motions and light emission of a dye-doped deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Sznitko, Lech; Parafiniuk, Kacper; Miniewicz, Andrzej; Rau, Ileana; Kajzar, Francois; Niziol, Jacek; Hebda, Edyta; Pielichowski, Jan; Sahraoui, Bouchta; Mysliwiec, Jaroslaw

    2013-10-01

    Pure deoxyribonucleic acid (DNA) is known to be soluble in water only and exhibits poor temperature stability. In contrary, it is well known that the complex of DNA - with cetyltrimethyl ammonium (CTMA) is insoluble in water but soluble in alcohols and can be processed into very good optical quality thin films by solution casting or spin deposition. Despite the success of DNA-CTMA, there is still need for new cationic surfactants which would extend the range of available solvents for DNA complex. We test and present experimental results of influence of new surfactants replacing CTMA in the DNA complex and based on benzalkonium chloride (BA) and didecyldimethylammonium chloride (DDCA) on their optical properties. Particularly, we were interested in all optical switching and light generation in amplified spontaneous emission process in these materials.

  12. Simultaneous Rates of Ribonucleic Acid and Deoxyribonucleic Acid Syntheses for Estimating Growth and Cell Division of Aquatic Microbial Communities

    PubMed Central

    Karl, David M.

    1981-01-01

    A method for measuring rates of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) syntheses using a single radioactive precursor has been devised and tested using bacterial cultures and natural assemblages of marine and freshwater microorganisms. The procedure is based upon the uptake and incorporation of exogenous [3H]adenine into cellular adenosine triphosphate and deoxyadenosine triphosphate pools which serve as the immediate precursors for the adenine incorporated into RNA and DNA, respectively. It is proposed that the DNA/RNA rate ratio is correlated with the specific growth rate of microorganisms and can be used as an index for estimating and comparing the productivities of microbial assemblages in nature. This technique can also be used to detect discontinuous growth and cell division processes which frequently occur in surface plankton populations. The DNA/RNA rate ratios measured in a variety of aquatic ecosystems ranged from 3.3 to 31.8% without significant correlation to total microbial biomass. PMID:16345882

  13. Identification of cross-linked peptides after click-based enrichment using sequential collision-induced dissociation and electron transfer dissociation tandem mass spectrometry.

    PubMed

    Chowdhury, Saiful M; Du, Xiuxia; Tolić, Nikola; Wu, Si; Moore, Ronald J; Mayer, M Uljana; Smith, Richard D; Adkins, Joshua N

    2009-07-01

    Chemical cross-linking combined with mass spectrometry can be a powerful approach for the identification of protein-protein interactions and for providing constraints on protein structures. However, enrichment of cross-linked peptides is crucial to reduce sample complexity before mass spectrometric analysis. In addition compact cross-linkers are often preferred to provide short spacer lengths, surface accessibility to the protein complexes, and must have reasonable solubility under conditions where the native complex structure is stable. In this study, we present a novel compact cross-linker that contains two distinct features: (1) an alkyne tag and (2) a small molecule detection tag (NO(2)) to maintain reasonable solubility in water. The alkyne tag enables enrichment of the cross-linked peptides after proteolytic cleavage and coupling of an affinity tag using alkyne-azido click chemistry. Neutral loss of the small NO(2) moiety provides a secondary means of detecting cross-linked peptides in MS/MS analyses, providing additional confidence in peptide identifications. We show the labeling efficiency of this cross-linker, which we termed CLIP (click-enabled linker for interacting proteins) using ubiquitin. The enrichment capability of CLIP is demonstrated for cross-linked ubiquitin in highly complex E. coli cell lysates. Sequential collision-induced dissociation tandem mass spectrometry (CID-MS/MS) and electron transfer dissociation (ETD)-MS/MS of intercross-linked peptides (two peptides connected with a cross-linker) are also demonstrated for improved automated identification of cross-linked peptides.

  14. 21 CFR 528.1070 - Bc6 recombinant deoxyribonucleic acid construct.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... use. Five copies of a human Bc6 recombinant deoxyribonucleic acid (rDNA) construct located at the GTC.... 528.1070 Section 528.1070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... hircus) directing the expression of the human gene for antithrombin (which is intended for the treatment...

  15. 21 CFR 528.1070 - Bc6 recombinant deoxyribonucleic acid construct.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... use. Five copies of a human Bc6 recombinant deoxyribonucleic acid (rDNA) construct located at the GTC.... 528.1070 Section 528.1070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... hircus) directing the expression of the human gene for antithrombin (which is intended for the treatment...

  16. 21 CFR 528.1070 - Bc6 recombinant deoxyribonucleic acid construct.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... use. Five copies of a human Bc6 recombinant deoxyribonucleic acid (rDNA) construct located at the GTC.... 528.1070 Section 528.1070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... hircus) directing the expression of the human gene for antithrombin (which is intended for the treatment...

  17. 21 CFR 528.1070 - Bc6 recombinant deoxyribonucleic acid construct.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... use. Five copies of a human Bc6 recombinant deoxyribonucleic acid (rDNA) construct located at the GTC.... 528.1070 Section 528.1070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... hircus) directing the expression of the human gene for antithrombin (which is intended for the treatment...

  18. Four proteins synthesized in response to deoxyribonucleic acid damage in Micrococcus radiodurans.

    PubMed Central

    Hansen, M T

    1980-01-01

    Four proteins, alpha beta, gamma, and delta, preferentially synthesized in ultraviolet light-treated cells of Micrococcus radiodurans, were characterized in terms of their molecular weights and isoelectric points. Within the sublethal-dose range, the differential rate of synthesis for these proteins increased linearly with the inducing UV dose. The degree of induction reached 100-fold, and the most abundant protein beta, amounted to approximately 2% of the total newly synthesized protein after irradiation. Damage caused by ionizing radiation or by treatment with mitomycin C also provoked the synthesis of the four proteins. The proportions between the individual proteins, however, varied strikingly with the damaging agent. In contrast to treatments which introduced damage in the cellular deoxyribonucleic acid, the mere arrest of deoxyribonucleic acid replication, caused by nalidixic acid or by starvation for thymine, failed to elicit the synthesis of either protein. Repair of deoxyribonucleic acid damage requires that a number of versatile and efficient processes by employed. It is proposed that the induced proteins participate in deoxyribonucleic acid repair in M. radiodurans. Mechanisms are discussed which would allow a differentiated cellular response to damages of sufficiently distinctive nature. Images PMID:7354007

  19. Chemical modification of wheat protein-based natural polymers: grafting and cross-linking reactions with poly(ethylene oxide) diglycidyl ether and ethyl diamine.

    PubMed

    Kurniawan, Lusiana; Qiao, Greg G; Zhang, Xiaoqing

    2007-09-01

    Mobile poly(ethylene oxide) diglycidyl ether (PEODGE) segments were chemically grafted onto a soluble wheat protein (WP), and different network structures were formed via coupling reactions with ethyl diamine (EDA) in different PEODGE/EDA (PE) ratios. When the PE ratio was 1:1, linear PEs were the predominant segments grafted onto WP chains and the whole WP-PEODGE-EDA (WPE) system was still soluble with an increased molecular weight. Reducing the amount of EDA in the systems produced insoluble cross-linked WPE networks. The broad distribution of network structures and chain mobility resulted in a broad glass transition for the WPE materials. However, the glass transition started at lower temperatures, and the materials became flexible at room temperature. The PE segments were present in all rigid, intermediate, and mobile phases in WPE networks, while the proportion of mobile WP chains was increased as a result of the plasticization effect from the mobile PE segments. The mobility of the most mobile component lipid was also restricted to some extent when forming the cross-linked WPE networks. The study demonstrated that the formation of different network structures with PE segments could significantly improve the flexibility of WP materials, vary the solubility, and modify the mechanical performance of WP-based natural polymer materials.

  20. Dynamics of the sorption of copper(II) and silver(I) by materials based on sulfoethylchitosan with various degrees of crosslinking

    NASA Astrophysics Data System (ADS)

    Petrova, Yu. S.; Pestov, A. V.; Alifkhanova, L. M. k.; Neudachina, L. K.

    2017-04-01

    Optimum conditions of the dynamic concentration of copper(II) and silver(I) ions simultaneously present in a solution with N-(2-sulfoethyl)chitosan with a degree of modification equal to 0.5 and different degrees of crosslinking by glutaraldehyde are determined. The values of coefficients of selectivity K Ag/Cu are determined under dynamic conditions. It is shown that the selectivity of the sorption of silver(I) increases (compared to copper(II)) as the degree of crosslinking of sorbents based on N-(2-sulfoethyl)chitosan is raised. Mathematical treatment of the obtained dynamic curves is performed according to the Thomas, Adams-Bohart, and Yoon and Nelson models. As a result, the values of dynamic capacity of sorbents, the rate constant of the reaction, and the release time of 50% of the sorbate are determined. The quantitative desorption of copper and silver from the surface of sorbents is achieved by using 1 mol/dm3 solution of nitric acid.

  1. Aliphatic polycarbonates based on carbon dioxide, furfuryl glycidyl ether, and glycidyl methyl ether: reversible functionalization and cross-linking.

    PubMed

    Hilf, Jeannette; Scharfenberg, Markus; Poon, Jeffrey; Moers, Christian; Frey, Holger

    2015-01-01

    Well-defined poly((furfuryl glycidyl ether)-co-(glycidyl methyl ether) carbonate) (P((FGE-co-GME)C)) copolymers with varying furfuryl glycidyl ether (FGE) content in the range of 26% to 100% are prepared directly from CO2 and the respective epoxides in a solvent-free synthesis. All materials are characterized by size-exclusion chromatography (SEC), (1)H NMR spectroscopy, and differential scanning calorimetry (DSC). The furfuryl-functional samples exhibit monomodal molecular weight distributions with Mw/Mn in the range of 1.16 to 1.43 and molecular weights (Mn) between 2300 and 4300 g mol(-1). Thermal properties reflect the amorphous structure of the polymers. Both post-functionalization and cross-linking are performed via Diels-Alder chemistry using maleimide derivatives, leading to reversible network formation. This transformation is shown to be thermally reversible at 110 °C.

  2. Cross-linked cyclodextrin-based material for treatment of metals and organic substances present in industrial discharge waters

    PubMed Central

    Euvrard, Élise; Morin-Crini, Nadia; Druart, Coline; Bugnet, Justine; Martel, Bernard; Cosentino, Cesare; Moutarlier, Virginie

    2016-01-01

    Summary In this study, a polymer, prepared by crosslinking cyclodextrin (CD) by means of a polycarboxylic acid, was used for the removal of pollutants from spiked solutions and discharge waters from the surface treatment industry. In spiked solutions containing five metals, sixteen polycyclic aromatic hydrocarbons (PAH) and three alkylphenols (AP), the material exhibited high adsorption capacities: >99% of Co2+, Ni2+ and Zn2+ were removed, between 65 and 82% of the PAHs, as well as 69 to 90% of the APs. Due to the structure of the polymer and its specific characteristics, such as the presence of carboxylic groups and CD cavities, the adsorption mechanism involves four main interactions: ion exchange, electrostatic interactions and precipitation for metal removal, and inclusion complexes for organics removal. In industrial discharge waters, competition effects appeared, especially because of the presence of calcium at high concentrations, which competed with other pollutants for the adsorption sites of the adsorbent. PMID:27829889

  3. Influence of molecular weight of polymethyl(methacrylate) beads on the properties and structure of cross-linked denture base polymer.

    PubMed

    Kawaguchi, Tomohiro; Lassila, Lippo V J; Tokue, Ai; Takahashi, Yutaka; Vallittu, Pekka K

    2011-11-01

    Denture base polymers are multiphase polymers made of polymethyl(methacrylate) (PMMA) beads and monomers containing methylmethacrylate and cross-linking agent. The cross-linking agent is typically dimethacrylate but methacrylated dendrimers have been tested. The aim of this study was to investigate the influence of the molecular weight of the PMMA beads on the mechanical properties of cross-linked denture base polymers. Resin powder with three different molecular weights (Mw 120,000, 350,000, and 996,000) and a commercial autopolymerizing denture base resin (Palapress, Mw 220,000) were tested. The resin monomer liquid was applied with a methylmethacrylate mixture containing 4.6 vol% dendrimer (DD1, VTT Processes). To investigate the flexural properties, the surface microhardness of the PMMA beads, and the thickness of the swollen interpenetrating polymer network (IPN) layer on the PMMA beads, test specimens (3.3×10×65 mm) were fabricated from autopolymerizing resin using a powder/liquid ratio of 10 g/7 ml. The specimens were polymerized in distilled water maintained at 55 °C under 0.4 MPa pressure for 20 min. The flexural strength and flexural modulus (n=8/group) were measured with a three-point bending test at a crosshead speed of 5 mm/min. The Vickers hardness of the area of the polymer with PMMA beads (n=10/group) was tested using a load of 98.12 mN for 5 s. In addition, the thickness of the swollen layer on the PMMA beads was measured (n=10/group). Statistical analysis was performed using a one-way ANOVA and Tukey's test. The flexural strength of the specimens with Mw 220,000 and 350,000 PMMA beads was significantly higher than the strength of specimens with beads having other molecular weights. The flexural modulus of specimens with Mw 120,000 PMMA beads was the lowest. There was no difference in the surface microhardness among all groups. The thickness of the swollen IPN layer on specimens with 120,000 Mw PMMA beads was significantly higher than in the

  4. A MapReduce approach to diminish imbalance parameters for big deoxyribonucleic acid dataset.

    PubMed

    Kamal, Sarwar; Ripon, Shamim Hasnat; Dey, Nilanjan; Ashour, Amira S; Santhi, V

    2016-07-01

    In the age of information superhighway, big data play a significant role in information processing, extractions, retrieving and management. In computational biology, the continuous challenge is to manage the biological data. Data mining techniques are sometimes imperfect for new space and time requirements. Thus, it is critical to process massive amounts of data to retrieve knowledge. The existing software and automated tools to handle big data sets are not sufficient. As a result, an expandable mining technique that enfolds the large storage and processing capability of distributed or parallel processing platforms is essential. In this analysis, a contemporary distributed clustering methodology for imbalance data reduction using k-nearest neighbor (K-NN) classification approach has been introduced. The pivotal objective of this work is to illustrate real training data sets with reduced amount of elements or instances. These reduced amounts of data sets will ensure faster data classification and standard storage management with less sensitivity. However, general data reduction methods cannot manage very big data sets. To minimize these difficulties, a MapReduce-oriented framework is designed using various clusters of automated contents, comprising multiple algorithmic approaches. To test the proposed approach, a real DNA (deoxyribonucleic acid) dataset that consists of 90 million pairs has been used. The proposed model reduces the imbalance data sets from large-scale data sets without loss of its accuracy. The obtained results depict that MapReduce based K-NN classifier provided accurate results for big data of DNA. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  5. Molecular beacon mediated circular strand displacement strategy for constructing a ratiometric electrochemical deoxyribonucleic acid sensor.

    PubMed

    Gao, Fenglei; Du, Lili; Zhang, Yu; Tang, Daoquan; Du, Yan

    2015-07-09

    A novel ratiometric electrochemical sensor for sensitive and selective determination of deoxyribonucleic acid (DNA) had been developed based on signal-on and signal-off strategy. The target DNA hybridized with the loop portion of ferrocene (Fc) labeled hairpin probe immobilized on the gold electrode (GE), the Fc away from the surface of GE and the methylene blue (MB) was attached to an electrode surface by hybridization between hairpin probe and MB labeled primer. Such conformational changes resulted in the oxidation peak current of Fc decreased and that of MB increased, and the changes of dual signals are linear with the concentration of DNA. Furthermore, with the help of strand-displacement polymerization, polymerase catalyzed the extension of the primer and the sequential displacement of the target DNA, which led to the release of target and another polymerization cycle. Thus the circular strand displacement produced the multiplication of the MB confined near the GE surface and Fc got away from the GE surface. Therefore, the recognition of target DNA resulted in both the "signal-off" of Fc and the "signal-on" of MB for dual-signal electrochemical ratiometric readout. The dual signal strategy offered a dramatic enhancement of the stripping response. The dynamic range of the target DNA detection was from 10(-13) to 10(-8) mol L(-1) with a detection limit down to 28 fM level. Compared with the single signaling electrochemical sensor, the dual-signaling electrochemical sensing strategy developed in this paper was more selective. It would have important applications in the sensitive and selective electrochemical determination of other small molecules and proteins.

  6. Generation of Pretilt Angle for Nematic Liquid Crystal Using the Photodimerization Method on Various New Photo-Crosslinkable Polyimide Based Polymers

    NASA Astrophysics Data System (ADS)

    Hwang, Jeoung-Yeon; Seo, Dae-Shik; Son, Jong-Ho; Suh, Dong Hack

    2001-07-01

    We synthesized the various new photo-crosslinkable polyimide based polymers and generation of pretilt angle for a nematic liquid crystal (NLC) using a photodimerization method on the photopolymers was studied. A good thermal stability of the photopolymers was measured by thermogravimatric analysis (TGA) measurement until 450°C. The NLC pretilt angle generated was about 2.5°-3.0° by polarized UV exposure on the photopolymers containing a biphenyl (BP), decyl (De), and cholesteryl(chol), chalcone(Chal) group, respectively. However, low pretilt angle of the NLC was measured by polarized UV exposure on the photopolymers containing the fluorine and chalcone group. The NLC pretilt angle generated is attributed to the biphenyl and alkyl moieties, and the photo-dimerized chalcone group of the photopolymer.

  7. A novel heterotrifunctional peptide-based cross-linking reagent for facile access to bioconjugates. Applications to peptide fluorescent labelling and immobilisation.

    PubMed

    Clavé, Guillaume; Boutal, Hervé; Hoang, Antoine; Perraut, François; Volland, Hervé; Renard, Pierre-Yves; Romieu, Anthony

    2008-09-07

    A convenient, versatile and straightforward synthesis of a novel heterotrifunctional peptide-based linker molecule is described. This generic bio-labelling reagent contains an amine-reactive N-hydroxysuccinimidyl carbamate moiety, an aldehyde/ketone-reactive aminooxy group and a thiol group with a propensity to form urea, oxime and thioether linkages respectively. The full chemical orthogonality between the free aminooxy and thiol functionalities was demonstrated through the preparation of a fluorescent reagent suitable for the selective staining of a carboxaldehyde-modified surface by means of oxime ligation. The absence of reactivity of these two functions toward the nucleophile-sensitive active carbamate was obtained by using temporary aminooxy- and thiol-protecting groups removable under mild conditions. The utility of the linker molecule to cross-link three different molecular partners has been illustrated by the preparation of fluorescent tripod-functionalised surfaces which may be useful in developing new peptide microarrays and related immunosensors.

  8. Preparation and characterization of highly cross-linked polyimide aerogels based on polyimide containing trimethoxysilane side groups.

    PubMed

    Pei, Xueliang; Zhai, Wentao; Zheng, Wenge

    2014-11-11

    In this study, highly cross-linked and completely imidized polyimide aerogels were prepared from polyimide containing trimethoxysilane side groups, which was obtained as the condensation product of polyimide containing acid chloride side groups and 3-aminopropyltrimethoxysilane. After adding water and acid catalyst, the trimethoxysilane side groups hydrolyzed and condensed one another, and a continuous increase in the complex viscosities of the polyimide solutions with time was observed. The formed polyimide gels were dried by freeze-drying from tert-butyl alcohol to obtain polyimide aerogels, which consisted of a three-dimensional network of polyimide fibers tangled together. By varying the solution concentration of the polyimide containing trimethoxysilane side groups, polyimide aerogels with different densities (ranging from 0.19 to 0.42 g/cm(3)) were obtained. The resulting polyimide aerogels had small pore diameter (ranging from 20.7 to 58.3 nm), high surface area (ranging from 310 to 344 m(2)/g), high 5% weight loss temperature in air (at about 440 °C), and an excellent mechanical property. In addition, the glass transition temperature (349 °C) of the polyimide aerogels was much higher than that (210 °C) of the corresponding linear polyimide. So, even after being heated at 300 °C for 30 min, the porous structure of the polyimide aerogels was not completely destroyed.

  9. Development of a biosensor based on gilo peroxidase immobilized on chitosan chemically crosslinked with epichlorohydrin for determination of rutin.

    PubMed

    Zwirtes de Oliveira, Inês Rosane W; Fernandes, Suellen Cadorin; Vieira, Iolanda Cruz

    2006-05-03

    A new reagentless biosensor for the square-wave voltammetric determination of rutin in pharmaceutical formulations was developed by immobilization of gilo (Solanum gilo) crude extract in chitosan matrix. The gilo tissue acts as a source of peroxidase. The highest biosensor performance was obtained after immobilization of the peroxidase in chemically crosslinked chitosan with epichlorohydrin and glutaraldehyde that was incorporated in a carbon paste electrode. In the presence of hydrogen peroxide this enzyme catalyses the oxidation of rutin to quinone and the electrochemical reduction of the product was obtained at a fixed potential of +124 mV versus Ag/AgCl (3.0 M KCl). The performance and factors influencing the resulting biosensor were studied in detail. The bioelectrode exhibited a linear response for rutin concentrations from 3.4x10(-7) to 7.2x10(-6) M (r=0.9998) and the recovery of rutin from the samples ranged from 96.2 to 102.4%. The detection and quantification limits were 2.0x10(-8) and 6.3x10(-8) M, respectively. The relative standard deviation was less than 1.0% for solutions containing 3.4x10(-7) to 7.2x10(-6) M rutin in 0.1 M phosphate buffer solution at pH 7.0 (n=10). The lifetime of this biosensor was 8 months (at least 500 determinations).

  10. A Cross-Linking Succinonitrile-Based Composite Polymer Electrolyte with Uniformly Dispersed Vinyl-Functionalized SiO2 Particles for Li-Ion Batteries.

    PubMed

    Liu, Kai; Ding, Fei; Liu, Jiaquan; Zhang, Qingqing; Liu, Xingjiang; Zhang, Jinli; Xu, Qiang

    2016-09-14

    A cross-linking succinonitrile (SN)-based composite polymer electrolyte (referred to as "CLPC-CPE"), in which vinyl-functionalized SiO2 particles connect with trimethylolpropane propoxylate triacrylate (TPPTA) monomers by covalent bonds, was prepared by an ultraviolet irradiation (UV-curing) process successfully. Vinyl-functionalized SiO2 particles may react with TPPTA monomers to form a cross-linking network within the SN-based composite polymer electrolyte under ultraviolet irradiation. Vinyl-functionalized SiO2 particles as the fillers of polymer electrolyte may improve both the thermal stability of CLPC-CPE and interfacial compatibility between CLPC-CPE and electrodes effectively. There is no weight loss for CLPC-CPE until above 230 °C. The ionic conductivity of CLPC-CPE may reach 7.02 × 10(-4) S cm(-1) at 25 °C. CLPC-CPE has no significant oxidation current until up to 4.6 V (vs Li/Li(+)). The cell of LiFePO4/CLPC-CPE/Li has presented superior cycle performance and rate capability. The cell of LiFePO4/CLPC-CPE/Li may deliver a high discharge capacity of 154.4 mAh g(-1) at a rate of 0.1 C after 100 charge-discharge cycles, which is similar than that of the control cell of LiFePO4/liquid electrolyte/Li. Furthermore, the cell of LiFePO4/CLPC-CPE/Li can display a high discharge capacity of 112.7 mAh g(-1) at a rate of 2 C, which is higher than that of the cells assembled with other plastic crystal polymer electrolyte reported before obviously.

  11. Amphiphilic model conetworks based on cross-linked star copolymers of benzyl methacrylate and 2-(dimethylamino)ethyl methacrylate: synthesis, characterization, and DNA adsorption studies.

    PubMed

    Achilleos, Demetra S; Georgiou, Theoni K; Patrickios, Costas S

    2006-12-01

    Six amphiphilic model conetworks of a new structure, that of cross-linked "in-out" star copolymers, were synthesized by the group transfer polymerization (GTP) of the hydrophobic monomer benzyl methacrylate (BzMA) and the ionizable hydrophilic monomer 2-(dimethylamino)ethyl methacrylate (DMAEMA) in a one-pot preparation. The synthesis took place in tetrahydrofuran (THF) using tetrabutylammonium bibenzoate (TBABB) as the catalyst, 1-methoxy-1-(trimethylsiloxy)-2-methyl-propene (MTS) as the initiator, and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. Three heteroarm star-, two star block-, one statistical copolymer star-, and one homopolymer star-based networks were prepared. The synthesis of these star-based networks involved four to six steps, including the preparation of the linear (co)polymers, the "arm-first" and the "in-out" star copolymers, and finally the network. The precursors and the extractables were characterized using gel permeation chromatography (GPC) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The degrees of swelling (DSs) of all the networks were measured in THF, while the aqueous DSs were measured as a function of pH. The DSs at low pH were higher than those at neutral or high pH because of the protonation of the DMAEMA units and were found to be dependent on the structure of the network. The DSs in THF were higher than those in neutral water and were independent of the structure. Finally, DNA adsorption studies onto the networks indicated that the DNA binding was governed by electrostatics.

  12. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

    1977-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree. C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  13. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

    1976-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  14. Chromatographic isolation of the functionally active MutS protein covalently linked to deoxyribonucleic acid.

    PubMed

    Monakhova, Mayya; Ryazanova, Alexandra; Hentschel, Andreas; Viryasov, Mikhail; Oretskaya, Tatiana; Friedhoff, Peter; Kubareva, Elena

    2015-04-10

    DNA metabolism is based on formation of different DNA-protein complexes which can adopt various conformations. To characterize functioning of such complexes, one needs a solution-based technique which allows fixing a complex in a certain transient conformation. The crosslinking approach is a popular tool for such studies. However, it is under debate if the protein components retain their natural activities in the resulting crosslinked complexes. In the present work we demonstrate the possibility of obtaining pure DNA conjugate with functionally active protein using as example MutS protein from Escherichia coli mismatch repair system. A conjugate of a chemically modified mismatch-containing DNA duplex with MutS is fixed by thiol-disulfide exchange reaction. To perform a reliable test of the protein activity in the conjugate, such conjugate must be thoroughly separated from the uncrosslinked protein and DNA prior to the test. In the present work, we employ anion exchange chromatography for this purpose for the first time and demonstrate this technique to be optimal for the conjugate purification. The activity test is a FRET-based detection of DNA unbending. We show experimentally that MutS in the conjugate retains its ability to unbend DNA in response to ATP addition and find out for the first time that the DNA unbending rate increases with increasing ATP concentration. Since the crosslinked complexes contain active MutS protein, they can be used in further experiments to investigate MutS interactions with other proteins of the mismatch repair system.

  15. Effect of post crosslinking haze on the repeatability of Scheimpflug-based and slit-scanning imaging devices

    PubMed Central

    Shetty, Rohit; Agrawal, Aarti; Deshmukh, Rashmi; Kaweri, Luci; Rao, Harsha L; Nagaraja, Harsha; Jayadev, Chaitra

    2017-01-01

    Purpose: The aim of this study was to analyze the effect of postcollagen crosslinking (CXL) haze on the measurement and repeatability of pachymetry and mean keratometry (Km) of four corneal topographers. Materials and Methods: Sixty eyes of sixty patients with progressive keratoconus who had undergone accelerated CXL (ACXL) underwent imaging with a scanning slit imaging device (Orbscan II) and three Scheimpflug imaging devices (Pentacam HR, Sirius, and Galilei). Post-ACXL haze was measured using the densitometry software on the Pentacam HR. Readings of the thinnest corneal thickness (TCT) and Km from three scans of each device were analyzed. Effect of haze on the repeatability of TCT and Km measurements was evaluated using regression models. Repeatability was assessed by coefficient of variation. Results: Corneal densitometry in different zones affected the repeatability of TCT measurement of Orbscan (P < 0.05) significantly but not the repeatability of TCT with Pentacam HR and Sirius (P = 0.03 and 0.05, respectively). Km values were affected by haze when measured with the Pentacam HR (P < 0.05). The repeatability of Km readings for all devices was unaffected by haze. In the anterior 0–2 mm and 2–6 mm zone, TCT (P = 0.43 and 0.45, respectively), Km values (P = 0.4 and 0.6, respectively), repeatability of TCT (P = 0.1 in both zones), and Km (P = 0.5 and 0.1, respectively) with Galilei were found to be the most reliable. Conclusion: Galilei measurements appear to be least affected by post-ACXL haze when compared with other devices. Hence, topography measurements in the presence of haze need to be interpreted with caution. PMID:28513495

  16. Excision of pyrimidine dimers from nuclear deoxyribonucleic acid in ultraviolet-irradiated Dictyostelium discoideum

    SciTech Connect

    Clark, J.M.; Deering, R.A.

    1987-02-01

    A sensitive endonuclease assay was used to study the fate of pyrimidine dimers introduced by ultraviolet irradiation into the nuclear deoxyribonucleic acid of the cellular slime mold Dictyostellium discoideum. Analysis of the frequency of T4 endonuclease V-induced single-strand breaks by alkaline sucrose gradient sedimentation showed that strain NC4 (rad/sup +/) removed >98% of the dimers induced by irradiation at 40 J/m/sup 2/ (254 nm) within 215 min after irradiation. HPS104 (radC44), a mutant sensitive to ultraviolet irradiation, removed 91% under these conditions, although at a significantly slower rate than NC4: only 8% were removed during the 10- to 15- min period immediately after irradiation, whereas NC4 excised 64% during this interval. HPS104 thus appears to be deficient in the activity(ies) responsible for rapidly incising ultraviolet-irradiated nuclear deoxyribonucleic acid at the sites of pyrimidine dimers.

  17. INCORPORATION OF DEOXYRIBONUCLEIC ACID IN THE BACILLUS SUBTILIS TRANSFORMATION SYSTEM1

    PubMed Central

    Young, F. E.; Spizizen, John

    1963-01-01

    Young, F. E. (Western Reserve University Cleveland, Ohio) and John Spizizen. Incorporation of deoxyribonucleic acid in the Bacillus subtilis transformation system. J. Bacteriol. 86:392–400. 1963.—The optimal conditions for the incorporation of deoxyribonucleic acid (DNA) were studied. In competent cells, the irreversible binding of DNA was influenced by temperature, hydrogen ion concentration, and aeration. Divalent cations, such as barium, strontium, calcium, or magnesium, were required. Under suboptimal environmental conditions and with metabolic inhibitors, the process of transformation was decreased to a greater extent than was incorporation of DNA. Under conditions of phosphate depletion, the incorporation of P32 increased. However, the frequency of transformation decreased. This inducible process was not related to competence. PMID:14066414

  18. Blood lymphocyte ultrastructure and deoxyribonucleic acid content in children with systemic lupus erythematosis.

    PubMed

    Ptasekas, R; Matulis, A; Urmonas, V; Graziene, V; Zukiene, G

    1980-01-01

    Two varieties of peripheral blood lymphocytes have been disclosed in systemic lupus erythematosus (SLE) cases: one showing signs of degradation and nuclear chromatine elimination and the other one manifesting a state of biological activation, possibly of an immunologic nature. This karyostructural lymphocyte heterogeneity in SLE may cause a great scattering of these cells on histograms in respect to their nuclear deoxyribonucleic acid content determined by cytophotometry. On the other hand, the expressiveness of the scattering and the degree of predominance of negative tendency towards proliferation (with a shift to the left from 2 n) may thereby serve as a very objective quantitative indication of nuclear structure degradation and of loss by lymphocytes of chromatine with deoxyribonucleic acid during SLE.

  19. Hyper-crosslinked resins filled with multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Castaldo, R.; Ambrogi, V.; Avolio, R.; Cocca, C.; Errico, M. E.; Gentile, G.; Avella, M.; Carfagna, C.

    2016-05-01

    Hyper-crosslinked styrenic resins are tipically prepared by suspension polymerization of a gel-type precursor and successive crosslinking by Friedel-Crafts reaction. This kind of polymers displays high specific surface area and excellent sorption properties. Hyper-crosslinked resins and nanocomposites containing multiwalled carbon nanotubes (MWCNT) were prepared in this study. Structure and properties of hyper-crosslinked resins containing MWCNT were investigated. Moreover, a new synthetic process of the nanocomposites was developed, based on the bulk polymerization of the precursor resin. The effect of the synthetic procedure and the addition of nanofillers on the material specific surface area, porosity and adsorption properties were explored.

  20. Microbes encapsulated within crosslinkable polymers

    DOEpatents

    Chidambaram, Devicharan; Liu, Ying; Rafailovich, Miriam H

    2013-02-05

    The invention relates to porous films comprising crosslinked electrospun hydrogel fibers. Viable microbes are encapsulated within the crosslinked electrospun hydrogel fibers. The crosslinked electrospun hydrogel fibers are water insoluble and permeable. The invention also relates to methods of making and using such porous films.

  1. Physically cross-linked polymer binder based on poly(acrylic acid) and ion-conducting poly(ethylene glycol-co-benzimidazole) for silicon anodes

    NASA Astrophysics Data System (ADS)

    Lim, Sanghyun; Lee, Kukjoo; Shin, Inseop; Tron, Artur; Mun, Junyoung; Yim, Taeeun; Kim, Tae-Hyun

    2017-08-01

    The practical applications of Si electrodes in lithium-ion batteries are limited since they undergo large changes in volume during charge and discharge, and consequently become highly deteriorated. A novel binder system holding silicon particles together and preventing disintegration of the electrode during operation hence needs to be developed to enable reliable cycleability. In the current work, such a new polymer binder system, based on poly(acrylic acid) (PAA) and poly(ethylene glycol-co-benzimidazole) (PEGPBI), is developed for silicon anodes. The physical crosslinking using acid-base interactions between PAA and PBI, together with the ion-conducting PEG group, yields physical properties for the resulting PAA-PEGPBI-based anodes that are better than those of electrodes based on the currently available PAA binder, and yields good cell performances. A Si-based electrode with high loading levels of 1.0-1.3 mg cm-2 (0.7-0.91 Si mg cm-2) is reliably manufactured using specifically PAA-PEGPBI-2, which is made with 2 wt% of PEGPBI relative to PAA, and shows a very high capacity value of 1221 mAh g-1 at a rate of 0.5 C after 50 cycles, and a high capacity value of more than 1600 mAh g-1 at a high rate of 2 C.

  2. Excretion of glutamic acid in Citrobacter intermedius C3 associated with plasmid deoxyribonucleic acid.

    PubMed Central

    Jofre, J; Prieto, M J; Tomás, J; Parés, R

    1979-01-01

    Several mutants of Citrobacter intermedius C3 lacking both the ability to synthesize proline and the ability to excrete glutamic acid were isolated by treatment with nitrosoguanidine. No revertants for either characteristic were obtained from these mutants. The ability to excrete glutamic acid was transferred to those mutants with very high frequencies in mating experience by using auxotropic excreting strains as donors. Moreover, the ability to synthesize proline was transferred together with the ability to excrete glutamic acid when an excreting strain was used as donor. The transconjugants showed a rapid spontaneous curing of both genetic markers. It was shown by two different methods that a band of covalently closed circular deoxyribonucleic acid is present in the cesium chloride gradients corresponding to the wild type and excretor mutants. Nonexcretor mutants described herein lacked such a band. Pro + transformants that were also excretors were obtained with plasmid deoxyribonucleic acid isolated either from wild type or from an excretor mutant. These data strongly indicate that glutamic acid excretion in C. intermedius C3 is related to the presence of extrachromosomal deoxyribonucleic acid. PMID:457593

  3. Imidate-Based Cross-Linkers for Structural Proteomics: Increased Charge of Protein and Peptide Ions and CID and ECD Fragmentation Studies

    NASA Astrophysics Data System (ADS)

    Koolen, Hector H. F.; Gomes, Alexandre F.; Schwab, Nicolas V.; Eberlin, Marcos N.; Gozzo, Fabio C.

    2014-07-01

    Chemical cross-linking is an attractive low-resolution technique for structural studies of protein complexes. Distance constraints obtained from cross-linked peptides identified by mass spectrometry (MS) are used to construct and validate protein models. Amidinating cross-linkers such as diethyl suberthioimidate (DEST) have been used successfully in chemical cross-linking experiments. In this work, the application of a commercial diimidate cross-linking reagent, dimethyl suberimidate (DMS), was evaluated with model peptides and proteins. The peptides were designed with acetylated N-termini followed by random sequences containing two Lys residues separated by an Arg residue. After cross-linking reactions, intra- and intermolecular cross-linked species were submitted to CID and ECD dissociations to study their fragmentation features in the gas phase. Fragmentation of intramolecular peptides by collision induced dissociation (CID) demonstrates a unique two-step fragmentation pathway involving formation of a ketimine as intermediate. Electron capture and electron transfer dissociation (ECD and ETD) experiments demonstrated that the cyclic moiety is not dissociated. Intermolecular species demonstrated previously described fragmentation behavior in both CID and ECD experiments. The charge state distributions (CSD) obtained after reaction with DMS were compared with those obtained with disuccinimidyl suberate (DSS). CSDs for peptides and proteins were increased after their reaction with DMS, owing to the higher basicity of DMS modified species. These features were also observed in LC-MS experiments with bovine carbonic anhydrase II (BCA) after cross-linking with DMS and tryptic proteolysis. Cross-linked peptides derived from this protein were identified at high confidence and those species were in agreement with the crystal structure of BCA.

  4. Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization.

    PubMed

    Zhang, Jing; Liu, Jingjiang; Zuo, Yong; Wang, Rongmin; Xiong, Yubing

    2015-09-18

    In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3'-bis-1-vinyl imidazolium bromides ([CnVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5-25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO₂ and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO₂ conversion.

  5. Chitosan membranes for tissue engineering: comparison of different crosslinkers.

    PubMed

    Ruini, F; Tonda-Turo, C; Chiono, V; Ciardelli, G

    2015-11-03

    Chitosan (CS), a derivative of the naturally occurring biopolymer chitin, is an attractive material for biomedical applications thanks to its biocompatibility, biodegradability, antibacterial properties and ability to enhance cell adhesion and growth compared to other biopolymers. However, the physical and mechanical stability of CS based materials in aqueous solutions is limited and crosslinking agents are required to increase CS performances in a biological environment. In this work, the effect of three highly-biocompatible crosslinkers as genipin (GP), γ-glycidoxypropyltrimethoxysilane (GPTMS), dibasic sodium phosphate (DSP) and a combination of GPTMS and DSP (GPTMS_DSP) on CS physicochemical, thermal, morphological, mechanical properties, swelling and degradation behavior was investigated. Infrared spectroscopy and thermogravimetric analyses confirmed the chemical reaction between CS and the different crosslinkers. CS wettability was enhanced when CS was DSP ionically crosslinked showing contact angle values of about 65° and exhibiting a higher swelling behavior compared to covalently crosslinked films. Moreover, all the crosslinking methods analyzed improved the stability of CS in aqueous media, showed model molecule permeation in time and increased the mechanical properties when compared with non-crosslinked films. The possibility to tailor the final properties of CS scaffolds through crosslinking is a key strategy in applying CS in different biomedical and tissue engineering applications. The obtained results reveal that the optimization of the crosslinking mechanism provides CS membrane properties required in different biomedical applications.

  6. Dipentaerythritol penta-/hexa-acrylate based-highly cross-linked hybrid monolithic column: Preparation and its applications for ultrahigh efficiency separation of proteins.

    PubMed

    Ma, Junqian; Dai, Qian; Li, Xueyun; Zhu, Xianghui; Ma, Teng; Qiao, Xiaoqiang; Shen, Shigang; Liu, Xiuhua

    2017-04-22

    In this study, multi-acrylate based dipentaerythritol penta-/hexa-acrylate (DPEPA) was exploited for fabrication of highly cross-linked hybrid monolithic column by copolymerization with polyhedral oligomeric silsesquioxane methacryl substituted (POSS-MA) via a "one-pot" method. The new DPEPA-POSS hybrid monolithic column was respectively characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption/desorption measurement. When it was used for the separation of amides, thioureas and positional isomers of phenols, ultrahigh column efficiency separation (up to 511,000 N m(-1)) was achieved with excellent selectivity. Moreover, intact protein standards could be efficiently separated with minimum tailing peaks, outperforming the commercially available silica-based C8 column. Furthermore, successful separation of complex egg white proteins and expressed BARD1 BRCT domains protein sample was also achieved with good chromatographic performance. In the future work, the DPEPA-POSS hybrid monolithic column will be further exploited and applied in capillary electrochromatography as well as the top-down based proteome research.

  7. Novel hydrogels based on carboxyl pullulan and collagen crosslinking with 1, 4-butanediol diglycidylether for use as a dermal filler: initial in vitro and in vivo investigations.

    PubMed

    Li, Xian; Xue, Wenjiao; Zhu, Chenhui; Fan, Daidi; Liu, Yannan; XiaoxuanMa

    2015-12-01

    Novel hydrogels based on carboxyl pullulan (PC) and human-like collagen (HLC) crosslinking with 1,4-butanediol diglycidyl ether (BDDE) are promising soft fillers for tissue engineering due to their highly tunable properties. Recent studies, however, have shown that incorporating hyaluronic acid and BDDE results in hydrogels with a microporous structure, a large pore size and high porosity, which reduce cell adhesion and enhance degradation in vivo. To improve biocompatibility and prevent biodegradation, the use of PC to replace hyaluronic acid in the fabrication of PC/BDDE (PCB) and PC/BDDE/HLC (PCBH) hydrogels was investigated. Preparation of gels with PC is a promising strategy due to the high reactivity, superb selectivity, and mild reaction conditions of PC. In particular, the Schiff base reaction of HLC and PC produces the novel functional group -RCONHR' in PCBH hydrogels. Twenty-four weeks after subcutaneous injection of either PCB or PCBH hydrogel in mice, the surrounding tissue inflammation, enzymatic response and cell attachment were better compared to hyaluronic acid-based hydrogels. However, the biocompatibility, cytocompatibility and non-biodegradability of PCBH were milder than those of the PCB hydrogels both in vivo and in vitro. These results show that the proposed use of PC and HLC for the fabrication of hydrogels is a promising strategy for generating soft filler for tissue engineering.

  8. Cross-linking Chemistry of Squid Beak*

    PubMed Central

    Miserez, Ali; Rubin, Daniel; Waite, J. Herbert

    2010-01-01

    In stark contrast to most aggressive predators, Dosidicus gigas (jumbo squids) do not use minerals in their powerful mouthparts known as beaks. Their beaks instead consist of a highly sclerotized chitinous composite with incremental hydration from the tip to the base. We previously reported l-3,4-dihydroxyphenylalanine (dopa)-histidine (dopa-His) as an important covalent cross-link providing mechanical strengthening to the beak material. Here, we present a more complete characterization of the sclerotization chemistry and describe additional cross-links from D. gigas beak. All cross-links presented in this report share common building blocks, a family of di-, tri-, and tetra-histidine-catecholic adducts, that were separated by affinity chromatography and high performance liquid chromatography (HPLC) and identified by tandem mass spectroscopy and proton nuclear magnetic resonance (1H NMR). The data provide additional insights into the unusually high cross-link density found in mature beaks. Furthermore, we propose both a low molecular weight catechol, and peptidyl-dopa, to be sclerotization agents of squid beak. This appears to represent a new strategy for forming hard tissue in animals. The interplay between covalent cross-linking and dehydration on the graded properties of the beaks is discussed. PMID:20870720

  9. Cross-linking chemistry of squid beak.

    PubMed

    Miserez, Ali; Rubin, Daniel; Waite, J Herbert

    2010-12-03

    In stark contrast to most aggressive predators, Dosidicus gigas (jumbo squids) do not use minerals in their powerful mouthparts known as beaks. Their beaks instead consist of a highly sclerotized chitinous composite with incremental hydration from the tip to the base. We previously reported l-3,4-dihydroxyphenylalanine (dopa)-histidine (dopa-His) as an important covalent cross-link providing mechanical strengthening to the beak material. Here, we present a more complete characterization of the sclerotization chemistry and describe additional cross-links from D. gigas beak. All cross-links presented in this report share common building blocks, a family of di-, tri-, and tetra-histidine-catecholic adducts, that were separated by affinity chromatography and high performance liquid chromatography (HPLC) and identified by tandem mass spectroscopy and proton nuclear magnetic resonance ((1)H NMR). The data provide additional insights into the unusually high cross-link density found in mature beaks. Furthermore, we propose both a low molecular weight catechol, and peptidyl-dopa, to be sclerotization agents of squid beak. This appears to represent a new strategy for forming hard tissue in animals. The interplay between covalent cross-linking and dehydration on the graded properties of the beaks is discussed.

  10. The effect of cross-linking on the molecular dynamics of the segmental and β Johari-Goldstein processes in polyvinylpyrrolidone-based copolymers.

    PubMed

    Redondo-Foj, Belén; Sanchis, María Jesús; Ortiz-Serna, Pilar; Carsí, Marta; García, José Miguel; García, Félix Clemente

    2015-09-28

    The effect of the cross-link density on the molecular dynamics of copolymers composed of vinylpyrrolidone (VP) and butyl acrylate (BA) was studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). A single glass transition was detected by DSC measurements. The dielectric spectra exhibit conductive processes and three dipolar relaxations labeled as α, β and γ in the decreasing order of temperatures. The cross-linker content affects both α and β processes, but the fastest γ process is relatively unaffected. An increase of cross-linking produces a typical effect on the α process dynamics: (i) the glass transition temperature is increased, (ii) the dispersion is broadened, (iii) its strength is decreased and (iv) the relaxation times are increased. However, the β process, which possesses typical features of a pure Johari-Goldstein relaxation, unexpectedly loses the intermolecular character for the highest cross-linker content.

  11. Macromolecular cross-linked polybenzimidazole based on bromomethylated poly (aryl ether ketone) with enhanced stability for high temperature fuel cell applications

    NASA Astrophysics Data System (ADS)

    Wang, Shuang; Zhao, Chengji; Ma, Wenjia; Zhang, Na; Liu, Zhongguo; Zhang, Gang; Na, Hui

    2013-12-01

    A series of macromolecular cross-linked polybenzimidazole (PBI) membranes have been successfully prepared for the high temperature proton exchange membrane fuel cell (HT-PEMFC) applications. Bromomethylated poly (aryl ether ketone) (BrPAEK) is synthesized and used as a macromolecular cross-linker, the cross-linking reaction can be accomplished at 160 °C using an easy facial heating treatment. The resulting cross-linked membranes CBrPBI-X (X is the weight fraction of the cross-linker) display excellent mechanical strength. After phosphoric acid (PA) doping, the mechanical strength and proton conductivity of the PA/CBrPBI-X membranes are both enhanced comparing with the pristine PA/PBI. Considering the tradeoff of the mechanical strength and proton conductivity, 10 wt% BrPAEK is demonstrated to be an optimum content in the matrix. For instance, the proton conductivity of PA/CBrPBI-10 is 0.038 S cm-1 at 200 °C, which is higher than that of pristine PA/PBI with the proton conductivity of 0.029 S cm-1 at the same temperature. Other properties of the cross-linked membranes are also investigated in detail, including the oxidative stability, solubility and thermal stability. All the results indicate that the PA/CBrPBI-10 membrane has the potential application in HT-PEMFCs.

  12. Biocompatibility of two model elastin-like recombinamer-based hydrogels formed through physical or chemical crosslinking for various applications in tissue engineering and regenerative medicine.

    PubMed

    Ibáñez-Fonseca, Arturo; Ramos, Teresa L; de Torre, Israel González; Sánchez-Abarca, Luis Ignacio; Muntión, Sandra; Arias, Francisco Javier; Del Cañizo, María Consuelo; Alonso, Matilde; Sánchez-Guijo, Fermín; Rodríguez-Cabello, José Carlos

    2017-09-01

    Biocompatibility studies, especially innate immunity induction, in vitro and in vivo cytotoxicity, and fibrosis, are often lacking for many novel biomaterials including recombinant protein-based ones, such as elastin-like recombinamers (ELRs), and has not been extensively explored in the scientific literature, in contrast to traditional biomaterials. Herein we present the results from a set of experiments designed to elucidate the preliminary biocompatibility of two types of ELRs that are able to form extracellular matrix-like hydrogels through either physical or chemical crosslinking, both of which are intended for different applications in tissue engineering and regenerative medicine (TERM). Initially we present in vitro cytocompatibility results obtained upon culturing HUVECs on ELR substrates, showing optimal proliferation up to 9 days. Regarding in vivo cytocompatibility, luciferase-expressing hMSCs were viable for at least 4 weeks in terms of bioluminescence emission when embedded in ELR hydrogels and injected subcutaneously into immunosuppressed mice. Furthermore, both types of ELR-based hydrogels were injected subcutaneously in immunocompetent mice and serum TNFα, IL-1β, IL-4, IL-6 and IL-10 concentrations were measured by ELISA, confirming the lack of inflammatory response, as also observed upon macroscopic and histological evaluation. All these findings suggest that both types of ELRs possess broad biocompatibility, thus making them very promising for TERM-related applications. This article is protected by copyright. All rights reserved.

  13. Lambda bacteriophage-mediated transduction of ColE1 deoxyribonucleic acid having a lambda bacteriophage-cohesive end site: selection of packageable-length deoxyribonucleic acid.

    PubMed Central

    Umene, K; Shimada, K; Tsuzuki, T; Mori, R; Takagi, Y

    1979-01-01

    An in vitro recombinant ColE1-cos lambda deoxyribonucleic acid (DNA) molecule, pKY96, has 70% of the length of lambda phage DNA. The process of lambda phage-mediated transduction of pKY96 generated a small amount of transducing phage particles containing ColE1-cos lambda DNA molecules of 80 or 101% of the length of lambda phage DNA, in addition to those containing original pKY96 DNA molecules. The newly isolated larger plasmid DNAs were transduced 100 times more efficiently than pKY96 DNA. Their structures were compared with that of a prototype pKY96 DNA, and the mechanism of the formation of these molecules is discussed. Images PMID:158007

  14. Stable and biocompatible genipin-inducing interlayer-crosslinked micelles for sustained drug release

    NASA Astrophysics Data System (ADS)

    Dai, Yu; Zhang, Xiaojin

    2017-05-01

    To develop the sustained drug release system, here we describe genipin-inducing interlayer-crosslinked micelles crosslinked via Schiff bases between the amines of amphiphilic linear-hyperbranched polymer poly(ethylene glycol)-branched polyethylenimine-poly( ɛ-caprolactone) (PEG-PEI-PCL) and genipin. The generation of Schiff bases was confirmed by the color changes and UV-Vis absorption spectra of polymeric micelles after adding genipin. The particle size, morphology, stability, in vitro cytotoxicity, drug loading capacity, and in vitro drug release behavior of crosslinked micelles as well as non-crosslinked micelles were characterized. The results indicated that genipin-inducing interlayer-crosslinked micelles had better stability and biocompatibility than non-crosslinked micelles and glutaraldehyde-inducing interlayer-crosslinked micelles. In addition, genipin-inducing interlayer-crosslinked micelles were able to improve drug loading capacity, reduce the initial burst release, and achieve sustained drug release.

  15. Preliminary study of highly cross-linked hyaluronic acid-based combination therapy for management of knee osteoarthritis-related pain

    PubMed Central

    Palmieri, Beniamino; Rottigni, Valentina; Iannitti, Tommaso

    2013-01-01

    Background Hyaluronic acid has been extensively used for treatment of knee osteoarthritis due to its anti-inflammatory properties and its ability to act as a synovial lubricant. Furthermore, it has found application in combination with other drugs in the dermatological field and in pre-clinical studies in animal models of osteoarthritis. Experimental evidence suggests that a combination of this macromolecule with other drugs may act as a slow-release depot. However, to date, to the best of our knowledge, no one has tested local intra-articular delivery of highly cross-linked hyaluronic acid combined with bisphosphonate or nonsteroidal anti-inflammatory drugs for management of knee osteoarthritis pain in the clinical setting. The aim of the present randomized double-blind study was to investigate, for the first time, the effect of a highly cross-linked hyaluronic acid, Variofill®, alone or in combination with diclofenac sodium or sodium clodronate, for management of bilateral knee osteoarthritis-related pain. Methods Sixty-two patients with symptomatic bilateral medial tibiofemoral knee osteoarthritis (Kellgren–Lawrence grade II and III) and pain in both knees corresponding to a daily visual analog scale (VAS) score ≥ 30 in the month before the beginning of the study were included in this investigation. Patients were divided into three groups: group 1, treated with an injection of hyaluronic acid alone (66 mg) into each knee; group 2, treated with an injection of hyaluronic acid (49.5 mg) plus diclofenac sodium (5 mg) into each knee; group 3, treated with an injection of hyaluronic acid (49.5 mg) plus sodium clodronate (5 mg) into each knee. Patients also underwent blood tests for measurement of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) immediately before and at 6-month follow-up. Results Hyaluronic acid alone and in combination with sodium clodronate or diclofenac sodium produced a significant improvement in mean VAS pain score at 3 and

  16. Kinetic and spectrophotometric studies on the renaturation of deoxyribonucleic acid.

    PubMed

    Thrower, K J; Peacocke, A R

    1968-10-01

    The kinetics of the renaturation of Escherichia coli DNA in 0.4-1.0m-sodium chloride at temperatures from 60 degrees to 90 degrees have been studied. The extent of renaturation was a maximum at 65 degrees to 75 degrees and increased with ionic strength, and the rate constant increased with both ionic strength and temperature. The energy and entropy of activation of renaturation were calculated to be 6-7kcal.mole(-1) and -40cal.deg.(-1)mole(-1) respectively. It has been shown that renaturation is a second-order process for 5hr. under most conditions. The results are consistent with a reaction in which the rate-controlling step is the diffusion together of two separated complementary DNA strands and the formation of a nucleus of base pairs between them. The kinetics of the renaturation of T7-phage DNA and Bordetella pertussis DNA have also been studied, and their rates of renaturation related quantitatively to the relative heterogeneity of the DNA samples. By analysis of the spectra of DNA at different stages during renaturation it was shown that initially the renatured DNA was rich in guanine-cytosine base pairs and non-random in base sequence, but that, as equilibrium was approached, the renatured DNA gradually resembled native DNA more closely. The rate constant for the renaturation of guanine-cytosine base pairs was slightly higher than for adenine-thymine base pairs.

  17. Large Scale Chemical Cross-linking Mass Spectrometry Perspectives

    PubMed Central

    Zybailov, Boris L.; Glazko, Galina V.; Jaiswal, Mihir; Raney, Kevin D.

    2014-01-01

    The spectacular heterogeneity of a complex protein mixture from biological samples becomes even more difficult to tackle when one’s attention is shifted towards different protein complex topologies, transient interactions, or localization of PPIs. Meticulous protein-by-protein affinity pull-downs and yeast-two-hybrid screens are the two approaches currently used to decipher proteome-wide interaction networks. Another method is to employ chemical cross-linking, which gives not only identities of interactors, but could also provide information on the sites of interactions and interaction interfaces. Despite significant advances in mass spectrometry instrumentation over the last decade, mapping Protein-Protein Interactions (PPIs) using chemical cross-linking remains time consuming and requires substantial expertise, even in the simplest of systems. While robust methodologies and software exist for the analysis of binary PPIs and also for the single protein structure refinement using cross-linking-derived constraints, undertaking a proteome-wide cross-linking study is highly complex. Difficulties include i) identifying cross-linkers of the right length and selectivity that could capture interactions of interest; ii) enrichment of the cross-linked species; iii) identification and validation of the cross-linked peptides and cross-linked sites. In this review we examine existing literature aimed at the large-scale protein cross-linking and discuss possible paths for improvement. We also discuss short-length cross-linkers of broad specificity such as formaldehyde and diazirine-based photo-cross-linkers. These cross-linkers could potentially capture many types of interactions, without strict requirement for a particular amino-acid to be present at a given protein-protein interface. How these shortlength, broad specificity cross-linkers be applied to proteome-wide studies? We will suggest specific advances in methodology, instrumentation and software that are needed to

  18. A novel water-based process produces eco-friendly bio-adhesive made from green cross-linked soybean soluble polysaccharide and soy protein.

    PubMed

    Yuan, Cheng; Chen, Mingsong; Luo, Jing; Li, Xiaona; Gao, Qiang; Li, Jianzhang

    2017-08-01

    In this study, an eco-friendly soy protein adhesive was developed that utilized two components from soybean meal without addition of any toxic material. A plant-based, water-soluble and inexpensive soybean soluble polysaccharide was used as the novel renewable material to combine with soy protein to produce a soy protein adhesive. Three-plywood was fabricated with the resulting adhesive, and its wet shear strength was measured. The results showed the wet shear strength of plywood bonded by the adhesive reached 0.99MPa, meeting the water resistance requirement for interior use panels. This improvement was attributed to the following reasons: (1) Combination of cross-linked soybean soluble polysaccharide and soy protein formed an interpenetrating network structure, improving the thermal stability and water resistance of the cured adhesive. (2) Adding CL-SSPS decreased the adhesive viscosity to 15.14Pas, which increased the amount of the adhesive that penetrate the wood's surface and formed more interlocks. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Synthesis and characterization of biodegradable polyurethane films based on HDI with hydrolyzable crosslinked bonds and a homogeneous structure for biomedical applications.

    PubMed

    Barrioni, Breno Rocha; de Carvalho, Sandhra Maria; Oréfice, Rodrigo Lambert; de Oliveira, Agda Aline Rocha; Pereira, Marivalda de Magalhães

    2015-01-01

    Synthetic biodegradable polymers are considered strategic in the biomaterials field and are used in various applications. Among the polymers used as biomaterials, polyurethanes (PUs) feature prominently due to their versatility and the ability to obtain products with a wide range of physical and mechanical properties. In this work, new biodegradable polyurethane films were developed based on hexamethylene diisocyanate (HDI) and glycerol as the hard segment (HS), and poly(caprolactone) triol (PCL triol) and low-molecular-weight poly(ethylene glycol) PEG as the soft segment (SS) without the use of a catalyst. The films obtained were characterized by structural, mechanical and biological testing. A highly connected network with a homogeneous PU structure was obtained due to crosslinked bonds. The films showed amorphous structures, high water uptake, hydrogel behavior, and susceptibility to hydrolytic degradation. Mechanical tests indicated that the films reached a high deformation at break of up to 425.4%, an elastic modulus of 1.6 MPa and a tensile strength of 3.6 MPa. The materials presented a moderate toxic effect on MTT assay and can be considered potential materials for biomedical applications.

  20. Influence of thermal post-curing on the degradation of a cross-linked polybenzimidazole-based membrane for high temperature polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ossiander, T.; Perchthaler, M.; Heinzl, C.; Scheu, C.

    2014-12-01

    The lifetime stability of membranes is one of the main requirements regarding reliability of high temperature polymer electrolyte membrane fuel cells. The present work has improved durability under cycled operation by thermal post-curing of cross-linked polybenzimidazole (PBI)-based membranes. The membranes were dried over 1, 2 and 3 h at 250 °C under air. Ex-situ experiments proved an increase in stability by post-curing. The liquid uptake and swelling in phosphoric acid increased with longer curing periods. The effect of thermal treatments on cycle stability, lifetime and begin-of-life performance of the membrane electrode assemblies (MEAs) was investigated. Longer post-curing periods of the membranes had no influence on the MEAs' begin-of-life performance and constant current behavior over 2300 h. However, the 3 h post-cured MEAs showed enhanced cycle stability. Post-mortem analysis was carried out to identify the occurring degradation mechanisms. While a significant loss of phosphoric acid and a reduction of electrochemical surface activity on the cathode were observed for both post-cured MEAs, the 3 h dried membrane sample had a significantly higher resistance against pinhole formation during the long term test. Altogether, this work presents thermal post-curing as a promising method for the reduction of degradation determining effects in fuel cell membranes.

  1. Adsorption of Hg2+, Cu2+ and Zn2+ ions from aqueous solution using formaldehyde cross-linked modified chitosan-thioglyceraldehyde Schiff's base.

    PubMed

    Monier, M

    2012-04-01

    A chitosan-thioglyceraldehyde Schiff's base cross-linked magnetic resin (CSTG) was prepared and characterized using various instrumental methods. Then, the prepared resin was used for comparative studies on the removal of toxic metal ions like: Hg(2+), Cu(2+) and Zn(2+) from aqueous solutions. The effects of the initial pH value of the solution, contact time, the initial metal ion concentration and temperature on the adsorption capacity of the composite were investigated. The kinetics data were analyzed by pseudo-first order and pseudo-second order equations. The adsorption kinetics was well described by the pseudo-second order equation, and the adsorption isotherms were better fitted by the Langmuir equation. The maximum theoretical adsorption capacities of the CSTG resin for Hg(2+), Cu(2+) and Zn(2+) were found to be 98±2, 76±1 and 52±1 mg g(-1), respectively. The negative values of Gibbs free energy of adsorption (ΔG(ads°) indicated the spontaneity of the adsorption of all metal ions on the novel resin.

  2. Effect of Cross-linking Density on Creep and Recovery Behavior in Epoxy-Based Shape Memory Polymers (SMEPs) for Structural Applications

    NASA Astrophysics Data System (ADS)

    Rao, Kavitha V.; Ananthapadmanabha, G. S.; Dayananda, G. N.

    2016-12-01

    Epoxy-based shape memory polymers (SMEPs) are gaining importance in the area of aerospace structures due to their high strength and stiffness which is a primary requirement for an SMEP in structural applications. The understanding of viscoelastic behavior of SMEPs is very essential to assess their shape memory effect. In the present work, three types of SMEPs with varying cross-linking densities were developed by curing an aromatic epoxy resin with aliphatic amines. Glass transition temperature ( T g) was measured for these SMEPs using advanced rheometric expansion system, and from the T g measurements, a range of temperatures from glassy to rubbery regimes were chosen. At selected temperatures, creep-recovery tests were performed in order to evaluate the viscoelastic behavior of SMEPs and also to investigate the effect of temperature on creep-recovery. Further, a three-parameter viscoelastic model (Zener) was used to fit the data obtained from experiments. Model parameters like moduli of the springs and viscosity of the dashpot were evaluated by curve fitting. Results revealed that Zener model was well suited to describe the viscoelastic behavior of SMEPs as a function of test temperatures.

  3. A novel amperometric biosensor based on a co-crosslinked L-lysine-α-oxidase/overoxidized polypyrrole bilayer for the highly selective determination of L-lysine.

    PubMed

    Guerrieri, Antonio; Ciriello, Rosanna; Cataldi, Tommaso R I

    2013-09-17

    An amperometric biosensor for the determination of L-lysine based on L-lysine-α-oxidase immobilized by co-crosslinking on a platinum electrode previously modified by an overoxidized polypyrrole film is described. The optimization of experimental parameters, such as pH and flow rate, permitted to minimize significantly substrate interferences even using a low specific, commercial enzyme. The relevant biases introduced in the measurement of lysine were just about 1% for L-arginine, L-histidine and L-ornithine, roughly 4% for L-phenylalanine and L-tyrosine. The developed approach allowed linear lysine responses from 0.02 mM up to 2 mM with a sensitivity of 41 nA/(mM × mm(2)) and a detection limit of 4 μM (S/N=3). No appreciable loss in lysine sensitivity was observed up to about 40 days. Allowing polypyrrole layer to remove interference from electroactive compounds, the present method revealed suitable to detect L-lysine in a pharmaceutical and cheese sample, showing a good agreement with the expected values. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Tear Film Stability in Sjögren Syndrome Patients Treated with Hyaluronic Acid Versus Crosslinked Hyaluronic Acid-Based Eye Drops.

    PubMed

    Cagini, Carlo; Torroni, Giovanni; Fiore, Tito; Cerquaglia, Alessio; Lupidi, Marco; Aragona, Pasquale; Iaccheri, Barbara

    2017-09-01

    To compare the stability of the tear film after instillation of eye drops containing hyaluronic acid (HA) or crosslinked hyaluronic acid (CLHA)-based in patients with Sjögren syndrome-related dry eye (SSDE). Forty subjects were included in this study and were divided into 2 groups: the first group (control group) consisted of 20 healthy volunteers; the second group (study group) constituted of 20 suffering from SSDE; before and 5, 30, and 60 min after instillation of eye drops the surface regularity index (SRI) and surface asymmetry index (SAI) were registered. Comparing HA and CLHA, in the control group, SAI show statistically significant difference in the time 0 and in time 5, whereas there is no a statistically significant difference after 30 and 60 min from instillation. For SRI there is no statistically significant difference at any time. In SSDE group there is no statistically significant difference in the time 0 and 5, whereas there is a statistically significant difference after 60 min for SAI, and after 30 and 60 min for SRI from instillation. Both SRI and SAI in dry eyes were significantly greater than in control eyes (P < 0.05). Our study showed a better efficacy of CLHA compared with HA in maintaining the stability of the tear film in a patient suffering from SSDE.

  5. Two-step sequential cross-linking of sugar beet pectin for transforming zein nanoparticle-based Pickering emulsions to emulgels.

    PubMed

    Soltani, Sahar; Madadlou, Ashkan

    2016-01-20

    Nanosized (<100 nm) zein spheres were employed for fabrication of a series of fish O/W Pickering emulsions. Although surface tension measurement informed the high potency of zein particles for interfacial adsorption, the prepared emulsions destabilized shortly. Electrostatic deposition of sugar beet pectin onto zein particles interfacial layer at pH 4.0 increased significantly the emulsion stability which was attributed to enhanced steric and electrostatic repulsions based on ζ-potential measurements. Pectin enrichment also increased the viscosity of the continuous phase of emulsion. Injection of the oxidative enzyme laccase into the pectin-enriched emulsion to cross-link the feruloyl-bearing pectin molecules and the subsequent addition of CaCl2 to set ion-mediated cross-linkages between carboxyl groups of pectin chains transformed Pickering emulsions to emulgels. The higher the pectin content, the shorter was the gelation time of emulsions. The obtained emulgels were self-standing and became harder along with increasing pectin content.

  6. Crosslinking biopolymers for biomedical applications.

    PubMed

    Reddy, Narendra; Reddy, Roopa; Jiang, Qiuran

    2015-06-01

    Biomaterials made from proteins, polysaccharides, and synthetic biopolymers are preferred but lack the mechanical properties and stability in aqueous environments necessary for medical applications. Crosslinking improves the properties of the biomaterials, but most crosslinkers either cause undesirable changes to the functionality of the biopolymers or result in cytotoxicity. Glutaraldehyde, the most widely used crosslinking agent, is difficult to handle and contradictory views have been presented on the cytotoxicity of glutaraldehyde-crosslinked materials. Recently, poly(carboxylic acids) that can crosslink in both dry and wet conditions have been shown to provide the desired improvements in tensile properties, increase in stability under aqueous conditions, and also promote cell attachment and proliferation. Green chemicals and newer crosslinking approaches are necessary to obtain biopolymeric materials with properties desired for medical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Development of a Crosslink Channel Simulator

    NASA Technical Reports Server (NTRS)

    Hunt, Chris; Smith, Carl; Burns, Rich

    2004-01-01

    Distributed Spacecraft missions are an integral part of current and future plans for NASA and other space agencies. Many of these multi-vehicle missions involve utilizing the array of spacecraft as a single, instrument requiring communication via crosslinks to achieve mission goals. NASA s Goddard Space Flight Center (GSFC) is developing the Formation Flying Test Bed (FFTB) to provide a hardware-in-the-loop simulation environment to support mission concept development and system trades with a primary focus on Guidance, Navigation, and Control (GN&C) challenges associated with spacecraft flying. The goal of the FFTB is to reduce mission risk by assisting in mission planning and analysis, provide a technology development platform that allows algorithms to be developed for mission functions such as precision formation navigation and control and time synchronization. The FFTB will provide a medium in which the various crosslink transponders being used in multi-vehicle missions can be integrated for development and test; an integral part of the FFTB is the Crosslink Channel Simulator (CCS). The CCS is placed into the communications channel between the crosslinks under test, and is used to simulate on-mission effects to the communications channel such as vehicle maneuvers, relative vehicle motion, or antenna misalignment. The CCS is based on the Starlight software programmable platform developed at General Dynamics Decision Systems and provides the CCS with the ability to be modified on the fly to adapt to new crosslink formats or mission parameters. This paper briefly describes the Formation Flying Test Bed and its potential uses. It then provides details on the current and future development of the Crosslink Channel Simulator and its capabilities.

  8. Radiation Crosslinking of Polyurethane Enhanced by Introducing Terminal Double-Bonds

    NASA Astrophysics Data System (ADS)

    Zhou, Cheng-Fei; Liu, Yang; Jiu, Yong-Bin; Cao, Wei; Zhai, Tong; Wang, Lian-Cai

    2016-05-01

    In this article, the enhanced radiation crosslinking of polyurethane via double-bond capping method were discussed in detail. Meanwhile, the Enhanced radiation crosslinking of polyurethane based on polyimide as hard segment were emphasized. In addition, the preparation of radiation crosslinking foam by introducing terminal double-bond were introduced.

  9. Diaspirin cross-linked hemoglobin infusion did not influence base deficit and lactic acid levels in two clinical trials of traumatic hemorrhagic shock patient resuscitation.

    PubMed

    Sloan, Edward P; Koenigsberg, Max D; Philbin, Nora B; Gao, Weihua

    2010-05-01

    Diaspirin cross-linked hemoglobin (DCLHb) has demonstrated a pressor effect that could adversely affect traumatic hemorrhagic shock patients through diminished perfusion to vital organs, causing base deficit (BD) and lactate abnormalities. Data from two parallel, multicenter traumatic hemorrhagic shock clinical trials from 17 US Emergency Departments and 27 European Union prehospital services using DCLHb, a hemoglobin-based resuscitation fluid. In the 219 patients, the mean age was 37.3 years, 64% of the patients sustained a blunt injury, 48% received DCLHb resuscitation, and the overall 28-day mortality rate was 36.5%. BD data did not differ by treatment group (DCLHb vs. normal saline [NS]) at any time point. Study entry BD was higher in patients who died when compared with survivors in both studies (US: -14.7 vs. -9.3 and European Union: -11.1 vs. -4.1 mEq/L, p < 0.003) and at the first three time points after resuscitation. No differences in BD based on treatment group were observed in either those who survived or those who died from the hemorrhagic shock. US lactate data did not differ by treatment group (DCLHb vs. NS) at any time point. Study entry lactates were higher in US patients who ultimately died when compared with survivors (82.4 vs. 56.1 mmol/L, p < 0.003) and at all five postresuscitation time points. No lactate differences were observed between DCLHb and NS survivors or in those who died based on treatment group. Although patients who died had more greatly altered perfusion than those who survived, DCLHb treatment of traumatic hemorrhagic shock patients was not associated with BD or lactate abnormalities that would indicate poor perfusion.

  10. Performance enhancement of pentacene and F16CuPc-based low-voltage devices using cross-linked blend gate dielectrics

    NASA Astrophysics Data System (ADS)

    Shin, Eun-Sol; Oh, Jeong-Do; Kim, Dae-Kyu; Ha, Young-Geun; Choi, Jong-Ho

    2015-02-01

    Herein is reported the fabrication and systematic comparative analysis of low-voltage organic filed-effect transistors (OFETs) and inverters using bare ZrOx dielectrics and inorganic-organic hybrid CZB (cross-linked ZrOx/1,6-bis(trimethoxysily)hexane blend) dielectrics. Solution-processed sol-gel chemistry was employed to prepare the gate dielectrics. Two active layers of p-type pentacene and n-type copper hexadecafluorophthalocyanine (F16CuPc) were deposited on the dielectrics using the neutral cluster beam deposition method. Compared with bare ZrOx-based transistors and inverters, the CZB-based devices with low leakage current and high capacitance exhibited significantly higher hole and electron carrier mobilities of (0.12 → 1.03) and (1.3  ×  10-3 → 4.9  ×  10-3) cm2 (Vs)-1, respectively, and enhanced gains of (9.4 → 13.3), together with large output voltage swings and sharp inversions in the voltage transfer characteristics (VTCs). The CZB-based inverters also exhibited improved noise margins due to the higher gain and better symmetry of the VTCs compared with their bare ZrOx-based counterparts. The results indicate that on the basis of the enhanced electrical properties of CZB dielectrics and the growth of high-quality crystalline semiconducting films on CZB dielectric surfaces, such high-performance devices operating at low voltage levels are promising potential components for integrated circuits.

  11. Report of the blind trial of the Cetus Amplitype HLA DQ alpha forensic deoxyribonucleic acid (DNA) amplification and typing kit.

    PubMed

    Walsh, P S; Fildes, N; Louie, A S; Higuchi, R

    1991-09-01

    The AmpliType HLA DQ alpha forensic DNA amplification and typing kit is designed for the qualitative analysis of the human leukocyte antigen (HLA) DQ alpha alleles present in deoxyribonucleic acid (DNA) extracted from forensic samples. The AmpliType kit is the first forensic DNA typing product based on the GeneAmp polymerase chain reaction (PCR) process. The kit was evaluated by five forensic science laboratories (test sites) to assess their ability to perform DNA typing using PCR on sample types typically encountered by forensic laboratories. None of the DNA-containing samples was mistyped. Of the 180 DNA-containing samples analyzed, results were reported for 178 (98.9%). Of the 178 samples with results, all were correctly typed. Two sites did not report a result for one sample each. Four of the five laboratories experienced no significant levels of contamination in the DNA-containing samples. At the one site with the highest number of DNA-containing samples with contamination, the typing results were not compromised. This site was able to correct the contamination problem through simple procedural changes and stricter attention to sterile technique. Blank controls were important to monitor contamination. In conclusion, the trial demonstrated that forensic science laboratories are capable of setting up a PCR-based DNA typing laboratory and successfully using the AmpliType HLA DQ alpha forensic DNA amplification and typing kit to analyze forensic samples.

  12. Dual cross-linked organic-inorganic hybrid polymer electrolyte membranes based on quaternized poly(ether ether ketone) and (3-aminopropyl)triethoxysilane

    NASA Astrophysics Data System (ADS)

    Zhang, Na; Wang, Baolong; Zhao, Chengji; Zhang, Yurong; Bu, Fanzhe; Cui, Ying; Li, Xuefeng; Na, Hui

    2015-02-01

    Quaternized poly(ether ether ketone)s (QPEEKs) are synthesized to absorb phosphoric acid (PA) and used as high temperature proton exchange membranes (HTPEMs). In order to improve their oxidative and mechanical stability without sacrificing proton conductivities, a series of dual cross-linked organic-inorganic hybrid membranes are prepared using (3-aminopropyl)triethoxysilane (APTES) as a cross-linker. The amine of APTES reacts with two benzyl bromide groups to build the primary cross-linking network. The Si-O-Si network generated by the hydrolysis of triethoxysilane in APTES is the secondary cross-linking network. The dual cross-linking hybrid networks improve the mechanical and oxidative stability of PA doped membranes. They can endure up to 15.3 h in 3 wt.% H2O2, 4 ppm Fe2+ Fenton solution at 80 °C. During the hydrolysis of triethoxysilane, the release of small molecules (H2O and C2H5OH) forms many pores in surfaces and interior of membranes. These pores and the resulted Si-OH groups corporately enhance the PA absorbing ability and proton conductivity. The highest proton conductivity is 61.7 mS cm-1 for PA-QPEEK-10%APTES at 200 °C under anhydrous condition. These membranes show great potential to be used in HTPEM fuel cell.

  13. Fabrication of polytetrafluoroethylene/carbon fiber composites using radiation crosslinking

    NASA Astrophysics Data System (ADS)

    Oshima, Akihiro; Udagawa, Akira; Tanaka, Shigeru

    2001-07-01

    A fabrication method for fiber-reinforced plastic (FRP) composites based on carbon fibers and polytetrafluoroethylene (PTFE) which was crosslinked by electron beam (EB) irradiation under specific conditions was studied. Though the fabricated composite showed high mechanical properties compared with a ready-made PTFE composite (non-crosslinked PTFE with 5˜20 wt% filler), mechanical properties of laminated panels were a bit poor compared with those of usual FRP. It was found that the toughness of the PTFE matrix is poor in the composite. On the other hand, the one-ply sheet of carbon fibers and crosslinked PTFE composite showed good mechanical properties for sheet-shape materials. The wettability of the obtained crosslinked PTFE composite is hardly changed by crosslinking and reinforcement.

  14. Xwalk: computing and visualizing distances in cross-linking experiments.

    PubMed

    Kahraman, Abdullah; Malmström, Lars; Aebersold, Ruedi

    2011-08-01

    Chemical cross-linking of proteins or protein complexes and the mass spectrometry-based localization of the cross-linked amino acids in peptide sequences is a powerful method for generating distance restraints on the substrate's topology. Here, we introduce the algorithm Xwalk for predicting and validating these cross-links on existing protein structures. Xwalk calculates and displays non-linear distances between chemically cross-linked amino acids on protein surfaces, while mimicking the flexibility and non-linearity of cross-linker molecules. It returns a 'solvent accessible surface distance', which corresponds to the length of the shortest path between two amino acids, where the path leads through solvent occupied space without penetrating the protein surface. Xwalk is freely available as a web server or stand-alone JAVA application at http://www.xwalk.org.

  15. Conjugation of glucosamine with Gd3+-based nanoporous silica using a heterobifunctional ANB-NOS crosslinker for imaging of cancer cells

    PubMed Central

    Mehravi, Bita; Ahmadi, Mohsen; Amanlou, Massoud; Mostaar, Ahmad; Ardestani, Mehdi Shafiee; Ghalandarlaki, Negar

    2013-01-01

    Background The aim of this study was to synthesize Gd3+-based silica nanoparticles that conjugate easily with glucosamine and to investigate their use as a nanoprobe for detection of human fibrosarcoma cells. Methods Based on the structure of the 2-fluoro-2-deoxy-D-glucose molecule (18FDG), a new compound consisting of D-glucose (1.1 nm) was conjugated with a Gd3+-based mesoporous silica nanoparticle using an N-5-azido-2-nitrobenzoyloxy succinimide (ANB-NOS) crosslinker The contrast agent obtained was characterized using a variety of methods, including Fourier transform infrared spectroscopy, nitrogen physisorption, thermogravimetric analysis, scanning and transmission electron microscopy, and inductively coupled plasma atomic emission spectrometry (ICP-AES). In vitro studies included cell toxicity, apoptosis, tumor necrosis factor-alpha, and hexokinase assays, and in vivo tests consisted of evaluation of blood glucose levels using the contrast compound and tumor imaging. The cellular uptake study was validated using ICP-AES. Magnetic resonance relaxivity of the contrast agent was determined using a 1.5 Tesla scanner. Results ANB-NOS was found to be the preferred linker for attaching glucosamine onto the surface of the mesoporous silica nanospheres. The r1 relaxivity for the nanoparticles was 17.70 mM−1s−1 per Gd3+ ion, which is 4.4 times larger than that for Magnevist® (r1 approximately 4 mM−1s−1 per Gd3+ ion). The compound showed suitable cellular uptake (75.6% ± 2.01%) without any appreciable cytotoxicity. Conclusion Our results suggest that covalently attaching glucosamine molecules to mesoporous silica nanoparticles enables effective targeted delivery of a contrast agent. PMID:24101868

  16. Individual identification from semen by the deoxyribonucleic acid (DNA) fingerprint technique.

    PubMed

    Honma, M; Yoshii, T; Ishiyama, I; Mitani, K; Kominami, R; Muramatsu, M

    1989-01-01

    For individual identification from semen, the deoxyribonucleic acid (DNA) fingerprint technique was used. In a blind trial, we succeeded in determining the semen donors among several volunteers comparing the DNA fingerprints of the blood and semen samples, respectively. Thereafter, we examined semen in a condom left beside a naked female dead body. The DNA fingerprint of the semen was recognized to be identical to that of the blood from a suspected man arrested later. This is the first report that the DNA fingerprint technique was practically used in a criminal investigation in Japan.

  17. Inhibition of Deoxyribonucleic Acid Synthesis and Bud Formation by Nalidixic Acid in Hyphomicrobium neptunium

    PubMed Central

    Weiner, Ronald M.; Blackman, Marcia A.

    1973-01-01

    The relationship between chromosome replication and morphogenesis in the budding bacterium Hyphomicrobium neptunium has been investigated. Nalidixic acid was found to completely inhibit deoxyribonucleic acid synthesis, but not ribonucleic acid synthesis. The antibiotic was bacteriostatic to the organism for the initial 5 h of exposure; thereafter it was bacteriocidal. Observation of inhibited cultures revealed cells that had produced abnormally long stalks, but no buds. These results indicate that bud formation is coupled to chromosome replication in H. neptunium. They do not exclude the possibilities that cross wall formation and bud separation may also be coupled to chromosome replication. Images PMID:4127631

  18. Survival, Deoxyribonucleic Acid Breakdown, and Synthesis in Salmonella typhimurium as Compared with Escherichia coli B Strains

    PubMed Central

    Hudnik-Plevnik, Tamara A.; Djordjević, Nadežda

    1970-01-01

    Salmonella typhimurium LT-2 was compared with radioresistant (B/r) and radiosensitive (Bs−2) strains of Escherichia coli in respect to the survival, deoxyribonucleic acid (DNA) breakdown, and DNA synthesis after X irradiation. It is shown that S. typhimurium LT-2 is about four times more sensitive than E. coli B/r but less sensitive than Bs−2. The DNA breakdown is in S. typhimurium LT-2 lower than the postirradiation breakdown of DNA in both E. coli strains and DNA synthesis proceeds in this bacterium in spite of a much lower survival, as in the radioresistant E. coli B/r. PMID:4916313

  19. Tetracycline Inhibits Propagation of Deoxyribonucleic Acid Replication and Alters Membrane Properties

    PubMed Central

    Pato, Martin L.

    1977-01-01

    Tetracycline, at concentrations greater than required for inhibition of protein synthesis, rapidly and completely inhibits replication of deoxyribonucleic acid (DNA) in Escherichia coli and Bacillus subtilis. At these concentrations of tetracycline, synthesis of ribonucleic acid is not appreciably altered. In addition to inhibiting DNA replication, tetracycline causes alterations of the cytoplasmic membrane resulting in leakage of intracellular pools of nucleotides, amino acids, and the non-metabolizable sugar analogue, thiomethylgalactoside. As DNA is synthesized at a site on the membrane, alterations of membrane structure by tetracycline may be responsible for the observed inhibition of DNA replication. PMID:403855

  20. Photodynamic Action on Native and Denatured Transforming Deoxyribonucleic Acid from Haemophilus influenzae

    PubMed Central

    León, Manuel Ponce-De; Cabrera-Juárez, Emiliano

    1970-01-01

    The photodynamic inactivation of native or denatured transforming deoxyribonucleic acid (DNA) from Haemophilus influenzae is described. The inactivation at the same pH was higher for denatured than native DNA. At acidic pH, the inactivation both for native and denatured DNA was faster than at alkaline pH. The guanine content of photoinactivated native DNA at neutral pH was less than untreated DNA. The inactivation of biological activity was more extensive than the alteration of guanine. The absorption spectrum of photoinactivated native or denatured DNA was only slightly different than the control DNA at the different experimental conditions. PMID:5309576

  1. Mechanisms of Inhibition of Pyrimidine Dimer Formation in Deoxyribonucleic Acid by Acridine Dyes

    PubMed Central

    Sutherland, B. M.; Sutherland, J. C.

    1969-01-01

    The ultraviolet (UV)-induced formation of cyclobutyl pyrimidine dimers in Escherichia coli deoxyribonucleic acid (DNA) in vitro has been investigated in terms of the mechanism of inhibition by acridine dyes, the effect on dimer yield of specific singlet and triplet quenchers, and the mechanism of dimer formation. Our results indicate that (a) energy transfer is important in dimer reduction by acridines, (b) this transfer occurs from the singlet (S1) of DNA, and (c) at room temperature triplet quenchers do not reduce dimer yield in DNA. PMID:4888976

  2. Some Unique Properties of the Deoxyribonucleic Acid-Bearing Portion of the Bacterial Membrane

    PubMed Central

    Ballesta, J. P.; Cundliffe, E.; Daniels, M. J.; Silverstein, Judith L.; Susskind, Miriam M.; Schaechter, M.

    1972-01-01

    By using the M-band technique we have shown that portions of the membranes of Bacillus megaterium and Escherichia coli vary in their affinity for magnesium-Sarkosyl crystals and in phospholipid composition. The portion to which deoxyribonucleic acid is attached comprises as little as 4% of the total cell membrane, has a particularly high degree of affinity for magnesium-Sarkosyl crystals, and is rich in phosphatidylethanolamine. The M-band fractionation does not depend on the use of lysozyme. PMID:4627921

  3. Elastin-based biopolymers: chemical synthesis and structural characterization of linear and cross-linked poly(OrnGlyGlyOrnGly).

    PubMed

    Martino, M; Perri, T; Tamburro, A M

    2002-01-01

    Poly(OrnGlyGlyOrnGly) was synthesized by classical procedures in solution. The monomeric sequence -OrnGlyGlyOrnGly- was chosen as a modification of -ValGlyGlyValGly-, typical of elastin, to impart primary amine functionality, susceptible to cross-linking with appropriate bifunctional reagents. Herein we focus on the cross-linking of poly(OrnGlyGlyOrnGly) with glutaraldehyde. The polymers, both linear and cross-linked, were characterized and investigated for their molecular and supramolecular properties. Circular dichroism studies performed on linear poly(OrnGlyGlyOrnGly) revealed a variety of conformations similar to elastin. At a supramolecular level, different kinds of aggregates were found such as the elastin-like twisted-rope pattern of filaments and fibrils, together with other specific morphologies, similar to those recently identified in some elastin-mimetic polypeptides.

  4. Folic acid-targeted disulfide-based cross-linking micelle for enhanced drug encapsulation stability and site-specific drug delivery against tumors

    PubMed Central

    Zhang, Yumin; Zhou, Junhui; Yang, Cuihong; Wang, Weiwei; Chu, Liping; Huang, Fan; Liu, Qiang; Deng, Liandong; Kong, Deling; Liu, Jianfeng; Liu, Jinjian

    2016-01-01

    Although the shortcomings of small molecular antitumor drugs were efficiently improved by being entrapped into nanosized vehicles, premature drug release and insufficient tumor targeting demand innovative approaches that boost the stability and tumor responsiveness of drug-loaded nanocarriers. Here, we show the use of the core cross-linking method to generate a micelle with enhanced drug encapsulation ability and sensitivity of drug release in tumor. This kind of micelle could increase curcumin (Cur) delivery to HeLa cells in vitro and improve tumor accumulation in vivo. We designed and synthesized the core cross-linked micelle (CCM) with polyethylene glycol and folic acid-polyethylene glycol as the hydrophilic units, pyridyldisulfide as the cross-linkable and hydrophobic unit, and disulfide bond as the cross-linker. CCM showed spherical shape with a diameter of 91.2 nm by the characterization of dynamic light scattering and transmission electron microscope. Attributed to the core cross-linking, drug-loaded CCM displayed higher Nile Red or Cur-encapsulated stability and better sensitivity to glutathione than noncross-linked micelle (NCM). Cellular uptake and in vitro antitumor studies proved the enhanced endocytosis and better cytotoxicity of CCM-Cur against HeLa cells, which had a high level of glutathione. Meanwhile, the folate receptor-mediated drug delivery (FA-CCM-Cur) further enhanced the endocytosis and cytotoxicity. Ex vivo imaging studies showed that CCM-Cur and FA-CCM-Cur possessed higher tumor accumulation until 24 hours after injection. Concretely, FA-CCM-Cur exhibited the highest tumor accumulation with 1.7-fold of noncross-linked micelle Cur and 2.8-fold of free Cur. By combining cross-linking of the core with active tumor targeting of FA, we demonstrated a new and effective way to design nanocarriers for enhanced drug encapsulation, smart tumor responsiveness, and elevated tumor accumulation. PMID:27051287

  5. The effect of deoxyribonucleic acid extraction methods from lymphoid tissue on the purity, content, and amplifying ability

    PubMed Central

    Ayatollahi, Hossein; Sadeghian, Mohammad Hadi; Keramati, Mohammad Reza; Ayatollahi, Ali; Shajiei, Arezoo; Sheikhi, Maryam; Bakhshi, Samane

    2016-01-01

    Background: Nowadays, definitive diagnosis of numerous diseases is based on the genetic and molecular findings. Therefore, preparation of fundamental materials for these evaluations is necessary. Deoxyribonucleic acid (DNA) is the first material for the molecular pathology and genetic analysis, and better results need more pure DNA. Furthermore, higher concentration of achieved DNA causes better results and higher amplifying ability for subsequent steps. We aim to evaluate five DNA extraction methods to compare DNA intimacy including purity, concentration, and amplifying ability with each other. Materials and Methods: The lymphoid tissue DNA was extracted from formalin-fixed, paraffin embedded (FFPE) tissue through five different methods including phenol-chloroform as the reference method, DNA isolation kit (QIAamp DNA FFPE Tissue Kit, Qiagen, Germany), proteinase K and xylol extraction and heat alkaline plus mineral oil extraction as authorship innovative method. Finally, polymerase chain reaction (PCR) and real-time PCR method were assessed to compare each following method consider to DNA purity and its concentration. Results: Among five different applied methods, the highest mean of DNA purity was related to heat alkaline method. Moreover, the highest mean of DNA concentration was related to heat alkaline plus mineral oil. Furthermore, the best result in quantitative PCR was in proteinase K method that had the lowest cycle threshold averages among the other extraction methods. Conclusion: We concluded that our innovative method for DNA extraction (heat alkaline plus mineral oil) achieved high DNA purity and concentration. PMID:27630381

  6. DNA Photolithography with Cinnamate Crosslinkers

    NASA Technical Reports Server (NTRS)

    Feng, Lang (Inventor); Chaikin, Paul Michael (Inventor)

    2016-01-01

    The present invention relates generally to cinnamate crosslinkers. Specifically, the present invention relates to gels, biochips, and functionalized surfaces useful as probes, in assays, in gels, and for drug delivery, and methods of making the same using a newly-discovered crosslinking configuration.

  7. Laser welding and collagen crosslinks

    SciTech Connect

    Reiser, K.M.; Last, J.A.; Small, W. IV; Maitland, D.J.; Heredia, N.J.; Da Silva, L.B.; Matthews, D.L.

    1997-02-20

    Strength and stability of laser-welded tissue may be influenced, in part, by effects of laser exposure on collagen crosslinking. We therefore studied effects of diode laser exposure (805 nm, 1-8 watts, 30 seconds) + indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. Effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p<0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relations are maintained. We conclude that: (1)ICG alone induces DHLNL and OHP crosslink formation; (2)subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3)excessive diode laser exposure destroys normally occurring HLNL crosslinks.

  8. Laser welding and collagen crosslinks

    NASA Astrophysics Data System (ADS)

    Reiser, Karen M.; Small, Ward, IV; Maitland, Duncan J.; Heredia, Nicholas J.; Da Silva, Luiz B.; Matthews, Dennis L.; Last, Jerold A.

    1997-05-01

    The strength and stability of laser-welded tissue may be influenced, in part, by the effects of laser exposure on collagen crosslinking. We therefore studied the effects of diode laser exposure (805 nm, 1 - 8 watts, 30 seconds) plus indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. The effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p less than 0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relationships are maintained. We conclude that: (1) ICG alone induces DHLNL and OHP crosslink formation; (2) subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3) excessive diode laser exposure destroys normally occurring HLNL crosslinks.

  9. Absence of Circular Plasmid Deoxyribonucleic Acid Attributable to a Genetic Determinant for Methicillin Resistance in Staphylococcus aureus

    PubMed Central

    Stiffler, Paul W.; Sweeney, H. M.; Cohen, Sidney

    1973-01-01

    Plasmid deoxyribonucleic acid was not detected by centrifugal analysis of lysates of penicillinase-negative strains of Staphylococcus aureus harboring a determinant of methicillin resistance derived from strain Villaluz. When these strains contained a penicillinase plasmid, the plasmid deoxyribonucleic acid of methicillin-resistant and methicillin-susceptible strains was indistinguishable by the methods employed. The results indicate that the genetic determinant for methicillin resistance in the strains examined was not associated with a circular plasmid comparable to those that have been shown to determine resistance to benzylpenicillin, tetracycline, and chloramphenicol in S. aureus. PMID:4490525

  10. Further Evidence Concerning the Configuration of Transforming Deoxyribonucleic Acid During Entry into Bacillus subtilis1

    PubMed Central

    Strauss, Norman

    1966-01-01

    Strauss, Norman (State University of New York at Buffalo, Buffalo, N.Y.). Further evidence concerning the configuration of transforming deoxyribonucleic acid during entry into Bacillus subtilis. J. Bacteriol 91:702–708. 1966.—The appearance of linked, unselected traits with selected markers was followed as a function of time after the exposure of competent cells to transforming deoxyribonucleic acid (DNA). It was found that the per cent cotransfer of a linked, unselected trait with a single selected trait increased sharply soon after the lag period characterizing the appearance of the selected trait. Similar results were obtained when cotransfer of a linked unselected trait with a pair of selected traits was examined. The results are taken as an unequivocal demonstration that the entry of transforming DNA into competent Bacillus subtilis occurs in longitudinal fashion. The nature of the linkage between try2 and his9 was characterized. It was found that, although these two traits had been found to be unlinked on the basis of recombination tests, the saturation curves showed these two traits to be present on the same fragment of DNA. PMID:4956757

  11. PENICILLIN RESISTANCE OF COMPETENT CELLS IN DEOXYRIBONUCLEIC ACID TRANSFORMATION OF BACILLUS SUBTILIS.

    PubMed

    NESTER, E W

    1964-04-01

    Nester, E. W. (University of Washington, Seattle). Penicillin resistance of competent cells in deoxyribonucleic acid transformation of Bacillus subtilis. J. Bacteriol. 87:867-875. 1964.-Transformants are resistant to penicillin killing for several hours after deoxyribonucleic acid (DNA) addition. The present study indicates that this resistance is a consequence of such cells still remaining competent and is not the result of any interaction of donor DNA with the recipient cell. The following data support this conclusion: (i) the frequency of transformation can be increased five- to tenfold if penicillin acts on a competent culture prior to DNA addition; (ii) the percentage of competent cells in such a penicillin-treated culture calculated on the basis of a random coincidence of DNA molecules entering the same cell increases some 25-fold over that of a penicillin-nontreated population; (iii) the kinetics of penicillin killing of a recipient culture are identical whether or not transforming DNA has been added; (iv) the extent of killing by penicillin is related to the level of competence of the recipient culture; and (v) the kinetics of appearance and disappearance of competence in a population as well as in individual cells indicate that a cell may remain competent for 3 to 4 hr.

  12. “BLACK LIGHT” INACTIVATION OF TRANSFORMING DEOXYRIBONUCLEIC ACID FROM HAEMOPHILUS INFLUENZAE

    PubMed Central

    Cabrera-Juárez, Emiliano

    1964-01-01

    Cabrera-Juárez, Emiliano (Instituto Politecnico Nacional, Mexico, D.F., Mexico). “Black light” inactivation of transforming deoxyribonucleic acid from Haemophilus influenzae. J. Bacteriol. 87:771–778. 1964.—The biological activity (intrinsic genetic markers or nitrous acid mutable regions) of transforming deoxyribonucleic acid (DNA) from Haemophilus influenzae has been inactivated by “black light” (BL) by two mechanisms: (i) photodynamic action (oxygen-dependent) and (ii) “BL inactivation” (oxygen-independent). The BL inactivation is greater in denatured than in native DNA, and it is dependent on the pH. It does not depend on the temperature, and the damage produced is stable. The effective wavelength of inactivation is between 330 and 360 mμ. The BL inactivation is not reactivated by photoreactivating enzyme or nitrous acid. The BL and ultraviolet inactivations are additive, suggesting that the changes produced by BL and ultraviolet irradiation on transforming DNA are different. T2 phage was also inactivated by BL. The nature of the photochemical changes produced in DNA by BL is not known. PMID:14139527

  13. Alumina-clay nanoscale hybrid filler assembling in cross-linked polyethylene based nanocomposites: mechanics and thermal properties.

    PubMed

    Jose, Josmin P; Thomas, Sabu

    2014-07-28

    Herein, investigation on XLPE-Al2O3-clay ternary hybrid systems of Al2O3 and clay in 1 : 1 and 2 : 1 ratios, binary systems of XLPE-clay and XLPE-Al2O3 nanocomposites, with special reference to the hybrid filler effect and the superior microstructural development in ternary systems is conducted. The ternary hybrid composite of Al2O3 and clay in a 1 : 1 ratio exhibits the highest tensile strength (100% increase) and Young's modulus (208% increase), followed by the Al2O3 : clay = 2 : 1 system. The interaction between alumina and clay altered the composite morphology, filler dispersion and gave rise to a unique filler architecture leading to a substantial boost up in mechanics compared to predictions based on the idealized filler morphology. Experimentally observed much higher mechanics compared to theoretical predictions confirmed that the dramatic improvement in mechanics is the outcome of the positive hybrid effect and a second factor of synergism, i.e. filler-filler networks. Morphological control of the hybrid filler network is realized by adjusting the ratio between different fillers. For the Al2O3 : clay = 2 : 1 system, the microstructural limitation of dispersion due to the steric effect of alumina clusters shifts the properties to the negative hybrid effect region.

  14. Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements

    NASA Astrophysics Data System (ADS)

    Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

    2016-01-01

    Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively.

  15. Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements

    PubMed Central

    Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

    2016-01-01

    Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively. PMID:26817674

  16. Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements.

    PubMed

    Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

    2016-01-28

    Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively.

  17. A Study into the Collision-induced Dissociation (CID) Behavior of Cross-Linked Peptides.

    PubMed

    Giese, Sven H; Fischer, Lutz; Rappsilber, Juri

    2016-03-01

    Cross-linking/mass spectrometry resolves protein-protein interactions or protein folds by help of distance constraints. Cross-linkers with specific properties such as isotope-labeled or collision-induced dissociation (CID)-cleavable cross-linkers are in frequent use to simplify the identification of cross-linked peptides. Here, we analyzed the mass spectrometric behavior of 910 unique cross-linked peptides in high-resolution MS1 and MS2 from published data and validate the observation by a ninefold larger set from currently unpublished data to explore if detailed understanding of their fragmentation behavior would allow computational delivery of information that otherwise would be obtained via isotope labels or CID cleavage of cross-linkers. Isotope-labeled cross-linkers reveal cross-linked and linear fragments in fragmentation spectra. We show that fragment mass and charge alone provide this information, alleviating the need for isotope-labeling for this purpose. Isotope-labeled cross-linkers also indicate cross-linker-containing, albeit not specifically cross-linked, peptides in MS1. We observed that acquisition can be guided to better than twofold enrich cross-linked peptides with minimal losses based on peptide mass and charge alone. By help of CID-cleavable cross-linkers, individual spectra with only linear fragments can be recorded for each peptide in a cross-link. We show that cross-linked fragments of ordinary cross-linked peptides can be linearized computationally and that a simplified subspectrum can be extracted that is enriched in information on one of the two linked peptides. This allows identifying candidates for this peptide in a simplified database search as we propose in a search strategy here. We conclude that the specific behavior of cross-linked peptides in mass spectrometers can be exploited to relax the requirements on cross-linkers.

  18. Glucose biosensor based on the immobilization of glucose oxidase on electrochemically synthesized polypyrrole-poly(vinyl sulphonate) composite film by cross-linking with glutaraldehyde.

    PubMed

    Colak, Ozlem; Yaşar, Ahmet; Cete, Servet; Arslan, Fatma

    2012-10-01

    In this study, a novel amperometric glucose biosensor was developed by immobilizing glucose oxidase (GOX) by cross-linking via glutaraldehyde on electrochemically polymerized polypyrrole-poly(vinyl sulphonate) (PPy-PVS) films on the surface of a platinum (Pt) electrode. Electropolymerization of pyrrole and poly(vinyl sulphonate) on the Pt surface was carried out with an electrochemical cell containing pyrrole and poly(vinyl sulphonate) by cyclic voltammetry between -1.0 and + 2.0 V (vs.Ag/AgCl) at a scan rate of 50 mV/s upon the Pt electrode. The amperometric determination was based on the electrochemical detection of H(2)O(2) generated in enzymatic reaction of glucose. Determination of glucose was carried out by the oxidation of enzymatically produced H(2)O(2) at 0.4 V vs. Ag/AgCl. The effects of pH and temperature were investigated and optimum parameters were found to be 7.5 and 65°C, respectively. The effect of working potential was investigated and optimum potential was determined to be 0.4 V. The operational stability of the enzyme electrode was also studied. The response of the PPy/PVS-GOX glucose biosensor exhibited good reproducibility with a relative standard deviation (RSD) of 2.48%. The glucose biosensor retained 63% of initial activity after 93 days when stored in 0.1 M phosphate buffer solution of pH 7.5 at 4°C. With the low operating potential, the biosensor demonstrated little interference from the possible interferants.

  19. The effects of different cross-linking conditions on collagen-based nanocomposite scaffolds-an in vitro evaluation using mesenchymal stem cells.

    PubMed

    Suchý, Tomáš; Šupová, Monika; Sauerová, Pavla; Verdánová, Martina; Sucharda, Zbyněk; Rýglová, Šárka; Žaloudková, Margit; Sedláček, Radek; Kalbáčová, Marie Hubálek

    2015-11-20

    Nanocomposite scaffolds which aimed to imitate a bone extracellular matrix were prepared for bone surgery applications. The scaffolds consisted of polylactide electrospun nano/sub-micron fibres, a natural collagen matrix supplemented with sodium hyaluronate and natural calcium phosphate nano-particles (bioapatite). The mechanical properties of the scaffolds were improved by means of three different cross-linking agents: N-(3-dimethylamino propyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in an ethanol solution (EDC/NHS/EtOH), EDC/NHS in a phosphate buffer saline solution (EDC/NHS/PBS) and genipin. The effect of the various cross-linking conditions on the pore size, structure and mechanical properties of the scaffolds were subsequently studied. In addition, the mass loss, the swelling ratio and the pH of the scaffolds were determined following their immersion in a cell culture medium. Furthermore, the metabolic activity of human mesenchymal stem cells (hMSCs) cultivated in scaffold infusions for 2 and 7 days was assessed. Finally, studies were conducted of cell adhesion, proliferation and penetration into the scaffolds. With regard to the structural stability of the tested scaffolds, it was determined that EDC/NHS/PBS and genipin formed the most effectively cross-linked materials. Moreover, it was discovered that the genipin cross-linked scaffold also provided the best conditions for hMSC cultivation. In addition, the infusions from all the scaffolds were found to be non-cytotoxic. Thus, the genipin and EDC/NHS/PBS cross-linked scaffolds can be considered to be promising biomaterials for further in vivo testing and bone surgery applications.

  20. Intracellular Forms of Adenovirus Deoxyribonucleic Acid I. Evidence for a Deoxyribonucleic Acid-Protein Complex in Baby Hamster Kidney Cells Infected with Adenovirus Type 12

    PubMed Central

    Doerfler, Walter; Lundholm, Ulla; Hirsch-Kauffmann, Monica

    1972-01-01

    The total intracellular deoxyribonucleic acid (DNA) from baby hamster kidney cells abortively infected with 3H-adenovirus type 12 was analyzed in dye-buoyant density gradients. Between 10 and 20% of the cell-associated radioactivity derived from viral DNA bands in a density position which is 0.043 to 0.085 g/cm3 higher than that of viral DNA extracted from purified virions. The DNA in the high-density region (HP-fraction) is almost completely absent when DNA, ribonucleic acid (RNA) or protein synthesis is chemically inhibited in separate experiments. The HP-fraction is not found when the virus does not adsorb to and enter the cell. The DNA in the HP-fraction appears as early as 2 hr after inoculation. At 2 hr after infection, the HP-fraction is present both in the nucleus and the cytoplasm. This DNA hybridizes exclusively with viral DNA and sediments at approximately the same rate in both neutral and alkaline sucrose density gradients. Electron microscopy has revealed no circular DNA molecules in this fraction. Evidence indicates that the viral DNA in the HP-fraction exists in a complex with protein and possibly RNA. The protein component of the complex is resistant to enzymatic digestion, whereas the complex is susceptible to ribonuclease treatment. Digestion with deoxyribonuclease reduces the amount of DNA found in the HP-fraction. The structure and biological function of this complex are currently being investigated. PMID:5062681

  1. Influence of Bacteriophage PBS1 and φW-14 Deoxyribonucleic Acids on Homologous Deoxyribonucleic Acid Uptake and Transformation in Competent Bacillus subtilis

    PubMed Central

    López, Paloma; Espinosa, Manuel; Piechowska, Mirosława; Shugar, David

    1980-01-01

    Both bacteriophage PBS1 deoxyribonucleic acid (DNA) (in which all the thymine residues are replaced by uracil) and phage φW-14 DNA [in which half the thymine residues are replaced by 5-(aminobutylaminomethyl)uracil or 5-putrescinylthymine] exhibit comparable competing abilities for uptake of homologous DNA in a Bacillus subtilis competent system. But, whereas PBS1 DNA leads to a decrease in transformation frequencies compatible with its competing ability for DNA uptake, φW-14 DNA decreases transformation frequencies by a factor up to eightfold higher. The effect of φW-14 DNA on transformation frequencies is visible even at a concentration level that does not decrease transforming DNA uptake. No such effect was observed with heterologous DNA containing presumably ionically bound putrescine. Low concentrations of φW-14 DNA decreased the number of double (nonlinked) transformants more than single transformants. The influence on transformation was abolished when φW-14 DNA was added 20 min after addition of transforming DNA, i.e., when the recombination process was terminated. The putrescine-containing DNA also decreased retention of trichloroacetic acid-precipitable radioactivity of homologous DNA taken up. We conclude that φW-14 DNA inhibits some intracellular process(es) at the level of recombination. In addition, there is evidence that φW-14 DNA, but not heterologous DNA with ionically bound putrescine, binds also to site(s) on the cell surface other than receptors for homologous DNA. PMID:6772635

  2. Sterile Keratitis following Collagen Crosslinking.

    PubMed

    Javadi, Mohammad-Ali; Feizi, Sepehr

    2014-01-01

    To report a keratoconic eye that developed severe sterile keratitis and corneal scar after collagen crosslinking necessitating corneal transplantation. A 26-year-old man with progressive keratoconus underwent collagen crosslinking and presented with severe keratitis 72 hours after the procedure. The initial impression was infectious corneal ulcer and a fortified antibiotic regimen was administered. However, the clinical course and confocal microscopy results prompted a diagnosis of sterile keratitis. The eye developed severe corneal scars leading to reduced visual acuity and necessitating corneal transplantation. Sterile keratitis may develop after collagen crosslinking resulting in profound visual loss leading to corneal transplantation.

  3. Respiratory-deficient mutants of Torulopsis glabrata, a yeast with circular mitochondrial deoxyribonucleic acid of 6 mu m.

    PubMed Central

    O'Connor, R M; McArthur, C R; Clark-Walker, G D

    1976-01-01

    Purified mitochondria from the petite positive yeast Torulopsis glabrata contain a circular deoxyribonucleic acid (DNA) with a length of 6 mum and a buoyant density of 1.686 g/cm3. This DNA is absent from ethidium bromide induced respiratory-deficient mutants. Images PMID:944184

  4. Detection of deoxyribonucleic acid (DNA) targets using polymerase chain reaction (PCR) and paper surface-enhanced Raman spectroscopy (SERS) chromatography.

    PubMed

    Hoppmann, Eric P; Yu, Wei W; White, Ian M

    2014-01-01

    Surface-enhanced Raman spectroscopy (SERS) enables multiplex detection of analytes using simple, portable equipment consisting of a single excitation source and detector. Thus, in theory, SERS is ideally suited to replace fluorescence in assays that screen for numerous deoxyribonucleic acid (DNA) targets, but in practice, SERS-based assays have suffered from complexity and elaborate processing steps. Here, we report an assay in which a simple inkjet-fabricated plasmonic paper device enables SERS-based detection of multiple DNA targets within a single polymerase chain reaction (PCR). In prior work, we demonstrated the principles of chromatographic separation and SERS-based detection on inkjet-fabricated plasmonic paper. The present work extends that capability for post-PCR gene sequence detection. In this design, hydrolysis DNA probes with 5' Raman labels are utilized; if the target is present, the probe is hydrolyzed during PCR, freeing the reporter. After applying the PCR sample to a paper SERS device, an on-device chromatographic separation and concentration is conducted to discriminate between hydrolyzed and intact probes. SERS is then used to detect the reporter released by the hydrolyzed probes. This simple separation and detection on paper eliminates the need for complex sample processing steps. In this work, we simultaneously detect the methicillin-resistant Staphylococcus aureus genes mecA and femB to illustrate the concept. We envision that this approach could contribute to the development of multiplex DNA diagnostic tests enabling screening for several target sequences within a single reaction, which is necessary for cases in which sample volume and resources are limited.

  5. Photoreactivities and thermal properties of psoralen cross-links

    SciTech Connect

    Yeung, A.T.; Jones, B.K.; Chu, C.T.

    1988-05-03

    The authors have studied the photoreaction of 8-methoxypsoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP), and 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) with a pair of 18-base-long oligonucleotides in which a 14-base region is complementary. Only one 5'TpA site, favored for both monoadduct and cross-link formation with psoralen, is present in this oligonucleotide pair. They have used this model system to demonstrate, for the first time, strand specificity in the photoreaction of psoralen with DNA. They found that the two types of cross-links which form at this site have large differences in thermal stabilities. In addition, the denaturation of each cross-links isomer duplex occurred in at least three stages, which can be visualized as three bands in thermal equilibrium under the conditions of a denaturing polyacrylamide gel. This novel observation suggests that there are several domains differing in thermal stability in a psoralen cross-link.

  6. Carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing.

    PubMed

    Zhang, Di; Zhou, Wei; Wei, Bing; Wang, Xin; Tang, Rupei; Nie, Jiemin; Wang, Jun

    2015-07-10

    The objective of this study was to develop a novel carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing. To prepare the crosslinked hydrogels, poly(vinyl alcohol) (PVA) was grafted with succinate acid to yield carboxyl-modified poly(vinyl alcohol) (PVA-COOH). Hydrogel films based on PVA-COOH and chitosan (CS) at different concentrations were crosslinked through the formation of amide linkages. The mechanical properties of these crosslinked hydrogel films in dry and swollen state were greatly improved with high swelling ratio. Water vapor and oxygen permeability evaluations indicated that crosslinked hydrogel films could maintain a moist environment over wound bed. Biocompatibility test showed the crosslinked hydrogels had no cytotoxicity and hemolytic potential. Gentamicin sulfate-loaded crosslinked hydrogel films showed sustained drug release profile, and could effectively suppress bacterial proliferation and protect wound from infection.

  7. New Cross-Linkable Polyimides

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.; Havens, Stephen J.

    1992-01-01

    Methyl groups cross-link in air at 275 degrees C or upon ultraviolet irradiation to form insoluble polyimides. New materials particularly useful in electronics and microelectronics. Also useful as films, adhesives, and composite matrices.

  8. Graft-crosslinked copolymers based on poly(arylene ether ketone)-gc-sulfonated poly(arylene ether sulfone) for PEMFC applications.

    PubMed

    Zhang, Xuan; Hu, Zhaoxia; Luo, Linqiang; Chen, Shanshan; Liu, Jianmei; Chen, Shouwen; Wang, Lianjun

    2011-07-15

    Novel poly(arylene ether ketone) polymers with fluorophenyl pendants and phenoxide-terminated wholly sulfonated poly(arylene ether sulfone) oligomers are prepared via Ni(0)-catalyzed and nucleophilic polymerization, respectively, and subsequently used as starting materials to obtain graft-crosslinked membranes as polymer electrolyte membranes. The phenoxide-terminated sulfonated moieties are introduced as hydrophilic parts as well as crosslinking units. The chemical structure and morphology of the obtained membranes are confirmed by (1) H NMR and tapping-mode AFM. The properties required for fuel cell applications, including water uptake and dimensional change, as well as proton conductivity, are investigated. AFM results show a clear nanoscale phase-separation microstructure of the obtained membranes. The membranes show good dimensional stability and reasonably high proton conductivities under 30-90% relative humidity. The anisotropic proton conductivity ratios (σ(formula see text) ) of the membranes in water are in the range 0.65-0.92, and increase with an increase in hydrophilic block length. The results indicate that the graft-crosslinked membranes are promising candidates for applications as polymer electrolyte membranes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Thermo- and pH-sensitive ionic-crosslinked hollow spheres from chitosan-based graft copolymer for 5-fluorouracil release.

    PubMed

    Li, Guiying; Guo, Lei; Wen, Quanwu; Zhang, Ting

    2013-04-01

    Thermo- and pH-sensitive ionic-crosslinked hollow spheres from self-assembly of chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAM) for controlled release of 5-fluorouracil were studied. CS-g-PNIPAM aggregated into core-shell micelles with collapsed PNIPAM as the core and CS as the shell at the temperature above LCST. Ionic crosslinking reagent sodium tripolyphosphate (TPP) was used to crosslink the shell to form hollow spheres after cooling to room temperature. The size of hollow spheres was manipulated by changing pH or temperature of the environment. The CS-g-PNIPAM hollow spheres with plenty of inner cavities showed high loading capacity for 5-fluorouracil due to the polymer-drug interactions. Release of 5-fluorouracil from nanoparticles was accelerated at the temperature above LCST ascribed to the destruction of polymer-drug interactions and the decrease of particles size. Changing pH or ionic strength deformed the structure hollow spheres, which led to the increase of drug release. These hollow nanoparticles with environmentally sensitive properties are expected to be utilized in the field of intelligent drug delivery. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Collagen based film with well epithelial and stromal regeneration as corneal repair materials: Improving mechanical property by crosslinking with citric acid.

    PubMed

    Zhao, Xuan; Liu, Yang; Li, Weichang; Long, Kai; Wang, Lin; Liu, Sa; Wang, Yingjun; Ren, Li

    2015-10-01

    Corneal disease can lead to vision loss. It has become the second greatest cause of blindness in the world, and keratoplasty is considered as an effective treatment method. This paper presents the crosslinked collagen (Col)-citric acid (CA) films developed by making use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The results showed that the Col-CA films had necessary optical performance, water content. The collagenase resistance of CA crosslinked films was superior to that of EDC crosslinked films. And CA5 film (Col:CA:EDC:NHS=60:3:10:10) had the best mechanical properties. Cell experiments showed that CA5 film was non-cytotoxic and human corneal epithelial cells could proliferate well on the films. Lamellar keratoplasty showed that the CA5 film could be sutured in the rabbit eyes and was epithelialized completely in about 10 days, and the transparency was restored quickly in 30±5 days. No inflammation and corneal neovascularization were observed at 6 months. Corneal stroma had been repaired; stromal cells and neo-stroma could be seen in the area of operation from the hematoxylin-eosin stained histologic sections and anterior segment optical coherence tomography images. These results indicated that Col-CA films were highly promising biomaterials that could be used in corneal tissue engineering and a variety of other tissue engineering applications.

  11. Protein Synthesis and Deoxyribonucleic Acid-Membrane Attachment During Thymineless Death in Escherichia coli

    PubMed Central

    Dankberg, Frances; Cummings, Donald J.

    1973-01-01

    The proteins synthesized during thymineless death in Escherichia coli B and B/r were analyzed by polyacrylamide gel elctrophoresis. It was found that the amount of a protein of molecular weight 80,000 to 88,000 is greatly increased during thymineless death compared to the amounts of other cell proteins. A technique for the isolation of cell membrane-deoxyribonucleic acid (DNA)-nascent ribonucleic acid (RNA) complex on detergent crystals was used to determine whether DNA might be detached from the cell membrane as a result of thymineless death. It was found that under no conditions of thymineless death or immunity to thymineless death was there any change in the attachment of DNA or pulse-labeled RNA to cell membrane. Images PMID:4570604

  12. Role of polyadenylic acid in a deoxyribonucleic acid-membrane fraction extracted from pneumococci.

    PubMed Central

    Firshein, W; Meyer, B; Epner, E; Viggiani, J

    1976-01-01

    After the addition of radioactive polyadenylic acid to cell suspensions of pneumocci, part of the radioactivity becomes associated with a deoxyribonucleic acid (DNA)-membrane fraction extracted from the cells. A variety of techniques show that a portion of this associated radioactivity may represent oligoadenylates complexed to DNA, probaby as part of a ribonucleic acid (RNA) component. Polyadenylic acid, which had previously been shown to enhance DNA synthesis in cell suspensions (Firshein and Benson, 1968), also enhances the extent of DNA synthesis by the DNA-membrane fraction in vitro under specific conditions of concentration and conformation. The mechanism of action of this enhancement may be related to the ability of oligoadenylates to increase the number of initiation sites for DNA replication by stimulating the production of an RNA primer, thus providing additional 3'-OH groups with which DNA polymerase can react. PMID:6428

  13. Fluorescence, spectroscopic and NLO properties of green tea extract in deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Manea, Ana-Maria; Rau, Ileana; Kajzar, Francois; Meghea, Aurelia

    2013-11-01

    Natural, purely biological deoxyribonucleic acid (DNA)-green tea extract (GTE) complexes at different concentrations were prepared and characterized for their spectroscopic, fluorescent, linear and nonlinear optical properties. The complexes can be processed into good optical quality thin films by solution casting. They fluoresce when excited in UV absorption band, with a significantly larger quantum yield for the DNA-GTE complex than for a pure GTE solution. The thin film refractive indices were determined by Fabry-Perot (FP) interference patterns. The third-order nonlinear optical (NLO) properties of thin films were determined by the optical third-harmonic generation technique at 1064.2 nm fundamental wavelength. The phase of THG susceptibility was determined from the concentration variation of THG susceptibility. It reveals presence of a two-photon resonance with a band lying in the optical gap.

  14. New Deoxyribonucleic Acid Polymerase Induced by Bacillus subtilis Bacteriophage PBS2

    PubMed Central

    Price, Alan R.; Cook, Sandra J.

    1972-01-01

    The deoxyribonucleic acid (DNA) of Bacillus subtilis phage PBS2 has been confirmed to contain uracil instead of thymine. PBS2 phage infection of wild-type cells or DNA polymerase-deficient cells results in an increase in the specific activity of DNA polymerase. This induction of DNA polymerase activity is prevented by actinomycin D and chloramphenicol. In contrast to the major B. subtilis DNA polymerase, which prefers deoxythymidine triphosphate (dTTP) to deoxyuridine triphosphate (dUTP), the DNA polymerase in crude extracts of PBS2-infected cells is equally active whether dTTP or dUTP is employed. This phage-induced polymerase may be responsible for the synthesis of uracil-containing DNA during PBS2 phage infection. PMID:4623224

  15. Features of the damage produced by proflavine on transforming deoxyribonucleic acid.

    PubMed

    Cabrera-Juárez, E; Sánchez-Rincón, D A

    1979-03-01

    Proflavine formed a complex with transforming deoxyribonucleic acid (DNA) from Haemophilus influenzae, with optimal formation at a ratio of proflavine to DNA of 0.06. The rate of dissociation of the complex by dialysis increased in the order: native, denatured, renatured DNA. The transforming activity of the DNA was reduced by its interaction with proflavine. This inactivation was dependent on the physical state of the DNA, the proflavine concentration, and the temperature. DNA that had been denatured and renatured was most sensitive; native DNA was much less sensitive. The inactivation remained after dialysis and was stable to prolonged storage. It is concluded that the inactivation of transforming DNA by proflavine takes place by a mechanism different from that of DNA-proflavine complex formation.

  16. Capsid Size and Deoxyribonucleic Acid Length: the Petite Variant of Bacteriophage T4

    PubMed Central

    Eiserling, Frederick A.; Geiduschek, E. Peter; Epstein, Richard H.; Metter, E. Jeffrey

    1970-01-01

    A mutant which produces a small-headed (“petite”) variant of bacteriophage T4 is described. The mutation (E920g) maps in a new gene (66) between genes 23 and 24. Petite phage particles composed up to 70% of the phage yield. The petite phage was nonviable upon single infection but produced progeny when two or more infected a cell. Its genome was shortened by a random deletion of about 30%, and deoxyribonucleic acid (DNA) extracted from the particles was 0.68 the length of normal T4 DNA. The reduction in DNA length was accompanied by a proportional reduction in head volume. Double mutants between E920g and head-defective mutants in gene 21 produced unusually high frequencies of spherical capsidlike structures (τ-particles). Images PMID:4924630

  17. Anomalies in the Sedimentation of Deoxyribonucleic Acid from Haemophilus influenzae in Alkaline Sucrose Gradients

    PubMed Central

    Kantor, George J.

    1972-01-01

    Difficulties were experienced in obtaining reproducible results for the sedimentation in alkaline sucrose gradients of Haemophilus influenzae deoxyribonucleic acid (DNA). The technique of McGrath and Williams of lysing whole cells on top of an alkaline sucrose gradient was employed. The addition of 0.2% sodium lauryl sulfate to the 0.2 n NaOH lysing solution and reduction of the hemin concentration in the growth medium increased the reproducibility to 100% for log-phase cells handled in a manner mimicking the handling procedure used for irradiating cells with ultraviolet light. Distributions of DNA with number average molecular weights of 200 × 106 were routinely obtained by using these modifications. PMID:4539243

  18. Number of Deoxyribonucleic Acid Uptake Sites in Competent Cells of Bacillus subtilis

    PubMed Central

    Singh, R. N.

    1972-01-01

    Two direct methods are presented for estimating the average number of deoxyribonucleic acid (DNA) uptake sites in competent cells of Bacillus subtilis from measurement of 14C- or 3H-thymine-labeled DNA uptake by competent culture. Advantage is taken of two facts: (i) effective contact between competent cells and transforming DNA molecules is established within a short time after mixing them together, and (ii) DNA molecules enter the competent B. subtilis cells in a linear fashion at a finite speed. From the number of DNA molecules initially attached to competent cells by brief exposure to transforming DNA in the first method or from the rate of DNA uptake by competent culture in the second method, the average number of DNA uptake sites is calculated to be 20 to 53 per competent cell. PMID:4622899

  19. Radiation crosslinked plasticized PVC - pipes

    NASA Astrophysics Data System (ADS)

    Hell, Z.; Ravlić, M.; Bogdanović, Lj.; Maleš, J.; Dvornik, I.; Ranogajec, F.; Ranogajec, M.; Tudorić-Ghemo, J.

    The efficiency of polyfunctional monomers triallyl cyanurate, allyl methacrylate, diallyl phtalate, 2-ethyl-2(hydroxy-methyl)-propanediol-(1,3) trimethacrylate, divinyl benzene and ethylene glycol dimethacrylate in radiation crosslinking of PVC was investigated. Patterns of pipes were produced and irradiated with gamma rays. The resistance to internal pressure of crosslinked PVC pipes was measured at 80°C and compared with resistance of unirradiated PVC pipes.

  20. Subnucleosomes and their relationships to the arrangement of histone binding sites along nucleosome deoxyribonucleic acid

    SciTech Connect

    Nelson, D.A.; Mencke, A.J.; Chambers, S.A.; Oosterhof, D.K.; Rill, R.L.

    1982-01-01

    Micrococcal nuclease cleaves within nucleosomes at sites spaced about 10.4 base pairs (bp) apart. Cleavages at sites equivalent to 30-35 bp from the ends of 146-bp cores cause spontaneous loss of an H2a-H2b pair associated with 30-40 bp length DNA. Cleavages at certain other sites do not affect the nucleosome integrity unless a solvent perturbant such as urea is added. Chromatin moderately digested with micrococcal nuclease, when fractionated by sedimentation or electrophoresis in the presence of 3 M urea, yielded four previously unobserved subnucleosomes with the following histone/DNA compositions: (H3)/sub 2/(H4)/sub 2/(H2a)(H2b)/95-115 bp; (H3)(H4)/70-80 bp DNA; (H2a)(H2b)/50-60 bp DNA; and (H1)/60-70 bp DNA. All but the latter subnucleosome were also obtained upon DNase I digestion of purified nucleosome cores labeled on the 5' ends with /sup 32/P. Only subnucleosomes that retained H2a and H2b also retained labeled ends. These results show that H2a and H2b are paired on the terminal 30-40 bp of core DNA, as suggested from analyses of histone-DNA cross-link products by Mirzabekov and coworkers. Considerations of the orgins and compositions of subnucleosomes and of cross-linking data suggest an expanded model for the locations of histone binding sites along nucleosome core DNA. The principal features of this model are (i) strong electrostatic binding sites of H2a and H2b occur at positions approximately 20-30 bp from the core ends, (ii) strong electrostatic binding sites of H3 and H4 occur primarily on the central 40 bp of core DNA, (iii) strong nonelectrostatic, urea-sensitive binding sites of H3 and H4 occur at positions approximately 30-50 bp from the core ends, and (iv) urea-sensitive binding sites of H2a or H2b may occur on the terminal 10-20 bp of core DNA.

  1. Chemical Crosslinking: Role in Protein and Peptide Science.

    PubMed

    Arora, Bharti; Tandon, Rashmi; Attri, Pankaj; Bhatia, Rohit

    2017-01-01

    Chemical crosslinking refers to intermolecular or intramolecular joining of two or more molecules by a covalent bond. The reagents that are used for the purpose are referred to as 'crosslinking reagents' or 'crosslinkers'. Based on factors like reactivity and spacer length these are classified into different types, each having its own specific function and application. In recent times, chemical crosslinking has emerged as an efficient tool for the study of biomolecules like proteins. It finds its application in various studies including the attachment of proteins to a solid support for the study of membrane receptors, protein-protein complexes, protein-DNA complexes, and others. When coupled with techniques like mass spectroscopy, it has been used not only for the determination of three dimensional structures of proteins but also for the study of protein-protein interactions and determination of interesting sites. This combination of mass spectrometry techniques and bioinformatics, added yet another dimension to our present day understanding of protein chemistry. Thus, chemical crosslinking has multitude uses that it can be put to. We undertook a systematic search of bibliographic databases and search engine such as Google Scholar, Scifinder, Scopus, Mendeley etc for review of research literature. We excluded research paper which only reported synthesis of crosslinker molecules and did not involve any mass spectrometry studies. Sixty-four papers were included in the review. The majority of references were taken from last ten years as there has been an immense progress in this area in the recent years. Eleven classical papers in this field were included which talk about basic of this methodology. Thirty-two papers discussed about various types of organic groups used for designing chemical cross-linkers and various methodologies which were used to enhance the crosslinking efficiency. These papers also highlight various strategies used to enhance detection of cross-linked

  2. Deoxyribonucleic acid damage induced by doxorubicin in peripheral blood mononuclear cells: possible roles for the stress response and the deoxyribonucleic acid repair process

    PubMed Central

    Nadin, Silvina B.; Vargas-Roig, Laura M.; Cuello-Carrión, F. Darío; Ciocca, Daniel R.

    2003-01-01

    Doxorubicin is an antineoplastic drug widely used in cancer treatment. However, many tumors are intrinsically resistant to the drug or show drug resistance after an initial period of response. Among the different molecules implicated with doxorubicin resistance are the heat shock proteins (Hsps). At present we do not know with certainty the mechanism(s) involved in such resistance. In the present study, to advance our knowledge on the relationship between Hsps and drug resistance, we have used peripheral blood mononuclear cells obtained from healthy nonsmoker donors to evaluate the capacity of a preliminary heat shock to elicit the Hsp response and to establish the protection against the deoxyribonucleic acid (DNA) damage induced by doxorubicin. DNA damage and repair were determined using the alkaline comet assay. We also measured the expression of Hsp27, Hsp60, Hsp70, Hsp90, hMLH1, hMSH2, and proliferating cell nuclear antigen by immunocytochemistry. The damage induced by doxorubicin was more efficiently repaired when the cells were previously heat shocked followed by a resting period of 24 hours before drug exposure, as shown by (1) the increased number of undamaged cells (P < 0.05), (2) the increased DNA repair capacity (P < 0.05), and (3) the high expression of the mismatch repair (MMR) proteins hMLH1 and hMSH2 (P < 0.05). In addition, in the mentioned group of cells, we confirmed by Western blot high expression levels of Hsp27 and Hsp70. We also noted a nuclear translocation of Hsp27 and mainly of Hsp70. Furthermore, inducible Hsp70 was more expressed in the nucleus than Hsc70, showing a possible participation of Hsp70 in the DNA repair process mediated by the MMR system. PMID:15115288

  3. Formaldehyde cross-linking and structural proteomics: Bridging the gap.

    PubMed

    Srinivasa, Savita; Ding, Xuan; Kast, Juergen

    2015-11-01

    Proteins are dynamic entities constantly moving and altering their structures based on their functions and interactions inside and outside the cell. Formaldehyde cross-linking combined with mass spectrometry can accurately capture interactions of these rapidly changing biomolecules while maintaining their physiological surroundings. Even with its numerous established uses in biology and compatibility with mass spectrometry, formaldehyde has not yet been applied in structural proteomics. However, formaldehyde cross-linking is moving toward analyzing tertiary structure, which conventional cross-linkers have already accomplished. The purpose of this review is to describe the potential of formaldehyde cross-linking in structural proteomics by highlighting its applications, characteristics and current status in the field. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Self-Assembled and Cross-Linked Animal and Plant-Based Polysaccharides: Chitosan-Cellulose Composites and Their Anion Uptake Properties.

    PubMed

    Udoetok, Inimfon A; Wilson, Lee D; Headley, John V

    2016-12-07

    Self-assembled and cross-linked chitosan/cellulose glutaraldehyde composite materials (CGC) were prepared with enhanced surface area and variable morphology. FTIR, CHN, and (13)C solid state NMR studies provided support for the cross-linking reaction between the amine groups of chitosan and glutaraldehyde; whereas, XRD and TGA studies provided evidence of cellulose-chitosan interactions for the composites. SEM, equilibrium swelling, and nitrogen adsorption studies corroborate the enhanced surface area and variable morphology of the cross-linked biopolymers. Equilibrium sorption studies at alkaline conditions with phenolic dyes, along with single component and mixed naphthenates in aqueous solution revealed variable uptake properties with the composites. The Freundlich isotherm model revealed that the composite at the highest levels of cross-linker, CGC3, had the highest sorption affinity (KF; L mmol/g) for phenolphthalein (phth) followed by ortho-nitrophenyl acetic acid (ONPAA) and para-nitrophenol (PNP), as follows: Phth (5.03 × 10(-1)) > ONPAA (2.28 × 10(-1)) > PNP (8.49 × 10(-2)). The Sips isotherm model provided a good description of the sorption profile of single component and naphthenate mixtures. The monolayer uptake capacity (Qm; mg g(-1)) is given in parentheses: 2-hexyldecanoic acid (S1; 115 mg/g) > 2-naphthoxyacetic acid (S3; 40.5 mg/g) > trans-4-pentylcyclohexylcarboxylic acid (S2; 13.7 mg/g). By comparison, the Qm values for CGC3 with naphthenate mixtures (24.1 and 27.4 mg/g) according to UV spectroscopy and electrospray ionization mass spectrometry (ESI-HRMS). The sorbent materials generally show greater uptake with naphthenates that possess lower vs higher double bond equivalence (DBE) values. Kinetic studies revealed that the sorption of phth adopted behavior described by the pseudo-second order model, while uptake for S3 and naphthenate mixtures adopted pseudo-first order behavior. This study contributes to a greater understanding of the

  5. The effect of cross-linking yield of PVK on the vibrational and emissive properties of new copolymer based on vinylcarbazole and phenylene-vinylene units

    NASA Astrophysics Data System (ADS)

    Mbarek, M.; Abbassi, F.; Alimi, K.

    2016-09-01

    The Phenylene-Vinylene (PV) unit's was successfully incorporated in the Vinylarbazole (VC) skeleton using the oxidative way via an anhydrous FeCl3. Dramatic changes in the vibrational and emissive properties are founded by varying the FeCl3 amount in the synthesis way due to the cross-linking of PVK units. SEM analysis showing a modified morphology structures of three compounds. However the percentage of the oxidant account induces the modulation of copolymer properties particularly theirs emissive proprieties. A red shifting of the maximum of photoluminescence, a quenching of luminescence and a fast decay time was observed with increasing of the oxidation yields.

  6. Crosslinking of agarose bioplastic using citric acid.

    PubMed

    Awadhiya, Ankur; Kumar, David; Verma, Vivek

    2016-10-20

    We report chemical crosslinking of agarose bioplastic using citric acid. Crosslinking was confirmed using Fourier transform infrared (FTIR) spectroscopy. The effects of crosslinking on the tensile strength, swelling, thermal stability, and degradability of the bioplastic were studied in detail. The tensile strength of the bioplastic films increased from 25.1MPa for control films up to a maximum of 52.7MPa for citric acid crosslinked films. At 37°C, the amount of water absorbed by crosslinked agarose bioplastic was only 11.5% of the amount absorbed by non-crosslinked controls. Thermogravimetric results showed that the crosslinked samples retain greater mass at high temperature (>450°C) than control samples. Moreover, while the crosslinked films were completely degradable, the rate of degradation was lower compared to non-crosslinked controls.

  7. Intra-spike crosslinking overcomes antibody evasion by HIV-1

    PubMed Central

    Galimidi, Rachel P.; Klein, Joshua S.; Politzer, Maria S.; Bai, Shiyu; Seaman, Michael S.; Nussenzweig, Michel C.; West, Anthony P.; Bjorkman, Pamela J.

    2015-01-01

    SUMMARY Antibodies developed during HIV-1 infection lose efficacy as the viral spike mutates. We postulated that anti-HIV-1 antibodies primarily bind monovalently because HIV’s low spike density impedes bivalent binding through inter-spike crosslinking, and the spike structure prohibits bivalent binding through intra-spike crosslinking. Monovalent binding reduces avidity and potency, thus expanding the range of mutations permitting antibody evasion. To test this idea, we engineered antibody-based molecules capable of bivalent binding through intra-spike crosslinking. We used DNA as a “molecular ruler” to measure intra-epitope distances on virion-bound spikes and construct intra-spike crosslinking molecules. Optimal bivalent reagents exhibited up to 2.5 orders-of-magnitude increased potency (>100-fold average increases across virus panels) and identified conformational states of virion-bound spikes. The demonstration that intra-spike crosslinking lowers the concentration of antibodies required for neutralization supports the hypothesis that low spike densities facilitate antibody evasion and the use of molecules capable of intra-spike crosslinking for therapy or passive protection. PMID:25635457

  8. Inverted bulk-heterojunction solar cell with cross-linked hole-blocking layer

    PubMed Central

    Udum, Yasemin; Denk, Patrick; Adam, Getachew; Apaydin, Dogukan H.; Nevosad, Andreas; Teichert, Christian; S. White, Matthew.; S. Sariciftci, Niyazi.; Scharber, Markus C.

    2014-01-01

    We have developed a hole-blocking layer for bulk-heterojunction solar cells based on cross-linked polyethylenimine (PEI). We tested five different ether-based cross-linkers and found that all of them give comparable solar cell efficiencies. The initial idea that a cross-linked layer is more solvent resistant compared to a pristine PEI layer could not be confirmed. With and without cross-linking, the PEI layer sticks very well to the surface of the indium–tin–oxide electrode and cannot be removed by solvents used to process PEI or common organic semiconductors. The cross-linked PEI hole-blocking layer functions for multiple donor–acceptor blends. We found that using cross-linkers improves the reproducibility of the device fabrication process. PMID:24817837

  9. Flanking sequences modulate diepoxide and mustard cross-linking efficiencies at the 5'-GNC site.

    PubMed

    Sawyer, Gregory A; Frederick, Elizabeth D; Millard, Julie T

    2004-08-01

    Diepoxybutane, diepoxyoctane, and mechlorethamine are cytotoxic agents that induce interstrand cross-links between the N7 positions of deoxyguanosine residues on opposite strands of the DNA duplex preferentially at 5'-GNC sequences. We have systematically varied the identity of either the base 5' to the cross-linked deoxyguanosine residues or the intervening base pair to determine flanking sequence effects on cross-linking efficiency. We used synthetic DNA oligomers containing four 5'-N(1)GN(2)C sites that varied either N(1) or N(2). Interstrand cross-links were purified through denaturing polyacrylamide gel electrophoresis and then subjected to piperidine cleavage. The amount of cleavage at each deoxyguanosine residue, representative of cross-linking efficiency at that site, was determined by sequencing gel analysis. Our data suggest that cross-linking efficiency varies with the identity of N(1) similarly (purines > pyrimidines) for diepoxybutane, diepoxyoctane, and mechlorethamine but that the effects of N(2) differ for the three compounds.

  10. The synthesis and coupling of photoreactive collagen-based peptides to restore integrin reactivity to an inert substrate, chemically-crosslinked collagen

    PubMed Central

    Malcor, Jean-Daniel; Bax, Daniel; Hamaia, Samir W.; Davidenko, Natalia; Best, Serena M.; Cameron, Ruth E.; Farndale, Richard W.; Bihan, Dominique

    2016-01-01

    Collagen is frequently advocated as a scaffold for use in regenerative medicine. Increasing the mechanical stability of a collagen scaffold is widely achieved by cross-linking using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). However, this treatment consumes the carboxylate-containing amino acid sidechains that are crucial for recognition by the cell-surface integrins, abolishing cell adhesion. Here, we restore cell reactivity to a cross-linked type I collagen film by covalently linking synthetic triple-helical peptides (THPs), mimicking the structure of collagen. These THPs are ligands containing an active cell-recognition motif, GFOGER, a high-affinity binding site for the collagen-binding integrins. We end-stapled peptide strands containing GFOGER by coupling a short diglutamate-containing peptide to their N-terminus, improving the thermal stability of the resulting THP. A photoreactive Diazirine group was grafted onto the end-stapled THP to allow covalent linkage to the collagen film upon UV activation. Such GFOGER-derivatized collagen films showed restored affinity for the ligand-binding I domain of integrin α2β1, and increased integrin-dependent cell attachment and spreading of HT1080 and Rugli cell lines, expressing integrins α2β1 and α1β1, respectively. The method we describe has wide application, beyond collagen films or scaffolds, since the photoreactive diazirine will react with many organic carbon skeletons. PMID:26854392

  11. Formation and cleaning function of physically cross-linked dual strengthened water-soluble chitosan-based core-shell particles.

    PubMed

    Dong, Yanrui; Xiao, Congming

    2017-09-01

    Facile and mild ionic cross-linking and freezing/thawing technologies were applied to prepare double strengthened core-shell particles by using water-soluble chitosan (WSC), sodium alginate (SA) and poly(vinyl alcohol) (PVA) as starting materials. The aqueous solution contained WSC and PVA was dropped in ethanol to form beads. The beads were converted into WSC/PVA hydrogel particles by being subjected to three freeze/thaw cycles. Subsequently, ionic cross-linked hydrogel layer was formed around each WSC/PVA particle to generate core-shell particulates. Fourier transform infrared spectra confirmed the combination among various components. Dynamic mechanical thermal analysis indicated that the storage modulus of the core-shell hydrogel was improved obviously. Thermogravimetric analysis exhibited the thermal stability of the particles was also enhanced by incorporation of PVA. It was found that the particles were able to adsorb carbon dioxide, lead ion and copper ion. The adsorption capacities of dry particles toward carbon dioxide, Pb(II) and Cu(II) could reach 199.62, 39.28 and 26.03mg/g, respectively. The rates of the particles for binding Pb(II) and Cu(II) at initial stage were 26.57 and 4.30%/min, respectively. These experimental results suggested that the particles were an efficient sorbent for removing hazardous substances such as carbon dioxide and heavy-metal ions. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Synthesis and applications of shell cross-linked thermoresponsive hybrid micelles based on poly(N-isopropylacrylamide-co-3-(trimethoxysilyl)propyl methacrylate)-b-poly(methyl methacrylate).

    PubMed

    Wei, Hua; Cheng, Cheng; Chang, Cong; Chen, Wen-Qin; Cheng, Si-Xue; Zhang, Xian-Zheng; Zhuo, Ren-Xi

    2008-05-06

    Shell cross-linked (SCL) thermoresponsive hybrid micelles consisting of a cross-linked thermoresponsive hybrid hydrophilic shell and a hydrophobic core domain were synthesized from poly(N-isopropylacrylamide-co-3- (trimethoxysilyl)propyl methacrylate)-b-polymethyl methacrylate (P(NIPAAm-co-MPMA)-b-PMMA) amphiphilic block copolymers. Transmission electron microscopy (TEM) images showed that the SCL micelles formed regularly globular nanoparticles. The SCL micelles showed reversible dispersion/aggregation in response to temperature cycles through an outer polymer shell lower critical solution temperature (LCST) for PNIPAAm at around 33 degrees C, observed by turbidity measurements and dynamic light scattering (DLS). The drug loading and in vitro drug release properties of the SCL micelles bearing a silica-reinforced PNIPAAm shell were further studied, which showed that the SCL micelles exhibited a much improved entrapment efficiency (EE) as well as a slower release rate which allowed the entrapped molecules to be slowly released over a much longer period of time as compared with pure PNIPAAm-b-PMMA micelles.

  13. Cotton fabric finishing with TiO2/SiO2 composite hydrosol based on ionic cross-linking method

    NASA Astrophysics Data System (ADS)

    Xu, Z. J.; Tian, Y. L.; Liu, H. L.; Du, Z. Q.

    2015-01-01

    Cotton fabric was successfully modified by 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHTAC), 1,2,3,4-butanetetracarboxylic acid (BTCA) and TiO2/SiO2 sol. Self-cleaning characteristic was investigated using a Color Measuring & Matching System with 6 h sunlight irradiation. And the stability of TiO2/SiO2 coatings was explored by measuring the washing fastness and wrinkle resistance of treated cotton samples. In addition, whiteness index, crease recovery angle and tensile strength retention (%) of treated samples were evaluated. Moreover, the morphology, structure change and crystallinity of samples were observed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. The results revealed that the samples treated with CHTAC had lower value of whiteness index as compared with original cotton fabric. It was also found that samples treated with BTCA achieved higher crease recovery angle and lower tensile strength. Moreover, the treatment of CHTAC and BTCA had adverse effect on the crystallinity of cotton samples, as treated samples had lower crystallinity in comparison with raw cotton fabrics. Nevertheless, the stability of self-cleaning coatings was better for samples treated with ionic cross-linking treatment (CHTAC + BTCA + TiO2/SiO2) than samples treated with TiO2/SiO2 sol alone. Furthermore, compared with original samples the UV-blocking property of ionic cross-linking treated samples was obviously enhanced.

  14. The synthesis and coupling of photoreactive collagen-based peptides to restore integrin reactivity to an inert substrate, chemically-crosslinked collagen.

    PubMed

    Malcor, Jean-Daniel; Bax, Daniel; Hamaia, Samir W; Davidenko, Natalia; Best, Serena M; Cameron, Ruth E; Farndale, Richard W; Bihan, Dominique

    2016-04-01

    Collagen is frequently advocated as a scaffold for use in regenerative medicine. Increasing the mechanical stability of a collagen scaffold is widely achieved by cross-linking using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). However, this treatment consumes the carboxylate-containing amino acid sidechains that are crucial for recognition by the cell-surface integrins, abolishing cell adhesion. Here, we restore cell reactivity to a cross-linked type I collagen film by covalently linking synthetic triple-helical peptides (THPs), mimicking the structure of collagen. These THPs are ligands containing an active cell-recognition motif, GFOGER, a high-affinity binding site for the collagen-binding integrins. We end-stapled peptide strands containing GFOGER by coupling a short diglutamate-containing peptide to their N-terminus, improving the thermal stability of the resulting THP. A photoreactive Diazirine group was grafted onto the end-stapled THP to allow covalent linkage to the collagen film upon UV activation. Such GFOGER-derivatized collagen films showed restored affinity for the ligand-binding I domain of integrin α2β1, and increased integrin-dependent cell attachment and spreading of HT1080 and Rugli cell lines, expressing integrins α2β1 and α1β1, respectively. The method we describe has wide application, beyond collagen films or scaffolds, since the photoreactive diazirine will react with many organic carbon skeletons.

  15. Microfluidic approaches for the fabrication of gradient crosslinked networks based on poly(ethylene glycol) and hyperbranched polymers for manipulation of cell interactions

    PubMed Central

    Pedron, S; Peinado, C; Bosch, P; Benton, J A; Anseth, K S

    2011-01-01

    High-throughput methods allow rapid examination of parameter space to characterize materials and develop new polymeric formulations for biomaterials applications. One limitation is the difficulty of preparing libraries and performing high-throughput screening with conventional instrumentation and sample preparation. Here, we describe the fabrication of substrate materials with controlled gradients in composition by a rapid method of micromixing followed by a photopolymerization reaction. Specifically, poly(ethylene glycol) dimethacrylate was copolymerized with a hyperbranched multimethacrylate (P1000MA or H30MA) in a gradient manner. The extent of methacrylate conversion and the final network composition were determined by near-infrared spectroscopy, and mechanical properties were measured by nanoindentation. A relationship was observed between the elastic modulus and network crosslinking density. Roughness and hydrophilicity were increased on surfaces with a higher concentration of P1000MA. These results likely relate to a phase segregation process of the hyperbranched macromer that occurs during the photopolymerization reaction. On the other hand, the decrease in the final conversion in H30MA polymerization reactions was attributed to the lower termination rate as a consequence of the softening of the network. Valvular interstitial cell attachment was evaluated on these gradient substrates as a demonstration of studying cell morphology as a function of the local substrate properties. Data revealed that the presence of P1000MA affects cell–material interaction with a higher number of adhered cells and more cell spreading on gradient regions with a higher content of the multifunctional crosslinker. PMID:21105168

  16. Magnetically-Separable and Highly-Stable Enzyme System Based on Crosslinked Enzyme Aggregates Shipped in Magnetite-Coated Mesoporous Silica

    SciTech Connect

    Lee, Jinwoo; Na, Hyon Bin; Kim, Byoung Chan; Lee, Jin Hyung; Lee, Byoungsoo; Kwak, Ja Hun; Hwang, Yosun; Park, Je-Geun; Gu, Man Bock; Kim, Jaeyun; Joo, Jin; Shin, Chae-Ho; Grate, Jay W.; Hyeon, Taeghwan; Kim, Jungbae

    2009-10-15

    Magnetically-separable and highly-stable enzyme system was developed by adsorption of enzymes in superparamagnetic hierarchically ordered mesocellular mesoporous silica (M-HMMS) and subsequent enzyme crosslinking. Superparamagnetic nanoparticles were homogeneously incorporated into hierarchically-ordered mesocellular mesoporous silica (HMMS) by the decomposition of preformed iron propionate complex. The size of incorporated superparamagnetic 15 nanoparticles was around 5 nm, generating a magnetically separable host with high pore volumes and large pores (M-HMMS). α-chymotrypsin (CT) was adsorbed into M-HMMS with high loading (~30 wt%) in less than 30 minutes. Glutaraldehyde (GA) treatment of adsorbed CT resulted in nanometer scale crosslinked enzyme aggregates in M-HMMS (CLEA-M). The activity of these CT aggregates in M-HMMS (CLEA-M-CT) was 34 times than that of simply adsorbed CT in M20 HMMS, due to an effective prevention of enzyme leaching during washing via a ship-in-a-bottle approach. CLEA-M-CT maintained the intial activity not only under shaking (250 rpm) for 30 days, but also under recycled uses of 35 times. The same approach was employed for the synthesis of CLEA-M of lipase (CLEA-M-LP), and proven to be effective in improving the loading, activity, and stability of enzyme when compared to those of adsorbed LP in M-HMMS.

  17. Biocompatible fibrous networks of cellulose nanofibres and collagen crosslinked using genipin: potential as artificial ligament/tendons.

    PubMed

    Mathew, Aji P; Oksman, Kristiina; Pierron, Dorothée; Harmand, Marie-Françoise

    2013-03-01

    Bio-based fibrous nanocomposites of cellulose nanofibres and non-crosslinked/crosslinked collagen were prepared by in situ pH-induced fibrillation of collagen phase and sterilized using gamma rays at 25 KGy. Collagen phase is crosslinked using genipin, a bio-based crosslinker that introduces flexible crosslinks. Microscopy studies of the prepared materials showed nanostructured fibrous collagen and cellulose dispersed in collagen matrix. Mechanical performance of the sterilized nanocomposites was close to that of natural ligament and tendon, in simulated body conditions. Cytocompatibility studies indicated that these nanocomposites allowed human ligament cell and human endothelial cell adhesion, growth, and differentiation; which is eminently favourable to ligament tissue engineering.

  18. Biologically relevant oxidants cause bound proteins to readily oxidatively cross-link at Guanine.

    PubMed

    Solivio, Morwena J; Nemera, Dessalegn B; Sallans, Larry; Merino, Edward J

    2012-02-20

    Oxidative DNA-protein cross-links have received less attention than other types of DNA damage and remain as one of the least understood types of oxidative lesion. A model system using ribonuclease A and a 27-nucleotide DNA was used to determine the propensity of oxidative cross-linking to occur in the presence of oxidants. Cross-link formation was examined using four different oxidation systems that generate singlet oxygen, superoxide, and metal-based Fenton reactions. It is shown that oxidative cross-linking occurs in yields ranging from 14% to a maximal yield of 61% in all oxidative systems when equivalent concentrations of DNA and protein are present. Because singlet oxygen is the most efficient oxidation system in generating DNA-protein cross-links, it was chosen for further analyses. Cross-linking occurred with single-stranded DNA binding protein and not with bovine serum albumin. Addition of salt lowered nonspecific binding affinity and lowered cross-link yield by up to 59%. The yield of cross-linking increased with increased ratios of protein compared with DNA. Cross-linking was highly dependent on the number of guanines in a DNA sequence. Loss of guanine content on the 27-nucleotide DNA led to nearly complete loss in cross-linking, while primer extension studies showed cross-links to predominantly occur at guanine base on a 100-nucleotide DNA. The chemical species generated were examined using two peptides derived from the ribonuclease A sequence, N-acetyl-AAAKF and N-acetyl-AYKTT, which were cross-linked to 2'-deoxyguanosine. The cross-link products were spiroiminodihydantoin, guanidinohydantoin, and tyrosyl-based adducts. Formation of tyrosine-based adducts may be competitive with the more well-studied lysine-based cross-links. We conclude that oxidative cross-links may be present at high levels in cells since the propensity to oxidatively cross-link is high and so much of the genomic DNA is coated with protein.

  19. Intersatellite optical crosslink testbed for 300/650 Mbps

    NASA Astrophysics Data System (ADS)

    Carlson, R. T.

    This paper described the design, fabrication, and preliminary testing of a high datarate intersatellite laser crosslink testbed being built at The MITRE Corporation in 1993 on IR&D funding. Wideband laser drivers and optical receivers for signals at datarates of 300 Mbps and 650 Mbps have been designed and built, and are being integrated into a laboratory testbed for system level testing. This testbed includes laser wavelength division multiplexing of three colors, representative of that required for a flight implementation. The optical crosslink testbed has input/output interfaces with RF signals from uplink/downlink hardware simulators, described in a companion paper. The design of this optical crosslink is unique, in that it is based on direct analog modulation of the crosslink lasers with the wideband signal waveform from an incoming RF link (i.e., an uplink or space crosslink). Nearly all of the optical crosslink designs proposed to date have been for digitally modulated laser links, typically for applications where a wideband digital data stream originates at a sensing or imaging satellite and needs to be crosslinked to a destination satellite. The motivation for the analog modulation scheme in this paper is driven by end-to-end applications that include satellite uplinks, crosslinks, and downlinks, to avoid the requirement for processing satellites to detect, demodulate, regenerate, and remodulate multiple FDM channels of data at each of the two (or more) satellite crosslink nodes. This is particularly important for wideband channels that represent a composite of many different signals and modulation formats. The datarates, frequencies, interfaces, and requirements chosen for this testbed were based on the NASA TDRSS satellite and an upgrade being considered for a TDRSS-to-TDRSS crosslink capability. More generally, these datarates and the resulting testbed implementation are representative of an arbitrary RF-modulated wideband optical crosslink. The optical

  20. Swelling, mechanical, and barrier properties of albedo-based films prepared in the presence of phaseolin cross-linked or not by transglutaminase.

    PubMed

    Mariniello, L; Giosafatto, C V L; Di Pierro, P; Sorrentino, A; Porta, R

    2010-09-13

    Edible films were obtained from Citrus paradisi grapefruit albedo homogenates and bean protein phaseolin modified or not by the enzyme transglutaminase. Swelling capability, barrier performance to water vapor, oxygen and carbon dioxide, and mechanical properties of such films were investigated. The addition of the protein, mostly in the presence of transglutaminase, provide films less swellable at pH values above 5 compared to films made by albedo homogenates only, whereas the action of the enzyme clearly improves mechanical properties producing more stretchable and elastic films. Moreover, transglutaminase-mediated cross-linking of phaseolin gives rise to films less permeable to carbon dioxide and able to offer a high barrier to water vapor. These findings suggest that albedo-phaseolin film prepared in the presence of transglutaminase can be a promising candidate to be used as food edible wrap.

  1. Isolation and Characterization of Supercoiled Circular Deoxyribonucleic Acid from Beta-Hemolytic Strains of Escherichia coli

    PubMed Central

    Goebel, Werner; Schrempf, Hildgund

    1971-01-01

    Covalently closed circular deoxyribonucleic acid (DNA) molecules were isolated by cesium chloride centrifugation in the presence of ethidium bromide from a naturally occurring beta-hemolytic Escherichia coli strain (SC52). The open circular forms have contour lengths of 2.25 ± 0.1 μm, 24.0 ± 0.3 μm, and 29.5 ± 0.5 μm. The beta-hemolytic character of E. coli SC52 can be transferred by conjugation to a nonhemolytic recipient strain. Analysis of the supercoiled DNA of the hemolytic recipient demonstrated that the two large supercoiled DNA molecules of E. coli SC52 are transferred during this event, too. A beta-hemolytic laboratory E. coli strain and several of its derivatives have been shown to contain at least one circular DNA molecule, slightly larger in size than those isolated from E. coli SC52 and its conjugant. The possible significance of these DNA molecules for hemolysin production and transfer is discussed. Images PMID:4929855

  2. Role of deoxyribonucleic acid ligase in a doxyribonucleic acid membrane fraction extracted from pneumococci.

    PubMed Central

    Greene, M; Firshein, W

    1976-01-01

    Deoxyribonucleic acid (DNA) ligase has been detected in a DNA membrane fraction extracted from Pneumococcus. The specific activity of the enzyme in this fraction is 10-fold greater than in the remaining cell extract. It remains firmly bound (with other enzymes) to the complex after a purification procedure in which a considerable percentage of the macromolecules are dissociated. The ligase acts in two ways in the DNA membrane fraction in vitro. One, it catalyzes the linkage of small-molecular-weight pieces of newly synthesized DNA into heavier-molecular-weight DNA strands as shown by others (M Gellert, 1976; R. Okazaki, A. Sugino, S. Hirose, T. Okazaki, Y. Imae, R. Kainuma-Kuroda, T. Ogawa, M. Arisawa, and Y. Kurosowa, 1973; B. Olivera and I. Lehman, 14; and A. Sugino, S. Hirose, and R. Okazaki, 1972) and, two, it protects DNA from degradation by deoxyribonucleases. This latter effect is due to a competition between the ability of the nucleases to degrade DNA and the ability of DNA ligase to seal the nicks produced by these degradative enzymes. The ligase acts cooperatively with other enzymes in the DNA membrane fraction to synthesize DNA. PMID:4433

  3. Formation of an 8-hydroxyguanine moiety in deoxyribonucleic acid on gamma-irradiation in aqueous solution

    SciTech Connect

    Dizdaroglu, M.

    1985-07-30

    Isolation and characterization of a novel radiation-induced product, i.e., the 8-hydroxyguanine residue, produced in deoxyribonucleic acid (DNA), 2'-deoxyguanosine, and 2'-deoxyguanosine 5'-monophosphate by gamma-irradiation in aqueous solution, are described. For this purpose, gamma-irradiated DNA was first hydrolyzed with a mixture of four enzymes, i.e., DNase I, spleen and snake venom exonucleases, and alkaline phosphatase. Analysis of the resulting mixture by capillary gas chromatography-mass spectrometry after trimethylsilylation revealed the presence of a product, which was identified as 8-hydroxy-2'-deoxyguanosine on the basis of the typical fragment ions of its trimethylsilyl (Me3Si) derivative. This product was then isolated by using reversed-phase high-performance liquid chromatography. The UV and proton nuclear magnetic resonance spectra taken from the isolated product confirmed the structure suggested by the mass spectrum of its Me3Si derivative. The yield of 8-hydroxyguanine was also measured. Its mechanism of formation is believed to involve OH radical addition to the C-8 position of guanine followed by oxidation of the radical adduct.

  4. Automated Quantification of the Impact of Defects on the Mechanical Behavior of Deoxyribonucleic acid Origami Nanoplates.

    PubMed

    Liang, Bowen; Nagarajan, Anand; Hudoba, Michael W; Alvarez, Ricardo; Castro, Carlos E; Soghrati, Soheil

    2017-04-01

    Deoxyribonucleic acid (DNA) origami is a method for the bottom-up self-assembly of complex nanostructures for applications, such as biosensing, drug delivery, nanopore technologies, and nanomechanical devices. Effective design of such nanostructures requires a good understanding of their mechanical behavior. While a number of studies have focused on the mechanical properties of DNA origami structures, considering defects arising from molecular self-assembly is largely unexplored. In this paper, we present an automated computational framework to analyze the impact of such defects on the structural integrity of a model DNA origami nanoplate. The proposed computational approach relies on a noniterative conforming to interface-structured adaptive mesh refinement (CISAMR) algorithm, which enables the automated transformation of a binary image of the nanoplate into a high fidelity finite element model. We implement this technique to quantify the impact of defects on the mechanical behavior of the nanoplate by performing multiple simulations taking into account varying numbers and spatial arrangements of missing DNA strands. The analyses are carried out for two types of loading: uniform tensile displacement applied on all the DNA strands and asymmetric tensile displacement applied to strands at diagonal corners of the nanoplate.

  5. Size, Composition, and Structure of the Deoxyribonucleic Acid of Herpes Simplex Virus Subtypes 1 and 2

    PubMed Central

    Kieff, Elliott D.; Bachenheimer, Steven L.; Roizman, Bernard

    1971-01-01

    Studies of the size, composition, and structure of the deoxyribonucleic acid (DNA) of the F and G prototypes of herpes simplex virus (HSV) subtypes 1 and 2 (HSV-1 and HSV-2) showed the following. (i) As previously reported by Good-heart et al. HSV-1 and HSV-2 DNA have a buoyant density of 1.726 and 1.728 g/cm3, corresponding to 67 and 69 guanine ± cytosine moles per cent, respectively. The difference in guanine plus cytosine content of the DNA species was confirmed by the finding of a 1 C difference in Tm. (ii) The DNA from purified virus on cocentrifugation with T4 DNA in neutral sucrose density gradients sedimented at 55S, corresponding to 99 ± 5 million daltons in molecular weight. HSV-1 and HSV-2 DNA could not be differentiated with respect to size. (iii) Cosedimentation of alkali-denatured DNA from purified virus with T4 DNA on alkaline sucrose density gradients consistently yielded several bands of single-stranded HSV DNA ranging from fragments 7 × 106 daltons to intact strands 48 × 106 daltons in molecular weight. PMID:4329966

  6. Transcription of exogenous and endogenous deoxyribonucleic acid templates in cold-shocked Bacillus subtilis.

    PubMed Central

    Kuhl, S J; Brown, L R

    1980-01-01

    Ribonucleic acid (RNA) synthesis was examined in cold-shocked Bacillus subtilis cells. The cells were grown to mid-log stage, harvested, and cold shocked. RNA synthesis was monitored by the incorporation of [3H]uridine triphosphate or [alpha 32P]adenosine triphosphate into trichloroacetic acid-precipitable material in the presence of all four nucleoside triphosphates. The inhibition of RNA synthesis in cold-shocked cells by lipiarmycin, ethidium bromide, rifampin. or streptolydigin was analyzed using mutant or wild-type cells. Also examined were the effects of temperature, salt concentration, and the addition of polyamines or highly phosphorylated nucleotides. In ultraviolet-irradiated and cold-shocked cells, RNA wynthesis decreased to low levels. The addition of exogenous phi 29 or TSP-1 template to these cells caused a 13- to 20-fold increase in RNA synthesis, as monitored by trichloroacetic acid-precipitable counts. RNA synthesized in the presence of phi 29 deoxyribonucleic acid (DNA) hybridizes mainly to EcoRI fragments A and C of phi 29 DBA, These two fragments direct transcription by purified RNA polymerase in vitro and hybridize to early phi 29 DNA produced in vivo. Our results with TSP-1 DNA in this system indicated that the RNA produced hybridizes to the same fragments as early RNA produced in vivo. Plasmic pUB110 DNA was not transcribed in this system. Images PMID:6157674

  7. Spermidine-Deoxyribonucleic acid interaction in vitro and in Escherichia coli.

    PubMed Central

    Rubin, R L

    1977-01-01

    The binding of spermidine to deoxyribonucleic acid (DNA) was studied by equilibrium dialysis in a wide range of salt concentrations. The association constants ranged from 6 x 10(5) M-1 in 1 mM sodium cacodylate, pH 7.5, to 3 x 10(2) M-1 in 0.3 M NaCl. MgCl2 reduced spermidine-DNA interaction even more than NaCl so that in moderate-ionic-strength solutions (0.3 M NaCl, 0.002 M MgCl2) there was little detectable binding. Low-ionic-strength media were used to isolate DNA from Escherichia coli by a method shown to minimize loss of spermidine from the DNA. Considerable spermidine was associated with E. coli DNA, but control experiments indicated that complex formation had taken place during or after lysis of the cells. Exogenous DNA or ribonucleic acid added to spheroplasts at the time of their lysis caused most of the cellular spermidine to be scavenged by the extra nucleic acid. The data suggest that spermidine is relatively free in the cell and thereby capable of strong (high-affinity) associations with nucleic acids only after the ionic strength of the cell environment is lowered. PMID:320196

  8. Properties of the Deoxyribonucleic Acid Contained in the Defective Particle Coliphage 15 1

    PubMed Central

    Frampton, E. W.; Mandel, M.

    1970-01-01

    Escherichia coli strain 15 TAU, which requires thymine, arginine, and uracil for growth and harbors an apparently defective prophage, was induced by exposure to ultraviolet light (580 ergs/mm2) or to mitomycin C (5 μg/ml). Phage particles (coliphage 15) were recovered from the resulting lysate by treatment with deoxyribonuclease, filtration, and several cycles of differential centrifugation. Analysis of the phage particles obtained by using cesium chloride density gradient centrifugation in a preparative ultracentrifuge resulted in the resolution of three components. The major component had a peak density of 1.52 to 1.53 g/cm3 followed by components with densities of 1.5 and 1.49 g/cm3. The guanine plus cytosine content of coliphage 15 deoxyribonucleic acid (DNA) was determined by both analytical ultracentrifugation in cesium chloride and by thermal denaturation in standard saline citrate buffer. Respective values of 46.4 ± 1% and 46.6 ± 1% guanine plus cytosine content were obtained. Coliphage 15 DNA formed molecular hybrids with messenger ribonucleic acid (RNA) from both uninduced and ultraviolet-induced cultures of E. coli 15 TAU, but did not hybridize with E. coli ribosomal RNA. The molecular weight of coliphage 15 DNA was determined by constant velocity sucrose density gradient centrifugation to be about 33 × 106 daltons. PMID:4909911

  9. Effects of intradermally administered plasmid deoxyribonucleic acid on ovine popliteal lymph node morphology.

    PubMed

    Uwiera, R R; Rankin, R; Adams, G P; Pontarollo, R; van Drunen Littel-van den Hurk, S; Middleton, D M; Babiuk, L A; Griebel, P J

    2001-02-01

    In the last decade it has become apparent that bacterial deoxyribonucleic acid (DNA) is recognized as a "danger signal" by the mammalian immune system. To investigate this interaction, sheep were injected intradermally two centimeters distal to the lateral prominence of the fibular head with 400 microg of purified plasmid DNA. Over a 28-day period ultrasound measurements indicated a progressive increase in size of both plasmid and saline (controls) treated popliteal lymph nodes and at Day 30 macroscopic and histological measurements of the lymph nodes were determined. Compared with the contralateral control lymph nodes, plasmid exposed lymph nodes were heavier (2.8 +/- 0.1g vs. 2.0 +/- 0.6 g) and displayed prominent histological changes in the cortex and medulla. Average medullary cord thickness (114.2 +/- 25.2 microm) and the average distance across medullary sinuses (64.4 +/- 2.5 microm) were significantly greater after plasmid exposure relative to contralateral controls (62.7 +/- 14.9 microm and 36.5 +/- 1.0 microm, respectively). Total number of germinal centers (71.4 +/- 17.7) and the total area of germinal centers (4.0 +/- 1.3 mm(2)) within the cortex of popliteal lymph nodes exposed to plasmid were also significantly greater than the controls (40.4 +/- 11.4 and 1.6 +/- 0.5 mm(2), respectively). Our results demonstrate that a single exposure to plasmid DNA has long term effects on regional lymph node weight and morphology.

  10. Gating of single-layer graphene with single-stranded deoxyribonucleic acids.

    PubMed

    Lin, Jian; Teweldebrhan, Desalegne; Ashraf, Khalid; Liu, Guanxiong; Jing, Xiaoye; Yan, Zhong; Li, Rong; Ozkan, Mihri; Lake, Roger K; Balandin, Alexander A; Ozkan, Cengiz S

    2010-05-21

    Patterning of biomolecules on graphene layers could provide new avenues to modulate their electrical properties for novel electronic devices. Single-stranded deoxyribonucleic acids (ssDNAs) are found to act as negative-potential gating agents that increase the hole density in single-layer graphene. Current-voltage measurements of the hybrid ssDNA/graphene system indicate a shift in the Dirac point and "intrinsic" conductance after ssDNA is patterned. The effect of ssDNA is to increase the hole density in the graphene layer, which is calculated to be on the order of 1.8 x 10(12) cm(-2). This increased density is consistent with the Raman frequency shifts in the G-peak and 2D band positions and the corresponding changes in the G-peak full width at half maximum. Ab initio calculations using density functional theory rule out significant charge transfer or modification of the graphene band structure in the presence of ssDNA fragments.

  11. Feasibility for quantitative determination of deoxyribonucleic acid by using near-infrared diffuse reflectance spectroscopy.

    PubMed

    Yang, Yafei; Tu, Jiarun; Cai, Wensheng; Shao, Xueguang

    2012-09-15

    A method for quantitative determination of fish sperm deoxyribonucleic acid (fsDNA) in solutions was developed by using adsorption preconcentration and near-infrared diffuse reflectance spectroscopy (NIRDRS). A high capacity adsorbent of amino-modified silica particle (AMSP) was prepared for preconcentration of fsDNA in solutions. Under the optimized conditions, the adsorption rate can be above 90% within 3 min. After adsorbing the DNA onto the adsorbent, near-infrared (NIR) spectra in diffuse reflectance mode were measured and partial least squares (PLS) model was established for fast quantitative prediction. The results show that the correlation coefficient (R) between the predicted and the reference concentration is 0.9894 and the recoveries are in the range of 92.9-123.4% for the validation samples in the concentration range of 3.00-29.38 mg L(-1). Therefore, the feasibility for quantitative analysis of DNA in solutions by NIRDRS is proved. This may provide an alternative way for fast determination of DNA in solutions.

  12. Repair of Single-Strand Deoxyribonucleic Acid Breaks in Ultraviolet Light-Irradiated Haemophilus influenzae

    PubMed Central

    Kantor, George J.; Barnhart, B. J.

    1973-01-01

    The wild-type strain and mutants of Haemophilus influenzae, sensitive or resistant to ultraviolet light (UV) as defined by colony-forming ability, were examined for their ability to perform the incision and rejoining steps of the deoxyribonucleic acid (DNA) dark repair process. Although UV-induced pyrimidine dimers are excised by the wild-type Rd and a resistant mutant BC200, the expected single-strand DNA breaks could not be detected on alkaline sucrose gradients. Repair of the gap resulting from excision must be rapid when experimental conditions described by us are employed. Single-strand DNA breaks were not detected in a UV-irradiated sensitive mutant (BC100) incapable of excising pyrimidine dimers, indicating that this mutant may be defective in a dimer-recognizing endonuclease. No single-strand DNA breaks were detected in a lysogen BC100(HP1c1) irradiated with a UV dose large enough to induce phage development in 80% of the cells. PMID:4540247

  13. Topical Cross-Linked HA-Based Hydrogel Accelerates Closure of Corneal Epithelial Defects and Repair of Stromal Ulceration in Companion Animals.

    PubMed

    Williams, David L; Wirostko, Barbara M; Gum, Glenwood; Mann, Brenda K

    2017-09-01

    The purpose of this study was to determine the safety of topical ocular administration of a cross-linked, modified hyaluronic acid (xCMHA-S) hydrogel, and its effectiveness in accelerating repair and closure of acute and nonhealing corneal ulcers in companion animals as a veterinary treatment and its utility as a model for therapy in human corneal ulceration. Two concentrations of xCMHA-S (0.33% and 0.75%) were topically administered to the eyes of rabbits six times daily for 28 days to assess safety. Then, 30 dogs and 30 cats with spontaneous acute corneal ulcers were treated with either xCMHA-S (0.75%) or a non-cross-linked hyaluronic acid (HA) solution (n = 15 per group for each species), three times daily until the ulcer had healed. Finally, 25 dogs with persistent nonhealing corneal ulcers were treated with xCMHA-S (0.75%) twice daily until the ulcer had healed. Both concentrations of the xCMHA-S hydrogel were well tolerated, safe, and nontoxic in the 28-day exaggerated dosing study in healthy rabbits. Topically applied xCMHA-S significantly accelerated closure of acute corneal stromal ulcers in dogs and cats compared with a non-cross-linked HA solution. Further, topical administration of the xCMHA-S aided in closure of nonhealing corneal stromal ulcers in dogs. Hyaluronic acid has previously been shown to aid in corneal wound repair. This study demonstrates that a cross-linked, modified HA hydrogel provides further benefit by accelerating time to corneal wound closure compared to a non-cross-linked HA solution in companion animals, and therefore may be beneficial in fulfilling an unmet need in humans.

  14. Electrospinning formaldehyde cross-linked zein solutions

    USDA-ARS?s Scientific Manuscript database

    In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as the cross-linking reagent before spinning. The cross-linking reaction was carried out in either acetic acid or ethanolic-HCl where the amount of cross-linking reagent was between 1 and...

  15. Molecular and macro-scale analysis of enzyme-crosslinked silk hydrogels for rational biomaterial design.

    PubMed

    McGill, Meghan; Coburn, Jeannine M; Partlow, Benjamin P; Mu, Xuan; Kaplan, David L

    2017-09-14

    Silk fibroin-based hydrogels have exciting applications in tissue engineering and therapeutic molecule delivery; however, their utility is dependent on their diffusive properties. The present study describes a molecular and macro-scale investigation of enzymatically-crosslinked silk fibroin hydrogels, and demonstrates that these systems have tunable crosslink density and diffusivity. We developed a liquid chromatography tandem mass spectroscopy (LC-MS/MS) method to assess the quantity and order of covalent tyrosine crosslinks in the hydrogels. This analysis revealed between 28 and 56% conversion of tyrosine to dityrosine, which was dependent on the silk concentration and reactant concentration. The crosslink density was then correlated with storage modulus, revealing that both crosslinking and protein concentration influenced the mechanical properties of the hydrogels. The diffusive properties of the bulk material were studied by fluorescence recovery after photobleaching (FRAP), which revealed a non-linear relationship between silk concentration and diffusivity. As a result of this work, a model for synthesizing hydrogels with known crosslink densities and diffusive properties has been established, enabling the rational design of silk hydrogels for biomedical applications. Hydrogels from naturally-derived silk polymers offer versitile opportunities in the biomedical field, however, their design has largely been an empirical process. We present a fundamental study of the crosslink density, storage modulus, and diffusion behavior of enzymatically-crosslinked silk hydrogels to better inform scaffold design. These studies revealed unexpected non-linear trends in the crosslink density and diffusivity of silk hydrogels with respect to protein concentration and crosslink reagent concentration. This work demonstrates the tunable diffusivity and crosslinking in silk fibroin hydrogels, and enables the rational design of biomaterials. Further, the characterization methods

  16. Influence of different crosslinking treatments on the physical properties of collagen membranes.

    PubMed

    Charulatha, V; Rajaram, A

    2003-02-01

    The physical properties of collagen-based biomaterials are profoundly influenced by the method and extent of crosslinking. In this study, the influence of various crosslinking treatments on the physical properties of reconstituted collagen membranes was assessed. Five crosslinking agents viz., GTA, DMS, DTBP, a combination of DMS and GTA and acyl azide method were used to stabilize collagen matrices. Crosslinking density, swelling ratio, thermo-mechanical properties, stress-strain characteristics and resistance to collagenase digestion were determined to evaluate the physical properties of crosslinked matrices. GTA treatment induced the maximum number of crosslinks (13) while DMS treatment induced the minimum (7). Of the two diimidoesters (DMS and DTBP), DTBP was a more effective crosslinking agent due to the presence of disulphide bonds in the DTBP crosslinks. T(s) for DTBP and DMS crosslinked collagen were 80 degrees C and 70 degrees C, and their HIT values were 5.4 and 2.85MN/m(2), respectively. Low concentration of GTA (0.01%) increased the crosslinking density of an already crosslinked matrix (DMS treated matrix) from 7 to 12. Lowest fracture energy was observed for the acyl azide treated matrix (0.61MJ/m(3)) while the highest was observed for the GTA treated matrix (1.97MJ/m(3)). The tensile strength of GTA treated matrix was maximum (12.4MPa) and that of acyl azide treated matrix was minimum (7.2MPa). GTA, DTBP and acyl azide treated matrices were equally resistant to collagenase degradation with approximately 6% solubilization after 5h while the DMS treated was least stable with 52.4% solubilization after the same time period. The spatial orientation of amino acid side chain residues on collagen plays an important role in determining the crosslinking density and consequent physical properties of the collagen matrix.

  17. In vitro cross-linking of elastin peptides and molecular characterization of the resultant biomaterials.

    PubMed

    Heinz, Andrea; Ruttkies, Christoph K H; Jahreis, Günther; Schräder, Christoph U; Wichapong, Kanin; Sippl, Wolfgang; Keeley, Fred W; Neubert, Reinhard H H; Schmelzer, Christian E H

    2013-04-01

    Elastin is a vital protein and the major component of elastic fibers which provides resilience to many vertebrate tissues. Elastin's structure and function are influenced by extensive cross-linking, however, the cross-linking pattern is still unknown. Small peptides containing reactive allysine residues based on sequences of cross-linking domains of human elastin were incubated in vitro to form cross-links characteristic of mature elastin. The resultant insoluble polymeric biomaterials were studied by scanning electron microscopy. Both, the supernatants of the samples and the insoluble polymers, after digestion with pancreatic elastase or trypsin, were furthermore comprehensively characterized on the molecular level using MALDI-TOF/TOF mass spectrometry. MS(2) data was used to develop the software PolyLinX, which is able to sequence not only linear and bifunctionally cross-linked peptides, but for the first time also tri- and tetrafunctionally cross-linked species. Thus, it was possible to identify intra- and intermolecular cross-links including allysine aldols, dehydrolysinonorleucines and dehydromerodesmosines. The formation of the tetrafunctional cross-link desmosine or isodesmosine was unexpected, however, could be confirmed by tandem mass spectrometry and molecular dynamics simulations. The study demonstrated that it is possible to produce biopolymers containing polyfunctional cross-links characteristic of mature elastin from small elastin peptides. MALDI-TOF/TOF mass spectrometry and the newly developed software PolyLinX proved suitable for sequencing of native cross-links in proteolytic digests of elastin-like biomaterials. The study provides important insight into the formation of native elastin cross-links and represents a considerable step towards the characterization of the complex cross-linking pattern of mature elastin. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Biomechanical Analysis of a Pedicle Screw-Rod System with a Novel Cross-Link Configuration

    PubMed Central

    Hara, Masahito; Umebayashi, Daisuke; Haimoto, Shoichi; Yamamoto, Yu; Nishimura, Yusuke; Wakabayashi, Toshihiko

    2016-01-01

    Study Design The strength effects of a pedicle screw-rod system supplemented with a novel cross-link configuration were biomechanically evaluated in porcine spines. Purpose To assess the biomechanical differences between a conventional cross-link pedicle screw-rod system versus a novel cross-link instrumentation, and to determine the effect of the cross-links. Overview of Literature Transverse cross-link systems affect torsional rigidity, but are thought to have little impact on the sagittal motion of spinal constructs. We tested the strength effects in pullout and flexion-compression tests of novel cross-link pedicle screw constructs using porcine thoracic and lumbar vertebrae. Methods Five matched thoracic and lumbar vertebral segments from 15 porcine spines were instrumented with 5.0-mm pedicle screws, which were then connected with 6.0-mm rods after partial corpectomy in the middle vertebral body. The forces required for construct failure in pullout and flexion-compression tests were examined in a randomized manner for three different cross-link configurations: un-cross-link control, conventional cross-link, and cross-link passing through the base of the spinous process. Statistical comparisons of strength data were analyzed using Student's t-tests. Results The spinous process group required a significantly greater pullout force for construct failure than the control group (p=0.036). No difference was found between the control and cross-link groups, or the cross-link and spinous process groups in pullout testing. In flexion-compression testing, the spinous processes group required significantly greater forces for construct failure than the control and cross-link groups (p<0.001 and p=0.003, respectively). However, there was no difference between the control and cross-link groups. Conclusions A novel cross-link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and

  19. Probe Into the Influence of Crosslinking on CO2 Permeation of Membranes

    PubMed Central

    Li, Jinghui; Chen, Zhuo; Umar, Ahmad; Liu, Yang; Shang, Ying; Zhang, Xiaokai; Wang, Yao

    2017-01-01

    Crosslinking is an effective way to fabricate high-selective CO2 separation membranes because of its unique crosslinking framework. Thus, it is essentially significant to study the influence of crosslinking degree on the permeation selectivities of CO2. Herein, we report a successful and facile synthesis of a series of polyethylene oxide (PEO)-based diblock copolymers (BCP) incorporated with an unique UV-crosslinkable chalcone unit using Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) process. The membranes of as-prepared BCPs show superior carbon dioxide (CO2) separation properties as compared to nitrogen (N2) after UV-crosslinking. Importantly, the influence of different proportions of crosslinked chalcone on CO2 selectivities was systematically investigated, which revealed that CO2 selectivities increased obviously with the enhancement of chalcone fractions within a certain limit. Further, the CO2 selectivities of block copolymer with the best block proportion was studied by varying the crosslinking time which confirmed that the high crosslinking degree exhibited a better CO2/N2 (αCO2/N2) selectivities. A possible mechanism model revealing that the crosslinking degree played a key role in the gas separation process was also proposed. PMID:28051190

  20. Probe Into the Influence of Crosslinking on CO2 Permeation of Membranes

    NASA Astrophysics Data System (ADS)

    Li, Jinghui; Chen, Zhuo; Umar, Ahmad; Liu, Yang; Shang, Ying; Zhang, Xiaokai; Wang, Yao

    2017-01-01

    Crosslinking is an effective way to fabricate high-selective CO2 separation membranes because of its unique crosslinking framework. Thus, it is essentially significant to study the influence of crosslinking degree on the permeation selectivities of CO2. Herein, we report a successful and facile synthesis of a series of polyethylene oxide (PEO)-based diblock copolymers (BCP) incorporated with an unique UV-crosslinkable chalcone unit using Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) process. The membranes of as-prepared BCPs show superior carbon dioxide (CO2) separation properties as compared to nitrogen (N2) after UV-crosslinking. Importantly, the influence of different proportions of crosslinked chalcone on CO2 selectivities was systematically investigated, which revealed that CO2 selectivities increased obviously with the enhancement of chalcone fractions within a certain limit. Further, the CO2 selectivities of block copolymer with the best block proportion was studied by varying the crosslinking time which confirmed that the high crosslinking degree exhibited a better CO2/N2 (αCO2/N2) selectivities. A possible mechanism model revealing that the crosslinking degree played a key role in the gas separation process was also proposed.

  1. Crosslinking density influences chondrocyte metabolism in dynamically loaded photocrosslinked poly(ethylene glycol) hydrogels.

    PubMed

    Bryant, Stephanie J; Chowdhury, Tina T; Lee, David A; Bader, Dan L; Anseth, Kristi S

    2004-03-01

    In approaches to tissue engineer articular cartilage, an important consideration for in situ forming cell carriers is the impact of mechanical loading on the cell composite structure and function. Photopolymerized hydrogel scaffolds based on poly(ethylene glycol) (PEG) may be synthesized with a range of crosslinking densities and corresponding macroscopic properties. This study tests the hypothesis that changes in the hydrogel crosslinking density influences the metabolic response of encapsulated chondrocytes to an applied load. PEG hydrogels were formulated with two crosslinking densities that resulted in gel compressive moduli ranging from 60 to 670 kPa. When chondrocytes were encapsulated in these PEG gels, an increase in crosslinking density resulted in an inhibition in cell proliferation and proteoglycan synthesis. Moreover, when the gels were dynamically loaded for 48 h in unconfined compression with compressive strains oscillating from 0 to 15% at a frequency of 1 Hz, cell proliferation and proteoglycan synthesis were affected in a crosslinking-density-dependent manner. Cell proliferation was inhibited in both crosslinked gels, but was greater in the highly crosslinked gel. In contrast, dynamic loading did not influence proteoglycan synthesis in the loosely crosslinked gel, but a marked decrease in proteoglycan production was observed in the highly crosslinked gel. In summary, changes in PEG hydrogel properties greatly affect how chondrocytes respond to an applied dynamic load.

  2. Fabrication of a deoxyribonucleic acid polymer ridge waveguide electro-optic modulator by nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Fehrman Cory, Emily Marie

    The purpose of this dissertation is to develop the nanoimprint lithography (NIL) technique for direct patterning of the deoxyribonucleic acid biopolymer DNA-CTMA. The Mach Zehnder modulator was chosen as the test device to demonstrate the NIL patterning technique for DNA-CTMA as well as the unique optical and electrical properties of the DNA-CTMA as a cladding material for poled electro-optic polymers. Towards this goal, a DNA-CTMA clad inverted ridge waveguide is demonstrated at 633 nm and 1550 nm, the structure of which is patterned directly in the DNA-CTMA cladding by NIL. Additionally, EO modulation is demonstrated in a slab waveguide structure with DNA-CTMA cladding and SEO110 EO polymer core. Marine-derived deoxyribonucleic acid biopolymer (DNA-CTMA) is a green, nontoxic, low cost optical polymer material derived from waste products of the salmon fishing industry. It exhibits low optical loss at 1550 nm, forms a thin flexible film, is compatible with existing poled polymer technologies, increases the poling efficiency when used as a low resistivity cladding layer, and is thermally stable to 200 oC. Due to chemical incompatibility with the photoresists and the associated solvents, NIL has been developed for patterning the DNA biopolymer cladding to form an inverted ridge waveguide for the basis of the Mach Zehnder modulator. While DNA-CTMA presents significant advantages over other commonly used cladding materials for the 1550 nm wavelength range, one of the commonly used bands for optical communications, the mechanical properties and environmental susceptibility of the material poses significant fabrication challenges. A study of the effects of optical and mechanical effects of environmental humidity exposure are presented for the DNA-CTMA and SEO110 polymers used in the inverted ridge waveguide. While the soft, flexible nature of the DNA-CTMA is desirable for certain applications, this presents a challenge in producing a clean polished window for optical

  3. Mapping of psoralen cross-linked nucleotides in RNA.

    PubMed Central

    Garrett-Wheeler, E; Lockard, R E; Kumar, A

    1984-01-01

    A method is described for using the cross-linking reagent 4'-(hydroxy-methyl)-4,5',8-trimethylpsoralen (HMT) to map base paired regions and higher-order structure within RNA molecules. Applying this method to yeast tRNAPhe, we have specifically identified cross-links within the acceptor stem between U6 X U68, in the D-stem between C11 X C25, and in the T psi-stem between U50 X C63 and U52 X C63. We have also identified a unique cross-link between U8 X C48 which are trans pyrimidines in the core region due to tertiary interactions between U8:A14 and C48:G15. The precise point of cross-linking was deduced in every case by using purine-specific U2 ribonuclease along with cytidine-specific CL3 ribonuclease which will anomalously cleave after photoreversed pyrimidines. The ability to map the precise point of cross-linking should prove invaluable in identifying nucleotides in close proximity within the tertiary structure of other RNA molecules. Images PMID:6425802

  4. Effect of sterilization and crosslinking on gelatin films.

    PubMed

    Amadori, Sofia; Torricelli, Paola; Rubini, Katia; Fini, Milena; Panzavolta, Silvia; Bigi, Adriana

    2015-02-01

    Sterilization through γ-irradiation has been reported to affect collagen mechanical properties, but its possible effects on gelatin based materials have not been investigated up to now. Herein we report the results of a mechanical, chemical and thermal study performed on gelatin films before and after γ-irradiation. The investigation was performed on uncrosslinked films as well as on crosslinked films. To this aim, two common crosslinking agents, glutaraldehyde and genipin, at different concentration (0.15, 0.30 and 0.67%) were used. The results indicate that sterilization significantly affects the mechanical properties of uncrosslinked films, whereas it displays a modest effect on gelatin swelling, release in solution, thermal stability and molecular structure. Both glutaraldehyde and genipin enhance the mechanical properties and stability in solution of the gelatin films. In particular, the values of Young modulus increase as a function of crosslinker concentration up to about 10 and 18 MPa for genipin and glutaraldehyde treated samples respectively. The results of in vitro study demonstrate that the films crosslinked with genipin do not display any cytotoxic reaction, whereas glutaraldehyde crosslinking provokes an acute and dose dependent cytotoxic effect.

  5. Hyper-crosslinked cyclodextrin porous polymer: An efficient CO2 capturing material with tunable porosity

    DOE PAGES

    Meng, Bo; Li, Haiyang; East China Univ. of Science and Technology, Shanghai; ...

    2016-11-11

    We designed and synthesized the cyclodextrin (CD)-based hyper-crosslinked porous polymers (HCPPs) for selective CO2 adsorption and storage. We also explored the effect of monomer size on micropore formation, and determined a feasible way to tailor the porosity of the materials during the hyper-crosslinking process.

  6. Ice templated and cross-linked xylan/nanocrystalline cellulose hydrogels

    Treesearch

    Tobias Köhnke; Thomas Elder; Hans Theliander; Arthur J. Ragauskas

    2014-01-01

    Structured xylan-based hydrogels, reinforced with cellulose nanocrystals (CNCs), have successfully been prepared from water suspensions by cross-linking during freeze-casting. In order to induce cross-linking during the solidification/sublimation operation, xylan was first oxidized using sodium periodate to introduce dialdehydes. The oxidized xylan was then mixed with...

  7. Assessment of collagen crosslinking and denaturation for the design of regenerative scaffolds.

    PubMed

    Madaghiele, Marta; Calò, Emanuela; Salvatore, Luca; Bonfrate, Valentina; Pedone, Deborah; Frigione, Mariaenrica; Sannino, Alessandro

    2016-01-01

    Crosslinking and denaturation were two variables that deeply affected the performance of collagen-based scaffolds designed for tissue regeneration. If crosslinking enhances the mechanical properties and the enzymatic resistance of collagen, while masking or reducing the available cell binding sites, denaturation has very opposite effects, as it impairs the mechanical and the enzymatic stability of collagen, but increases the number of exposed cell adhesive domains. The quantification of both crosslinking and denaturation was thus fundamental to the design of collagen-based scaffolds for selected applications. The aim of this work was to investigate the extents of crosslinking and denaturation of collagen-based films upon dehydrothermal (DHT) treatment, that is, one of the most commonly employed methods for zero-length crosslinking that shows the unique ability to induce partial denaturation. Swelling measurements, differential scanning calorimetry, Fourier transform infrared spectroscopy, colorimetric assays for the quantification of primary amines, and mechanical tests were performed to analyze the effect of the DHT temperature on crosslinking and denaturation. In particular, chemically effective and elastically effective crosslink densities were evaluated. Both crosslinking and denaturation were found to increase with the DHT temperature, although according to different trends. The results also showed that DHT treatments performed at temperatures up to 120°C maintained the extent of denaturation under 25%. Coupling a mild DHT treatment with further crosslinking may thus be very useful not only to modulate the crosslink density, but also to induce a limited amount of denaturation, which shows potential to partially compensate the loss of cell binding sites caused by crosslinking.

  8. Mutants of Escherichia coli with Cold-Sensitive Deoxyribonucleic Acid Synthesis

    PubMed Central

    Waskell, Lucy; Glaser, Donald A.

    1974-01-01

    Ten cold-sensitive mutants defective in deoxyribonucleic acid (DNA) synthesis at 20 C have been identified among 218 cold-sensitive mutants isolated from a mutagenized population of Escherichia coli K-12. Four of the ten mutant alleles, dna-339 dna-340, dna-341, and dna-342, cotransduce with serB+ and hence may be dnaC mutants. Two of these, dna-340 and dna-341, are recessive to their wild-type allele. The gene product of their wild-type allele is trans acting. Complementation tests have demonstrated that dna-340 and dna-341 are in the same cistron. The mapping of the remaining six mutations is in progress. In an attempt to determine whether LW4 and LW21 were initiator mutants, cultures of these strains were starved of an essential amino acid at 37 C and then incubated at 15 C with the essential amino acid. The amount of DNA synthesis observed under these circumstances was insignificant. These data are consistent with the idea that LW4 and LW21 are initiator mutants. However, attempts to integratively suppress LW4 and LW21 with F′ factors were unsuccessful. To resolve the question of whether or not LW4 and LW21 are initiator mutants, more specific tests and criteria are required. Cultures of LW4 and LW21 were toluene treated and used to measure in vitro DNA synthesis. If the cells were incubated either at 15 or 20 C before toluene treatment, they were capable of markedly less DNA synthesis than if preincubation had not occurred. The amount of in vitro DNA synthesis is directly proportional to the amount of DNA synthesis occurring during preincubation in vivo; i.e., more DNA synthesis is observed at 20 than at 15 C. The fact that the cold-sensitive mutants are unable to synthesize DNA when supplied with deoxyribonucleoside triphosphates, DNA precursors, is evidence they are not defective in precursor synthesis. PMID:4597994

  9. Fate of Donor Deoxyribonucleic Acid in a Highly Transformation-Deficient Strain of Haemophilus influenzae

    PubMed Central

    Kooistra, Jan; Venema, Gerard

    1974-01-01

    A transformation-deficient strain of Haemophilus influenzae (efficiency of transformation 104-fold less than that of the wild type), designated TD24, was isolated by selection for sensitivity to mitomycin C. In its properties the mutant was equivalent to recA type mutants of Escherichia coli. The TD24 mutation was linked with the str-r marker (about 30%) and only weakly linked with the nov-r2.5 marker. The uptake of donor deoxyribonucleic acid (DNA) was normal in the TD24 strain, but no molecules with recombinant-type activity (molecules carrying both the donor and the resident marker) were formed. In the mutant the intracellular presynaptic fate of the donor DNA was the same as that in the transformation-proficient (wild-type) strain, and the radioactive label of the donor DNA associated covalently with the recipient chromosome in about the same quantity as in the wild type. However, many fewer donor atoms were associated with segments of the mutant's recipient chromosome as compared with segments of the wild-type chromosome. In the mutant the association was accompanied by complete loss of donor marker activity. The lack of donor marker activity of the donor-recipient complex of DNA isolated from the mutant was not due to lack of uptake of the complex by the second recipient and its inability to associate with the second recipient's chromosome. Because the number of donor-atom-carrying resident molecules was higher than could be accounted for by the lengths of presynaptic donor molecules, we favor the idea that the association of donor DNA atoms with the mutant chromosome results from local DNA synthesis rather than from dispersive integration of donor DNA by recombination. PMID:4546806

  10. Deoxyribonucleic acid modified poly(dimethylsiloxane) microfluidic channels for the enhancement of microchip electrophoresis.

    PubMed

    Liang, Ruping; Hu, Pengfei; Gan, Guihua; Qiu, Jianding

    2009-03-15

    In this paper, deoxyribonucleic acid (DNA) was employed to construct a functional film on the PDMS microfluidic channel surface and apply to perform electrophoresis coupled with electrochemical detection. The functional film was formed by sequentially immobilizing chitosan and DNA to the PDMS microfluidic channel surface using the layer-by-layer assembly. The polysaccharide backbone of chitosan can be strongly adsorbed onto the hydrophobic PDMS surface through electrostatic interaction in the acidic media, meanwhile, chitosan contains one protonatable functional moiety resulting in a strong electrostatic interactions between the surface amine group of chitosan and the charged phosphate backbone of DNA at low pH, which generates a hydrophilic microchannel surface and reveals perfect resistance to nonspecific adsorption of analytes. Aminophenol isomers (p-, o-, and m-aminophenol) served as a separation model to evaluate the effect of the functional PDMS microfluidic chips. The results clearly showed that these analytes were efficiently separated within 60s in a 3.7 cm long separation channel and successfully detected on the modified microchip coupled with in-channel amperometric detection mode at a single carbon fiber electrode. The theoretical plate numbers were 74,021, 92,658 and 60,552 Nm(-1) at the separation voltage of 900 V with the detection limits of 1.6, 4.7 and 2.5 microM (S/N=3) for p-, o-, and m-aminophenol, respectively. In addition, this report offered an effective means for preparing hydrophilic and biocompatible PDMS microchannel surface, which would facilitate the use of microfluidic devices for more widespread applications.

  11. Radiation crosslinking of polyamide 610

    NASA Astrophysics Data System (ADS)

    Feng, W.; Hu, F. M.; Yuan, L. H.; Zhou, Y.; Zhou, Y. Y.

    2002-03-01

    In the present paper the gel formation of polyamide 610 by γ-ray irradiation in the presence of polyfunctional monomer and γ-crystal nucleating agent under vacuum or air atmosphere had been studied. It was found that the gel formation was dependent on the content of polyfunctional monomer and nucleating agent. However, there was very little difference between gel contents irradiated under vacuum and air atmosphere. The results showed that the crosslinking by γ-irradiation enhanced the mechanical properties of PA610 especially at high temperature in the presence of polyfunctional monomer and γ-crystal nucleating agent. The mechanism of radiation crosslinking and scission was discussed according to the composition and quantity of gas released from three kinds of PA during irradiation.

  12. Laser Crosslink Subsystem - An overview

    NASA Astrophysics Data System (ADS)

    Deadrick, R. B.; Deckelman, W. F.

    1992-06-01

    The Laser Crosslink Subsystem (LCS) is a full duplex laser communications terminal in production at McDonnell Douglas Electronics Systems Company. The LCS will provide a data crosslink for geosynchronous satellites. This paper provides an overview of the system design and major elements followed by a brief program history. One LCS is installed on each satellite. The system utilizes a solid state diode pumped Neodymium YAG laser and direct pulse detection to provide 1.28 Mbps data transmission in one direction on the link and 4 Kbps in the other. A single eight inch gimballed telescope provides both the transmit and receive antenna function. After autonomously acquiring, the 200 Hz bandwidth fine tracking system maintains pointing of the 10 microrad optical beam. The LCS began development in 1981. Since then, each of its assemblies has completed-flight qualification testing. The first integrated production unit successfully completed environmental and performance qualification testing in 1990.

  13. Assembly of crosslinked oxo-cyanoruthenate and zirconium oxide bilayers: Application in electrocatalytic films based on organically modified silica with templated pores

    PubMed Central

    Rutkowska, Iwona A.; Sek, Jakub P.; Mehdi, B. Layla; Kulesza, Pawel J.; Cox, James A.

    2014-01-01

    Electrochemical deposition of crosslinked oxo-cyanoruthenate, Ru-O/CN-O, from a mixture of RuCl3 and K4Ru(CN)6 is known to yield a film on glassy carbon that promotes oxidations by a combination of electron and oxygen transfer. Layer-by-layer (LbL) deposition of this species and of a film formed by cycling of the electrode potential in a ZrO2 solution systematically increases the number of catalytically active sites of the Ru-O/CN-O on the electrode. The evaluation of the electrocatalytic activity was by cyclic voltammetric oxidation of cysteine at pH 2. Plots of the anodic peak current vs. the square root of scan rate were indicative of linear diffusion control of this oxidation, even in the absence of ZrO2, but the slopes of these linear plots increased with bilayer number, n, of (ZrO2 | Ru-O/CN-O)n. The latter observation is hypothesized to be due to an increased number of active sites for a given geometric electrode area, but proof required further study. To optimize utilization of the catalyst and to provide a size-exclusion characteristic to the electrode, the study was extended to LbL deposition of the composite in 50-nm pores of an organically modified silica film deposited by electrochemically assisted sol-gel processing using surface-bound poly(styrene sulfonate) nanospheres as a templating agent. PMID:24683266

  14. Materials based on carbon-filled porous layers of PVC cyclam derivatives cross-linked with the surfaces of asbestos fabric fibers

    NASA Astrophysics Data System (ADS)

    Tzivadze, A. Yu.; Fridman, A. Ya.; Morozova, E. M.; Sokolova, N. P.; Voloshchuk, A. M.; Petukhova, G. A.; Bardishev, I. I.; Gorbunov, A. M.; Novikov, A. K.; Polyakova, I. Ya.; Titova, V. N.; Yavich, A. A.; Petrova, N. V.

    2016-08-01

    The synthesis of bilayer materials with porous upper layers composed of PVC hydroxyethylcyclam derivatives filled with carbon and a layer consisting of hydroxyethylcyclam, cross-linked via Si-O-C groups with the silica chains of a developed surface of asbestos fabric, is described. The aza-crown groups in these materials are bound with aqua complexes of H2SO4 or NaOH. The structure of the materials is examined, their adsorption characteristics are determined, and the rate of motion of H+ or OH- ions in electrochemical bridges is measured, while the formation of H2 and O2 in their cathodic and anodic polarization is determined as a function of voltage. It is shown that the upper layer of these materials is adsorption-active and electronand H+- or OH-- conductive, while the bottom layer is only H+- or OH-- conductive; through it, the upper layer is supplied with the H+ or OH- ions needed for the regeneration of the aqua complexes broken down to H2 and O2 on carbon particles.

  15. Efficient ibuprofen delivery from anhydrous semisolid formulation based on a novel cross-linked silicone polymer network: an in vitro and in vivo study.

    PubMed

    Aliyar, Hyder; Huber, Robert; Loubert, Gary; Schalau, Gerald

    2014-07-01

    The use of silicone as a primary polymer in topical semisolid pharmaceutical formulations is infrequent. Recent development of novel silicone materials provides an opportunity to investigate their drug delivery efficiencies. In this study, an anhydrous semisolid formulation was prepared using a novel cross-linked silicone polymer network swollen in isododecane. Similar formulations were prepared using petrolatum, an acrylic, or a cellulose polymer. All formulations contained 5% ibuprofen (IBP). In vitro permeability was evaluated for all formulations and a commercial product using human cadaver epidermis. The silicone formulation delivered IBP more efficiently than all other formulations in terms of flux, cumulative amount, and percent drug release. The silicone formulation showed the maximum flux of 85.9 μg . cm(-2) . h(-1) and a cumulative IBP release of 261.6 μg in 8 h, whereas the benchmark showed 20.1 μg . cm(-2) . h(-1) and 30.9 μg, respectively. An in vivo study conducted on rats showed calculated blood AUCs of 59.2 and 17.6 μg . h/g (p < 0.003) for the silicone formulation and the benchmark, respectively. The IBP in excised rat skin was 264 ± 59 μg/g for the silicone formulation and 102 ± 5 μg/g for the benchmark. The results obtained from the in vitro and in vivo studies demonstrate efficient topical IBP delivery by the silicone formulation.

  16. "Near perfect" amphiphilic conetwork based on end-group cross-linking of polydimethylsiloxane triblock copolymer via atom transfer radical polymerization.

    PubMed

    Xu, Jianfeng; Qiu, Ming; Ma, Bomou; He, Chunju

    2014-09-10

    Novel amphiphilic conetworks (APCNs) with uniform channel size were synthesized through end-cross-linking of well-defined amphiphilic triblock copolymers via atom transfer radical polymerization (ATRP). A new ditelechelic polydimethylsiloxane macroinitiator was synthesized to initiate the polymerization of N,N-dimethylacrylamide. The resulting triblock copolymers show well-defined molecular weight with narrow polydisperisty, which are telechelic modified by allylamine and fully cross-linked with polyhydrosiloxanes through hydrosilylation. Transmission electron microscopy shows that the APCN has the behavior of microphase separation with small channel size and uniform phase domain. The resulting APCNs with idealized microstructure exhibit a combination of excellent properties, i.e., superhigh mechanical strength (4 ± 1 MPa) and elongation ratio (175 ± 25%), outstanding oxygen permeability (350 ± 150 barrers), a high water uptake property, and excellent biocompatibility, indicating that in this way, "near perfect" networks are obtained. These results are better than those reported in the literature, suggesting a promising semipermeable barrier for islet encapsulation in relative biomaterial fields.

  17. Sequence preferences of DNA interstrand crosslinking agents: quantitation of interstrand crosslink locations in DNA duplex fragments containing multiple crosslinkable sites.

    PubMed Central

    Millard, J T; Weidner, M F; Kirchner, J J; Ribeiro, S; Hopkins, P B

    1991-01-01

    A general approach to the quantitative study of the sequence specificity of DNA interstrand crosslinking agents in synthetic duplex DNA fragments is described. In the first step, a DNA fragment previously treated with an interstrand crosslinking agent is subjected to denaturing PAGE. Not only does this distinguish crosslinked from native or monoadducted DNA, it is shown herein that isomeric crosslinked DNAs differing in position of the crosslink can in some cases be separated. In the second stage, the now fractionated crosslinked DNAs isolated from denaturing PAGE are subjected to fragmentation using iron(II)/EDTA. For those fractions which are structurally homogeneous, analysis of the resulting fragment distribution has previously been shown to reveal the crosslink position at nucleotide resolution. It is shown herein that in fractions which are structurally heterogeneous due to differences in position of crosslink, this analysis quantifies the relative extent of crosslinking at distinct sites. Using this method it is shown that reductively activated mitomycin C crosslinks the duplex sequences 5'-GCGC and 5'-TCGA with 3 +/- 1:1 relative efficiency. Images PMID:1903204

  18. Bifunctional crosslinking ligands for transthyretin

    PubMed Central

    Mangione, P. Patrizia; Deroo, Stéphanie; Ellmerich, Stephan; Bellotti, Vittorio; Kolstoe, Simon; Wood, Stephen P.; Robinson, Carol V.; Smith, Martin D.; Tennent, Glenys A.; Broadbridge, Robert J.; Council, Claire E.; Thurston, Joanne R.; Steadman, Victoria A.; Vong, Antonio K.; Swain, Christopher J.; Pepys, Mark B.; Taylor, Graham W.

    2015-01-01

    Wild-type and variant forms of transthyretin (TTR), a normal plasma protein, are amyloidogenic and can be deposited in the tissues as amyloid fibrils causing acquired and hereditary systemic TTR amyloidosis, a debilitating and usually fatal disease. Reduction in the abundance of amyloid fibril precursor proteins arrests amyloid deposition and halts disease progression in all forms of amyloidosis including TTR type. Our previous demonstration that circulating serum amyloid P component (SAP) is efficiently depleted by administration of a specific small molecule ligand compound, that non-covalently crosslinks pairs of SAP molecules, suggested that TTR may be also amenable to this approach. We first confirmed that chemically crosslinked human TTR is rapidly cleared from the circulation in mice. In order to crosslink pairs of TTR molecules, promote their accelerated clearance and thus therapeutically deplete plasma TTR, we prepared a range of bivalent specific ligands for the thyroxine binding sites of TTR. Non-covalently bound human TTR–ligand complexes were formed that were stable in vitro and in vivo, but they were not cleared from the plasma of mice in vivo more rapidly than native uncomplexed TTR. Therapeutic depletion of circulating TTR will require additional mechanisms. PMID:26400472

  19. Metal Chelating Crosslinkers Form Nanogels with High Chelation Stability.

    PubMed

    Lux, Jacques; Chan, Minnie; Elst, Luce Vander; Schopf, Eric; Mahmoud, Enas; Laurent, Sophie; Almutairi, Adah

    2013-12-14

    We present a series of hydrogel nanoparticles (nanogels) incorporating either acyclic or cyclic metal chelates as crosslinkers. These crosslinkers are used to formulate polyacrylamide-based nanogels (diameter 50 to 85 nm) yielding contrast agents with enhanced relaxivities (up to 6-fold greater than Dotarem®), because this nanogel structure slows the chelator's tumbling frequency and allows fast water exchange. Importantly, these nanogels also stabilize Gd(3+) within the chelator thermodynamically and kinetically against metal displacement through transmetallation, which should reduce toxicity associated with release of free Gd(3+). This chelation stability suggests that the chelate crosslinker strategy may prove useful for other applications of metal-chelating nanoparticles in medicine, including other imaging modalities and radiotherapy.

  20. Metal Chelating Crosslinkers Form Nanogels with High Chelation Stability

    PubMed Central

    Elst, Luce Vander; Schopf, Eric; Mahmoud, Enas; Laurent, Sophie; Almutairi, Adah

    2013-01-01

    We present a series of hydrogel nanoparticles (nanogels) incorporating either acyclic or cyclic metal chelates as crosslinkers. These crosslinkers are used to formulate polyacrylamide-based nanogels (diameter 50 to 85 nm) yielding contrast agents with enhanced relaxivities (up to 6-fold greater than Dotarem®), because this nanogel structure slows the chelator's tumbling frequency and allows fast water exchange. Importantly, these nanogels also stabilize Gd3+ within the chelator thermodynamically and kinetically against metal displacement through transmetallation, which should reduce toxicity associated with release of free Gd3+. This chelation stability suggests that the chelate crosslinker strategy may prove useful for other applications of metal-chelating nanoparticles in medicine, including other imaging modalities and radiotherapy. PMID:24505553

  1. Enzymatically Crosslinked Emulsion Gels Using Star-Polymer Stabilizers.

    PubMed

    Ma, Kai; An, Zesheng

    2016-10-01

    A novel type of emulsion gel based on star-polymer-stabilized emulsions is highlighted, which contains discrete hydrophobic oil and hydrophilic aqueous solution domains. Well-defined phenol-functionalized core-crosslinked star polymers are synthesized via reversible addition-fragmentation chain transfer (RAFT)-mediated dispersion polymerization and are used as stabilizers for oil-in-water emulsions. Horseradish-peroxidase-catalyzed polymerization of the phenol moieties in the presence of H2 O2 enables rapid formation of crosslinked emulsion gels under mild conditions. The crosslinked emulsion gels exhibit enhanced mechanical strength, as well as widely tunable composition. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Actin cross-linkers and the shape of stereocilia.

    PubMed

    Lenz, Martin; Prost, Jacques; Joanny, Jean-François

    2010-10-20

    Stereocilia are actin-based cellular protrusions essential for hearing. We propose that they are shaped by the detachment dynamics of actin cross-linkers, in particular espin. We account for experimentally observed stereocilium shapes, treadmilling velocity to length relationship, espin 1 localization profile, and microvillus length to espin level relationship. If the cross-linkers are allowed to reattach, our model yields a dynamical phase transition toward unbounded growth. Considering the simplified case of a noninteracting, one-filament system, we calculate the length probability distribution in the growing phase and its stationary form in a continuum approximation of the finite-length phase. Numerical simulations of interacting filaments suggest an anomalous power-law divergence of the protrusion length at the growth transition, which could be a universal feature of cross-linked depolymerizing systems. Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. Instabilities in filament-motor solutions with crosslinkers.

    NASA Astrophysics Data System (ADS)

    Ziebert, Falko; Peter, Ronny; Zimmermann, Walter

    2007-03-01

    Filament-motor systems are in nonequilibrium due to the energy consumption during motor movement (via ATP hydrolysis), and thus display pattern and structure formation. We report on simple mesoscopic modeling based on conservation laws with active filament currents. We discuss instabilities in a recent experiment on actomyosin, where ATP is depleted in the presence of a small amount of crosslinker proteins. In the limit of high density of crosslinkers, we propose a model where transported filaments are coupled to an elastic crosslinked network, leading to oscillatory behavior. References: D. Smith, F. Ziebert, D. Humphrey, C. Duggan, W. Zimmermann and J. Kaes, submitted to Biophys. J. ; R. Peter, F. Ziebert and W. Zimmermann, submitted to Europhys. Lett.

  4. Crosslinking of polyamide-6 initiated by proton beam irradiation

    NASA Astrophysics Data System (ADS)

    Porubská, Mária; Szöllös, Ondrej; Janigová, Ivica; Jomová, Klaudia; Chodák, Ivan

    2017-04-01

    Initiation of crosslinking of polyamide-6 (PA6) by proton beam irradiation was investigated for a virgin material as well as for PA6 containing up to 5 wt% of triallyl cyanurate (TAC) as a crosslinking coagent. The gel point was found to be 144 and 40 kGy for virgin PA6 and for PA6 with 1 wt% of TAC, while for higher TAC content gel content was determined to be around zero absorbed dose. The ratio between crosslinking and scission of macroradicals formed by irradiation was found to be around 0.65 regardless on presence or absence of TAC and its concentration. The more detailed discussion on chemical processes as well as on final structure formation after irradiation is based on data from differential scanning calorimetry, detecting a decrease of both lamellar thickness and crystalline portion, but an increase of glass transition temperature.

  5. Constitutive models for rubber networks undergoing simultaneous crosslinking and scission.

    SciTech Connect

    Thompson, Aidan Patrick; Curro, John G.; Rottach, Dana R.; Grest, Gary Stephen; Budzien, Joanne L.; Lo, David Chi S.

    2006-01-01

    Constitutive models for chemically reacting networks are formulated based on a generalization of the independent network hypothesis. These models account for the coupling between chemical reaction and strain histories, and have been tested by comparison with microscopic molecular dynamics simulations. An essential feature of these models is the introduction of stress transfer functions that describe the interdependence between crosslinks formed and broken at various strains. Efforts are underway to implement these constitutive models into the finite element code Adagio. Preliminary results are shown that illustrate the effects of changing crosslinking and scission rates and history.

  6. The Importance of Non-accessible Crosslinks and Solvent Accessible Surface Distance in Modeling Proteins with Restraints From Crosslinking Mass Spectrometry.

    PubMed

    Matthew Allen Bullock, Joshua; Schwab, Jannik; Thalassinos, Konstantinos; Topf, Maya

    2016-07-01

    Crosslinking mass spectrometry (XL-MS) is becoming an increasingly popular technique for modeling protein monomers and complexes. The distance restraints garnered from these experiments can be used alone or as part of an integrative modeling approach, incorporating data from many sources. However, modeling practices are varied and the difference in their usefulness is not clear. Here, we develop a new scoring procedure for models based on crosslink data-Matched and Nonaccessible Crosslink score (MNXL). We compare its performance with that of other commonly-used scoring functions (Number of Violations and Sum of Violation Distances) on a benchmark of 14 protein domains, each with 300 corresponding models (at various levels of quality) and associated, previously published, experimental crosslinks (XLdb). The distances between crosslinked lysines are calculated either as Euclidean distances or Solvent Accessible Surface Distances (SASD) using a newly-developed method (Jwalk). MNXL takes into account whether a crosslink is nonaccessible, i.e. an experimentally observed crosslink has no corresponding SASD in a model due to buried lysines. This metric alone is shown to have a significant impact on modeling performance and is a concept that is not considered at present if only Euclidean distances are used. Additionally, a comparison between modeling with SASD or Euclidean distance shows that SASD is superior, even when factoring out the effect of the nonaccessible crosslinks. Our benchmarking also shows that MNXL outperforms the other tested scoring functions in terms of precision and correlation to Cα-RMSD from the crystal structure. We finally test the MNXL at different levels of crosslink recovery (i.e. the percentage of crosslinks experimentally observed out of all theoretical ones) and set a target recovery of ∼20% after which the performance plateaus.

  7. Initiation of Deoxyribonucleic Acid Replication in Germinating Spores of Bacillus subtilis 168 Carrying the dnaB(Ts)134 Mutation

    PubMed Central

    Callister, Heather; Mesurier, Sue Le; Wake, R. G.

    1977-01-01

    The nature of the deoxyribonucleic acid synthesis reported by others to occur at 45°C in germinating spores of the temperature-sensitive deoxyribonucleic acid initiation mutant of Bacillus subtilis 168, TsB134, has been investigated. Density transfer experiments, using 5-bromouracil, show that a normal round of replication can occur in a significant fraction of the spore population under such conditions. No repair synthesis is detectable. The possibility raised by this finding, that initiation of the first round of replication during spore outgrowth is unique in that its initiation is determined prior to germination, has been investigated by comparing the behavior of germinating spores of isogenic strains of B. subtilis 168, one carrying and the other without the dnaB (Ts)134 mutation. It is shown that deoxyribonucleic acid synthesis in the Ts strain is very sensitive to temperature in the vicinity of 45°C. At a slightly higher temperature, 49°C, initiation of the first round of replication in the Ts strain is completely (greater than 96%) blocked, but it proceeds normally in the Ts+ strain. Thus, it is concluded that, after the germination of a spore, the action of the dnaB134 gene product is an obligatory requirement for initiation of the first round of replication. The initiation of replication that can occur in spores of the original TsB134 strain germinating at 45°C is presumably due to incomplete inactivation of the dnaB134 gene product under such conditions. PMID:405369

  8. The Role of Inclusion Binding Contributions for β-Cyclodextrin Polymers Cross-Linked with Divinyl Sulfone?--A Comment on Morales-Sanfrutos et al. Entitled "Divinyl Sulfone Cross-Linked Cyclodextrin-Based Polymeric Materials: Synthesis and Applications as Sorbents and Encapsulating Agents", Molecules, 2015, 20, 3565-3581.

    PubMed

    Wilson, Lee D; Mohamed, Mohamed H; McMartin, Dena W

    2016-01-14

    This commentary reports on a recent scientific study reported in this journal (cf. Molecules 2015, 20(3), 3565-3581). Some key scientific issues that require further explanation and clarification in the former article are as follows: (i) the relationship between the inclusion site accessibility and the level of cross-linking employed are brought into question for the case of α-CD and β-CD cross-linked adsorbent materials; (ii) the binding affinity of the CD/guest complexes were not related to the isotherm parameters for the CD-polymer/guest systems; (iii) the limited molecular level structural characterization of the cross-linked polymer materials; and (iv) the interpretation of the adsorption isotherm results by the authors.

  9. Determination of protein conformation by isotopically labelled cross-linking and dedicated software

    NASA Astrophysics Data System (ADS)

    Nielsen, Tina; Thaysen-Andersen, Morten; Larsen, Nanna; Jørgensen, Flemming S.; Houen, Gunnar; Højrup, Peter

    2007-12-01

    Chemical cross-linking in conjunction with mass spectrometry (MS) can be used for sensitive and rapid investigation of the three-dimensional structure of proteins at low resolution. However, the resulting data are very complex, and on the bioinformatic side, there still exists an urgent need for improving computer software for (semi-) automated cross-linking data analysis. In this study, we have developed dedicated software for rapid and confident identification and validation of cross-linked species using an isotopic labelled cross-linker approach in combination with MS. Deuterated (+4 Da) and non-deuterated (+0 Da) bis(sulfosuccinimidyl)suberate, BS3, was used as homobifunctional cross-linker to tag the cross-linked regions. Peptides generated from proteolysis were separated using high performance liquid chromatography, and peptide mass fingerprinting was obtained for the individual fractions using matrix-assisted laser-desorption ionisation time-of-flight (MALDI TOF) MS. The resulting peptide mass lists were combined and transferred to the program, ProteinXXX, which generated the theoretical mass values of all combinations of cross-linked peptides and dead-end cross-links and compared this to the obtained mass lists. In addition, screening for 4 Da-separated signals aided the identification of potential cross-linked species. Sequence information of these candidates was then obtained using MALDI TOF TOF. The cross-linked peptides could then be validated based on the match of the fragmentation pattern and the theoretical values produced by ProteinXXX. This semi-automated interpretation provided a high analysis speed of cross-linking data, with efficient and confident identification of cross-linked species. Four experiments using different conditions showed a high degree of reproducibility as only 1 and 2 cross-links out of 36 identified was not observed in two experiments. The method was tested using human placenta calreticulin (CRT). Based on the identified cross-links

  10. Calcium-requiring step in the uptake of deoxyribonucleic acid molecules through the surface of competent pneumococci.

    PubMed Central

    Seto, H; Tomasz, A

    1976-01-01

    The conversion of surface-adsorbed deoxyribonucleic acid (DNA) molecules to a state in which they are inaccessible to exogenous deoxyribonuclease requires specifically calcium ions; magnesium ions cannot replace calcium ions. Virtually maximal levels of nuclease-resistant DNA binding and genetic transformation can be obtained in media free from magnesium and containing only calcium ions. It is suggested that the calcium-requiring process is the transport of DNA molecules across the plasma membrane. Magnesium ions stimulate both the loss of surface-adsorbed DNA to the medium and the extracellular degradation of DNA. PMID:7544

  11. Mapping of colicin E2 and colicin E3 plasmid deoxyribonucleic acid EcoR-1-sensitive sites.

    PubMed

    Inselburg, J; Johns, V

    1975-01-01

    Colicin plasmids E2 and E3 (Col E2 and Col E3) deoxyribonucleic acid (DNA) has been shown to contain, respectively, two and three EcoR1 restriction endonuclease-sensitive sites. This was determined by measuring the DNA fragments generated after EcoR1 endonuclease treatment by agarose gel electrophoresis and electron microscopy. The structure of heteroduplex Col E2-col E3 DNA molecules formed from EcoR1-generated fragments permitted a localization of the EcoR1-sensitive sites on the plasmid chromosomes.

  12. Isolation and Characterization of a Mutant of Salmonella typhimurium Deficient in a Major Deoxyribonucleic Acid Polymerase Activity

    PubMed Central

    Whitfield, Harvey J.; Levine, Gary

    1973-01-01

    A mutant of Salmonella typhimurium strain LT2 that is deficient in a major deoxyribonucleic acid (DNA) polymerase activity has been isolated and characterized. This mutant resembles the pol mutants of E. coli in that it has low DNA polymerase activity and it is sensitive to methyl methane sulfonate as well as ultraviolet irradiation. Revertants selected for methyl methane sulfonate resistance are no longer sensitive to ultraviolet irradiation and contain normal DNA polymerase levels. No direct role in replication can be ascribed to this polymerase activity since cells grow well in its absence. In addition, the LT2 plasmid has been shown to exist in the mutant strain. PMID:4355486

  13. Mitigating crosslinking reactions through preconversion strategies

    SciTech Connect

    Not Available

    1992-03-01

    The ultimate goal of this research is to develop preconversion techniques that will mitigate crosslinking reactions and thereby substantially increase liquid yields during subsequent liquefaction. The immediate objective is to explore the effect of several pretreatments on the evolution of oxygen functions, crosslinking, and conversion in laboratory studies. The pretreatments to be explored include several that hold promise for effecting deoxygenation or other reduction, for example, treatment with CO/water/base and hydroquinones, either alone or in conjunction. The effects of these pretreatments on functional group distribution, macromoleculer structure, and liquefaction will be compared with those that have shown promise in the past for improved conversions, such as simple hydrothermal pretreatment, mild hydrogenation with dispersed catalysts, and demineralization. A second objective is to develop suitable test procedures for assessing the effect of the pretreatment on subsequent liquefaction and achieve also an understanding the chemical origin of the effect. These test procedures will include the use of proton magnetic resonance thermal analysis (PMRTA) for determining the effect of pretreatment on fluidity as liquefaction conditions (temperature, pressure) are approached. They will also involve the use of simpler and more pertinent laboratory measures of volatile product yields following the batch liquefactions that will be run to test the susceptibility of pretreated coals to subsequent liquefaction.

  14. A Two-Dimensional Deoxyribonucleic Acid (DNA) Matrix Based Biomolecular Computing and Memory Architecture

    DTIC Science & Technology

    2009-02-01

    decoded. On the aqueous side, binding proteins specific to each modification are used to selectively isolate DNA fragments and this selectivity is...used to do computation. As there are millions of molecules with corresponding binding proteins , this approach has the potential to yield unlimited...are used to selectively isolate DNA fragments by binding proteins specific to the label of interest. An implementation strategy for using these

  15. Order-Disorder Transitions in Cross-Linked Block Copolymer Solids

    SciTech Connect

    Das, J.

    2005-01-12

    With a view toward creating solid block copolymers wherein the order-disorder transition can be accessed many times they investigated the nature of order-disorder transitions in cross-linked diblock copolymer melts using synergistic theory and experiment. A mean-field theory based on a coarse grained free-energy and the Random Phase Approximation (RPA) is developed for the system of interest. The quenched distribution of cross-links is averaged using the replica method. The phase behavior of a particular A-B block copolymer melt with a randomly cross-linked B-Block is determined as a function of the Florry-Huggins interaction parameter ({chi}) and the average number of cross-links per chain N{sub c}. They find for a cross-link density greater than N*{sub c} the B monomers are localized within a region of size {zeta} {approx} (N{sub c} - N*{sub c}){sup -1/2}. The cross-links strongly oppose ordering in the system as {zeta} becomes comparable to the radius of gyration of the block copolymer chain. As such the order-disorder transition temperature T{sub ODT} decreases precipitously when N{sub c} > N*{sub c}. When N{sub c} < N*{sub c}, T{sub ODT} increases weakly with N{sub c}. Experiments were conducted on cross-linked polystyrene-block-polyisoprene copolymer samples wherein the polyisoprene block was selectively cross-linked at a temperature well above the order-disorder transition temperature of the pure block copolymer. Small angle X-ray scattering (SAXS) and birefringence measurements on the cross-linked samples are consistent with the theoretical prediction. T{sub ODT} decreases rapidly when the cross-linking density exceeds the critical cross-linking density.

  16. Thymineless Death in Escherichia coli: Deoxyribonucleic Acid Replication and the Immune State

    PubMed Central

    Cummings, Donald J.; Kusy, Alvin R.

    1970-01-01

    Thymineless death (TLD) and nalidixic acid (NA) inactivation were studied in multiple auxotrophic strains of Escherichia coli B and B/r. As expected, it was found that both E. coli B and B/r exhibited an “immune state,” i.e., a fraction of the population survived inactivation to both TLD and NA. With glucose as a carbon source in minimal medium, 0.1 to 0.3% of strain B and 0.2 to 0.5% of strain B/r survived inactivation; with acetate as the carbon source, the surviving fractions were increased to 1 to 2% and 5 to 7%, respectively. These immune fractions could be increased in magnitude by preincubation in minimal media containing thymine. Systematic analysis of the particular supplements necessary for the immune state indicated that the absence of the required amino acids was essential for the maximal expression of immunity. However, immunity was not abolished in acetate medium even in the presence of the required supplements. Further studies on the replication of deoxyribonucleic acid (DNA) during preincubation indicated that the degree of immunity did not necessarily correlate with the completion of a round of DNA replication. This finding was supported by examining the immune state in synchronous populations. In both glucose and acetate medium, there was no significant change in the degree of immunity to inactivation within the cell cycles of E. coli B and B/r. We concluded that some other event, possibly inhibition of protein synthesis, was necessary in determining the degree of the immune state. DNA replication was investigated after TLD and NA inactivation, and, as expected, it was found that both events led to premature initiation of replication. The only differences observed in the effects of these two processes on DNA synthesis were the following. (i) NA-induced replication was less sensitive to chloramphenicol than was TLD. (ii) TLD-induced replication was unaffected by pretreatment of the cells with mitomycin C, but this pretreatment prevented the

  17. Identification of a Herbal Powder by Deoxyribonucleic Acid Barcoding and Structural Analyses

    PubMed Central

    Sheth, Bhavisha P.; Thaker, Vrinda S.

    2015-01-01

    Background: Authentic identification of plants is essential for exploiting their medicinal properties as well as to stop the adulteration and malpractices with the trade of the same. Objective: To identify a herbal powder obtained from a herbalist in the local vicinity of Rajkot, Gujarat, using deoxyribonucleic acid (DNA) barcoding and molecular tools. Materials and Methods: The DNA was extracted from a herbal powder and selected Cassia species, followed by the polymerase chain reaction (PCR) and sequencing of the rbcL barcode locus. Thereafter the sequences were subjected to National Center for Biotechnology Information (NCBI) basic local alignment search tool (BLAST) analysis, followed by the protein three-dimension structure determination of the rbcL protein from the herbal powder and Cassia species namely Cassia fistula, Cassia tora and Cassia javanica (sequences obtained in the present study), Cassia Roxburghii, and Cassia abbreviata (sequences retrieved from Genbank). Further, the multiple and pairwise structural alignment were carried out in order to identify the herbal powder. Results: The nucleotide sequences obtained from the selected species of Cassia were submitted to Genbank (Accession No. JX141397, JX141405, JX141420). The NCBI BLAST analysis of the rbcL protein from the herbal powder showed an equal sequence similarity (with reference to different parameters like E value, maximum identity, total score, query coverage) to C. javanica and C. roxburghii. In order to solve the ambiguities of the BLAST result, a protein structural approach was implemented. The protein homology models obtained in the present study were submitted to the protein model database (PM0079748-PM0079753). The pairwise structural alignment of the herbal powder (as template) and C. javanica and C. roxburghii (as targets individually) revealed a close similarity of the herbal powder with C. javanica. Conclusion: A strategy as used here, incorporating the integrated use of DNA

  18. Identification of a Herbal Powder by Deoxyribonucleic Acid Barcoding and Structural Analyses.

    PubMed

    Sheth, Bhavisha P; Thaker, Vrinda S

    2015-10-01

    Authentic identification of plants is essential for exploiting their medicinal properties as well as to stop the adulteration and malpractices with the trade of the same. To identify a herbal powder obtained from a herbalist in the local vicinity of Rajkot, Gujarat, using deoxyribonucleic acid (DNA) barcoding and molecular tools. The DNA was extracted from a herbal powder and selected Cassia species, followed by the polymerase chain reaction (PCR) and sequencing of the rbcL barcode locus. Thereafter the sequences were subjected to National Center for Biotechnology Information (NCBI) basic local alignment search tool (BLAST) analysis, followed by the protein three-dimension structure determination of the rbcL protein from the herbal powder and Cassia species namely Cassia fistula, Cassia tora and Cassia javanica (sequences obtained in the present study), Cassia Roxburghii, and Cassia abbreviata (sequences retrieved from Genbank). Further, the multiple and pairwise structural alignment were carried out in order to identify the herbal powder. The nucleotide sequences obtained from the selected species of Cassia were submitted to Genbank (Accession No. JX141397, JX141405, JX141420). The NCBI BLAST analysis of the rbcL protein from the herbal powder showed an equal sequence similarity (with reference to different parameters like E value, maximum identity, total score, query coverage) to C. javanica and C. roxburghii. In order to solve the ambiguities of the BLAST result, a protein structural approach was implemented. The protein homology models obtained in the present study were submitted to the protein model database (PM0079748-PM0079753). The pairwise structural alignment of the herbal powder (as template) and C. javanica and C. roxburghii (as targets individually) revealed a close similarity of the herbal powder with C. javanica. A strategy as used here, incorporating the integrated use of DNA barcoding and protein structural analyses could be adopted, as a novel

  19. Dually cross-linked single network poly(acrylic acid) hydrogels with superior mechanical properties and water absorbency.

    PubMed

    Zhong, Ming; Liu, Yi-Tao; Liu, Xiao-Ying; Shi, Fu-Kuan; Zhang, Li-Qin; Zhu, Mei-Fang; Xie, Xu-Ming

    2016-06-28

    Poly(acrylic acid) (PAA) hydrogels with superior mechanical properties, based on a single network structure with dual cross-linking, are prepared by one-pot free radical polymerization. The network structure of the PAA hydrogels is composed of dual cross-linking: a dynamic and reversible ionic cross-linking among the PAA chains enabled by Fe(3+) ions, and a sparse covalent cross-linking enabled by a covalent cross-linker (Bis). Under deformation, the covalently cross-linked PAA chains remain intact to maintain their original configuration, while the Fe(3+)-enabled ionic cross-linking among the PAA chains is broken to dissipate energy and then recombined. It is found that the mechanical properties of the PAA hydrogels are significantly influenced by the contents of covalent cross-linkers, Fe(3+) ions and water, which can be adjusted within a substantial range and thus broaden the applications of the hydrogels. Meanwhile, the PAA hydrogels have excellent recoverability based on the dynamic and reversible ionic cross-linking enabled by Fe(3+) ions. Moreover, the swelling capacity of the PAA hydrogels is as high as 1800 times in deionized water due to the synergistic effects of ionic and covalent cross-linkings. The combination of balanced mechanical properties, efficient recoverability, high swelling capacity and facile preparation provides a new method to obtain high-performance hydrogels.

  20. Viscoelastic behavior of polymers undergoing crosslinking reactions.

    NASA Technical Reports Server (NTRS)

    Moacanin, J.; Aklonis, J. J.

    1971-01-01

    Previously a method was developed for predicting the viscoelastic response of polymers undergoing scission reactions. These results are now extended to include crosslinking reactions. As for scission, at any given time the character of the network chains is determined by the instantaneous crosslink density. For scission all chains were assumed to carry the same stress; for crosslinking, however, the stress is distributed between the 'new' and 'old' chains. Equations for calculating the creep response of a system which experiences a step increase in crosslink density are derived.

  1. Rubber Elasticity in Highly Crosslinked Polyesters.

    DTIC Science & Technology

    Esters, *Polymers, *Elastic properties, Rubber, Propylene glycol , Maleic acid, Anhydrides, Phthalic acids, Mechanical properties, Molecular structure, Crosslinking(Chemistry), Polymerization, Styrenes, Temperature, Transition temperature, Molecular weight

  2. High data rate optical crosslinks

    NASA Astrophysics Data System (ADS)

    Boroson, Don M.; Bondurant, Roy S.

    1992-03-01

    Optical technologies, due to their extremely short wavelengths, can be designed to be much more compact than RF when addressing high data rate crosslinks and multiple apertures approaching the multi-Gbps operational range. Currently available optical technologies can furnish hundreds-of- Mbps in a package of less than 100 lbs and several cubic feet. Attention is presently given to communications and spatial acquisition/tracking system analysis, the character of such space-qualified optics hardware as the requisite laser transmitter, and advanced hardware prototypes.

  3. The chemical protecting group concept applied in crosslinking of natural tissues with glutaraldehyde acetals.

    PubMed

    Goissis, G; Yoshioka, S A; Braile, D M; Ramirez, V D

    1998-03-01

    This work describes the results of the controlled crosslinking of collagen matrices by glutaraldehyde based on a double protection strategy, glutaraldehyde acetals and lysine protonation due to the acidic conditions of acetal formation. Materials crosslinked by this approach were characterized by thermal stability comparable to those obtained by conventional procedures with mechanical properties expected for bioprosthesis manufacture and with a higher stability toward collagenase hydrolysis. The integrity of the microfibrillar structure was confirmed by optical and scanning electronic microscopy. The results indicate that the glutaraldehyde acetals procedure may be of potential use for the crosslinking of bovine pericardium used in the manufacture of bioprosthetic devices. Advantages may be related to the production of materials with homogeneous crosslinking distributions, associated with better definition in the nature of the chemical link that they introduce, due to a better distribution of glutaraldehyde within the tissue matrix before the crosslinking reaction is allowed to occur. As a result, materials with improved biological and mechanical properties are expected.

  4. Association of mitochondrial deoxyribonucleic acid mutation with polymorphism in CYP2E1 gene in oral carcinogenesis

    PubMed Central

    Pandey, Rahul; Mehrotra, Divya; Catapano, Carlo; Choubey, Vimal; Sarin, Rajiv; Mahdi, Abbas Ali; Singh, Stuti

    2012-01-01

    Background Oral carcinogenesis is a complex process affected by genetic as well as environmental factors. CYP2E1 gene is involved in metabolism of number of compounds and carcinogens. Its normal functioning is required for homeostasis of free radical. Mitochondrial deoxyribonucleic acid (mtDNA) is 10–100 times more susceptible to damage than nuclear DNA. Mitochondrial DNA large scale deletions are well documented in oral cancer. However, the relationship between CYP2E1 gene polymorphisms and mtDNA damage is still not documented in literature. Materials and Methods Case–control study involving 50 subjects was carried out. Deoxyribonucleic acid extraction was done from study subject tissue samples. Restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR) amplification was done to confirm CYP2E1 gene polymorphisms. The PCR amplification was done for mtDNA 4977 bp deletion. Statistical analysis was carried out using SPSS version 11.5 with χ2 tests. Results c1c1 and DD polymorphisms are prevalent in North Indian population having oral cancer. These polymorphisms are significantly associated with mtDNA 4977 bp deletion. Conclusion Mitochondrial DNA damage induced by wild CYP2E1 forms and imperfect DNA repair in mtDNA may act synergistically to greatly enhance oral cancer risk. PMID:25756024

  5. Suppression of lex Mutations Affecting Deoxyribonucleic Acid Repair in Escherichia coli K-12 by Closely Linked Thermosensitive Mutations

    PubMed Central

    Mount, David W.; Walker, Anita C.; Kosel, C.

    1973-01-01

    A major class of ultraviolet (UV)-resistant derivatives of lex− strains of Escherichia coli K-12 grows normally at 30 C but at 42.5 C fails to produce colonies on complete or minimal agar. At 42.5 C these thermosensitive strains form filaments without septa, due to an apparent defect in cell division. Deoxyribonucleic acid degradation in UV-irradiated cultures of the thermosensitive strains is slow, in contrast to the rapid degradation in UV-irradiated cultures of the parental lex− strains. The thermosensitive mutations (tsl) are tightly linked (less than 0.04 min on the E. coli K-12 linkage map) to the site of the lex mutation in the parental strain and could lie within the same gene. The tsl+/tsl− heterozygotes grow at 42.5 C and are UV resistant when grown at 30 or 42.5 C. The tsl mutations are, therefore, recessive in contrast to lex mutations, which are dominant. It appears likely that the tsl mutations alter the diffusible product that gives rise to the Lex− mutant phenotype. This product appears to be necessary for deoxyribonucleic acid repair and cell division. PMID:4583257

  6. Proteome-wide profiling of protein assemblies by cross-linking mass spectrometry.

    PubMed

    Liu, Fan; Rijkers, Dirk T S; Post, Harm; Heck, Albert J R

    2015-12-01

    We describe an integrated workflow that robustly identifies cross-links from endogenous protein complexes in human cellular lysates. Our approach is based on the application of mass spectrometry (MS)-cleavable cross-linkers, sequential collision-induced dissociation (CID)-tandem MS (MS/MS) and electron-transfer dissociation (ETD)-MS/MS acquisitions, and a dedicated search engine, XlinkX, which allows rapid cross-link identification against a complete human proteome database. This approach allowed us to detect 2,179 unique cross-links (1,665 intraprotein cross-links at a 5% false discovery rate (FDR) and 514 interprotein cross-links at 1% FDR) in HeLa cell lysates. We validated the confidence of our cross-linking results by using a target-decoy strategy and mapping the observed cross-link distances onto existing high-resolution structures. Our data provided new structural information about many protein assemblies and captured dynamic interactions of the ribosome in contact with different elongation factors.

  7. Crosslinking of Chitosan with Dialdehyde Derivatives of Nucleosides and Nucleotides. Mechanism and Comparison with Glutaraldehyde.

    PubMed

    Mikhailov, Sergey N; Zakharova, Alexandra N; Drenichev, Mikhail S; Ershov, Andrey V; Kasatkina, Mariya A; Vladimirov, Leonid V; Novikov, Valentin V; Kildeeva, Natalia R

    2016-01-01

    In medical and pharmaceutical applications, chitosan is used as a component of hydrogels-macromolecular networks swollen in water. Chemical hydrogels are formed by covalent links between the crosslinking reagents and amino functionalities of chitosan. To date, the most commonly used chitosan crosslinkers are dialdehydes, such as glutaraldehyde (GA). We have developed novel GA like crosslinkers with additional functional groups-dialdehyde derivatives of uridine (oUrd) and nucleotides (oUMP and oAMP)-leading to chitosan-based biomaterials with new properties. The process of chitosan crosslinking was investigated in details and compared to crosslinking with GA. The rates of crosslinking with oUMP, oAMP, and GA were essentially the same, though much higher than in the case of oUrd. The remarkable difference in the crosslinking properties of nucleoside and nucleotide dialdehydes can be clearly attributed to the presence of the phosphate group in nucleotides that participates in the gelation process through ionic interactions with the amino groups of chitosan. Using NMR spectroscopy, we have not observed the formation of aldimine bonds. It can be concluded that the real number of crosslinks needed to cause gelation of chitosan chains may be less than 1%.

  8. Flexural properties of crosslinked and oligomer-modified glass-fibre reinforced acrylic bone cement.

    PubMed

    Puska, Mervi A; Närhi, Timo O; Aho, Allan J; Yli-Urpo, Antti; Vallittu, Pekka K

    2004-09-01

    The flexural properties of oligomer-modified bone cement with various quantities of crosslinking monomer with or without glass fibre reinforcement were studied. The flexural strength and modulus of acrylic bone cement-based test specimens (N=6), including crosslinked and oligomer-modified structures with or without glass fibres, were measured in dry conditions and after immersion in simulated body fluid (SBF) for seven days (analysis with ANOVA). One test specimen from the acrylic bone cement group containing 30 wt % crosslinking monomer of its total monomer content was examined with scanning electron microscope (SEM) to evaluate signs of the semi-interpenetrating polymer network (semi-IPN). The highest dry mean flexural strength (130 MPa) was achieved with the bone cement/crosslinking monomer/glass fibre combination containing 5 wt % crosslinking monomer of its monomer content. The highest flexural modulus (11.5 GPa) was achieved with the bone cement/crosslinking monomer/glass fibre combination containing 30 wt % crosslinking monomer of its monomer content. SBF storage decreased the flexural properties of the test specimens, as did the addition of the oligomer filler. Nevertheless, the addition of crosslinking monomer and chopped glass fibres improves considerably the mechanical properties of oligomer-modified (i.e. porosity-producing filler containing) acrylic bone cement. In addition, some signs of the semi-IPN structure were observed by SEM examination.

  9. Visible Light Crosslinking of Methacrylated Hyaluronan Hydrogels for Injectable Tissue Repair

    PubMed Central

    Fenn, Spencer L.; Oldinski, Rachael A.

    2015-01-01

    Tissue engineering hydrogels are primarily cured in situ using ultraviolet (UV) radiation which limits the use of hydrogels as drug or cell carriers. Visible green light activated crosslinking systems are presented as a safe alternative to UV photocrosslinked hydrogels, without compromising material properties such as viscosity and stiffness. The objective of this study was to fabricate and characterize photocrosslinked hydrogels with well-regulated gelation kinetics and mechanical properties for the repair or replacement of soft tissue. An anhydrous methacrylation of hyaluronan (HA) was performed to control the degree of modification (DOM) of HA, verified by 1H-NMR spectroscopy. UV activated crosslinking was compared to visible green light activated crosslinking. While the different photocrosslinking techniques resulted in varied crosslinking times, comparable mechanical properties of UV and green light activated crosslinked hydrogels were achieved using each photocrosslinking method by adjusting time of light exposure. Methacrylated HA (HA-MA) hydrogels of varying molecular weight, DOM and concentration exhibited compressive moduli ranging from 1 kPa to 116 kPa, for UV crosslinking, and 3 kPa to 146 kPa, for green light crosslinking. HA-MA molecular weight and concentration were found to significantly influence moduli values. HA-MA hydrogels did not exhibit any significant cytotoxic affects towards human mesenchymal stem cells. Green light activated crosslinking systems are presented as a viable method to form natural-based hydrogels in situ. PMID:26097172

  10. Analytical characterisation of glutardialdehyde cross-linking products in gelatine-gum arabic complex coacervates.

    PubMed

    Fuguet, Elisabet; van Platerink, Chris; Janssen, Hans-Gerd

    2007-11-26

    Encapsulates having shells of cross-linked mixtures of proteins and polysaccharides are widely used in the food and pharmaceutical industry for controlled release of actives and flavour compounds. In order to be able to predict the behaviour and the release characteristics of the microcapsules, a better understanding of the nature and extent of the cross-linking reaction is needed. Several analytical techniques were applied for the characterisation of glutardialdehyde (GDA) cross-linked encapsulates made of gelatine and gum arabic. To allow the use of sensitive, high-resolution methods such as chromatography and mass spectrometry, the sample first had to be hydrolysed. In this way, a mixture of amino acids, small peptides and the cross-link moieties was obtained. High-resolution liquid chromatography coupled to high-resolution mass spectrometry (HPLC-MS) was applied to detect possible cross-link markers through a comparison of HPLC-MS mass-chromatograms obtained for cross-linked and non-cross-linked coacervates. HPLC-MS/MS was used to identify the species responsible for the differences. Cross-linking occurred between GDA molecules and lysine and hydroxylysine epsilon-amino groups, and up to eight cross-link products of different nature could be identified. They included pyridinium ions and Schiff bases, and also unreacted GDA condensation products. Next, based on the insight gained in the possible chemical structures present in the cross-link markers, methods for selective labelling of these functionalities were employed to allow easier detection of related reaction products. Both liquid chromatography (LC) and gas chromatography (GC) were used in these experiments. Unfortunately, these approaches failed to detect new cross-link markers, most likely as a result of the low levels at which these are present.

  11. Review stapling peptides using cysteine crosslinking.

    PubMed

    Fairlie, David P; Dantas de Araujo, Aline

    2016-11-01

    Stapled peptides are an emerging class of cyclic peptide molecules with enhanced biophysical properties such as conformational and proteolytic stability, cellular uptake and elevated binding affinity and specificity for their biological targets. Among the limited number of chemistries available for their synthesis, the cysteine-based stapling strategy has received considerable development in the last few years driven by facile access from cysteine-functionalized peptide precursors. Here we present some recent advances in peptide and protein stapling where the side-chains of cysteine residues are covalently connected with a range of different crosslinkers affording bisthioether macrocyclic peptides of varying topology and biophysical properties. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 843-852, 2016.

  12. Mechanisms of DNA-protein crosslink repair.

    PubMed

    Stingele, Julian; Bellelli, Roberto; Boulton, Simon J

    2017-09-01

    Covalent DNA-protein crosslinks (DPCs, also known as protein adducts) of topoisomerases and other proteins with DNA are highly toxic DNA lesions. Of note, chemical agents that induce DPCs include widely used classes of chemotherapeutics. Their bulkiness blocks virtually every chromatin-based process and makes them intractable for repair by canonical repair pathways. Distinct DPC repair pathways employ unique points of attack and are crucial for the maintenance of genome stability. Tyrosyl-DNA phosphodiesterases (TDPs) directly hydrolyse the covalent linkage between protein and DNA. The MRE11-RAD50-NBS1 (MRN) nuclease complex targets the DNA component of DPCs, excising the fragment affected by the lesion, whereas proteases of the spartan (SPRTN)/weak suppressor of SMT3 protein 1 (Wss1) family target the protein component. Loss of these pathways renders cells sensitive to DPC-inducing chemotherapeutics, and DPC repair pathways are thus attractive targets for combination cancer therapy.

  13. Crosslinked polyimide electro-optic materials

    NASA Astrophysics Data System (ADS)

    Kowalczyk, T. C.; Kosc, T. Z.; Singer, K. D.; Beuhler, A. J.; Wargowski, D. A.; Cahill, P. A.; Seager, C. H.; Meinhardt, M. B.; Ermer, S.

    1995-11-01

    We report studies of the optical and electro-optic properties of guest-host polymeric nonlinear optical materials based on aromatic, fluorinated, fully imidized, organic soluble, thermally, and photochemically crosslinkable, guest-host polyimides. We have introduced temperature stable nonlinear optical chromophores into these polyimides and studied optical losses, electric field poling, electro-optic properties, and orientational stability. We measured electro-optic coefficients of 5.5 and 12.0 pm/V for ((2,6-Bis(2-(3-(9-(ethyl)carbazolyl))ethenyl)4H-pyran-4-ylidene)propanedinitrile (4-(Dicyanomethylene)-2-methyl-6-(p -dimethylaminostyryl)-4H-pyran) DCM-doped guest-host systems at 800 nm using a poling field of 1.3 MV/cm. Poling induced nonlinearities in single-layer films were in agreement with the oriented gas model, but were lower in three-layer films due to voltage division across the layers.

  14. Study of continuously mixed crosslinked fracturing fluids with a recirculating flow-loop viscometer

    SciTech Connect

    Harris, P.C.; Harms, W.M.; Norman, L.R. )

    1989-11-01

    Continuously mixed gel fracturing fluids were successfully prepared with polymer slurries of guar, derivatized guar, and derivatized cellulose. The authors describe the rheological behavior of the continuously mixed fluids measured on a recirculating flow-loop viscometer over a temperature range of 80 to 300{sup 0}F (27 to 149{sup 0}C). Rapid and complete base-gel hydration required proper pH control and high mixing energy. Oil-based polymer slurries allowed rapid hydration rates sufficient to achieve performance from a crosslinked fluid prepared during a completely continuous operation. Water-based polymer slurries required a short holding period for complete hydration. Delayed-crosslink-gel viscosity was influenced by shear rate and the degree of base-gel hydration. Chemical factors influencing viscosity development included base-gel concentration, crosslinking-agent concentration, fluid pH, and ionic strength. Hydration time and pH requirements may differ for specific polymer/crosslinker pairs.

  15. DNA-Based Chiral Composites with Enhancement of Chirooptic and NLO Effects for NIMS Applications

    DTIC Science & Technology

    2008-11-24

    A. Miniewicz, A. Kochalska, J. Mysliwiec, A. Samoc, M. Samoc, and J. G. Grote, Deoxyribonucleic acid-based photochromic material for fast dynamic holography, Appl. Phys. Lett. 91, 041118-1/041118-3 (2007).

  16. Chemical crosslinking and mass spectrometry studies of the structure and dynamics of membrane proteins and receptors.

    SciTech Connect

    Haskins, William E.; Leavell, Michael D.; Lane, Pamela; Jacobsen, Richard B.; Hong, Joohee; Ayson, Marites J.; Wood, Nichole L.; Schoeniger, Joseph S.; Kruppa, Gary Hermann; Sale, Kenneth L.; Young, Malin M.; Novak, Petr

    2005-03-01

    Membrane proteins make up a diverse and important subset of proteins for which structural information is limited. In this study, chemical cross-linking and mass spectrometry were used to explore the structure of the G-protein-coupled photoreceptor bovine rhodopsin in the dark-state conformation. All experiments were performed in rod outer segment membranes using amino acid 'handles' in the native protein sequence and thus minimizing perturbations to the native protein structure. Cysteine and lysine residues were covalently cross-linked using commercially available reagents with a range of linker arm lengths. Following chemical digestion of cross-linked protein, cross-linked peptides were identified by accurate mass measurement using liquid chromatography-fourier transform mass spectrometry and an automated data analysis pipeline. Assignments were confirmed and, if necessary, resolved, by tandem MS. The relative reactivity of lysine residues participating in cross-links was evaluated by labeling with NHS-esters. A distinct pattern of cross-link formation within the C-terminal domain, and between loop I and the C-terminal domain, emerged. Theoretical distances based on cross-linking were compared to inter-atomic distances determined from the energy-minimized X-ray crystal structure and Monte Carlo conformational search procedures. In general, the observed cross-links can be explained by re-positioning participating side-chains without significantly altering backbone structure. One exception, between C3 16 and K325, requires backbone motion to bring the reactive atoms into sufficient proximity for cross-linking. Evidence from other studies suggests that residues around K325 for a region of high backbone mobility. These findings show that cross-linking studies can provide insight into the structural dynamics of membrane proteins in their native environment.

  17. Oil-in-water emulsions stabilized by tyrosinase-crosslinked potato protein.

    PubMed

    Glusac, Jovana; Isaschar-Ovdat, Sivan; Kukavica, Biljana; Fishman, Ayelet

    2017-10-01

    Potato protein (PP) holds great promise as a non-allergenic food ingredient with high nutritional value. Attempts to modulate its functional properties by crosslinking have not been reported to date. The effect of tyrosinase-mediated crosslinking of PP on the properties of o/w emulsions was studied in the present work. Among the various PPs, protease inhibitors were efficiently crosslinked by the enzyme as determined by SDS-PAGE analysis. Concentrated emulsions comprising 40% olive oil and 6.1% PP (w/w) were fabricated by a shear stress homogenizer. The PP-stabilized emulsions were evaluated after one and 4h of incubation with tyrosinase. Emulsions were characterized by their droplet size distribution, rheological behavior, creaming resistance and microstructure. The crosslinked emulsion had a self-standing elastic gel-like structure after 1h of incubation. Unlike the Newtonian non-crosslinked emulsion, the crosslinked emulsion exhibited a shear-thinning behavior with a 20-fold increase in viscosity. The longer incubation time coupled with shaking at 250rpm for up to 4h resulted in the disruption of the droplets structure and led to a 2-fold decrease in viscosity, compared to the 1-hour crosslinked emulsion. Droplet size distribution showed formation of large particles in the crosslinked emulsion. Microscopy imaging demonstrated formation of aggregated and dense emulsion droplets network, which also contributed to the emulsion gel-like behavior. In the case of the non-crosslinked emulsion, severe flocculation and coalescence was observed, regardless of incubation time. The results suggest that tyrosinase crosslinking is a useful method to modulate the properties of PP-based food formulations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Processing and characterization of benzocyclobutene (BCB)-functionalized thermally crosslinkable copolymers

    NASA Astrophysics Data System (ADS)

    Jiang, Tao

    The objective of this research has been to examine the processing, microstructure and physical properties of benzocyclobutene (BCB) functionalized copolymers. The approach was based on incorporating XTA, a BCB modified derivative of terephthalic acid, into the polymer backbone and then inducing crosslinking by heat treatment after the polymer has been formed into various shapes. The primary focus of the work was to investigate aromatic polyamides (aramids) such as poly(p-phenylene terephthalamide) (PPTA or Kevlarsp°ler) and poly(m-phenylene isophthalamide) (MPDI or Nomexsp°ler). It was anticipated that crosslinking would increase the inter-chain interactions between PPTA molecules and thus improve its compressive strength as well as other properties including creep, solvent resistance and flame resistance. PPTA-co-XTA copolymers exhibited lyotropic nematic liquid crystalline behavior. Highly oriented fibers were obtained using dry-jet wet spinning techniques, and they could be crosslinked via heat treatment between 320 and 420sp°C. Crosslinked fibers possessed higher tensile modulus than their as-spun counterparts. However, for high XTA-content materials, the tensile strength and toughness tended to decrease with increasing extent of heat treatment, which was attributed to degradative chain scission. MPDI-co-XTA copolymers were processed from isotropic solutions. The thermally crosslinkable copolymers demonstrated improved solvent resistance and dimensional stability at elevated temperatures. Crosslinking led to increased tensile modulus and decreased toughness and elongation at break. Molecular modeling established that with low XTA content the overall structure of MPDI-co-XTA copolymers was mostly unchanged from that of the neat MPDI and that the incorporated XTA unit introduced only local perturbations. Spectroscopic studies suggested that BCB crosslinked predominantly via stilbene junctions. Free radicals were found to form after crosslinking and might cause

  19. Polyimide Aerogels Using Triisocyanate as Cross-linker.

    PubMed

    Nguyen, Baochau N; Meador, Mary Ann B; Scheiman, Daniel; McCorkle, Linda

    2017-08-16

    A family of polyimide (PI)-based aerogels is produced using Desmodur N3300A, an inexpensive triisocyanate, as the cross-linker. The aerogels are prepared by cross-linking amine end-capped polyimide oligomers with the triisocyanate. The polyimide oligomers are formulated using 2,2'-dimethylbenzidine, 4,4'-oxydianiline, or mixtures of both diamines, combined with 3,3',4,4'-biphenyltetracarboxylic dianhydride, and are chemically imidized at room temperature. Depending on the backbone chemistry, chain length, and polymer concentration, density of the aerogels ranged from 0.06 to 0.14 g/cm(3) and Brunauer-Emmett-Teller surface areas ranged from 350 to 600 m(2)/g. Compressive moduli of these aerogels were as high as 225 MPa, which are comparable to, or higher than, those previously reported prepared with similar backbone structures but with other cross-linkers. Because of their lower cost and commercial availability as cross-linker, the aerogels may have further potential as insulation for building and construction, clothing, sporting goods, and automotive applications, although lower-temperature stability may limit their use in some aerospace applications.

  20. Cholesterol Removal from Whole Egg by Crosslinked β-Cyclodextrin

    PubMed Central

    Jeong, H. J.; Sun, H.; Chogsom, C.; Kwak, H. S.

    2014-01-01

    This study was carried out to optimize cholesterol removal in whole egg using crosslinked β-cyclodextrin (β-CD) and to recycle the β-CD. Various factors for optimizing conditions were concentration of the β-CD, mixing temperature, mixing time, mixing speed and centrifugal speed. In the result of this study, the optimum conditions of cholesterol removal were 25% crosslinked β-CD, 40°C mixing temperature, 30 min mixing time, 1,200 rpm mixing speed and 2,810×g centrifugal speed. The recycling was repeated five times. The cholesterol removal was 92.76% when treated with the optimum conditions. After determining the optimum conditions, the recyclable yields of the crosslinked β-CD ranged from 86.66% to 87.60% in the recycling and the percentage of cholesterol removal was over 80% until third recycling. However, the cholesterol removal efficiency was decreased when the number of repeated recycling was increased. Based on the result of this study, it was concluded that the crosslinked β-CD was efficient for cholesterol removal in whole egg, and recycling is possible for only limited repeating times due to the interaction of the β-CD and egg protein. PMID:25049985

  1. Phosphate uptake studies of cross-linked chitosan bead materials.

    PubMed

    Mahaninia, Mohammad H; Wilson, Lee D

    2017-01-01

    A systematic experimental study is reported that provides a molecular based understanding of cross-linked chitosan beads and their adsorption properties in aqueous solution containing phosphate dianion (HPO4(2-)) species. Synthetically modified chitosan using epichlorohydrin and glutaraldehyde cross-linkers result in surface modified beads with variable hydrophile-lipophile character and tunable HPO4(2-) uptake properties. The kinetic and thermodynamic adsorption properties of cross-linked chitosan beads with HPO4(2-) species were studied in aqueous solution. Complementary structure and physicochemical characterization of chitosan beads via potentiometry, Raman spectroscopy, DSC, and dye adsorption measurements was carried out to establish structure-property relationships. The maximum uptake (Qm) of bead systems with HPO4(2-) at equilibrium was 52.1mgg(-1); whereas, kinetic uptake results for chitosan bead/phosphate systems are relatively rapid (0.111-0.113min(-1)) with an intraparticle diffusion rate-limiting step. The adsorption process follows a multi-step pathway involving inner- and outer-sphere complexes with significant changes in hydration. Phosphate uptake strongly depends on the composition and type of cross-linker used for preparation of chitosan beads. The adsorption isotherms and structural characterization of bead systems illustrate the role of surface charge, hydrophile-lipophile balance, adsorption site accessibility, and hydration properties of the chitosan bead surface. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Two wavelength femtosecond laser induced DNA-protein crosslinking.

    PubMed Central

    Russmann, C; Stollhof, J; Weiss, C; Beigang, R; Beato, M

    1998-01-01

    Nucleic acid-protein interactions are essential for storage, reproduction and expression of genetic information. Biochemical methods, such as dimethyl sulfate genomic footprinting, have been developed to study stable protein-DNA interactions in vivo and chemical crosslinking has been used for less stable interactions, but the chemical agents are slow, damage cells and perturb native equilibria. To avoid these perturbations, UV laser crosslinking offers an alternative, although the energies required for significant crosslinking cause extensive DNA damage. We find that a combination of femtosecond laser pulses at two different wavelengths, in the UV and the visible range, increases the crosslinking efficiency while minimizing DNA damage. This technique also allowed us to directly measure the singlet S1lifetime of native DNA (tauS1 = 3.2 +/- 0.2 ps), which is mainly determined by the lifetime of thymine [tauS1 = 2.8 +/- 0.4 ps for (dT)16], the photochemically most reactive base. Our results suggest that two wavelength femtosecond laser pulses are well suited for the identification of transcription factors interacting with defined sequences and for studying the kinetics of protein-nucleic acid interactions in intact cells. PMID:9705506

  3. Modular enzymatically crosslinked protein polymer hydrogels for in situ gelation

    PubMed Central

    Davis, Nicolynn E.; Ding, Sheng; Forster, Ryan; Pinkas, Daniel M.; Barron, Annelise E.

    2012-01-01

    Biomaterials that mimic the extracellular matrix in both modularity and crosslinking chemistry have the potential to recapitulate the instructive signals that ultimately control cell fate. Toward this goal, modular protein polymer-based hydrogels were created through genetic engineering and enzymatic crosslinking. Animal derived tissue transglutaminase (tTG) and recombinant human transglutaminase (hTG) enzymes were used for coupling two classes of protein polymers containing either lysine or glutamine, which have the recognition substrates for enzymatic crosslinking, evenly spaced along the protein backbone. Utilizing tTG under physiological conditions, crosslinking occurred within two minutes, as determined by particle tracking microrheology. Hydrogel composition impacted the elastic storage modulus of the gel over 4-fold and also influenced microstructure and degree of swelling, but did not appreciably effect degradation by plasmin. Mouse 3T3 and primary human fibroblasts were cultured in both 2- and 3-dimensions without a decrease in cell viability and displayed spreading in 2D. The properties of these gels, which are controlled through the specific nature of the protein polymer precursors, render these gels valuable for in situ therapies. Furthermore, the modular hydrogel composition allows tailoring of mechanical and physical properties for specific tissue engineering applications. PMID:20609472

  4. SAXS Study of Reversibly Crosslinked Isotactic Polypropylene/clay Nanocomposites

    SciTech Connect

    Bouhelal, S.; Cagiao, M; Benachour, D; Djellouli, B; Rong, L; Hsiao, B; Baltá-Calleja, F

    2010-01-01

    A new route based on reversibly crosslinking reactive extrusion is applied for the development of iPP/clay nanocomposites. Analysis of small-angle X-ray scattering (SAXS) reflections of isotactic polypropylene (iPP)/clay nanocomposites, prepared by two different mixing and chemical crosslinking methods (i.e., conventional and in situ), is presented and results are compared with preceding wide-angle X-ray diffraction (WAXD) results. It is shown that the presence of clay significantly affects the value of long spacing in iPP, as well as the coherence length of lamellar stacks. Results show that the size of the coherently diffracting nanodomains decreases in two stages, first rapidly and then slowly as a function of increasing clay content. This can be attributed to the influence of confined iPP lamellae under the effect of rising number of clay particles. The appearance of the {gamma}-crystalline form in the crosslinked iPP/clay nanocomposites is related with the difficulty in chain folding of iPP chains introduced by the chemical crosslinking process, as well as by the presence of clay particles.

  5. Crosslinking Evidence for Motional Constraints within Chemoreceptor Trimers of Dimers

    PubMed Central

    Massazza, Diego A.; Parkinson, John S.; Studdert, Claudia A.

    2011-01-01

    Chemotactic behavior in bacteria relies on the sensing ability of large chemoreceptor clusters that are usually located at the cell pole. In E. coli, chemoreceptors show higher order interactions within those clusters based on a trimer-of-dimers organization. This architecture is conserved in a variety of other bacteria and archaea, implying that receptors in many microorganisms form trimer of dimer signaling teams. To gain further insight into the assembly and dynamic behavior of receptor trimers of dimers, we used in vivo crosslinking targeted to cysteine residues at various positions that define six different levels along the cytoplasmic signaling domains of the aspartate and serine chemoreceptors, Tar and Tsr. We found that the cytoplasmic domains of these receptors are close to each other near the trimer contact region at the cytoplasmic tip and lie farther apart as the receptor dimers approach the cytoplasmic membrane. Tar and Tsr reporter sites within the same or closely adjacent levels readily formed mixed crosslinks, whereas reporters lying at different distances from the tip did not. These findings indicate that there are no significant vertical displacements of one dimer with respect to the others within the trimer unit. Attractant stimuli had no discernable effect on the crosslinking efficiency of any of the reporters tested, but a strong osmotic stimulus reproducibly enhanced crosslinking at most of the reporter sites, indicating that individual dimers may move closer together under this condition. PMID:21174433

  6. Electron beam crosslinking of non-lead PVC formulations

    NASA Astrophysics Data System (ADS)

    Castañeda Facio, A.; Benavides, R.; Martínez Pardo, M. E.; Uribe, R.

    2007-11-01

    PVC samples with lead-free and lead-base stabilizer, containing TMPTMA (trimethylolpropane trimethacrylate) as a crosslinker and DOP (2-ethylhexyl phthalate) as a plasticizer, were electron beam treated at different doses (2-200 kGy) and characterized to evaluate crosslinking and other several properties, as a continuation of our previously reported paper, where these PVC formulations, typical for wire and cable applications, underwent gamma irradiation. The PVC was formulated with two different stabilizing systems: Ca/Zn and dibasic lead phthalate for comparison, to use them as jackets for a 22 wire gage (AWG). Small samples of the jacketed wires were irradiated in an industrial Dynamitron electron accelerator for the corresponding doses, along with two dosimetric systems: radiochromic thin film and alanine pellets dosimeters. The maximum dose applied was decided as the crosslinking increased, until the gel content was stable. The dose of 200 kGy was the condition for the highest crosslinking, so most of the wire was irradiated at such dose. Chemical and mechanical evaluations were carried out to the irradiated wire. The results show that 200 kGy was too high dose for the materials, since an important degradation is observed for the Ca/Zn systems. Unfortunately, such dose affects basically to CaZn formulations, which showed much poorer performance than classical lead-containing compositions. The results also indicate that gel content is not the best way of deciding the optimum condition for irradiation.

  7. Potential Effects of Corneal Cross-Linking upon the Limbus

    PubMed Central

    2016-01-01

    Corneal cross-linking is nowadays the most used strategy for the treatment of keratoconus and recently it has been exploited for an increasing number of different corneal pathologies, from other ectatic disorders to keratitis. The safety of this technique has been widely assessed, but clinical complications still occur. The potential effects of cross-linking treatment upon the limbus are incompletely understood; it is important therefore to investigate the effect of UV exposure upon the limbal niche, particularly as UV is known to be mutagenic to cellular DNA and the limbus is where ocular surface tumors can develop. The risk of early induction of ocular surface cancer is undoubtedly rare and has to date not been published other than in one case after cross-linking. Nevertheless it is important to further assess, understand, and reduce where possible any potential risk. The aim of this review is to summarize all the reported cases of a pathological consequence for the limbal cells, possibly induced by cross-linking UV exposure, the studies done in vitro or ex vivo, the theoretical bases for the risks due to UV exposure, and which aspects of the clinical treatment may produce higher risk, along with what possible mechanisms could be utilized to protect the limbus and the delicate stem cells present within it. PMID:27689081

  8. New crosslinkers for electrospun chitosan fibre mats. I. Chemical analysis.

    PubMed

    Austero, Marjorie S; Donius, Amalie E; Wegst, Ulrike G K; Schauer, Caroline L

    2012-10-07

    Chitosan (CS), the deacetylated form of chitin, the second most abundant, natural polysaccharide, is attractive for applications in the biomedical field because of its biocompatibility and resorption rates, which are higher than chitin. Crosslinking improves chemical and mechanical stability of CS. Here, we report the successful utilization of a new set of crosslinkers for electrospun CS. Genipin, hexamethylene-1,6-diaminocarboxysulphonate (HDACS) and epichlorohydrin (ECH) have not been previously explored for crosslinking of electrospun CS. In this first part of a two-part publication, we report the morphology, determined by field emission scanning electron microscopy (FESEM), and chemical interactions, determined by Fourier transform infrared microscopy, respectively. FESEM revealed that CS could successfully be electrospun from trifluoroacetic acid with genipin, HDACS and ECH added to the solution. Diameters were 267 ± 199 nm, 644 ± 359 nm and 896 ± 435 nm for CS-genipin, CS-HDACS and CS-ECH, respectively. Short- (15 min) and long-term (72 h) dissolution tests (T(600)) were performed in acidic, neutral and basic pHs (3, 7 and 12). Post-spinning activation by heat and base to enhance crosslinking of CS-HDACS and CS-ECH decreased the fibre diameters and improved the stability. In the second part of this publication, we report the mechanical properties of the fibres.

  9. New crosslinkers for electrospun chitosan fibre mats. I. Chemical analysis

    PubMed Central

    Austero, Marjorie S.; Donius, Amalie E.; Wegst, Ulrike G. K.; Schauer, Caroline L.

    2012-01-01

    Chitosan (CS), the deacetylated form of chitin, the second most abundant, natural polysaccharide, is attractive for applications in the biomedical field because of its biocompatibility and resorption rates, which are higher than chitin. Crosslinking improves chemical and mechanical stability of CS. Here, we report the successful utilization of a new set of crosslinkers for electrospun CS. Genipin, hexamethylene-1,6-diaminocarboxysulphonate (HDACS) and epichlorohydrin (ECH) have not been previously explored for crosslinking of electrospun CS. In this first part of a two-part publication, we report the morphology, determined by field emission scanning electron microscopy (FESEM), and chemical interactions, determined by Fourier transform infrared microscopy, respectively. FESEM revealed that CS could successfully be electrospun from trifluoroacetic acid with genipin, HDACS and ECH added to the solution. Diameters were 267 ± 199 nm, 644 ± 359 nm and 896 ± 435 nm for CS–genipin, CS–HDACS and CS–ECH, respectively. Short- (15 min) and long-term (72 h) dissolution tests (T600) were performed in acidic, neutral and basic pHs (3, 7 and 12). Post-spinning activation by heat and base to enhance crosslinking of CS–HDACS and CS–ECH decreased the fibre diameters and improved the stability. In the second part of this publication, we report the mechanical properties of the fibres. PMID:22628209

  10. Ionic liquid crosslinkers for chiral imprinted nanoGUMBOS.

    PubMed

    Hamdan, Suzana; Moore, Leonard; Lejeune, Jason; Hasan, Farhana; Carlisle, Trevor K; Bara, Jason E; Gin, D L; LaFrate, Andrew L; Noble, R D; Spivak, David A; Warner, Isiah M

    2016-02-01

    Molecularly imprinted polymers (MIPs) are an important class of selective materials for molecular specific sensors and separations. Molecular imprinting using non-covalent interactions in aqueous conditions still remains a difficult challenge due to interruption of hydrogen-bonding or electrostatic interactions water. Newly developed crosslinking ionic liquids are demonstrated herein to overcome problems of synthesizing aqueous MIPs, adding to previous examples of ionic liquids used as monomers in non-aqueous conditions or used as MIP solvents. Vinylimidazole ionic liquid crosslinkers were synthesized and subsequently explored as matrix supports for fabrication of molecularly imprinted polymeric nanoGUMBOS (nanoparticles derived from a group of uniform materials based on organic salts). Each of the four crosslinkers incorporated a unique functional spacer between the vinylimidazole groups, and the