These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Localized drugs delivery hydroxyapatite microspheres for osteoporosis therapy  

NASA Astrophysics Data System (ADS)

This study describes the preparation of hydroxyapatite microspheres for local drugs delivery. The formation of the hydroxyapatite microspheres was initiated by enzymatic decomposition of urea and accomplished by emulsification process (water-in-oil). The microspheres obtained were sintered at 500°C. Scanning electron microscope (SEM) indicated that the microspheres have various porous with random size, which maximizes the surface area. Cytotoxicity was not observed after sintering. Osteoporosis drugs, alendronate and BMP-2, were loaded into HAp microspheres and the releases of both molecules showed sustained releasing profiles.

Lee, J. H.; Ko, I. H.; Jeon, S.-H.; Chae, J. H.; Lee, E. J.; Chang, J. H.

2011-10-01

2

Evaluation of hydroxyapatite microspheres made from a borate glass to separate protein mixtures  

Microsoft Academic Search

A hydroxyapatite (HA, Ca10(PO4)6(OH)2), transformed from a calcium-containing borate glass, has been investigated for its protein adsorption and chromatographic\\u000a characteristics. Microspheres of the borate glass were transformed into HA by reacting them with a 0.25 M phosphate (K2HPO4) solution for 24 h at 37 °C (pH 9.0). The HA microspheres with a diameter of 45–90 ?m were hand packed into a steel column\\u000a (4.6 mm × 80 mm)

Xue Han; Ming Du; Yinfa Ma; Delbert E. Day

2008-01-01

3

Evaluation of BSA protein release from hollow hydroxyapatite microspheres into PEG hydrogel  

PubMed Central

Implants that simultaneously function as an osteoconductive matrix and as a device for local drug or growth factor delivery could provide an attractive system for bone regeneration. In our previous work, we prepared hollow hydroxyapatite (abbreviated HA) microspheres with a high surface area, mesoporous shell wall and studied the release of a model protein, bovine serum albumin (BSA), from the microspheres into phosphate-buffered saline (PBS). The present work is an extension of our previous work to study the release of BSA from similar HA microspheres into a biocompatible hydrogel, poly(ethylene glycol) (PEG). BSA-loaded HA microspheres were placed in a PEG solution which was rapidly gelled using ultraviolet radiation. The BSA release rate into the PEG hydrogel, measured using a spectrophotometric method, was slower than into PBS, and it was dependent on the initial BSA loading and on the microstructure of the microsphere shell wall. A total of 35–40% of the BSA initially loaded into the microspheres was released into PEG over ~14 days. The results indicate that these hollow HA microspheres have promising potential as an osteoconductive device for local drug or growth factor delivery in bone regeneration and in the treatment of bone diseases. PMID:23498254

Fu, Hailuo; Rahaman, Mohamed N.; Brown, Roger F.; Day, Delbert E.

2013-01-01

4

Hollow hydroxyapatite microspheres as a device for controlled delivery of proteins  

PubMed Central

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of Li2O–CaO–B2O3 glass (106–150 ?m) in K2HPO4 solution, and evaluated as a controlled delivery device for a model protein, bovine serum albumin (BSA). Reaction of the glass microspheres for 2 days in 0.02 M K2HPO4 solution (pH = 9) at 37°C resulted in the formation of biocompatible HA microspheres with a hollow core diameter equal to 0.6 the external diameter, high surface area (~100 m2/g), and a mesoporous shell wall (pore size ?13 nm). After loading with a solution of BSA in phosphate-buffered saline (PBS) (5 mg BSA/ml), the release kinetics of BSA from the HA microspheres into a PBS medium were measured using a micro bicinchoninic acid (BCA) protein assay. Release of BSA initially increased linearly with time, but almost ceased after 24–48 h. Modification of the BSA release kinetics was achieved by modifying the microstructure of the as-prepared HA microspheres using a controlled heat treatment (1–24 h at 600–900°C). Sustained release of BSA was achieved over 7–14 days from HA microspheres heated for 5 h at 600°C. The amount of BSA released at a given time was dependent on the concentration of BSA initially loaded into the HA microspheres. These hollow HA microspheres could provide a novel inorganic device for controlled local delivery of proteins and drugs. PMID:21290170

Fu, Hailuo; Day, Delbert E.; Brown, Roger F.

2011-01-01

5

Preparation of Hydroxyapatite Coating on the Surface of Hollow Glass Microspheres Using a Biomimetic Process  

NASA Astrophysics Data System (ADS)

Microcarrier culture technology has attached more attention, especially for scale-up cell culture in the filed of tissue engineering. The present work introduces a microcarrier with hydroxyapatite (HA) on hollow glass microsphere. Hollow glass microspheres with a main composition of SiO2 (55-65 wt.%), Al2O3 (26-35 wt.%), were pretreated by NaOH, on which hydroxyapatite coating was deposited by biomimetic process. The phase composition and morphology were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscope, field emission scanning electron microscope (FE-SEM) and high resolution transmission electron microscope (HRTEM), respectively. The results showed that after immersion for 15 days in 1.5 SBF, the uniform and dense HA coating was formed and it has porous surface and low crystallinity.

Jiao, Yan; Yang, Hai-Ying; Zhang, Ying-Long; Duan, Rong-Shuai; Lu, Yu-Peng

2014-07-01

6

Preparation of hollow hydroxyapatite microspheres by the conversion of borate glass at near room temperature  

SciTech Connect

Hollow hydroxyapatite microspheres, consisting of a hollow core and a porous shell, were prepared by converting Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres in dilute phosphate solution at 37 {sup o}C. The results confirmed that Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass was transformed to hydroxyapatite without changing the external shape and dimension of the original glass object. Scanning electron microscopy images showed the shell wall of the microsphere was built from hydroxyapatite particles, and these particles spontaneously align with one another to form a porous sphere with an interior cavity. Increase in phosphate concentration resulted in an increase in the reaction rate, which in turn had an effect on shell wall structure of the hollow hydroxyapatite microsphere. For the Li{sub 2}O-CaO-B{sub 2}O{sub 3} glass microspheres reacted in low-concentration K{sub 2}HPO{sub 4} solution, lower reaction rate and a multilayered microstructure were observed. On the other hand, the glass microspheres reacted in higher phosphate solution converted more rapidly and produced a single hydroxyapatite layer. Furthermore, the mechanism of forming hydroxyapatite hollow microsphere was described.

Yao, Aihua, E-mail: aihyao@126.com [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)] [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China); Ai, Fanrong; Liu, Xin; Wang, Deping; Huang, Wenhai; Xu, Wei [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)] [Institute of Bioengineering and Information Technology Materials, School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)

2010-01-15

7

Hollow hydroxyapatite microspheres: a novel bioactive and osteoconductive carrier for controlled release of bone morphogenetic protein-2 in bone regeneration.  

PubMed

The regeneration of large bone defects is a common and significant clinical problem. Limitations associated with existing treatments such as autologous bone grafts and allografts have increased the need for synthetic bone graft substitutes. The objective of this study was to evaluate the capacity of novel hollow hydroxyapatite (HA) microspheres to serve as a carrier for controlled release of bone morphogenetic-2 (BMP2) in bone regeneration. Hollow HA microspheres (106-150 ?m) with a high surface area (>100 m2 g(-1)) and a mesoporous shell wall (pore size 10-20 nm) were created using a glass conversion technique. The release of BMP2 from the microspheres into a medium composed of diluted fetal bovine serum in vitro was slow, but it occurred continuously for over 2 weeks. When implanted in rat calvarial defects for 3 or 6 weeks, the microspheres loaded with BMP2 (1 ?g per defect) showed a significantly better capacity to regenerate bone than those without BMP2. The amount of new bone in the defects implanted with the BMP2-loaded microspheres was 40% and 43%, respectively, at 3 and 6 weeks, compared to 13% and 17%, respectively, for the microspheres without BMP2. Coating the BMP2-loaded microspheres with a biodegradable polymer, poly(lactic-co-glycolic acid), reduced the amount of BMP2 released in vitro and, above a certain coating thickness, significantly reduced bone regeneration in vivo. The results indicate that these hollow HA microspheres could provide a bioactive and osteoconductive carrier for growth factors in bone regeneration. PMID:23747325

Xiao, Wei; Fu, Hailuo; Rahaman, Mohamed N; Liu, Yonxing; Bal, B Sonny

2013-09-01

8

5-Fluorouracil encapsulated HA/PLGA composite microspheres for cancer therapy.  

PubMed

5-Fluorouracil (5FU) was successfully entrapped within poly(lactide-co-glycolide) (PLGA) and hydroyapatite (HA) composite microspheres using the emulsification/solvent extraction technique. The effects of HA to PLGA ratio, solvent ratio as well as polymer inherent viscosity (IV) on encapsulation efficiency were investigated. The degradation and drug release rates of the microspheres were studied for 5 weeks in vitro in phosphate buffered solution of pH 7.4 at 37 °C. The drug release profile followed a biphasic pattern with a small initial burst followed by a zero-order release for up to 35 days. The initial burst release decreased with increasing HA content. The potential of HA in limiting the initial burst release makes the incorporation of HA into PLGA microspheres advantageous since it reduces the risk of drug overdose from high initial bursts. The linear sustained drug release profile over the course of 5 weeks makes these 5-FU-loaded HA/PLGA composite microparticles a promising delivery system for the controlled release of chemotherapy drugs in the treatment of cancer. PMID:22843166

Lin, Yuting; Li, Yan; Ooi, Chui Ping

2012-10-01

9

The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications  

NASA Astrophysics Data System (ADS)

Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

2014-04-01

10

The Effect of Temozolomide/Poly(lactide-co-glycolide) (PLGA)/Nano-Hydroxyapatite Microspheres on Glioma U87 Cells Behavior  

PubMed Central

In this study, we investigated the effects of temozolomide (TMZ)/Poly (lactide-co-glycolide)(PLGA)/nano-hydroxyapatite microspheres on the behavior of U87 glioma cells. The microspheres were fabricated by the “Solid/Water/Oil” method, and they were characterized by using X-Ray diffraction, scanning electron microscopy and differential scanning calorimetry. The proliferation, apoptosis and invasion of glioma cells were evaluated by MTT, flow cytometry assay and Transwell assay. The presence of the key invasive gene, ?V?3 integrin, was detected by the RT-PCR and Western blot method. It was found that the temozolomide/PLGA/nano-hydroxyapatite microspheres have a significantly diminished initial burst of drug release, compared to the TMZ laden PLGA microspheres. Our results suggest they can significantly inhibit the proliferation and invasion of glioma cells, and induce their apoptosis. Additionally, ?V?3 integrin was also reduced by the microspheres. These data suggest that by inhibiting the biological behavior of glioma cells in vitro, the newly designed temozolomide/PLGA/nano-hydroxyapatite microspheres, as controlled drug release carriers, have promising potential in treating glioma. PMID:22312307

Zhang, Dongyong; Tian, Ang; Xue, Xiangxin; Wang, Mei; Qiu, Bo; Wu, Anhua

2012-01-01

11

The effect of temozolomide/poly(lactide-co-glycolide) (PLGA)/nano-hydroxyapatite microspheres on glioma U87 cells behavior.  

PubMed

In this study, we investigated the effects of temozolomide (TMZ)/Poly (lactide-co-glycolide)(PLGA)/nano-hydroxyapatite microspheres on the behavior of U87 glioma cells. The microspheres were fabricated by the "Solid/Water/Oil" method, and they were characterized by using X-Ray diffraction, scanning electron microscopy and differential scanning calorimetry. The proliferation, apoptosis and invasion of glioma cells were evaluated by MTT, flow cytometry assay and Transwell assay. The presence of the key invasive gene, ?(V)?3 integrin, was detected by the RT-PCR and Western blot method. It was found that the temozolomide/PLGA/nano-hydroxyapatite microspheres have a significantly diminished initial burst of drug release, compared to the TMZ laden PLGA microspheres. Our results suggest they can significantly inhibit the proliferation and invasion of glioma cells, and induce their apoptosis. Additionally, ?(V)?3 integrin was also reduced by the microspheres. These data suggest that by inhibiting the biological behavior of glioma cells in vitro, the newly designed temozolomide/PLGA/nano-hydroxyapatite microspheres, as controlled drug release carriers, have promising potential in treating glioma. PMID:22312307

Zhang, Dongyong; Tian, Ang; Xue, Xiangxin; Wang, Mei; Qiu, Bo; Wu, Anhua

2012-01-01

12

Bactericidal property and biocompatibility of gentamicin-loaded mesoporous carbonated hydroxyapatite microspheres.  

PubMed

Implant-associated infection is a serious problem in orthopaedic surgery. One of the most effective ways is to introduce a controlled antibiotics delivery system into the bone filling materials, achieving sustained release of antibiotics in the local sites of bone defects. In the present work, mesoporous carbonated hydroxyapatite microspheres (MCHMs) loaded with gentamicin have been fabricated according to the following stages: (i) the preparation of the MCHMs by hydrothermal method using calcium carbonate microspheres as sacrificial templates, and (ii) loading gentamicin into the MCHMs. The MCHMs exhibit the 3D hierarchical nanostructures constructed by nanoplates as building blocks with mesopores and macropores, which make them have the higher drug loading efficiency of 70-75% than the conventional hydroxyapatite particles (HAPs) of 20-25%. The gentamicin-loaded MCHMs display the sustained drug release property, and the controlled release of gentamicin can minimize significantly bacterial adhesion and prevent biofilm formation against S. epidermidis. The biocompatibility tests by using human bone marrow stromal cells (hBMSCs) as cell models indicate that the gentamicin-loaded MCHMs have as excellent biocompatibility as the HAPs, and the dose of the released gentamicin from the MCHMs has no toxic effects on the hBMSCs. Hence, the gentamicin-loaded MCHMs can be served as a simple, non-toxic and controlled drug delivery system to treat bone infections. PMID:23910253

Guo, Ya-Jun; Long, Teng; Chen, Wei; Ning, Cong-Qin; Zhu, Zhen-An; Guo, Ya-Ping

2013-10-01

13

Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly- L-lactide (PLLA): Part I. Basic characteristics  

Microsoft Academic Search

Compounds that had neither calcined nor sintered hydroxyapatite (u-HA) particles (particulate size 0.2–20?m, averaging 3.0?m, Ca\\/P=1.69, and containing CO2-3) uniformly distributed in a poly-L-lactide (PLLA, M?v: 400KDa) matrix with a content of 20–50wt% (with 10% increment) were reinforced into composites by a forging process, which was a unique compression molding, and were then machined on a lathe in order to

Y Shikinami; M Okuno

1999-01-01

14

Facile fabrication of nanorod-assembled fluorine-substituted hydroxyapatite (FHA) microspheres.  

PubMed

Nanorod-assembled FHA microspheres with different F contents were for the first time prepared through a facile one-step hydrothermal method. The effect of the reaction time and pH value of reaction solutions on the FHA morphology was investigated to elucidate the self-assembly process of FHA microspheres. The results showed pH values had significant effect on the morphology of the formed FHA crystals, which were self-assembled into sphere-like sturctures at high pH conditions and rod-like structures at low pH values. The results suggested that formation of FHA crystals with varied morphology may be directly related to Ca(2+) release kinetics from EDTA-Ca-Na2 at different pH conditions. Furthermore, it was found that the chemical stability of FHA microspheres was dependent on the F content in the materials, and high F contents in FHA microspheres lead to improved chemical stability. These results suggest that the prepared self-assembled FHA microspheres may be used for teeth substitution materials due to their unique hierarchical structures and controllable chemical stability. PMID:23404821

Wang, Yueyue; Wu, Chengtie; Lin, Kaili; Chang, Jiang

2013-05-01

15

Analyzing the behavior of a porous nano-hydroxyapatite/polyamide 66 (n-HA/PA66) composite for healing of bone defects  

PubMed Central

The aim of this study was to analyze the behavior of the porous nano-hydroxyapatite/polyamide 66 (n-HA/PA66) composite grafted for bone defect repair through a series of biological safety experiments, animal experiments, and a more than 5-year long clinical follow-up. The biological safety experiments, carried out in accordance with the Chinese Guo Biao and Tolerancing (GB/T)16886 and GB/T16175, revealed that porous n-HA/PA66 composite had no cytotoxicity, no sensitization effect, no pyrogenic reaction, and that its hemolysis rate was 0.59% (less than 5%). Rabbit models of tibia defects with grafted porous n-HA/PA66 composite were established. After 2 weeks, the experiment showed that osteogenesis was detected in the porous n-HA/PA66 composite; the density of new bone formation was similar to the surrounding host bone at 12 weeks. After 26 weeks, the artificial bone rebuilt to lamellar bone completely. In the clinical study, a retrospective review was carried out for 21 patients who underwent serial radiographic assessment after treatment with porous n-HA/PA66 composite grafts following bone tumor resection. All wounds healed to grade A. No postoperative infections, delayed deep infection, nonspecific inflammation, rejection, or fractures were encountered. At a mean follow-up of 5.3 years, the mean Musculoskeletal Tumor Society’s (MSTS) 93 score was 29.3 points (range: 28–30 points) and mean radiopaque density ratio was 0.77±0.10. The radiologic analysis showed that porous n-HA/PA66 composite had been completely incorporated with the host bone about 1.5 years later. In conclusion, this study indicated that the porous n-HA/PA66 composite had biological safety, and good biocompatibility, osteoinduction, and osseointegration. Thus, the porous n-HA/PA66 composite is an ideal artificial bone substitute and worthy of promotion in the field. PMID:24531621

Xiong, Yan; Ren, Cheng; Zhang, Bin; Yang, Hongsheng; Lang, Yun; Min, Li; Zhang, Wenli; Pei, Fuxing; Yan, Yonggang; Li, Hong; Mo, Anchun; Tu, Chongqi; Duan, Hong

2014-01-01

16

Preparation, evaluation, and first clinical use of 177Lu-labeled hydroxyapatite (HA) particles in the treatment of rheumatoid arthritis: utility of cold kits for convenient dose formulation at hospital radiopharmacy.  

PubMed

While radiation synovectomy (RSV) constitutes a successful paradigm for the treatment of arthritis, a major cornerstone of its success resides in the selection of appropriate radiolabeled agent. Among the radionuclide used for RSV, the scope of using (177)Lu [T1/2 ?=?6.65 d, E?(max) ?=?497?keV, E? ?=?113?KeV (6.4%), 208?KeV (11%)] seemed to be attractive owing to its suitable decay characteristics, easy availability, and cost-effective production route. The present article describes a formulation of (177)Lu-labeled hydroxyapatite (HA) using ready-to-use kits of HA particles of 1-10?µm size range. The developed kits enable convenient one-step preparation of (177)Lu-HA (400?±?30?MBq doses) in high radiochemical purity (>99%) and stability at hospital radiopharmacy. The preparation showed promising results in pre-clinical studies carried out in Wistar rats bearing arthritis in knee joints. In preliminary clinical investigation, significant improvement in the disease conditions was reported in 10 patients with rheumatoid arthritis of knee joints treated with 333?±?46?MBq doses of (177)Lu-HA. The studies reveal that while (177)Lu labeled HA particles holds considerable promise as a cost-effective agent for RSV, the adopted strategy of using HA kits could be a potential step toward wider clinical utilization of radiolanthanide-labeled HA particles. PMID:24966157

Chakraborty, Sudipta; Vimalnath, K V; Rajeswari, A; Shinto, Ajit; Sarma, H D; Kamaleshwaran, K; Thirumalaisamy, P; Dash, Ashutosh

2014-06-15

17

Preparation and bioactivity evaluation of bone-like hydroxyapatite nanopowder  

Microsoft Academic Search

Calcium phosphate ceramic such as hydroxyapatite (HA) is good candidate for bone substitutes due to their chemical and structural similarity to bone minerals. The bone mineral consists of tiny hydroxyapatite crystals in the nanoregime. Nanostructured hydroxyapatite is also expected to have better bioactivity than coarser crystals. This paper reports on the preparation and in vitro evaluation of bone-like hydroxyapatite nanopowder.

M. H. Fathi; A. Hanifi; V. Mortazavi

2008-01-01

18

Dissolution of Human Teeth-Derived Hydroxyapatite  

Microsoft Academic Search

We have been interested in human teeth which consist of hydroxyapatite (HA), but do not degrade for a long time. In order\\u000a to overcome dissolution and mechanical degradation of man-made HA, biologically derived hydroxyapatite (BHA) ceramics were\\u000a prepared from human teeth and their dissolving behavior was investigated in distilled water for 3–14 days and compared with\\u000a an artificial HA made of

Dong Seok Seo; Jong Kook Lee

2008-01-01

19

Hydroxyapatite fiber reinforced poly( ?-hydroxy ester) foams for bone regeneration  

Microsoft Academic Search

A process has been developed to manufacture biodegradable composite foams of poly(DL-lactic-co-glycolic acid) (PLGA) and hydroxyapatite short fibers for use in bone regeneration. The processing technique allows the manufacture of three-dimensional foam scaffolds and involves the formation of a composite material consisting of a porogen material (either gelatin microspheres or salt particles) and hydroxyapatite short fibers embedded in a PLGA

Robert C. Thomson; Michael J. Yaszemski; John M. Powers; Antonios G. Mikos

1998-01-01

20

Molten Salt Synthesis of Calcium Hydroxyapatite Whiskers A. Cuneyt Tas*,  

E-print Network

Molten Salt Synthesis of Calcium Hydroxyapatite Whiskers A. Cu¨neyt Tas¸*, Department hydroxyapatite (HA) whiskers and crystals were produced by the route of molten salt synthesis. The effects. A tentative X-ray diffraction pattern was proposed for the HA whiskers. Molten salt synthesis with a K2SO4

Tas, A. Cuneyt

21

Hydroxyapatite coating by dipping method, and bone bonding strength  

Microsoft Academic Search

Hydroxyapatite (HA) was coated onto titanium rods by a dip coating method using HA sol. The HA sols were prepared by dispersing HA crystals less than 100 nm length in distilled water or physiological salt solution using an ultrasonic homogenizer. The surface of the HA coating was homogeneous as determined by scanning electron microscopy (SEM). After implantation of uncoated and

Tuantuan Li; Junhee Lee; Takayuki Kobayashi; Hideki Aoki

1996-01-01

22

Chemically coupled hydroxyapatite-polyethylene composites: processing and characterisation  

Microsoft Academic Search

Hydroxyapatite (HA)-reinforced polyethylene was developed as a bone replacement material. In order to improve bonding between HA and polyethylene, and hence to increase mechanical properties of the composite, chemical treatments of HA and polyethylene were investigated and new composites manufactured. Two approaches were employed in this investigation: the use of silane-treated HA as the filler, and the application of polymer

M Wang; S Deb; W Bonfield

2000-01-01

23

Nutrient-substituted hydroxyapatites: synthesis and characterization  

NASA Technical Reports Server (NTRS)

Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

Golden, D. C.; Ming, D. W.

1999-01-01

24

Chemical characterization of silicon-substituted hydroxyapatite.  

PubMed

Bioceramic specimens have been prepared by incorporating a small amount of silicon (0.4 wt %) into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HA] via an aqueous precipitation reaction to produce a silicon-substituted hydroxyapatite (Si-HA). The results of chemical analysis confirmed the proposed substitution of the silicon (or silicate) ion for the phosphorus (or phosphate) ion in hydroxyapatite. The Si-HA was produced by first preparing a silicon-substituted apatite (Si-Ap) by a precipitation process. A single-phase Si-HA was obtained by heating/calcining the as-prepared Si-Ap to temperatures above 700 degrees C; no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP), or calcium oxide (CaO), were observed by X-ray diffraction analysis. Although the X-ray diffraction patterns of Si-HA and stoichiometric HA appeared to be identical, refinement of the diffraction data revealed some small structural differences between the two materials. The silicon substitution in the HA lattice resulted in a small decrease in the a axis and an increase in the c axis of the unit cell. This substitution also caused a decrease in the number of hydroxyl (OH) groups in the unit cell, which was expected from the proposed substitution mechanism. The incorporation of silicon in the HA lattice resulted in an increase in the distortion of the PO4 tetrahedra, indicated by an increase in the distortion index. Analysis of the Si-HA by Fourier transform infrared (FTIR) spectroscopy indicated that although the amount of silicon incorporated into the HA lattice was small, silicon substitution appeared to affect the FTIR spectra of HA, in particular the P-O vibrational bands. The results demonstrate that phase-pure silicon-substituted hydroxyapatite may be prepared using a simple precipitation technique. PMID:10397946

Gibson, I R; Best, S M; Bonfield, W

1999-03-15

25

Structural analysis of hydroxyapatite\\/bioactive glass composite coatings obtained by plasma spray processing  

Microsoft Academic Search

Bioactive materials such as hydroxyapatite (HA) are used as coatings on metallic implants, producing a conjugate with better performance. The coatings are in general obtained by a plasma spray process. In this work the structural properties of composite coatings hydroxyapatite\\/bioactive glass (HA\\/BG) as well as coatings of the pure materials are measured. The coatings were obtained by plasma spraying mixtures

Flávio L. S Carvalho; Christiano S Borges; José Roberto T Branco; Marivalda M Pereira

1999-01-01

26

The wet precipitation process of hydroxyapatite  

Microsoft Academic Search

Stoichiometric hydroxyapatite (HA) powder was synthesized by wet method using orthophosphoric acid and calcium hydroxide, as raw materials. In this regard, the time-depending changes of the precipitated particles and effects of heating on them were investigated. The as-precipitated and heated powder samples were examined using field emission electron microscopy (FESEM), XRD and Raman spectroscopy methods. The results revealed that the

M. R. Saeri; A. Afshar; M. Ghorbani; N. Ehsani; C. C. Sorrell

2003-01-01

27

Adsorption of bovine serum albumin onto hydroxyapatite  

Microsoft Academic Search

The adsorption of bovine serum albumin (BSA) onto hydroxyapatite (HA) has been studied as a function of protein concentration, pH and ionic strength. Isotherm data (adsorption being a reversible process) have been analysed using the Langmuir model, the adsorption parameters AT (maximum amount of protein adsorbed, mg m?2) and K (affinity constant, L g?1) being calculated for each solution condition

Diana T. Hughes Wassell; Rachel C. Hall; Graham Embery

1995-01-01

28

Polyacrolein microspheres as immunoreagents.  

PubMed

Polyacrolein microspheres were prepared by radiation polymerization of acrolein in the absence of emulsifying or stabilizing agent. The microspheres had functional surface aldehyde groups permitting covalent binding with antibody in 1 step. The particle size of the microspheres varied with polymerization conditions, especially irradiation temperature. The microsphere antibody conjugates obtained by binding immunoglobulins to polyacrolein microspheres were used to label cells. The reactivity of microsphere antibody conjugates was shown by specific aggregation by antigen. PMID:6352813

Kumakura, M; Suzuki, M; Adachi, S; Kaetsu, I

1983-09-30

29

Mechanisms of proteoglycan inhibition of hydroxyapatite growth  

Microsoft Academic Search

Summary  Purified bovine nasal cartilage proteoglycans (aggregate and subunit containing fractions) and to a lesser degree, chondroitin\\u000a 4-sulfate of physiological size, retard seeded hydroxyapatite (HA) growthin vitro. The large hydrodynamic size and high charge density of these macromolecules are believed to be associated with the ability\\u000a of proteoglycans to inhibit HA formation and growth. We now demonstrate the involvement of the

Chun-Chang Chen; Adele L. Boskey

1985-01-01

30

Microradiographic microsphere manipulator  

DOEpatents

A method and apparatus for radiographic characterization of small hollow spherical members (microspheres), constructed of either optically transparent or opaque materials. The apparatus involves a microsphere manipulator which holds a batch of microspheres between two parallel thin plastic films for contact microradiographic characterization or projection microradiography thereof. One plastic film is translated to relative to and parallel to the other to roll the microspheres through any desired angle to allow different views of the microspheres.

Singleton, Russell M. (Livermore, CA)

1980-01-01

31

Preparation of irregular mesoporous hydroxyapatite  

SciTech Connect

An irregular mesoporous hydroxyapatite (meso-HA), Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, is successfully prepared from Ca(NO{sub 3}){sub 2}.4H{sub 2}O and NH{sub 4}H{sub 2}PO{sub 4} using surfactant cetyltrimethyl ammonium bromide (CTAB) as template. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results reveal that the positive head of CTAB is assembled on the surface precipitated HA and much NH{sub 4}{sup +} is enclosed in precipitated HA before calcination. Field scanning electron microscope (FSEM) reveals that there exist many interconnected pores throughout the HA reticular skeleton. Nitrogen adsorption-desorption experiment exhibits a mesoporous material type IV curve, and pore size distribution calculated from the desorption branch of the isotherms based on Barrett-Joyner-Halenda (BJH) model shows that most pores throughout the HA reticular skeleton are sized at about 40 nm, but the pores are not uniform on the whole, owning to decomposition of the 'organic' CTAB templating structures and ammonium salt enclosed in the precipitated HA. The specific surface area of irregular meso-HA is calculated to be 37.6 m{sup 2}/g according to the Brunauer-Emmett-Teller (BET) equation. Moreover, after polylactic acid/meso-HA (PLA/meso-HA) composites degraded 12 weeks in normal saline at 37 deg. C, the interconnected pores throughout the HA skeleton were enlarged and sized in micron degree, which resemble trabecular bone structure very much.

Wang Hualin [School of Chemical Technology, Hefei University of Technology, Hefei, Anhui 230009 (China)], E-mail: hlwang@hfut.edu.cn; Zhai Linfeng; Li Yanhong; Shi Tiejun [School of Chemical Technology, Hefei University of Technology, Hefei, Anhui 230009 (China)

2008-06-03

32

Hydrothermal synthesis of hierarchical hydroxyapatite: Preparation, growth mechanism and drug release property  

Microsoft Academic Search

Hydroxyapatite (HAP) hierarchical microspheres were synthesized by a facile hydrothermal method using calcium nitrate and ammonium dihydrogen phosphate through controlling complexing agents. The influences of two kinds of complexing agents (potassium sodium tartrate tetrahydrate and trisodium citrate) and reaction time on the morphology of HAP crystals have been investigated. These results indicate that complexing agents have a great influence on

Li-Xia Yang; Jia-Jun Yin; Lu-Lu Wang; Guo-Xiu Xing; Ping Yin; Quan-Wen Liu

33

Hybrid microspheres  

NASA Technical Reports Server (NTRS)

Substrates, particularly inert synthetic organic resin beads (10) or sheet (12) such as polystyrene are coated with a covalently bound layer (24) of polyacrolein by irradiation a solution (14) of acrolein or other aldehyde with high intensity radiation. Individual microspheres (22) are formed which attach to the surface to form the aldehyde containing layer (24). The aldehyde groups can be converted to other functional groups by reaction with materials such as hydroxylamine. Adducts of proteins such as antibodies or enzymes can be formed by direct reaction with the surface aldehyde groups.

Rembaum, Alan (Inventor); Yen, Richard C. K. (Inventor)

1985-01-01

34

Characterization of high velocity oxy-fuel combustion sprayed hydroxyapatite  

Microsoft Academic Search

Bioceramic coatings, created by the high velocity oxy-fuel combustion spraying of hydroxyapatite (HA) powders onto commercially pure titanium, were characterized in order to determine whether this relatively new coating process can be successfully applied to bioceramic coatings of orthopaedic and dental implants. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterize both the HA starting

Jeannie D. Haman; Linda C. Lucas; Daryl Crawmer

1995-01-01

35

Polymeric micelle-templated synthesis of hydroxyapatite hollow nanoparticles for a drug delivery system  

Microsoft Academic Search

Hydroxyapatite (HA) hollow nanoparticles (HNPs) have great potential in nanoscaled delivery devices due to their small size, excellent biocompatibility and expected high capacity. However, the preparation of HA HNPs for their application in a drug delivery system has rarely been reported because HA has a complicated crystal structure and it is difficult to obtain stable HA HNPs with hollows that

Feng Ye; Haifeng Guo; Haijiao Zhang; Xiulan He

2010-01-01

36

Ectopic bone formation associated with mesenchymal stem cells in a resorbable calcium deficient hydroxyapatite carrier  

Microsoft Academic Search

Bone substitute materials can induce bone formation in combination with mesenchymal stem cells (MSC). The aim of the current study was to examine ectopic in vivo bone formation with and without MSC on a new resorbable ceramic, called calcium deficient hydroxyapatite (CDHA). Ceramic blocks characterized by a large surface (48m2\\/g) were compared with ?-tricalcium phosphate (?-TCP), hydroxyapatite (HA) ceramics (both

Philip Kasten; Julia Vogel; Reto Luginbühl; Philip Niemeyer; Marcus Tonak; Helga Lorenz; Lars Helbig; Stefan Weiss; Jörg Fellenberg; Albrecht Leo; Hans-Georg Simank; Wiltrud Richter

2005-01-01

37

Differentiation between hydroxyapatite and ?-tricalcium phosphate by means of ?-Raman spectroscopy  

Microsoft Academic Search

We present a comparative study of the Roman spectra of polycrystalline ?-tricalcium phosphate (?-TCP) and hydroxyapatite (HA) over their whole optical frequency range. Due to their structural differences, Raman scattering permits to differentiate between these two calcium phosphates, not only through the detection of vibrational modes associated with the OH? group of hydroxyapatite, but also by comparing the bands arising

R. Cuscó; F. Guitián; S. de Aza; L. Artús

1998-01-01

38

In situ synthesis and biocompatibility of nano hydroxyapatite on pristine and chitosan functionalized  

E-print Network

composites, thereis a drive to search for this new kind of carbon material as a reinforcing phaseIn situ synthesis and biocompatibility of nano hydroxyapatite on pristine and chitosan to the GO­HA composite. These findings may provide new prospects for utilizing the GO- based hydroxyapatite

Zheng, Yufeng

39

Hydroxyapatite whisker-reinforced polyetherketoneketone bone ingrowth scaffolds  

Microsoft Academic Search

Hydroxyapatite (HA) whisker-reinforced polyetherketoneketone (PEKK) bone ingrowth scaffolds were prepared and characterized. High levels of porosity (75–90%) and HA whisker reinforcement (0–40 vol.%) were attained using a powder processing approach to mix the HA whiskers, PEKK powder and a NaCl porogen, followed by compression molding at 350–375°C and particle leaching to remove the porogen. The scaffold architecture and microstructure exhibited

Gabriel L. Converse; Timothy L. Conrad; Christina H. Merrill; Ryan K. Roeder

2010-01-01

40

microsphere assemblies  

NASA Astrophysics Data System (ADS)

The effect of Fe ion concentration on the morphological, structural, and optical properties of TiO2 films supported on silica (SiO2) opals has been studied. TiO2:Fe2O3 films were prepared by the sol-gel method in combination with a vertical dip coating procedure; precursor solutions of Ti and Fe were deposited on a monolayer of SiO2 opals previously deposited on a glass substrate by the same procedure. After the dip coating process has been carried out, the samples were thermally treated to obtain the TiO2:Fe2O3/SiO2 composites at the Fe ion concentrations of 1, 3, and 5 wt%. Scanning electron microscopy (SEM) micrographs show the formation of colloidal silica microspheres of about 50 nm diameter autoensembled in a hexagonal close-packed fashion. Although the X-ray diffractograms show no significant effect of Fe ion concentration on the crystal structure of TiO2, the ?-Raman and reflectance spectra do show that the intensity of a phonon vibration mode and the energy bandgap of TiO2 decrease as the Fe+3 ion concentration increases.

Peña-Flores, Jesús I.; Palomec-Garfias, Abraham F.; Márquez-Beltrán, César; Sánchez-Mora, Enrique; Gómez-Barojas, Estela; Pérez-Rodríguez, Felipe

2014-09-01

41

Nanoscale influences on bioactivity : ultrastructure and nanomechanics of model bioactive hydroxyapatite based biomaterials  

E-print Network

There is a significant need for improved synthetic materials as orthopedic implants to replace human bone lost and damaged due to disease or injury. Certain ceramics, such as hydroxyapatite (HA), have the special property ...

Vandiver, Jennifer M. (Jennifer McKeehan)

2006-01-01

42

Porous hydroxyapatite-gelatin composites with functions of bone substitutes and drug releasing agents: A preliminary study  

NASA Astrophysics Data System (ADS)

Biomedical composites made of porous hydroxyapatite (HA) bonded with a biodegradable polymeric matrix gelatin have been prepared. This device is expected to be useful as an excellent bone graft with bioactive hydroxyapatite which will facilitate new bone formation and at the same time it could functions as drug delivery with a controlled release rate. In this preliminary report, we wish to present preparation and physical characterization of the biomedical composite and the non-biodegradable porous hydroxyapatite composing the matrix of the composite. Porous hydroxyapatite was prepared via polymeric sponge method using hydroxyapatite nanopowders which were prepared via sol-gel procedure. Suspensions of the sol-gel derived hydroxyapatite powder was prepared with an adjusted loading of hydroxyapatite, using a dispersant. After soaking cellulosic sponges into the suspension, the sponges were dried and then subjected to heat-treatment at 600°C, followed by sintering at 1250°C for 1h. Three types of porous hydroxyapatite samples have been prepared in various composition of hydroxyapatite suspension. Porous hydroxyapatite bodies produced from slurry with less hydroxyapatite powder content and more dispersant amount yielded higher porosity and thus causing weaker compressive strength. Compressive strengths varied between 0.67 and 1.94 MPa depending on the porosity of the sample. Porosity plays important role in gelatin loading; the amount of gelatin coated on the porous hydroxyapatite bodies depend on porosity and the gelatin concentration in water solution. The higher porosity the more gelatin can be absorbed by the porous body.

Sopyan, I.; Sulaiman, N. S.; Gustiono, D.; Herdianto, N.

2006-01-01

43

Nanocrystalline Hydroxyapatite/Si Coating by Mechanical Alloying Technique  

PubMed Central

A novel approach for depositing hydroxyapatite (HA) films on titanium substrates by using mechanical alloying (MA) technique has been developed. However, it was shown that one-hour heat treatment at 800°C of such mechanically coated HA layer leads to partial transformation of desired HA phase to beta-tri-calcium phosphate (?-TCP) phase. It appears that the grain boundary and interface defects formed during MA promote this transformation. It was discovered that doping HA by silicon results in hindering this phase transformation process. The Si-doped HA does not show phase transition to ?-TCP or decomposition after heat treatment even at 900°C. PMID:22312324

Hannora, Ahmed E.; Mukasyan, Alexander S.; Mansurov, Zulkhair A.

2012-01-01

44

Removal of Uranium in Drinking Water: Brimac Environmental Services, Inc. Brimac HA 216 Adsorptive Media  

EPA Science Inventory

The Brimac HA 216 Adsorptive Media was tested for uranium (U) removal from a drinking water source (well water) at Grappone Toyota located in Bow, New Hampshire. The HA 216 media is a hydroxyapatite-based material. A pilot unit, consisting of a TIGG Corporation Cansorb® C-5 ste...

45

Effects of degradation and porosity on the load bearing properties of model hydroxyapatite bone scaffolds.  

SciTech Connect

Degradation of three types of model hydroxyapatite (HA) scaffolds was studied after in vitro degradation in a sodium acetate buffer (pH 4). Degradation was evaluated using compression testing, scanning electron microscopy (SEM), inductively coupled plasma (ICP) analysis, and weight measurements. Scaffolds were fabricated with a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. Scaffolds had a macrostructure resembling a lattice of rods. Scaffolds contained either macropores (270 or 680 m in the x-y direction and 280 m in the z-direction) and micropores (1-30-m pores and pores <1 m) or only macropores pores (270 m in the x-y direction and 280 m in the z-direction). A computer-aided design (CAD) program controlled the size and distribution of macropores; micropores were created by polymethylmethacrylate (PMMA) microsphere porogens (1-30-m pore diameter) and controlled sintering (pores <1 m). Percent weight loss of the scaffolds and calcium and phosphorus ion concentrations in solution increased as the degradation period increased for all scaffold types. After degradation, compressive strength and compressive modulus decreased significantly for those scaffolds with microporosity. For scaffolds without microporosity, the changes in strength and modulus after degradation were not statistically significant. The compressive strength of scaffolds without microporosity was significantly greater than the scaffolds with microporosity.

Dellinger, Jennifer Gwynne; Cesarano, Joseph, III; Jamison, Russell D. (University of Illinois at Urbana-Champaign, Urbana, IL); Wojtowicz, Abigail M. (Georgia Institute of Technology, Atlanta, GA)

2005-06-01

46

Impact behavior of hydroxyapatite reinforced polyethylene composites.  

PubMed

Hydroxyapatite particulate reinforced high density polyethylene composite (HA-HDPE) has been developed as a bone replacement material. The impact behavior of the composites at 37 degrees C has been investigated using an instrumented falling weight impact testing machine. The fracture surfaces were examined using SEM and the fracture mechanisms are discussed. It was found that the fracture toughness of HA-HDPE composites increased with HDPE molecular weight, but decreased with increasing HA volume fraction. Examination of fracture surfaces revealed weak filler/matrix interfaces which can debond easily to enable crack initiation and propagation. Increasing HA volume fraction increases the interface area, and more cracks can form and develop, thus decreasing the impact resistance of the composites. Another important factor for the impact behavior of the composites is the matrix. At higher molecular weight, HDPE is able to sustain more plastic deformation and dissipates more impact energy, hence improving the impact property. PMID:15348540

Zhang, Y; Tanner, K E

2003-01-01

47

Determination of Microstructural Parameters of Nanocrystalline Hydroxyapatite Prepared by Mechanical Alloying Method  

NASA Astrophysics Data System (ADS)

Hydroxyapatite [HA, Ca10(PO4)6(OH)2] is chemically similar to the mineral component of bones and hard tissues. HA can support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications. In this research, HA nanostructure was synthesized by mechanical alloying method. Phase development, particle size and morphology of HA were investigated by X-ray diffraction (XRD) pattern, zetasizer instrument, scanning electron microscopy (SEM), respectively. XRD pattern has been used to determination of the microstructural parameters (crystallite size, lattice parameters and crystallinity percent) by Williamson-Hall equation, Nelson-Riley method and calculating the areas under the peaks, respectively. The crystallite size and particle size of HA powders were in nanometric scales. SEM images showed that some parts of HA particles have agglomerates. The ratio of lattice parameters of synthetic hydroxyapatite (c/a = 0.73) was determined in this study is the same as natural hydroxyapatite structure.

Joughehdoust, Sedigheh; Manafi, Sahebali

2011-12-01

48

Preparation of bioactive porous HA/PCL composite scaffolds  

NASA Astrophysics Data System (ADS)

Porous hydroxyapatite (HA) bioceramic scaffold has been widely attracted the attention to act as a three-dimensional (3D) template for cell adhesion, proliferation, differentiation and thus promoting bone and cartilage regeneration because of its osteoinduction. However, the porous bioceramic scaffold is fragile so that it is not suitable to be applied in clinic for bone repair or replacement. Therefore, it is significant to improve the mechanical property of porous HA bioceramics while the interconnected structure is maintained for tissue ingrowth in vivo. In the present research, a porous composite scaffold composed of HA scaffold and polycaprolactone (PCL) lining was fabricated by the method of polymer impregnating to produce HA scaffold coated with PCL lining. Subsequently, the composite scaffolds were deposited with biomimetic coating for improving the bioactivity. The HA/PCL composite scaffolds with improved mechanical property and bioactivity is expected to be a promising bone substitute in tissue engineering applications.

Zhao, J.; Guo, L. Y.; Yang, X. B.; Weng, J.

2008-12-01

49

Chemical Preparation of Carbonated Calcium Hydroxyapatite Powders at 37  

E-print Network

Chemical Preparation of Carbonated Calcium Hydroxyapatite Powders at 37 C in Urea-phase ceramic powder. Carbonated HA powders were formed from calcium nitrate tetrahydrate and di- ammonium properties. They were usually observed1 to be carbonate-substituted and calcium-de®cient. Synthetic body

Tas, A. Cuneyt

50

Hydroxyapatite nanoparticles: electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics.  

PubMed

Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction. PMID:23225849

Zakaria, Siti Maisurah; Sharif Zein, Sharif Hussein; Othman, Mohd Roslee; Jansen, John A

2013-07-01

51

The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth  

PubMed Central

Synthetic hydroxyapatite (HA) has been widely used and developed as the material for bone substitute in medical applications. The addition of zirconia is needed to improve the strength of hydroxyapatite as the bone substitute. One of the drawbacks in the use of biomedical materials is the occurrence of biomaterial-centred infections. The recent method of limiting the presence of microorganism on biomaterials is by providing biomaterial-bound metal-containing compositions. In this case, S. epidermidis is the most common infectious organism in biomedical-centred infection. Objective. This study was designed to evaluate the effect of zirconia concentrations in hydroxyapatite on the growth of S. epidermidis. Methods and Materials. The subjects of this study were twenty hydroxyapatite discs, divided into four groups in which one was the control and the other three were the treatment groups. Zirconia powder with the concentrations of 20%, 30%, and 40% was added into the three different treatment groups. Scanning electron microscope analysis was performed according to the hydroxyapatite and hydroxyapatite-zirconia specimens. All discs were immersed into S. epidermidis culture for 24 hours and later on they were soaked into a medium of PBS. The cultured medium was spread on mannitol salt agar. After incubation for 24 hours at 37°C , the number of colonies was measured with colony counter. Data obtained were analyzed using the ANOVA followed by the pairwise comparison. Result. The statistical analysis showed that different concentrations of zirconia powder significantly influenced the number of S. epidermidis colony (P < 0.05) . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony. PMID:22919390

Siswomihardjo, Widowati; Sunarintyas, Siti; Tontowi, Alva Edy

2012-01-01

52

Characterization of chemical inhomogeneity in plasma-sprayed hydroxyapatite coatings  

Microsoft Academic Search

Successful applications of plasma-sprayed hydroxyapatite (HA) coating for implants rely on understanding characteristics of the coating's microstructure, particularly its inhomogeneity. We explored three new techniques for characterizing the chemical inhomogeneity of sprayed HA coatings on titanium substrate: micro-Raman spectroscopy (MRS), positive and negative ion ratios of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the energy loss peaks of X-ray photoelectron

Liling Yan; Yang Leng; Lu-Tao Weng

2003-01-01

53

Processing and tensile properties of hydroxyapatite-whisker-reinforced polyetheretherketone  

Microsoft Academic Search

Polyetheretherketone (PEEK) was reinforced with 0–50vol% hydroxyapatite (HA) whiskers using a novel powder processing and compression molding technique which enabled uniform mixing at high whisker content. Texture analysis showed that viscous flow during compression molding produced a preferred orientation of whiskers along the specimen tensile axis. Consequently, the elastic modulus or ultimate tensile strength of HA-whisker-reinforced PEEK was able to

Gabriel L. Converse; Weimin Yue; Ryan K. Roeder

2007-01-01

54

Mechanical properties of hydroxyapatite whisker reinforced polyetherketoneketone composite scaffolds  

Microsoft Academic Search

The apparent mechanical properties of hydroxyapatite (HA) whisker reinforced polyetherketoneketone (PEKK) scaffolds were evaluated in unconfined, uniaxial compression to investigate the effects of the porosity (75%, 82.5% and 90%), HA content (0, 20 and 40 vol%) and mold temperature (350, 365 and 375 ?C). Increased porosity resulted in a non-linear decrease in the elastic modulus and yield strength for both reinforced

Gabriel L. Converse; Timothy L. Conrad; Ryan K. Roeder

2009-01-01

55

Production of hollow aerogel microspheres  

DOEpatents

A method is described for making hollow aerogel microspheres of 800-1200 .mu. diameter and 100-300 .mu. wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

Upadhye, Ravindra S. (Pleasanton, CA); Henning, Sten A. (Dalby, SE)

1993-01-01

56

Production of hollow aerogel microspheres  

SciTech Connect

A method is described for making hollow aerogel microspheres of 800--1200{mu} diameter and 100--300{mu} wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

Upadhye, R.S.; Henning, S.A.

1990-12-31

57

Biological activity of lactoferrin-functionalized biomimetic hydroxyapatite nanocrystals  

PubMed Central

The emergence of bacterial strains resistant to antibiotics is a general public health problem. Progress in developing new molecules with antimicrobial properties has been made. In this study, we evaluated the biological activity of a hybrid nanocomposite composed of synthetic biomimetic hydroxyapatite surface-functionalized by lactoferrin (LF-HA). We evaluated the antimicrobial, anti-inflammatory, and antioxidant properties of LF-HA and found that the composite was active against both Gram-positive and Gram-negative bacteria, and that it modulated proinflammatory and anti-inflammatory responses and enhanced antioxidant properties as compared with LF alone. These results indicate the possibility of using LF-HA as an antimicrobial system and biomimetic hydroxyapatite as a candidate for innovative biomedical applications. PMID:24623976

Nocerino, Nunzia; Fulgione, Andrea; Iannaccone, Marco; Tomasetta, Laura; Ianniello, Flora; Martora, Francesca; Lelli, Marco; Roveri, Norberto; Capuano, Federico; Capparelli, Rosanna

2014-01-01

58

Raman spectroscopy determination of phases within thermal sprayed hydroxyapatite splats and subsequent in vitro dissolution examination  

Microsoft Academic Search

Phase compositions at various locations within individual thermal sprayed hydroxyapatite (HA) splats were qualitatively determined using Raman spectroscopy analysis and, confirmed through in vitro dissolution exercise. The purpose of the present study was to verify the locations of different phases within a HA splat deposited by thermal spray techniques. The splats were prepared through dc thermal plasma and high velocity

H. Li; B. S. Ng; K. A. Khor; P. Cheang; T. W. Clyne

2004-01-01

59

Influence of temperature, ripening time and calcination on the morphology and crystallinity of hydroxyapatite nanoparticles  

Microsoft Academic Search

Nano-sized hydroxyapatite (HA) particles were prepared by chemical precipitation through aqueous solutions of calcium chloride and ammonium hydrogenphosphate. The influence of temperature, ripening time and calcination on the crystallinity and morphology of the HA nanoparticles were investigated. It was found that the crystallinity and crystallite size increased with the increase of synthetic temperature and ripening time. XRD and TEM results

Y. X. Pang; X. Bao

2003-01-01

60

Antimicrobial effects of metal ions (Ag+, Cu2+, Zn2+) in hydroxyapatite  

Microsoft Academic Search

The antimicrobial ceramics (AC) based on hydroxyapatite (HA) were made in a wet chemical process with additions of AgNO3, Cu(NO3)2 · 3H2O and Zn(NO3)2 · 6H2O. The ACs were composed of metal-ion substituted hydroxyapatite and nitrate–apatite, which was identified by X-ray diffraction. The viable count and turbidity measurement was adopted to observe the antimicrobial effects of the various ACs. The

T. N Kim; Q. L Feng; J. O Kim; J Wu; H Wang; G. C Chen; F. Z Cui

1998-01-01

61

Collagen hydrolysate based collagen/hydroxyapatite composite materials  

NASA Astrophysics Data System (ADS)

The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ? 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

2013-04-01

62

The influence of collagen support and ionic species on the morphology of collagen/hydroxyapatite composite materials  

SciTech Connect

The purpose of this investigation is to study the influence of collagenous supports and ionic species on the precipitation of hydroxyapatite (HA) from aqueous solutions. To this end, we obtained hydroxyapatite by co-precipitation from a solution of calcium hydroxide and sodium dihydrogenophosphate. The formation of HA was studied by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that the morphology of hydroxyapatite is highly influenced by the support material and the ionic species present. The obtained materials were studied by scanning electron microscopy (SEM).

Ficai, Anton, E-mail: anton_ficai81@yahoo.com [Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science, 1-5 Polizu Str., 011061 Bucharest (Romania); Andronescu, Ecaterina; Voicu, Georgeta; Ghitulica, Cristina; Ficai, Denisa [Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science, 1-5 Polizu Str., 011061 Bucharest (Romania)

2010-04-15

63

Organic aerogel microspheres  

DOEpatents

Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, Steven T. (San Leandro, CA); Kong, Fung-Ming (Pleasanton, CA); Pekala, Richard W. (Pleasant Hill, CA); Kaschmitter, James L. (Pleasanton, CA)

1999-01-01

64

Organic aerogel microspheres  

DOEpatents

Organic aerogel microspheres are disclosed which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonstick gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, S.T.; Kong, F.M.; Pekala, R.W.; Kaschmitter, J.L.

1999-06-01

65

Preparation and characterization of PHBV microsphere/45S5 bioactive glass composite scaffolds with vancomycin releasing function.  

PubMed

PHBV microsphere/45S5 bioactive glass (BG) composite scaffolds with drug release function were developed for bone tissue engineering. BG-based glass-ceramic scaffolds with high porosity (94%) and interconnected pore structure prepared by foam replication method were coated with PHBV microspheres (nominal diameter=3.5 ?m) produced by water-in-oil-in-water double emulsion solvent evaporation method. A homogeneous microsphere coating throughout the porous structure of scaffolds was obtained by a simple dip coating method, using the slurry of PHBV microspheres in hexane. Compressive strength tests showed that the microsphere coating slightly improved the mechanical properties of the scaffolds. It was confirmed that the microsphere coating did not inhibit the bioactivity of the scaffolds in SBF. Hydroxyapatite crystals homogeneously grew not only on the struts of the scaffolds but also on the surface of microspheres within 7 days of immersion in SBF. Vancomycin was successfully encapsulated into the PHBV microspheres. The encapsulated vancomycin was released with a dual release profile involving a relatively low initial burst release (21%) and a sustained release (1 month), which is favorable compared to the high initial burst release (77%) and short release period (4 days) measured on uncoated scaffolds. The developed bioactive composite scaffold with drug delivery function has thus the potential to be used advantageously in bone tissue engineering. PMID:24907766

Li, Wei; Ding, Yaping; Rai, Ranjana; Roether, Judith A; Schubert, Dirk W; Boccaccini, Aldo R

2014-08-01

66

Osteoblast response to nanocrystalline calcium hydroxyapatite depends on carbonate content.  

PubMed

Normal bone mineral is a carbonated-apatite, but there are limited data on the effect of mineral containing carbonate on cell response. We characterized surface chemical compositions of three experimental carbonated hydroxyapatite (CO3(2-) HA) substrates and investigated their effect on osteoblast differentiation. Carbonate was incorporated into the hydroxyapatite powders while phosphate and hydroxyl groups were shown to be reduced by analyzing the chemical composition of the substrate surfaces. CO3(2-) HA powders with increasing carbonate concentrations designated as C1 (3.88%), C2 (4.85%), and C3 (5.82%) were molded, pressed, and fired into 14 mm discs. We observed that calcium phosphate ratios increased monotonically with increasing carbonate content, whereas differentiation of MG63 cells decreased. CO3(2-) HA surfaces also affected factor production. Addition of carbonate caused a 70% reduction in osteoprotegerin (OPG) compared to cultures on pure HA, but the effect of carbonate was not dose-dependent. Low carbonate content reduced VEGF-A by 80%, but higher levels of carbonate reversed this effect in a concentration dependent manner, with the C3 VEFG-A levels approximately twice that of C1 levels. These observations collectively indicate that bone cells are sensitive to carbonate content in bone mineral and the effects of carbonate substitution vary with the outcome being measured. Overall, this study provides a preliminary understanding of how carbonate substitution within hydroxyapatite modulates cellular behavior. PMID:24167147

Adams, Brandy R; Mostafa, Amany; Schwartz, Zvi; Boyan, Barbara D

2014-09-01

67

Preparing nanocomposite fibrous scaffolds of P3HB\\/nHA for bone tissue engineering  

Microsoft Academic Search

Nanocomposites are recently known to be among the most successful materials in biomedical applications. In this work we sought to fabricate fibrous scaffolds which can mimic the extra cellular matrix of cartilaginous connective tissue not only to a structural extent but with a mechanical and biological analogy. Poly(3-hydroxybutyrate) (P3HB) matrices were reinforced with 5, 10 and 15 %wt hydroxyapatite (HA)

Ashkan Heidarkhan Tehrani; Ali Zadhoush; Saeed Karbasi

2010-01-01

68

Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior  

Microsoft Academic Search

The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results

J. L. Xu; K. A. Khor; Y. W. Gu; R. Kumar; P. Cheang

2005-01-01

69

Synthesis and in vitro evaluation of hydroxyapatite with controlled morphology  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) ceramics have been used as bone-repairing materials. Particles in HA ceramics show different properties depending on their compositions and morphologies. It is expected that the control of the composition and morphology contributes to improvement of biological properties of HA ceramics. In order to reveal the effect of the composition and morphology, the HA ceramics composed of rod-shaped or plate-shaped particles with calcium-deficient composition were prepared by the hydrothermal process. The in vitro evaluation, simulated body fluid (SBF) soaking test, was then conducted for these samples. The calcium-deficient HA ceramics composed of rod-shaped or plate-shaped particles were reacted with SBF and incorporated calcium and phosphate ions from SBF. This implies that these HA ceramics show high affinity to bone in the body.

Kamitakahara, M.; Saito, T.; Ioku, K.

2012-01-01

70

Citric Acid-based Hydroxyapatite Composite Scaffolds Enhance Calvarial Regeneration.  

PubMed

Citric acid-based polymer/hydroxyapatite composites (CABP-HAs) are a novel class of biomimetic composites that have recently attracted significant attention in tissue engineering. The objective of this study was to compare the efficacy of using two different CABP-HAs, poly (1,8-octanediol citrate)-click-HA (POC-Click-HA) and crosslinked urethane-doped polyester-HA (CUPE-HA) as an alternative to autologous tissue grafts in the repair of skeletal defects. CABP-HA disc-shaped scaffolds (65 wt.-% HA with 70% porosity) were used as bare implants without the addition of growth factors or cells to renovate 4?mm diameter rat calvarial defects (n = 72, n = 18 per group). Defects were either left empty (negative control group), or treated with CUPE-HA scaffolds, POC-Click-HA scaffolds, or autologous bone grafts (AB group). Radiological and histological data showed a significant enhancement of osteogenesis in defects treated with CUPE-HA scaffolds when compared to POC-Click-HA scaffolds. Both, POC-Click-HA and CUPE-HA scaffolds, resulted in enhanced bone mineral density, trabecular thickness, and angiogenesis when compared to the control groups at 1, 3, and 6 months post-trauma. These results show the potential of CABP-HA bare implants as biocompatible, osteogenic, and off-shelf-available options in the repair of orthopedic defects. PMID:25372769

Sun, Dawei; Chen, Yuhui; Tran, Richard T; Xu, Song; Xie, Denghui; Jia, Chunhong; Wang, Yuchen; Guo, Ying; Zhang, Zhongmin; Guo, Jinshan; Yang, Jian; Jin, Dadi; Bai, Xiaochun

2014-01-01

71

Citric Acid-based Hydroxyapatite Composite Scaffolds Enhance Calvarial Regeneration  

PubMed Central

Citric acid-based polymer/hydroxyapatite composites (CABP-HAs) are a novel class of biomimetic composites that have recently attracted significant attention in tissue engineering. The objective of this study was to compare the efficacy of using two different CABP-HAs, poly (1,8-octanediol citrate)-click-HA (POC-Click-HA) and crosslinked urethane-doped polyester-HA (CUPE-HA) as an alternative to autologous tissue grafts in the repair of skeletal defects. CABP-HA disc-shaped scaffolds (65 wt.-% HA with 70% porosity) were used as bare implants without the addition of growth factors or cells to renovate 4?mm diameter rat calvarial defects (n = 72, n = 18 per group). Defects were either left empty (negative control group), or treated with CUPE-HA scaffolds, POC-Click-HA scaffolds, or autologous bone grafts (AB group). Radiological and histological data showed a significant enhancement of osteogenesis in defects treated with CUPE-HA scaffolds when compared to POC-Click-HA scaffolds. Both, POC-Click-HA and CUPE-HA scaffolds, resulted in enhanced bone mineral density, trabecular thickness, and angiogenesis when compared to the control groups at 1, 3, and 6 months post-trauma. These results show the potential of CABP-HA bare implants as biocompatible, osteogenic, and off-shelf-available options in the repair of orthopedic defects. PMID:25372769

Sun, Dawei; Chen, Yuhui; Tran, Richard T.; Xu, Song; Xie, Denghui; Jia, Chunhong; Wang, Yuchen; Guo, Ying; Zhang, Zhongmin; Guo, Jinshan; Yang, Jian; Jin, Dadi; Bai, Xiaochun

2014-01-01

72

Novel selenium-doped hydroxyapatite coatings for biomedical applications.  

PubMed

Nowadays there is a short-term need of investigating in orthopedic implants with a greater functionality, including an improved osseointegration and also antibacterial properties. The coating of metallic implants with hydroxyapatite (HA) remains to be the main proposal, but superior quality HA coatings with compositions closer to natural bone apatites, including carbonates, trace elements are required. Selenium is an essential nutrient in biological tissues and, at the same time, it also presents antibacterial properties. A pioneering study on the fabrication of selenium-doped carbonated hydroxyapatite (iHA:Se) coatings by Pulsed Laser Deposition (PLD) is presented. Different proportions of selenium were incorporated to obtain the iHA:Se coatings. Their physicochemical characterization, performed by SEM/EDS, FTIR, FT-Raman, Interferometric Profilometry and XPS, revealed typical columnar growth of HA in globular aggregates and the efficient incorporation of selenium into the HA coatings by the, most probably, substitution of SeO(3)(2-) groups in the CO(3)(2-) sites. Biological evaluation illustrated the absence of cytotoxicity when an amount of 0.6 at.% of Se was added to the iHA:Se coatings and excellent proliferation of the MC3T3-E1 preosteoblasts. Antibacterial properties were also proved with the inhibition of P. aeruginosa and S. aureus from establishing bacterial biofilms. PMID:22968925

Rodríguez-Valencia, C; López-Álvarez, M; Cochón-Cores, B; Pereiro, I; Serra, J; González, P

2013-03-01

73

A homogenous CS\\/NaCMC\\/nHA polyelectrolyte complex membrane prepared by gradual electrostatic assembling  

Microsoft Academic Search

A homogenous membrane composed of chitosan (CS), sodium carboxymethyl cellulose (NaCMC) and nano hydroxyapatite (n-HA) was\\u000a prepared by a gradual electrostatic assembling (GEA) method. The physical and chemical properties of the membranes with different\\u000a n-HA contents and CS\\/NaCMC ratios were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy,\\u000a X-ray diffraction and mechanical test. The schematic formation mechanism of the

Hong Jiang; Yi Zuo; Lin Cheng; Hongli Wang; Aiqun Gu; Yubao Li

2011-01-01

74

THE EXPERIMENT OF PLASMA-SPRAYED HA COATINGS ON CARBON\\/CARBON COMPOSITES IN BONE  

Microsoft Academic Search

This paper dealt with plasma-sprayed hydroxyapatite (HA) coatings on carbon\\/carbon composites (C\\/C) and the implantation was carried out in rabbits. Ninety days after the implantation, we found that such materials were favorable for health and no cytotoxic effects were discovered. The histological observation of osteogenic response of HA-coated C\\/C showed that the osteoplaque had scansorially grown along the surface of

NING CAO; QUAN-SHENG MA; JIN-LING SUI; QIANG-XIU WANG; YU-PENG LÜ; YAN-MEI CHEN; MU-SEN LI

2006-01-01

75

HDPE-HA composites synthetized by in situ polymerization with different filler content  

NASA Astrophysics Data System (ADS)

In Situ ethylene polymerization was used to synthesize high density polyethylene - hydroxyapatite (HDPE-HA) composites, employing Cp2ZrCl2/MAO as catalytic system. A good dispersion of HA into the HDPE matrix was obtained when the following synthesis conditions were combined: high stirring velocities (2000 rpm), low quantities of solvent (100 mL), and 10 °C. Under these conditions different filler content was used to synthetized HDPE-HA composites. An interaction between HA and HDPE was obtained by FTIR. On the other hand, thermal analysis indicated that no significant differences were observed between HDPE and the composites.

Hermán, V.; Karam, A.; Albano, C.; Romero, K.; González, G.

2012-07-01

76

Silicate-doped hydroxyapatite and its promotive effect on bone mineralization  

NASA Astrophysics Data System (ADS)

Bone defect is one of the most common diseases in clinic. Existing therapeutic approaches have encountered many problems, such as lack of autogenous allogeneic bone and immunological rejection to allogeneic implant. Synthetic hydroxyapatite (HA) provided solutions for bone repair, since the HA is the main inorganic component of animals' bone. However, HA has good biocompatibility, but does not possess osteogenic capability, which is of significance for modern bone repair materials. Si is an essential trace element in bone tissue, and it has been demonstrated to be able to promote bone formation. Therefore, silicate-doped hydroxyapatite (Si-HA) may serve as a promising material for bone repair, and promote bone regeneration in the repair. The current review discusses development of Si-HA, focusing on its preparation and characterization, in vitro and in vivo evaluations of the material, positive effect of Si-HA on promoting bone formation in clinical applications, and molecular mechanism investigation of such promotive effect.

Qiu, Zhi-Ye; Noh, In-Sup; Zhang, Sheng-Min

2013-03-01

77

Dissolution of calcium-deficient hydroxyapatite synthesized at different conditions  

Microsoft Academic Search

The dissolution characteristics of several calcium-deficient hydroxyapatites (HA) have been investigated. Eleven samples were produced by varying synthesis parameters like temperature, pH, digestion time, reagent concentration and velocity of addition. Powder characterization was conducted using X-ray diffraction. Sample crystallinity was variable and samples examined by transmission electron microscopy showed acicular or plate-like morphology. After sample dissolution in Milli-Q water for

Elena Mavropoulos; Alexandre M. Rossi; Nilce C. C. da Rocha; Gloria A. Soares; Josino C. Moreira; Gustavo T. Moure

2003-01-01

78

Improved mechanical properties of hydroxyapatite whisker-reinforced poly(L-lactic acid) scaffold by surface modification of hydroxyapatite.  

PubMed

To improve the mechanical properties of porous hydroxyapatite/poly(L-lactic acid) (HA/PLLA) composites, HA whiskers with high crystallinity and high aspect ratio were synthesized. HA whiskers were modified with ?-aminopropyltriethoxysilane (APTES) to improve the interface between HA whiskers and PLLA. The composite scaffold consists of a porous PLLA matrix with HA whiskers distributed homogeneously. The morphology and the distributions of pore sizes of PLLA scaffold was not influenced by introducing HA whiskers, while the mechanical properties were improved. Both the compressive strength and compressive modulus were increased with the weight ratio of APTES-modified HA whiskers up to 30 wt.%, but only up to 15 wt.% for non-modified HA whiskers. With more than 15 wt.% HA whiskers, the mechanical properties of HA/PLLA scaffold were better improved with APTES-modified HA whiskers than non-modified. The HA whisker/PLLA scaffold with high porosity and improved mechanical properties is attractive in the application of tissue engineering. PMID:24411368

Fang, Zhou; Feng, Qingling

2014-02-01

79

Influences of magnetized hydroxyapatite on the growth behaviors of osteoblasts and the mechanism from molecular dynamics simulation.  

PubMed

To investigate the influence of magnetized hydroxyapatite on the growth and differentiation of osteoblasts, hydroxyapatite (HA) and magnetized hydroxyapatite (mHA) were synthesized and characterized. The cell viability, differentiation, and morphologies of osteoblasts were investigated in vitro, respectively. The results showed that compared to HA, cells cultured with mHA had better cell viability, and both HA and mHA were beneficial to the early differentiation of osteoblasts. Furthermore, the interaction mechanism between mHA and osteoblasts was elucidated using a molecular dynamics simulation. The simulation results indicated that when cultured with osteoblasts, HA adsorbed bovine serum protein onto its surface from the medium immediately, which was beneficial to the adhesion and proliferation of osteoblasts. The main driving force for the adsorption of bovine serum was the electronic properties of HA crystal faces. The (211) crystal face of HA had the highest electron density among its all crystal faces, thus mainly contributing to the protein adsorption of HA. Nevertheless, the (211) crystal face of mHA still had a relatively higher electron density than that of HA, thus possessing better protein adsorption than that of HA, and in turn promoting the biological functions of osteoblasts. PMID:23910273

Yang, Weihu; Xi, Xingfeng; Fang, Jiajia; Liu, Peng; Cai, Kaiyong

2013-10-01

80

Hydroxyapatite coating on titanium by a low energy plasma spraying mini-gun  

Microsoft Academic Search

Plasma-sprayed hydroxyapatite (HA) coatings are used on metallic implants to improve osseointegration and bone growth. The purpose of this work was to determine the microstructure and composition of HA coatings obtained with a newly developed low energy plasma spray mini-gun employing an HA feedstock powder with smaller granulometry than that commonly used.The microstructure and the phase composition of the coatings

I. Demnati; M. Parco; D. Grossin; I. Fagoaga; C. Drouet; G. Barykin; C. Combes; I. Braceras; S. Goncalves; C. Rey

81

Hydroxyapatite coating on titanium substrate with titania buffer layer processed by sol–gel method  

Microsoft Academic Search

Hydroxyapatite (HA) was coated onto a titanium (Ti) substrate with the insertion of a titania (TiO2) buffer layer by the sol–gel method. The HA layer was employed to enhance the bioactivity and osteoconductivity of the Ti substrate, and the TiO2 buffer layer was inserted to improve the bonding strength between the HA layer and Ti substrate, as well as to

Hae-Won Kim; Young-Hag Koh; Long-Hao Li; Sook Lee; Hyoun-Ee Kim

2004-01-01

82

Titanium dioxide reinforced hydroxyapatite coatings deposited by high velocity oxy-fuel (HVOF) spray  

Microsoft Academic Search

Hydroxyapatite (HA) coatings with titania addition were produced by the high velocity oxy-fuel (HVOF) spray process. Mechanical properties of the as-sprayed coatings in terms of adhesive strength, shear strength and fracture toughness were investigated to reveal the effect of the titania reinforcement on HA. Qualitative phase analysis with X-ray diffraction (XRD) showed that mutual chemical reaction between TiO2 and HA,

H. Li; K. A. Khor; P. Cheang

2002-01-01

83

Adsorption of chlorhexidine on synthetic hydroxyapatite and in vitro biological activity  

Microsoft Academic Search

The kinetic of chlorhexidine digluconate (CHXDG) uptake from aqueous solution by hydroxyapatite (HA) was investigated by ultraviolet (UV) analysis performed in HA powder (UV-solid) after the CHX adsorption. Adsorption isotherm of chlorhexidine (CHX) uptake was modeled by a combination of Languimir and Langmuir–Freundlich mechanisms. Strong molecule–molecule interactions and positive cooperativity predominated in the surface when CHX concentration was above 8.6?gCHX\\/mgHA.

Carlos A. Soriano de Souza; Ana Paula V. Colombo; Renata M. Souto; Carina M. Silva-Boghossian; Jose M. Granjeiro; Gutemberg G. Alves; Alexandre M. Rossi; Maria Helena M. Rocha-Leão

2011-01-01

84

Evaluation and characterization of nanostructure hydroxyapatite powder prepared by simple sol–gel method  

Microsoft Academic Search

Many attempts have been focused on preparing of synthetic hydroxyapatite (HA), which closely resembles bone apatite and exhibits excellent osteoconductivity. Low temperature formation and fusion of the apatite crystals have been the main contributions of the sol–gel process in comparison with conventional methods for HA powder synthesis. This paper describes the synthesis of nano-HA particles via a sol–gel method. Nanocrystalline

M. H. Fathi; A. Hanifi

2007-01-01

85

Hydroxyapatite-reinforced collagen tissue engineering scaffolds  

NASA Astrophysics Data System (ADS)

Scaffolds have been fabricated from a wide variety of materials and most have showed some success, either as bone graft substitutes or as tissue engineering scaffolds. However, all current scaffold compositions and architectures suffer from one or more flaws including poor mechanical properties, lack of biological response, nondegradability, or a scaffold architecture not conducive to osteointegration. Biomimetic approaches to scaffold design using the two main components of bone tissue, collagen and hydroxyapatite, resulted in scaffolds with superior biological properties but relatively poor mechanical properties and scaffold architecture. It was hypothesized that by optimizing scaffold composition and architecture, HA-collagen bone tissue engineering scaffolds could provide both an excellent biological response along with improved structural properties. The mechanical properties of freeze-dried HA-collagen scaffolds, the most common type of porous HA-collagen material, were first shown to be increased by the addition of HA reinforcements, but scaffold stiffness still fell far short of the desired range. Based on limitations inherent in the freeze-dried process, a new type of leached-porogen scaffold fabrication process was developed. Proof-of-concept scaffolds demonstrated the feasibility of producing leached-porogen HA-collagen materials, and the scaffold architecture was optimized though careful selection of porogen particle size and shape along with an improved crosslinking technique. The final scaffolds exhibited substantially increased compressive modulus compared to previous types HA-collagen scaffolds, while the porosity, pore size, and scaffold permeability were tailored to be suitable for bone tissue ingrowth. An in vitro study demonstrated the capacity of the leached-porogen scaffolds to serve as a substrate for the differentiation of osteoblasts and subsequent production of new bone tissue. The new leached-porogen scaffold HA-collagen scaffolds were shown to have potential as a highly tailorable bone tissue engineering scaffold with a unique combination of biological, mechanical, and structural properties.

Kane, Robert J.

86

The beneficial effect of hydroxyapatite lasts  

PubMed Central

Background and purpose In contrast to early migration, the long-term migration of hydroxyapatite- (HA-) coated tibial components in TKA has been scantily reported. This randomized controlled trial investigated the long-term migration measured by radiostereometric analysis (RSA) of HA-coated, uncoated, and cemented tibial components in TKA. Patients and methods 68 knees were randomized to HA-coated (n = 24), uncoated (n = 20), and cemented (n = 24) components. All knees were prospectively followed for 11–16 years, or until death or revision. RSA was used to evaluate migration at yearly intervals. Clinical and radiographic evaluation was according to the Knee Society system. A generalized linear mixed model (GLMM, adjusted for age, sex, diagnosis, revisions, and BMI) was used to take into account the repeated-measurement design. Results The present study involved 742 RSA analyses. The mean migration at 10 years was 1.66 mm for HA, 2.25 mm for uncoated and 0.79 mm for the cemented group (p < 0.001). The reduction of migration by HA as compared to uncoated components was most pronounced for subsidence and external rotation. 3 tibial components were revised for aseptic loosening (2 uncoated and 1 cemented), 3 for septic loosening (2 uncoated and 1 cemented), and 1 for instability (HA-coated). 2 of these cases were revised for secondary loosening after a period of stability: 1 case of osteolysis and 1 case of late infection. There were no statistically significant differences between the fixation groups regarding clinical or radiographic scores. Interpretation HA reduces migration of uncemented tibial components. This beneficial effect lasts for more than 10 years. Cemented components showed the lowest migration. Longitudinal follow-up of TKA with RSA allows early detection of secondary loosening. PMID:22329667

2012-01-01

87

[Hydroxyapatite bioactive coating on carbon/carbon composites].  

PubMed

A simple plasma spraying method was employed in coating hydroxyapaptite (HA) on to carbon/carbon composites (C/C composites). The morphology of the coating was examined under scanning electron microscope (SEM). The phase constitutions of the HA coating were determined by X-ray diffractometer (XRD). The shear strength of the HA coating-C/C composite substrates was detected. A hydroxyapatite coating with rough surface was observed. A considerable amount of amorphous phase appeared as a result from the coating process, which could be transformed into the morphous phase crystalline HA after subsequent heat treatment. The shear strength between the HA coating and C/C composite substrates was 7.15 MPa. PMID:15884528

Sui, Jinling; Li, Musen; Lü, Yupeng; Bai, Yunqiang

2005-04-01

88

Study of BSA protein adsorption/release on hydroxyapatite nanoparticles  

NASA Astrophysics Data System (ADS)

Three different spherical, rod and fibrous morphologies of hydroxyapatite (HA) nanoparticles have been prepared through control over the processing parameters like temperature, pH and Ca:P ratio. Protein adsorption/release with respect to HA nanoparticle morphologies are investigated using model protein bovine serum albumin (BSA). BSA adsorption on HA nanoparticles follows Langmuir adsorption isotherm. Thermal analysis and FT-IR spectrum confirms the BSA adhesion and retention of their secondary structure. High surface area with high Ca:P ratio nanorod adsorbs relatively more amount (28 mg BSA/gm of nanorod HA) of BSA within 48 h in comparison with counterpart fibroid and spherical morphologies. Slow and steady BSA release (75 wt% of adsorbed BSA in 96 h) from nanorod HA is found as futuristic drug delivery media.

Swain, Sanjaya Kumar; Sarkar, Debasish

2013-12-01

89

Hyaluronic acid as an internal phase additive to obtain ofloxacin/PLGA microsphere by double emulsion method.  

PubMed

Hyaluronic acid (HA) was used as an internal phase additive to improve the loading efficiency of ofloxacin, a hydrophilic drug encapsulated by hydrophobic polylactic-co-glycolic acid (PLGA) materials, through a double emulsion (water-in-oil-in-water) solvent extraction/evaporation method. Results from laser distribution analysis show that polyelectrolyte additives have low impact on the average particle size and distribution of the microspheres. The negatively charged HA increases the drug loading efficiency as well as the amount of HA in microspheres. Burst release can be observed in the groups with the polyelectrolyte additives. The release rate decreases with the amount of HA inside the microspheres in all negatively charged polyelectrolyte-added microsphere groups. PMID:24211960

Wu, Gang; Chen, Long; Li, Hong; Wang, Ying-jun

2014-01-01

90

Pressureless sintering of dense hydroxyapatite–zirconia composites  

Microsoft Academic Search

Hydroxyapatite (HA)–TZP (2.5 mol% Y2O3) containing 2, 5, 7.5 and 10 wt% TZP were prepared using calcium nitrate, diammonium hydrogen orthophosphate, zirconium oxychloride\\u000a and yttrium nitrate. The composite powder was prepared by a reverse strike precipitation method at a pH of 10.5. The precipitates\\u000a after aging and washing were calcined at 850°C to yield fine crystallites of HA and TZP. TEM study

Y. Nayak; R. P. Rana; S. K. Pratihar; S. Bhattacharyya

2008-01-01

91

Hydroxyapatite grafted carbon nanotubes and graphene nanosheets: Promising bone implant materials  

NASA Astrophysics Data System (ADS)

In the present study, hydroxyapatite (HA) was successfully grafted to carboxylated carbon nanotubes (CNTs) and graphene nanosheets. The HA grafted CNTs and HA-graphene nanosheets were characterized using FT-IR, TGA, SEM and X-ray diffraction. The HA grafted CNTs and graphene nanosheets (CNTs-HA and Gr-HA) were further used to examine the proliferation and differentiation rate of temperature-sensitive human fetal osteoblastic cell line (hFOB 1.19). Total protein assays and western blot analysis of osteocalcin expression were used as indicators of cell proliferation and differentiation. Results indicated that hFOB 1.19 cells proliferate and differentiate well in treatment media containing CNTs-HA and graphene-HA. Both CNTs-HA and graphene-HA could be promising nanomaterials for use as scaffolds in bone tissue engineering.

Oyefusi, Adebola; Olanipekun, Opeyemi; Neelgund, Gururaj M.; Peterson, Deforest; Stone, Julia M.; Williams, Ebonee; Carson, Laura; Regisford, Gloria; Oki, Aderemi

2014-11-01

92

In vivo study of chitosan-natural nano hydroxyapatite scaffolds for bone tissue regeneration.  

PubMed

Significant development has been achieved with bioceramics and biopolymer scaffolds in the construction of artificial bone. In the present study, we have developed and compared chitosan-micro hydroxyapatite (chitosan-mHA) and chitosan-nano hydroxyapatite (chitosan-nHA) scaffolds as bone graft substitutes. The biocompatibility and cell proliferation of the prepared scaffolds were checked with preosteoblast (MC3T3-E1) cells. Total Volume (TV), bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were found to be higher in chitosan-nHA than chitosan-mHA scaffold. Hence, we suggest that chitosan-nHA scaffold could be a promising biomaterial for bone tissue engineering. PMID:24705167

Lee, Jong Seo; Baek, Sang Dae; Venkatesan, Jayachandran; Bhatnagar, Ira; Chang, Hee Kyung; Kim, Hui Taek; Kim, Se-Kwon

2014-06-01

93

Effect of n-HA with different surface-modified on the properties of n-HA/PLGA composite  

NASA Astrophysics Data System (ADS)

Three different surface modification methods for nano-hydroxyapatite (n-HA) of stearic acid, grafted with L-lactide, combining stearic acid and surface-grafting L-lactic were adopted, respectively. The surface modification reaction and the effect of different methods were evaluated by Fourier transformation infrared (FTIR), X-ray photoelectron spectra (XPS), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM). The results showed that n-HA surfaces were all successful modified, and the modification method of combining stearic acid and surface-grafting L-lactic had the greatest grafting amount and the best dispersion among the three modification methods. Then, the n-HA with three different surface modification and unmodified n-HA were introduced into PLGA, respectively, and a serials of n-HA/PLGA composites with 3% n-HA amount in weight were prepared by solution mixing, and the properties of n-HA/PLGA composites were also investigated by electromechanical universal tester and scanning electron microscope(SEM), comparing with PLGA. The results showed that the n-HA/PLGA composite with the n-HA surface modified by combining stearic acid and surface-grafting L-lactic had the highest bending strength and the best dispersion and interfacial adhesion among the three different modification methods, suggesting the surface modification of combining stearic acid and surface-grafting L-lactic was the most ideal method in this study, which has a great deal of enhancement of bending strength than PLGA, and it would be potential to be used in the field of bone fracture internal fixation in future.

Liuyun, Jiang; Chengdong, Xiong; Dongliang, Chen; Lixin, Jiang; xiubing, Pang

2012-10-01

94

Effect of Hydrothermal Treatment on Sinterability of Hydroxyapatite  

SciTech Connect

Calcium hydroxyapatite, Ca10(PO4)6(OH)2:HA, is the inorganic principle component of natural bones and teeth. It has been already suggested that the amount of OH ion in the crystal structure of HA is closely related to the biocompatibility. The amount of OH ion in current HA, however, has not been controlled. In order to prepare more functional HA ceramics, the amount of OH ion must be controlled. In this study, HA ceramics with different OH amount were prepared from fine HA crystals by spark plasma sintering (SPS). Fine powder of HA was treated hydrothermally at 200 deg. C for 24 h with pH 10 NH3 aqueous solution. The samples were pressed uniaxialy under 60 MPa, and then they were SPS at 800 deg. C, 900 deg. C and 1000 deg. C for 10 min with the heating rate of 25 deg. C{center_dot}min-1. No phases other than HA were revealed by XRD for the starting samples after hydrothermal treatment and samples after sintering by SPS at 800 deg. C, 900 deg. C and 1000 deg. C for 10 min. The quantity of OH ion in HA ceramics sintered by SPS was decreased with increasing temperature of sintering. Transparent HA ceramics were prepared by SPS at 900 deg. C and 1000 deg. C.

Kawagoe, D. [Institution of Fluid Science, Tohoku University, Aoba 20 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Fujimori, H.; Goto, S. [Division of Applied Medical Engineering Science, Graduate School of Medicine, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611 (Japan); Yamasaki, N.; Ioku, K. [Graduate School of Environmental Studies, Tohoku University, Aoba 20 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2006-05-15

95

Doped zinc oxide microspheres  

DOEpatents

A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel.

Arnold, Jr., Wesley D. (Oak Ridge, TN); Bond, Walter D. (Knoxville, TN); Lauf, Robert J. (Oak Ridge, TN)

1993-01-01

96

Doped zinc oxide microspheres  

DOEpatents

A new composition and method of making same for a doped zinc oxide microsphere and articles made therefrom for use in an electrical surge arrestor which has increased solid content, uniform grain size and is in the form of a gel. 4 figures.

Arnold, W.D. Jr.; Bond, W.D.; Lauf, R.J.

1993-12-14

97

Emulsion cross-linked chitosan/nanohydroxyapatite microspheres for controlled release of alendronate.  

PubMed

Sustained delivery of growth factors has emerged as an essential requirement for bone tissue engineering applications for the treatment of various kinds of bone defects. Chitosan (CH) has attracted particular attention for drug delivery and bone tissue engineering because of its favorable biocompatibility and biodegradability. In this study, a composite microsphere system containing CH and nanohydroxyapatite (nHA)-alendronate (AL) particles was fabricated by employing both emulsification and cross-linking strategies. The microspheres were characterized for their surface morphology, composition, size distribution, drug loading efficiency and release properties. The results showed that loading efficiency and sustained release of hydrophilic AL were significantly improved, which is ideal for locally sustained release in the bone microenvironment. In vitro osteogenic studies showed that the microspheres could enhance the osteogenic activity of rabbit adipose-derived stem cells. In conclusion, the CH/nHA-AL composite microspheres exhibit promising properties as a candidate for local treatment for bone defects. PMID:25080396

Wu, Hongwei; Xu, Yan; Liu, Gengyan; Ling, Jianghong; Dash, Biraja C; Ruan, Jianming; Zhang, Chaoyue

2014-12-01

98

Hydroxyapatite for Keratoprosthesis Biointegration  

PubMed Central

Purpose. Integration of keratoprosthesis with the surrounding cornea is very important in preventing bacterial invasion, which may cause ocular injury. Here the authors investigated whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) biointegration, using polymethyl methacrylate (PMMA)—the principal component of the Boston KPro—as a model polymer. Methods. HAp coatings were induced on PMMA discs after treatment with concentrated NaOH and coating with poly-dopamine (PDA) or polydopamine and then with 11-mercaptoundecanoic acid (11-MUA). Coatings were characterized chemically (Fourier transform infrared spectroscopy [FTIR], energy dispersive X-ray spectroscopy [EDX]) and morphologically (SEM) and were used as substrates for keratocyte growth in vitro. Cylinders of coated PMMA were implanted in porcine corneas ex vivo for 2 weeks, and the force required to pull them out was measured. The inflammatory reaction to coated discs was assessed in the rabbit cornea in vivo. Results. FTIR of the coatings showed absorption bands characteristic of phosphate groups, and EDX showed that the Ca/P ratios were close to those of HAp. By SEM, each method resulted in morphologically distinct HAp films; the 11-MUA group had the most uniform coating. The hydroxyapatite coatings caused comparable enhancement of keratocyte proliferation compared with unmodified PMMA surfaces. HAp coating significantly increased the force and work required to pull PMMA cylinders out of porcine corneas ex vivo. HAp coating of implants reduced the inflammatory response around the PMMA implants in vivo. Conclusions. These results are encouraging for the potential of HAp-coated surfaces for use in keratoprostheses. PMID:21849419

Wang, Liqiang; Jeong, Kyung Jae; Chiang, Homer H.; Zurakowski, David; Behlau, Irmgard; Chodosh, James; Dohlman, Claes H.; Langer, Robert

2011-01-01

99

Synthesis and characterization of wool keratin/hydroxyapatite nanocomposite.  

PubMed

Taking the inspiration from the biomineral, the wool keratin was selected to modulate the assembly of nanosized hydroxyapatite (HA) crystals via a coprecipitation method. A series of keratin/HA nanocomposite with different ratios were synthesized by adjusting the concentrations of keratin solutions and calcium phosphate and their final components were detected by thermogravimetric analysis (TGA). The transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed that keratin in the composite decreased the crystallinity of HA. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to examine the chemical and surface structure of the composites. In vitro biocompatibility results revealed that cells showed better viability on keratin/HA composites which have a ratio of organics and inorganics similar to that of natural bones. PMID:22438339

Li, Jiashen; Liu, Xuan; Zhang, Jing; Zhang, Yu; Han, Yanxia; Hu, Junyan; Li, Yi

2012-05-01

100

Preparation and characterization of nano-hydroxyapatite within chitosan matrix.  

PubMed

Nano-composites that show some features of natural bone both in composition and in microstructure have been prepared by in situ precipitation method. Apatite phase has been prepared from cost-effective precursors (calcite and urea phosphate) within chitosan (CS) matrix dissolved in aqueous acetic acid solution. The compositional and morphological properties of composites were studied by means of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Depending on the reaction conditions (temperature, reaction time, glucose addition and pH control) in addition to hydroxyapatite (HA) as a major phase, octacalcium hydrogen phosphate pentahydrate (OCP) and dicalcium phosphate anhydrate (DCPD) were formed as shown by XRD and FTIR. Crystallite lengths of precipitated HA estimated by Scherrer's equation were between 20 and 30 nm. A fibrous morphology (~400 nm) of HA observed by TEM indicates that HA nucleates on chitosan chains. PMID:24094157

Rogina, A; Ivankovi?, M; Ivankovi?, H

2013-12-01

101

Cytotoxicity and genotoxicity property of hydroxyapatite-mullite eluates.  

PubMed

Long-term biomedical applications of implant materials may cause osteolysis, aseptic losing and toxicity. Therefore, we investigated the cytotoxic and genotoxic potential of hydroxyapatite (HA) mullite eluates in L929 mouse fibroblast cells. The spark plasma sintered HA-20% mullite biocomposite (HA20M) were ground using mortar and pestle as well as ball milling. The cells were exposed for 6 h to varying concentrations (10, 25, 50, 75 and 100%) of the eluates of HA-20% mullite (87 nm), HA (171 nm) and mullite (154 nm). The scanning electron microscopy and MTT assay revealed the concentration dependent toxicity of H20M eluate at and above 50%. The analysis of the DNA damaging potential of HA, mullite and HA20M eluates using Comet assay demonstrated a significant DNA damage by HA20M which was largely related to the presence of mullite. The results collectively demonstrate the cytotoxic and genotoxic potential of HA20M eluate in L929 cells is dependent on particle size, concentration and composition. PMID:21485810

Kalmodia, Sushma; Sharma, Vyom; Pandey, Alok K; Dhawan, Alok; Basu, Bikramjit

2011-02-01

102

Hepatotoxicity and liver injury induced by hydroxyapatite nanoparticles.  

PubMed

As hydroxyapatite nanoparticles (HA NPs) are increasingly used in biomedical and biotechnological fields, risk assessment of HA NPs has attracted extensive attention. Nevertheless, little is known about the potential adverse effects of HA NPs on normal hepatocytes and the liver. In the present study, we conducted an in vitro study in which 80-nm HA NPs were incubated with normal Buffalo rat liver (BRL) cells. By analyzing the changes in cell viability, apoptosis/necrosis and the mitogen-activated protein kinase (MAPK) signaling pathway, we investigated the cytotoxicity and potential mechanism of HA NPs in hepatocytes. Furthermore, we used the serum hematology and histopathology examinations to explore the in vivo effects of HA NPs on the structure and function of the liver. Our results showed that exposure to HA NPs at a concentration above 200?µg?ml(-1) decreased cell viability, increased levels of lactate dehydrogenase (LDH) leakage, induced apoptosis and necrosis, and triggered the MAPK signaling pathway in BRL cells in a dose-dependent manner. Moreover, our in vivo study indicated that HA NPs increased the white blood cell count (WBC) and the levels of tumor necrosis factor-? (TNF-?), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the serum, caused inflammatory cell infiltration at the portal area in the liver, and induced hepatic oxidative stress with elevated levels of hydrogen peroxide (H2 O2 ) and malondialdehyde (MDA). These data demonstrate that at certain concentrations, 80-nm HA NPs cause hepatotoxicity and liver injury. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25225040

Chen, Qingqing; Xue, Yang; Sun, Jiao

2014-11-01

103

Carbon nanotubes/hydroxyapatite nanocomposites fabricated by spark plasma sintering for bonegraft applications  

NASA Astrophysics Data System (ADS)

Multi-wall carbon nanotubes/hydroxyapatite (MWCNTs/HA) composites with 20%, 40% and 60% HA were successfully fabricated at 1200 °C and 120 MPa by spark plasma sintering (SPS). Scanning electron microscope (SEM) observations showed that MWCNTs/HA composites kept the nanostructure of MWCNTs after SPS treatment. The bulk density of the MWCNTs/HA composites was increased by the addition of HA. However, the Vickers hardness, porosity, Young's modulus, flexure strength and compression strength of the MWCNTs/HA composites were decreased with increasing content of HA. To test their biocompatibility, the MWCNTs/40% HA composites were inserted into rat femur. The in vivo reaction of four weeks showed that the composites possessed better osseointegration compared to pure MWCNTs. The results indicated that the MWCNTs/HA composites have potential for a wide variety of bonegraft applications in the future.

Wang, Wei; Zhu, Yuhe; Watari, Fumio; Liao, Susan; Yokoyama, Atsuro; Omori, Mamoru; Ai, Hongjun; Cui, FuZhai

2012-12-01

104

Porous microsphere and its applications  

PubMed Central

Porous microspheres have drawn great attention in the last two decades for their potential applications in many fields, such as carriers for drugs, absorption and desorption of substances, pulmonary drug delivery, and tissue regeneration. The application of porous microspheres has become a feasible way to address existing problems. In this essay, we give a brief introduction of the porous microsphere, its characteristics, preparation methods, applications, and a brief summary of existing problems and research tendencies. PMID:23515359

Cai, Yunpeng; Chen, Yinghui; Hong, Xiaoyun; Liu, Zhenguo; Yuan, Weien

2013-01-01

105

Phase transformation behaviour of hydroxyapatite foams subject to heat treatment.  

PubMed

This study examined the relationship between sintering and phase transformation behaviour in hydroxyapatite (HA). Pellets and replicated foams were sintered at five different temperatures ranging from 1350 degrees C to 1550 degrees C. Hydroxyapatite remained as the major phase in all the samples studied. In the pellets, sintering took place prior to the phase transformation which occurs primarily at the surface. This created damage that extended into the interior of the pellet above 1400 degrees C. In contrast, the foams transformed at lower temperatures due to the higher surface area. This did not create damage in the foam. The differences in the foams and the pellets are discussed in terms of sintering and phase transformation behaviour. PMID:20057016

Finoli, A; McKeel, D; Gerlach, J; Nettleship, I

2010-02-01

106

Dip Coating of Calcium Hydroxyapatite on Ti-6Al-4V Substrates and A. Cuneyt Tas*,  

E-print Network

Dip Coating of Calcium Hydroxyapatite on Ti-6Al-4V Substrates Bora Mavis and A. Cu¨neyt Tas biocompatibility with bone, metal implants made of Ti-6Al-4V are often coated with bioceramics. Dip-coating is focused on the development of recipes of appropriate solutions for the dip coating of HA on Ti-6Al-4V

Tas, A. Cuneyt

107

Selective laser melting of a stainless steel and hydroxyapatite composite for load-bearing implant development  

Microsoft Academic Search

Selective laser melting (SLM) is emerged as a new manufacturing technique to directly fabricate customised implants using metallic materials. This technique is also capable of processing powder mixtures to generate advanced composites offering desirable properties. In this research, the SLM technique was used to directly fabricate hydroxyapatite (HA) and 316L stainless steel (SS) powders mixture with an objective to develop

L. Hao; S. Dadbakhsh; O. Seaman; M. Felstead

2009-01-01

108

Development of metal\\/hydroxyapatite composite surface coatings. Ph.D. Thesis  

Microsoft Academic Search

Metal\\/ceramic composites containing calcium phosphates have shown considerable success in enhancing bone growth into implants, thereby providing cementless fixation. Calcium phosphate occurs in various phases. The extent of compatibility of the composites to the hosts depend upon the phase of the calcium phosphate. A crystalline phase known as hydroxyapatite (HA) which naturally occurs in bones and teeth of animals has

Dasarathy

1992-01-01

109

Controlled release of rhodium (II) carboxylates and their association complexes with cyclodextrins from hydroxyapatite matrix  

Microsoft Academic Search

Preparation and characterization of a controlled release system of rhodium (II) citrate, acetate, propionate, butyrate and their inclusion or association compounds with cyclodextrin (CD) are described. The porous hydroxyapatite (HA) was characterized by X-ray powder pattern diffraction, FTIR and solid state 31P NMR. Scanning electron microscopy and gas adsorption analysis (BET) were also performed. Release profiles of rhodium (II) carboxylates

A. E. Burgos; J. C. Belchior; R. D. Sinisterra

2002-01-01

110

Magnesium substituted hydroxyapatite formation on (Ti,Mg)N coatings produced by cathodic arc PVD technique.  

PubMed

In this study, formation of magnesium substituted hydroxyapatite (Ca10-xMgx(PO4)6(OH)2) on (Ti,Mg)N and TiN coating surfaces were investigated. The (Ti1-x,Mgx)N (x=0.064) coatings were deposited on titanium substrates by using cathodic arc physical vapor deposition technique. TiN coated grade 2 titanium substrates were used as reference to understand the role of magnesium on hydroxyapatite (HA) formation. The HA formation experiments was carried out in simulated body fluids (SBF) with three different concentrations (1X SBF, 5X SBF and 5X SBF without magnesium ions) at 37 °C. The coatings and hydroxyapatite films formed were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and FTIR Spectroscopy techniques. The energy dispersive X-ray spectroscopy (EDS) analyses and XRD investigations of the coatings indicated that magnesium was incorporated in the TiN structure rather than forming a separate phase. The comparison between the TiN and (Ti, Mg)N coatings showed that the presence of magnesium in TiN structure facilitated magnesium substituted HA formation on the surface. The (Ti,Mg)N coatings can potentially be used to accelerate the HA formation in vivo conditions without any prior hydroxyapatite coating procedure. PMID:23910351

Onder, Sakip; Kok, Fatma Nese; Kazmanli, Kursat; Urgen, Mustafa

2013-10-01

111

Adhesion between biodegradable polymers and hydroxyapatite: Relevance to synthetic bone-like materials and tissue  

E-print Network

­polymer­HA bonds, scale directly with the results from the wetting experiments. Short-time aging (up to 30 h; Hydroxyapatite; Work of adhesion; Interfacial strength 1. Introduction The search for strong artificial implants importantly, much stiffer [1,2]. This difference in stiffness is the genesis of many failed implants; living

Ritchie, Robert

112

Characterization of the chemically deposited hydroxyapatite coating on a titanium substrate  

Microsoft Academic Search

Bioactive hydroxyapatite (HA) coating on titanium (Ti) implant can be used as a drug delivery device. A controlled release\\u000a of drug around the implant requires the incorporation of drug into the coating material during the coating process. HA coating\\u000a was prepared using a two-step procedure in conditions suitable for simultaneous incorporation of the protein-based drug into\\u000a the coating material. Monetite

Alexander V. Zavgorodniy; Oscar Borrero-López; Mark Hoffman; Racquel Z. LeGeros; Ramin Rohanizadeh

2011-01-01

113

Fabrication of a hydroxyapatite scaffold for bone tissue regeneration using microstereolithography and molding technology  

Microsoft Academic Search

Recently, many groups have researched the reconstruction of bone tissue and the development of bone scaffolds using solid freeform fabrication technology. However, the capacity to produce three-dimensional hydroxyapatite (HA) scaffolds with a very accurate architecture is limited by difficulties in the manufacturing process. In this study, a HA scaffold with an accurate pore size of 300±10?m was fabricated using a

Young-Joon Seol; Jong Young Kim; Eui Kyun Park; Shin-Yoon Kim; Dong-Woo Cho

2009-01-01

114

Synthesis and in vitro evaluation of gelatin\\/hydroxyapatite graft copolymers to form bionanocomposites  

Microsoft Academic Search

The combination of gelatin (Gel) with a bioactive component hydroxyapatite (HA) and cartilage powder (CP) to form biocomposites takes advantage of the osteoconductivity and osteoinductivity properties. The studies on bionanocomposites containing HA, CP fillers and Gel are still being conducted. In this present study, the bioactive fillers were loaded onto poly(hydroxylethylmethacrylate) and poly(hydroxylethylmethacrylate-co-methyl methacrylate) grafted gelatin copolymers to produce novel

Ahmed A. Haroun; V. Migonney

2010-01-01

115

Reconstruction of Extensive Long-Bone Defects in Sheep Using Porous Hydroxyapatite Sponges  

Microsoft Academic Search

.   The capacity of hydroxyapatite (HA) implants to support large defect repair in weight-bearing long bones of large size animals\\u000a was investigated. Diaphyseal resections 3.5 cm of the tibia were performed in five adult sheep. They were substituted with\\u000a HA macroporous ceramic cylinders anatomically shaped, and an external fixator was assembled. The sheep were sacrificed at\\u000a 20, 40, 60, 120,

M. Marcacci; E. Kon; S. Zaffagnini; R. Giardino; M. Rocca; A. Corsi; A. Benvenuti; P. Bianco; R. Quarto; I. Martin; A. Muraglia; R. Cancedda

1999-01-01

116

Adrenomedullin delivery in microsphere-scaffold composite for remodeling of the alveolar bone following tooth extraction: an experimental study in the rat  

PubMed Central

Background Alveolar ridge resorption, as a significant problem in implant and restorative dentistry, has long been considered as an inevitable outcome following tooth extraction. Recently, adrenomedullin (ADM) is reported to be able to stimulate the proliferation and migration of various cells including osteoblasts. The purpose of this study was to investigate the influence of local ADM application in the tooth extraction socket in vivo. Methods Chitosan micropheres were developed by an emulsion-ionic cross-linking method for ADM delivery. Poly (L -lactic-co-glycolic) acid (PLGA) and nano-hydroxyapatite (nHA) were used to prepare scaffolds to contain the micrspheres with ADM. In vivo experiment was evaluated by transplanting the composite into the rat socket right after the incisor extraction. After 4, 8, 12 weeks implantation, radiographic and histological tests were carried out to evaluate the effect of released ADM on the alveolar bone. Results The microspheres had a spherical structure and a relative rough and uniform surface, and the particle size was under a normal distribution, with the average diameter of 38.59 ?m. The scaffolds had open and interconnected pores. In addition, the high porosity of the composite was 88.93%. Radiographic and histological examination revealed that the PLGA/nHA/CMs/ADM composite could accelerate the alveolar bone remodeling and reduce the residual ridge resorption compared with the PLGA/nHA/CMs scaffold. Conclusions The results of this study suggest that local application of ADM has the potential to preserve the residual alveolar ridge and accelerate the alveolar bone remodeling. PMID:24099554

2013-01-01

117

The performance of dental pulp stem cells on nanofibrous PCL\\/gelatin\\/nHA scaffolds  

Microsoft Academic Search

The aim of current study is to investigate the in vitro and in vivo behavior of dental pulp stem cells (DPSCs) seeded on electrospun poly(epsilon-caprolactone) (PCL)\\/gelatin scaffolds with or without the addition of nano-hydroxyapatite (nHA). For the in vitro evaluation, DNA content, alkaline phosphatase (ALP) activity and osteocalcin (OC) measurement showed that the scaffolds supported DPSC adhesion, proliferation, and odontoblastic

X. Yang; F. Yang; X. F. Walboomers; Z. Bian; M. Fan; J. A. Jansen

2010-01-01

118

Single-walled carbon nanotubes/hydroxyapatite coatings on titanium obtained by electrochemical deposition  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes/hydroxyapatite (SWNTs/HA) composite coatings were successfully fabricated by electrochemical deposition technique. Different concentrations of SWNTs were incorporated into the apatite coating by adding functionalized SWNTs into the electrolyte. Homogeneous and crack-free SWNTs/HA composite coatings were achieved and the coatings had higher crystallinity compared to pure HA coating. In addition, the highest bonding strength of the SWNTs/HA coating reached 25.7 MPa, which was nearly 70% higher than that of pure HA coating. The in-vitro cellular biocompatibility tests revealed that SWNTs/HA composite coatings exhibited higher in-vitro bioactivity than that of pure HA coating and pure titanium (Ti). It suggests that SWNTs/HA composite coating may have enormous potential applications in the field of biomaterials, especially for the metal implants.

Pei, Xibo; Zeng, Yongxiang; He, Rui; Li, Zhongjie; Tian, Lingyang; Wang, Jian; Wan, Qianbing; Li, Xiaoyu; Bao, Hong

2014-03-01

119

Immunofluorescence detection methods using microspheres  

NASA Astrophysics Data System (ADS)

Microsphere-based immunoassays were devised for compounds of agricultural and biomedical interest (e.g., digoxin, theophylline, and zearalenone). Commercially available microspheres with surface functional groups for chemical derivatization were used as solid carriers. After immobilizing the target substances, the surface of the haptenized microspheres was blocked by a protein to reduce aspecific binding. Competitive immunoassays were performed using the functionalized microspheres and antibodies labeled with horseradish peroxidase. Immunofluorescence signal amplification was achieved by enzyme-catalyzed reporter deposition (CARD). An epifluorescence microscope, a CCD camera interfaced with a computer, and microscopy image analysis software were employed for quantitative detection of fluorescent light emitted from individual microspheres. Integration of several such immunoassays and application of an optical encoding method enabled multianalyte determination. These immunoassays can also be utilized in an immunosensor array format. This immunoarray format could facilitate miniaturization and automation of multianalyte immunoassays.

Szurdoki, Ferenc; Michael, Karri L.; Agrawal, Divya; Taylor, Laura C.; Schultz, Sandra L.; Walt, David R.

1999-01-01

120

Design of Experiment Analysis of the Sulzer Metco DJ High Velocity Oxy-Fuel Coating of Hydroxyapatite for Orthopedic Applications  

Microsoft Academic Search

High Velocity Oxy-Fuel (HVOF) has the potential to produce hydroxyapatite (HA; Bio-ceramic) coatings based on its experience\\u000a with other sprayed ceramic materials. This technique should offer mechanical and biological results comparable to other thermal\\u000a spraying processes, such as atmospheric plasma thermal spray, currently FDA approved for HA deposition. Deposition of HA via\\u000a HVOF is a new venture especially using the

S. Hasan; J. Stokes

2011-01-01

121

PLGA Microspheres Incorporated Gelatin Scaffold: Microspheres Modulate Scaffold Properties  

PubMed Central

Freeze drying is one of the popular methods of fabrication for poly(lactide-co-glycolide) (PLGA) microspheres incorporated polymer scaffolds. However, the consequence of microspheres incorporation on physical and biological properties of scaffold has not been studied yet. In this study, attempt has been made to characterize the effect of PLGA microsphere incorporation on the physical properties of freeze-dried gelatin scaffold and its influence on cytocompatibility. Scaffolds loaded with varying amount of PLGA microspheres (10%, 1%, 0.1% w/w) were subjected to microarchitecture analysis, swelling, porosity, mechanical properties, biodegradation, cell adhesion, and cell proliferation studies. Results revealed that an increase in percentage loading of microspheres reduced the pore size and uniformity of the pore structure. Moreover, loading of PLGA microspheres up to 1% w/w significantly increased porosity, swelling, and mechanical properties of the scaffold but variations were not proportional for 10% w/w loading. Results also showed that PLGA microspheres have no significant effect on cell adhesion but influenced the growth kinetics. PMID:20126575

Banerjee, Indranil; Mishra, Debasish; Maiti, Tapas K.

2009-01-01

122

Influence of hydroxyapatite crystallization temperature and concentration on stress transfer in wet-spun nanohydroxyapatite-chitosan composite fibres.  

PubMed

Hydroxyapatite possesses appropriate osteoconductivity and biocompatibility for hard-tissue replacement implants but suffers from brittleness. One approach to overcome this problem is to incorporate nanometre hydroxyapatite (nHA) into a polymer matrix, such as chitosan, to yield a hydroxyapatite-chitosan (HC) composite. Here, a novel HC composite was synthesized and its elastic properties were investigated by varying (1) nHA concentration and (2) crystallization temperature (T), where T is a parameter which influences the morphology of the crystals. Crystals of nHA were precipitated at T = 40 degrees C and 100 degrees C, blended in a chitosan matrix, and wet-spun to yield fibres of HC composites at 5, 15, 20 and 40% concentrations (mass fraction of nHA). Scanning electron microscopy and energy-dispersive x-ray spectroscopy revealed a uniform distribution of nanocrystallites within the fibre. Tensile testing revealed that HC fibres, which comprised nHA treated at T = 100 degrees C, possessed low tensile strength, sigma(0), and stiffness, E, at low nHA concentrations but high sigma(0) and E at higher concentrations, i.e. beyond a 15% mass fraction of nHA. However, with nHA treated at T = 40 degrees C, the fibres yielded high sigma(0) and E at low nHA concentrations but low sigma(0) and E at high concentrations. The results strongly implicate the underlying effect of crystallite morphology on stress transfer at different concentrations. PMID:18477816

Xie, J Z; Hein, S; Wang, K; Liao, K; Goh, K L

2008-06-01

123

Synthesis of hydroxyapatite from eggshells  

Microsoft Academic Search

A novel procedure to produce porous hydroxyapatite (HAp) from eggshells is reported. The process is carried out at an elevated temperature. HAp is the only apatite present in the reaction products, apart from minute fractions of certain other calcium compounds. The final product is characterized by X-ray diffraction and scanning electron microscopy (SEM).

Eric M Rivera; Miguel Araiza; Witold Brostow; Victor M Castaño; J. R D??az-Estrada; R Hernández; J. Rogelio Rodr??guez

1999-01-01

124

Synthesis and characterization of TEP-EDTA-regulated bioactive hydroxyapatite  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA), Ca10(PO4)6(OH) 2, the stoichiometric equivalent of the ceramic phase of bone, is the preferred material for hard tissue replacement due to its bioactivity. However, bioinert metals are utilized in load-bearing orthopedic applications due to the poor mechanical properties of HA. Consequently, attention has been given to HA coatings for metallic orthopedic implants to take advantage of the bioactivity of HA and the mechanical properties of metals. Commercially, the plasma spray process (PS-HA) is the method most often used to deposit HA films on metallic implants. Since its introduction in the 1980's, however, concerns have been raised about the consequences of PS-HA's low crystallinity, lack of phase purity, lack of film-substrate chemical adhesion, passivation properties, and difficulty in coating complex geometries. Thus, there is a need to develop inexpensive reproducible next-generation HA film deposition techniques, which deposit high crystallinity, phase pure, adhesive, passivating, conformal HA films on clinical metallic substrates. The aim of this dissertation was to intelligently synthesize and characterize the material and biological properties of HA films on metallic substrates synthesized by hydrothermal crystallization, using thermodynamic phase diagrams as the starting point. In three overlapping interdisciplinary studies the potential of using ethylenediamine-tetraacetic acid/triethyl phosphate (EDTA/TEP) doubly regulated hydrothermal crystallization to deposit HA films, the TEP-regulated, time-and-temperature-dependent process by which films were deposited, and the bioactivity of crystallographically engineered films were investigated. Films were crystallized in a 0.232 molal Ca(NO3)2-0.232 molal EDTA-0.187 molal TEP-1.852 molal KOH-H2O chemical system at 200°C. Thermodynamic phase diagrams demonstrated that the chosen conditions were expected to produce Ca-P phase pure HA, which was experimentally confirmed. EDTA regulation of Ca2+ concentration enabled the HA crystallization process to be growth dominated, producing films composed of high crystallinity, hexagonal grains on multiple metallic substrates. TEP regulation of HA crystallization enabled the deposition of an adhesive CaTiO3 intermediate layer, and then HA in a continuous, phase sequenced process on Ti6Al4V substrates, the first such process reported in the hydrothermal HA literature. The HA film was found to be deposited by a passivating competitive growth mechanism that enabled the [0001] crystallographic orientation of hexagonal single crystals to be engineered with synthesis time. Bioactivity analysis demonstrated that films were bioactive and bone bonding. Together, these results suggest that these HA films are candidates for use on metallic orthopedic implants, namely Ti6Al4V.

Haders, Daniel Joseph, II

125

Ultrasound-assisted fabrication of a biocompatible magnetic hydroxyapatite.  

PubMed

This work describes the fabrication and characterization of a biocompatible magnetic hydroxyapatite (HA) using an ultrasound-assisted co-precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) were used to characterize the structure and chemical composition of the produced samples. The M-H loops of synthesized materials were traced using a vibrating sample magnetometer (VSM) and the biocompatibility was evaluated by cell culture and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Furthermore, in vivo histopathological examinations were used to evaluate the potential toxicological effects of Fe?O?-HA composites on kidney of SD rats injected intraperitoneally with Fe?O?-HA particles. The results showed that magnetic iron oxide particles first replace OH ions of HA, which are parallel to the c axis, and then enter the HA crystal lattice which produces changes in the crystal surface of HA. Chemical bond interaction was observed between PO?³? groups of HA and iron ions of Fe?O?. The saturation magnetization (MS ) of Fe?O?-HA composites was 46.36 emu/g obtained from VSM data. Cell culture and MTT assays indicated that HA could affect the growth and proliferation of HEK-293 cells. This Fe?O?-HA composite produced no negative effects on cell morphology, viability, and proliferation and exhibited remarkable biocompatibility. Moreover, no inflammatory cell infiltration was observed in kidney histopathology slices. Therefore, this study succeeds to develop a Fe?O?-HA composite as a prospective biomagnetic material for future applications. PMID:24339231

Zhou, Gang; Song, Wei; Hou, Yongzhao; Li, Qing; Deng, Xuliang; Fan, Yubo

2014-10-01

126

Hydroxyapatite-nanotube composites and coatings for orthopedic applications  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) has received wide attention in orthopedics, due to its biocompatibility and osseointegration ability. Despite these advantages, the brittle nature and low fracture toughness of HA often results in rapid wear and premature fracture of implant. Hence, there is a need to improve the fracture toughness and wear resistance of HA without compromising its biocompatibility. The aim of the current research is to explore the potential of nanotubes as reinforcement to HA for orthopedic implants. HA- 4 wt.% carbon nanotube (CNT) composites and coatings are synthesized by spark plasma sintering and plasma spraying respectively, and investigated for their mechanical, tribological and biological behavior. CNT reinforcement improves the fracture toughness (>90%) and wear resistance (>66%) of HA for coating and free standing composites. CNTs have demonstrated a positive influence on the proliferation, differentiation and matrix mineralization activities of osteoblasts, during in-vitro biocompatibility studies. In-vivo exposure of HA-CNT coated titanium implant in animal model (rat) shows excellent histocompatibility and neobone integration on the implant surface. The improved osseointegration due to presence of CNTs in HA is quantified by the adhesion strength measurement of single osteoblast using nano-scratch technique. Considering the ongoing debate about cytotoxicity of CNTs in the literature, the present study also suggests boron nitride nanotube (BNNT) as an alternative reinforcement. BNNT with the similar elastic modulus and strength as CNT, were added to HA. The resulting composite having 4 wt.% BNNTs improved the fracture toughness (˜85%) and wear resistance (˜75%) of HA in the similar range as HA-CNT composites. BNNTs were found to be non-cytotoxic for osteoblasts and macrophages. In-vitro evaluation shows positive role of BNNT in osteoblast proliferation and viability. Apatite formability of BNNT surface in ˜4 days establishes its osseointegration ability.

Lahiri, Debrupa

127

Increased osteoblast adhesion on nanoparticulate crystalline hydroxyapatite functionalized with KRSR  

PubMed Central

The present in vitro study created nanometer crystalline hydroxyapatite (HA) and amorphous calcium phosphate for novel orthopedic applications. Specifically, nano-crystalline HA and amorphous calcium phosphate nanoparticles were synthesized by a wet chemical process followed by hydrothermal treatment for 2 hours at 200°C and 70°C, respectively. Resulting particles were then pressed into compacts. For the preparation of control conventional HA particles (or those currently used in orthopedics with micron diameters), the aforementioned calcium phosphate particles were pressed into compacts and sintered at 1100°C for 2 hours. All calcium phosphate-based particles were fully characterized. Results showed that although there was an initial weight gain for all the compacts studied in this experiment, higher eventual degradation rates up to 3 weeks were observed for nano-amorphous calcium phosphate compared with nano-crystalline HA which was higher than conventional HA. Peptide functionalization (with the cell adhesive peptide lysine-arginine-serine-arginine [KRSR] and the non-cell-adhesive peptide lysine-serine-arginine-arginine [KSRR]) was accomplished by means of a three-step reaction procedure: silanization with 3-aminopropyltriethoxysilane (APTES), cross-linking with N-succinimidyl-3-maleimido propionate (SMP), and finally peptide immobilization. The peptide functionalization was fully characterized. Results demonstrated increased osteoblast (bone-forming cell) adhesion on non-functionalized and functionalized nano-crystalline HA compacts compared with nano amorphous calcium phosphate compacts; both increased osteoblast adhesion compared with conventional HA. To further exemplify the novel properties of nano crystalline HA, results also showed similar osteoblast adhesion between non-functionalized nano crystalline HA and KRSR functionalized conventional HA. Thus, results provided evidence that nanocrystalline HA should be further studied for orthopedic applications. PMID:17717974

Nelson, Michael; Balasundaram, Ganesan; Webster, Thomas J

2006-01-01

128

Calcium Deficient Hydroxyapatite for Medical Application Prepared by Hydrothermal Method  

NASA Astrophysics Data System (ADS)

Hydrothermal processing plays a key role in the synthesis of biomaterials with excellent biocompatibility in the physiological environment. Especially, calcium phosphates are paid to much attention for the regenerative medicine. Two kinds of porous materials of hydroxyapatite with 70% porosity were prepared. One of them is a newly developed calcium-deficient hydroxyapatite composed of rod-shaped particles of about 20 ?m in length synthesized hydrothermally (HHA) and the other one is the stoichiometric hydroxyapatite (SHA) prepared by the conventional sintering method. These materials were used for animal implantation tests to compare these biological responses. In the rabbit femur, implanted HHA was slowly resorbed and then most of the implanted HHA was resorbed after 72 weeks. The implanted SHA was unresorbed throughout the experimental period. The volume of newly formed bone and the number of osteoclasts in the implanted region were significantly larger in HHA than in SHA after 24 weeks. Results in the present research suggested that the activity of osteoclasts correlated to the bone forming activity of osteoblasts. The method to synthesize biodegradable pure calcium-deficient HA is expected to provide adequate biodegradability and bone replaceability.

Ioku, Koji; Kamitakahara, Masanobu; Ikeda, Tohru

2010-11-01

129

Gelatine-Hydroxyapatite Nano-composites for Orthopaedic Applications  

NASA Astrophysics Data System (ADS)

This study focuses on the preparation and testing of hydroxyapatite-gelatine nano-composite gels via a sol-gel route and in situ formation of hydroxyapatite (HA) type salts. Four types of gels and foams were prepared with Ca/P molar ratio of 0.43 and 0.86 and hydroxyapatite/gelatine weight ratio of 0.50 and 0.70. Cross-linking of gelatine chains was carried out in 1% glutaraldehyde and dynamic mechanical torsion tests were used to measure the viscoelastic properties of the gels and foams, optimize the cross-linking time and assess their mechanical performance. Optical and atomic force microscopy were used to investigate the micro- and nano-structure of the produced composites: in these studies, it was confirmed that the gels were nano-composites with a nano-structure very similar to that of bone and several similarities in the microstructural features. The best foams incorporated dual pore size distribution.

Vidyarthi, U.; Zhdan, P.; Gravanis, C.; Lekakou, C.

2008-09-01

130

Na-doped hydroxyapatite coating on carbon/carbon composites: Preparation, in vitro bioactivity and biocompatibility  

NASA Astrophysics Data System (ADS)

Na-doped hydroxyapatite (Na-HA) coating was directly prepared onto carbon/carbon (C/C) composites using electrochemical deposition (ECD) and the mean thickness of the coating is approximately 10 ± 2 ?m. The formed Na-HA crystals which are Ca-deficient, are rod-like with a hexagonal cross section. The Na/P molar ratios of the coating formed on C/C substrate is 0.097. During the deposition, the Na-HA crystals grow in both radial and longitudinal directions, and faster along the longitudinal direction. The pattern formation of crystal growth leads to dense coating which would help to increase the bonding strength of the coating. The average shear bonding strength of Na-HA coating on C/C is 5.55 ± 0.77 MPa. The in vitro bioactivity of the Na-HA coated C/C composites were investigated by soaking the samples in a simulated body fluid (SBF) for 14 days. The results indicate that the Na-HA coated C/C composites can rapidly induce bone-like apatite nucleation and growth on its surface in SBF. The in vitro cellular biocompatibility tests reveal that the Na-HA coating was better to improve the in vitro biocompatibility of C/C composites compared with hydroxyapatite (HA) coating. It was suggested that the Na-HA coating might be an effective method to improve the surface bioactivity and biocompatibility of C/C composites.

Li, Hejun; Zhao, Xueni; Cao, Sheng; Li, Kezhi; Chen, Mengdi; Xu, Zhanwei; Lu, Jinhua; Zhang, Leilei

2012-12-01

131

Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: dissolution behaviour and biological properties after crystallisation.  

PubMed

Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) were synthesised by the sol-gel method as possible implant coating or bone-grafting materials. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride were incorporated for the preparation of the FHA and FA sol-gels. After heating and powdering the sol-gels, dissolution behaviour was assessed using ion chromatography to measure Ca(2+) and PO4 (3-) ion release. Biological behaviour was assessed using cellular proliferation with human osteosarcoma cells and alamarBlue™ assay. Statistical analysis was performed with a two way analysis of variance and post hoc testing with a Bonferroni correction. Increasing fluoride substitution into an apatite structure decreased the dissolution rate. Increasing the firing temperature of the HA, FHA and FA sol-gels up to 1,000 °C decreased the dissolution rate. There was significantly higher cellular proliferation on highly substituted FHA and FA than on HA or Titanium. The properties of an implant coating or bone grafting material can be tailored to meet specific requirements by altering the amount of fluoride that is incorporated into the original apatite structure. The dissolution behaviour can further be altered by the temperature at which the sol-gel is fired. PMID:24052344

Tredwin, Christopher J; Young, Anne M; Abou Neel, Ensanya A; Georgiou, George; Knowles, Jonathan C

2014-01-01

132

Hydroxyapatite thin films synthesized by Pulsed Laser Deposition onto titanium mesh implants for cranioplasty applications  

NASA Astrophysics Data System (ADS)

We report on the synthesis of advanced nanostructured hydroxyapatite thin films onto 3D titanium (Ti) mesh substrates by Pulsed Laser Deposition method. Morphological and structural investigations as well as pull-out tests proved the stoichiometric transfer of crystalline hydroxyapatite (HA) films along with their good adherence. In vivo tests were performed on 12 patients (six with simple Ti mesh, six with Ti mesh biofunctionalized with HA). The tomodensitometry analysis of the cranial control scans evidenced the process of osseogenesis. For four patients with implanted HA/Ti mesh structures, the modification of the value obtained on Hounsfield scale was observed at the level of implant, proving the progress of osseointegration. We conclude that the structures exhibit excellent bonding strength and functionality, and are suitable for neurosurgical applications.

Duta, L.; Stan, G. E.; Popescu, A. C.; Socol, G.; Miroiu, F. M.; Mihailescu, I. N.; Ianculescu, A.; Poeata, I.; Chiriac, A.

2013-06-01

133

Micro- and nanostructured hydroxyapatite-collagen microcarriers for bone tissue-engineering applications.  

PubMed

Novel hydroxyapatite (HA)-collagen microcarriers (MCs) with different micro/nanostructures were developed for bone tissue-engineering applications. The MCs were fabricated via calcium phosphate cement (CPC) emulsion in oil. Collagen incorporation in the liquid phase of the CPC resulted in higher MC sphericity. The MCs consisted of a porous network of entangled hydroxyapatite crystals, formed as a result of the CPC setting reaction. The addition of collagen to the MCs, even in an amount as small as 0.8?wt%, resulted in an improved interaction with osteoblast-like Saos-2 cells. The micro/nanostructure and the surface texture of the MCs were further tailored by modifying the initial particle size of the CPC. A synergistic effect between the presence of collagen and the nanosized HA crystals was found, resulting in significantly enhanced alkaline phosphatase activity on the collagen-containing nanosized HA MCs. PMID:22328196

Perez, R A; Altankov, G; Jorge-Herrero, E; Ginebra, M P

2013-05-01

134

Hydroxyapatite-magnetite-MWCNT nanocomposite as a biocompatible multifunctional drug delivery system for bone tissue engineering.  

PubMed

New magnetic hydroxyapatite-based nanomaterials as bone-specific systems for controlled drug delivery have been synthesized. The synthesized hydroxyapatite, HA, decorated with magnetite nanoparticles by a deposition method (HA/Fe3O4) and the nanocomposite system obtained using magnetic multi-walled carbon nanotubes (HA/MWCNT/Fe3O4) as a filler for HA have been characterized by chemical and morphological analyses, and their biological behavior was investigated. The systems have also been doped with clodronate in order to combine the effect of bone biomineralization induced by hydroxyapatite-based composites with the decrease of osteoclast formation induced by the drug. An analysis of the preosteoclastic RAW264.7 cell proliferation by MTT assay confirmed the high biocompatibility of the three systems. TRAP staining of RAW 264.7 conditioned with sRAKL to induce osteoclastogenesis, cultured in the presence of the systems doped and undoped with clodronate, showed the inhibitory effect of clodronate after we counted the MNC TRAP(+)cells but only in the osteoclast formation; in particular, the system HA/Fe3O4-Clo exerted a high inhibitory effect compared to the drug alone. These results demonstrate that the synthesized nanocomposites are a biocompatible magnetic drug delivery system and can represent a useful multimodal platform for applications in bone tissue engineering. PMID:25265364

Pistone, Alessandro; Iannazzo, Daniela; Panseri, Silvia; Montesi, Monica; Tampieri, Anna; Galvagno, Signorino

2014-10-24

135

Hydroxyapatite-magnetite-MWCNT nanocomposite as a biocompatible multifunctional drug delivery system for bone tissue engineering  

NASA Astrophysics Data System (ADS)

New magnetic hydroxyapatite-based nanomaterials as bone-specific systems for controlled drug delivery have been synthesized. The synthesized hydroxyapatite, HA, decorated with magnetite nanoparticles by a deposition method (HA/Fe3O4) and the nanocomposite system obtained using magnetic multi-walled carbon nanotubes (HA/MWCNT/Fe3O4) as a filler for HA have been characterized by chemical and morphological analyses, and their biological behavior was investigated. The systems have also been doped with clodronate in order to combine the effect of bone biomineralization induced by hydroxyapatite-based composites with the decrease of osteoclast formation induced by the drug. An analysis of the preosteoclastic RAW264.7 cell proliferation by MTT assay confirmed the high biocompatibility of the three systems. TRAP staining of RAW 264.7 conditioned with sRAKL to induce osteoclastogenesis, cultured in the presence of the systems doped and undoped with clodronate, showed the inhibitory effect of clodronate after we counted the MNC TRAP+cells but only in the osteoclast formation; in particular, the system HA/Fe3O4-Clo exerted a high inhibitory effect compared to the drug alone. These results demonstrate that the synthesized nanocomposites are a biocompatible magnetic drug delivery system and can represent a useful multimodal platform for applications in bone tissue engineering.

Pistone, Alessandro; Iannazzo, Daniela; Panseri, Silvia; Montesi, Monica; Tampieri, Anna; Galvagno, Signorino

2014-10-01

136

An investigation of the effects of hydroxyapatite coatings on the fixation strength of cortical screws.  

PubMed

Hydroxyapatite (HA) are commonly applied to orthopaedic implants for acceleration of osteointegration and so overcoming the loosening problems such as in cortical screws. Electrophoretic deposition (EPD) of hydroxyapatite was applied for coating of cortical screws in this work. The effects of hydroxyapatite-coated and uncoated cortical screws on insertion and extraction torque were investigated through in vivo experiments. Three groups of screws were undertaken: first group with no coating, second group coated with HA and the third group coated with HA+interlayer, a synthetic calcium silicate compound. Five sheep were operated, and 60 cortical (20 x 3) screws from those of groups were implanted in cortical femurs to observe the effect of HA and interlayer on screws. Results show that as an alternative to plasma spray coating method, the EPD process enables to produce a quick, easy, cheap and uniform adjustable coating layer. Also from biomechanical and SEM examinations, HA coating by EPD method of cortical screws resulted in extremely improved fixation with reduced risk of loosening problem. PMID:15694605

Yildirim, O S; Aksakal, B; Celik, H; Vangolu, Y; Okur, A

2005-04-01

137

Effect of different sintering methods on bioactivity and release of proteins from PLGA microspheres.  

PubMed

Macromolecule release from poly(d,l-lactide-co-glycolide) (PLGA) microspheres has been well-characterized, and is a popular approach for delivering bioactive signals from tissue-engineered scaffolds. However, the effect of some processing solvents, sterilization, and mineral incorporation (when used in concert) on long-term release and bioactivity has seldom been addressed. Understanding these effects is of significant importance for microsphere-based scaffolds, given that these scaffolds are becoming increasingly more popular, yet growth factor activity following sintering and/or sterilization is heretofore unknown. The current study evaluated the 6-week release of transforming growth factor (TGF)-?3 and bone morphogenetic protein (BMP)-2 from PLGA and PLGA/hydroxyapatite (HAp) microspheres following exposure to ethanol (EtOH), dense phase carbon dioxide (CO2), or ethylene oxide (EtO). EtO was chosen based on its common use in scaffold sterilization, whereas EtOH and CO2 were chosen given their importance in sintering microspheres together to create scaffolds. Release supernatants were then used in an accelerated cell stimulation study with human bone marrow stromal cells (hBMSCs) with monitoring of gene expression for major chondrogenic and osteogenic markers. Results indicated that in microspheres without HAp, EtOH exposure led to the greatest amount of delivery, while those treated with CO2 delivered the least growth factor. In contrast, formulations with HAp released almost half as much protein, regardless of EtOH or CO2 exposure. Notably, EtO exposure was not found to significantly affect the amount of protein released. Cell stimulation studies demonstrated that eluted protein samples performed similarly to positive controls in PLGA-only formulations, and ambiguously in PLGA/HAp composites. In conclusion, the use of EtOH, subcritical CO2, and EtO in microsphere-based scaffolds may have only slight adverse effects, and possibly even desirable effects in some cases, on protein availability and bioactivity. PMID:23910352

Dormer, Nathan H; Gupta, Vineet; Scurto, Aaron M; Berkland, Cory J; Detamore, Michael S

2013-10-01

138

Effect of different sintering methods on bioactivity and release of proteins from PLGA microspheres  

PubMed Central

Macromolecule release from poly(d,l-lactide-co-glycolide) (PLGA) microspheres has been well-characterized, and is a popular approach for delivering bioactive signals from tissue-engineered scaffolds. However, the effect of some processing solvents, sterilization, and mineral incorporation (when used in concert) on long-term release and bioactivity has seldom been addressed. Understanding these effects is of significant importance for microsphere-based scaffolds, given that these scaffolds are becoming increasingly more popular, yet growth factor activity following sintering and/or sterilization is heretofore unknown. The current study evaluated the 6-week release of transforming growth factor (TGF)-?3 and bone morphogenetic protein (BMP)-2 from PLGA and PLGA/hydroxyapatite (HAp) microspheres following exposure to ethanol (EtOH), dense phase carbon dioxide (CO2), or ethylene oxide (EtO). EtO was chosen based on its common use in scaffold sterilization, whereas EtOH and CO2 were chosen given their importance in sintering microspheres together to create scaffolds. Release supernatants were then used in an accelerated cell stimulation study with human bone marrow stromal cells (hBMSCs) with monitoring of gene expression for major chondrogenic and osteogenic markers. Results indicated that in microspheres without HAp, EtOH exposure led to the greatest amount of delivery, whilst those treated with CO2 delivered the least growth factor. In contrast, formulations with HAp released almost half as much protein, regardless of EtOH or CO2 exposure. Notably, EtO exposure was not found to significantly affect the amount of protein released. Cell stimulation studies demonstrated that eluted protein samples performed similarly to positive controls in PLGA-only formulations, and ambiguously in PLGA/HAp composites. In conclusion, the use of EtOH, subcritical CO2, and EtO in microsphere-based scaffolds may have only slight adverse effects, and possibly even desirable effects in some cases, on protein availability and bioactivity. PMID:23910352

Dormer, Nathan H.; Gupta, Vineet; Scurto, Aaron M.; Berkland, Cory J.; Detamore, Michael S.

2013-01-01

139

Towards Monodispersed Polymer Microspheres  

NASA Astrophysics Data System (ADS)

Uniform polymer microspheres prepared by Spinning Disk Atomization Our spinning disk atomization (SDA) can, relative to other existing techniques, produce micron-sized particles of very narrow size distribution. Around the edge of the disk, small teeth channel the flow into identical droplets that are flung off over the disk rim. These solidify during flight to form spherical particles. Applications for spheres produced by SDA can be found in areas such as adhesives, powder coatings, food, biomedical use, drug delivery systems, etc. We have atomized polyethyleneglycol into very narrowly dispersed microspheres ranging from 50 to 500 =B5m. The aim of this work is to model the droplet formation occurring at the rim of the spinning disk in order to better understand the experimental results. The viscosity contribution in the fluid breakup is qualitatively analyzed and is adapted to the theoretical model to show how it affects the droplet size. We have used the pendant drop model (Ramesh Babu, S. Journal of Colloid and Interface Science 116, 350-372 (1987).) for spinning disk atomization to describe the drop-shape evolution during growth.

Senuma, Yoshinori; Hilborn, Jons

1998-03-01

140

Surface modification of hydroxyapatite nanoparticles by poly( L-phenylalanine) via ROP of L-phenylalanine N-carboxyanhydride (Pha-NCA)  

NASA Astrophysics Data System (ADS)

The surface of hydroxyapatite nanoparticles was modified by poly( L-phenylalanine) via the ring opening polymerization (ROP) of L-phenylalanine N-carboxyanhydride. The preparation procedure was monitored by Fourier transform infrared spectroscopy (FTIR), and the modified hydroxyapatite was characterized by thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). The results showed that the surface grafting amounts of poly( L-phenylalanine) on HA ranging from 20.26% to 38.92% can be achieved by tuning the reaction condition. The XRD patterns demonstrated that the crystalline structure of the modified hydroxyapatite was nearly the same with that of HA, implying that the ROP was an efficient surface modification method. The MTT assay proved that the biocompatibility of modified HA was very good, which showed the potential application of modified HA in bone tissue engineering.

Dai, Yanfeng; Xu, Min; Wei, Junchao; Zhang, Haobin; Chen, Yiwang

2012-01-01

141

Addressing processing problems associated with plasma spraying of hydroxyapatite coatings.  

PubMed

Biomedical coatings generally have to satisfy specific requirements such as a high degree of crystallinity (for positive biological responses), good coating adhesion and optimal porosity. These are necessary to enhance biocompatibility, accelerate post-operative healing and improved fixation. Thermal spray processes have been frequently used to deposit functionally active biomedical coatings, such as hydroxyapatite (HA), onto prosthetic implants. The benefits of HA materials in coated implants have been widely acknowledged, but the occurrence of several poor performances has generated concerns over the consistency and reliability of thermally sprayed HA coatings. Recent investigations using HA coatings have shown that process related variability has significant influence on coating characteristics such as phase composition, structure and chemical composition and performance such as bioresorption, degradation and bone apposition. Variation in process parameters such as powder morphology can induce microstructural and mechanical inconsistencies that have an effect on the service performance of the coating. In order to reach some acceptable level of reliability, it may be necessary to control existing variability in commercially available HA feedstock. In addition, certain opposing factors severely constrain the means to achieve the necessary coating conditions via thermal spraying alone; therefore, creating the need to introduce other innovative or secondary treatment stages to attain the desired results. This paper highlights some of the problems associated with plasma spray coating of HA and suggests that tailoring the powder feedstock morphology and properties through suitable conditioning processes can aid the deposition efficiency and produce an acceptable coating structure. PMID:8991486

Cheang, P; Khor, K A

1996-03-01

142

Role of osteopontin in modulation of hydroxyapatite formation.  

PubMed

The presence of osteopontin (OPN) at high levels in both mineralized tissues such as bone and ectopic calcifications such as atherosclerotic plaque presents a conundrum: is OPN a promoter or inhibitor of hydroxyapatite (HA) formation? In vitro studies show that OPN adsorbs tightly to HA and is a potent inhibitor of crystal growth. Although the mechanism of the OPN-HA interaction is not fully understood, it is probably electrostatic in nature. Phosphorylation enhances OPN's ability to adsorb to and inhibit the growth of HA crystals, although other anionic groups also contribute to these properties. Recent findings suggest that OPN is an intrinsically unordered protein and that its lack of folded structure facilitates the protein's adsorption by allowing multiple binding geometries and the sequential formation of ionic bonds with Ca(2+) ions of the crystal surface. By analogy with other biominerals, it is likely that adsorption of OPN to HA results in "pinning" of growth steps. The abundance of OPN at sites of ectopic calcification reflects upregulation of the protein in response to crystal formation or even in response to elevated phosphate levels. Therefore, it appears that OPN is one of a group of proteins that function to prevent crystal formation in soft tissues. The role of OPN in bone mineralization, if any, is less clear. However, it is possible that it modulates HA formation, either by preventing crystal growth in "inappropriate" areas such as the osteoid seam or by regulating crystal growth habit (size and shape). PMID:23334303

Hunter, Graeme K

2013-10-01

143

Osteoconductive hydroxyapatite coated PEEK for spinal fusion surgery  

NASA Astrophysics Data System (ADS)

Polyetheretherketone (PEEK) has attracted much interest as biomaterial for interbody fusion cages due to its similar stiffness to bone and good radio-transparency for post-op visualization. Hydroxyapatite (HA) coating stimulates bone growth to the medical implant. The objective of this work is to make an implant consisting of biocompatible PEEK with an osteoconductive HA surface for spinal or orthopedic applications. Highly dense and well-adhered HA coating was developed on medical-grade PEEK using aerosol deposition (AD) without thermal degradation of the PEEK. The HA coating had a dense microstructure with no cracks or pores, and showed good adhesion to PEEK at adhesion strengths above 14.3 MPa. The crystallinity of the HA coating was remarkably enhanced by hydrothermal annealing as post-deposition heat-treatment. In addition, in vitro and in vivo biocompatibility of PEEK, in terms of cell adhesion morphology, cell proliferation, differentiation, and bone-to-implant contact ratio, were remarkably enhanced by the HA coating through AD.

Hahn, Byung-Dong; Park, Dong-Soo; Choi, Jong-Jin; Ryu, Jungho; Yoon, Woon-Ha; Choi, Joon-Hwan; Kim, Jong-Woo; Ahn, Cheol-Woo; Kim, Hyoun-Ee; Yoon, Byung-Ho; Jung, In-Kwon

2013-10-01

144

Effects of the reinforcement morphology on the fatigue properties of hydroxyapatite reinforced polymers.  

PubMed

The objective of this study was to examine the effects of the hydroxyapatite (HA) reinforcement morphology and content on the fatigue behavior of HA reinforced high density polyethylene (HDPE). To this end, HDPE was reinforced with 20 and 40 vol% of either HA whiskers or an equiaxed HA powder, and tested in four-point bending fatigue under simulated physiological conditions. The fatigue life, mechanical property degradation and failure surfaces were compared between experimental groups. HDPE reinforced with HA whiskers exhibited a four- to five-fold increase (p < 0.001, T-test) in fatigue life compared to an equiaxed powder for either the 20 and 40 vol% reinforcement level. Composites containing 40 vol% HA exhibited decreased fatigue life compared to those with 20 vol% HA for either reinforcement morphology (p < 0.0001, ANOVA). HA whisker reinforced HDPE exhibited less stiffness loss, permanent deformation (creep) and energy dissipation at a given number of cycles compared to HA powder. Thus, HA whisker reinforced HDPE was more tolerant of fatigue damage due to either microcracking or polymer plasticity. Scanning electron microscopy of failure surfaces and surface microcracks showed evidence of toughening by uncracked ligaments, crack tip plasticity, polymer fibril bridging and HA whisker pullout. The results of this study suggest that the use of HA whiskers, in place of HA powder, is a straightforward means to improve the fatigue life and damage tolerance of HA reinforced polymers for synthetic bone substitutes. PMID:19578474

Kane, Robert J; Converse, Gabriel L; Roeder, Ryan K

2008-07-01

145

Effects of the Reinforcement Morphology on the Fatigue Properties of Hydroxyapatite Reinforced Polymers  

PubMed Central

The objective of this study was to examine the effects of the hydroxyapatite (HA) reinforcement morphology and content on the fatigue behavior of HA reinforced high density polyethylene (HDPE). To this end, HDPE was reinforced with 20 and 40 vol% of either HA whiskers or an equiaxed HA powder, and tested in four-point bending fatigue under simulated physiological conditions. The fatigue life, mechanical property degradation and failure surfaces were compared between experimental groups. HDPE reinforced with HA whiskers exhibited a four- to five-fold increase (p < 0.001, T-test) in fatigue life compared to an equiaxed powder for either the 20 and 40 vol% reinforcement level. Composites containing 40 vol% HA exhibited decreased fatigue life compared to those with 20 vol% HA for either reinforcement morphology (p < 0.0001, ANOVA). HA whisker reinforced HDPE exhibited less stiffness loss, permanent deformation (creep) and energy dissipation at a given number of cycles compared to HA powder. Thus, HA whisker reinforced HDPE was more tolerant of fatigue damage due to either microcracking or polymer plasticity. Scanning electron microscopy of failure surfaces and surface microcracks showed evidence of toughening by uncracked ligaments, crack tip plasticity, polymer fibril bridging and HA whisker pullout. The results of this study suggest that the use of HA whiskers, in place of HA powder, is a straightforward means to improve the fatigue life and damage tolerance of HA reinforced polymers for synthetic bone substitutes. PMID:19578474

Kane, Robert J.; Converse, Gabriel L.; Roeder, Ryan K.

2008-01-01

146

Microsphere contrast agents for OCT  

E-print Network

,17 , absorbing dyes18,19 , plasmon-resonant nanoparticles20,21 and magnetomotive nanoparticles22 . This chapter describes the fabrication, characterization and application of a new class of engineered protein microsphere

Suslick, Kenneth S.

147

Characterization of Hydroxyapatite-Glass Composites Using Terahertz Time-Domain Spectroscopy  

NASA Astrophysics Data System (ADS)

Terahertz time-domain spectroscopy (THz-TDS) is presented as a tool for characterization of the hydroxyapatite (HA)-glass composites. The materials under investigation are composites of HA and a calcium zinc silicate glass. Our results show that the refractive index and dielectric constant in THz frequencies provide a reliable determination of glass content of these composites. In addition, the THz-TDS is used to morphological changes in HA during simulated body fluid (SBF) incubation. Our results demonstrate that the THz-TDS can be a promising non-destructive tool.

Yatongchai, C.; Wren, A. W.; Sundaram, S. K.

2014-08-01

148

Glass microsphere lubrication  

NASA Technical Reports Server (NTRS)

The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the manufacturing of the microspheres, while sorting entails deciphering the good microspheres from the bad ones. Each process is discussed in detail.

Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

1991-01-01

149

Support for the initial attachment, growth and differentiation of MG-63 cells: a comparison between nano-size hydroxyapatite and micro-size hydroxyapatite in composites.  

PubMed

Hydroxyapatite (HA) is considered to be a bioactive material that favorably influences the adhesion, growth, and osteogenic differentiation of osteoblasts. To optimize the cell response on the hydroxyapatite composite, it is desirable to assess the optimum concentration and also the optimum particle size. The aim of our study was to prepare composite materials made of polydimethylsiloxane, polyamide, and nano-sized (N) or micro-sized (M) HA, with an HA content of 0%, 2%, 5%, 10%, 15%, 20%, 25% (v/v) (referred to as N0-N25 or M0-M25), and to evaluate them in vitro in cultures with human osteoblast-like MG-63 cells. For clinical applications, fast osseointegration of the implant into the bone is essential. We observed the greatest initial cell adhesion on composites M10 and N5. Nano-sized HA supported cell growth, especially during the first 3 days of culture. On composites with micro-size HA (2%-15%), MG-63 cells reached the highest densities on day 7. Samples M20 and M25, however, were toxic for MG-63 cells, although these composites supported the production of osteocalcin in these cells. On N2, a higher concentration of osteopontin was found in MG-63 cells. For biomedical applications, the concentration range of 5%-15% (v/v) nano-size or micro-size HA seems to be optimum. PMID:25125978

Filová, Elena; Suchý, Tomáš; Sucharda, Zbyn?k; Supová, Monika; Zaloudková, Margit; Balík, Karel; Lisá, V?ra; Slouf, Miroslav; Ba?áková, Lucie

2014-01-01

150

Materials processing and in-vivo animal studies of nitrided hydroxyapatite bioceramics  

NASA Astrophysics Data System (ADS)

Calcium phosphate bioceramics are currently being used in medicine and dentistry, for reconstruction or repair of diseased or injured bone, but with limited success. Incorporating nitrogen into phosphate glasses has resulted in improved properties, and it is proposed that similar benefits may be gained from nitriding calcium phosphate bioceramics for bone implants as well. This work focuses on processing of hydroxyapatite and tricalcium phosphate bioceramics nitrided by using solid, liquid, gas and ion sources. These materials were characterized by chemical, structural, mechanical, and biological methods to determine both the material structure and their suitability as implant materials. Calcium nitride and NaPON glass were unsatisfactory sources of nitrogen for hydroxyapatite (HA) and/or tricalcium phosphate (TCP) ceramics. Calcium nitride, Ca3N2, is reacts with water vapor in the air, releasing ammonia, and leaving behind crystals of calcium oxide, CaO. The calcium oxide byproduct decreases the chemical stability of hydroxyapatite and HA/TCP composites in simulated body fluid. Sodium phosphorus oxynitride (NaPON) glass, in the form of a liquid sintering aid for HA, produces an inhomogeneous, composite as well. Hydroxyapatite heated at 800C in an ammonia atmosphere produces a homogeneous material with up to 2 wt% N. Infrared spectroscopy indicates cyanamide ions, CN22-, are formed by the incorporated nitrogen and impurity carbon. The use of 15N-doped ammonia results in an 15N NMR peak at 83.2 ppm, indicating P--N bonding. Raman spectroscopy may also indicate P--N bonding, but it is inconclusive. In a limited study, nitrogen may decrease the hardness and fracture toughness of the phosphate ceramic, hydroxyapatite, contrary to results expected for nitrogen in phosphate glasses. Nitrogen ions are incorporated in hydroxyapatite by ion implantation, with lower energies producing higher nitrogen contents. The highest concentration achieved was 3.55 wt% N, as determined by electron microprobe analysis. Both ammonia-nitrided samples and ion-implanted samples were used as substrates for bone morphogenetic proteins (BMPs) in biological studies. Nitrided hydroxyapatite samples with BMPs showed an increase in bone formation when surgically implanted in rats. Furthermore, the bone formation increased with increasing nitrogen. On the other hand, bone formation decreased with increasing nitrogen for nitrided HA samples without BMPs.

Rashid, Nancy Elizabeth

2000-10-01

151

pH-sensitive fluorescent hepatocyte-targeting multilayer polyelectrolyte hollow microspheres as a smart drug delivery system.  

PubMed

Novel multilayer polyelectrolyte hollow microspheres with pH-sensitive fluorescence and hepatocyte-targeting functions were successfully fabricated via a layer-by-layer (LbL) assembly of fluorescein isothiocyanate (FITC)-modified chitosan (CSFITC) and sodium hyaluronate (HA) (as the polycation and polyanion, respectively) on polystyrene sulfonate (PSS) templates with galactosylated chitosan (GC) as the outermost layer; after etching the templates by dialysis, the aim was to use the microspheres to target hepatocytes specifically. TEM analysis revealed that they have a hollow structure with a particle size of about 260 nm, and DLS analysis demonstrated that they have pH and ionic strength dual-responsive characteristics. The hollow microspheres showed pH-sensitive fluorescence at a very low concentration by fluorescent emission spectra. MTT assays revealed that doxorubicin (a water-insoluble anticancer drug)-loaded (CSFITC/HA)4/GC hollow microspheres can specifically target hepatocytes and exhibit favorable cytocompatibility. Three typical model drugs were loaded into the (CSFITC/HA)4/GC hollow microspheres, and their drug-release kinetics in simulated body fluid (SBF) were estimated with different mathematical models. The results demonstrated that the drug-loading mechanism is chemosorption and the primary governing force for drug release is diffusion. Thus, the designed hollow microspheres are expected to be used for the diagnosis and therapy of hepatic cancer. PMID:24665978

Zhao, Xubo; Liu, Peng

2014-05-01

152

Hydroxyapatite interactions with copper complexes  

Microsoft Academic Search

Hydroxyapatite was used to remove dilute copper(II) from aqueous solutions containing organic ligands. Both synthetic apatite and natural apatite originating from animal bones retained copper(II) in a flow-through column experiment but lost much of this ability when glycine, ethylenediamine or ethylenediaminetetraacetic acid (EDTA) was present in the solution. The amounts of copper(II) withheld by apatite was compared to the concentrations

F. Fernane; M. O. Mecherri; P. Sharrock; M. Fiallo; R. Sipos

2010-01-01

153

Sulfobetaine as a zwitterionic mediator for 3D hydroxyapatite mineralization  

PubMed Central

Both positively and negatively charged residues play pivotal roles in recruiting precursor ions or ion clusters, and lowering interfacial energy in natural biomineralization process. Synergistic utilization of opposite charges, however, has rarely been implemented in the design of cytocompatible synthetic scaffolds promoting hydroxyapatite (HA)-mineralization and osteointegration. We report the use of cytocompatible zwitterionic sulfobetaine ligands to enable 3-dimensional in vitro mineralization of HA across covalently crosslinked hydrogels. The overall charge-neutral zwitterionic hydrogel effectively recruited oppositely charged precursor ions while overcame excessive swelling exhibited by anionic and cationic hydrogels under physiological conditions, resulting in denser and structurally well-integrated mineralized composites. Further controls over the size, content, and spatial distribution of the mineral domains within the zwitterionic hydrogel are accomplished by facile adjustments of hydrogel crosslinking densities and the supersaturation rate governing heterogeneous mineral nucleation and growth. These findings should inspire many creative uses of zwitterionic polymers and polymer coatings for skeletal tissue repair and regeneration. PMID:23332320

Liu, Pingsheng; Song, Jie

2013-01-01

154

Hydroxyapatite coating for titanium fibre mesh scaffold enhances osteoblast activity and bone tissue formation.  

PubMed

This study investigated the bone regeneration properties of titanium fibre mesh as a tissue engineering material. A thin hydroxyapatite (HA) coating on the titanium fibre web was created using the developed molecular precursor method without losing the complex interior structure. HA-coated titanium fibre mesh showed apatite crystal formation in vitro in a human osteoblast culture. Titanium fibre mesh discs with or without a thin HA coating were implanted into rat cranial bone defects, and the animals were killed at 2 and 4 weeks. The in vivo experience revealed that the amount of newly formed bone was significantly higher in the HA-coated titanium fibre mesh than in the non-coated titanium fibre mesh 2 weeks after implantation. These results suggest that thin HA coating enhances osteoblast activity and bone regeneration in the titanium fibre mesh scaffold. Thin HA-coating improved the ability of titanium fibre mesh to act as a bone regeneration scaffold. PMID:22513355

Hirota, Makoto; Hayakawa, Tohru; Yoshinari, Masao; Ametani, Akihiro; Shima, Takaki; Monden, Yuka; Ozawa, Tomomichi; Sato, Mitsunobu; Koyama, Chika; Tamai, Naoto; Iwai, Toshinori; Tohnai, Iwai

2012-10-01

155

Antibacterial properties of Ag-doped hydroxyapatite layers prepared by PLD method  

NASA Astrophysics Data System (ADS)

Thin hydroxyapatite (HA), silver-doped HA and silver layers were prepared using a pulsed laser deposition method. Doped layers were ablated from silver/HA targets. Amorphous and crystalline films of silver concentrations of 0.06 at.%, 1.2 at.%, 4.4 at.%, 8.3 at.% and 13.7 at.% were synthesized. Topology was studied using scanning electron microscopy and atomic force microscopy. Contact angle and zeta potential measurements were conducted to determine the wettability, surface free energy and electric surface properties. In vivo measurement (using Escherichia coli cells) of antibacterial properties of the HA, silver-doped HA and silver layers was carried out. The best antibacterial results were achieved for silver-doped HA layers of silver concentration higher than 1.2 at.%.

Jelínek, Miroslav; Kocourek, Tomáš; Jurek, Karel; Remsa, Jan; Mikšovský, Jan; Weiserová, Marie; Strnad, Jakub; Luxbacher, Thomas

2010-12-01

156

Nanostructural Characteristics of Vacuum Cold-Sprayed Hydroxyapatite/Graphene-Nanosheet Coatings for Biomedical Applications  

NASA Astrophysics Data System (ADS)

Development of novel biocompatible nanomaterials has provided insights into their potential biomedical applications. Bulk fabrication of the nanomaterials in the form of coatings remains challenging. Here, we report hydroxyapatite (HA)/graphene-nanosheet (GN) composite coatings deposited by vacuum cold spray (VCS). Significant shape changes of HA nanograins during the coating deposition were revealed. The nanostructural features of HA together with curvature alternation of GN gave rise to dense structures. Based on the microstructural characterization, a structure model was proposed to elucidate the nanostructural characteristics of the HA-GN nanocomposites. Results also showed that addition of GN significantly enhanced fracture toughness and elastic modulus of the HA-based coatings, which is presumably accounted for by crack bridging offered by GN in the composites. The VCS HA-GN coatings show potential for biomedical applications for the repair or replacement of hard tissues.

Liu, Yi; Huang, Jing; Li, Hua

2014-10-01

157

Bioactive rosette nanotube-hydroxyapatite nanocomposites improve osteoblast functions.  

PubMed

Inspired from biological systems, small synthetic organic molecules expressing the hydrogen bonding arrays of the DNA bases guanine and cytosine were prepared, and their self-assembly into rosette nanotubes (RNTs) was investigated. Due to their unique biological, physicochemical, and mechanical properties, RNTs could serve as the next generation of injectable orthopedic materials. In this study, a self-assembling module (termed twin base linkers or TBL) was synthesized, and the corresponding RNTs were used as bioactive components in composites of poly (2-hydroxyethyl methacrylate) (pHEMA) and hydroxyapatite (HA) nanoparticles (termed TBL/HA/pHEMA). The properties of these composites were characterized for solidification time, surface morphology, mechanical properties, and cytocompatibility. The experimental conditions were optimized to achieve solidification within 2-40 min, offering a range of properties for orthopedic applications. Composites with 20 wt% HA nanoparticles had a compressive strength (37.1 MPa) and an ultimate tensile stress (14.7 MPa) similar to that of a natural vertebral disc (5-30 MPa). Specifically, the TBL (0.01 mg/mL)/HA(20 wt%)/pHEMA composites improved long-term functions of osteoblasts (or bone-forming cells) in terms of collagen synthesis, alkaline phosphatase activity, and calcium deposition. Moreover, this composite inhibited fibroblast adhesion, thus decreasing the potential for undesirable fibrous tissue formation. In summary, this in vitro study provided evidence that TBL/HA/pHEMA composites are promising injectable orthopedic implant materials that warrant further mechanistic and in vivo studies. PMID:22530958

Sun, Linlin; Zhang, Lijie; Hemraz, Usha D; Fenniri, Hicham; Webster, Thomas J

2012-09-01

158

The effect of RGD peptides on osseointegration of hydroxyapatite biomaterials  

PubMed Central

Given that hydroxyapatite (HA) biomaterials are highly efficient at adsorbing proadhesive proteins, we questioned whether functionalizing HA with RGD peptides would have any benefit. In this study, we implanted uncoated or RGD-coated HA disks into rat tibiae for 30 minutes to allow endogenous protein adsorption, and then evaluated mesenchymal stem cell (MSC) interactions with the retrieved disks. These experiments revealed that RGD, when presented in combination with adsorbed tibial proteins (including fibronectin, vitronectin and fibrinogen), has a markedly detrimental effect on MSC adhesion and survival. Moreover, analyses of HA disks implanted for 5 days showed that RGD significantly inhibits total bone formation as well as the amount of new bone directly contacting the implant perimeter. Thus, RGD, which is widely believed to promote cell/biomaterial interactions, has a negative effect on HA implant performance. Collectively these results suggest that, for biomaterials that are highly interactive with the tissue microenvironment, the ultimate effects of RGD will depend upon how signaling from this peptide integrates with endogenous processes such as protein adsorption. PMID:18440064

Hennessy, KM; Clem, WC; Phipps, MC; Sawyer, AA; Shaikh, FM; Bellis, SL

2008-01-01

159

Fabrication of glass microspheres with conducting surfaces  

DOEpatents

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming a conducting coating on the surface of the microspheres.

Elsholz, W.E.

1982-09-30

160

Fabrication of glass microspheres with conducting surfaces  

DOEpatents

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming a conducting coating on the surface of the microspheres.

Elsholz, William E. (Acampo, CA)

1984-01-01

161

A new approach for the one-step synthesis of bioactive PS vs. PMMA silica hybrid microspheres as potential drug delivery systems.  

PubMed

In this work, hybrid microspheres were prepared in a two-step process combining the emulsifier free-emulsion polymerization and the sol-gel coating method. In the first step, polystyrene (St) and poly(methyl methacrylate) (PMMA) microspheres were prepared as sacrificial template and in the second step a silanol shell was fabricated. The functionalized surface of the hybrid microspheres by silane analogs (APTES, TEOS) resulted in enhanced effects. The hollow microspheres were resulted either in an additional step by template dissolution and/or during the coating process. The microspheres' surface interactions and the size distribution were optimized by treatment in simulated body fluids, which resulted in the in vitro prediction of bioactivity. The bioassay test indicated that the induced hydroxyapatite resembled in structure to naturally occurring bone apatite. The drug doxorubicin (DOX) was used as a model entity for the evaluation of drug loading and release. The drug release study was performed in two different pH conditions, at acidic (pH=4.5) close to cancer cell environment and at slightly basic pH (pH=7.4) resembling the orthopedic environment. The results of the present study indicated promising hybrid microspheres for the potential application as drug delivery vehicles, for dual orthopedic functionalities in bone defects, bone inflammation, bone cancer and bone repair. PMID:24670261

Angelopoulou, A; Efthimiadou, E K; Boukos, N; Kordas, G

2014-05-01

162

Electron microscopy of biomaterials based on hydroxyapatite  

SciTech Connect

Three types of biomaterials based on hydroxyapatite are synthesized and investigated. Hydroxyapatite nanocrystals or microcrystals precipitated from low-temperature aqueous solutions serve as the initial material used for preparing spherical porous granules approximately 300-500 {mu}m in diameter. Sintering of hydroxyapatite crystals at a temperature of 870 deg. C for 2 h or at 1000 deg. C (for 3 h) + 1200 deg. C (for 2 h) brings about the formation of solid ceramics with different internal structures. According to the electron microscopic data, the ceramic material prepared at 870 deg. C is formed by agglomerated hydroxyapatite nanocrystals, whereas the ceramics sintered at 1200 deg. C (with a bending strength of the order of 100 MPa) are composed of crystal blocks as large as 2 {mu}m. It is established that all the biomaterials have a single-phase composition and consist of the hydroxyapatite with a structure retained up to a temperature of 1200 deg. C.

Suvorova, E. I., E-mail: suvorova@ns.crys.ras.ru; Klechkovskaya, V. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Komarov, V. F.; Severin, A. V.; Melikhov, I. V. [Moscow State University (Russian Federation); Buffat, P. A. [Ecole Polytechnique Federale de Lausanne, Centre Interdisciplinaire de Microscopie Electronique (Switzerland)

2006-10-15

163

Lack of repair of rat skull critical size defect treated with bovine morphometric protein bound to microgranular bioabsorbable hydroxyapatite  

Microsoft Academic Search

The ability of a pool of bovine bone morphogenetic proteins bound to synthetic microgranular hydroxyapatite (BMPb-HA) to stimulate bone repair was determined in rat critical size defects. An 8-mm diameter defect was created in the calvaria of 25 rats. In 15 rats, the defects were filled with BMPb-HA homogenized with blood (experimental group), and in 10 rats the defects were

Gabriel Ramalho Ferreira; Tania Mary Cestari; José Mauro Granjeiro; Rumio Taga

2004-01-01

164

The effect of plasma spraying power on the structure and mechanical properties of hydroxyapatite deposited onto carbon\\/carbon composites  

Microsoft Academic Search

This paper deals with the effect of plasma spraying power on hydroxyapatite (HA) coatings on carbon\\/carbon composites (C\\/C composites). The microstructure and phase composition of the as-sprayed coatings have been examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The shear strength of the HA coatings–C\\/C substrates was detected on a RGD-5 tensile testing machine. Results indicate that

Jin-Ling Sui; Mu-Sen Li; Yu-Peng Lu; Yun-Qiang Bai

2005-01-01

165

In vitro and in vivo evaluation of degradability of hydroxyapatite coatings synthesized by ion beam-assisted deposition  

Microsoft Academic Search

Degradability is among the most important properties in the biomedical field, which is crucial to bone apposition on implants, bone-implant bonding and implantation longevity. The present paper evaluated the degradability of ion beam-assisted deposition (IBAD) hydroxyapatite (HA) coatings in vitro and in vivo. In vitro testing showed that IBAD HA coatings degraded little in 37°C sterile Hank’s physiologic (pH 5.2)

Z. S Luo; F. Z Cui; Q. L Feng; H. D Li; X. D Zhu; M Spector

2000-01-01

166

New bone formation around porous hydroxyapatite wedge implanted in opening wedge high tibial osteotomy in patients with osteoarthritis  

Microsoft Academic Search

A porous hydroxyapatite (highly purified synthetic Ca10(PO4)6(OH)2) wedge was inserted into the tibia in 10 knees of 7 patients with osteoarthritis of the knee who underwent high tibial osteotomy. The interface of this HA wedge with bone was histologically examined in undecalcified specimens obtained at the time of hardware removal in all 10 knees, and total incorporation of the HA

Tomihisa Koshino; Tomoo Murase; Toshitaka Takagi; Tomoyuki Saito

2001-01-01

167

Advances in Microsphere Insulation Systems  

NASA Astrophysics Data System (ADS)

Microsphere insulation, typically consisting of hollow glass bubbles, combines in a single material the desirable properties that other insulations only have individually. The material has high crush strength, low density, is noncombustible, and performs well in soft vacuum. Microspheres provide robust, low-maintenance insulation systems for cryogenic transfer lines and dewars. They also do not suffer from compaction problems typical of perlite that result in the necessity to reinsulate dewars because of degraded thermal performance and potential damage to its support system. Since microspheres are load bearing, autonomous insulation panels enveloped with lightweight vacuum-barrier materials can be created. Comprehensive testing performed at the Cryogenics Test Laboratory located at the NASA Kennedy Space Center demonstrated competitive thermal performance with other bulk materials. Test conditions were representative of actual-use conditions and included cold vacuum pressure ranging from high vacuum to no vacuum and compression loads from 0 to 20 psi. While microspheres have been recognized as a legitimate insulation material for decades, actual implementation has not been pursued. Innovative microsphere insulation system configurations and applications are evaluated.

Allen, M. S.; Baumgartner, R. G.; Fesmire, J. E.; Augustynowicz, S. D.

2004-06-01

168

Optical trapping of coated microspheres.  

PubMed

In an optical trap, micron-sized dielectric particles are held by a tightly focused laser beam. The optical force on the particle is composed of an attractive gradient force and a destabilizing scattering force. We hypothesized that using anti-reflection-coated microspheres would reduce scattering and lead to stronger trapping. We found that homogeneous silica and polystyrene microspheres had a sharp maximum trap stiffness at a diameter of around 800 nm--the trapping laser wavelength in water--and that a silica coating on a polystyrene microsphere was a substantial improvement for larger diameters. In addition, we noticed that homogeneous spheres of a correct size demonstrated anti-reflective properties. Our results quantitatively agreed with Mie scattering calculations and serve as a proof of principle. We used a DNA stretching experiment to confirm the large linear range in detection and force of the coated microspheres and performed a high-force motor protein assay. These measurements show that the surfaces of the coated microspheres are compatible with biophysical assays. PMID:18772994

Bormuth, Volker; Jannasch, Anita; Ander, Marcel; van Kats, Carlos M; van Blaaderen, Alfons; Howard, Jonathon; Schäffer, Erik

2008-09-01

169

A Comparative Study on In Vitro Osteogenic Priming Potential of Electron Spun Scaffold PLLA/HA/Col, PLLA/HA, and PLLA/Col for Tissue Engineering Application  

PubMed Central

A comparative study on the in vitro osteogenic potential of electrospun poly-L-lactide/hydroxyapatite/collagen (PLLA/HA/Col, PLLA/HA, and PLLA/Col) scaffolds was conducted. The morphology, chemical composition, and surface roughness of the fibrous scaffolds were examined. Furthermore, cell attachment, distribution, morphology, mineralization, extracellular matrix protein localization, and gene expression of human mesenchymal stromal cells (hMSCs) differentiated on the fibrous scaffolds PLLA/Col/HA, PLLA/Col, and PLLA/HA were also analyzed. The electrospun scaffolds with a diameter of 200–950 nm demonstrated well-formed interconnected fibrous network structure, which supported the growth of hMSCs. When compared with PLLA/H%A and PLLA/Col scaffolds, PLLA/Col/HA scaffolds presented a higher density of viable cells and significant upregulation of genes associated with osteogenic lineage, which were achieved without the use of specific medium or growth factors. These results were supported by the elevated levels of calcium, osteocalcin, and mineralization (P<0.05) observed at different time points (0, 7, 14, and 21 days). Furthermore, electron microscopic observations and fibronectin localization revealed that PLLA/Col/HA scaffolds exhibited superior osteoinductivity, when compared with PLLA/Col or PLLA/HA scaffolds. These findings indicated that the fibrous structure and synergistic action of Col and nano-HA with high-molecular-weight PLLA played a vital role in inducing osteogenic differentiation of hMSCs. The data obtained in this study demonstrated that the developed fibrous PLLA/Col/HA biocomposite scaffold may be supportive for stem cell based therapies for bone repair, when compared with the other two scaffolds. PMID:25140798

Balaji Raghavendran, Hanumantha Rao; Puvaneswary, Subramaniam; Talebian, Sepehr; Raman Murali, Malliga; Vasudevaraj Naveen, Sangeetha; Krishnamurithy, G.; McKean, Robert; Kamarul, Tunku

2014-01-01

170

Electrochemical preparation of chitosan/hydroxyapatite composite coatings on titanium substrates.  

PubMed

Composite coatings containing brushite (CaHPO(4). 2H(2)O) and chitosan were prepared by electrochemical deposition. The brushite/chitosan composites were converted to hydroxyapatite/chitosan composites in aqueous solutions of sodium hydroxide. The coatings ranged from approximately 1 to 15% chitosan by weight. Qualitative assessment of the coatings showed adhesion significantly improved over that observed for electrodeposited coatings of pure HA. PMID:12889012

Redepenning, Jody; Venkataraman, Guhanand; Chen, Jun; Stafford, Nathan

2003-08-01

171

Behavior of Plasma-Sprayed Hydroxyapatite Coatings onto Carbon\\/carbon Composites in Simulated Body Fluid  

Microsoft Academic Search

Two types of hydroxyapatite (HA) coatings onto carbon\\/carbon composite (C\\/C composites) substrates, deposited by plasma spraying technique, were immersed in a simulated body fluid (SBF) in order to determine their behavior in conditions similar to the human blood plasma. Calcium ion concentration, pH value, microstructure, and phase compositions were analyzed. Results demonstrated that both the crystal Ca-P phases or the

Jin-Ling Sui; Wu Bo; Zhou Hai; Ning Cao; Mu-Sen Li

2007-01-01

172

Use of hydroxyapatite ceramics for treatment of nonunited osseous defect after open fracture of lower limbs  

Microsoft Academic Search

Introduction  Osseous defects in nonunited open fracture of the lower limbs are difficult to treat. Autogenous bone grafting is a promising\\u000a treatment options, but a finite amount of autogenous bone graft is available from each individual and donor site morbidity\\u000a remains a problem. These limitations have prompted the development and use of synthetic biomaterials such as hydroxyapatite\\u000a (HA) ceramics. However, little

Takanobu Nakase; Masakazu Fujii; Akira Myoui; Noriyuki Tamai; Yasuhisa Hayaishi; Takafumi Ueda; Masayuki Hamada; Hideo Kawai; Hideki Yoshikawa

2009-01-01

173

Nanostructured titania\\/hydroxyapatite composite coatings deposited by high velocity oxy-fuel (HVOF) spraying  

Microsoft Academic Search

Pure nanostructured titania (TiO2) and blends with 10 and 20wt% hydroxyapatite (HA) powders were sprayed onto Ti–6Al–4V substrates using a high velocity oxy-fuel (HVOF) system. The feedstock powders employed in this work were engineered to exhibit similar particle size distributions in order to generate similar values of particle temperature and velocity in the spray jet. By achieving these characteristics it

M. Gaona; R. S. Lima; B. R. Marple

2007-01-01

174

Adsorption of chondroitin-4-sulphate and heparin onto hydroxyapatite—effect of bovine serum albumin  

Microsoft Academic Search

The adsorption of chondroitin-4-sulphate (C4S) and heparin onto hydroxyapatite (HA) has been studied in the absence and presence of bovine serum albumin (BSA). Isotherm data at pH 6.8 have shown that BSA in solution has no effect on C4S adsorption, whereas heparin affinity and adsorption decrease. These data suggest that C4S and BSA bind to different calcium sites on the

Diana T. Hughes Wassell; Graham Embery

1997-01-01

175

Effects of debinding parameters on powder injection molded Ti6Al4V\\/HA composite parts  

Microsoft Academic Search

Titanium alloy-hydroxyapatite(Ti-6Al-4V\\/HA) composite powders produced by a ceramic slurry were mixed with a multi-component binder system in the powder injection molding process. The binder system comprises mainly of natural wax, fatty acid wax, stearic acid, poly-oxialkyen-etherand olefln-hydrocarbons. After molding, the binder system was removed by conventional thermal debinding. The effects of heating rate and gas flow rate on the quality

E. S. Thian; N. H. Loh; K. A. Khor; S. B. Tor

2001-01-01

176

Production of hydroxyapatite layers on the plasma electrolytically oxidized surface of titanium alloys.  

PubMed

Hydroxyapatite (HA) is a bioactive material that is widely used for improving the osseointegration of titanium dental implants. Titanium can be coated with HA by various methods, such as chemical vapor deposition (CVD), thermal spray, or plasma spray. HA coatings can also be grown on titanium surfaces by hydrothermal, chemical, and electrochemical methods. Plasma electrolytic oxidation (PEO), or microarc oxidation (MAO), is an electrochemical method that enables the production of a thick porous oxide layer on the surface of a titanium implant. If the electrolyte in which PEO is performed contains calcium and phosphate ions, the oxide layer produced may contain hydroxyapatite. The HA content can then be increased by subsequent hydrothermal treatment. The HA thus produced on titanium surfaces has attractive properties, such as a high porosity, a controllable thickness, and a considerable density, which favor its use in dental and bone surgery. This review summarizes the state of the art and possible further development of PEO for the production of HA on Ti implants. PMID:25175246

Lugovskoy, Alex; Lugovskoy, Svetlana

2014-10-01

177

Fabrication and characterization of plasma-sprayed HA/SiO(2) coatings for biomedical application.  

PubMed

Fused silica powder has been mixed with hydroxyapatite (HA) powder and plasma sprayed by using gas tunnel-type plasma jet. The influence of silica content (10 wt% and 20 wt%) on the microstructure and mechanical properties of HA-silica coatings was investigated. For investigating the microstructure and mechanical properties of HA-silica coatings, SUS 304 stainless steel was used as substrate material. The spraying was carried out on roughened substrate in an atmospheric chamber. Scanning electron microscope micrographs of cross-sectioned HA/SiO(2) coatings showed that the sprayed HA coatings with 10 and 20 wt% SiO(2) have dense structure with low porosity compared to the pure HA coatings. On the other hand, as the amount of silica was increased the coatings became denser, harder and exhibited high abrasive wear resistance. The presence of silica significantly improved the adhesive strength of HA/SiO(2) coatings mainly due to the increase in bonding strength of the coating at the interface. PMID:19627776

Morks, M F

2008-01-01

178

Preparation of enhanced HA coating on H 2O 2-treated carbon\\/carbon composite by induction heating and hydrothermal treatment methods  

Microsoft Academic Search

An adherent hydroxyapatite (HA) coating was applied onto H2O2-treated carbon\\/carbon composite (HT–C\\/C) substrate by induction heating and hydrothermal treatment techniques. Specimens of C\\/C were initially modified by immersed in an autoclave with 2M H2O2 solution at 433K, and then coated with monetite crystals by induction heating method. Subsequently, monetite coating on HT–C\\/C was converted to HA coating by hydrothermal treatment

Xiong Xin-bo; Zeng Xie-rong; Zou Chun-li

2009-01-01

179

Strong bonding strength between HA and (NH 4) 2S 2O 8-treated carbon\\/carbon composite by hydrothermal treatment and induction heating  

Microsoft Academic Search

Carbon\\/carbon composite with hydroxyapatite (HA) coating is an attractive material in the dental and orthopedic fields, but the reported bonding strength between them was very poor. In this study, a compact crystalline HA coating on (NH4)2S2O8-treated C\\/C substrate about 10?m in width was obtained by hydrothermal treatment and induction heating. The microstructure, composition and morphologies of the as-prepared coatings were

Xiong Xin-bo; Zeng Xie-rong; Zou Chun-li; Zhou Ji-Zhao

2009-01-01

180

Electrospun polyvinyl alcohol-collagen-hydroxyapatite nanofibers: a biomimetic extracellular matrix for osteoblastic cells  

NASA Astrophysics Data System (ADS)

The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

Song, Wei; Markel, David C.; Wang, Sunxi; Shi, Tong; Mao, Guangzhao; Ren, Weiping

2012-03-01

181

Pulsed laser deposition of silicon substituted hydroxyapatite coatings from synthetical and biological sources  

NASA Astrophysics Data System (ADS)

Silicon substituted hydroxyapatite (Si-HA) is a new material with an enhanced bioactibity and it can be produced by chemical synthesis. Nevertheless, the coating of metallic substrates with a bioactive material is a common method nowadays to improve its integration with the receptor bone. Si-HA films were deposited by pulsed laser deposition (PLD), using targets composed of mixtures of HA with different Si containing sources such as SiO 2 and diatomaceous earth. The Si-HA films were characterized in terms of structure and chemical composition by spectroscopic techniques (FTIR, XPS), and several ion beam techniques (RBS, PIXE). The analysis revealed that the Si is successfully incorporated into the HA structure, as well as traces of other elements such as Na, Fe or K.

Solla, E. L.; González, P.; Serra, J.; Chiussi, S.; León, B.; López, J. García

2007-12-01

182

Hydroxyapatite-poly(L-lactide) nanohybrids via surface-initiated ATRP for improving bone-like apatite-formation abilities  

NASA Astrophysics Data System (ADS)

It is important to improve the compatibility of hydroxyapatite (HA) nanoparticles in biodegradable polyesters to obtain desirable nanocomposites for bone tissue engineering applications. Polymer grafting has been proven an efficient way to get nanohybrids with good dispersibility in polymeric matrixes. In this paper, a new strategy to prepare HA-poly(L-lactide) (PLLA) nanohybrids was developed, where PLLA oligomers were grafted from HA nanoparticle surfaces via surface-initiated atom transfer radical polymerization (ATRP) of methylacrylate group terminated PLLA macromonomers (PLLA-MA). HA with the derived ATRP initiators was obtained by (1) preparation of HA from precursors in the presence of 3-aminopropyl-triethoxysilane (APTS) to produce the HA surface with terminal sbnd NH2 groups (HA-NH2) and (2) reaction of the sbnd NH2 groups of the HA-NH2 nanoparticles with 2-bromoisobutyryl bromide (BIBB) to produce the 2-bromoisobutyryl-immobilized nanoparticles (HA-Br). The obtained HA-PLLA nanohybrids demonstrated good dispersibility in chloroform. With the good dispersion of HA-PLLA nanohybrids in PLLA matrix, the resultant PLLA/HA-PLLA nanocomposites could much faster induce bone-like apatite-formation in simulated body fluids (SBF) than the PLLA/HA counterparts where the HA nanoparticles aggregated heavily. With the versatility of ATRP, properly, grafting oligomeric PLLA chains from HA nanoparticle surfaces is an effective means for the design of novel HA-polymer biohybrids for future bone tissue engineering applications.

He, Jiqing; Yang, Xiaoping; Mao, Jiaofu; Xu, Fujian; Cai, Qing

2012-07-01

183

Characterization of Multiwalled Carbon Nanotube-Reinforced Hydroxyapatite Composites Consolidated by Spark Plasma Sintering  

PubMed Central

Pure HA and 1, 3, 5, and 10?vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day. PMID:24724100

Kim, Duk-Yeon; Han, Young-Hwan; Lee, Jun Hee; Kang, Inn-Kyu; Jang, Byung-Koog; Kim, Sukyoung

2014-01-01

184

Freeze-cast hydroxyapatite scaffolds for bone tissue engineering applications.  

PubMed

Freeze casting of aqueous suspensions was investigated as a method for preparing porous hydroxyapatite (HA) scaffolds for eventual application to bone tissue engineering. Suspensions of HA particles (10-20 volume percent) were frozen unidirectionally in a cylindrical mold placed on a cold steel substrate (-20 degrees C). After sublimation of the ice, sintering for 3 h at 1350 degrees C produced constructs with dense HA lamellae, with porosity of approximately 50%, and inter-lamellar pore widths of 5-30 microm. These constructs had compressive strengths of 12 +/- 1 MPa and 5 +/- 1 MPa in the directions parallel and perpendicular to the freezing direction, respectively. Manipulation of the microstructure was achieved by modifying the solvent composition of the suspension used for freeze casting. The use of water-glycerol mixtures (20 wt% glycerol) resulted in the production of constructs with finer pores (1-10 microm) and a larger number of dendritic growth connecting the HA lamellae, and higher strength. On the other hand, the use of water-dioxane mixtures (60 wt% dioxane) resulted in a cellular-type microstructure with larger pores (90-110 microm). The mechanical response showed high strain tolerance (5-10% at the maximum stress), high strain for failure (>20%) and sensitivity to the loading rate. The favorable mechanical behavior of the porous constructs, coupled with the ability to modify their microstructure, indicates the potential of the present freeze casting route for the production of porous scaffolds for bone tissue engineering. PMID:18458369

Fu, Qiang; Rahaman, Mohamed N; Dogan, Fatih; Bal, B Sonny

2008-06-01

185

Stability of hydroxyapatite while processing short-fibre reinforced hydroxyapatite ceramics.  

PubMed

Reinforcement by short fibres has been adapted from modern ceramic processing technologies to achieve an improvement of structural properties of hydroxyapatite. However, the influence of the reinforcement fibres on the thermochemical behaviour of the hydroxyapatite has yet to be clarified comprehensively. Titanium, alumina and 316L-stainless steel, all materials with a proven record as implant materials, were chosen as reinforcement materials. Short fibres of these materials were incorporated in a matrix of hydroxyapatite to toughen the hydroxyapatite. Composites were processed by sintering in air, hot isostatic pressing and a method combining sintering in inert gas atmosphere and hot isostatic pressing. PMID:9430334

Knepper, M; Moricca, S; Milthorpe, B K

1997-12-01

186

Chondroitin sulfate template-mediated biomimetic synthesis of nano-flake hydroxyapatite  

Microsoft Academic Search

By Ca(NO3)2·4H2O and (NH4)3PO4·3H2O as reagents and chondroitin sulfate (ChS) as a template, nano-flake hydroxyapatite (HA) is synthesized using a biomimetic method according to the biomineralization theory. HA crystals obtained are characterized in crystalline phase, microstructure, chemical composition and morphology by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), transmission electron microscopy (TEM) and elemental analysis respectively. UV–vis spectrum is

Dan He; Xiufeng Xiao; Fang Liu; Rongfang Liu

2008-01-01

187

Photocatalytic and Antibacterial Activity of Titanium, Fluorine and Silver Co-Substituted Hydroxyapatite  

NASA Astrophysics Data System (ADS)

Synthetic hydroxyapatite (HA), an analogue of the mineral component of bone tissue has been widely used in medicine as bone replacing material. To impart specific properties, HA can be chemically modified by anionic and cationic substitutions during synthesis. Thus the present study was focused in synthesizing nanocrystalline Ti, Ag and F co-substituted HA by microwave synthesis. The prepared powders were characterized by XRD and FTIR for their crystal size, cystallinity and functional groups respectively. XRD spectra reveal that crystal size of prepared powders was in the range of 21-25 nm in as synthesized condition and 45-51 nm in 900 ?C heat-treated condition. Complete decomposition of HA to tri calcium phosphate was observed for Ti substituted HA powder after heat-treatment. Addition of F improved the thermal stability of Ti substituted HA as indicated by predominant phase of HA after heat-treatment. The photocatalytic activity of co-substituted HA powders was examined by degradation of methylene blue (5 × 10-5 M concentration) under visible light irradiation and the results were compared with pure HA. The degradation efficiency of co-substituted HA with respect to methylene blue was twice as high as that of pure HA. Ti and Ag has improved the visible light photocatalytic activity of HA, further F co-substitution has not affected the photocatalytic activity of substituted HA. The antibacterial effect of prepared powders was observed against 1 × 105 cells/mL of Escherichia coli using spread plate method at 24 h incubation period. Ag co-substituted HA showed complete inhibition of growth of Escherichia coli. Thus, among Ti, Ti-F, Ti-F-Ag substituted HA powders, Ti-F-Ag co-substituted HA with excellent visible light photocatalytic activity and anti-bacterial property is expected to be a potential candidate for biomedical applications.

Sandhyarani, M.; Rameshbabu, N.; Venkateswarlu, K.; Ravisankar, K. V.; Ashok, M.; Anandan, S.

188

Development of Risperidone PLGA Microspheres.  

PubMed

The aim of this study was to design and evaluate biodegradable PLGA microspheres for sustained delivery of Risperidone, with an eventual goal of avoiding combination therapy for the treatment of schizophrenia. Two PLGA copolymers (50?:?50 and 75?:?25) were used to prepare four microsphere formulations of Risperidone. The microspheres were characterized by several in vitro techniques. In vivo studies in male Sprague-Dawley rats at 20 and 40?mg/kg doses revealed that all formulations exhibited an initial burst followed by sustained release of the active moiety. Additionally, formulations prepared with 50?:?50 PLGA had a shorter duration of action and lower cumulative AUC levels than the 75?:?25 PLGA microspheres. A simulation of multiple dosing at weekly or 15-day regimen revealed pulsatile behavior for all formulations with steady state being achieved by the second dose. Overall, the clinical use of Formulations A, B, C, or D will eliminate the need for combination oral therapy and reduce time to achieve steady state, with a smaller washout period upon cessation of therapy. Results of this study prove the suitability of using PLGA copolymers of varying composition and molecular weight to develop sustained release formulations that can tailor in vivo behavior and enhance pharmacological effectiveness of the drug. PMID:24616812

D'Souza, Susan; Faraj, Jabar A; Giovagnoli, Stefano; Deluca, Patrick P

2014-01-01

189

Development of Risperidone PLGA Microspheres  

PubMed Central

The aim of this study was to design and evaluate biodegradable PLGA microspheres for sustained delivery of Risperidone, with an eventual goal of avoiding combination therapy for the treatment of schizophrenia. Two PLGA copolymers (50?:?50 and 75?:?25) were used to prepare four microsphere formulations of Risperidone. The microspheres were characterized by several in vitro techniques. In vivo studies in male Sprague-Dawley rats at 20 and 40?mg/kg doses revealed that all formulations exhibited an initial burst followed by sustained release of the active moiety. Additionally, formulations prepared with 50?:?50 PLGA had a shorter duration of action and lower cumulative AUC levels than the 75?:?25 PLGA microspheres. A simulation of multiple dosing at weekly or 15-day regimen revealed pulsatile behavior for all formulations with steady state being achieved by the second dose. Overall, the clinical use of Formulations A, B, C, or D will eliminate the need for combination oral therapy and reduce time to achieve steady state, with a smaller washout period upon cessation of therapy. Results of this study prove the suitability of using PLGA copolymers of varying composition and molecular weight to develop sustained release formulations that can tailor in vivo behavior and enhance pharmacological effectiveness of the drug. PMID:24616812

D'Souza, Susan; Faraj, Jabar A.; Giovagnoli, Stefano; DeLuca, Patrick P.

2014-01-01

190

Electrostatically Tuned Interactions in Silica Microsphere-Polystyrene Nanoparticle Mixtures  

E-print Network

Electrostatically Tuned Interactions in Silica Microsphere-Polystyrene Nanoparticle Mixtures Angel mechanism in binary mixtures of silica microspheres and polystyrene nanoparticles. By selectively tuning of silica microspheres and polystyrene nanoparticles whose mutual electrostatic interactions can be tuned

Lewis, Jennifer

191

PLLA-HA composites: Synthesis and characterization  

NASA Astrophysics Data System (ADS)

A composite based on PLLA -HA was prepared by the solvent casting technique and characterized. An interaction between the polymer matrix and HA through the carbonyl and phosphate groups was obtained by FTIR . The several thermal transitions of PLLA were evaluated by DSC: the glass transition, crystallization, cold crystallization, melt-recrystallization and melting. The addition of HA to PLLA matrix increases its glass transition temperature and no major changes on the melting temperature and crystallinity were observed. The PLLA-HA composite showed better thermal stability than the neat polymer. The introduction of the nano-HA particles increased the decomposition temperature and the activation energy retarding the decomposition process.

Gonzalez, Gema; Albano, Carmen; Palacios, Jordana

2012-07-01

192

Use of hydroxyapatite cement in pediatric craniofacial reconstructive surgery: strategies for avoiding complications.  

PubMed

The emergence of powdered hydroxyapatite (HA) has dramatically expanded the repertoire of reconstructive tools for craniofacial surgeons. Although several groups have reported mixed success using HA powder, to date there have been few large series retrospective reviews of HA use in an exclusively pediatric population. The purpose of our study was to assess the incidence of complications using a single surgeon's experience in an entirely pediatric cohort of patients. We present 78 pediatric patients (mean age, 9 [SD, 5.1] years; 26 girls, 52 boys) who have undergone craniofacial reconstruction with HA powder in the form of Mimix or BoneSource (mean, 57.3 [SD, 27.9] g). From this cohort, we discuss in detail 7 patients who experienced complications after their reconstruction with HA. These complications were related to trauma, infection, and exposure. Of these 7 patients with problems, 6 required eventual HA removal. In addition, all 7 patients who had complications after HA reported having a traumatic event with respect to their cranial reconstruction before presenting with a complication. Our series concludes that HA powder is a safe and effective material for use in pediatric craniofacial reconstruction. When certain principles are not violated, meticulous hemostasis and surgical planning are of paramount importance to reduce the incidence of seroma, exposure, and infection of the overlying HA placement. However, should these complications arise, prompt removal of HA is usually necessary. PMID:20613591

Singh, Kimberly A; Burstein, Fernando D; Williams, Joseph K

2010-07-01

193

Effects of zinc-substituted nano-hydroxyapatite coatings on bone integration with implant surfaces*  

PubMed Central

Objective: The purpose of this study was to investigate the effects of a zinc-substituted nano-hydroxyapatite (Zn-HA) coating, applied by an electrochemical process, on implant osseointegraton in a rabbit model. Methods: A Zn-HA coating or an HA coating was deposited using an electrochemical process. Surface morphology was examined using field-emission scanning electron microscopy. The crystal structure and chemical composition of the coatings were examined using an X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). A total of 78 implants were inserted into femurs and tibias of rabbits. After two, four, and eight weeks, femurs and tibias were retrieved and prepared for histomorphometric evaluation and removal torque (RTQ) tests. Results: Rod-like HA crystals appeared on both implant surfaces. The dimensions of the Zn-HA crystals seemed to be smaller than those of HA. XRD patterns showed that the peaks of both coatings matched well with standard HA patterns. FTIR spectra showed that both coatings consisted of HA crystals. The Zn-HA coating significantly improved the bone area within all threads after four and eight weeks (P<0.05), the bone to implant contact (BIC) at four weeks (P<0.05), and RTQ values after four and eight weeks (P<0.05). Conclusions: The study showed that an electrochemically deposited Zn-HA coating has potential for improving bone integration with an implant surface. PMID:23733429

Zhao, Shi-fang; Dong, Wen-jing; Jiang, Qiao-hong; He, Fu-ming; Wang, Xiao-xiang; Yang, Guo-li

2013-01-01

194

Sol–gel processing of hydroxyapatite  

Microsoft Academic Search

Hydroxyapatite, a calcium phosphate-based compound with numerous applications in the biological field was synthesized using the sol–gel processing route. The formation of hydroxyapatite and other compounds during the heat-treatment cycle were identified and characterized using thermal analyses and X-ray diffraction together with infrared and Raman spectroscopy. The influence of the addition of various organic alcohols (R–OH, R=CH3–, C2H5– and C3H8–)

A. Jillavenkatesa; R. A. Condrate SR

1998-01-01

195

Stability of hydroxyapatite while processing short-fibre reinforced hydroxyapatite ceramics  

Microsoft Academic Search

Reinforcement by short fibres has been adapted from modern ceramic processing technologies to achieve an improvement of structural properties of hydroxyapatite. However, the influence of the reinforcement fibres on the thermochemical behaviour of the hydroxyapatite has yet to be clarified comprehensively. Titanium, alumina and 316L-stainless steel, all materials with a proven record as implant materials, were chosen as reinforcement materials.

M. Knepper; S. Moricca; B. K. Milthorpe

1997-01-01

196

Evaluation of a setting reaction pathway in the novel composite TiHA-CSD bone cement by FT-Raman and FT-IR spectroscopy  

NASA Astrophysics Data System (ADS)

The aim of this study was to determine a setting reaction pathway in a novel, surgically handy implant material, based on calcium sulfate hemihydrate (CSH) and titanium doped hydroxyapatite (TiHA). The previous studies confirmed superior biological properties of TiHA in comparison to the undoped hydroxyapatite (HA) what makes it highly attractive for future medical applications. In this study the three types of titanium modified HA powders: untreated, calcined at 800 °C, sintered at 1250 °C and CSH were used to produce bone cements. The Fourier Transform-InfraRed (FT-IR) spectroscopy and Raman spectroscopy were applied to evaluate processes taking place during the setting of the studied materials. Our results undoubtedly confirmed that the reaction pathways and the phase compositions differed significantly for set cements and were dependent on the initial heat treatment of TiHA powder. Final materials were multiphase composites consisting of calcium sulfate dihydrate, bassanite, tricalcium phosphate, hydroxyapatite and calcium titanate (perovskite). The FT-IR and Scanning Electron Microscopy (SEM) measurements performed after the incubation of the cement samples in the simulated body fluid (SBF), indicate on high bioactive potential of the obtained bone cements.

Paluszkiewicz, Czes?awa; Czechowska, Joanna; ?lósarczyk, Anna; Paszkiewicz, Zofia

2013-02-01

197

HVOF-Sprayed Nano TiO2-HA Coatings Exhibiting Enhanced Biocompatibility  

NASA Astrophysics Data System (ADS)

Biomedical thermal spray coatings produced via high-velocity oxy-fuel (HVOF) from nanostructured titania (n-TiO2) and 10 wt.% hydroxyapatite (HA) (n-TiO2-10wt.%HA) powders have been engineered as possible future alternatives to HA coatings deposited via air plasma spray (APS). This approach was chosen due to (i) the stability of TiO2 in the human body (i.e., no dissolution) and (ii) bond strength values on Ti-6Al-4V substrates more than two times higher than those of APS HA coatings. To explore the bioperformance of these novel materials and coatings, human mesenchymal stem cells (hMSCs) were cultured from 1 to 21 days on the surface of HVOF-sprayed n-TiO2 and n-TiO2-10 wt.%HA coatings. APS HA coatings and uncoated Ti-6Al-4V substrates were employed as controls. The profiles of the hMSCs were evaluated for (i) cellular proliferation, (ii) biochemical analysis of alkaline phosphatase (ALP) activity, (iii) cytoskeleton organization (fluorescent/confocal microscopy), and (iv) cell/substrate interaction via scanning electron microscopy (SEM). The biochemical analysis indicated that the hMSCs cultured on n-TiO2-10 wt.%HA coatings exhibited superior levels of bioactivity than hMSCs cultured on APS HA and pure n-TiO2 coatings. The cytoskeleton organization demonstrated a higher degree of cellular proliferation on the HVOF-sprayed n-TiO2-10wt.%HA coatings when compared to the control coatings. These results are considered promising for engineering improved performance in the next generation of thermally sprayed biomedical coatings.

Lima, R. S.; Dimitrievska, S.; Bureau, M. N.; Marple, B. R.; Petit, A.; Mwale, F.; Antoniou, J.

2010-01-01

198

Microsphere coated substrate containing reactive aldehyde groups  

NASA Technical Reports Server (NTRS)

A synthetic organic resin is coated with a continuous layer of contiguous, tangential, individual microspheres having a uniform diameter preferably between 100 Angstroms and 2000 Angstroms. The microspheres are an addition polymerized polymer of an unsaturated aldehyde containing 4 to 20 carbon atoms and are covalently bonded to the substrate by means of high energy radiation grafting. The microspheres contain reactive aldehyde groups and can form conjugates with proteins such as enzymes or other aldehyde reactive materials.

Rembaum, Alan (Inventor); Yen, Richard C. K. (Inventor)

1984-01-01

199

Silicon-substituted hydroxyapatite composite coating by using vacuum-plasma spraying and its interaction with human serum albumin  

Microsoft Academic Search

The incorporation of silicon can improve the bioactivity of hydroxyapatite (HA). Silicon-substituted HA (Ca10(PO4)6?x\\u000a (SiO4)\\u000a x\\u000a (OH)2?x\\u000a , Si-HA) composite coatings on a bioactive titanium substrate were prepared by using a vacuum-plasma spraying method. The\\u000a surface structure was characterized by using XRD, SEM, XRF, EDS and FTIR. The bond strength of the coating was investigated\\u000a and XRD patterns showed that

Feng-juan Xiao; Lei Peng; Ying Zhang; Li-jiang Yun

2009-01-01

200

Interfacial stress transfer in a graphene nanosheet toughened hydroxyapatite composite  

NASA Astrophysics Data System (ADS)

In recent years, graphene has emerged as potential reinforcing nanofiller in the composites for structural engineering due to its extraordinary high elastic modulus and mechanical strength. As recognized, the transfer of stress from a low modulus matrix to a high-modulus reinforcing graphene and the interfacial behavior at a graphene-matrix interface is the fundamental issue in these composites. In the case of graphene nanosheet (GNS) reinforced hydroxyapatite (HA) composite, this research presented analytical models and simulated that the number of graphene layers of GNSs has little effect on the maximum axial stress (˜0.35 GPa) and the maximum shear stress (˜0.14 GPa) at a GNS-HA interface, and the energy dissipation by GNS pull-out decreases with increasing the number of graphene layers due to weak bonding between them. Also, GNS-HA interfacial delamination and/or GNS rupture were also indentified to be the two key failure mechanisms. The computed results are expected to facilitate a better understanding of the interfacial behavior at a GNS-ceramic interface and to achieve tough ceramics reinforced with GNSs.

Zhang, L.; Zhang, X. G.; Chen, Y.; Su, J. N.; Liu, W. W.; Zhang, T. H.; Qi, F.; Wang, Y. G.

2014-10-01

201

Hierarchically nanostructured hydroxyapatite: hydrothermal synthesis, morphology control, growth mechanism, and biological activity  

PubMed Central

Hierarchically nanosized hydroxyapatite (HA) with flower-like structure assembled from nanosheets consisting of nanorod building blocks was successfully synthesized by using CaCl2, NaH2PO4, and potassium sodium tartrate via a hydrothermal method at 200°C for 24 hours. The effects of heating time and heating temperature on the products were investigated. As a chelating ligand and template molecule, the potassium sodium tartrate plays a key role in the formation of hierarchically nanostructured HA. On the basis of experimental results, a possible mechanism based on soft-template and self-assembly was proposed for the formation and growth of the hierarchically nanostructured HA. Cytotoxicity experiments indicated that the hierarchically nanostructured HA had good biocompatibility. It was shown by in-vitro experiments that mesenchymal stem cells could attach to the hierarchically nanostructured HA after being cultured for 48 hours. Objective The purpose of this study was to develop facile and effective methods for the synthesis of novel hydroxyapatite (HA) with hierarchical nanostructures assembled from independent and discrete nanobuilding blocks. Methods A simple hydrothermal approach was applied to synthesize HA by using CaCl2, NaH2PO4, and potassium sodium tartrate at 200°C for 24 hours. The cell cytotoxicity of the hierarchically nanostructured HA was tested by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results HA displayed the flower-like structure assembled from nanosheets consisting of nanorod building blocks. The potassium sodium tartrate was used as a chelating ligand, inducing the formation and self-assembly of HA nanorods. The heating time and heating temperature influenced the aggregation and morphology of HA. The cell viability did not decrease with the increasing concentration of hierarchically nanostructured HA added. Conclusion A novel, simple and reliable hydrothermal route had been developed for the synthesis of hierarchically nanosized HA with flower-like structure assembled from nanosheets consisting of nanorod building blocks. The HA with the hierarchical nanostructure was formed via a soft-template assisted self-assembly mechanism. The hierarchically nanostructured HA has a good biocompatibility and essentially no in-vitro cytotoxicity. PMID:22619527

Ma, Ming-Guo

2012-01-01

202

Glass microspheres for medical applications  

NASA Astrophysics Data System (ADS)

Radioactive dysprosium lithium borate glass microspheres have been developed as biodegradable radiation delivery vehicles for the radiation synovectomy treatment of rheumatoid arthritis. Once injected into a diseased joint, the microspheres deliver a potent dose of radiation to the diseased tissue, while a non-uniform chemical reaction converts the glass into an amorphous, porous, hydrated dysprosium phosphate reaction product. The non-radioactive, lithium-borate component is dissolved from the glass (up to 94% weight loss), while the radioactive 165Dy reacts with phosphate anions in the body fluids, and becomes "chemically" trapped in a solid, dysprosium phosphate reaction product that has the same size as the un-reacted glass microsphere. Ethylene diamine tetraacetate (EDTA) chelation therapy can be used to dissolve the dysprosium phosphate reaction product after the radiation delivery has subsided. The dysprosium phosphate reaction product, which formed in vivo in the joint of a Sprague-Dawley rat, was dissolved by EDTA chelation therapy in <1 week, without causing any detectable joint damage. The combination of dysprosium lithium borate glass microspheres and EDTA chelation therapy provides an unique "tool" for the medical community, which can deliver a large dose (>100 Gy) of localized beta radiation to a treatment site within the body, followed by complete biodegradability. The non-uniform reaction process is a desirable characteristic for a biodegradable radiation delivery vehicle, but it is also a novel material synthesis technique that can convert a glass to a highly porous materials with widely varying chemical composition by simple, low-temperature, glass/solution reaction. The reaction product formed by nonuniform reaction occupies the same volume as the un-reacted glass, and after drying for 1 h at 300°C, has a specific surface area of ?200 m2/g, a pore size of ?30 nm, and a nominal crushing strength of ?10 MPa. Finally, rhenium glass microspheres, composed of micron-sized, metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050°C. A 50 mg injection of radioactive rhenium glass microspheres containing 3.7 GBq of 186Re and 8.5 GBq of 188Re could be used to deliver a 100 Gy dose to a cancerous tumor, while limiting the total body dose caused by rhenium dissolution to approximately 1 mGy.

Conzone, Samuel David

203

Effect of loading time on marginal bone loss around hydroxyapatite-coated implants  

PubMed Central

Objectives The objective of this study is compare the rate of marginal bone resorption around hydroxyapatite-coated implants given different loading times in order to evaluate their stability. Materials and Methods The study was conducted retrospectively for one year, targeting 41 patients whose treatment areas were the posterior maxilla and the mandible. Osstem TS III HA (Osstem Implant Co., Busan, Korea) and Zimmer TSV-HA (Zimmer Dental, Carlsbad, CA, USA), which employ the new hydroxyapatite coating technique, were used. The patients were divided into two groups - immediate and delayed loading - and the bone level at the time of loading commencement and after one year of loading was measured using periapical radiography. Differences between the groups were evaluated using Mann-Whitney (?=0.05). Results For all patients as a single group, the survival rate of the implants was 100%, and the mean marginal bone loss was 0.26±0.59 mm. In comparison of the differences by loading, mean marginal bone loss of 0.32±0.69 mm was recorded for the immediate loading group whereas the delayed loading group had mean marginal bone loss of 0.16±0.42 mm. However, the difference was not significant (P>0.05). Conclusion Within the limited observation period of one year, predictable survival rates can be expected when using immediately loaded hydroxyapatite-coated implants. PMID:24471037

Kim, Young-Kyun; Ahn, Kyo-Jin; Yun, Pil-Young; Kim, Minkyoung; Yang, Hong-So; Yi, Yang-Jin

2013-01-01

204

Synthesis of chitosan/hydroxyapatite membranes coated with hydroxycarbonate apatite for guided tissue regeneration purposes  

NASA Astrophysics Data System (ADS)

Chitosan, which is a non-toxic, biodegradable and biocompatible biopolymer, has been widely researched for several applications in the field of biomaterials. Calcium phosphate ceramics stand out among the so-called bioceramics for their absence of local or systemic toxicity, their non-response to foreign bodies or inflammations, and their apparent ability to bond to the host tissue. Hydroxyapatite (HA) is one of the most important bioceramics because it is the main component of the mineral phase of bone. The aim of this work was to produce chitosan membranes coated with hydroxyapatite using the modified biomimetic method. Membranes were synthesized from a solution containing 2% of chitosan in acetic acid (weight/volume) via the solvent evaporation method. Specimens were immersed in a sodium silicate solution and then in a 1.5 SBF (simulated body fluid) solution. The crystallinity of the HA formed over the membranes was correlated to the use of the nucleation agent (the sodium silicate solution itself). Coated membranes were characterized by means of scanning electron microscopy - SEM, X-ray diffraction - XRD, and Fourier transform infrared spectroscopy - FTIR. The results indicate a homogeneous coating covering the entire surface of the membrane and the production of a semi-crystalline hydroxyapatite layer similar to the mineral phase of human bone.

Fraga, Alexandre Félix; Filho, Edson de Almeida; Rigo, Eliana Cristina da Silva; Boschi, Anselmo Ortega

2011-02-01

205

Evaluation of Bone Healing on Sandblasted and Acid Etched Implants Coated with Nanocrystalline Hydroxyapatite: An In Vivo Study in Rabbit Femur  

PubMed Central

This study aimed at investigating if a coating of hydroxyapatite nanocrystals would enhance bone healing over time in trabecular bone. Sandblasted and acid etched titanium implants with and without a submicron thick coat of hydroxyapatite nanocrystals (nano-HA) were implanted in rabbit femur with healing times of 2, 4, and 9 weeks. Removal torque analyses and histological evaluations were performed. The torque analysis did not show any significant differences between the implants at any healing time. The control implant showed a tendency of more newly formed bone after 4 weeks of healing and significantly higher bone area values after 9 weeks of healing. According to the results from this present study, both control and nano-HA surfaces were biocompatible and osteoconductive. A submicron thick coating of hydroxyapatite nanocrystals deposited onto blasted and acid etched screw shaped titanium implants did not enhance bone healing, as compared to blasted and etched control implants when placed in trabecular bone. PMID:24723952

Melin Svanborg, Lory; Meirelles, Luiz; Franke Stenport, Victoria; Currie, Fredrik; Andersson, Martin

2014-01-01

206

Coupling system to a microsphere cavity  

NASA Technical Reports Server (NTRS)

A system of coupling optical energy in a waveguide mode, into a resonator that operates in a whispering gallery mode. A first part of the operation uses a fiber in its waveguide mode to couple information into a resonator e.g. a microsphere. The fiber is cleaved at an angle .PHI. which causes total internal reflection within the fiber. The energy in the fiber then forms an evanescent field and a microsphere is placed in the area of the evanescent field. If the microsphere resonance is resonant with energy in the fiber, then the information in the fiber is effectively transferred to the microsphere.

Iltchenko, Vladimir (Inventor); Maleki, Lute (Inventor); Yao, Steve (Inventor); Wu, Chi (Inventor)

2002-01-01

207

Characterization of Nano-Hydroxyapatite Synthesized from Sea Shells Through Wet Chemical Method  

NASA Astrophysics Data System (ADS)

Nano-hydroxyapatite (HA) was synthesized by a wet chemical reaction using powdered sea shells (CaO) as starting material which was converted to calcium hydroxide (Ca(OH)2) and subsequently reacted with phosphoric acid (H3PO4). Initially raw sea shells (CaCO3) were thermally converted to amorphous calcium oxide by heat treatment. Two sets of experiments were done; in the first experiment, HA powder was dried in an electric furnace and in the second experiment, the reactants were irradiated in a domestic microwave oven followed by microwave drying. In each set of experiments, the concentrations of the reactants were decreased gradually. HA was synthesized by slow addition of phosphoric acid (H3PO4) in to calcium hydroxide (Ca(OH)2) maintaining the pH of the solution at 10 to avoid the formation of calcium deficient apatites. In both the experiments, Ca:P ratio of 1.67 was maintained for the reagents. The synthesized samples showed X-ray diffraction (XRD) patterns corresponding to hydroxyapatite. The wet chemical process with furnace drying resulted in HA particles of size 7-34 nm, whereas microwave irradiated process yielded HA particles of size 34-102 nm as evidenced from XRD analyses. The above experimental work done by wet chemical synthesis to produce HA powder from sea shells is a simple processing method at room temperature. Microwave irradiation leads to uniform crystallite sizes as evident from this study, at differing concentrations of the reactants and is a comparatively easy method to synthesize HA. The high resolution scanning electron microscopy (HRSEM)/transmission electron microscopic (TEM) analyses revealed the characteristic rod-shaped nanoparticles of HA for the present study.

Santhosh, S.; Prabu, S. Balasivanandha

2012-10-01

208

Pulsed Laser Deposited Magnesium - Hydroxyapatite Composite Thin Film for Resorbable Magnesium Bone Implants  

NASA Astrophysics Data System (ADS)

This research reports on the fabrication and characterization of bioactive magnesium-hydroxyapatite (Mg-HA) composite coatings on magnesium substrates using pulsed laser deposition for implant applications. The samples were fabricated at room temperature (25 ºC) under high vacuum of the order 10 -6 Torr, using laser pulse ratios up to 50,000 pulses (x%Mg-(100- x)%HA). The samples were structurally characterized using scanning electron microscopy, energy dispersion x-ray spectroscopy, and x-ray diffractometry. The samples were further investigated for their biocorrosive, mechanical, and biocompatibility properties. The results obtained from potentiodynamic polarization study indicate that the corrosion resistance of the composite coating increases with increasing hydroxyapatite content in the composite coating. The observed corrosion potential for uncoated Mg, 70Mg--30HA, 50Mg--50HA, 10Mg--90HA, and 100HA were -1.59, -1.57, -1.54, -1.49, and -1.49 V, respectively. Electrochemical impedance spectroscopy results were consistent with treads observed in potentiodynamic polarization experiments. The mechanical properties of the fabricated films were studied using nanoindentation. The hardness and elastic modulus of the fabricated composite films increase consistently with increasing magnesium content in the film with hardness showing approximately 20% increase between consecutive Mg-HA samples, while the modulus values increased from 47 to 62 GPa. The biocompatibility of the coatings was also investigated by examining their interaction with selected cells lines, using MTT assay and live cell staining techniques. It was demonstrated that the modified surfaces resulted an increase in cell interactions and proliferation. Based on these results, Mg-HA coated magnesium could be used for bioresorbable implant where tunable corrosion and mechanical properties are needed.

Mensah-Darkwa, Kwadwo

209

Fabrication of Adipose-Derived Mesenchymal Stem Cell Aggregates using Biodegradable Porous Microspheres for Injectable Adipose Tissue Regeneration  

Microsoft Academic Search

Injectable mesenchymal stem cell aggregates were formed using hyaluronic acid (HA)-immobilized porous biodegradable microspheres for adipose tissue regeneration. Adipose tissue-derived mesenchymal stem cells (AMSCs) were aggregated in a controlled manner and differentiated into adipocytes by cultivating in a stirred suspension bioreactor. The resultant cellular aggregates were approx. 1700 ?m in diameter and exhibited fully differentiated adipocytes, as shown by immunocytochemistry

Hyun Jung Chung; Jin Sup Jung; Tae Gwan Park

2011-01-01

210

Engineering nanocages with polyglutamate domains for coupling to hydroxyapatite biomaterials and allograft bone  

PubMed Central

Hydroxyapatite (HA) is the principal constituent of bone mineral, and synthetic HA is widely used as a biomaterial for bone repair. Previous work has shown that polyglutamate domains bind selectively to HA and that these domains can be utilized to couple bioactive peptides onto many different HA-containing materials. In the current study we have adapted this technology to engineer polyglutamate domains into cargo-loaded nanocage structures derived from the P22 bacteriophage. P22 nanocages have demonstrated significant potential as a drug delivery system due to their stability, large capacity for loading with a diversity of proteins and other types of cargo, and ability to resist degradation by proteases. Site-directed mutagenesis was used to modify the primary coding sequence of the P22 coat protein to incorporate glutamate-rich regions. Relative to wild-type P22, the polyglutamate-modified nanocages (E2-P22) exhibited increased binding to ceramic HA disks, particulate HA and allograft bone. Furthermore, E2-P22 binding was HA selective, as evidenced by negligible binding of the nanocages to non-HA materials including polystyrene, agarose, and polycaprolactone (PCL). Taken together these results establish a new mechanism for the directed coupling of nanocage drug delivery systems to a variety of HA-containing materials commonly used in diverse bone therapies. PMID:23312905

Culpepper, Bonnie K.; Morris, David S.; Prevelige, Peter E.; Bellis, Susan L.

2013-01-01

211

Densification Process of OH Controlled Hydroxyapatite Ceramics by Spark Plasma Sintering  

SciTech Connect

Calcium hydroxyapatite, Ca10(PO4)6(OH)2:HA, is the inorganic principle component of natural bones and teeth. It has been already suggested that the amount of OH ion in the crystal structure of HA is closely related to the biocompatibility. The amount of OH ion in current HA, however, has not been controlled. In order to prepare more functional HA ceramics, the amount of OH ion must be controlled. In this study, HA ceramics with different OH amount were prepared from fine HA crystals by spark plasma sintering (SPS). In order to reveal the ideal sintering conditions for preparation of transparent ceramics, densification process on SPS was investigated. The samples were pressed uniaxialy under 60 MPa, and then they were heated by SPS at 800 deg. C, 900 deg. C and 1000 deg. C for 10 min with the heating rate of 25 deg. C{center_dot}min-1. The quantity of OH ion in HA ceramics sintered by SPS was decreased with increasing temperature of sintering. Transparent HA ceramics were prepared by SPS at 900 deg. C and 1000 deg. C. In analysis of the densification behavior during sintering of HA by SPS, dominant sintering mechanism was plastic flow of densification. Transparent ceramics should be the most suitable materials to investigate the interface between human cells and ceramics.

Kawagoe, D. [Institution of Fluid Science, Tohoku University, Aoba 6-6-20 Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Koga, Y.; Ishida, E. H.; Ioku, K. [Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20 Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2006-05-15

212

Characterization of hydroxyapatite containing a titania layer formed by anodization coupled with blasting.  

PubMed

Abstract Objectives. The modification of dental implant surface by increasing the surface roughness or/and altering chemical composition have been attempted. Among them, hydroxyapatite (HA) coatings are typically bioactive. On the other hand, titania coatings have good corrosion resistance and biocompatibility. Therefore, the objective of this study was to fabricate HA containing a titania layer using an HA blasting and anodization method to benefit from the advantages of both, followed by surface characterization and biocompatibility. Materials and methods. HA blasting was performed followed by microarc oxidation (MAO) using various applied voltages (100, 150, 200, 250 V). For surface characterization, the microstructure of the surface, surface phase and surface roughness were observed. Bonding strength was measured using a universal testing machine and potentiodynamic corrosion testing was performed. Biocompatibility was evaluated based on bioactivity and cell proliferation test. Results. The porous titanium oxide-containing HA was formed at 150 and 200 V. These surfaces were a lower corrosion current compared to the titanium treated only with HA blasting. In addition, composite treated titanium showed a rougher surface and tighter bonding strength compared to the titanium treated only with MAO. Biocompatibility demonstrated that HA/Titania composite layer on titanium showed a rapid HA precipitation and also enhanced cell proliferation. Conclusions. These results suggested that HA containing titania layer on titanium had not only excellent physicochemical, mechanical and electrochemical properties, but also improved bioactivity and biological properties that could be applied as material for a dental implant system. PMID:25005626

Kang, Min-Kyung; Moon, Seung-Kyun; Kwon, Jae-Sung; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2014-11-01

213

Enhanced osteoinductivity and osteoconductivity through hydroxyapatite coating of silk-based tissue-engineered ligament scaffold.  

PubMed

Hybrid silk scaffolds combining knitted silk fibers and silk sponge have been recently developed for use as ligament-alone grafts. Incorporating an osteoinductive phase into the ends of a ligament scaffold may potentially generate an integrated "bone-ligament-bone" graft and improve graft osteointegration with host bone. To explore the possible application of hydroxyapatite (HA) coating in the fabrication of osteoinductive ends of silk-based scaffold, HA was coated on the hybrid silk scaffold and the effects to the bone-related cells were evaluated. HA could be coated in a uniform and controlled manner on the silk sponge, using an alternate soaking technology, with the amount deposited being dependent on the number of soaking cycles. HA coating also progressively reduced the hydrophobicity of silk surface (decreasing water contact angle from 87° to 42-76°, after 1-3 soaking cycles), making the HA-coated silk scaffold less favorable for initial cell attachments; but the attached cells showed viability and sustained proliferation on the HA-coated scaffold. As demonstrated by real-time polymerase chain reaction and alkaline phosphatase assay, the osteoinductivity of HA-coated silk scaffolds resulted in the osteogenic differentiation of bone marrow mesenchymal stem cells, and the osteoconductivity of HA-coated silk scaffolds supported osteoblasts growth and maintained the properties of mature osteoblasts. These properties of HA-coating demonstrated its possible application in fabricating osteoinductive ends of the silk-based ligament graft to potentially enhance graft-to-host bone integration. PMID:22949167

He, Pengfei; Sahoo, Sambit; Ng, Kian Siang; Chen, Kelei; Toh, Siew Lok; Goh, James Cho Hong

2013-02-01

214

Compositionally graded hydroxyapatite/tricalcium phosphate coating on Ti by laser and induction plasma.  

PubMed

In this study we report the fabrication of compositionally graded hydroxyapatite (HA) coatings on Ti by combining laser engineering net shaping (LENS) and radio frequency induction plasma spraying processes. Initially, HA powder was embedded in the Ti substrates using LENS, forming a Ti-HA composite layer. Later, RF induction plasma spraying was used to deposit HA on these Ti substrates with a Ti-HA composite layer on top. Phase analysis by X-ray diffraction indicated phase transformation of HA to ?-tricalcium phosphate in the laser processed coating. Laser processed coatings showed the formation of a metallurgically sound and diffused substrate-coating interface, which significantly increased the coating hardness to 922 ± 183 Hv from that of the base metal hardness of 189 ± 22 Hv. In the laser processed multilayer coating a compositionally graded nature was successfully achieved, however, with severe cracking and a consequent decrease in the flexural strength of the coating. To obtain a structurally stable coating with a composition gradient across the coating thickness a phase pure HA layer was sprayed on top of the laser processed single layer coatings using induction plasma spray. The plasma sprayed HA coatings were strongly adherent to the LENS-TCP coatings, with adhesive bond strength of 21 MPa. In vitro biocompatibility of these coatings, using human fetal osteoblast cells, showed a clear improvement in cellular activity from uncoated Ti compared with LENS-TCP-coated Ti and reached a maximum in the plasma sprayed HA coating. PMID:20854939

Roy, Mangal; Balla, Vamsi Krishna; Bandyopadhyay, Amit; Bose, Susmita

2011-02-01

215

The role of phosphorylation in dentin phosphoprotein peptide absorption to hydroxyapatite surfaces: a molecular dynamics study.  

PubMed

Dentin phosphoprotein (DPP) is a protein expressed mainly in dentin and to a lesser extent in bone. DPP has a disordered structure, rich in glutamic acid, aspartic acid and phosphorylated serine/threonine residues. It has a high capacity for binding to calcium ions and to hydroxyapatite (HA) crystal surfaces. We used molecular dynamics (MD) simulations as a method for virtually screening interactions between DPP motifs and HA. The goal was to determine which motifs are absorbed to HA surfaces. For these simulations, we considered five peptides from the human DPP sequence. All-atom MD simulations were performed using GROMACS, the peptides were oriented parallel to the {100} HA crystal surface, the distance between the HA and the peptide was 3?nm. The system was simulated for 20?ns. Preliminary results show that for the unphosphorylated peptides, the acidic amino acids present an electrostatic attraction where their side chains are oriented towards HA. This attraction, however, is slow to facilitate bulk transport to the crystal surface. On the other hand, the phosphorylated (PP) peptides are rapidly absorbed on the surface of the HA with their centers of mass closer to the HA surface. More importantly, the root mean square fluctuation (RMSF) indicates that the average structures of the phosphorylated peptides are very inflexible and elongate, while that of the unphosphorylated peptides are flexible. Radius of gyration (Rg) analysis showed the compactness of un-phosphorylated peptides is lower than phosphorylated peptides. Phosphorylation of the DPP peptides is necessary for binding to HA surfaces. PMID:25158198

Villarreal-Ramirez, Eduardo; Garduño-Juarez, Ramón; Gericke, Arne; Boskey, Adele

2014-08-01

216

Peptide decorated nano-hydroxyapatite with enhanced bioactivity and osteogenic differentiation via polydopamine coating.  

PubMed

To be better used as implant materials in bone graft substitutes, bioactivity and osteogenesis of nano-hydroxyapatite (nano-HA) need to be further enhanced. Inspired by adhesive proteins in mussels, here we developed a novel bone forming peptide decorated nano-HA material. In this study, nano-HA was coated by one-step pH-induced polymerization of dopamine, and then the peptide was grafted onto polydopamine (pDA) coated nano-HA (HA-pDA) through catechol chemistry. Our results demonstrated that the peptide-conjugated nano-HA crystals could induce the adhesion and proliferation of MG-63 cells. Moreover, the highly alkaline phosphatase activity of the functionalized nano-HA indicated that the grafted peptide could maintain its biological activity after immobilization onto the surface of HA-pDA, especially at the concentration of 100?g/mL. These modified nano-HA crystals with better bioactivity and osteogenic differentiation hold great potential to be applied as bioactive materials in bone repairing, bone regeneration and bio-implant coating applications. PMID:23792546

Sun, Yuhua; Deng, Yi; Ye, Ziyou; Liang, Shanshan; Tang, Zhihui; Wei, Shicheng

2013-11-01

217

Sol-Gel-Derived Hydroxyapatite-Carbon Nanotube/Titania Coatings on Titanium Substrates  

PubMed Central

In this paper, hydroxyapatite-carbon nanotube/titania (HA-CNT/TiO2) double layer coatings were successfully developed on titanium (Ti) substrates intended for biomedical applications. A TiO2 coating was firstly developed by anodization to improve bonding between HA and Ti, and then the layer of HA and CNTs was coated on the surface by the sol-gel process to improve the biocompatibility and mechanical properties of Ti. The surfaces of double layer coatings were uniform and crack-free with a thickness of about 7 ?m. The bonding strength of the HA-CNT/TiO2 coating was higher than that of the pure HA and HA-CNT coatings. Additionally, in vitro cell experiments showed that CNTs promoted the adhesion of preosteoblasts on the HA-CNT/TiO2 double layer coatings. These unique surfaces combined with the osteoconductive properties of HA exhibited the excellent mechanical properties of CNTs. Therefore, the developed HA-CNT/TiO2 coatings on Ti substrates might be a promising material for bone replacement. PMID:22606041

Ji, Xiaoli; Lou, Weiwei; Wang, Qi; Ma, Jianfeng; Xu, Haihong; Bai, Qing; Liu, Chuantong; Liu, Jinsong

2012-01-01

218

Influence of Magnesium Ion Substitution on Structural and Thermal Behavior of Nanodimensional Hydroxyapatite  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA), incorporating small amount of magnesium, shows attractive biological performance in terms of improved bone metabolism, osteoblast and osteoclast activity, and bone in-growth. This article reports a systematic investigation on the influence of magnesium (Mg) substitution on structural and thermal behavior of nanodimensional HA. HA and Mg-substituted HA nanopowders were synthesized through sol-gel route. The morphology and size of nanopowders were characterized by transmission electron microscopy. The BET surface area was evaluated from N2 adsorption isotherms. Structural analysis and thermal behavior were investigated by means of Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetry, and differential thermal analysis. As-synthesized powders consisted of flake-like agglomerates of HA and calcium-deficient HA. The incorporation of magnesium in HA resulted in decrease of crystallite size, crystallinity, and lattice parameters a and c and increase in BET surface area. ?-tricalcium phosphate formation occured at lower calcination temperature in Mg-substituted HA than HA.

Batra, Uma; Kapoor, Seema; Sharma, Sonia

2013-06-01

219

Chondroitin sulfate template-mediated biomimetic synthesis of nano-flake hydroxyapatite  

NASA Astrophysics Data System (ADS)

By Ca(NO 3) 2·4H 2O and (NH 4) 3PO 4·3H 2O as reagents and chondroitin sulfate (ChS) as a template, nano-flake hydroxyapatite (HA) is synthesized using a biomimetic method according to the biomineralization theory. HA crystals obtained are characterized in crystalline phase, microstructure, chemical composition and morphology by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), transmission electron microscopy (TEM) and elemental analysis respectively. UV-vis spectrum is adopted to investigate interactions between functional groups ChS and HA. The results show that HA crystal nucleation and growth take place in chemical interactions between HA crystals and ChS as a template. And elemental analysis indicates that obtained HA contains a small amount of ChS. Furthermore, ChS concentration significantly affects the morphology of HA crystals. Staple-fiber-like HA crystals can be obtained at a low concentration in ChS, and flake-like HA crystals synthesized at a high concentration (?0.5 wt.%) of ChS as a template.

He, Dan; Xiao, Xiufeng; Liu, Fang; Liu, Rongfang

2008-11-01

220

Antibacterial and osteogenic properties of silver-containing hydroxyapatite coatings produced using a sol gel process.  

PubMed

Since bacterial infection is a rising complication following the wide use of implant, there is considerable attention on the effect of implant surface properties on bacterial adhesion. In this study, the effect of silver (Ag) doped hydroxyapatite (HA) coatings on initial antibacterial adhesion and osteoblast cell proliferation and differentiation was investigated. Using a sol-gel process, HA coatings doped with 1 wt % AgNO(3) (AgHA1.0) and 1.5 wt % Ag (AgHA1.5) were prepared. Coated surfaces were characterized using X-ray diffraction (XRD) and contact angles measurements. The initial bacteria adhesion was evaluated using a RP12 strain of Staphylococcus epidermidis (ATCC 35984) and the Cowan I strain of Staphylococcus aureus, whereas osteoblast proliferation and differentiation were evaluated using human embryonic palatal mesenchyme cells (HEPM), an osteoblast precursor cell line. In this study, XRD analysis of all surfaces indicated peaks corresponding to HA. Contact angles for AgHA surfaces were observed to be significantly lower when compared to HA surfaces. In vitro initial bacterial adhesion study indicated a significantly reduced number of S. epidermidis and S. aureus on AgHA surfaces when compared to HA surface. The use of HEPM cells indicated no significant difference in double-stranded DNA (dsDNA) production between all surfaces. Additionally, no differences in alkaline phosphatase specific activity were observed between HA and AgHA1.0 surfaces. Overall, it was concluded that AgHA1.0 has the similar biological activity as HA, with respect to bone cell proliferation and differentiation. In addition, the AgHA1.0 was also concluded to have the ability to minimize the initial bacteria adhesion. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007. PMID:17335020

Chen, W; Oh, S; Ong, A P; Oh, N; Liu, Y; Courtney, H S; Appleford, M; Ong, J L

2007-09-15

221

Adsorption of chlorhexidine on synthetic hydroxyapatite and in vitro biological activity.  

PubMed

The kinetic of chlorhexidine digluconate (CHXDG) uptake from aqueous solution by hydroxyapatite (HA) was investigated by ultraviolet (UV) analysis performed in HA powder (UV-solid) after the CHX adsorption. Adsorption isotherm of chlorhexidine (CHX) uptake was modeled by a combination of Languimir and Langmuir-Freundlich mechanisms. Strong molecule-molecule interactions and positive cooperativity predominated in the surface when CHX concentration was above 8.6 ?g(CHX)/mg(HA). UV-solid spectra (shape, intensity and band position) of CHX bound to HA revealed that long-range molecular structures, such as aggregates or micelles, started to be formed at low CHX concentrations (1.52 ?g(CHX)/mg(HA)) and predominated at high concentrations. Grazing-incidence X-ray diffraction (GIXRD) analysis from synchrotron radiation discarded the formation of crystalline structures on HA surface or precipitation of CHX crystalline salts, as suggested in previous works. The effect of the HA/CHX association on HA in vitro bioactivity, cytotoxicity and CHX antimicrobial activity was evaluated. It was shown that CHX did not inhibit the precipitation of a poorly crystalline apatite at HA/CHX surface after soaking in simulating body fluid (SBF). Cell viability studies after exposure to extracts of HA and HA/CHX showed that both biomaterials did not present significant in vitro toxicity. Moreover, HA/CHX inhibited Enterococcus faecalis growth for up to 6 days, revealing that binding to HA did not affect antimicrobial activity of CHX and reduced bacterial adhesion. These results suggested that HA/CHX association could result in a potential adjuvant antimicrobial system for clinical use. PMID:21676601

de Souza, Carlos A Soriano; Colombo, Ana Paula V; Souto, Renata M; Silva-Boghossian, Carina M; Granjeiro, Jose M; Alves, Gutemberg G; Rossi, Alexandre M; Rocha-Leão, Maria Helena M

2011-10-15

222

Sorption behavior of Zn(II) ions on synthesized hydroxyapatites  

Microsoft Academic Search

Calcium hydroxyapatite (CaHAP) and barium hydroxyapatite (BaHAP) have been prepared by a wet method from aqueous solutions with cation\\/P molar ratio of 1.67. The prepared particles were characterized using XRD, IR, TG–DTA and BET-N2 adsorption measurements. The potential of the synthesized hydroxyapatites to remove Zn(II) from aqueous solutions was investigated in batch reactor under different experimental conditions. Both hydroxyapatites remove

R. R. Sheha

2007-01-01

223

Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent  

PubMed Central

Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ?-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas. PMID:22399838

Wang, Tongxin; Chow, Laurence C.; Frukhtbeyn, Stanislav A.; Ting, Andy Hai; Dong, Quanxiao; Yang, Mingshu; Mitchell, James W.

2012-01-01

224

Hydroxyapatite-Coated Sillicone Rubber Enhanced Cell Adhesion and It May Be through the Interaction of EF1? and ?-Actin  

PubMed Central

Silicone rubber (SR) is a common soft tissue filler material used in plastic surgery. However, it presents a poor surface for cellular adhesion and suffers from poor biocompatibility. In contrast, hydroxyapatite (HA), a prominent component of animal bone and teeth, can promote improved cell compatibility, but HA is an unsuitable filler material because of the brittleness in mechanism. In this study, using a simple and economical method, two sizes of HA was applied to coat on SR to counteract the poor biocompatibility of SR. Surface and mechanical properties of SR and HA/SRs confirmed that coating with HA changes the surface topology and material properties. Analysis of cell proliferation and adhesion as well as measurement of the expression levels of adhesion related molecules indicated that HA-coated SR significantly increased cell compatibility. Furthermore, mass spectrometry proved that the biocompatibility improvement may be related to elongation factor 1-beta (EF1?)/?-actin adjusted cytoskeletal rearrangement. PMID:25386892

Zhang, Yi-ming; Wang, Yi-cheng; Yang, Zhi; Zhou, Xin; Lei, Ze-yuan; Fan, Dong-li

2014-01-01

225

Fretting wear behaviour of hydroxyapatite-titanium composites in simulated body fluid, supplemented with 5 g l-1 bovine serum albumin  

NASA Astrophysics Data System (ADS)

Damaged articulating joints can be repaired or replaced with synthetic biomaterials, which can release wear debris due to articulation, leading to the osteolysis. In a recent work, it has been shown that it is possible to achieve a better combination of flexural strength/fracture toughness as well as in vitro bioactivity and cytocompatibility properties in spark plasma sintered hydroxyapatite-titanium (HA-Ti) composites. Although hydroxyapatite and titanium are well documented for their good biocompatibility, nanosized hydroxyapatite (HA) and titanium (Ti) particles can cause severe toxicity to cells. In order to address this issue, fretting wear study of HA-Ti composites under dry and wet (1× SBF, supplemented with 5 g l-1 bovine serum albumin (BSA)) condition was performed to assess the wear resistance as well as wear debris formation, in vitro. The experimental results reveal one order of magnitude lower wear rate for HA-10 wt% Ti (7.5 × 10-5 mm3 N-1 m-1) composite than monolithic HA (3.9 × 10-4 mm3 N-1 m-1) in simulated body fluid. The difference in the tribological properties has been analyzed in the light of phase assemblages and mechanical properties. Overall, the results suggest the potential use of HA-Ti composites over existing HA-based biocomposites in orthopedic as well as dental applications.

Kumar, Alok; Biswas, Krishanu; Basu, Bikramjit

2013-10-01

226

A Rheological Study of Biodegradable Injectable PEGMC/HA Composite Scaffolds  

PubMed Central

Injectable biodegradable hydrogels, which can be delivered in a minimally invasive manner and formed in situ, have found a number of applications in pharmaceutical and biomedical applications, such as drug delivery and tissue engineering. We have recently developed an in situ crosslinkable citric acid-based biodegradable poly (ethylene glycol) maleate citrate (PEGMC)/hydroxyapatite (HA) composite, which shows promise for use in bone tissue engineering. In this study, the mechanical properties of the PEGMC/HA composites were studied in dynamic linear rheology experiments. Critical parameters such as monomer ratio, crosslinker, initiator, and HA concentrations were varied to reveal their effect on the extent of crosslinking as they control the mechanical properties of the resultant gels. The rheological studies, for the first time, allowed us investigating the physical interactions between HA and citric acid-based PEGMC. Understanding the viscoelastic properties of the injectable gel composites is crucial in formulating suitable injectable PEGMC/HA scaffolds for bone tissue engineering, and should also promote the other biomedical applications based on citric acid-based biodegradable polymers. PMID:25309615

Jiao, Yang; Gyawali, Dipendra; Stark, Joseph M.; Akcora, Pinar; Nair, Parvathi; Tran, Richard T.; Yang, Jian

2014-01-01

227

Microspheres in Plasma Display Panels  

NASA Technical Reports Server (NTRS)

Filling small bubbles of molten glass with gases is just as difficult as it sounds, but the technical staff at NASA is not known to shy away from a difficult task. When Microsphere Systems, Inc. (MSI), of Ypsilanti, Michigan, and Imaging Systems Technology, Inc. (IST), of Toledo, Ohio, were trying to push the limits of plasma displays but were having difficulty with the designs, NASA s Glenn Garrett Morgan Commercialization Initiative (GMCI) assembled key personnel at Glenn Research Center and Ohio State University for a brainstorming session to come up with a solution for the companies. They needed a system that could produce hollow, glass micro-sized spheres (microspheres) that could be filled with a variety of gasses. But the extremely high temperature required to force the micro-sized glass bubbles to form at the tip of a metal nozzle resulted in severe discoloration of the microspheres. After countless experiments on various glass-metal combinations, they had turned to the GMCI for help. NASA experts in advanced metals, ceramics, and glass concluded that a new design approach was necessary. The team determined that what was needed was a phosphate glass composition that would remain transparent, and they went to work on a solution. Six weeks later, using the design tips from the NASA team, Tim Henderson, president of MSI, had designed a new system in which all surfaces in contact with the molten glass would be ceramic instead of metal. Meanwhile, IST was able to complete a Phase I Small Business Innovation Research (SBIR) grant supported by the National Science Foundation (NSF) and supply a potential customer with samples of the microspheres for evaluation as filler materials for high-performance insulations.

2006-01-01

228

Flow cytometry analysis of human fetal osteoblast fate processes on spark plasma sintered hydroxyapatite-titanium biocomposites.  

PubMed

Hydroxyapatite (HA)-based biocomposites have been widely investigated for a multitude of applications and these studies have been largely driven to improve mechanical properties (toughness and strength) without compromising cytocompatibility properties. Apart from routine cell viability/proliferation analysis, limited efforts have been made to quantify the fate processes (cell proliferation, cell cycle, and cell apoptosis) of human fetal osteoblast (hFOB) cells on HA-based composites, in vitro. In this work, the osteoblast cell fate process has been studied on a model hydroxyapatite-titanium (HA-Ti) system using the flow cytometry. In order to retain both HA and Ti, the novel processing technique, that is, spark plasma sintering, was suitably adopted. The cell fate processes of hFOBs, as evaluated using a flow cytometry, revealed statistically insignificant differences among HA-10 wt % Ti and HA and control (tissue culture polystyrene surface) in terms of osteoblast apoptosis, proliferation index as well as division index. For the first time, we provide quantified flow cytometry results to demonstrate that 10 wt % Ti additions to HA do not have any significant influence on the fate processes of human osteoblast-like cells, in vitro. PMID:23529941

Kumar, Alok; Webster, Thomas J; Biswas, Krishanu; Basu, Bikramjit

2013-10-01

229

Confocal Raman and electronic microscopy studies on the topotactic conversion of calcium carbonate from Pomacea lineate shells into hydroxyapatite bioceramic materials in phosphate media.  

PubMed

Conversion of Pomacea lineate shells into hydroxyapatite (HA) bioceramic materials was investigated by their in vitro treatment with phosphate solutions, at room temperature. Confocal Raman microscopy revealed that the conversion proceeds at distinct rates through the nacreous or periostracum sides of the shell. The conversion can be accelerated using powdered samples, yielding biocompatible materials of great interest in biomedicine. PMID:20678941

dePaula, S M; Huila, M F G; Araki, K; Toma, H E

2010-12-01

230

Enhanced MSC Chondrogenesis Following Delivery of TGF-?3 from Alginate Microspheres within Hyaluronic Acid Hydrogels In Vitro and In Vivo  

PubMed Central

Mesenchymal stem cells (MSCs) are being recognized as a viable cell source for cartilage repair and members of the transforming growth factor-beta (TGF-?) superfamily are a key mediator of MSC chondrogenesis. While TGF-? mediated MSC chondrogenesis is well established in in vitro pellet or hydrogel cultures, clinical translation will require effective delivery of TGF-?s in vivo. Here, we investigated the co-encapsulation of TGF-?3 containing alginate microspheres with human MSCs in hyaluronic acid (HA) hydrogels towards the development of implantable constructs for cartilage repair. TGF-?3 encapsulated in alginate microspheres with nanofilm coatings showed significantly reduced initial burst release compared to uncoated microspheres, with release times extending up to 6 days. HA hydrogel constructs seeded with MSCs and TGF-?3 containing microspheres developed comparable mechanical properties and cartilage matrix content compared to constructs supplemented with TGF-?3 continuously in culture media, whereas constructs with TGF-?3 directly encapsulated in the gels without microspheres had inferior properties. When implanted subcutaneously in nude mice, constructs containing TGF-?3 microspheres resulted in superior cartilage matrix formation to groups without TGF-?3 or with TGF-?3 added directly to the gel. However, calcification was observed in implanted constructs after 8 weeks of subcutaneous implantation. To prevent this, the co-delivery of parathyroid hormone-related protein (PTHrP) with TGF-?3 in alginate microspheres was pursued, resulting in partially reduced calcification. This study demonstrates that the controlled local delivery of TGF-?3 is essential to neocartilage formation by MSCs and that further optimization is needed to avert the differentiation of chondrogenically induced MSCs towards a hypertrophic phenotype. PMID:21652067

Bian, Liming; Zhai, David Y.; Tous, Elena; Rai, Reena; Mauck, Robert L.; Burdick, Jason A.

2011-01-01

231

Bioactive nanocrystalline sol-gel hydroxyapatite coatings.  

PubMed

Sol-gel technology offers an alternative technique for producing bioactive surfaces for improved bone attachment. Previous work indicated that monophasic hydroxyapatite coatings were difficult to produce. In the present work hydroxyapatite was synthesized using the sol-gel technique with alkoxide precursors and the solution was allowed to age up to seven days prior to coating. It was found that, similar to the wet-chemical method of hydroxyapatite powder synthesis, an aging time is required to produce a pure hydroxyapatite phase. A methodology that has been successfully used to produce nanocrystalline hydroxyapatite thin film coatings via the sol-gel route on various substrates including alumina, Vycor glass, partially stabilized zirconia, Ti-6Al-4V alloy and single crystal MgO is described. Coatings produced on MgO substrates were characterized by X-ray diffraction and atomic force microscopy, while the analogous gels were examined with thermogravimetric and differential thermal analyses. The coatings were crack free and the surface was covered with small grains, of approximately 200 nm in size for samples fired to 1000 degrees C. Coating thickness varied between 70 and 1000 nm depending on the number of applied layers. PMID:15348113

Chai, C S; Ben-Nissan, B

1999-08-01

232

Encapsulation of antihypertensive drugs in cellulose-based matrix microspheres: characterization and release kinetics of microspheres and tableted microspheres.  

PubMed

This study is an attempt to prepare microspheres loaded with two antihypertensive drugs viz., nifedipine (NFD) and verapamil hydrochloride (VRP) using cellulose-based polymers viz., ethyl cellulose (EC) and cellulose acetate (CA). Emulsification and solvent evaporation methods were optimized using ethyl acetate as a dispersing solvent. The particles are spherical in shape and have smooth surfaces, as evidenced by the scanning electron microscopy. The microspheres were characterized for their particle size and distribution, tapped density and encapsulation efficiency. Smaller sized particles with a narrow size distribution were produced with EC when compared to CA matrices. Molecular level drug distribution in the microspheres was confirmed by differential scanning calorimetry. The microspheres were directly compressed into tablets using different excipients. The drug release from CA was faster than EC microspheres and, also, the VRP release was faster than NFD. The excipients used in tableting showed an effect on the release as well as the physical properties of the tablets. PMID:11308229

Soppimath, K S; Kulkarni, A R; Aminabhavi, T M

2001-01-01

233

Effect of steam treatment during plasma spraying on the microstructure of hydroxyapatite splats and coatings  

NASA Astrophysics Data System (ADS)

The major problems with plasma sprayed hydroxyapatite (HA) coatings for hard tissue replacement are severe HA decomposition and insufficient mechanical properties of the coatings. Loss of crystalline HA after the high-temperature spraying is due mainly to the loss of OH- in terms of water. The current study used steam to treat HA droplets and coatings during both in-flight and flattening stages during plasma spraying. The microstructure of the HA coatings and splats was characterized using scanning electron microscope, Raman spectroscopy, Fourier transform IR spectroscopy, and x-ray diffraction. Results showed that a significant increase in crystallinity of the HA coating was achieved through the steam treatment (e.g., from 58 to 79%). In addition, the effects were dependent on particle sizes of the HA feedstock, more increase in crystallinity of the coatings made from smaller powders was revealed. The Raman spectroscopy analyses on the individual splats and coatings indicate that the mechanism involves entrapping of water molecules by the individual HA droplets upon their impingement. It further suggests that the HA decomposition has already taken place before the impingement of the droplets on precoating or substrate. The improvement in crystallinity and phases, for example, from tricalcium phosphate and amorphous calcium phosphate to HA, was achieved by reversing the HA decomposition through providing extra OH-. Furthermore, the steam treatment during the spraying also accounts for remarkably increased adhesion strength from 9.09 to 23.13 MPa. The in vitro testing through immersing the HA coatings in simulated body fluid gives further evidence that the economic and simple steam treatment is promising in improving HA coating structure.

Li, H.; Khor, K. A.; Cheang, P.

2006-12-01

234

Biocompatibility of defect-related luminescent nanostructured and microstructured hydroxyapatite.  

PubMed

Three defect-related luminescent hydroxyapatite (HAP) particles, S1, S2, and S3, with different morphologies (the samples S1 and S2 are nanorods with diameters of 25 nm and lengths of 30 and 100 nm, respectively; sample S3 is bur-like microspheres with diameters of 5-6 ?m) were synthesized, and their biocompatibility was investigated by MTT, reactive oxygen species (ROS), interleukin-6 (IL-6), comet, and hemolysis assays. The results indicated that all samples were stable in cell culture medium and did not induce the synthesis of proinflammatory cytokine IL-6 or result in hemolysis. It was found that samples S1 and S3 inhibited osteoblast (OB) viability at concentrations of 5, 10, 20, 40, and 80 ?g/mL for 24, 48, and 72 h. Sample S2 had no effect on the viability of OB at all tested concentrations for 24 and 48 h, but the viability of OB was increased at concentrations of 20, 40, and 80 ?g/mL for 72 h. Samples S1 and S3 could increase the level of cellular ROS; sample S2 had no effect on the level of cellular ROS at a concentration of 20 ?g/mL for 48 h. Although samples S1 and S3 induced significant DNA damage, sample S2 could not cause significant DNA damage at a concentration of 20 ?g/mL for 72 h. The results suggest that longer nanorod HAP can show excellent biocompatibility and therefore may find potential applications in biomedical fields. PMID:25312382

Dai, Chunyan; Duan, Jianlei; Zhang, Liang; Jia, Guang; Zhang, Cuimiao; Zhang, Jinchao

2014-12-01

235

Microsphere estimates of blood flow: Methodological considerations  

SciTech Connect

The microsphere technique is a standard method for measuring blood flow in experimental animals. Sporadic reports have appeared outlining the limitations of this method. In this study the authors have systematically assessed the effect of blood withdrawals for reference sampling, microsphere numbers, and anesthesia on blood flow estimates using radioactive microspheres in dogs. Experiments were performed on 18 conscious and 12 anesthetized dogs. Four blood flow estimates were performed over 120 min using 1 {times} 10{sup 6} microspheres each time. The effects of excessive numbers of microspheres pentobarbital sodium anesthesia, and replacement of volume loss for reference samples with dextran 70 were assessed. In both conscious and anesthetized dogs a progressive decrease in gastric mucosal blood flow and cardiac output was observed over 120 min. This was also observed in the pancreas in conscious dogs. The major factor responsible for these changes was the volume loss due to the reference sample withdrawals. Replacement of the withdrawn blood with dextran 70 led to stable blood flows to all organs. The injection of excessive numbers of microspheres did not modify hemodynamics to a greater extent than did the injection of 4 million microspheres. Anesthesia exerted no influence on blood flow other than raising coronary flow. The authors conclude that although blood flow to the gastric mucosa and the pancreas is sensitive to the minor hemodynamic changes associated with the microsphere technique, replacement of volume loss for reference samples ensures stable blood flow to all organs over a 120-min period.

von Ritter, C.; Hinder, R.A.; Womack, W.; Bauerfeind, P.; Fimmel, C.J.; Kvietys, P.R.; Granger, D.N.; Blum, A.L. (Univ. of the Witwatersrand, Johannesburg (South Africa) Louisianna State Univ. Medical Center, Shreveport (USA) Universitaire Vaudois (Switzerland))

1988-02-01

236

Gastro-resistant microspheres containing ketoprofen.  

PubMed

Ketoprofen gastroresistant microspheres were prepared by spray-drying using common pH dependent polymers, such as Eudragit S and L, CAP, CAT and HPMCP. The long ketoprofen recrystallization time was a serious hindrance to the preparation of microspheres having a drug content higher than 35%. Microspheres were characterized by scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry and in vitro dissolution studies, and used for the preparation of tablets. During this step, the compaction ability of the spray-dried powders was measured. While the compressibility of the microspheres containing the enteric cellulosic derivatives are not acceptable and different from those of the microcrystalline cellulose, the compaction properties of ketoprofen/Eudragit L or S microspheres are comparable to those of the Avicel PH 101. In vitro dissolution studies were performed on the microspheres and the tablets. All microspheres showed a good gastroresistance, but some differences among the five polymers in reducing drug release at low pH values are present. Acrylic polymers (Eudragit L or S) are considerably more effective than the cellulosic derivatives CAP and CAT, while the HPMCP profile is in an intermediate position. These differences are erased by the microspheres compression process. In HCl 0.1 N, the percentage of ketoprofen released from the tablets is always close to zero, independently from the polymer used. PMID:11811753

Palmieri, G F; Bonacucina, G; Di Martino, P; Martelli, S

2002-01-01

237

Effect of hydroxyapatite nanocrystals functionalized with lactoferrin in osteogenic differentiation of mesenchymal stem cells.  

PubMed

Lactoferrin (LF) is a bioactive glycoprotein that became recently interesting in the field of bone regeneration for its modulatory effect on bone cells. On the basis of this evidence this work aims to functionalize biomimetic hydroxyapatite (HA) nanocrystals with LF to study their effect on osteogenic differentiation of mesenchymal stem cells (MSCs). The orientation of LF on the HA surface was analyzed by spectroscopic and thermal techniques. Three samples with different amounts of LF attached to HA nanocrystals were tested in vitro. The combined effect of HA and LF on MSC proliferation and morphology, alkaline phosphatase (ALP) activity, and gene expression were evaluated at different time points. The sample with the lowest LF amount showed the best bioactivity probably due to the formation of a single layer of protein with a better molecular orientation. Coupling of HA-LF did not affect cell proliferation and morphology, while analysis of HA-LF on ALP activity and messenger RNA expression of the selected genes, demonstrated the role of HA-LF in the induction of osteogenic markers. HA-LF represents a promising system to be used to manufacture bioactive functional materials in tissue engineering (as scaffolds, injectable cements, or coatings for metallic implants) with enhanced anabolic activity to treat bone diseases. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 224-234, 2015. PMID:24639083

Montesi, Monica; Panseri, Silvia; Iafisco, Michele; Adamiano, Alessio; Tampieri, Anna

2015-01-01

238

Development of metal/hydroxyapatite composite surface coatings. Ph.D. Thesis  

SciTech Connect

Metal/ceramic composites containing calcium phosphates have shown considerable success in enhancing bone growth into implants, thereby providing cementless fixation. Calcium phosphate occurs in various phases. The extent of compatibility of the composites to the hosts depend upon the phase of the calcium phosphate. A crystalline phase known as hydroxyapatite (HA) which naturally occurs in bones and teeth of animals has proved to enhance bone growth. This work involved development of a composite that will retain both the biological properties of HA and the mechanical properties of the metal. In this method, HA was codeposited electrolytically on a metal substrate in a metal matrix to provide adequate adhesion to the substrate. Codeposited HA on the surface was characterized using FTIR and Raman spectroscopy to ensure that HA structure remained unaltered throughout the conditions employed during the process. The development of the composite was carried out in two phases. Phase 1 consisted of codeposition of HA in a single metal matrix, characterization of HA and testing the viability of the process to all substrate geometry. In the second phase, a process was developed to electrolytically deposit cobalt, chromium, molybdenum alloy (vitallium) and then codeposit HA in that alloy matrix on substrates. The plated alloy was characterized by x-ray photoelectron spectroscopy, x-ray diffraction, energy dispersive spectroscopy and compared with similar analyses for cast vitallium alloy. The deposited alloy was also tested for corrosion and substrate adhesion.

Dasarathy, H.

1992-01-01

239

Nanostructural characteristics, mechanical properties, and osteoblast response of spark plasma sintered hydroxyapatite.  

PubMed

This study aimed to fabricate bulk nanostructured hydroxyapatite (HA) pellets with improved properties using spark plasma sintering (SPS) for orthopedic applications. Spray-dried nanostructured HA (nSD-HA) powders were consolidated using the rapid SPS processing. The SPS processed nSD-HA was characterized using Raman spectroscopy and field emission scanning electron microscopy (FESEM). Mechanical properties of the consolidates were also evaluated through indentation approach. The nanostructures ( approximately 80 nm in grain size) of the starting powders were successfully retained after the SPS processing operated at 950 degrees C with <15 min holding time. The SPS consolidated nSD-HA showed promising mechanical properties, approximately 118 GPa for Young's modulus, and up to 2.22 MPa m(0.5) for fracture toughness. SPS holding time showed minor influence on the phases of the pellets. Furthermore, the spheroidized nanostructured HA retained the HA structure after the SPS consolidation. Preliminary cytotoxicity and cell attachment studies were also carried out using a human osteoblast cell line hFOB 1.19. Enhanced cell attachment and proliferation on the nanostructured pellets were revealed. The presence of the nanostructures accounts mainly for the enhanced mechanical properties and promoted proliferation of the osteoblast cells. This study suggests that the SPS technique is an appropriate process for fabrication of bulk nSD-HA from nanostructured powder. PMID:17274029

Li, H; Khor, K A; Chow, V; Cheang, P

2007-08-01

240

Effect of silver content on the antibacterial and bioactive properties of silver-substituted hydroxyapatite.  

PubMed

The long-term success of a biomaterial used during surgery may be compromised by infection. A possible effective solution is to make the biomaterial osteoconductive and antibacterial. A range of silver-substituted hydroxyapatite (AgHA) of up to 1.1 wt. % of Ag was synthesized. AgHA displayed a rod-like morphology of dimensions ~50 nm in length and ~15 nm in width. Phase-pure AgHA was demonstrated in the X-ray diffraction patterns and Fourier transform infrared spectroscopy spectra. Comparing with hydroxyaptite (HA), 0.5AgHA exhibited a 3-log reduction in the number of bacteria. Diffusion of the entrapped Ag(+) ions towards the crystal structure surface was revealed by an increase of 6 at. % Ag in the X-ray photoelectron spectroscopy results. Furthermore, less than 0.5 ppm of Ag(+) ions being released from 0.5AgHA into the deionized water medium was evidenced from the inductively coupled plasma mass spectrometry results. AgHA produced by co-precipitation gave rise to minimal release of Ag(+) ions. It was hypothesized that the diffused surface Ag(+) ions damaged the bacteria cell membrane and impede its replication. With the culturing time, significant increase in the number of human mesenchymal stem cells (p < 0.05) was demonstrated on 0.5AgHA. PMID:23349126

Lim, Poon Nian; Teo, Erin Yiling; Ho, Bow; Tay, Bee Yen; Thian, Eng San

2013-09-01

241

Hydroxyapatite crystallinity does not affect the repair of critical size bone defects  

PubMed Central

Objective The physicochemical properties of hydroxyapatite (HA) granules were observed to affect the biological behavior of graft materials. The aim of this work was to analyze the tissue response of two HA granules with different crystallinity and Ca/P ratio in vivo. Material and Methods The HA granules were produced in the Biomaterials Laboratory (COPPE/UFRJ). The testing materials were HA granules presenting a Ca/P molar ratio of 1.60 and 28% crystallinity (HA-1), and a Ca/P molar ratio of 1.67 and 70% crystallinity (HA-2). Both HAs were implanted into a critical-size calvaria rat defects. Results To note, in the control group, the bone defects were filled with blood clot only. Descriptive and histomorphometric analyses after 1, 3, and 6 months postoperatively showed mild inflammatory infiltrate, mainly comprising macrophage-like and multinucleated giant cells, and an increase in the volume density of the fibrous tissues (p<0.05), which was in contrast to the similar volume density of the newly formed bone and biomaterials in relation to the control group. Conclusion Thus, we concluded that HA-1 and HA-2 are biocompatible and non-degradable, and that crystallinity does not affect bone repair of critical size defects. PMID:21655775

CONZ, Marcio Baltazar; GRANJEIRO, Jose Mauro; SOARES, Gloria de Almeida

2011-01-01

242

Effects of ionic products from silicon-substituted hydroxyapatite on the rat brain activity: Morris water maze studies and long term potentiation in hippocampal CA1  

Microsoft Academic Search

This study sets to examine the effects of ionic products from silicon-substituted hydroxyapatite (Si-HA) on brain activity in Wistar rats. Animals were treated intraperitoneally with leaching liquor of Si-HA once a day for 2weeks. Morris water maze (MWM) test was employed to evaluate the spatial memory. The long term potentiation (LTP) of synaptic responses in the CA1 area was recorded.

Yi-Yi Wang; Ning Li; Jie Huang; Zhuo Yang; Tao Zhang

2011-01-01

243

Calcium modulates interactions between bacteria and hydroxyapatite.  

PubMed

Bacterial adhesion onto hydroxyapatite is known to depend on the surface properties of both the biomaterial and the bacterial strain, but less is known about the influence of the composition of the aqueous medium. Here, the adhesion of Streptococcus mutans and 3 different Lactobacilli on powdered hydroxyapatite was shown to change with Ca2+ concentration. The effect depends on the surface properties of each strain. Adhesion of Lactobacillus fermentum and salivarius (and of Streptococcus mutans at low Ca2+) was enhanced with increasing Ca2+ concentration. Lactobacillus casei was efficiently removed by adhesion on hydroxyapatite, even without Ca2+ addition, and the effect of this ion was only marginal. The results are interpreted in terms of Ca2+-mediated adhesion, and relative to the hydrophobic properties of each strain and the electrical properties of the bacterial and solid surfaces (electrophoretic mobility). PMID:17122166

Venegas, S C; Palacios, J M; Apella, M C; Morando, P J; Blesa, M A

2006-12-01

244

Integrated Cryogenic Experiment (ICE) microsphere investigation  

NASA Technical Reports Server (NTRS)

The main objective is to determine the performance of microsphere insulation in a 0-g environment and compare its performance to reference insulations such as multilayer insulation. The Lockheed Helium Extended-Life Dewar (HELD) is used to provide superfluid-helium cold sink for the experiment. The use of HELD allows the low-g dynamic properties of Passive Orbital Disconnect Struts (PODS) to be characterized and provides a flight demonstration of the PODS system. The thermal performance of microspheres in 1 and 0 g was predicted, a flight experiment was designed to determine microsphere thermal performance, and the interface was also designed between the experimental package and the shuttle through HELD and the Hitchhiker-M carrier. A single test cell was designed and fabricated. The cell was filled with uncoated glass microspheres and tested with a liquid-nitrogen cold sink. The data were found to agree with predictions of microsphere performance in 1 g.

Spradley, I.; Read, D.

1989-01-01

245

Polymer microspheres carrying fluorescent DNA probes  

NASA Astrophysics Data System (ADS)

A polymer microspheres carried DNA probe, which was based on resonance energy transfer, was presented in this paper when CdTe quantum dots(QDs) were as energy donors, Au nanoparticles were as energy accepters and poly(4- vinylpyrindine-co-ethylene glycol dimethacrylate) microspheres were as carriers. Polymer microspheres with functional group on surfaces were prepared by distillation-precipitation polymerization when ethylene glycol dimethacrylate was as crosslinker in acetonitrile. CdTe QDs were prepared when 3-mercaptopropionic acid(MPA) was as the stabilizer in aqueous solution. Because of the hydrogen-bonding between the carboxyl groups of MPA on QDs and the pyrindine groups on the microspheres, the QDs were self-assembled onto the surfaces of microspheres. Then, the other parts of DNA probe were finished according to the classic method. The DNA detection results indicated that this novel fluorescent DNA probe system could recognize the existence of complementary target DNA or not.

Chen, Xiaoyu; Dai, Zhao; Zhang, Jimei; Xu, Shichao; Wu, Chunrong; Zheng, Guo

2010-07-01

246

Preparation of floating microspheres for fish farming.  

PubMed

The aim of this study was to develop floating microspheres with practical applications to fish farming. Each microsphere with a central hollow cavity was prepared using a solvent diffusion and evaporation method with Eudragit E100. Various manufacturing parameters were investigated by single factor method. The macrolide antibiotic josamycin was selected as a model drug. The loading efficiency of the drug in the microspheres was 64.7%. In the release study, virtually none of the drug was released into the fresh water whereas the entire drug was released from the josamycin-loaded microspheres into the simulated gastric fluid of rainbow trout (pH 2.7). The buoyancy was excellent with approximately 90% of the microspheres still floating after 24h. PMID:17485183

Nepal, Pushp R; Chun, Myung-Kwan; Choi, Hoo-Kyun

2007-08-16

247

Thermal response of chalcogenide microsphere resonators  

SciTech Connect

A chalcogenide microsphere resonator (CMR) used for temperature sensing is proposed and demonstrated. The CMR is fabricated using a simple technique of heating chalcogenide glass and allowing the molten glass to form a microsphere on the waist of a tapered silica fibre. The thermal responses of the CMR is investigated and compared to that of a single-mode-fibre (SMF) based microsphere resonator. It is observed that the CMR sensitivity to ambient temperature changes is 8 times higher than that of the SMF-based microsphere resonator. Heating the chalcogenide microsphere with a laser beam periodically turned on and off shows periodic shifts in the transmission spectrum of the resonator. By injecting an intensity-modulated cw signal through the resonator a thermal relaxation time of 55 ms is estimated.

Ahmad, H; Aryanfar, I; Lim, K S; Chong, W Y; Harun, S W

2012-05-31

248

Thermoplastic polyurethane/hydroxyapatite electrospun scaffolds for bone tissue engineering: Effects of polymer properties and particle size.  

PubMed

Thermoplastic polyurethane (TPU)/hydroxyapatite (HA) scaffolds were fabricated via electrospinning. The effects of TPU properties and HA particle size on scaffold physical properties and osteoblast-like cell performance were investigated. It was found that the addition of micro-HA (mHA), which was inlayed in the fiber, decreased the electrospun fiber diameter. On the contrary, nano-HA (nHA), which was either embedded or existed inside of the fiber, increased the fiber diameter for both soft and hard TPUs. The soft TPU had a much lower Young's modulus and higher strain-at-break than the hard TPU. The addition of both mHA and nHA decreased the tensile properties; this decrease was more significant with mHA. The cells on the hard scaffolds actively proliferated and migrated compared to those on the soft scaffolds. On the other hand, cells on the soft scaffolds more effectively induced osteogenesis of human mesenchymal stem cells (hMSCs) than those on the hard scaffolds. In addition, our data suggest that the soft scaffolds with supplementation of nHA further enhanced osteogenesis of hMSCs compared to those without nHA. The soft TPU scaffolds containing nano-HA have the potential to be used in bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1434-1444, 2014. PMID:24574168

Mi, Hao-Yang; Palumbo, SunMi; Jing, Xin; Turng, Lih-Sheng; Li, Wan-Ju; Peng, Xiang-Fang

2014-10-01

249

PLGA/nHA hybrid nanofiber scaffold as a nanocargo carrier of insulin for accelerating bone tissue regeneration  

PubMed Central

The development of tissue engineering in the field of orthopedic surgery is booming. Two fields of research in particular have emerged: approaches for tailoring the surface properties of implantable materials with osteoinductive factors as well as evaluation of the response of osteogenic cells to these fabricated implanted materials (hybrid material). In the present study, we chemically grafted insulin onto the surface of hydroxyapatite nanorods (nHA). The insulin-grafted nHAs (nHA-I) were dispersed into poly(lactide-co-glycolide) (PLGA) polymer solution, which was electrospun to prepare PLGA/nHA-I composite nanofiber scaffolds. The morphology of the electrospun nanofiber scaffolds was assessed by field emission scanning electron microscopy (FESEM). After extensive characterization of the PLGA/nHA-I and PLGA/nHA composite nanofiber scaffolds by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM), the PLGA/nHA-I and PLGA/nHA (used as control) composite nanofiber scaffolds were subjected to cell studies. The results obtained from cell adhesion, alizarin red staining, and Von Kossa assay suggested that the PLGA/nHA-I composite nanofiber scaffold has enhanced osteoblastic cell growth, as more cells were proliferated and differentiated. The fact that insulin enhanced osteoblastic cell proliferation will open new possibilities for the development of artificial scaffolds for bone tissue regeneration. PMID:25024679

2014-01-01

250

Preparation and characterization of NiW-nHA composite catalyst for hydrocracking  

NASA Astrophysics Data System (ADS)

The synthesis, characterization and catalytic capability of the NiW-nano-hydroxyapatite (NiW-nHA) composite were investigated in this paper. The NiW-nHA catalyst was prepared by a co-precipitation method. Then Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX) were used to analyze this material. In addition, the catalytic capacity of the NiW-nHA composite was also examined by FT-IR and gas chromatography (GC). The results of FT-IR analysis indicated that Ni, W and nHA combined closely. TEM observation revealed that this catalyst was needle shaped and the crystal retained a nanometer size. XRD data also suggested that a new phase of CaWO4 appeared and the lattice parameters of nHA changed in this system. nHA was the carrier of metals. The rates of Ni/W-loading were 73.24% and 65.99% according to the EDX data, respectively. Furthermore, the conversion of 91.88% Jatropha oil was achieved at 360 °C and 3 MPa h-1 over NiW-nHA catalyst. The straight chain alkanes ranging from C15 to C18 were the main components in the production. The yield of C15-C18 alkanes was up to 83.56 wt%. The reaction pathway involved hydrocracking of the C&z.dbd;C bonds of these triglycerides from Jatropha oil. This paper developed a novel non-sulfided catalyst to obtain a ``green biofuel'' from vegetable oil.

Zhou, Gang; Hou, Yongzhao; Liu, Lei; Liu, Hongru; Liu, Can; Liu, Jing; Qiao, Huiting; Liu, Wenyong; Fan, Yubo; Shen, Shituan; Rong, Long

2012-11-01

251

Characterization of hydroxyapatite\\/nano-zirconia composite coatings deposited by high velocity oxy-fuel (HVOF) spray process  

Microsoft Academic Search

Hydroxyapatite (HA)\\/nano-zirconia composite coatings were successfully produced through high velocity oxy-fuel (HVOF) spraying of radio frequency (RF) plasma synthesized powders. Microstructure characterization and morphology analysis on the nano-structured coatings were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and differential scanning calorimetry (DSC). Elastic modulus of the coatings was determined using nano-indentation on polished cross-sections,

H Li; K. A Khor; R Kumar; P Cheang

2004-01-01

252

In vitro Study on Apical Sealing Ability of Nano-Hydroxyapatite-Filled Epoxy Resin Based Endodontic Sealer  

Microsoft Academic Search

The objectives of this in vitro study were to evaluate the apical sealing ability of experimental nano hydroxyapatite (HA)-filled epoxy resin based endodontic sealer and to compare it with the commercial AH26 sealant. A total of 76 extracted human anterior teeth were instrumented using NiTi files and randomly divided into two groups of 33 teeth each and two control groups

S. M. Masudi; N. Luddin; D. Mohamad; J. J. Alkashakhshir; R. Adnan; R. A. Ramli

2010-01-01

253

Induction Plasma Sprayed Nano Hydroxyapatite Coatings on Titanium for Orthopaedic and Dental Implants  

PubMed Central

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared spectroscopic (FTIR) analysis show that the normal plasma nozzle lead to increased phase decomposition, high amorphous calcium phosphate (ACP) phase formation, and severe dehydroxylation of HA. In contrast, coatings prepared using supersonic nozzle retained the crystallinity and phase purity of HA due to relatively short exposure time of HA particles in the plasma. In addition, these coatings exhibited a microstructure that varied from porous and glassy structure at the coating-substrate interface to dense HA at the top surface. The microstructural analysis showed that the coating was made of multigrain HA particles of ~200 nm in size, which consisted of recrystallized HA grains in the size range of 15– 20 nm. Apart from the type of nozzle, working distance was also found to have a strong influence on the HA phase decomposition, while plate power had little influence. Depending on the plasma processing conditions, a coating thickness between 300 and 400 ?m was achieved where the adhesive bond strengths were found to be between 4.8 MPa to 24 MPa. The cytotoxicity of HA coatings was examined by culturing human fetal osteoblast cells (hFOB) on coated surfaces. In vivo studies, using the cortical defect model in rat femur, evaluated the histological response of the HA coatings prepared with supersonic nozzle. After 2 weeks of implantation, osteoid formation was evident on the HA coated implant surface, which could indicate early implant- tissue integration in vivo. PMID:21552358

Roy, Mangal; Bandyopadhyay, Amit; Bose, Susmita

2011-01-01

254

Morphology and immersion behavior of plasma-sprayed hydroxyapatite/bioactive glass coatings.  

PubMed

A series of hydroxyapatite/bioactive glass (HA/BG) coatings have been plasma-sprayed on Ti6Al-4V substrate using HA/BG powders that were prepared by both sinter-granulation and direct mixing methods. The morphology and immersion behavior of these coatings in a simulated body fluid (SBF) were investigated. The results showed that in-house fabricated BG and sinter-granulated HA powders were irregularly shaped and dense. When 5 wt % or more BG was added in HA, the powder became rough and porous. X-ray diffraction (XRD) patterns showed that the presence of BG enhanced the decomposition of HA structure during fabrication of the powders. Reasonably high bond strengths were obtained from all coatings. The granulated type HA/BG coatings showed no significant differences in bond strength from the mixed type HA/BG coatings. The plasma spray process itself and the presence of BG enhanced the decomposition of apatite. Surface morphology of all sinter-granulated type coatings was similar to that of monolithic HA coating, that was comprised of patches of smooth and shiny glassy film and irregularly-shaped particles on its surface. The dissolution depth of plasma-sprayed coatings immersed in SBF was largely dependent on the type and composition of the coating. Granulated type HA/BG coatings were much less dissolvable than monolithic HA or mixed type HA/BG coatings. It seems that the presently used granulation method for the preparation of HA/BG powders plays a predominant role in determining the dissolution behavior of the plasma-sprayed coatings. PMID:15348047

Ding, S J; Ju, C P; Lin, J H

2000-03-01

255

Ya Ha, an associate professor of phar-  

E-print Network

unusual reaction is yet unclear. Many researchers... See Ha's Talk on p.2 Think of eye makeup in ancient. These fascinating items from the world's cultural heritage have one thing in com- mon: all are subjects

Johnson, Peter D.

256

Biofilm formation on nanostructured hydroxyapatite-coated titanium.  

PubMed

Biofilm formation on medical devices is a common cause of implant failure, especially regarding implants that breach the epithelial tissue, so-called transcutaneous implants. Nanotechnology and the development of new nanomaterials have given the opportunity to design nanotextured implant surfaces. Such surfaces have been studied using various in vitro methods showing that nanosized features strongly benefit bone cell growth. However, little is known on how nanostructured features affect biofilm formation. The aim of this study was therefore to examine the shape- and chemical-dependent effect of a nanostructured hydroxyapatite (HA) coating on the degree of Staphylococcus epidermidis biofilm formation. Three different types of nanosized HA particles having different shapes and calcium to phosphate ratios were compared to uncoated turned titanium using safranin stain in a biofilm assay and confocal laser scanning microscopy (CLSM) for assessment of biofilm biomass and bacterial volume, respectively. No difference in biofilm biomass was detected for the various surfaces after 6 h incubation with S. epidermidis. Additionally, image analysis of CLSM Z-stacks confirmed the biofilm assay and showed similar results. In conclusion, the difference in nanomorphology and chemical composition of the surface coatings did not influence the adhesion and biofilm formation of S. epidermidis. PMID:23589449

Westas, Emma; Gillstedt, Martin; Lönn-Stensrud, Jessica; Bruzell, Ellen; Andersson, Martin

2014-04-01

257

Mineralization Potential of Electrospun PDO-Hydroxyapatite-Fibrinogen Blended Scaffolds  

PubMed Central

The current bone autograft procedure for cleft palate repair presents several disadvantages such as limited availability, additional invasive surgery, and donor site morbidity. The present preliminary study evaluates the mineralization potential of electrospun polydioxanone:nano-hydroxyapatite?:?fibrinogen (PDO?:?nHA?:?Fg) blended scaffolds in different simulated body fluids (SBF). Scaffolds were fabricated by blending PDO?:?nHA?:?Fg in the following percent by weight ratios: 100?:?0?:?0, 50?:?25?:?25, 50?:?50?:?0, 50?:?0?:?50, 0?:?0?:?100, and 0?:?50?:?50. Samples were immersed in (conventional (c), revised (r), ionic (i), and modified (m)) SBF for 5 and 14 days to induce mineralization. Scaffolds were characterized before and after mineralization via scanning electron microscopy, Alizarin Red-based assay, and modified burnout test. The addition of Fg resulted in scaffolds with smaller fiber diameters. Fg containing scaffolds also induced sheet-like mineralization while individual fiber mineralization was noticed in its absence. Mineralized electrospun Fg scaffolds without PDO were not mechanically stable after 5 days in SBF, but had superior mineralization capabilities which produced a thick bone-like mineral (BLM) layer throughout the scaffolds. 50?:?50?:?0 scaffolds incubated in either r-SBF for 5 days or c-SBF for 14 days produced scaffolds with high mineral content and individual-mineralized fibers. These mineralized scaffolds were still porous and will be further optimized as an effective bone substitute in future studies. PMID:22956956

Rodriguez, Isaac A.; Madurantakam, Parthasarathy A.; McCool, Jennifer M.; Sell, Scott A.; Yang, Hu; Moon, Peter C.; Bowlin, Gary L.

2012-01-01

258

Mechanical properties of calcium sulphate/hydroxyapatite cement.  

PubMed

Setting times, volume after setting, injectability and hardness (at 37 degrees C in contact with Ringer's solution) were determined for cements made of mixtures of calcium sulphate hemihydrate (CS) and hydroxyapatite (HA) with a range of compositions. The purpose of these experiments was to determine the behaviour of a mixture that could be used as an injectable cement for orthopaedic applications, including spinal fusion. A suitable mixture consisted of 60% CS and 40% HA by mass; a slurry was made by mixing solid (36 g) with water (15 cm(3)). The slurry had initial and final setting times of 5.7+/-1.3 min and 19.6+/-0.7 min (mean +/- standard deviation), respectively. The hardness of the cement did not systematically increase or decrease in the 72 h following the final setting time. The volume of the cement was 99.8+/-0.4% of the volume of the initial slurry, i.e. there was negligible shrinkage on setting. It was able to withstand a pressure of 7.3+/-1.2 MPa, applied by a hemispherical indenter before the onset of permanent damage, indicating adequate strength for spinal fusion. PMID:17119281

Lei, Dang; Wardlaw, D; Hukins, D W L

2006-01-01

259

The facile and low temperature synthesis of nanophase hydroxyapatite crystals using wet chemistry.  

PubMed

A simple and facile wet chemistry route was used to synthesize nanophase hydroxyapatite (HaP) crystals at low temperature. The synthesis was carried out at a pH of 11.0 and at a temperature of 37°C. The resulting samples were washed several times and subjected to further analysis. XRD studies revealed that the HaP crystals were polycrystalline in nature with a crystallite size of ~15-60 ± 5 nm. SEM-EDXA images confirmed the presence of calcium (Ca), phosphorous (P), and oxygen (O) peaks. Likewise, FTIR confirmed the presence of characteristic phosphate and hydroxyl peaks in samples. Lastly, HRTEM images clearly showed distinctive lattice fringes positioned in the 100 and 002 planes. TGA analysis shows that HaP crystals can withstand higher calcination temperatures and are thermally stable. PMID:24433898

Dhand, Vivek; Rhee, K Y; Park, Soo-Jin

2014-03-01

260

Experimental Analysis of Spray Dryer Used in Hydroxyapatite Thermal Spray Powder  

NASA Astrophysics Data System (ADS)

The spray drying process of hydroxyapatite (HA) powder used as a plasma spray powder on human hip implants was examined. The Niro-Minor mixed spray dryer was studied because it incorporates both co-current and counter-current air mixing systems. The process parameters of the spray drying were investigated: temperature, flow rate of the inlet hot air in the spray dryer, viscosity of feed/HA slurry, and responses (chamber and cyclone powder size, deposition of powder on the wall of spray dryer, and overall thermal efficiency). The statistical analysis (ANOVA test) showed that for the chamber particle size, viscosity was the most significant parameter, while for the cyclone particle size, the main effects were temperature, viscosity, and flow rate, but also their interaction effects were significant. The spray dried HA powder showed the two main shapes were a doughnut and solid sphere shape as a result of the different input.

Murtaza, Q.; Stokes, J.; Ardhaoui, M.

2012-09-01

261

Controlled release of rhodium (II) carboxylates and their association complexes with cyclodextrins from hydroxyapatite matrix.  

PubMed

Preparation and characterization of a controlled release system of rhodium (II) citrate, acetate. propionate, butyrate and their inclusion or association compounds with cyclodextrin (CD) are described. The porous hydroxyapatite (HA) was characterized by X-ray powder pattern diffraction, FTIR and solid state 31P NMR. Scanning electron microscopy and gas adsorption analysis (BET) were also performed. Release profiles of rhodium (II) carboxylates and their inclusion or association compounds from HA matrix were obtained at different drug loadings (5% and 10%). These were reasonably consistent with a diffusion model. This analysis, mainly using rhodium (II) citrate and butyrate, showed that the strategy of using CDs with a HA matrix may offer a useful new method for the controlled release of these compounds, and hence an alternative strategy for the controlled release of chemotherapeutic agents containing toxic metals. This may be a valuable new technique for localized anti-tumour chemotherapy that minimizes the side effects of such agents. PMID:12033599

Burgos, A E; Belchior, J C; Sinisterra, R D

2002-06-01

262

The composite of hydroxyapatite and calcium sulphate: a review of preclinical evaluation and clinical applications.  

PubMed

Recent publications have shown that the combination of ?-calcium sulfate hemihydrate, the densest form of hydrates and hydroxyapatite (HA) particles gives good clinical outcome in various applications. It has large potential as bone substitute since the material transforms to bone throughout the entire volume and not only by creeping substitution, from the surface toward the inside. Release of important proteins for osteogenesis has been observed around implanted material and is speculated to be due to fast dissolution of the calcium sulfate phase in combination with the osteoconductive and bioactive nature of HA. In diabetic foot infection, the osteoconductive HA/calcium sulfate material has been successfully used loaded with antibiotics and since it is injectable, the application is minimally invasive, easy and precise. It is a bone substitute for the future. PMID:24053255

Nilsson, Malin; Zheng, Ming H; Tägil, Magnus

2013-09-01

263

The Effect of Hydroxyapatite Nanocrystals on Osseointegration of Titanium Implants: An In Vivo Rabbit Study  

PubMed Central

Osseointegration is dependent on implant surface characteristics, including surface chemistry and topography. The presence of nanosized calcium phosphates on the implant surface is interesting to investigate since they affect both the nanotopography and surface chemistry, forming a bone mineral resembling surface. In this work, the osseointegration of titanium implants with and without the presence of hydroxyapatite (HA) nanocrystals has been evaluated in vivo. The integration was examined using removal torque measurements and real-time polymerase chain reaction (RT-PCR) analysis. The study was performed using two healing time points, 3 and 12 weeks. The results showed that the torque needed to remove the implants was insignificant between the non- and HA-coated implants, both at weeks 3 and 12. The RT-PCR, however, showed significant differences for osteoblast, osteoclast, and proinflammation markers when HA nanocrystals were present. PMID:24563651

Breding, Karin; Jimbo, Ryo; Hayashi, Mariko; Xue, Ying; Mustafa, Kamal; Andersson, Martin

2014-01-01

264

The adsorptive behavior of albumin and lysozyme proteins on rod-shaped and plate-shaped hydroxyapatite.  

PubMed

The adsorption behavior of albumin (BSA) and lysozyme (LSZ) on rod-shaped and plate-shaped hydroxyapatite (HA) was investigated to evaluate the influence of crystal orientation and morphology on the selective protein adsorption of HA. The rod-shaped HA was prepared by hydrothermal treatment from ?-tricalcium phosphate (?-TCP) in H3PO4 solution (pH 2.0 and 4.0 for HA-pH 2.0 and HA-pH 4.0). The plate-shaped HA was synthesized by hydrolysis of CaHPO4-2H2O (DCPD) in NaOH solution at 40°C and 80°C (HA-40°C and HA-80°C). The synthesized HA was characterized using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). HA-pH 2.0 and HA-pH 4.0 produced rod-shaped crystals that were highly oriented to the a-face plane, whereas HA-40°C and HA-80°C showed a plate-like shape and a c-face preferred orientation. The peak intensity ratio I(300)/I(002) (a/c intensity ratio) from the XRD patterns increased in the following order: HA-80°C, HA-40°C, HA-pH 2.0 and HA-pH 4.0. It also increased as the Ca/P ratio decreased. The amount of adsorbed BSA increased in the following order: HA-pH 4.0, HA-pH 2.0, HA-40°C and HA-80°C. The amount of adsorbed LSZ on HA increased in the following order--HA-pH 2.0, HA-pH 4.0, HA-40°C and HA-80°C--with a corresponding decrease in the a/c intensity ratio. The BSA/LSA adsorption ratio increased with the a/c intensity ratio in the range of 3.3-8.9, and the BSA and LSZ were selectively adsorbed on HA, depending on the crystal shape. PMID:23629536

Ozeki, K; Hoshino, T; Aoki, H; Masuzawa, T

2013-01-01

265

Facile fabrication of porous ZnO microspheres by thermal treatment of ZnS microspheres.  

PubMed

Porous ZnO microspheres with an average size of around 500 nm had been synthesized by thermal treatment of ZnS microspheres in an air atmosphere. The ZnS spheres had been synthesized at a low temperature of 100 degrees C by using L-cysteine (an ordinary amino acid) as a sulfur source with the assist of gelatin. By combining the results of X-ray diffraction (XRD), transmission electron microscope (TEM), field-emission scanning electron microscopy (FE-SEM), and Fourier transformation infrared spectra (FTIR), a structural and morphological characterization of the products was performed. The photocatalytic activity of ZnS microspheres and porous ZnO microspheres have been tested by degradation of Rhodamine-B (RB) under UV light, indicating that the porous ZnO microspheres showed enhanced photocatalytic performance compared to ZnS microspheres and commercial Degussa P25 TiO(2). PMID:19913355

Wu, Xiao; Li, KunWei; Wang, Hao

2010-02-15

266

Bisphosphonate release profiles from magnetite microspheres.  

PubMed

Hyperthermia has been suggested as a novel, minimally invasive cancer treatment method. After implantation of magnetic nano- or microparticles around a tumour through blood vessels, irradiation with alternating magnetic fields facilitates the efficient in situ hyperthermia even for deep-seated tumours. On the basis of this idea, if the microspheres are capable of delivering drugs, they could be promising multifunctional biomaterials effective for chemotherapy as well as hyperthermia. In the present study, magnetite microspheres were prepared by aggregation of the iron oxide colloid in water-in-oil (W/O) emulsion. The release behaviour of alendronate, a typical bisphosphonate, from the microspheres was examined in vitro as a model of the bone tumour prevention and treatment system. The alendronate was successfully incorporated onto the porous magnetite microspheres in vacuum conditions. The drug-loaded microspheres maintained their original spherical shapes even after shaking in ultrapure water for 3 days, suggesting that they have sufficient mechanical integrity for clinical use. It was attributed to high aggregation capability of the magnetite nanoparticles through van der Waals and weak magnetic attractions. The microspheres showed slow release of the alendronate in vitro, resulting from tight covalent or ionic interaction between the magnetite and the alendronate. The release rate was diffusion-controlled type and well controlled by the alendronate concentration in drug incorporation to the microspheres. PMID:24854985

Miyazaki, Toshiki; Inoue, Tatsuya; Shirosaki, Yuki; Kawashita, Masakazu; Matsubara, Takao; Matsumine, Akihiko

2014-10-01

267

Development of high strength hydroxyapatite for bone tissue regeneration using nanobioactive glass composites  

SciTech Connect

With an increasing demand of biocompatible bone substitutes for the treatment of bone diseases and bone tissue regeneration, bioactive glass composites are being tested to improvise the osteoconductive as well as osteoinductive properties. Nanobioactive glass (nBG) composites, having composition of SiO{sub 2} 70 mol%, CaO 26 mol % and P{sub 2}O{sub 5} 4 mol% were prepared by Freeze drying method using PEG-PPG-PEG co-polymer. Polymer addition improves the mechanical strength and porosity of the scaffold of nBG. Nano Bioactive glass composites upon implantation undergo specific reactions leading to the formation of crystalline hydroxyapatite (HA). This is tested in vitro using Simulated Body Fluid (SBF). This high strength hydroxyapatite (HA) layer acts as osteoconductive in cellular environment, by acting as mineral base of bones, onto which new bone cells proliferate leading to new bone formation. Strength of the nBG composites as well as HA is in the range of cortical and cancellous bone, thus proving significant for bone tissue regeneration substitutes.

Shrivastava, Pragya; Dalai, Sridhar; Vijayalakshmi, S. [Centre for Research in Nanotechnology and Science, IIT Bombay (India); Sudera, Prerna; Sivam, Santosh Param [Amity Institute of Nanotechnology, Amity University, Noida, Uttar Pradesh-201303 (India); Sharma, Pratibha [Dept of Energy Science and Engineering, IIT Bombay (India)

2013-02-05

268

Pulsed laser deposition of thin film hydroxyapatite. Applications for flexible catheters.  

PubMed

Skin exit site infections are a major source of morbidity in patients with indwelling percutaneous catheters. Ceramic materials, such as hydroxyapatite (HA) and alumina, have demonstrated excellent biocompatibility and low rates of infection in soft tissues. Previous attempts to design ceramic materials for use as percutaneous connectors have resulted in rigid discs or solid cylindrical tubes. In order to take advantage of the inherent properties of HA without reducing patient comfort or mobility, the feasibility of applying a thin film of HA directly onto a flexible polymeric catheter was studied. The coating was applied by pulsed laser deposition (PLD). The beam from a KrF excimer laser impinged upon a target of pressed and sintered HA, producing a plume of ablated material that was deposited onto the catheter tubing. By rotating the tubing, an even coating of HA was applied to the catheter at a thickness of approximately 0.50 microm. The coating did not compromise the flexibility of the catheter tubing. Hence, PLD of a thin film of HA at the exit site of percutaneous catheters may be a means of incorporating the bioactive and biocompatible properties of HA with the mobility and patient comfort that characterize polymeric catheters. PMID:8555642

Zabetakis, P M; Cotell, C M; Chrisey, D B; Auyeung, R C

1994-01-01

269

Preparation and in vitro evaluation of mesoporous hydroxyapatite coated ?-TCP porous scaffolds.  

PubMed

A mesoporous hydroxyapatite (HA) coating was prepared on a ?-tricalcium phosphate (?-TCP) porous scaffold by a sol-gel dip-coating method using the block copolymer Pluronic F127 (EO106PO70EO106) as the template. For application as a bone graft, in vitro cell response and bone-related protein expression of mesoporous HA coated ?-TCP scaffold were investigated, using the non-mesoporous HA coated scaffold as the control group, to evaluate the influence of the mesoporous structure on the biological properties of HA coating. It was found that the increased surface area of the mesoporous HA coating greatly affected the response of MC3T3-E1 osteoblasts and the expression of proteins. An enzyme-linked immunosorbent assay recorded a significantly higher expression of alkaline phosphatase (ALP) and bone sialoprotein (BSP) in the mesoporous group than those in the control group (*p<0.05) after different incubation periods. The introduction of mesopores enhanced the expression of ALP and BSP in the cells grown on the mesoporous HA coatings, on the premise of maintaining the protein expression in a sequence to ensure the correct temporo-spatial expression in osteogenesis. These results indicated that the mesoporous HA coating would provide a good environment for cell growth, suggesting that it could be used as the coating material for the surface modification of the tissue engineering scaffolds. PMID:24094217

Ye, Xinyu; Cai, Shu; Xu, Guohua; Dou, Ying; Hu, Hongtao; Ye, Xiaojian

2013-12-01

270

Hydrothermally mixed hydroxyapatite-multiwall carbon nanotubes composite coatings on biomedical alloys by electrophoretic deposition.  

PubMed

Hydroxyapatite (HA) coatings have been used to improve biological and mechanical fixation of metallic prosthesis. Because of extraordinary features of carbon nanotubes (CNTs), they have a lot of facilities, such as extremely strong nanoreinforcement materials for composites. HA powders were synthesized and mixed with multiwalled carbon nanotubes (MWCNTs) by a hydrothermal process. Calcium acetate (Ca (CH(3)COO)(2)) and phosphoric acid (H(3)PO(4)) were used as starting materials for synthesizing nano-HA powders. HA-MWCNTs were treated together hydrothermally at 200 °C for 2 h to synthesize nano-HA powders mixed homogeneously with MWCNTs. Cathodic deposits were obtained on Ti-based alloys using suspensions containing nano-HA and MWCNTs dispersed in n-butanol solvent. It was shown that MWCNTs interacted with HA powders during hydrothermal processing, and therefore, they can easily be dispersed within aqueous-based suspensions. It was also shown that hydrothermal surface modification of MWCNTs with functional groups was achievable, which was a significant step toward eliminating nonwetting surface behavior of MWCNTs, resulting in obtaining homogeneous dispersion of them in liquids. PMID:22780563

Ustundag, C B; Avciata, O; Kaya, F; Kaya, C

2013-02-14

271

Porous alumina-hydroxyapatite composites through protein foaming-consolidation method.  

PubMed

This report presents physical characterization and cell culture test of porous alumina-hydroxyapatite (HA) composites fabricated through protein foaming-consolidation technique. Alumina and HA powders were mixed with yolk and starch at an adjusted ratio to make slurry. The resulting slip was poured into cylindrical shaped molds and followed by foaming and consolidation via 180 °C drying for 1 h. The obtained green bodies were burned at 600 °C for 1 h, followed by sintering at temperatures of 1200-1550 °C for 2 h. Porous alumina-HA bodies with 26-77 vol.% shrinkage, 46%-52% porosity and 0.1-6.4 MPa compressive strength were obtained. The compressive strength of bodies increased with the increasing sintering temperatures. The addition of commercial HA in the body was found to increase the compressive strength, whereas the case is reverse for sol-gel derived HA. Biocompatibility study of porous alumina-HA was performed in a stirred tank bioreactor using culture of Vero cells. A good compatibility of the cells to the porous microcarriers was observed as the cells attached and grew at the surface of microcarriers at 8-120 cultured hours. The cell growth on porous alumina microcarrier was 0.015 h(-1) and increased to 0.019 h(-1) for 0.3 w/w HA-to-alumina mass ratio and decreased again to 0.017 h(-1) for 1.0 w/w ratio. PMID:22402156

Sopyan, I; Fadli, A; Mel, M

2012-04-01

272

Reinforced Pulsed Laser-Deposited Hydroxyapatite Coating on 316 Stainless Steel  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) is a widely used bioceramic known for its chemical similarity with that of bone and teeth (Ca/P ratio of 1.67). But, owing to its extreme brittleness, ?-Al2O3 is reinforced with HA and processed as a coating via pulsed laser deposition (PLD). Reinforcement of ?-Al2O3 (50 wt.%) in HA via PLD on 316L steel substrate has shown modulus increase by 4% and hardness increase by 78%, and an improved adhesion strength of 14.2 N (improvement by 118%). Micro-scratching has shown an increase in the coefficient-of-friction from 0.05 (pure HA) to 0.17 (with 50 wt.% Al2O3) with enhancement in the crack propagation resistance (CPR) up to 4.5 times. Strong adherence of PLD HA-Al2O3 coatings (~4.5 times than that of HA coating) is attributed to efficient release of stored tensile strain energy (~17 × 10-3 J/m2) in HA-Al2O3 composites, making it a potential damage-tolerant bone-replacement surface coating.

Bajpai, Shubhra; Gupta, Ankur; Pradhan, Siddhartha Kumar; Mandal, Tapendu; Balani, Kantesh

2014-10-01

273

Factors influencing the compressive strength of an injectable calcium sulfate-hydroxyapatite cement.  

PubMed

A biphasic injectable bone substitute, suitable for filling bone defects, that sets in the body, based on calcium sulfate and hydroxyapatite (HA), is presented. For applications in bone defects the compressive strength is important to assure support of the defect site during loading when the patient is weight bearing. To control the strength, the influence of four different factors; the liquid-to-powder (L/P) ratio, the HA particle morphology, the HA content and the amount of accelerator, were investigated. alpha-Calcium sulfate hemihydrate (CSH) and four different HA powders (three sintered and one spray-dried) were used. All differed in size and morphology. CSH and each HA powder were mixed together with distilled water to form the bone substitute. An accelerator, in form of calcium sulfate dihydrate, was added to the powder phase to obtain an adequate setting time. Cylindrical specimens were compression tested. A lower L/P-ratio gave stronger cement, but was more difficult to inject. The shape and the morphology of the HA particles influenced the strength, and reducing the amount of HA increased the strength. The amount of accelerator (calcium sulfate dihydrate) had no influence. PMID:15348442

Nilsson, M; Wielanek, L; Wang, J-S; Tanner, K E; Lidgren, L

2003-05-01

274

In vivo comparison of the osseointegration of vacuum plasma sprayed titanium- and hydroxyapatite-coated implants.  

PubMed

For the last 15 years, orthopedic implants have been coated with hydroxyapatite (HA) to improve implant fixation. The osteoconductive effect of HA coatings has been demonstrated in experimental and clinical studies. However, there are ongoing developments to improve the quality of HA coatings. The objective of this study was to investigate whether a rough and highly crystalline HA coating applied by vacuum plasma spraying (VPS) had a positive effect on the osseointegration of special, high-grade titanium (Ti) implants with the same surface roughness. Ti alloy implants were coated (VPS) with special, high-grade Ti or HA. The osseointegration of the implants was evaluated by either light microscopy or pullout tests after 1, 2, and 4 weeks of unloaded implantation in the cancellous bone of 18 sheep. The interface shear strength increased significantly over all time intervals. By 4 weeks, values had reached approximately 10N/mm(2). However, the difference between the coatings was not significant at any time interval. Direct bone-implant contact was significantly different between the coatings after 2 and 4 weeks, and reached 46% for Ti and 68% for HA implants by 4 weeks. This study indicates that the use of a rough and highly crystalline HA coating, applied by VPS, enhances early osseointegration. Accelerated establishment of secondary implant fixation decreases the risk of early loosening. PMID:12889006

Aebli, Nikolaus; Krebs, Jörg; Stich, Hermann; Schawalder, Peter; Walton, Mark; Schwenke, Daryl; Gruner, Heiko; Gasser, Beat; Theis, Jean-Claude

2003-08-01

275

Carbon Nanotubes in Nanocomposites and Hybrids with Hydroxyapatite for Bone Replacements  

PubMed Central

Hydroxyapatite (HA), as a bone mineral component, has been an attractive bioceramic for the reconstruction of hard tissues. However, its poor mechanical properties, including low fracture toughness and tensile strength, have been a significant challenge to the application of HA for the replacement of load-bearing and/or large bone defects. Among materials studied to reinforce HA, carbon nanotubes (CNTs: single-walled or multiwalled) have recently gained significant attention because of their unprecedented mechanical properties (high strength and toughness) and physicochemical properties (high surface area, electrical and thermal conductivity, and low weight). Here, we review recent studies of the organization of HA-CNTs at the nanoscale, with a particular emphasis on the functionalization of CNTs and their dispersion within an HA matrix and induction of HA mineralization. The organization of CNTs and HA implemented at the nanoscale can further be developed in the form of coatings, nanocomposites, and hybrid powders to enable potential applications in hard tissue reconstruction. PMID:21776341

Shin, Ueon Sang; Yoon, Il-Kyu; Lee, Gil-Su; Jang, Won-Cheoul; Knowles, Jonathan C.; Kim, Hae-Won

2011-01-01

276

Prediction of mechanical properties of composites of HDPE/HA/EAA.  

PubMed

In this investigation, the behavior of the mechanical properties of composites of high-density polyethylene/hydroxyapatite (HDPE/HA) with and without ethylene-acrylic acid copolymer (EAA) as possible compatibilizer, was studied. Different mathematical models were used to predict their Young's modulus, tensile strength and elongation at break. A comparison with the experimental results shows that the theoretical models of Guth and Kerner modified can be used to predict the Young's modulus. On the other hand, the values obtained by the Verbeek model do not show a good agreement with the experimental data, since different factors that influence the mechanical properties are considered in this model such as: aspect ratio of the reinforcement, interfacial adhesion, porosity and binder content. TEM analysis confirms the discrepancies obtained between the experimental Young's modulus values and those predicted by the Verbeek model. The values of "P", "a" and "?(A)" suggest that an interaction among the carboxylic groups of the copolymer and the hydroxyl groups of hydroxyapatite might be present. In composites with 20 and 30 wt% of filler, this interaction does not improve the Young's modulus values, since the deviations of the Verbeek model are significant. PMID:21316635

Albano, C; Perera, R; Cataño, L; Karam, A; González, G

2011-04-01

277

Aceclofenac microspheres: quality by design approach.  

PubMed

The purpose of this study was to prepare polymeric microspheres containing aceclofenac by single emulsion [oil-in-water (o/w)] solvent evaporation method. Two biocompatible polymers, ethylcellulose, and Eudragit® RS100 were used in combination. Seven processing factors were investigated by Plackett-Burman design (PBD) in order to enhance the encapsulation efficiency of the microspheres. A Plackett-Burman design was employed by using the Design-Expert® software (Version-8.0.7.1). The resultant microspheres were characterized for their size, morphology, encapsulation efficiency, and drug release. Imaging of particles was performed by field emission scanning electron microscopy. Interaction between the drug and polymers were investigated by Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffractometry (XRPD). Graphical and mathematical analyses of the design showed that Eudragit® RS100, and polyvinyl alcohol (PVA) were significant negative effect on the encapsulation efficiency and identified as the significant factor determining the encapsulation efficiency of the microspheres. The low magnitudes of error and the significant values of R(2) in the present investigation prove the high prognostic ability of the design. The microspheres showed high encapsulation efficiency (70.15% to 83.82%). The microspheres were found to be discrete, oval with smooth surface. The FTIR analysis confirmed the compatibility of aceclofenac with the polymers. The XRPD revealed the dispersion of drug within microspheres formulation. Perfect prolonged drug release profile over 12h was achieved by a combination of ethylcellulose, and Eudragit® RS100 polymers. In conclusion, polymeric microspheres containing aceclofenac can be successfully prepared using the technique of experimental design, and these results helped in finding the optimum formulation variables for encapsulation efficiency of microspheres. PMID:24433918

Deshmukh, Rameshwar K; Naik, Jitendra B

2014-03-01

278

Chapter 24 Protein Chromatography on Hydroxyapatite Columns  

Microsoft Academic Search

The introduction of spherical forms of hydroxyapatite has enabled protein scientists to separate and purify proteins multiple times with the same packed column. Biopharmaceutical companies have driven single column applications of complex samples to simpler samples obtained from upstream column purification steps on affinity, ion exchange or hydrophobic interaction columns. Multiple column purification permits higher protein loads to spherical forms

Larry J. Cummings; Mark A. Snyder; Kimberly Brisack

2009-01-01

279

Effect of calcination on sintering of hydroxyapatite  

Microsoft Academic Search

Four different temperatures (700–1000 °C) were chosen for calcination treatment of as-received hydroxyapatite powder before press forming and sintering to study the effect of calcination on the sintering behaviours. The results show that calcination treatment increases the average particle size and distribution, which changes from trimodal to monomodal. The sintering behaviours were investigated by dilatometry and density measurement. Fluidity of

Horng Yih Juang; Min Hsiung Hon

1996-01-01

280

Thermal processing of hydroxyapatite for coating production.  

PubMed

Thermally processed hydroxyapatite coatings used on dental implants and hip prostheses for enhanced fixation may typically consist of a number of chemical and structural phases. These phases affect coating performance and tissue attachment. Hydroxyapatite was plasma sprayed to examine the phase evolution during processing. Coatings were examined with X-ray diffraction and elemental analysis. Results indicate that phase transformations are produced by (a) preferential removal of hydroxyl and phosphate leading to a change in melt composition, and (b) the high cooling rate due to the thermal spray process. Hydroxyl group removal promotes the amorphous phase and oxyapatite. Further heating produces a less viscous melt facilitating decomposition of hydroxyapatite to tricalcium and tetracalcium phosphate. Phosphate removal during flight produces a more calcium-rich melt preferring tetracalcium phosphate and calcium oxide formation. A proposed model shows the phase location within the lamellae of these coatings. Coating processes must thus prevent removal of hydroxide and phosphate during processing to maximize the hydroxyapatite content. PMID:9492219

Gross, K A; Berndt, C C

1998-03-15

281

Influence of humate on calcium hydroxyapatite implants  

Microsoft Academic Search

Implanted bovine apatite is highly osteoconductive, since it serves the host tissue as a “guide-line” for the deposition of newly developing bone tissue. It is well tolerated, but it showed no signs of being resorbed during the course of the experiment. Previous impregnation of the bovine hydroxyapatite with a low molecular humate substance obviously encourages its resorption. This is most

W. Schlickewei; U. N. Riede; J. Yu; W. Ziechmann; E. H. Kuner; B. Seubert

1993-01-01

282

Synthesis and structural characterization of nano-hydroxyapatite biomaterials prepared by microwave processing  

NASA Astrophysics Data System (ADS)

Synthetic hydroxyapatite, (HA, Ca10(PO4)6(OH)2), is an attractive and widely utilized bio-ceramic material for orthopedic and dental implants because of its close resemblance of native tooth and bone crystal structure. Synthetic HA exhibits excellent osteoconductive properties. Osteoconductivity means the ability to provide the appropriate scaffold or template for bone formation. Calcium phosphate biomaterials [(HA), tri-calcium phosphate (TCP) and biphasic calcium phosphate (HA/TCP)] with appropriate three-dimensional geometry are able to bind and concentrate endogenous bone morphogenetic proteins in circulation, and may become osteoinductive and can be effective carriers of bone cell seeds. This HA can be used in bio-implants as well as drug delivery application due to the unique properties of HA. Biomaterials synthesized from the natural species like mussel shells have additional benefits such as high purity, less expensive and high bio compatibility. In this project, HA-nanoparticles of different crystallite size were prepared by microwave synthesis of precursors. High purity CaO was extracted from the natural mussel shells for the synthesis of nano HA. Dried nano HA powders were analyzed using X-Ray Diffraction (XRD) technique for the determination of crystal structure and impurity content. Scanning Electron Microscopic (SEM) investigation was employed for the morphological investigation of nano HA powders. From the results obtained, it was concluded that by altering the irradiation time, nano HA powders of different crystallite sizes and morphologies could be produced. Crystallite sizes calculated from the XRD patterns are found to be in the range of 10-55 nm depending on the irradiation time.

Ramli, Rosmamuhamadani; Arawi, Ainaa Zafirah Omar; Talari, Mahesh Kumar; Mahat, Mohd Muzamir; Jais, Umi Sarah

2012-07-01

283

Electrospinning growth factor releasing microspheres into fibrous scaffolds.  

PubMed

This procedure describes a method to fabricate a multifaceted substrate to direct nerve cell growth. This system incorporates mechanical, topographical, adhesive and chemical signals. Mechanical properties are controlled by the type of material used to fabricate the electrospun fibers. In this protocol we use 30% methacrylated Hyaluronic Acid (HA), which has a tensile modulus of ~500 Pa, to produce a soft fibrous scaffold. Electrospinning on to a rotating mandrel produces aligned fibers to create a topographical cue. Adhesion is achieved by coating the scaffold with fibronectin. The primary challenge addressed herein is providing a chemical signal throughout the depth of the scaffold for extended periods. This procedure describes fabricating poly(lactic-co-glycolic acid) (PLGA) microspheres that contain Nerve Growth Factor (NGF) and directly impregnating the scaffold with these microspheres during the electrospinning process. Due to the harsh production environment, including high sheer forces and electrical charges, protein viability is measured after production. The system provides protein release for over 60 days and has been shown to promote primary nerve cell growth. PMID:25178038

Whitehead, Tonya J; Sundararaghavan, Harini G

2014-01-01

284

Effects of DCPD Cement Chemistry on Degradation Properties and Cytocompatibility: Comparison of MCPM/?-TCP and MCPM/HA Formulations  

PubMed Central

Dicalcium phosphate dihydrate (DCPD) cements are attractive biomaterials for bone repair, and a number of different DCPD cement formulations have been proposed in the literature. In this study we have specifically compared monocalcium phosphate monohydrate (MCPM)/hydroxyapatite (HA) and MCPM/?-tricalcium phosphate (?-TCP) formulations to test the hypothesis that DCPD cement chemistry affects the degradation properties and cytocompatibility of the cement. Using simple in vitro models we found that MCPM/?-TCP formulations degraded primarily by DCPD dissolution, which was associated with a slight pH drop and relatively low mass loss. Cytocompatibility testing of cement conditioned culture media revealed no significant change in cell viability relative to the negative control for all of the MCPM/?-TCP formulations. In contrast, the MCPM/HA formulations were prone to undergo rapid conversion of DCPD to HA, resulting in a sharp pH drop and extensive mass loss. A stoichiometric excess of HA in the cement was found to accelerate the conversion process, and significant cytotoxicity was observed for the MCPM/HA formulations containing excess HA. Collectively, these results show that, although the product of the setting reaction is the same, DCPD cements produced with MCPM/HA and MCPM/?-TCP formulations differ significantly in their degradation properties and cytocompatibility. These differences may have important implications for the selection of a DCPD cement formulation for clinical application. PMID:23428798

Alge, Daniel L.; Goebel, W. Scott; Chu, Tien-Min Gabriel

2013-01-01

285

Fabrication and in vitro biocompatibility of biomorphic PLGA/nHA composite scaffolds for bone tissue engineering.  

PubMed

In this study, biomorphic poly(dl-lactic-co-glycolic acid)/nano-hydroxyapatite (PLGA/nHA) composite scaffolds were successfully prepared using cane as a template. The porous morphology, phase, compression characteristics and in vitro biocompatibility of the PLGA/nHA composite scaffolds and biomorphic PLGA scaffolds as control were investigated. The results showed that the biomorphic scaffolds preserved the original honeycomb-like architecture of cane and exhibited a bimodal porous structure. The average channel diameter and micropore size of the PLGA/nHA composite scaffolds were 164 ± 52 ?m and 13 ± 8 ?m, respectively, with a porosity of 89.3 ± 1.4%. The incorporation of nHA into PLGA decreased the degree of crystallinity of PLGA, and significantly improved the compressive modulus of biomorphic scaffolds. The in vitro biocompatibility evaluation with MC3T3-E1 cells demonstrated that the biomorphic PLGA/nHA composite scaffolds could better support cell attachment, proliferation and differentiation than the biomorphic PLGA scaffolds. The localization depth of MC3T3-E1 cells within the channels of the biomorphic PLGA/nHA composite scaffolds could reach approximately 400 ?m. The results suggested that the biomorphic PLGA/nHA composite scaffolds were promising candidates for bone tissue engineering. PMID:24433891

Qian, Junmin; Xu, Weijun; Yong, Xueqing; Jin, Xinxia; Zhang, Wei

2014-03-01

286

Prolonged release from PLGA/HAp scaffolds containing drug-loaded PLGA/gelatin composite microspheres.  

PubMed

Porous scaffolds that can prolong the release of bioactive factors are urgently required in bone tissue engineering. In this study, PLGA/gelatin composite microspheres (PGMs) were carefully designed and prepared by entrapping poly(L: -lactide-co-glycolide) (PLGA) microspheres (PMs) in gelatin matrix. By mixing PGMs with PLGA solution directly, drug-loaded PLGA/carbonated hydroxyapatite (HAp)/PGMs composite scaffolds were successfully fabricated. In vitro release of fluorescein isothiocyanate-dextran (FD70S) as a model drug from the scaffolds as well as PMs and PGMs was studied by immersing samples in phosphate buffered saline (pH = 7.4) at 37°C for 32 days. Compared with PMs, PGMs and PLGA/HAp/PGMs scaffolds exhibited slow and steady release behavior with constant release rate and insignificantly original burst release. The swelling of PGMs, diffusion of drugs, and degradation of polymer dominated the release behaviors synergistically. The PLGA/HAp/PGMs scaffold offers a novel option for sequential or simultaneous release of several drugs in terms of bone regeneration. PMID:22095448

Tang, Gongwen; Zhang, Hong; Zhao, Yunhui; Li, Xiao; Yuan, Xiaoyan; Wang, Min

2012-02-01

287

SRNL POROUS WALL GLASS MICROSPHERES  

SciTech Connect

The Savannah River National Laboratory (SRNL) has developed a new medium for storage of hydrogen and other gases. This involves fabrication of thin, Porous Walled, Hollow Glass Microspheres (PW-HGMs), with diameters generally in the range of 1 to several hundred microns. What is unique about the glass microballons is that porosity has been induced and controlled within the thin, one micron thick walls, on the scale of 10 to several thousand Angstroms. This porosity results in interesting properties including the ability to use these channels to fill the microballons with special absorbents and other materials, thus providing a contained environment even for reactive species. Gases can now enter the microspheres and be retained on the absorbents, resulting in solid-state and contained storage of even reactive species. Also, the porosity can be altered and controlled in various ways, and even used to filter mixed gas streams within a system. SRNL is involved in about a half dozen different programs involving these PW-HGMs and an overview of some of these activities and results emerging are presented.

Wicks, G; Leung Heung, L; Ray Schumacher, R

2008-04-15

288

Protease immobilization onto polyacrolein microspheres.  

PubMed

Water-insoluble proteases were prepared by immobilizing papain and chymotrypsin onto the surface of polyacrolein microspheres with and without oligoglycines as spacer. The activity of immobilized proteases was found to be still high toward small ester substrates, but very low toward casein, a high-molecular-weight substrate. The relative activity of the immobilized proteases without spacer decreased gradually with the decreasing surface concentration of the immobilized proteases on the microspheres. On the contrary, the immobilized proteases with oligoglycine spacers gave an almost constant activity for the substrate hydrolysis within the surface concentration region studied and gave a much higher relative activity than those without any spacer. With the longer spacer, the immobilized enzymes showed a higher activity toward casein hydrolysis, whereas there was an optimum length for the spacer when hydrolysis was carried out toward the low-molecular-weight substrate. The thermal stability of the immobilized proteases was higher than that of the respective native proteases. The initial enzymatic activity of the immobilized proteases maintained almost unchanged without any elimination and inactivation of proteases, when the batch enzyme reaction was performed repeatedly, indicating the excellent durability. PMID:18592545

Hayashi, T; Ikada, Y

1990-03-01

289

Precision Extruding Deposition for Freeform Fabrication of PCL and PCL-HA Tissue Scaffolds  

NASA Astrophysics Data System (ADS)

Computer-aided tissue engineering approach was used to develop a novel Precision Extrusion Deposition (PED) process to directly fabricate Polycaprolactone (PCL) and composite PCL/Hydroxyapatite (PCL-HA) tissue scaffolds. The process optimization was carried out to fabricate both PCL and PCL-HA (25% concentration by weight of HA) with a controlled pore size and internal pore structure of the 0°/90° pattern. Two groups of scaffolds having 60 and 70% porosity and with pore sizes of 450 and 750 microns, respectively, were evaluated for their morphology and compressive properties using Scanning Electron Microscopy (SEM) and mechanical testing. The surface modification with plasma was conducted on PCL scaffold to increase the cellular attachment and proliferation. Our results suggested that inclusion of HA significantly increased the compressive modulus from 59 to 84 MPa for 60% porous scaffolds and from 30 to 76 MPa for 70% porous scaffolds. In vitro cell-scaffolds interaction study was carried out using primary fetal bovine osteoblasts to assess the feasibility of scaffolds for bone tissue engineering application. In addition, the results in surface hydrophilicity and roughness show that plasma surface modification can increase the hydrophilicity while introducing the nano-scale surface roughness on PCL surface. The cell proliferation and differentiation were calculated by Alamar Blue assay and by determining alkaline phosphatase activity. The osteoblasts were able to migrate and proliferate over the cultured time for both PCL as well as PCL-HA scaffolds. Our study demonstrated the viability of the PED process to the fabricate PCL and PCL-HA composite scaffolds having necessary mechanical property, structural integrity, controlled pore size and pore interconnectivity desired for bone tissue engineering.

Shor, L.; Yildirim, E. D.; Güçeri, S.; Sun, W.

290

Characterization of a Polyamine Microsphere and Its Adsorption for Protein  

PubMed Central

A novel polyamine microsphere, prepared from the water-in-oil emulsion of polyethylenimine, was characterized. The investigation of scanning electron microscopy showed that the polyamine microsphere is a regular ball with a smooth surface. The diameter distribution of the microsphere is 0.37–4.29 ?m. The isoelectric point of the microsphere is 10.6. The microsphere can adsorb proteins through the co-effect of electrostatic and hydrophobic interactions. Among the proteins tested, the highest value of adsorption of microsphere, 127.8 mg·g?1 microsphere, was obtained with lipase. In comparison with other proteins, the hydrophobic force is more important in promoting the adsorption of lipase. The microsphere can preferentially adsorb lipase from an even mixture of proteins. The optimum temperature and pH for the selective adsorption of lipase by the microsphere was 35 °C and pH 7.0. PMID:23344018

Wang, Feng; Liu, Pei; Nie, Tingting; Wei, Huixian; Cui, Zhenggang

2013-01-01

291

The influence of pH and temperature on the morphology of hydroxyapatite synthesized by hydrothermal method  

Microsoft Academic Search

Hydroxyapatite (HA) whiskers and crystals were synthesized by hydrothermal treatment of Ca(OH)2 and CaHPO4·2H2O. Different conditions relative to pH=6–14, temperature=60–140 °C have been investigated in order to ascertain their influence on the HA particle structure and morphology. Results have shown that pH value is a significant parameter variable in altering the morphology. Well elongated particles were obtained on condition that pH=9

Jingbing Liu; Xiaoyue Ye; Hao Wang; Mankang Zhu; Bo Wang; Hui Yan

2003-01-01

292

Syntheses of near-net-shaped monolithic hydroxyapatite and hydroxyapatite-ASTM F75 composites by the oxidation of solid metal-bearing precursors  

NASA Astrophysics Data System (ADS)

A novel powder-metallurgical route was used to fabricate near net-shaped hydroxyapatite, Ca10(PO4)6(OH)2 (HA) and HA+Co-C-Mo composite bodies. Ca and beta-Ca2P 2O7 with Ca/P ˜ 1.67 was intimately mixed by high-energy mechanical alloying, formed into desired shapes by pressing and machining, and then converted into HA with a series of heat treatments: a 600°C annealing in dry O2 completely oxidized calcium within 3 h, and a subsequent annealing at ?1150°C in moist O2 yielded phase-pure HA. The reduction in solid volume associated with the oxidation of calcium (Vm[CaO] < Vm[Ca]) was offset by the increase in solid volume associated with the conversion of CaO and Ca2P2O7 into HA. Thus, the overall dimensional changes upon transformation of Ca+beta-Ca2P 2O7 precursors into HA can be relatively small. A mixture of Co-Cr-Mo powder with the precursor prepared from Ca and beta-Ca 2P2O7, targeted to yield a 75 to 25 volume ratio of Co-Cr-Mo to stoichiometric HA were prepared with the same method but different annealing cycles: annealing at 1150°C in de-oxygenized, flowing Ar resulted in partial densification of the composite bodies, and subsequent annealing at 850°C in a moist O2 atmosphere yielded a composite of Co-Cr-Mo alloy with phase-pure HA. The overall dimensional changes upon transformation of Ca+beta-Ca2P2O7+CO-Cr-Mo precursors into HA/Co-Cr-Mo composite were relatively small. In this thesis, the phase and microstructural evolution at various stages of transformation to monolithic HA and to HA/Co-Cr-Mo alloy composites are discussed. Planar reaction couples and powder compacts of CaO-TCP were prepared to study the kinetics for HA formation from CaO+TCP. Pt strips were used in the planar reaction couples as inert markers. These reaction couples were heated at 1150°C for various times in moist O2. The results of powder compact analyses fits Carter's model, which indicated that the rate of HA conversion from CaO and TCP is limited by solid state diffusion of Ca 2+ and/or OH- through the HA layer.

Saw, Eaden

293

Ha Shengcheng Hajia kun Hawandija yiusanni  

E-print Network

line). B: Kanzhuo’s father was his eldest son and was adopted by the eldest great-great-granduncle (i.e. Ha Nangsuo’s eldest brother)? A: Yeah, Shenghui’s father was adopted by the second great-great-granduncle (i.e., Ha Nangsuo’s second eldest brother... , aadee, ni naomenzi aadeesa da zhao jisui dai? A: Nao liangsui dazhe lia. Ta fu gou zi a, nizi Maotuo aadee fu yang zi a. Nao tasa shi’ai sui ma shisansui dazhe lia. Nizi aadee zili haiyou Jingdi’s ama lia zai. B: Shi’ai ma shisan lia? Nani fu sa zi a...

Ha, Mingzong

2009-09-23

294

Catalytic oxidiative decomposition of dimethyl methylphosphonate over Cu-substituted hydroxyapatite  

SciTech Connect

The oxidative decomposition of dimethyl methylphosphonate (DMMP) has been studied over Cu-substituted hydroxyapatite catalysts in a flow reactor in the temperature range 373-773 K. by substitution of a portion of the Ca[sup 2+] by Cu[sup 2+] in the hydroxyapatite lattice, the catalytic activity was markedly increased. The composition Cu[sub 2]Ca[sub 8](PO[sub 4])[sub 6](OH)[sub 2], herein called Cu2-HA, had the highest activity among these catalysts. All the catalysts showed 100% conversion at the beginning of the reaction, but became deactivated after a period of time. Only CO[sub 2] and H[sub 2]O were produced during the [open quotes]protection period[close quotes] of the 100% conversion. With deactivation, CO[sub 2] formation decreased and methanol and dimethyl ether appeared as products. A phosphorus-containing product was not detected in the gas phase. Some condensate of phosphoric acid appeared in the outlet of the reactor after deactivation. Several analytical methods revealed that carbonaceous compounds did not remain on the surface after 773-K oxidative regeneration, but the phosphorus compounds that had accumulated during the reaction were; not eliminated. The catalytic activity of Cu-substituted hydroxyapatite was compared to that of conventional supported Pt catalysts. This study suggested that easily made and cheap Cu-substituted hydroxyapatite catalysts could be used as successful alternatives to conventional adsorbents and catalytic systems based on supported noble metals devised for protection against nerve gases in warfare. 35 refs., 10 figs., 2 tabs.

Lee, Kwan Young (Univ. of Tokyo (Japan)); Houalla, M.; Hercules, D.M.; Hall, W.K. (Univ. of Pittsburgh, PA (United States))

1994-01-01

295

Acute and subacute toxicity in vivo of thermal-sprayed silver containing hydroxyapatite coating in rat tibia.  

PubMed

To reduce the incidence of implant-associated infection, we previously developed a novel coating technology using hydroxyapatite (HA) containing silver (Ag). This study examined in vivo acute and subacute toxicity associated with the Ag-HA coating in rat tibiae. Ten-week-old rats received implantation of HA-, 2% Ag-HA-, or 50% Ag-HA-coated titanium rods. Concentrations of silver in serum, brain, liver, kidneys, and spleen were measured in the acute phase (2-4 days after treatment) and subacute phase (4-12 weeks after treatment). Biochemical and histological examinations of those organs were also performed. Mean serum silver concentration peaked in the acute phase and then gradually decreased. Mean silver concentrations in all examined organs from the 2% Ag-HA coating groups showed no significant differences compared with the HA coating group. No significant differences in mean levels of glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, creatinine, or blood urea nitrogen were seen between the three groups and controls. Histological examinations of all organs revealed no abnormal pathologic findings. No acute or subacute toxicity was seen in vivo for 2% Ag-HA coating or HA coating. Ag-HA coatings on implants may represent biologically safe antibacterial biomaterials and may be of value for reducing surgical-site infections related to implantation. PMID:24779019

Tsukamoto, Masatsugu; Miyamoto, Hiroshi; Ando, Yoshiki; Noda, Iwao; Eto, Shuichi; Akiyama, Takayuki; Yonekura, Yutaka; Sonohata, Motoki; Mawatari, Masaaki

2014-01-01

296

Beta dose distribution for randomly packed microspheres  

E-print Network

of radiation dose distribution when utilizing this technique. This study focuses on random packing of microspheres and seeks to determine dose distributions for specific cases. The Monte Carlo Neutral Particle code (MCNP) developed by Los Alamos National...

Urashkin, Alexander

2007-04-25

297

Organic aerogel microspheres and fabrication method therefor  

DOEpatents

Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

Mayer, Steven T. (San Leandro, CA); Kong, Fung-Ming (Pleasanton, CA); Pekala, Richard W. (Pleasant Hill, CA); Kaschmitter, James L. (Pleasanton, CA)

1996-01-01

298

Development and evaluation of controlled-release diclofenac microspheres and tabletted microspheres.  

PubMed

Diclofenac wax microspheres were prepared using the congealable dispersephase encapsulation method. Emulsifiers, glyceryl monostearate (GMS) and stearic acid, were added to improve the efficiency of emulsification. Microspheres containing either of the emulsifiers or both showed a high drug content (80-90%) and the particle size distribution was log-normal compared with microspheres without the emulsifiers. Increase in GMS concentration decreased the drug release and, in contrast, stearic acid appeared to channel the drug from the wax matrix. The addition of both emulsifiers at different concentrations modified drug release. Increase in dispersant (PVP) concentration, and decrease in microsphere size accelerated the rate of drug release. Higuchi/Baker Londsdale spherical matrix dissolution kinetics was followed. Disintegrating tableted microspheres were prepared with Avicel and Explotab. With the increase in compression pressure the crushing force and disintegrating time increased, but the thickness decreased, and the dissolution profile did not appear to be affected. Slightly faster release was noticed with tableted microspheres compared with that of uncompressed microspheres. Tablets containing 40 and 60% microsphere loadings had disintegration times of 5.12 +/- 0.63 and 57.73 +/- 3.53 min, respectively. In contrast, tablet formulation containing 80% microsphere load had a significant increase in disintegration time (130.83 +/- 4.26 min). The dissolution from this formulation also showed a lag time of 30 min in contrast with the other two formulations, which showed no lag time. Increased microsphere size from 215 to 630 microns had no effect on tableting properties (such as hardness and thickness); and only very little effect on dissolution. The microspheres appeared deformed but intact irrespective of compression pressures on scanning electron micrographs. PMID:7931945

Vilivalam, V D; Adeyeye, C M

1994-01-01

299

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon  

PubMed Central

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtas, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-01-01

300

Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon  

NASA Astrophysics Data System (ADS)

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojta?, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

2013-07-01

301

One- and three-dimensional growth of hydroxyapatite nanowires during sol-gel-hydrothermal synthesis.  

PubMed

Nanoscale hydroxyapatite (HA) is an optimal candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. In this study, micro- and nanoscale HA particles with rod- and wirelike morphology were synthesized by a novel sol-gel-hydrothermal process. Sol-gel chemistry was used to produce a dry gel containing amorphous calcium phosphate (ACP), which was used as a precursor material in a hydrothermal process. The sol-gel-hydrothermal products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine particle morphology, crystal structure, and the presence of chemical functional groups. A pure HA crystal was synthesized, which underwent both one- and three-dimensional growth, resulting in tunable microrod and nanorod, and wire morphologies. The effects of solution pH and reaction time on particle diameter and length were assessed. Particle diameter ranged from 25 to 800 nm and decreased with an increase in solution pH, whereas both particle length and diameter increased as the hydrothermal process was prolonged. Nanowire HA powders (10-50 wt %) were mixed with poly(?-caprolactone) (PCL) to produce PCL/HA composites. Fracture surfaces of PCL/HA composites showed a well-dispersed and homogeneous distribution of HA nanowires within the PCL matrix. Mechanical testing revealed a significant (p < 0.05) increase in the Young's and compressive moduli of PCL/HA composites compared to PCL alone, with 50 wt % HA producing a 3-fold increase in Young's modulus from 193 to 665 MPa and 2-fold increase in compressive modulus from 230 to 487 MPa. These HA nanowires can be used to reinforce polymer composites and are excellent biomaterials for tissue engineering of bone. PMID:22296410

Costa, Daniel O; Dixon, S Jeffrey; Rizkalla, Amin S

2012-03-01

302

Nasal delivery of insulin using chitosan microspheres.  

PubMed

Nasal delivery of insulin is an alternative route for administration of this drug. The objective of this study was preparation of chitosan microspheres for insulin nasal delivery. After preparation of insulin chitosan microspheres by emulsification-cross linking process, the effect of chitosan quantity (200-400mg), cross-linker type (ascorbic acid or ascorbyl palmitate) and amount (70-140 mg) were studied on the morphology, particle size, loading efficiency, flow and release of insulin from the microspheres by a factorial design. Optimized formulation was administered nasally in four groups of diabetic rats and their serum insulin levels were analysed by the insulin enzyme immunoassay kit and the serum glucose by the glucose oxidase kits. Insulin loading in microspheres was between 4.7-6.4% w/w, preparation efficiency more than 65% and mean particle size was 20-45 microm. In most cases, drug released followed a Higuchi model. Ascorbic acid caused an increase in stability, particle size and T50%, while decreased the loading efficiency and production efficiency. Increasing the chitosan content, increased particle size, flow and insulin release rate form the microspheres. The increase of cross-linking percentage decreased the flow and size of the microspheres while increase of cross-linking percentage promoted the stability and decreased DE8% of insulin. Microspheres containing 400mg of chitosan and 70mg ascorbyl palmitate caused a 67% reduction of blood glucose compared to i.v. route and absolute bioavaliability of insulin was 44%. The results showed that chitosan microspheres of insulin are absorbable from nasal route. PMID:15799226

Varshosaz, J; Sadrai, H; Alinagari, R

2004-11-01

303

Carbon microsphere-filled Pyrrone foams.  

NASA Technical Reports Server (NTRS)

Syntactic foam formulations were prepared from mixtures of Pyrrone prepolymers and hollow carbon microspheres. Very low curing shrinkages were obtained for high volume loadings of microspheres. The resulting syntactic foams were found to be remarkably stable over a wide range in temperature. A technique was developed for the emplacement of these foam formulations in polyimide-fiberglass, titanium alloy and stainless steel honeycomb without sacrificing low curing shrinkage or thermal stability.

Kimmel, B. G.

1973-01-01

304

In vitro testing of plasma-sprayed hydroxyapatite coatings  

Microsoft Academic Search

Hydroxyapatite-coated coupons were tested in various physiological media. Immersion in Ringer's solution showed that heat-treated coatings displayed a weight gain but the assprayed coatings underwent a weight loss. Dissolution of the coating was measured by weighing the specimen before and after ageing. Immersion of hydroxyapatite coatings showed the appearance of small spheres that were identified by X-ray diffraction as hydroxyapatite.

K. A. Gross; C. C. Berndt

1994-01-01

305

Effects of Recombinant Amelogenin on Hydroxyapatite Formation In Vitro  

Microsoft Academic Search

.   To determine the role of amelogenin in the mineralization of dental enamel, the effects of the recombinant mouse amelogenin\\u000a rM179 on in vitro hydroxyapatite formation have been studied. In a steady-state agarose gel assay for hydroxyapatite nucleation, rM179 lacked\\u000a significant activity at concentrations up to 300 ?g\\/ml. In an autotitration assay for inhibition of de novo hydroxyapatite formation, rM179

G. K. Hunter; H. A. Curtis; M. D. Grynpas; J. P. Simmer; A. G. Fincham

1999-01-01

306

X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium  

SciTech Connect

The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

Drummond, J.L.; Steinberg, A.D. [Univ. of Illinois, Chicago, IL (United States); Krauss, A.R. [Argonne National Lab., IL (United States)] [and others

1997-08-01

307

High temperature in-situ XRD of plasma sprayed HA coatings.  

PubMed

The control of phase transformations in plasma sprayed hydroxyapatite (HA) coatings are critical to the clinical performance of the material. This paper reports the use of high temperature X-ray diffraction (HT-XRD) to study, in-situ, the phase transformations occurring in plasma sprayed HA coatings. The coatings were prepared using different spray power levels (net plasma power of 12 and 15 kW) and different starting powder size ranges (20-45; 45-75 microm). The temperature range employed was room temperature (approximately 26 degrees C) to 900 degrees C in normal atmosphere and pressure. High temperature differential scanning calorimetry (DSC) was also employed to investigate and determine the precise onset temperature of phase transformations during the recrystallization process. Results showed that actual onset of thermal degradation in the coating into other metastable phases like TTCP, beta-TCP and CaO occurred at 638 degrees C. The aforementioned phase transitions were independent of the selected spraying parameters. The degree of melting and thermal dissociation of HA actually determines the amount of calcium phosphate phases that are formed. A high power level of 15 kW produced a greater degree of melting, resulting in more CaO, TTCP and beta-TCP being formed as a result. PMID:11762329

Kweh, S W K; Khor, K A; Cheang, P

2002-01-01

308

Demonstration of Microsphere Insulation in Cryogenic Vessels  

NASA Astrophysics Data System (ADS)

While microspheres have been recognized as a legitimate insulation material for decades, actual use in full-scale cryogenic storage tanks has not been demonstrated until now. The performance and life-cycle-cost advantages previously predicted have now been proven. Most bulk cryogenic storage tanks are insulated with either multilayer insulation (MLI) or perlite. Microsphere insulation, consisting of hollow glass bubbles, combines in a single material the desirable properties that other insulations only have individually. The material has high crush strength, low density, is noncombustible, and performs well in soft vacuum. These properties were proven during recent field testing of two 22,700-L (6,000-gallon) liquid nitrogen tanks, one insulated with microsphere insulation and the other with perlite. Normal evaporation rates (NER) for both tanks were monitored with precision test equipment and insulation levels within the tanks were observed through view ports as an indication of insulation compaction. Specific industrial applications were evaluated based on the test results and beneficial properties of microsphere insulation. Over-the-road trailers previously insulated with perlite will benefit not only from the reduced heat leak, but also the reduced mass of microsphere insulation. Economic assessments for microsphere-insulated cryogenic vessels including life-cycle cost are also presented.

Baumgartner, R. G.; Myers, E. A.; Fesmire, J. E.; Morris, D. L.; Sokalski, E. R.

2006-04-01

309

Affinity separation with polyaldehyde microsphere beads.  

PubMed

Agarose polyaldehyde microsphere beads were prepared by encapsulating polyaldehyde microspheres of various diameters, e.g., polyacrolein or polyglutaraldehyde microspheres, within agarose beads. Amino ligands such as proteins or drugs can be bound covalently to the beads in a single step at physiological pH. The binding capacity of the beads towards various amino ligands is inversely related to the diameter of the microspheres encapsulated in the agarose matrix. Different reagents, e.g., bovine serum albumin, ethanolamine and hydroxylamine, were studied as blocking reagents of the free aldehyde groups. Blocking the remaining aldehyde groups after coupling the amino ligands to the beads is essential for increasing or retaining the reactivity of the ligands conjugated to the beads. Among the reagent studied, hydroxylamine was found to be the most suitable blocking reagent of the free aldehyde groups of beads conjugated with proteins. The extent of leakage of amino ligands bound to the agarose-polyaldehyde microsphere beads was studied as a function of the pH of aqueous solutions of the beads. At physiological pH the leakage was negligible. At acid pH, leakage of ligands containing several primary amine groups, e.g., proteins, was insignificant. However, significant leakage was detected for ligands containing a single amino group. The leakage of proteins bound to the agarose-polyaldehyde microsphere beads was found to be much less than the leakage of the same proteins bound to agarose beads through the cyanogen bromide activation method. PMID:2738121

Margel, S

1989-01-13

310

Better early osteogenesis of electroconductive hydroxyapatite-calcium titanate composites in a rabbit animal model.  

PubMed

In view of the fact that bone healing can be enhanced due to external electric field application, it is important to assess the influence of the implant conductivity on the bone regeneration in vivo. To address this issue, this study reports the in vivo biocompatibility property of multistage spark plasma sintered hydroxyapatite (HA)-80 wt % calcium titanate (CaTiO3 ) composites and monolithic HA, which have widely different conductivity property (14 orders of magnitude difference). The ability of bone regeneration was assessed by implantation in cylindrical femoral bone defects of rabbit animal model for varying time period of 1, 4, and 12 weeks. The overall assessment of the histology results suggests that the progressive healing of bone defects around HA-80 wt % CaTiO3 is associated with a better efficacy with respect to (w.r.t) early stage neobone formation, which is histomorphometrically around 140% higher than monolithic HA. Overall, this study demonstrates that the in vivo biocompatibility property of HA-80 wt % CaTiO3 with respect to local effects after 12 weeks of implantation is not compromised both qualitatively and quantitatively, and a comparison with control implant (HA) points toward the critical role of electrical conductivity on better early stage bone regeneration. PMID:23589392

Mallik, Prafulla Kumar; Basu, Bikramjit

2014-03-01

311

Dynamics of bone marrow pressure with tapping of titanium and hydroxyapatite implants in rabbits.  

PubMed

The purpose of the present study was to evaluate the difference in stress transfer between titanium (Ti) and hydroxyapatite (HA) by the measurement of bone marrow pressure using a catheter pressure transducer. Ti and HA implants were inserted in the tibiae of rabbits. A hole of 1 mm in diameter was drilled in the bone and a fine catheter pressure transducer was placed in the bone marrow through a tube. The top of the abutment was vertically tapped with an impulse hammer, and the acceleration signal from the hammer and pressure signal from the catheter pressure transducer were examined. The time of contact (impulse duration) recorded in the impulse with Ti and HA was 166+/-17 micro sec and 164 +/- 17 micro sec, respectively. Maximum bone marrow pressure (BMP) with Ti and HA was 54.2 +/- 32.6 and 47.5 +/- 10.0 mmHg, respectively. Variation of the BMP with Ti was significantly larger than that with HA (P < 0.05). A negative correlation coefficient between impulse duration and BMP was found. The results of the present study suggest that the stress transfer is different between Ti and HA implants using dynamics of the bone marrow pressure. PMID:11952743

Tomotake, Yoritoki; Ichikawa, Tetsuo; Kanitani, Hideo; Nakao, Masahide; Kitaoka, Naoki

2002-04-01

312

Mechanisms of enhanced osteoblast gene expression in the presence of hydroxyapatite coated iron oxide magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) coated iron oxide (Fe3O4) magnetic nanoparticles have been shown to enhance osteoblast (bone forming cells) proliferation and osteoblast differentiation into calcium depositing cells (through increased secretion of alkaline phosphatase, collagen and calcium deposition) compared to control samples without nanoparticles. Such nanoparticles are, thus, very promising for numerous orthopedic applications including magnetically directed osteoporosis treatment. The objective of the current study was to elucidate the mechanisms of the aforementioned improved osteoblast responses in the presence of HA coated Fe3O4 nanoparticles. Results demonstrated large amounts of fibronectin (a protein known to increase osteoblast functions) adsorption on HA coated Fe3O4 nanoparticles. Specifically, fibronectin adsorption almost doubled when HA coated Fe3O4 nanoparticle concentrations increased from 12.5 to 100 ?g ml-1, and from 12.5 to 200 ?g ml-1, a four fold increase was observed. Results also showed greater osteoblast gene regulation (specifically, osteocalcin, type I collagen and cbfa-1) in the presence of HA coated Fe3O4 nanoparticles. Collectively, these results provide a mechanism for the observed enhanced osteoblast functions in the presence of HA coated iron oxide nanoparticles, allowing their further investigation for a number of orthopedic applications.

Tran, Nhiem; Hall, Douglas; Webster, Thomas J.

2012-11-01

313

Polylactide nanofibers with hydroxyapatite as growth substrates for osteoblast-like cells.  

PubMed

Various types of nanofibers are increasingly used in tissue engineering, mainly for their ability to mimic the architecture of tissue at the nanoscale. We evaluated the adhesion, growth, viability, and differentiation of human osteoblast-like MG 63 cells on polylactide (PLA) nanofibers prepared by needle-less electrospinning and loaded with 5 or 15 wt % of hydroxyapatite (HA) nanoparticles. On day 7 after seeding, the cell number was the highest on samples with 15 wt % of HA. This result was confirmed by the XTT test, especially after dynamic cultivation, when the number of metabolically active cells on these samples was even higher than on control polystyrene. Staining with a live/dead kit showed that the viability of cells on all nanofibrous scaffolds was very high and comparable to that on control polystyrene dishes. An enzyme-linked immunosorbent assay revealed that the concentration of osteocalcin was also higher in cells on samples with 15 wt % of HA. There was no immune activation of cells (measured by production of TNF-alpha), associated with the incorporation of HA. Moreover, the addition of HA suppressed the creep behavior of the scaffolds in their dry state. Thus, nanofibrous PLA scaffolds have potential for bone tissue engineering, particularly those with 15 wt % of HA. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3918-3930, 2014. PMID:24375970

Novotna, Katarina; Zajdlova, Martina; Suchy, Tomas; Hadraba, Daniel; Lopot, Frantisek; Zaloudkova, Margit; Douglas, Timothy E L; Munzarova, Marcela; Juklickova, Martina; Stranska, Denisa; Kubies, Dana; Schaubroeck, David; Wille, Sebastian; Balcaen, Lieve; Jarosova, Marketa; Kozak, Halyna; Kromka, Alexander; Svindrych, Zdenek; Lisa, Vera; Balik, Karel; Bacakova, Lucie

2014-11-01

314

A novel route for synthesis of nanocrystalline hydroxyapatite from eggshell waste.  

PubMed

The eggshell waste has been value engineered to a nanocrystalline hydroxyapatite (HA) by microwave processing. To highlight the advantages of eggshell as calcium precursor in the synthesis of HA (OHA), synthetic calcium hydroxide was also used to form HA (SHA) following similar procedure and were compared with a commercially available pure HA (CHA). All the HAs were characterized by X-ray powder diffraction (XRD) method, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and specific surface area measurements. Nanocrystalline nature of OHA is revealed through characteristic broad peaks in XRD patterns, platelets of length 33-50 nm and width 8-14 nm in TEM micrograph and size calculations from specific surface area measurements. FT-IR spectra showed characteristic bands of HA and additionally peaks of carbonate ions. The cell parameter calculations suggest the formation of carbonated HA of B-type. The OHA exhibits superior sinterability in terms of hardness and density than both SHA and CHA may be due to larger surface area of its spherulite structure. The in vitro dissolution study shows longer stability in phosphate buffer and cell culture test using osteoblast cells establishes biocompatibility of OHA. PMID:17483877

Siva Rama Krishna, D; Siddharthan, A; Seshadri, S K; Sampath Kumar, T S

2007-09-01

315

Nano-Ag-loaded hydroxyapatite coatings on titanium surfaces by electrochemical deposition  

PubMed Central

Hydroxyapatite (HA) coatings on titanium (Ti) substrates have attracted much attention owing to the combination of good mechanical properties of Ti and superior biocompatibility of HA. Incorporating silver (Ag) into HA coatings is an effective method to impart the coatings with antibacterial properties. However, the uniform distribution of Ag is still a challenge and Ag particles in the coatings are easy to agglomerate, which in turn affects the applications of the coatings. In this study, we employed pulsed electrochemical deposition to co-deposit HA and Ag simultaneously, which realized the uniform distribution of Ag particles in the coatings. This method was based on the use of a well-designed electrolyte containing Ag ions, calcium ions and l-cysteine, in which cysteine acted as the coordination agent to stabilize Ag ions. The antibacterial and cell culture tests were used to evaluate the antibacterial properties and biocompatibility of HA/Ag composite coatings, respectively. The results indicated the as-prepared coatings had good antibacterial properties and biocompatibility. However, an appropriate silver content should be chosen to balance the biocompatibility and antibacterial properties. Heat treatments promoted the adhesive strength and enhanced the biocompatibility without sacrificing the antibacterial properties of the HA/Ag coatings. In summary, this study provided an alternative method to prepare bioactive surfaces with bactericidal ability for biomedical devices. PMID:20880853

Lu, Xiong; Zhang, Bailin; Wang, Yingbo; Zhou, Xianli; Weng, Jie; Qu, Shuxin; Feng, Bo; Watari, Fumio; Ding, Yonghui; Leng, Yang

2011-01-01

316

Drug loading and release of Tobramycin from hydroxyapatite coated fixation pins.  

PubMed

This paper evaluates the loading and release properties of Tobramycin incorporated by adsorptive loading from a solution into plasma sprayed and biomimetically coated Hydroxyapatite (HA) fixation pins. The aim of this study is to contribute towards designing a functional implant surface offering local release of the antibiotic agent to prevent post-surgical infections. Cathodic arc deposition is used to coat stainless steel fixation pins with a bioactive, anatase phase dominated, TiO? coating onto which a HA layer is grown biomimetically. The loading and release properties are evaluated by studying the subsequent release of Tobramycin using high performance liquid chromatography and correlated to the differences in HA coating microstructure and the physical conditions under loading. The results from these studies show that a dual loading strategy consisting of a solution temperature of 90 °C and a pressure of 6 bar during a loading time of 5 min release a sufficient amount of Tobramycin to guarantee the inhibition of Staphylococcus aureus up to 2 days for plasma sprayed HA coatings and for 8 days for biomimetic coatings. The present study emphasizes the advantages of the nanoporous structure of biomimetically deposited HA over the more dense structure of plasma sprayed HA coatings in terms of antibiotic incorporation and subsequent sustained release and provides a valuable outline for the design of implant surfaces aiming for a fast-loading and controlled, local drug administration. PMID:23779156

Lilja, Mirjam; Sörensen, Jan Henrik; Brohede, Ulrika; Astrand, Maria; Procter, Philip; Arnoldi, Jörg; Steckel, Hartwig; Strømme, Maria

2013-09-01

317

Nonlinear elasticity of microsphere heaps  

NASA Astrophysics Data System (ADS)

Thermal fluctuations, geometric exclusion, and external driving all govern the mechanical response of dense particulate suspensions. Here, we measure the stress-strain response of quasi-two-dimensional flow-stabilized microsphere heaps in a regime in which all three effects are present using a microfluidic device. We observe that the elastic modulus and the mean interparticle separation of the heaps are tunable via the confining stress provided by the fluid flow. Furthermore, the measured stress-strain curves exhibit a universal nonlinear shape, which can be predicted from a thermal van der Waals equation of state with excluded volume. This analysis indicates that many-body interactions contribute a significant fraction of the stress supported by the heap.

Ortiz, Carlos P.; Daniels, Karen E.; Riehn, Robert

2014-08-01

318

Fabrication of Adipose-Derived Mesenchymal Stem Cell Aggregates using Biodegradable Porous Microspheres for Injectable Adipose Tissue Regeneration.  

PubMed

Injectable mesenchymal stem cell aggregates were formed using hyaluronic acid (HA)-immobilized porous biodegradable microspheres for adipose tissue regeneration. Adipose tissue-derived mesenchymal stem cells (AMSCs) were aggregated in a controlled manner and differentiated into adipocytes by cultivating in a stirred suspension bioreactor. The resultant cellular aggregates were approx. 1700 mum in diameter and exhibited fully differentiated adipocytes, as shown by immunocytochemistry and RT-PCR. The cultured aggregates could be smoothly injected into the subcutaneous region of mice through a syringe needle due to their soft elasticity and deformability. The in vivo regenerated adipose tissue maintained a proper dimension and shape, showing natural adipose tissue characteristics, as demonstrated by various histological staining procedures. HA-immobilized microspheres significantly enhanced cell differentiation during 3D cultivation, and tissue regeneration when implanted in vivo, compared to unmodified porous microspheres. This study showed that AMSC cellular aggregates prepared by using porous microspheres could be delivered in an injectable manner into the body and could have great therapeutic potential for soft tissue augmentation and reconstruction. PMID:20546678

Chung, Hyun Jung; Jung, Jin Sup; Park, Tae Gwan

2010-06-11

319

Transformation of 3DP gypsum model to HA by treating in ammonium phosphate solution.  

PubMed

Three-dimensional printing (3DP) is a CAD/CAM built-up using ink-jet printing technique. Commercially available 3DP system can form only gypsum model and not for bioceramics. On the other hand, transformation of hardened gypsum into hydroxyapatite (HA) by treatment in ammonium phosphate solution was found lately. In the present study, transformation of the 3DP gypsum block to HA was attempted. However, the fabricated 3DP block was soluble in water. To insolubilize, it was heated at 300 degrees C for 10 min, and then, gypsum was transformed to calcium sulfate hemihydrate, CaSO(4) x 0.5H(2)O. The 3D block was immersed in 1M (NH(4))(3)PO(4) x 3H(2)O solution at 80 degrees C for 1-24 h, and the transformation into HA within 4 h was ascertained. A heat-treated plaster of Paris (POP) block was also investigated for comparison. The unheated POP block consisting of gypsum dihydrate took 24 h to complete the transformation, while the heat-treated POP consisting calcium sulfate hemihydrate promoted the transformation into HA; but the transformed thickness in the block was less than the 3DP block. This is probably due to higher solubility of the hemihydrate than gypsum dihydrate. Accelerated transformation of the 3DP block was also caused by its porous structure, which enabled an easy penetration of the phosphate solution. With the present method, it is possible to transform the fabricated gypsum by 3D printing that is adaptive to the osseous defect into HA prostheses or scaffold. PMID:16838351

Lowmunkong, Rungnapa; Sohmura, Taiji; Takahashi, Junzo; Suzuki, Yumiko; Matsuya, Shigeki; Ishikawa, Kunio

2007-02-01

320

Recent Developments in Suspension Plasma Sprayed Titanium Oxide and Hydroxyapatite Coatings  

NASA Astrophysics Data System (ADS)

The paper aims at reviewing of the recent studies related to the development of suspension plasma sprayed TiO2 and Ca5(PO4)3OH (hydroxyapatite, HA) coatings as well as their multilayer composites obtained onto stainless steel, titanium and aluminum substrates. The total thickness of the coatings was in the range 10 to 150 ?m. The suspensions on the base of distilled water, ethanol and their mixtures were formulated with the use of fine commercial TiO2 pigment crystallized as rutile and HA milled from commercial spray-dried powder or synthesized from calcium nitrate and ammonium phosphate in an optimized reaction. The powder was crystallized as hydroxyapatite. Pneumatic and peristaltic pump liquid feeders were applied. The injection of suspension to the plasma jet was studied carefully with the use of an atomizer injector or a continuous stream one. The injectors were placed outside or inside of the anode-nozzle of the SG-100 plasma torch. The stream of liquid was tested under angle right or slightly backwards with regard to the torch axis. The sprayed deposits were submitted to the phase analysis by the use of x-ray diffraction. The content of anatase and rutile was calculated in the titanium oxide deposits as well as the content of the decomposition phases in the hydroxyapatite ones. The micro-Raman spectroscopy was used to visualize the area of appearance of some phases. Scratch test enabled to characterize the adhesion of the deposits, their microhardness and friction coefficient. The electric properties including electron emission, impedance spectroscopy, and dielectric properties of some coatings were equally tested.

Jaworski, R.; Pawlowski, L.; Pierlot, C.; Roudet, F.; Kozerski, S.; Petit, F.

2010-01-01

321

Studies on sintering process of synthetic hydroxyapatite.  

PubMed

In this study the effect of sintering process in different temperatures on microstructure and morphological properties of sintered hydroxyapatite (HAp) was investigated. HAp powder was prepared by wet precipitation method from following reagents: Ca(OH)2 + H3PO4 in an alkaline conditions. Thermal analysis (TA), X-Ray diffraction method (XRD), FT-IR spectrometry (FT-IR) and scanning electron microscopy (SEM) were used to elaborate the phase composition and properties of sintered HAp samples and raw HAp powder as well. The total and apparent density and total porosity of sintered compacts, shrinkage and weight loss during the sintering were also measured. The results show that there is a difference in sintering behavior of synthetic hydroxyapatites depending on sintering temperature. The main differences refer to the loss of mass, shrinkage, changes in porosity and density of the investigated materials. PMID:24432345

Malina, Dagmara; Biernat, Kamila; Sobczak-Kupiec, Agnieszka

2013-01-01

322

Modeling scattered intensity from microspheres in evanescent field  

E-print Network

. These modes may be used as a refractometric biosensor with high sensitivity to local refractive index changes on the surface of the microsphere. This research involves modeling scattered intensity distributions for polydispersed collections of microspheres...

Shah, Suhani Kiran

2009-05-15

323

Modeling scattered intensity from microspheres in evanescent field  

E-print Network

. These modes may be used as a refractometric biosensor with high sensitivity to local refractive index changes on the surface of the microsphere. This research involves modeling scattered intensity distributions for polydispersed collections of microspheres...

Shah, Suhani Kiran

2008-10-10

324

Hydroxyapatite deposition disease of the joint  

Microsoft Academic Search

Basic calcium phosphate (BCP) crystals include partially carbonate-substituted hydroxyapatite, octacalcium phosphate, and\\u000a tricalcium phosphate. They may form deposits, which are frequently asymptomatic but may give rise to a number of clinical\\u000a syndromes including calcific periarthritis, Milwaukee shoulder syndrome, and osteoarthritis, in and around joints. Recent\\u000a data suggest that magnesium whitlockite, another form of BCP, may play a pathologic role in

Eamonn S. Molloy; Geraldine M. McCarthy

2003-01-01

325

Selective laser sintering fabrication of nano-hydroxyapatite/poly-?-caprolactone scaffolds for bone tissue engineering applications  

PubMed Central

The regeneration of functional tissue in osseous defects is a formidable challenge in orthopedic surgery. In the present study, a novel biomimetic composite scaffold, here called nano-hydroxyapatite (HA)/poly-?-caprolactone (PCL) was fabricated using a selective laser sintering technique. The macrostructure, morphology, and mechanical strength of the scaffolds were characterized. Scanning electronic microscopy (SEM) showed that the nano-HA/PCL scaffolds exhibited predesigned, well-ordered macropores and interconnected micropores. The scaffolds have a range of porosity from 78.54% to 70.31%, and a corresponding compressive strength of 1.38 MPa to 3.17 MPa. Human bone marrow stromal cells were seeded onto the nano-HA/PCL or PCL scaffolds and cultured for 28 days in vitro. As indicated by the level of cell attachment and proliferation, the nano-HA/PCL showed excellent biocompatibility, comparable to that of PCL scaffolds. The hydrophilicity, mineralization, alkaline phosphatase activity, and Alizarin Red S staining indicated that the nano-HA/PCL scaffolds are more bioactive than the PCL scaffolds in vitro. Measurements of recombinant human bone morphogenetic protein-2 (rhBMP-2) release kinetics showed that after nano-HA was added, the material increased the rate of rhBMP-2 release. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both nano-HA/PCL scaffolds and PCL scaffolds were implanted in rabbit femur defects for 3, 6, and 9 weeks. The wounds were studied radiographically and histologically. The in vivo results showed that both nano-HA/PCL composite scaffolds and PCL scaffolds exhibited good biocompatibility. However, the nano-HA/PCL scaffolds enhanced the efficiency of new bone formation more than PCL scaffolds and fulfilled all the basic requirements of bone tissue engineering scaffolds. Thus, they show large potential for use in orthopedic and reconstructive surgery. PMID:24204147

Xia, Yan; Zhou, Panyu; Cheng, Xiaosong; Xie, Yang; Liang, Chong; Li, Chao; Xu, Shuogui

2013-01-01

326

Molecular dynamics simulations for the examination of mechanical properties of hydroxyapatite/ poly ?-n-butyl cyanoacrylate under additive manufacturing.  

PubMed

Molecular dynamics (MD) simulations emerged to be a helpful tool in the field of material science. In rapid prototyping artificial bone scaffolds process, the binder spraying volume and mechanism are very important for bone scaffolds mechanical properties. In this study, we applied MD simulations to investigating the binding energy of ?-n-butyl cyanoacrylate (NBCA) on Hydroxyapatite (HA) crystallographic planes (001, 100 and 110), and to calculating and analyzing the mechanical properties and radial distribution function of the HA(110)/NBCA mixed system. The simulation results suggested that HA (110) has the highest binding energy with NBCA owing to the high planar atom density, and the mechanical properties of HA(110)/NBCA mixed system is stronger than pure HA system. Therefore, the multi-grade strength bone scaffold could be fabricated through spraying various volume NBCA binders during 3D printing process. By calculating the radial distribution function of HA(110)/NBCA, the essence of the interface interaction were successfully elucidated. The forming situation parameters can be referred to calculation results. There exists a strong interaction between HA crystallographic plane (110) and NBCA, it is mainly derived from the hydrogen bonds between O atoms which connect with C atoms of NBCA and H atoms in HA crystal. Furthermore, a strong adsorption effect can be demonstrated between HA and NBCA. PMID:24211969

Wang, Yanen; Wei, Qinghua; Pan, Feilong; Yang, Mingming; Wei, Shengmin

2014-01-01

327

Physical and biological evaluations of sintered hydroxyapatite/silicone composite with covalent bonding for a percutaneous implant material.  

PubMed

A composite (HA/silicone) of hydroxyapatite (HA) microparticles with an average diameter of 2.0 micro m covalently linked to a silicone substrate has been developed, and its physical and biological properties as a percutaneous soft-tissue-compatible material have been evaluated. In tensile property measurement, samples of HA/silicone and the original silicone were similar in tensile strength, ca. 7.8 MPa, and elongation at break, ca. 570%. It was found that chemical surface modification with HA particles presented no mechanical disadvantage. In an adhesive-tape peeling test, scanning electron microscopic (SEM) observation showed that HA particles coupled directly to the substrate were not removed. HA particles may bond strongly with the substrate. In human periodontal ligament fibroblast attachment and proliferation experiments, the number of cells attached to HA/silicone was 14 times greater than that attached to the original silicone after 24 h of incubation. The value on HA/silicone was ca. 80% versus that on a tissue-culture plastic used as a positive control. After 72 h of incubation, the number of cells grown on HA/silicone increased to the level of the positive control. In observation of fluorescence microscopy stained by Hoechst 33342, cells appeared to tightly adhere to HA particles coupled to the silicone sheet due to intact nuclear morphology. Observation of cells by fluorescence dye with rhodamin phalloidin showed an extensive F-actin cytoskeleton on HA/silicone. In a 4-week animal implant test, force required to pull out the HA/silicone sheet was 15 times that of the original silicone. HA-particle coating on silicone with covalent linkage gave the inert surface bioactivity. The HA composite thus effectively prevents germ infection percutaneously. PMID:12687713

Furuzono, Tsutomu; Wang, Pao-Li; Korematsu, Arata; Miyazaki, Kozo; Oido-Mori, Mari; Kowashi, Yusuke; Ohura, Kiyoshi; Tanaka, Junzo; Kishida, Akio

2003-05-15

328

In vitro and in vivo bioactivity of CoBlast hydroxyapatite coating and the effect of impaction on its osteoconductivity.  

PubMed

The novel non-thermal CoBlast process has been used recently to create a hydroxyapatite coating on metallic substrates with improved biological response compared to an uncoated implant. In this study, we compared the biological effect of coatings deposited by this process and the industrial standard technique - plasma-spray. Physicochemical properties of these two coatings have been found to be significantly different in that CoBlast HA is less rough but more hydrophilic than the plasma-spray HA as evidenced by data obtained from profilometry and goniometry. Mesenchymal stem cell attachment and adhesion are enhanced on CoBlast HA. Analysis by a combination of EDX and ICP suggests that the higher crystallinity retained by the CoBlast HA result in slower coating dissolution. Detailed in vitro evaluation reveals that plasma-spray HA might induce slightly faster cell proliferation and earlier osteogenic differentiation, but CoBlast HA becomes equivalent to it by the late osteogenic stage. PCR array facilitated the identification of differentially regulated genes involved in various functional aspects of in vitro osteogenesis by the CoBlast HA coating. The expression level of the functional protein products of these genes are in agreement with the PCR data. Coating metallic screws with HA significantly improves the in vivo osseointegration. By measuring of removal force using torque measurement instrument and analyzing the patterns found in X-ray images it is demonstrated that the two HA coatings elicit comparable osseointegration. Using simulated impaction model, CoBlast HA is shown to maintain better performance in cell attachment and mineralization than plasma-spray HA, especially following significant impactions. This might indicate a potentially greater osteoconductivity of CoBlast HA coating in shear-stress associated surgical applications. Collectively, it was demonstrated that CoBlast HA is an effective alternative to plasma-spray HA coating and a promising replacement for specialized surgical applications. PMID:21801828

Tan, Fei; Naciri, Mariam; Dowling, Denis; Al-Rubeai, Mohamed

2012-01-01

329

Histomorphological study of bone response to hydroxyapatite coating on stainless steel.  

PubMed

Bone response to hydroxyapatite coating on stainless steel has not been so extensively tested in animals as it happened for other metallic substrate, like Ti6Al4V. For this reason, authors performed an in vivo histomorphological electron microscopic study of hydroxyapatite coating on duplex stainless steel cylinders, to gather further evidences on the characters of bone apposition at the interface. Sixteen HA-coated cylinders were implanted in the distal femur of New Zealand White rabbits. Comparison with uncoated controls was made. Retrieval steps were at: 4, 8, 26 and 34 weeks. Specimens were analyzed in a Jeol JSM 6301F scanning electron microscope. The response to HA-coated samples has a morphological character of tight apposition between bone and coating. Osteocytic lacunae may be found few microns close to the coating and newly formed bone is extremely interlocked with it so that even an higher magnification electron-microscopy cannot resolve any discontinuity in between. Pictures of physiological bone-turnover are distinguishable at the bone-coating interface; areas of well preserved coating may be present together with areas where local exfoliation or fragmentation has already completely exposed the metallic substrate. On the opposite in uncoated samples, despite a morphological picture of properly formed bone, the largest area of the metal has no direct apposition with it. PMID:15348457

Merolli, A; Moroni, A; Faldini, C; Tranquilli Leali, P; Giannini, S

2003-04-01

330

A new injectable in situ forming hydroxyapatite and thermosensitive chitosan gel promoted by Na?CO?.  

PubMed

A new injectable in situ forming hydroxyapatite and thermosensitive chitosan gel (chitosan/HA/Na2CO3 gel) promoted by Na2CO3 was preliminarily synthesized. This study was the first to use Na2CO3 as coagulant to construct the chitosan thermosensitive gel. The sol–gel phase transition, degradation, and morphology of the gel were examined. We found that chitosan/HA/Na2CO3 sol with 1.4% Na2CO3 has a suitable gelation time (9 min) and degradation rate. SEM images of the dried gel show a porous netlike framework. TEM, EDS, and XRD were combined to confirm the presence of hydroxyapatite. In vitro cell culture was performed by using rat bone mesenchymal stem cells (rBMSCs). rBMSCs survived well on the chitosan gel scaffold that formed in vitro and in vivo, indicating that the chitosan gel was a suitable substrate for the attachment and proliferation of rBMSCs. Subcutaneous implantation of the chitosan gel formed in situ into a nude mouse revealed that the chitosan gel loaded with rBMSCs could lead to angiogenesis. PMID:24795961

Li, Fangfang; Liu, Yang; Ding, Yun; Xie, Qiufei

2014-04-01

331

Design of a substrate heater for calcium hydroxyapatite coating by pulsed laser ablation  

SciTech Connect

Calcium hydroxyapatite (HA) is the main chemical constituent of bone. When replacement hip joints are coated with this chemical, the body may be more likely to accept the artificial joint, forming new bone that bonds the joint to the original leg bone. HA deposited by laser ablation in vacuum adheres to the substrate better at high temperatures of up to 700 C. This heater should be capable of uniformly heating to 700 C a silicon disk 150 mm in diameter. The heater consists of two wire heating coils brazed into a disk of stainless steel, with tantalum shields on top and at the sides of the heater to minimize radiation loss. Three spring-rotation clamps at the bottom of the heater hold the substrate disk in place. This report describes the heater and how it was developed, including design evolution and thermal modeling. Also, detailed information about parts is discussed.

Chang, T.; Havstad, M.A.

1995-07-24

332

Cyclic fatigue of hydroxyapatite-coated titanium alloy implant material--effect of crystallinity.  

PubMed

Titanium alloy (ASTM F-136) rods were coated with hydroxyapatite (HA) of 3 levels of crystallinity, which were determined by X-ray diffraction (XRD) analysis to be 60.5%, 52.8%, and 47.8%. Fourier Transform Infrared (FTIR) spectroscopy analysis showed the removal of the hydroxyl and carbonate groups as compared to the original HA powder. It appears that these changes are caused by the high temperature plasma spray coating process. Cyclic fatigue testing in a lactated Ringer's solution to 5 million cycles showed no statistical difference in calcium dissolution among the 3 crystalline levels, whereas phosphorus dissolution was lowest from the highest crystalline coating sample. The mechanical properties, however, did not change in response to fatigue loading. PMID:10167358

Ashroff, S; Napper, S A; Hale, P N; Siriwardane, U; Mukherjee, D P

1996-01-01

333

The influence of radiation therapy on subperiosteal hydroxyapatite implants in rabbits  

SciTech Connect

Granular hydroxyapatite (HA) was implanted into subperiosteal pockets along both the right and left proximal tibias of 12 adult New Zealand white rabbits. The left extremities of 10 rabbits served as controls, whereas the right sides were irradiated with 2,250 rad in three doses over 5 days. The animals were killed at 1-week intervals starting at 2 weeks postirradiation. One half of each site was evaluated using standard histologic techniques while the other half was examined as a nondecalcified section. The quantity and the quality of new bone formation was determined using a rating scale and histomorphometric digitization. The results of this 4-month study showed that the amount of new bone formation around the HA granules was significantly greater in the irradiated sites. The irradiation produced no deleterious effects on the implant or the surrounding tissue areas.

Khateery, S.; Waite, P.D.; Lemons, J.E. (King Saud Univ., Riyadh (Saudi Arabia))

1991-07-01

334

Agarose-polyaldehyde microsphere beads: Synthesis and biomedical applications  

Microsoft Academic Search

Polyaldehyde microspheres, polyglutaraldehyde (PGL), and polyacrolein (PA) were synthesized by polymerizing glutaraldehyde\\u000a and acrolein in the presence of an appropriate surfactant. The microspheres with average diameter of 0.2 ?m were used for\\u000a the specific labeling of human red blood cells (RBC) and mouse lymphocytes. The “naked” microspheres were encapsulated with\\u000a agarose and formed agarose-polyaldehyde microsphere beads in sizes ranging from

Shlomo Margel

1983-01-01

335

Synthesis and Reactions of Hydrophilic Functional Microspheres for Immunological Studies  

Microsoft Academic Search

There is a need for hydrophilic polymeric microspheres with functional groups on their surface which can be reacted efficiently with proteins. These microspheres with antibodies (immunoglobulins) covalently bound to their surfaces constitute valuable immunoreagents capable of marking specific receptors (antigens) on cell surface membranes. The main requirements of the microspheres for the above applications are: insolubility in aqueous or organic

A. Rembaum; S. P. S. Yen; R. S. Molday

1979-01-01

336

Fiber laser using a microsphere resonator as a feedback element  

E-print Network

. An adiabatic fiber taper is then used to couple laser light into and out of these microspheres.6 The gapFiber laser using a microsphere resonator as a feedback element Khanh Kieu and Masud Mansuripur in fiber lasers. Due to their high quality factor Q 108 , microsphere resonators possess a narrow

Kieu, Khanh

337

Preparation of monodisperse, reactive hydrogel microspheres and their amphoterization  

Microsoft Academic Search

Monodisperse, reactive hydrogel microspheres were prepared by precipitation polymerization ofp-nitrophenyl acrylate (NPA) with acrylamide, methacrylic acid, and methylenebisacrylamide in ethanol. The size of microspheres was controlled by the monomer ratio. Some fraction of reactive ester decomposed during the polymerization. The reactive hydrogel microspheres were converted to amphoteric ones by the reaction of NPA units with diamine. The isoelectric point of

M. Kashiwabara; K. Fujimoto; H. Kawaguchi

1995-01-01

338

Modified Open-door Laminoplasty Using Hydroxyapatite Spacers and Miniplates  

PubMed Central

Objective Cervical laminoplasty has been widely accepted as one of the major treatments for cervical myelopathy and various modifications and supplementary procedures have been devised to achieve both proper decompression and stability of the cervical spine. We present the retrospectively analyzed results of a modified unilateral open-door laminoplasty using hydroxyapatite (HA) spacers and malleable titanium miniplates. Methods From June 2008 to May 2012, among patients diagnosed with cervical spondylotic myelopathy and ossification of posterior longitudinal ligament, the patients who received laminoplasty were reviewed. Clinical outcome was assessed using Frankel grade and Japanese Orthopaedic Association score. The radiologic parameters were obtained from plain films, 3-dimensional computed tomography and magnetic resonance images. Results A total of 125 cervical laminae were operated in 38 patients. 11 patients received 4-level laminoplasty and 27 patients received 3-level laminoplasty. Postoperatively, the mean Frankel grade and JOA score were significantly improved from 3.97 to 4.55 and from 12.76 to 14.63, respectively (p<0.001). Radiologically, cervical curvature was worsened from 19.09 to 15.60 (p=0.025). The percentage of range of motion preservation was 73.32±22.39%. The axial dimension of the operated spinal canal was increased from 1.75 to 2.70 cm2 (p<0.001). Conclusion In the presenting study, unilateral open-door laminoplasty using HA spacers and miniplates appears to be a safe, rapid and easy procedure to obtain an immediate and rigid stabilization of the posterior elements of the cervical spine. This modified laminoplasty method showed effective expansion of the spinal canal and favorable clinical outcomes. PMID:25346767

Jin, Sung-Won; Kim, Bum-Joon; Choi, Jong-Il; Ha, Sung-Kon; Kim, Sang-Dae; Lim, Dong-Jun

2014-01-01

339

The pathway to intelligent implants: osteoblast response to nano silicon-doped hydroxyapatite patterning  

PubMed Central

Bioactive hydroxyapatite (HA) with addition of silicon (Si) in the crystal structure (silicon-doped hydroxyapatite (SiHA)) has become a highly attractive alternative to conventional HA in bone replacement owing to the significant improvement in the in vivo bioactivity and osteoconductivity. Nanometre-scaled SiHA (nanoSiHA), which closely resembles the size of bone mineral, has been synthesized in this study. Thus, the silicon addition provides an extra chemical cue to stimulate and enhance bone formation for new generation coatings, and the next stage in metallic implantation design is to further improve cellular adhesion and proliferation by control of cell alignment. Topography has been found to provide a powerful set of signals for cells and form contact guidance. Using the recently developed novel technique of template-assisted electrohydrodynamic atomization (TAEA), patterns of pillars and tracks of various dimensions of nanoSiHA were achieved. Modifying the parameters of TAEA, the resolution of pattern structures was controlled, enabling the topography of a substrate to be modified accordingly. Spray time, flow rate and distance between the needle and substrate were varied to improve the pattern formation of pillars and tracks. The 15 min deposition time provided the most consistent patterned topography with a distance of 50 mm and flow rate of 4 µl min?1. A titanium substrate was patterned with pillars and tracks of varying widths, line lengths and distances under the optimized TAEA processing condition. A fast bone-like apatite formation rate was found on nanoSiHA after immersion in simulated body fluid, thus demonstrating its high in vitro bioactivity. Primary human osteoblast (HOB) cells responded to SiHA patterns by stretching of the filopodia between track and pillar, attaching to the apex of the pillar pattern and stretching between two. HOB cells responded to the track pattern by elongating along and between the track, and the length of HOB cells was proportional to the gaps between track patterns, but this relationship was not observed on the pillar patterns. The study has therefore provided an insight for future design of next generation implant surfaces to control and guide cellular responses, while TAEA patterning provides a controllable technique to provide topography to medical implants. PMID:21208969

Munir, G.; Koller, G.; Di Silvio, L.; Edirisinghe, M. J.; Bonfield, W.; Huang, J.

2011-01-01

340

Mechanical, in vitro antimicrobial, and biological properties of plasma-sprayed silver-doped hydroxyapatite coating.  

PubMed

Implant-related infection is one of the key concerns in total joint hip arthroplasties. To reduce bacterial adhesion, we used silver (Ag)/silver oxide (Ag(2)O) doping in plasma sprayed hydroxyapatite (HA) coating on titanium substrate. HA powder was doped with 2.0, 4.0, and 6.0 wt % Ag, heat-treated at 800 °C and used for plasma spray coating using a 30 kW plasma spray system, equipped with supersonic nozzle. Application of supersonic plasma nozzle significantly reduced phase decomposition and amorphous phase formation in the HA coatings as evident by X-ray diffraction (XRD) study and Fourier transformed infrared spectroscopic (FTIR) analysis. Adhesive bond strength of more than 15 MPa ensured the mechanical integrity of the coatings. Resistance against bacterial adhesion of the coatings was determined by challenging them against Pseudomonas aeruginosa (PAO1). Live/dead staining of the adherent bacteria on the coating surfaces indicated a significant reduction in bacterial adhesion due to the presence of Ag. In vitro cell-material interactions and alkaline phosphatase (ALP) protein expressions were evaluated by culturing human fetal osteoblast cells (hFOB). Our results suggest that the plasma-sprayed HA coatings doped with an optimum amount of Ag can have excellent antimicrobial property without altering mechanical property of the Ag-doped HA coatings. PMID:22313742

Roy, Mangal; Fielding, Gary A; Beyenal, Haluk; Bandyopadhyay, Amit; Bose, Susmita

2012-03-01

341

Freeze casting of porous hydroxyapatite scaffolds. I. Processing and general microstructure.  

PubMed

Freeze casting of aqueous suspensions on a cold substrate was investigated as a method for preparing hydroxyapatite (HA) scaffolds with unidirectional porosity. In the present paper, we report on the ability to manipulate the microstructure of freeze-cast constructs by controlling the processing parameters. Constructs prepared from aqueous suspensions (5-20 volume percent particles) on a steel substrate at -20 degrees C had a lamellar-type microstructure, consisting of plate-like HA and unidirectional pores oriented in the direction of freezing. Sintering for 3 h at 1350 degrees C produced constructs with dense HA lamellas, porosity of approximately 50%, and inter-lamellar pore widths of 5-30 microm. The thickness of the HA lamellas decreased but the width of the pores increased with decreasing particle concentration. Decreasing the substrate temperature from -20 degrees C to -196 degrees C produced a finer lamellar microstructure. The use of water-glycerol mixtures (20 wt % glycerol) as the solvent in the suspension resulted in the production of finer pores (1-10 microm) and a larger number of dendritic growth connecting the HA lamellas. On the other hand, the use of water-dioxane mixtures (60 wt % dioxane) produced a cellular-type microstructure with larger pores (90-110 microm). The ability to produce a uniaxial microstructure and its manipulation by controlling the processing parameters indicate the potential of the present freeze casting route for the production of scaffolds for bone tissue engineering applications. PMID:18098195

Fu, Qiang; Rahaman, Mohamed N; Dogan, Fatih; Bal, B Sonny

2008-07-01

342

Hydroxyapatite/polylactide biphasic combination scaffold loaded with dexamethasone for bone regeneration.  

PubMed

This study presents a novel design of a ceramic/polymer biphasic combination scaffold that mimics natural bone structures and is used as a bone graft substitute. To mimic the natural bone structures, the outside cortical-like shells were composed of porous hydroxyapatite (HA) with a hollow interior using a polymeric template-coating technique; the inner trabecular-like core consisted of porous poly(D,L-lactic acid) (PLA) that was loaded with dexamethasone (DEX) and was directly produced using a particle leaching/gas forming technique to create the inner diameter of the HA scaffold. It was observed that the HA and PLA parts of the fabricated HA/PLA biphasic scaffold contained open and interconnected pore structures, and the boundary between both parts was tightly connected without any gaps. It was found that the structure of the combination scaffold was analogous to that of natural bone based on micro-computed tomography analysis. Additionally, the dense, uniform apatite layer was formed on the surface of the HA/PLA biphasic scaffold through a biomimetic process, and DEX was successfully released from the PLA of the biphasic scaffold over a 1-month period. This release caused human embryonic palatal mesenchyme cells to proliferate, differentiate, produce ECM, and form tissue in vitro. Therefore, it was concluded that this functionally graded scaffold is similar to natural bone and represents a potential bone-substitute material. PMID:21954052

Son, Jun-Sik; Kim, Su-Gwan; Oh, Ji-Su; Appleford, Mark; Oh, Sunho; Ong, Joo L; Lee, Kyu-Bok

2011-12-15

343

Mechanical properties of polyvinylalcohol/hydroxyapatite cryogel as potential artificial cartilage.  

PubMed

The technological advances in material science are not enough to overcome the challenge of construct a material be able to replace the cartilage. The designed material has to meet the mechanical properties of cartilage and has to be also capable to be integrated with the articulation. Articular cartilage damage is a persistent and increasing problem which affects millions of people worldwide. Poly vinyl alcohol (PVA) hydrogels are promising implants, due to their similar properties as soft tissue; however their low mechanical resistance and durability together with its lack to integrate with the surrounding tissue restrict their application in this area. The poor adhesion can be solved by the development a composite hydrogel with bioactive and biocompatible filler, as hydroxyapatite (HA). The aim of this work was to obtain and characterize (physically, chemically and mechanically) PVA/HA composite hydrogels for potential application as articular replacement. Hence, composite hydrogels were prepared by adding of different amounts of HA in an aqueous solution of PVA and subsequent freezing-thawing cycles. It was observed that the addition of HA modified the physical and chemical features of the hydrogel and promoted the material crosslinking and stability. Moreover, it was found that the mechanical properties (compression, tension and nanoindentation) of the hydrogels were improved by the addition of HA. All these result indicate that these materials could be used as a potential cartilage replacement. However, further in vitro and in vivo studies are mandatory for future possible clinical applications and are actually being carried out. PMID:24556324

Gonzalez, Jimena S; Alvarez, Vera A

2014-06-01

344

Silver-doped hydroxyapatite coatings formed on Ti-6Al-4V substrates and their characterization.  

PubMed

Coatings with antibacterial components for medical implants are recommended to reduce the risk of bacterial infections. Therefore hydroxyapatite (HA) coatings with addition of chitosan (CS) and silver (Ag) are proposed in this work in an attempt to resolve this problem. Ti-6Al-4V substrates were modified by a chitosan film to study the influence of surface modification on the formation of the HA-Ag and HA-CS-Ag coatings. Using a thermal substrate method, HA and HA-CS coatings doped with Ag(+) were prepared at low substrate temperatures (90°C). Coated surfaces were examined using X-ray diffraction and scanning electron microscopy. The amount of silver in the deposited coatings was analyzed by atomic absorption spectroscopy. From this study it is concluded that the substrate surface modified by a chitosan film promotes the coating formation and increases the antibacterial activity of produced coatings against a strain of Escherichia coli. The adhesion of E. coli (ATCC 25922) to sheep erythrocytes was decreased by 14% as compared with the reference samples without Ag. It could be explained by the inhibition of bacterial adhesins by Ag(+) ions released. The combined action of silver ions and chitosan resulted in a 21% decrease in adhesive index. PMID:24433906

Yanovska, A A; Stanislavov, A S; Sukhodub, L B; Kuznetsov, V N; Illiashenko, V Yu; Danilchenko, S N; Sukhodub, L F

2014-03-01

345

Fostering hydroxyapatite bioactivity and mechanical strength by Si-doping and reinforcing with multiwall carbon nanotubes.  

PubMed

The aim of the present study was to prepare resorbable hydroxyapatite (HA) based bone graft materials reinforced with carbon nanotubes as a way to cope with the inability of pure HA to resorb and its intrinsic brittleness and poor strength that restrict its clinical applications under load-bearing conditions. With this purpose, a Si-doped HA nanopowder (n-Si0.8HA) was prepared by chemical synthesis and used as composite matrix reinforced with different amounts of functionalized multiwall carbon nanotubes (MWCNTs). The effect of the added amounts of MWCNTs on the mechanical properties of nanocomposites and their in vitro biomineralization was assessed by bending strength measurements, immersing tests in simulated body fluid solution (SBF), scanning electron microscopy (SEM), and inductively coupled plasma atomic emission spectroscopy analysis (ICP-AES). The bioactivity and bending strength were enhanced, reaching maximum balanced values for an optimum addition of 3 wt.% f-MWCNTs. These results might contribute to broaden the potential applications of HA-based bone grafts. PMID:24738405

Belmamouni, Younes; Bricha, Meriame; Essassi, El Mokhtar; Ferreira, José M F; El Mabrouk, Khalil

2014-06-01

346

A novel ordered nano hydroxyapatite coating electrochemically deposited on titanium substrate.  

PubMed

A novel porous nano hydroxyapatite (HA) coating has been prepared on commercially pure titanium substrate by a modified electrochemical deposition method. The physico-chemical and biological properties of the coating were characterized by SEM, XRD, FTIR, Raman, and in vitro cell culture test respectively. The SEM patterns show a uniform microporous morphology consisting of wirelike crystals at nanometer scale. It is suggested that under controlled deposition conditions, the primary HA nanowires grow and self-assemble to construct an ordered microporous nest-like morphology, thus to form a nano-micro two-level structure. The XRD results demonstrate that the HA nanowires are orderly arranged with their c-axis preferentially perpendicular to the substrate surface. The Raman and IR spectra affirm that the main component of the coating is well crystallized HA. An interdigitation phenomenon of the MG63 human osteosarcoma cells with the HA nanowires is observed in the in vitro test, indicating excellent biocompatibility and bioactivity for the prepared coating. PMID:17109412

Hu, Ren; Lin, Chang-Jian; Shi, Hai-Yan

2007-03-01

347

Mechanochemical Synthesis of Hydroxyapatite and Its Modifications: Composition, Structure, and Properties  

NASA Astrophysics Data System (ADS)

The mechanochemical method is used to synthesize samples of hydroxyapatite (HA) with substitution of the phosphate ion by silicate and zirconate ions, and substitution of calcium ions by copper ions. In the process of mechanochemical synthesis, carbonate ions and water molecules are incorporated into the structure of HA due to interaction of components of the reaction mixture with air. Intrusion of carbonate into the structure of HA is a competing process with modification of apatite by silicate and zirconate anions; therefore, the composition of the product during synthesis differs from the prescribed one. After annealing of the samples, the composition of the anion-modified HA can be described by the formula ??10(??4)6- ? (??4) ? (??)2- ? , where (??4)4- is the modifying anion. Substitution of calcium by copper ions localized at the ??1 position has been detected. Silver ions are not incorporated into the structure of HA, but are distributed in the apatite matrix in the form of nanocrystals of metallic silver.

Chaikina, M. V.; Bulina, N. V.; Ishchenko, A. V.; Prosanov, I. Yu.

2014-02-01

348

Interdiffusion in short-fibre reinforced hydroxyapatite ceramics  

Microsoft Academic Search

Sintering in air and hot isostatic pressing are production methods regarded as being capable of producing fibre-reinforced hydroxyapatite ceramics for biomedical applications. These composites may have the advantage of improved mechanical properties and be suitable for applications in areas where there are significant levels of load on the material. The use of pure hydroxyapatite is restricted to those free of

M. Knepper; B. K. Milthorpe; S. Moricca

1998-01-01

349

Bone Remodeling and Hydroxyapatite Resorption in Coated Primary Hip Prostheses  

PubMed Central

Hydroxyapatite coatings for THA promote bone ongrowth, but bone and coating are exposed to stress shielding-driven osteoclastic resorption. We asked: (1) if the resorption of hydroxyapatite coating and bone ongrowth correlated with demographics; (2) if the resorption related to the stem level; and (3) what happens to the implant-bone interface when all hydroxyapatite coating is resorbed? We recovered 13 femoral components from cadaveric specimens 3.3 to 11.2 years after uneventful primary THA. Three cross sections (proximal, medial, distal) of the hydroxyapatite-coated proximal implant sleeve were analyzed by measuring the percentage of residual hydroxyapatite and bone ongrowth on the implant perimeter. Hydroxyapatite resorption was independent of patient age but increased with time in vivo and mostly was gone after 8 years. Bone ongrowth was independent of time in vivo but decreased with aging patients. Only in the most proximal section did less residual hydroxyapatite correlate with less bone ongrowth. Hydroxyapatite resorption, which was more proximal than distal, showed no adverse effects on the implant-bone interface. PMID:18855086

Tonino, Alphons J.; Heyligers, Ide C.; Grimm, Bernd

2008-01-01

350

Use of rapidly hardening hydroxyapatite cement for facial contouring surgery.  

PubMed

Hydroxyapatite cement is an ideal alloplastic material to replace the autogenous bone grafts in craniofacial surgery. Hydroxyapatite cement is advantageous because it can be easily molded by hand unlike other alloplastic materials such as silicone and high-density polyethylene. For aesthetic applications of hydroxyapatite cement, we evaluated the efficacy and safety of the rapidly hardening hydroxyapatite cement used in facial contour augmentation, especially for the forehead and the malar area. A total of 18 cases of facial skeleton augmentation or contouring surgery using rapidly hardening hydroxyapatite cement (Mimix; Biomet, Warsaw, IN) were examined, and the long-term cosmetic results and any complications were also analyzed. The aims of facial contouring surgeries were to correct the following conditions: hemifacial microsomia, craniosynostosis, posttraumatic facial deformity, deformity after tumor resection, dentofacial deformity, and Romberg disease. The application sites of hydroxyapatite cement were the forehead, malar area, chin, and paranasal area. A mean of 16 g (range, 5-50 g) of the hydroxyapatite cement was used. Postoperative infection, seroma, and migration of the implant were not observed during the follow-up period of 23 months. Rapidly hardening hydroxyapatite cement, Mimix, is easy to manipulate, promptly sclerotized, and can be replaced by living bone tissue, with a low complication rate. Therefore, it can be an optimal treatment that can be used instead of other conventional types of alloplastic materials used in facial contouring surgery. PMID:20613576

Lee, Dong Won; Kim, Ji Ye; Lew, Dae Hyun

2010-07-01

351

Elasticity and viscoelasticity of embolization microspheres.  

PubMed

The present study investigates the mechanical properties of three embolization microspheres (E-ms): tris-acryl gelatin microspheres (TG-ms), acrylamido polyvinyl alcohol microspheres (APVA-ms), and polyphosphazene-coated polymethylmethacrylate microspheres (PP-PMMA-ms). Compression and relaxation tests were performed on monolayers of particles and their Young's moduli and relaxation half times (RHTs) were determined. The elasticity of E-ms was evaluated by applying Hertz theory with the assumptions of incompressibility and a Poisson's ratio of 0.5. The Young's moduli of TG-ms, APVA-ms, and PP-PMMA-ms were 39.6±5.05 kPa, 18.8±4.00 kPa, and 13.6±1.98 kPa, respectively. The RHTs of TG-ms, APVA-ms, and PP-PMMA-ms were 52.3±5.56 s, 59.1±8.16 s, and 31.0±7.01 s, respectively. TG-ms have a high rigidity and deform slightly under a sustained compression since they have a high elasticity. PP-PMMA-ms are soft and deform a lot under sustained compression. They are more viscous than the other two microspheres. APVA-ms have intermediate material properties, having the same low rigidity as PP-PMMA-ms and being more elastic than TG-ms. PMID:22098916

Hidaka, Kuniyuki; Moine, Laurence; Collin, Guillaume; Labarre, Denis; Grossiord, Jean Louis; Huang, Nicolas; Osuga, Keigo; Wada, Shigeo; Laurent, Alexandre

2011-11-01

352

Microstructure and mechanical properties of an Mg-3Zn- o.5Zr-5HA nanocomposite processed by ECAE  

NASA Astrophysics Data System (ADS)

Mg matrix composites reinforced by natural bone constituent hydroxyapatite (HA) particles have shown promising in-vitro corrosion resistance but are inconsistent in both electrochemical and mechanical performances because of severe particle segregations. The present work was carried out to investigate the feasibility of a novel technology that combines high shear solidification and equal channel angular extrusion (ECAE) for fabricating Mg-HA nanocomposites. Experiments showed that the high shear solidification resulted in a fine and uniform grain structure with a globally uniform HA nanoparticles in fine clusters and the ECAE processing of the as-cast composites resulted in further grain refinement and more importantly the breakdown of nanoparticle aggregates, leading to the formation of a dispersion of true nanoparticles in the Mg alloy matrix with improved mechanical properties. This paper describes mainly the microstructural features and mechanical performance of Mg-3Zn-0.5Zr-xHA (x = 1, 3, 5, 10) nanocomposites, in which the HA was in spherical shape with an average diameter of ~20nm

Li, J.; Huang, Y.

2014-08-01

353

Improvement of dual-leached polycaprolactone porous scaffolds by incorporating with hydroxyapatite for bone tissue regeneration.  

PubMed

Polycaprolactone (PCL)/hydroxyapatite (HA) composite scaffolds were prepared by combining solvent casting and salt particulate leaching with a polymer leaching technique. The hydrophilicity of the dual-leached scaffold was improved by alkaline (NaOH) treatment. Well-defined interconnected pores were detected by scanning electron microscopy. The water absorption capacity of the NaOH-treated PCL/HA dual-leached scaffold increased greatly, confirming that the hydrophilicity of the scaffold was improved by NaOH treatment. The compressive modulus of the PCL/HA dual-leached scaffold was greatly increased by the addition of HA particles. An indirect evaluation of the cytotoxicity of all PCL dual-leached scaffolds with mouse fibroblastic cells (L929) and mouse calvaria-derived pre-osteoblastic cells (MC3T3-E1) indicated that the PCL dual-leached scaffolds are non-toxic to cells. The ability of the scaffolds to support mouse calvaria-derived pre-osteoblastic cell (MC3T3-E1) attachment, proliferation, differentiation, and mineralization was also evaluated. Although the viability of cells was lower on the PCL/HA dual-leached scaffold than on the tissue-culture polystyrene plates (TCPS) and on the other substrates at early time points, both the PCL and NaOH-treated PCL/HA dual-leached scaffolds supported the attachment of MC3T3-E1 at significantly higher levels than TCPS. During the proliferation period (days 1-3), all of the PCL dual-leached scaffolds were able to support the proliferation of MC3T3-E1 at higher levels than the TCPS; in addition, the cells grown on NaOH-treated PCL/HA dual-leached scaffolds proliferated more rapidly. The cells cultured on the surfaces of NaOH-treated PCL/HA dual-leached scaffolds had the highest rate of mineral deposition. PMID:25291106

Thadavirul, Napaphat; Pavasant, Prasit; Supaphol, Pitt

2014-12-01

354

Thickness of Hydroxyapatite Nanocrystal Controls Mechanical Properties of the Collagen-Hydroxyapatite Interface  

E-print Network

, United States ABSTRACT: Collagen-hydroxyapatite interfaces compose an important building block of bone structures. While it is known that the nanoscale structure of this elementary building block can affect the mechanical properties of bone, a systematic understanding of the effect of the geometry on the mechanical

Buehler, Markus J.

355

Accelerated bone growth in vitro by the conjugation of BMP2 peptide with hydroxyapatite on titanium alloy.  

PubMed

Titanium alloys have been widely used in orthopedic practice due to their inherent bioactivity, however it is still insufficient to truly and reliably incorporate into living bone. In this work, polydopamine film was employed to induce the growth of hydroxyapatite (HA) on titanium alloy to enhance its osteoconductivity. Bone morphogenetic protein-2 (BMP2) peptide was absorbed into the HA particles for osteoinductivity. The precipitation of HA and the existence of BMP2 peptide were examined by X-ray diffraction, X-ray photoelectron spectroscopy and fluorescence microscopy. The dissolution of HA and the release of BMP2 peptide were monitored by measuring the concentrations of calcium ions and BMP2 peptide in phosphate buffered saline solution, respectively. The effect of BMP2 peptide incorporated into HA coating on bone growth was evaluated in vitro by cell culture tests, including cell attachment, alkaline phosphatase (ALP) activity, and gene expression. The results show that the HA particles grown on the substrate are mediated by the polydopamine film. The BMP2 peptide is distributed uniformly on HA-coated substrate and released in a sustained manner. Moreover, the conjunction of HA and BMP2 peptide increases cell adhesion, ALP activity and gene expression of osteogenic markers, which are potentially useful in the development of enhanced orthopedic medical devices. PMID:24304498

Cai, Yanli; Wang, Xiaoyan; Poh, Chye Khoon; Tan, Hark Chuan; Soe, Min Tun; Zhang, Sam; Wang, Wilson

2014-04-01

356

Preparation, characterization, and in vitro osteoblast functions of a nano-hydroxyapatite/polyetheretherketone biocomposite as orthopedic implant material.  

PubMed

A bioactive composite was prepared by incorporating 40 wt% nano-hydroxyapatite (nHA) into polyetheretherketone (PEEK) through a process of compounding, injection, and molding. The mechanical and surface properties of the nHA/PEEK composite were characterized, and the in vitro osteoblast functions in the composite were investigated. The mechanical properties (elastic modulus and compressive strength) of the nHA/PEEK composite increased significantly, while the tensile strength decreased slightly as compared with PEEK. Further, the addition of nHA into PEEK increased the surface roughness and hydrophilicity of the nHA/PEEK composite. In cell tests, compared with PEEK and ultra-high-molecular-weight polyethylene, it was found that the nHA/PEEK composite could promote the functions of MC3T3-E1 cells, including cell attachment, spreading, proliferation, alkaline phosphatase activity, calcium nodule formation, and expression of osteogenic differentiation-related genes. Incorporation of nHA into PEEK greatly improved the bioperformance of PEEK. The nHA/PEEK composite might be a promising orthopedic implant material. PMID:25170265

Ma, Rui; Tang, Songchao; Tan, Honglue; Lin, Wentao; Wang, Yugang; Wei, Jie; Zhao, Liming; Tang, Tingting

2014-01-01

357

Experimental estimation of chronic microsphere loss from the rat myocardium  

SciTech Connect

The aim of this paper was to determine the loss of isotope-labelled microspheres from the rat myocardium under chronic experimental conditions. The method of heterotopic transplantation of the heart from a donor which had received injections of microspheres was used for the first time. The extent of microsphere loss was calculated on the basis of two measurements of the number of microspheres in the heart graft: before transplantation and after 5-24 days in the recipient. Male Wistar rats were used. Scandium 46 was used as the label and the microsphere total was determined with a gamma counter.

Medvedev, O.S.; Martynova, E.R.; Akchurin, R.s.; Khalatov, V.Yu.

1987-06-01

358

Acrolein Microspheres Are Bonded To Large-Area Substrates  

NASA Technical Reports Server (NTRS)

Reactive cross-linked microspheres produced under influence of ionizing radiation in aqueous solutions of unsaturated aldehydes, such as acrolein, with sodium dodecyl sulfate. Diameters of spheres depend on concentrations of ingredients. If polystyrene, polymethylmethacrylate, or polypropylene object immersed in solution during irradiation, microspheres become attached to surface. Resulting modified surface has grainy coating with reactivity similar to free microspheres. Aldehyde-substituted-functional microspheres react under mild conditions with number of organic reagents and with most proteins. Microsphere-coated macrospheres or films used to immobilize high concentrations of proteins, enzymes, hormones, viruses, cells, and large number of organic compounds. Applications include separation techniques, clinical diagnostic tests, catalytic processes, and battery separators.

Rembaum, Alan; Yen, Richard C. K.

1988-01-01

359

Rolling friction of adhesive microspheres  

NASA Astrophysics Data System (ADS)

The rolling friction of adhesive microspheres is an important quantity as it determines the strength and stability of larger aggregates. Current models predict rolling forces that are 1 to 2 orders of magnitude smaller than observed experimentally. Starting from the well-known Johnson-Kendall-Roberts (JKR) contact description, we derive an analytical theory for the rolling friction based on the concept of adhesion hysteresis, e.g. a difference in apparent surface energies for opening/closing cracks. We show how adhesion hysteresis causes the pressure distribution within the contact to become asymmetrical, leading to an opposing torque. Analytical expressions are derived relating the size of the hysteresis, the rolling torque, and the rolling displacement, ?. We confirm the existence of a critical rolling displacement for the onset of rolling, the size of which is set by the amount of adhesion hysteresis and the size of the contact area. We demonstrate how the developed theory is able to explain the large rolling forces and particle-size dependence observed experimentally. Good agreement with experimental results is achieved for adhesion hysteresis values of (??/?) ? 3 for polystyrene, and (??/?) ? 0.5 for silicates, at crack propagation rates of 0.1 µm s-1 and 1-10 µm s-1, respectively.

Krijt, S.; Dominik, C.; Tielens, A. G. G. M.

2014-04-01

360

Polymeric microspheres as protein transduction reagents.  

PubMed

Discovering the function of an unknown protein, particularly one with neither structural nor functional correlates, is a daunting task. Interaction analyses determine binding partners, whereas DNA transfection, either transient or stable, leads to intracellular expression, though not necessarily at physiologically relevant levels. In theory, direct intracellular protein delivery (protein transduction) provides a conceptually simpler alternative, but in practice the approach is problematic. Domains such as HIV TAT protein are valuable, but their effectiveness is protein specific. Similarly, the delivery of intact proteins via endocytic pathways (e.g. using liposomes) is problematic for functional analysis because of the potential for protein degradation in the endosomes/lysosomes. Consequently, recent reports that microspheres can deliver bio-cargoes into cells via a non-endocytic, energy-independent pathway offer an exciting and promising alternative for in vitro delivery of functional protein. In order for such promise to be fully exploited, microspheres are required that (i) are stably linked to proteins, (ii) can deliver those proteins with good efficiency, (iii) release functional protein once inside the cells, and (iv) permit concomitant tracking. Herein, we report the application of microspheres to successfully address all of these criteria simultaneously, for the first time. After cellular uptake, protein release was autocatalyzed by the reducing cytoplasmic environment. Outside of cells, the covalent microsphere-protein linkage was stable for ?90 h at 37 °C. Using conservative methods of estimation, 74.3% ± 5.6% of cells were shown to take up these microspheres after 24 h of incubation, with the whole process of delivery and intracellular protein release occurring within 36 h. Intended for in vitro functional protein research, this approach will enable study of the consequences of protein delivery at physiologically relevant levels, without recourse to nucleic acids, and offers a useful alternative to commercial protein transfection reagents such as Chariot™. We also provide clear immunostaining evidence to resolve residual controversy surrounding FACS-based assessment of microsphere uptake. PMID:24692642

Nagel, David; Behrendt, Jonathan M; Chimonides, Gwen F; Torr, Elizabeth E; Devitt, Andrew; Sutherland, Andrew J; Hine, Anna V

2014-06-01

361

Polymer-functionalised microspheres for immunosensing applications  

NASA Astrophysics Data System (ADS)

Homogeneous polymeric thin layers have been used as functionalising agents on silica microresonators in view of immunosensing applications. We have characterised the microspheres functionalised with poly-L-lactic acid and Eudragit® L100, as an alternative to the commonly used silanes. It is shown that after polymeric functionalization the quality factor of the silica microspheres remains around 107, and that the Q factor is still about 3x105 after chemical activation and covalent binding of immunogammaglobulin. This functionalising process of the microresonator constitutes a promising step towards the achievement of a highly sensitive immunosensor.

Soria, S.; Baldini, F.; Berneschi, S.; Brenci, M.; Cosi, F.; Giannetti, A.; Nunzi conti, G.; Pelli, S.; Righini, G. C.; Tiribilli, B.

2010-02-01

362

Complementary Information on In Vitro Conversion of Amorphous (Precursor) Calcium Phosphate to Hydroxyapatite from Raman Microspectroscopy and Wide-Angle X-Ray Scattering  

Microsoft Academic Search

In addition to mechanical functions, bones have an essential role in metabolic activity as mineral reservoirs that are able\\u000a to absorb and release ions. Bioapatite, considered the major component in the mineralized part of mammalian bones, is a calcium\\u000a phosphate mineral with a structure that closely resembles hydroxyapatite (HA, Ca10[PO4]6[OH]2) with variable chemical substitutions. It is important to note that

M. Kazanci; P. Fratzl; K. Klaushofer; E. P. Paschalis

2006-01-01

363

Deposition of layered bioceramic hydroxyapatite\\/TiO 2 coatings on titanium alloys using a hybrid technique of micro-arc oxidation and electrophoresis  

Microsoft Academic Search

Titanium alloys have been used with some success in several bioimplant applications. However, they can suffer certain disadvantages, such as poor osteoinductive properties and low corrosive-wear resistance. Attempts to overcome the first of these drawbacks have involved coating the metal with the bioceramic material hydroxyapatite (HA), a primary component of bone and a very good osteoinductor. Since TiO2 coatings are

X. Nie; A. Leyland; A. Matthews

2000-01-01

364

Induction of osteoconductivity by BMP-2 gene modification of mesenchymal stem cells combined with plasma-sprayed hydroxyapatite coating  

NASA Astrophysics Data System (ADS)

Success in bone implant depends greatly on the composition and surface features of the implant. The surface-modification measures not only favor the implant's osteoconductivity, but also promote both bone anchoring and biomechanical stability. This paper reports an approach to combine a hydroxyapatite (HA) coated substrate with a cellular vehicle for the delivery of bone morphogenetic protein-2 (BMP-2) synergistically enhancing the osteoconductivity of implant surfaces. We examined the attachment, growth and osteoinductive activity of transfected BMP-producing bone marrow mesenchymal stem cells (BMSCs) on a plasma-sprayed HA coated substrate. It was found that the HA coated substrate could allow the attachment and growth of BMP-2 gene modified BMSCs, and this combined application synergistically enhanced osteconductivity of the substrate surface. This synergistic method may be of osseointegration value in orthopedic and dental implant surgery.

Wu, Jiang; Guo, Ying-qiang; Yin, Guang-fu; Chen, Huai-qing; Kang, Yunqing

2008-11-01

365

Surface phenomena of hydroxyapatite film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants.  

PubMed

In this study, surface phenomena of hydroxyapatite (HA) film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants have been investigated by electron beam physical vapor deposition (EB-PVD), field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), potentiostat and contact angle. The microstructure of Ti-29Nb-xZr alloys exhibited equiaxed structure and alpha" phase decreased, whereas beta phase increased as Zr content increased. The increment of Zr contents in HA coated nanotubular Ti-29Nb-xZr alloys showed good corrosion potential in 0.9% NaCI solution. The wettability of HA coated nanotubular surface was higher than that of non-coated samples. PMID:23755573

Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol

2013-03-01

366

Development of strontium and magnesium substituted porous hydroxyapatite/poly(3,4-ethylenedioxythiophene) coating on surgical grade stainless steel and its bioactivity on osteoblast cells.  

PubMed

The present study deals with the successful development of bilayer coatings by electropolymerisation of poly(3,4-ethylenedioxythiophene) (PEDOT) on surgical grade stainless steel (316L SS) followed by the electrodeposition of strontium (Sr) and magnesium (Mg) substituted porous hydroxyapatite (Sr, Mg-HA). The bilayer coatings were characterised by Fourier transform infrared spectroscopy (FT-IR) and high resolution scanning electron microscopy (HRSEM). Corrosion resistance of the obtained coatings was investigated in Ringer's solution by electrochemical techniques and the results were in good agreement with those obtained from chemical analysis, namely inductively coupled plasma atomic emission spectrometry (ICP-AES). Also, the mechanical and biological properties of the bilayer coatings were analyzed. From the obtained results it was evident that the PEDOT/Sr, Mg-HA bilayer exhibited greater adhesion strength than the Sr, Mg-HA coated 316L SS. In vitro cell adhesion test of the Sr, Mg-HA coating on PEDOT coated specimen is found to be more bioactive compared to that of the single substituted hydroxyapatite (Sr or Mg-HA) on the PEDOT coated 316L SS. Thus, the PEDOT/Sr, Mg-HA bilayer coated 316L SS can serve as a prospective implant material for biomedical applications. PMID:24200951

Gopi, D; Ramya, S; Rajeswari, D; Surendiran, M; Kavitha, L

2014-02-01

367

Poly(lactic-co-glycolic) Acid/Nanohydroxyapatite Scaffold Containing Chitosan Microspheres with Adrenomedullin Delivery for Modulation Activity of Osteoblasts and Vascular Endothelial Cells  

PubMed Central

Adrenomedullin (ADM) is a bioactive regulatory peptide that affects migration and proliferation of diverse cell types, including endothelial cells, smooth muscle cells, and osteoblast-like cells. This study investigated the effects of sustained release of ADM on the modulation activity of osteoblasts and vascular endothelial cells in vitro. Chitosan microspheres (CMs) were developed for ADM delivery. Poly(lactic-co-glycolic) acid and nano-hydroxyapatite were used to prepare scaffolds containing microspheres with ADM. The CMs showed rough surface morphology and high porosity, and they were well-distributed. The scaffolds exhibited relatively uniform pore sizes with interconnected pores. The addition of CMs improved the mechanical properties of the scaffolds without affecting their high porosity. In vitro degradation tests indicated that the addition of CMs increased the water absorption of the scaffolds and inhibited pH decline of phosphate-buffered saline medium. The expression levels of osteogenic-related and angiogenic-related genes were determined in MG63 cells and in human umbilical vein endothelial cells cultured on the scaffolds, respectively. The expression levels of osteogenic-related and angiogenic-related proteins were also detected by western blot analysis. Their expression levels in cells were improved on the ADM delivery scaffolds at a certain time point. The in vitro evaluation suggests that the microsphere-scaffold system is suitable as a model for bone tissue engineering. PMID:23841075

Li, Chunyan; Chen, Yingxin; Dong, Shujun; Chen, Xuesi; Zhou, Yanmin

2013-01-01

368

Lanthanum-containing hydroxyapatite coating on ultrafine-grained titanium by micro-arc oxidation: A promising strategy to enhance overall performance of titanium  

PubMed Central

Titanium is widely used in biomedical materials, particularly in dental implants, because of its excellent biocompatibility and mechanical characteristics. However, titanium implant failures still remain in some cases, varying with implantation sites and patients. Improving its overall performance is a major focus of dental implant research. Equal-channel angular pressing (ECAP) can result in ultrafine-grained titanium with superior mechanical properties and better biocompatibility, which significantly benefits dental implants, and without any harmful alloying elements. Lanthanum (La) can inhibit the acidogenicity of dental plaque and La-containing hydroxyapatite (La-HA) possesses a series of attractive properties, in contrast to La-free HA. Micro-arc oxidation (MAO) is a promising technology that can produce porous and firmly adherent hydroxyapatite (HA) coatings on titanium substrates. Therefore, we hypothesize that porous La-containing hydroxyapatite coatings with different La content (0.89%, 1.3% and 1.79%) can be prepared on ultrafine-grained (~200–400 nm) titanium by ECAP and MAO in electrolytic solution containing 0.2 mol/L calcium acetate, 0.02 mol/L ?-glycerol phosphate disodium salt pentahydrate (?-GP), and lanthanum nitrate with different concentrations to further improve the overall performance of titanium, which are expected to have great potential in medical applications as a dental implant. PMID:24487779

Deng, Zhennan; Wang, LiLi; Zhang, Dafeng; Liu, Jinsong; Liu, Chuantong; Ma, Jianfeng

2014-01-01

369

Lanthanum-containing hydroxyapatite coating on ultrafine-grained titanium by micro-arc oxidation: a promising strategy to enhance overall performance of titanium.  

PubMed

Titanium is widely used in biomedical materials, particularly in dental implants, because of its excellent biocompatibility and mechanical characteristics. However, titanium implant failures still remain in some cases, varying with implantation sites and patients. Improving its overall performance is a major focus of dental implant research. Equal-channel angular pressing (ECAP) can result in ultrafine-grained titanium with superior mechanical properties and better biocompatibility, which significantly benefits dental implants, and without any harmful alloying elements. Lanthanum (La) can inhibit the acidogenicity of dental plaque and La-containing hydroxyapatite (La-HA) possesses a series of attractive properties, in contrast to La-free HA. Micro-arc oxidation (MAO) is a promising technology that can produce porous and firmly adherent hydroxyapatite (HA) coatings on titanium substrates. Therefore, we hypothesize that porous La-containing hydroxyapatite coatings with different La content (0.89%, 1.3% and 1.79%) can be prepared on ultrafine-grained (~200-400 nm) titanium by ECAP and MAO in electrolytic solution containing 0.2 mol/L calcium acetate, 0.02 mol/L beta-glycerol phosphate disodium salt pentahydrate (beta-GP), and lanthanum nitrate with different concentrations to further improve the overall performance of titanium, which are expected to have great potential in medical applications as a dental implant. PMID:24487779

Deng, Zhennan; Wang, LiLi; Zhang, Dafeng; Liu, Jinsong; Liu, Chuantong; Ma, Jianfeng

2014-01-01

370

Friction and wear of hydroxyapatite reinforced high density polyethylene against the stainless steel counterface.  

PubMed

Hydroxyapatite (HA) reinforced high density polyethylene (HDPE) was invented as a biomaterial for skeletal applications. In this investigation, tribological properties (e.g. wear rate and coefficient of friction) of unfilled HDPE and HA/HDPE composites were evaluated against the duplex stainless steel in dry and lubricated conditions, with distilled water or aqueous solutions of proteins (egg albumen or glucose) being lubricants. Wear tests were conducted in a custom-built test rig for HDPE and HA/HDPE containing up to 40 vol % of HA. It was found that HA/HDPE composites had lower coefficients of friction than unfilled HDPE under certain conditions. HA/HDPE also exhibited less severe fatigue failure marks than HDPE. The degradation and fatigue failure of HDPE due to the presence of proteins were severe for low speed wear testing (100 rpm) as compared to high speed wear testing (200 rpm). This was due possibly to the high shear rate at the contact which could remove any degraded film instantaneously at high sliding speed, while with a low sliding speed the build-up of a degraded layer of protein could occur. The degraded protein layer would stay at the contact for a longer time and mechanical activation would induce adverse reactions, weakening the surface layer of HDPE. Both egg albumen and glucose were found to be corrosive to steel and adversely reactive for HDPE and HA/HDPE composites. The wear modes observed were similar to that of ultra-high molecular weight polyethylene. Specimens tested with egg albumen also displayed higher wear rates, which was again attributed to corrosion accelerated wear. PMID:15348592

Wang, M; Chandrasekaran, M; Bonfield, W

2002-06-01

371

Hydrothermal fabrication of hydroxyapatite/chitosan/carbon porous scaffolds for bone tissue engineering.  

PubMed

Porous carbon fiber felts (PCFFs) have great applications in orthopedic surgery because of the strong mechanical strength, low density, high stability, and porous structure, but they are biologically inert. To improve their biological properties, we developed, for the first time, the hydroxyapatite (HA)/chitosan/carbon porous scaffolds (HCCPs). HA/chitosan nanohybrid coatings have been fabricated on PCFFs according to the following stages: (i) deposition of chitosan/calcium phosphate precursors on PCFFs; and (ii) hydrothermal transformation of the calcium phosphate precursors in chitosan matrix into HA nanocrystals. The scanning electron microscopy images indicate that PCFFs are uniformly covered with elongated HA nanoplates and chitosan, and the macropores in PCFFs still remain. Interestingly, the calcium-deficient HA crystals exist as plate-like shapes with thickness of 10-18 nm, width of 30-40 nm, and length of 80-120 nm, which are similar to the biological apatite. The HA in HCCPs is similar to the mineral of natural bone in chemical composition, crystallinity, and morphology. As compared with PCFFs, HCCPs exhibit higher in vitro bioactivity and biocompatibility because of the presence of the HA/chitosan nanohybrid coatings. HCCPs not only promote the formation of bone-like apatite in simulated body fluid, but also improve the adhesion, spreading, and proliferation of human bone marrow stromal cells. Hence, HCCPs have great potentials as scaffold materials for bone tissue engineering and implantation. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1740-1748, 2014. PMID:24687547

Long, Teng; Liu, Yu-Tai; Tang, Sha; Sun, Jin-Liang; Guo, Ya-Ping; Zhu, Zhen-An

2014-11-01

372

Intrinsically superparamagnetic Fe-hydroxyapatite nanoparticles positively influence osteoblast-like cell behaviour  

PubMed Central

Background Superparamagnetic nanoparticles (MNPs) have been progressively explored for their potential in biomedical applications and in particular as a contrast agent for diagnostic imaging, for magnetic drug delivery and more recently for tissue engineering applications. Considering the importance of having safe MNPs for such applications, and the essential role of iron in bone remodelling, this study developed and analysed novel biocompatible and bioreabsorbable superparamagnetic nanoparticles, that avoid the use of poorly tolerated magnetite based nanoparticles, for bone tissue engineering applications. Results MNPs were obtained by doping hydroxyapatite (HA) with Fe ions, by directly substituting Fe2+ and Fe3+ into the HA structure yielding superparamagnetic bioactive phase. In the current study, we have investigated the effects of increasing concentrations (2000??g/ml; 1000??g/ml; 500??g/ml; 200??g/ml) of FeHA MNPs in vitro using Saos-2 human osteoblast-like cells cultured for 1, 3 and 7?days with and without the exposure to a static magnetic field of 320?mT. Results demonstrated not only a comparable osteoblast viability and morphology, but increased in cell proliferation, when compared to a commercially available Ha nanoparticles, even with the highest dose used. Furthermore, FeHA MNPs exposure to the static magnetic field resulted in a significant increase in cell proliferation throughout the experimental period, and higher osteoblast activity. In vivo preliminary results demonstrated good biocompatibility of FeHA superparamagnetic material four weeks after implantation into a critical size lesion of the rabbit condyle. Conclusions The results of the current study suggest that these novel FeHA MNPs may be particularly relevant for strategies of bone tissue regeneration and open new perspectives for the application of a static magnetic field in a clinical setting of bone replacement, either for diagnostic imaging or magnetic drug delivery. PMID:22828388

2012-01-01

373

Use of quartz crystal nanobalance to study the binding and stabilization of albumin and doxycycline on a thin layer of hydroxyapatite  

NASA Astrophysics Data System (ADS)

This study reports the use of quartz crystal nanobalance (QCN) to study the adsorption of two model molecules namely albumin and doxycycline by hydroxyapatite (HA). The work focuses on the deposition of a stable coating of HA on the quartz crystal, modification of the coating using doxycycline and its subsequent effects on albumin adsorption. The uniformity and thickness of the HA coating has been studied using atomic force microscopy (AFM). The functional groups to ascertain the presence of the selected moieties have been characterized by Raman spectroscopy. The results indicate that the mass of albumin deposited on the surface of the HA coated quartz crystal functionalized with doxycycline shows a substantial increase when compared to the standard HA coated quartz crystal. The adsorbed albumin has also been found to be retained for an enhanced period of time. This surface immobilization of doxycycline and subsequent albumin adsorption seem to be a promising approach to confer biomaterials with antithrombogenic and antibacterial surfaces.

Victor, Sunita Prem; Sharma, Chandra P.; Sreenivasan, K.

2011-12-01

374

Si-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sinterability  

SciTech Connect

Synthetic hydroxyapatites incorporating small amounts of Si have shown improved biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. This paper reports a systematic investigation on Si-substituted hydroxyapatite (Si 1.40 wt%) nanopowders produced following two different conventional wet methodologies: (a) precipitation of Ca(NO{sub 3}){sub 2}.4H{sub 2}O and (b) titration of Ca(OH){sub 2}. The influence of the synthesis process on composition, thermal behaviour and sinterability of the resulting nanopowders is studied. Samples were characterised by electron microscopy, induced coupled plasma atomic emission spectroscopy, thermal analysis, infrared spectroscopy, N{sub 2} adsorption measurements, X-ray diffraction and dilatometry. Semicrystalline Si-substituted hydroxyapatite powders made up of needle-like nanoparticles were obtained, the specific surface area ranged between 84 and 110 m{sup 2}/g. Pure and Si-substituted hydroxyapatite nanopowders derived from Ca(NO{sub 3}){sub 2}.4H{sub 2}O decomposed around 1000 deg. C. Si-substituted hydroxyapatite nanopowders obtained from Ca(OH){sub 2} were thermally stable up to 1200 deg. C and showed a distinct decreased thermal stability with respect to the homologous pure sample. Si-substituted hydroxyapatites exhibited higher sintering temperature and increased total shrinkage with respect to pure powders. Nanostructured dense ceramics were obtained by sintering at 1100 deg. C Si-substituted hydroxyapatites derived from Ca(OH){sub 2}.

Bianco, Alessandra [University of Rome Tor Vergata, Department of Chemical Sciences and Technologies, INSTM Research Unit Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy)], E-mail: bianco@stc.uniroma2.it; Cacciotti, Ilaria [University of Rome Tor Vergata, Department of Chemical Sciences and Technologies, INSTM Research Unit Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Lombardi, Mariangela [Politecnico of Torino, Department of Materials Science and Chemical Engineering, INSTM Research Unit Politecnico di Torino: LINCE Lab, Corso Duca degli Abruzzi, 24-10129 Torino (Italy)], E-mail: mariangela.lombardi@polito.it; Montanaro, Laura [Politecnico of Torino, Department of Materials Science and Chemical Engineering, INSTM Research Unit Politecnico di Torino: LINCE Lab, Corso Duca degli Abruzzi, 24-10129 Torino (Italy)

2009-02-04

375

Rapid-prototyped PLGA/?-TCP/hydroxyapatite nanocomposite scaffolds in a rabbit femoral defect model.  

PubMed

Bone tissue engineering scaffolds composed of poly(d,l-lactide:glycolide) (DL-PLGA) and ?-tricalcium phosphate (?-TCP) nanocomposites were prepared and characterized. Scaffolds with two specific architectures were produced via fused deposition modeling (FDM), a type of extrusion freeform fabrication. Microfilaments deposited at angles of 0° and 90° were designated as the 'simple' scaffold architecture, while those deposited at angles alternating between 0°, 90°, 45° and -45° were designated as the 'complex' scaffold architecture. In addition, the simple and complex scaffolds were coated with hydroxyapatite (HA). The surface morphology of the scaffolds was assessed before and after HA coating and uniform distribution of HA coating on the surface was observed by scanning electron microscopy. The scaffolds were implanted into rabbit femoral unicortical bone defects according to four treatment groups based on pore structure and HA coating. After 6 and 12 weeks, scaffolds and host bone were recovered and processed for histology. Data suggest that all configurations of the scaffolds integrated with the host bone and were biocompatible and thus may offer an exciting new scaffold platform for delivery of biologicals for bone regeneration. PMID:22427485

Kim, Jinku; McBride, Sean; Tellis, Brandi; Alvarez-Urena, Pedro; Song, Young-Hye; Dean, David D; Sylvia, Victor L; Elgendy, Hoda; Ong, Joo; Hollinger, Jeffrey O

2012-06-01

376

Mechanical properties and in vitro cell compatibility of hydroxyapatite ceramics with graded pore structure.  

PubMed

In order to improve the mechanical strength of hydroxyapatite (HA) ceramics used as osteoimplants and to enhance cellular penetration functionally graded ceramics with a transition in porosity from the surface towards the centre were designed. The multilayer structures were prepared by multiple tape casting based on an aqueous HA slurry containing polybutylmethacrylate (PBMA) spheres with diameters ranging from 100 to 300 microns. After burning out the PBMA, pores of 70-200 microns were generated. The pore-graded laminates were sintered at temperatures between 1250 degrees C and 1450 degrees C. Bending strength of the pore-graded ceramics was approximately 50% higher as compared to HA of the same pore volume fraction but without gradient structure. The materials were tested in vitro for attachment and activity of osteoblast-like MC3T3-E1 cells over a period of 3 weeks. Cells formed confluent layers on the ceramic surface, penetrated into the graded porosity ranging from 100-150 microns to 250-300 microns in size and showed increasing alkaline phosphatase activity over 3 weeks. The results demonstrated initial in vitro cell compatibility of the functionally graded HA materials and their potential as osteoimplants. PMID:12194531

Werner, Jan; Linner-Krcmar, Britta; Friess, Wolfgang; Greil, Peter

2002-11-01

377

Degradation and biocompatibility of porous nano-hydroxyapatite/polyurethane composite scaffold for bone tissue engineering  

NASA Astrophysics Data System (ADS)

Porous scaffold containing 30 wt% nano-hydroxyapatite (n-HA) and 70 wt% polyurethane (PU) from castor oil was prepared by a foaming method and investigated by X-ray diffraction (XRD), Fourier transform infrared absorption (FTIR), scanning electron microscopy (SEM) techniques. The results show that n-HA particles disperse homogeneously in the PU matrix. The porous scaffold has not only macropores of 100-800 ?m in size but also a lot of micropores on the walls of macropores. The porosity and compressive strength of scaffold are 80% and 271 kPa, respectively. After soaking in simulated body fluid (SBF), hydrolysis and deposition partly occur on the scaffold. The biological evaluation in vitro and in vivo shows that the n-HA/PU scaffold is non-cytotoxic and degradable. The porous structure provides a good microenvironment for cell adherence, growth and proliferation. The n-HA/PU composite scaffold can be satisfied with the basic requirement for tissue engineering, and has the potential to be applied in repair and substitute of human menisci of the knee-joint and articular cartilage.

Dong, Zhihong; Li, Yubao; Zou, Qin

2009-04-01

378

Characteristics improvement of calcium hydroxide dental cement by hydroxyapatite nanoparticles. Part 1: formulation and microstructure.  

PubMed

Calcium hydroxide cement (CHC), which is a direct pulp-capping material, has been widely used for several decades. In spite of the well-known advantages of CHCs, they have some disadvantages as well, such as high solubility, no inherent adhesive qualities, and low mechanical strength. Previous studies were undertaken to improve these deficiencies by implementing changes to modify the conventional CHCs. The aim of the present research is to demonstrate the potential rectification of the aforementioned deficiencies of the commercially available CHCs by adding hydroxyapatite (HA) nanoparticles without lessening their advantages. Here, the synthesized HA nanoparticles were added into the CHCs in two different portions of 3 and 7 wt%. A scanning electron microscope was used to observe and analyze the microstructure, and X-ray energy dispersive analysis was used to analyze the elemental composition of the new CHCs. In addition, setting time, mechanical strength, pH, calcium (Ca) release, and antibacterial behavior were measured to assess how HA nanoparticles influence the characteristics of CHCs. The results showed that adding 3 wt% HA nanoparticles can optimally improve the mechanical strength of the cement and increase the Ca release rate as a mineralization promoter without reducing the antibacterial behavior. PMID:23586755

Yasaei, Mana; Zamanian, Ali; Moztarzadeh, Fathollah; Ghaffari, Maryam; Mozafari, Masoud

2013-01-01

379

Aligned porous barium titanate/hydroxyapatite composites with high piezoelectric coefficients for bone tissue engineering.  

PubMed

It was proposed that the piezoelectric effect played an important physiological role in bone growth, remodelling and fracture healing. An aligned porous piezoelectric composite scaffold was fabricated by freeze casting hydroxyapatite/barium titanate (HA/BT) suspensions. The highest compressive strength and lowest porosity of 14.5MPa and 57.4% with the best parallelism of the pore channels were achieved in the HA10/BT90 composite. HA30/BT70 and HA10/BT90 composites exhibited piezoelectric coefficient d33 of 1.2 and 2.8pC/N, respectively, both of which were higher than the piezoelectric coefficient of natural bone. Increase of the solid loading of the suspension and solidification velocity led to the improvement of piezoelectric coefficient d33. Meanwhile, double-templates resulted in the coexistence of lamellar pores and aligned macro-pores, exhibiting the ability to produce an oriented long-range ordered architecture. The manipulation flexibility of this method indicated the potential for customized needs in the application of bone substitute. An MTT assay indicated that the obtained scaffolds had no cytotoxic effects on L929 cells. PMID:24863210

Zhang, Yan; Chen, Liangjian; Zeng, Jing; Zhou, Kechao; Zhang, Dou

2014-06-01

380

Interactions of Hydroxyapatite with Proteins and Its Toxicological Effect to Zebrafish Embryos Development  

PubMed Central

The increased application of nanomaterials has raised the level of public concern regarding possible toxicities caused by exposure to nanostructures. The interactions of nanosized hydroxyapatite (HA) with cytochrome c and hemoglobin were investigated by zeta-potential, UV-vis, fluorescence and circular dichroism. The experimental results indicated that the interactions were formed via charge attraction and hydrogen bond and obeyed Langmuir adsorption isotherm. The two functional proteins bridged between HA particles to aggregate into the coralloid form, where change of the secondary structure of proteins occurred. From effects of nanosized HA, SiO2 and TiO2 particles on the zebrafish embryos development, they were adsorbed on the membrane surface confirmed by the electronic scanning microscopy. Nano-HA aggregated into the biggest particles around the membrane protein and then caused a little toxicity to development of zebrafish embryos. The SiO2 particles were distributed throughout the outer surface and caused jam of membrane passage, delay of the hatching time and axial malformation. Maybe owing to the oxygen free radical activity, TiO2 caused some serious deformity characters in the cardiovascular system. PMID:22509249

Xu, Zhen; Zhang, Ya-Lei; Song, Cao; Wu, Ling-Ling; Gao, Hong-Wen

2012-01-01

381

An in vitro study into the effect of zinc substituted hydroxyapatite on osteoclast number and activity.  

PubMed

Zinc ions have been shown to inhibit osteoclast development and proliferation both in vitro and in vivo. The same inhibiting effect has been observed in vitro when zinc was substituted into tri-calcium phosphate (TCP). Because of the solubility of TCP it is not an ideal candidate for a material to inhibit osteoclast activity in the long term. Hydroxyapatite (HA) is less soluble and so potentially offers a more long-term, sustainable effect. Previous work has shown that zinc can successfully be substituted into HA and still retain phase purity after heat treatment. The study reported here presents the effects of zinc substituted HA on the development and activity of osteoclast-like cells. It was found that increasing zinc substitution levels led to a decrease in the number of these cells present after 21 days. When resorption activity was investigated it was found that an increase in the amount of zinc present in the discs led to a significant decrease in the amount of resorption taking place on the discs. These results provide evidence for the potential of zinc substituted HA as a material to reduce resorptive activity to provide long-term bonding of implant to bone. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 4136-4141, 2014. PMID:24443251

Shepherd, David V; Kauppinen, Kyösti; Brooks, Roger A; Best, Serena M

2014-11-01

382

Effect of chondroitin sulfate and biglycan on the crystallization of hydroxyapatite under physiological conditions  

NASA Astrophysics Data System (ADS)

Crystallization of hydroxyapatite (HA) in collagen gels has been studied in vitro in order to mimic biomineralization under physiological conditions. In particular, the effect of chondroitine sulfate (CS) and biglycan (BG) additions to the gel on the growth kinetics and morphology of HA crystals has been investigated. Large molecules of CS disrupt the gel and lower its viscosity, thus increasing the nucleation and growth rates as well as the overall mass of crystallized HA clusters, while the individual crystallite shape and size (˜1 ?m long) remain unchanged. In contrast, the presence of about 100 ?g/ml gel of BG limits the crystal size to less than 100 nm, since the protein cores of BG bind to collagen fibers forming a three-dimensional fiber network with a "lattice" constant of about 50 nm. This network provides preferential sites for ordered heterogeneous nucleation and also prevents clustering of HA crystals. Besides the general importance of these results for studying the biomineralization processes, they may explain the apparition of osteoporosis in BG-gene deficient mice.

Gafni, G.; Septier, D.; Goldberg, M.

1999-09-01

383

Molecular dynamics simulation of mechanical behavior of osteopontin-hydroxyapatite interfaces.  

PubMed

Bone is characterized with an optimized combination of high stiffness and toughness. The understanding of bone nanomechanics is critical to the development of new artificial biological materials with unique properties. In this work, the mechanical characteristics of the interfaces between osteopontin (OPN, a noncollagenous protein in extrafibrillar protein matrix) and hydroxyapatite (HA, a mineral nanoplatelet in mineralized collagen fibrils) were investigated using molecular dynamics method. We found that the interfacial mechanical behavior is governed by the electrostatic attraction between acidic amino acid residues in OPN and calcium in HA. Higher energy dissipation is associated with the OPN peptides with a higher number of acidic amino acid residues. When loading in the interface direction, new bonds between some acidic residues and HA surface are formed, resulting in a stick-slip type motion of OPN peptide on the HA surface and high interfacial energy dissipation. The formation of new bonds during loading is considered to be a key mechanism responsible for high fracture resistance observed in bone and other biological materials. PMID:24786380

Lai, Zheng Bo; Wang, Mingchao; Yan, Cheng; Oloyede, Adekunle

2014-08-01

384

Optimization of the sintering atmosphere for high-density hydroxyapatite–carbon nanotube composites  

PubMed Central

Hydroxyapatite–carbon nanotube (HA–CNT) composites have the potential for improved mechanical properties over HA for use in bone graft applications. Finding an appropriate sintering atmosphere for this composite presents a dilemma, as HA requires water in the sintering atmosphere to remain phase pure and well hydroxylated, yet CNTs oxidize at the high temperatures required for sintering. The purpose of this study was to optimize the atmosphere for sintering these composites. While the reaction between carbon and water to form carbon monoxide and hydrogen at high temperatures (known as the ‘water–gas reaction’) would seem to present a problem for sintering these composites, Le Chatelier's principle suggests this reaction can be suppressed by increasing the concentration of carbon monoxide and hydrogen relative to the concentration of carbon and water, so as to retain the CNTs and keep the HA's structure intact. Eight sintering atmospheres were investigated, including standard atmospheres (such as air and wet Ar), as well as atmospheres based on the water–gas reaction. It was found that sintering in an atmosphere of carbon monoxide and hydrogen, with a small amount of water added, resulted in an optimal combination of phase purity, hydroxylation, CNT retention and density. PMID:20573629

White, Ashley A.; Kinloch, Ian A.; Windle, Alan H.; Best, Serena M.

2010-01-01

385

A DPA Attack on the Improved Ha-Moon Algorithm ?  

E-print Network

A DPA Attack on the Improved Ha-Moon Algorithm ? Dong Jin PARK and Pil Joong LEE Information@postech.ac.kr Abstract. The algorithm proposed by Ha and Moon [2] is a counter- measure against power analysis. The Ha-Moon, Yen, Chen, Moon and Ha improved the algorithm by removing these drawbacks [7]. Their new algorithm

386

Interfacial characteristics and determination of cohesive and adhesive strength of plasma-coated hydroxyapatite via nanoindentation and microscratch techniques.  

PubMed

We investigate the chemical composition and mechanical properties of plasma-deposited hydroxyapatite on grit-blasted Ti-6Al-4V coupons as models of typical prosthetic hip implants. Nanoindentation is used to extract the mechanical properties of the hydroxyapatite (HA) coating and to evaluate the behavior of the material as a function of distance from the interface. A microscratch technique was used to determine parameters of cohesive and adhesive failure of the material that are critical in determining the functionality of these biomedical devices. This delamination method has not been studied in detail before and is usually considered to be unsuitable because of the thickness of the HA and the roughness of the substrate. However, through cross-section analysis of the scratch test, we can determine the point at which the HA delaminates from the substrate. It was concluded that spallation occurs locally, and there is no evidence of gross spallation, indicating that the coating is well adhered to the substrate. PMID:25167343

McManamon, Colm; de Silva, Johann P; Power, John; Ramirez-Garcia, Sonia; Morris, Michael A; Cross, Graham L W

2014-09-30

387

Mechanical, rheological, and bioactivity properties of ultra high-molecular-weight polyethylene bioactive composites containing polyethylene glycol and hydroxyapatite.  

PubMed

Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50?phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis. PMID:22666129

Ahmad, Mazatusziha; Uzir Wahit, Mat; Abdul Kadir, Mohammed Rafiq; Mohd Dahlan, Khairul Zaman

2012-01-01

388

Crack Propagation Resistance of ?-Al2O3 Reinforced Pulsed Laser-Deposited Hydroxyapatite Coating on 316 Stainless Steel  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) is a widely used bioceramic known for its chemical similarity with that of bone and teeth (Ca/P ratio of 1.67). But, owing to its extreme brittleness, ?-Al2O3 is reinforced with HA and processed as a coating via pulsed laser deposition (PLD). Reinforcement of ?-Al2O3 (50 wt.%) in HA via PLD on 316L steel substrate has shown modulus increase by 4% and hardness increase by 78%, and an improved adhesion strength of 14.2 N (improvement by 118%). Micro-scratching has shown an increase in the coefficient-of-friction from 0.05 (pure HA) to 0.17 (with 50 wt.% Al2O3) with enhancement in the crack propagation resistance (CPR) up to 4.5 times. Strong adherence of PLD HA-Al2O3 coatings (~4.5 times than that of HA coating) is attributed to efficient release of stored tensile strain energy (~17 × 10-3 J/m2) in HA-Al2O3 composites, making it a potential damage-tolerant bone-replacement surface coating.

Bajpai, Shubhra; Gupta, Ankur; Pradhan, Siddhartha Kumar; Mandal, Tapendu; Balani, Kantesh

2014-09-01

389

Mechanical, Rheological, and Bioactivity Properties of Ultra High-Molecular-Weight Polyethylene Bioactive Composites Containing Polyethylene Glycol and Hydroxyapatite  

PubMed Central

Ultrahigh-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) blends prepared using polyethylene glycol PEG as the processing aid and hydroxyapatite (HA) as the reinforcing filler were found to be highly processable using conventional melt blending technique. It was demonstrated that PEG reduced the melt viscosity of UHMWPE/HDPE blend significantly, thus improving the extrudability. The mechanical and bioactive properties were improved with incorporation of HA. Inclusion of HA from 10 to 50?phr resulted in a progressive increase in flexural strength and modulus of the composites. The strength increment is due to the improvement on surface contact between the irregular shape of HA and polymer matrix by formation of mechanical interlock. The HA particles were homogenously distributed even at higher percentage showed improvement in wetting ability between the polymer matrix and HA. The inclusion of HA enhanced the bioactivity properties of the composite by the formation of calcium phosphate (Ca-P) precipitates on the composite surface as proven from SEM and XRD analysis. PMID:22666129

Ahmad, Mazatusziha; Wahit, Mat Uzir; Abdul Kadir, Mohammed Rafiq; Mohd Dahlan, Khairul Zaman

2012-01-01

390

Preparation of small bio-compatible microspheres  

NASA Technical Reports Server (NTRS)

Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such a hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent.

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

1979-01-01

391

Proteolytically activated anti-bacterial hydrogel microspheres.  

PubMed

Hydrogels are finding increased clinical utility as advances continue to exploit their favorable material properties. Hydrogels can be adapted for many applications, including surface coatings and drug delivery. Anti-infectious surfaces and delivery systems that actively destroy invading organisms are alternative ways to exploit the favorable material properties offered by hydrogels. Sterilization techniques are commonly employed to ensure the materials are non-infectious upon placement, but sterilization is not absolute and infections are still expected. Natural, anti-bacterial proteins have been discovered which have the potential to act as anti-infectious agents; however, the proteins are toxic and need localized release to have therapeutic efficacy without toxicity. In these studies, we explore the use of the glutathione s-transferase (GST) to anchor the bactericidal peptide, melittin, to the surface of poly(ethylene glycol) diacrylate (PEGDA) hydrogel microspheres. We show that therapeutic levels of protein can be anchored to the surface of the microspheres using the GST anchor. We compared the therapeutic efficacy of recombinant melittin released from PEGDA microspheres to melittin. We found that, when released by an activating enzyme, thrombin, recombinant melittin efficiently inhibits growth of the pathogenic bacterium Streptococcus pyogenes as effectively as melittin created by solid phase peptide synthesis. We conclude that a GST protein anchor can be used to immobilize functional protein to PEGDA microspheres and the protein will remain immobilized under physiological conditions until the protein is enzymatically released. PMID:23816641

Buhrman, Jason S; Cook, Laura C; Rayahin, Jamie E; Federle, Michael J; Gemeinhart, Richard A

2013-11-10

392

In-situ deposition of hydroxyapatite on graphene nanosheets  

PubMed Central

Graphene nanosheets were effectively functionalized by in-situ deposition of hydroxyaptite through a facile chemical precipitation method. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. The resulting hydroxyapatite functionalized graphene nanosheets were characterized by attenuated total reflection IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy and thermogravimetric analysis. These characterization techniques revealed the successful grafting of hydroxyapatite over well exfoliated graphene nanosheets without destroying their structure. PMID:25110359

Neelgund, Gururaj M.; Oki, Aderemi; Luo, Zhiping

2014-01-01

393

Domination of volumetric toughening by silver nanoparticles over interfacial strengthening of carbon nanotubes in bactericidal hydroxyapatite biocomposite.  

PubMed

In order to address the problem of bacterial infections in bone-substitution surgery, it is essential that bone replacement biomaterials are equipped with bactericidal components. This research aims to optimize the content of silver (Ag), a well-known antibacterial metal, in a multiwalled carbon nanotube (CNT) reinforced hydroxyapatite (HA) composite, to yield a bioceramic which can be used as an antibacterial and tough surface of bone replacement prosthesis. The bactericidal properties evaluated using Escherichia coli and Staphylococcus epidermidis indicate that CNT reinforcement supports growth of Gram negative E. coli bacteria (~8.5% more adhesion than pure HA); but showed a strong decrease of Gram positive S. epidermidis bacteria (~diminished to 66%) compared to that of pure HA. Small amounts of silver (2-5wt.%) already show a severe bactericidal effect when compared to that of HA-CNT (by 30% and ~60% respectively). MTT assay confirmed enhanced biocompatibility of L929 cells on HA-4wt.% CNT (~121%), HA-4wt.% CNT-1wt.% Ag (~124%) sample and HA-4wt.% CNT-2wt.% Ag (~100%) when compared to that of pure HA. The samples with higher silver content showed decreased biocompatibility (77% for HA-4wt.% CNT-5wt.% Ag sample and 73% for HA-4wt.% CNT-10wt.% Ag). Though reinforcement of 4wt.% CNT has shown an increase of fracture toughness by ~62%, silver reinforcement has shown enhancement of up to 244% (i.e. 3.43 times). Accordingly, isolation of toughening contribution indicates that volumetric toughening by silver dominates over interfacial strengthening contributed by CNTs towards enhanced fracture toughness of potential HA-Ag-CNT biocomposites. PMID:24268282

Herkendell, Katharina; Shukla, Vishnu Raj; Patel, Anup Kumar; Balani, Kantesh

2014-01-01

394

Early bone apposition in vivo on plasma-sprayed and electrochemically deposited hydroxyapatite coatings on titanium alloy.  

PubMed

Three different implants, bare Ti-6Al-4V alloy, Ti-6Al-4V alloy coated with plasma-sprayed hydroxyapatite (PSHA), and Ti-6Al-4V alloy coated with electrochemically deposited hydroxyapatite (EDHA), were implanted into canine trabecular bone for 6 h, 7, and 14 days, respectively. Environmental scanning electron microscopy study showed that PSHA coatings had higher bone apposition ratios than those exhibited by bare Ti-6Al-4V and EDHA coatings after 7 days; however, at 14 days after implantation, EDHA and PSHA coatings exhibited similar bone apposition ratios, much higher than that for bare Ti-6Al-4V. The ultrastructure of the bone/implant interface observed by transmission electron microscope showed that the earliest mineralization (6 h-7 days) was in the form of nano-ribbon cluster mineral deposits with a Ca/P atomic ratio lower than that of hydroxyapatite. Later-stage mineralization (7-14 days) resulted in bone-like tissue with the characteristic templating of self-assembled collagen fibrils by HA platelets. Though adhesion of EDHA coatings to Ti-6Al-4V substrate proved problematical and clearly needs to be addressed through appropriate manipulation of electrodepositon parameters, the finely textured microstructure of EDHA coatings appears to provide significant advantage for the integration of mineralized bone tissue into the coatings. PMID:16618502

Wang, Hao; Eliaz, Noam; Xiang, Zhou; Hsu, Hu-Ping; Spector, Myron; Hobbs, Linn W

2006-08-01

395

Linux-HA-Cluster Heartbeat mit DRBD Thomas Rhl  

E-print Network

Linux-HA-Cluster ­ Heartbeat mit DRBD Thomas Röhl 01. Oktober 2004 #12;01.10.04 Thomas.Roehl@rrze.uni-erlangen.de 2Linux-HA-Cluster Inhalt Was ist ein HA-Cluster? Vorbereiten des Projekts Hardware Software Simulation Persönliches Fazit #12;01.10.04 Thomas.Roehl@rrze.uni-erlangen.de 3Linux-HA-Cluster Was ist ein HA

Fiebig, Peter

396

Titanium dioxide reinforced hydroxyapatite coatings deposited by high velocity oxy-fuel (HVOF) spray.  

PubMed

Hydroxyapatite (HA) coatings with titania addition were produced by the high velocity oxy-fuel (HVOF) spray process. Mechanical properties of the as-sprayed coatings in terms of adhesive strength, shear strength and fracture toughness were investigated to reveal the effect of the titania reinforcement on HA. Qualitative phase analysis with X-ray diffraction (XRD) showed that mutual chemical reaction between TiO2 and HA, that formed CaTiO3 occurred during coating formation. Differential scanning calorimetry (DSC) analysis of the starting powders showed that the mutual chemical reaction temperature was approximately 1410 degrees C and the existence of TiO2 can effectively inhibit the decomposition of HA at elevated temperatures. The positive influence of TiO2 addition on the shear strength was revealed. The incorporation of 10 vol% TiO2 significantly improved the Young's modulus of HA coatings from 24.82 (+/- 2.44) GPa to 43.23 (+/- 3.20) GPa. It decreased to 38.51 (+/- 3.65) GPa as the amount of TiO2 increased to 20 vol%. However, the addition of TiO2 has a negative bias on the adhesive strength of HA coatings especially when the content of TiO2 reached 20 vol%. This is attributed to the weak chemical bonding and brittle phases existing at the splats' interface that resulted from mutual chemical reactions. The fracture toughness exhibited values of 0.48 (+/- 0.08) MPa m0.5, 0.60 (+/- 0.07) MPa m0.5 and 0.67 (+/- 0.06) MPa m0.5 for the HA coating, 10 vol% TiO2 blended HA coating and 20 vol% TiO2 blended HA coating respectively. The addition of TiO2 in HA coating with the amount of less than 20 vol% is suggested for satisfactory toughening effect in HVOF HA coating. PMID:11762858

Li, H; Khor, K A; Cheang, P

2002-01-01

397

Polyorganophosphazene microspheres for drug release: polymer synthesis, microsphere preparation, in vitro and in vivo naproxen release.  

PubMed

Microsphere preparation for naproxen slow release was investigated using two newly prepared biodegradable polyorganophosphazenes, derivatized at the phosphorus atoms with phenylalanine ethyl ester and imidazole at molar ratios of 71/29 and 80/20. The polymers were prepared by substitution of the chloride atoms of polydichlorophosphazene with a phenylalanine ethyl ester-imidazole mixture followed, after 7 or 48 h reaction, by the addition of excess imidazole. Three methods of microsphere preparation have been considered: spray-drying, emulsion/solvent evaporation and emulsion/solvent evaporation-extraction. Microparticles obtained by spray-drying were found to possess a narrow distribution size with a mean diameter of 2-5 microm. Their internal structure consisted of a porous or empty core depending upon the solvent used for the preparation. Furthermore the microspheres prepared with this technique rapidly released the entrapped naproxen independently of the used polymer, the drug loading or the preparation process. On the other hand microspheres prepared by solvent evaporation or solvent evaporation-extraction showed a distribution size ranging between 10 and 100 microm. By the appropriate choice of pH and solvent composition of the external phase, naproxen could be entrapped, in these microspheres, with a yield higher of 80%. The polymer composition dictates the in vitro release rate of naproxen from the particles, which was faster when the microspheres were prepared with the polymer at higher imidazole content. In vivo experiments, carried out by subcutaneous implantation in rats of microspheres prepared by solvent evaporation, demonstrated that a constant level of naproxen in plasma could be maintained up to 400 h at a suitable concentration for antinflammatory activity. PMID:9743444

Veronese, F M; Marsilio, F; Caliceti, P; De Filippis, P; Giunchedi, P; Lora, S

1998-03-31

398

Synthesis of mesoporous nano-hydroxyapatite by using zwitterions surfactant  

EPA Science Inventory

Mesoporous nano-hydroxyapatite (mn-HAP) was successfully synthesized via a novel micelle-templating method using lauryl dimethylaminoacetic acid as zwitterionic surfactant. The systematic use of such a surfactant in combination with microwave energy inputenables the precise contr...

399

Floating microspheres of cimetidine: formulation, characterization and in vitro evaluation.  

PubMed

The present study involves preparation and evaluation of floating microspheres with cimetidine as model drug for prolongation of gastric residence time. The microspheres were prepared by the solvent evaporation method using polymers hydroxypropylmethyl cellulose and ethyl cellulose. The shape and surface morphology of prepared microspheres were characterized by optical and scanning electron microscopy, respectively. In vitro drug release studies were performed and drug release kinetics was evaluated using the linear regression method. Effects of the stirring rate during preparation, polymer concentration, solvent composition and dissolution medium on the size of microspheres and drug release were also observed. The prepared microspheres exhibited prolonged drug release (approximately 8 h) and remained buoyant for > 10 h. The mean particle size increased and the drug release rate decreased at higher polymer concentration. No significant effect of the stirring rate during preparation on drug release was observed. In vitro studies demonstrated diffusion-controlled drug release from the microspheres. PMID:16375838

Srivastava, Anand Kumar; Ridhurkar, Devendra Narayanrao; Wadhwa, Saurabh

2005-09-01

400

Macrofungi associated with vegetation and soils at Ha Ha Tonka State Park, Missouri.  

PubMed

Fungi and vascular plant interactions are necessary components of natural community establishment, productivity and degradation. While many fungal species serve as decomposers of organic matter, others have evolved mutualistic or parasitic relationships with vascular plants. This research focused on characterizing associations among macrofungi, vascular plant communities and soils. Ha Ha Tonka State Park is in central Missouri and has a varying landscape with numerous natural community types that provide diverse habitats and microhabitats that are ideally suited to the investigation of fungal, floral and soil associations. Five communities sampled within the park included glades, open woodlands, flatwoods, closed-canopy forests and karst sinks. Permanent 0.01 ha. plots were surveyed in the 2006 and 2007 growing seasons. Surveys of plots and entire communities yielded 249 fungal taxa and approximately 265 floral taxa. Soils were analyzed to help define specific edaphic components of each community and used to associate soil attributes with plant and fungal communities. Forest communities contained the most ectomycorrhizal (ECM) fungi species. Karst sinks and glades had higher soil pH and phosphorus and fewer ectomycorrhizal fungi. Statistical analyses included non-metric multidimensional scaling, multiresponse permutation procedure and indicator species analysis. Indicator species were identified for flatwood, forest and karst communities, but results were inconclusive for glades and open woodlands. PMID:20943573

Crabtree, Christopher D; Keller, Harold W; Ely, Joseph S

2010-01-01