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1

Preparation of hollow hydroxyapatite microspheres.  

PubMed

The preparation of hollow hydroxyapatite (HA) microspheres as potential drug-delivery vehicles was investigated. A lithium-calcium-borate (10Li(2)O-15CaO-75B(2)O(3)) (mol%) glass, made by fusing the components at 1100 degrees C for 1 h, was ground to a powder and passed through a flame at approximately 1400 degrees Celsius to spheroidize the particles. The resulting glass microspheres (106-125 microm in diameter) were reacted in 0.25 M K(2)HPO(4) solution for 5 days at 37 degrees Celsius and pH 10-12, resulting in the formation of porous, hollow microspheres of a calcium phosphate (Ca-P) material with external diameters similar to those of the original glass particles. Heat treatment at 600 degrees Celsius for 4 h partially converted the Ca-P material to HA, as confirmed by X-ray diffraction, and also increased the strength of the hollow microspheres. PMID:16770549

Wang, Qing; Huang, Wenhai; Wang, Deping; Darvell, Brian W; Day, Delbert E; Rahaman, Mohamed N

2006-07-01

2

Modified composite microspheres of hydroxyapatite and poly(lactide-co-glycolide) as an injectable scaffold  

NASA Astrophysics Data System (ADS)

The compound of hydroxyapatite-poly(lactide-co-glycolide) (HA-PLGA) was prepared by ionic bond between HA and PLGA. HA-PLGA was more stable than the simple physical blend of hydroxyapatite and poly(lactide-co-glycolide) (HA/PLGA). The surface of HA-PLGA microsphere fabricated by an emulsion-solvent evaporation method was rougher than that of HA/PLGA microspheres. Moreover, surface HA content of HA-PLGA microspheres was more than that of HA/PLGA microspheres. In vitro mouse OCT-1 osteoblast-like cell culture results showed that the HA-PLGA microspheres clearly promoted osteoblast attachment, proliferation and alkaline phosphatase activity. It was considered that surface rich HA component and rough surface of HA-PLGA microsphere enhanced cell growth and differentiation. The good cell affinity of the HA-PLGA microspheres indicated that they could be used as an injectable scaffold for bone tissue engineering.

Hu, Xixue; Shen, Hong; Yang, Fei; Liang, Xinjie; Wang, Shenguo; Wu, Decheng

2014-02-01

3

Controlled release of amoxicillin from hydroxyapatite-coated poly(lactic-co-glycolic acid) microspheres  

Microsoft Academic Search

Negatively charged poly(lactic-co-glycolic acid) (PLGA) microspheres with an encapsulated hydrophilic antibiotic (amoxicillin) have been prepared by the solid-in-oil-in-water (s\\/o\\/w) method using the anionic surfactant, sodium dodecyl sulfate (SDS). Drug encapsulation efficiency is over 40%. Successful coating of hydroxyapatite (HA) on these negatively charged PLGA microspheres has been achieved by a dual constant composition method in 3–6 h. The HA-coated PLGA microspheres

Qingguo Xu; Jan T. Czernuszka

2008-01-01

4

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

5

Characterization of hollow hydroxyapatite/copper microspheres prepared from the reduction of copper-modified hydroxyapatite by glucose.  

PubMed

This study employed a co-precipitation method to synthesize copper-modified hydroxyapatite (HA) powders, where Cu(2+) ions had entered the structure of HA and occupied Ca(1) sites in the columns parallel to the c-axis. Through a hydrothermal treatment, hollow HA/copper (Cu(2)O and/or Cu) microspheres with core-shell structures were prepared in solutions containing glucose, sodium carbonate and sodium citrate. When prolonging the reduction time, Cu(2+) ions dissolved from copper-modified HA were reduced by glucose initially to Cu(+) ions and then to Cu atoms, which would precipitate as copper on the surface of HA. The formation of microspheres with hollow structures was explained by the Kirkendall effect which states that diffusion behaviors of ions were different for HA and copper precipitations. Hybrid HA/copper powders might find their applications in gas sensors, catalysts, electrodes and so on. PMID:21821600

Li, Chengfeng; Liang, Jiaqing; Niu, Jinye; Liu, Shuguang; Li, Guochang; Bai, Jiahai; Zhang, Aijuan; Ding, Rui

2011-01-01

6

Synthesis of hollow hybrid hydroxyapatite microspheres based on chitosan-poly(acrylic acid) microparticles.  

PubMed

Core-template-free hybrid hydroxyapatite (HA) hollow microspheres based on a chitosan-poly acrylic acid (CS-PAA) complex were prepared. The amine groups on chitosan can interact with the carboxyl groups of poly(acrylic acid) to form hollow microspheres. The hollow HA microspheres of about 1.0 microm are obtained by heterogeneous nucleation of HA on CS-PAA hollow spheres. Gelatin (Gel), acting as a novel cross-link agent, is introduced to bind the spheres of CS-PAA and HA. The forming mechanism of hollow spheres and the influencing factors on the size of microspheres are investigated. In addition, the role of Gel is elucidated in the forming process of the hollow hybrid sphere. PMID:19372618

Zhang, Haibin; Zhou, Kechao; Li, Zhiyou; Huang, Suping

2009-06-01

7

Preparation, characterization and in vitro gentamicin release of porous HA microspheres.  

PubMed

Hydroxyapatite (HA) microspheres with high porosities were successfully obtained using an improved ice-templated spray drying (ITSD) technique for drug delivery applications. Pore structures and pore sizes of microspheres have great impact on drug loading and release kinetics. Therefore, solvent types, polyvinyl alcohol (PVA) contents and solid loadings of suspensions were adjusted to control the pore structures and pore sizes. Microspheres with interconnected pore networks and aligned pore structures were obtained using camphene-based and tert-butyl alcohol (TBA)-based suspensions, respectively. With the increase of PVA contents in suspensions, the growth of sintering neck became more obvious and the surface of HA particles became smoother. The inner pore structures of microspheres transformed from uniformly distributed cellular pores to three-dimensional interconnected pore networks, with the increase of solid loadings in suspensions. Gentamicin was successfully loaded into porous HA microspheres. The drug loading percentage increased from 40.59 to 49.82% with the increase of porosity of HA microspheres. The release percentage during the initial 18 h increased from 48.72 to 65.68% with the transformation of pore structures from independent cellular pores (main diameter~3 ?m) to three-dimensional interconnected pore networks (main diameter>3 ?m). PMID:25491833

Yu, Min; Zhou, Kechao; Li, Zhiyou; Zhang, Dou

2014-12-01

8

Hollow hydroxyapatite microspheres as a device for controlled delivery of proteins.  

PubMed

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of Li(2)O-CaO-B(2)O(3) glass (106-150 ?m) in K(2)HPO(4) 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 K(2)HPO(4) 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 m(2)/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; Rahaman, Mohamed N; Day, Delbert E; Brown, Roger F

2011-03-01

9

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

10

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

11

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

PubMed

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 and 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

2013-05-01

12

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

13

Enhancing Alendronate Release from a Novel PLGA\\/Hydroxyapatite Microspheric System for Bone Repairing Applications  

Microsoft Academic Search

Purpose  The goal of this study was to exploit the multifunction of PLGA based microsphere as efficient alendronate delivery and also\\u000a as potential injectable cell carrier for bone-repairing therapeutics.\\u000a \\u000a \\u000a \\u000a Materials and Methods  Novel poly (lactic-co-glycolic acid) (PLGA)-hybridizing -hydroxyapatite (HA) microspheres loaded with bisphosphonate-based\\u000a osteoporosis preventing drugs, alendronate (AL), are prepared with solid\\/oil\\/water (s\\/o\\/w) or water\\/oil\\/water (w\\/o\\/w) technique.\\u000a Macrophage resistance was evaluated by

Xuetao Shi; Yingjun Wang; Li Ren; Yihong Gong; Dong-An Wang

2009-01-01

14

Hydroxyapatite/polyurethane scaffold incorporated with drug-loaded ethyl cellulose microspheres for bone regeneration.  

PubMed

The purpose of this study is to explore and develop biodegradable scaffold for bone regeneration or tissue engineering with the capacity of controlled drug delivery. Ceftazidime as a model drug was encapsulated in ethyl cellulose (EC) microspheres, which were subsequently incorporated in a hydroxyapatite/polyurethane (HA/PU) composite scaffold to generate an antibiotic drug delivery system. HA/PU scaffolds had an interconnected pore network with an average porosity of about 83%. The presence of microspheres in the composite scaffolds was confirmed by scanning electron microscopy. The drug-loaded EC microspheres were uniformly distributed in the HA/PU scaffold matrix and showed no significant effect on the pore structure of the scaffold. Incorporation of microspheres into scaffolds significantly reduced the initial burst release, and the system exhibited a sustained release of the model drug for up to 60 days. Moreover, the scaffold with drug-loaded microspheres was proved to be an effective drug delivery system with good cytocompatibility and antibacterial properties. The novel drug-loaded microsphere/scaffold composites developed in this study are promising to serve as vehicles for controlled drug delivery in bone regeneration or bone tissue engineering. PMID:20665683

Liu, Haohuai; Zhang, Li; Shi, Pujiang; Zou, Qin; Zuo, Yi; Li, Yubao

2010-10-01

15

Polymer assisted hydroxyapatite microspheres suitable for biomedical application.  

PubMed

Hollow Microspheres of hydroxyapatite-polymer composite can be used as carriers in drug delivery and fillers in tissue engineering. Based on the concept of soft chemistry, a battery of technique is available in the literature to synthesize hollow microspheres, however, an economically viable synthesis route, having good control over the microarchitect and easy to be scaled up, is yet to be developed. Polymer matrix mediated synthesis of inorganic nanoparticles is known to synthesize nanoparticles with controlled morphology and dimensions. It is termed as biomimetic synthesis. Integrating the biomimetic synthesis of nano-particles and spray drying techniques, a novel process of producing hydroxyapatite-polymer composite hollow microspheres is briefly discussed here. PMID:17952563

Sinha, A; Mishra, T; Ravishankar, N

2008-05-01

16

Growth of hydroxyapatite coatings on biodegradable polymer microspheres.  

PubMed

Mineral-coated microspheres were prepared via a bioinspired, heterogeneous nucleation process at physiological temperature. Poly(d,l-lactide-co-glycolide) (PLG) microspheres were fabricated via a water-in-oil-in-water emulsion method and were mineral-coated via incubation in a modified simulated body fluid (mSBF). X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy with associated energy-dispersive X-ray spectroscopy confirmed the presence of a continuous mineral coating on the microspheres. The mineral grown on the PLG microsphere surface has characteristics analogous to those of bone mineral (termed "bonelike" mineral), with a carbonate-containing hydroxyapatite phase and a porous structure of platelike crystals at the nanometer scale. The assembly of mineral-coated microspheres into aggregates was observed when microsphere concentrations above 0.50 mg/mL were incubated in mSBF for 7 days, and the size of the aggregates was dependent on the microsphere concentration in solution. In vitro mineral dissolution studies performed in Tris-buffered saline confirmed that the mineral formed was resorbable. A surfactant additive (Tween 20) was incorporated into mSBF to gain insight into the mineral growth process, and Tween 20 not only prevented aggregation but also significantly inhibited mineral formation and influenced the characteristics of the mineral formed on the surface of PLG microspheres. Taken together, these findings indicate that mineral-coated PLG microspheres or mineral-coated microsphere aggregates can be synthesized in a controllable manner using a bioinspired process. These materials may be useful in a range of applications, including controlled drug delivery and biomolecule purification. PMID:20161578

Jongpaiboonkit, Leenaporn; Franklin-Ford, Travelle; Murphy, William L

2009-07-01

17

Strength of hollow hydroxyapatite microspheres prepared by a glass conversion process.  

PubMed

Hollow hydroxyapatite (HA) microspheres (diameter = 100-800 microm) were prepared by reacting solid Li(2)O-CaO-B(2)O(3) glass spheres in 0.25 M K(2)HPO(4) solution at 37 degrees C. The influence of subsequent heating on the microstructure, surface area, and compressive strength of the HA microspheres was evaluated using scanning electron microscopy, the BET method, and nano-mechanical testing. The surface area and rupture strength of the as-prepared microspheres were 135 m(2)/g and 1.6 +/- 0.6 MPa, respectively. On heating for 8 h at 600 degrees C, the surface area decreased to 27 m(2)/g, but there was no increase in the compressive strength (1.7 +/- 0.4 MPa). Heating to 800 degrees C (8 h) resulted in a marked decrease in the surface area (to 2.6 m(2)/g) and a sharp increase in the compressive strength (to >35 +/- 8 MPa). These hollow HA microspheres may be useful as devices for drug or protein growth factor delivery or as scaffolds for engineered tissues. PMID:18704649

Huang, Wenhai; Rahaman, Mohamed N; Day, Delbert E; Miller, Brad A

2009-01-01

18

Hydroxyapatite-armored poly(?-caprolactone) microspheres and hydroxyapatite microcapsules fabricated via a Pickering emulsion route.  

PubMed

Hydroxyapatite (HAp) nanoparticle-armored poly(?-caprolactone) (PCL) microspheres were fabricated via a "Pickering-type" emulsion solvent evaporation method in the absence of any molecular surfactants. It was clarified that the interaction between carbonyl/carboxylic acid groups of PCL and the HAp nanoparticles at an oil-water interface played a crucial role in the preparation of the stable Pickering-type emulsions and the HAp nanoparticle-armored microspheres. The HAp nanoparticle-armored PCL microspheres were characterized in terms of size, size distribution, morphology, and chemical compositions using scanning electron microscopy, laser diffraction, energy dispersive X-ray microanalysis, and thermogravimetric analysis. The presence of HAp nanoparticles at the surface of the microspheres was confirmed by scanning electron microscopy and energy dispersive X-ray microanalysis. Pyrolysis of the PCL cores led to the formation of the corresponding HAp hollow microcapsules. PMID:22364710

Fujii, Syuji; Okada, Masahiro; Nishimura, Taiki; Maeda, Hayata; Sugimoto, Tatsuya; Hamasaki, Hiroyuki; Furuzono, Tsutomu; Nakamura, Yoshinobu

2012-05-15

19

Adhesion of hollow calcium-deficient hydroxyapatite microspheres onto titanium.  

PubMed

Microcapsules containing active drugs, e.g. an antimicrobial agent, with a hydroxyapatite (HAp) shell are expected to prevent infection and to improve osseointegration simultaneously when used as implant materials. This study was conducted to investigate the effects of etching with hydrofluoric acid (HF) to change the surface morphology of titanium in cases of adhesion of calcium-deficient HAp microspheres onto titanium. The microspheres were mixed with Hanks' balanced salt solution (HBSS) to prepare slurry; the slurry was then put between two titanium disks that had been etched and kept soaking in HBSS for seven days at 310 K. The coverage and the degree of adherence of the microsphere were evaluated using electron probe microanalysis. The etching at an HF concentration of 0.10 mol/L caused the greatest adhesion. Changing the temperature between 303 and 323 K showed a tendency for the degree of adherence to increase. PMID:20019421

Kimura, Isao; Kanatani, Mitsugu; Watanabe, Kouichi

2009-11-01

20

Effect of Process Variables on the Microstructure of Hollow Hydroxyapatite Microspheres Prepared by a Glass Conversion Method.  

PubMed

Solid microspheres (diameter = 106-150 ?m) of a Li(2)O-CaO-B(2)O(3) glass were reacted in a K(2)HPO(4) solution to form hollow hydroxyapatite (HA) microspheres. The effect of the temperature (25°-60°C), K(2)HPO(4) concentration (0.01-0.25M), and pH (9-12) of the solution on the diameter (d) of the hollow core normalized to the diameter (D) of the HA microspheres, the surface area, and the pore size of the microsphere wall was studied. The statistically significant process variables that influenced these microstructural characteristics were evaluated using a factorial design approach. While the pH had little effect, the concentration of the solution had a marked effect on d/D, surface area, and pore size, whereas temperature markedly influenced d/D and pore size, but not the surface area. The largest hollow core size (d/D value ? 0.6) was obtained at the lowest temperature (25°C) or the lowest K(2)HPO(4) concentration (0.02M), while microspheres with the highest surface area (140 m(2)/g), with pores of size 10-12 nm were obtained at the highest concentration (0.25M). The consequences of these results for potential application of these hollow HA microspheres as devices for local delivery of proteins, such as drugs or growth factors, are discussed. PMID:21892226

Fu, Hailuo; Rahaman, Mohamed N; Day, Delbert E

2010-10-01

21

Effect of Process Variables on the Microstructure of Hollow Hydroxyapatite Microspheres Prepared by a Glass Conversion Method  

PubMed Central

Solid microspheres (diameter = 106–150 ?m) of a Li2O–CaO–B2O3 glass were reacted in a K2HPO4 solution to form hollow hydroxyapatite (HA) microspheres. The effect of the temperature (25°–60°C), K2HPO4 concentration (0.01–0.25M), and pH (9–12) of the solution on the diameter (d) of the hollow core normalized to the diameter (D) of the HA microspheres, the surface area, and the pore size of the microsphere wall was studied. The statistically significant process variables that influenced these microstructural characteristics were evaluated using a factorial design approach. While the pH had little effect, the concentration of the solution had a marked effect on d/D, surface area, and pore size, whereas temperature markedly influenced d/D and pore size, but not the surface area. The largest hollow core size (d/D value ? 0.6) was obtained at the lowest temperature (25°C) or the lowest K2HPO4 concentration (0.02M), while microspheres with the highest surface area (140 m2/g), with pores of size 10–12 nm were obtained at the highest concentration (0.25M). The consequences of these results for potential application of these hollow HA microspheres as devices for local delivery of proteins, such as drugs or growth factors, are discussed. PMID:21892226

Fu, Hailuo; Rahaman, Mohamed N.; Day, Delbert E.

2011-01-01

22

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

23

Encapsulation and osteoinduction of human periodontal ligament fibroblasts in chitosan-hydroxyapatite microspheres.  

PubMed

Periodontal ligament cells play a crucial role in the regeneration of periodontal tissues and an undifferentiated mesenchymal cell subset is thought to exist within this population. The aim of this study was to assess the osteogenic differentiation potential of human periodontal ligament fibroblasts (hPDLFs) in three dimensional (3D)-osteogenic culture environment following encapsulation in chitosan-hydroxyapatite (C/HA) microspheres with the size range of 350-450 microm. Human PDLF cultures were established and three experimental groups were formed: (i) two-dimensional (2D)-culture as single cell monolayer, (ii) 3D-static culture of C/HA encapsulated hPDLFs, and (iii) 3D-dynamic culture of C/HA encapsulated hPDLFs in a rotating wall vessel bioreactor. The cells were cultured in standard culture medium supplemented with beta-glycerophosphate, dexamethasone, and ascorbic acid. After 21 days, immunohistochemistry was performed using antibodies against osteonectin, osteopontin, bone-sialoprotein, and osteocalcin as osteogenic differentiation markers. Phase-contrast and scanning electron microscopy observations were used for histological and morphological evaluation. The combined effects of osteoinductive medium and HA-containing composite microsphere material on encapsulated hPDLFs resulted in the transformation of a considerable portion of the cells into osteoblastic lineage at the end of the experiments. Results demonstrate the ability of hPDLFs to undergo osteogenic differentiation upon induction in vitro, both under 2D and 3D culture conditions. C/HA microspheres in microgravity bioreactor may serve as a suitable 3D environment to support the osteogenic differentiation of human PDLFs, in vitro. PMID:17335028

Inanç, Bülend; Eser Elçin, A; Koç, Aysel; Balo?, Köksal; Parlar, Ate?; Murat Elçin, Y

2007-09-15

24

Factors influencing the deposition of hydroxyapatite coating onto hollow glass microspheres.  

PubMed

Hydroxyapatite (HA) and HA coated microcarriers for cell culture and delivery have attracted more attention recently, owing to the rapid progress in the field of tissue engineering. In this research, a dense and uniform HA coating with the thickness of about 2 ?m was successfully deposited on hollow glass microspheres (HGM) by biomimetic process. The influences of SBF concentration, immersion time, solid/liquid ratio and activation of HGM on the deposition rate and coating characteristics were discussed. X-ray diffraction (XRD) and Fourier transform infrared spectrum (FTIR) analyses revealed that the deposited HA is poorly crystalline. The thickness of HA coating showed almost no increase after immersion in 1.5SBF for more than 15 days with the solid/liquid ratio of 1:150. At the same time, SBF concentration, solid/liquid ratio and activation treatment played vital roles in the formation of HA coating on HGM. This poorly crystallized HA coated HGM could have potential use as microcarrier for cell culture. PMID:23623091

Jiao, Yan; Xiao, Gui-Yong; Xu, Wen-Hua; Zhu, Rui-Fu; Lu, Yu-Peng

2013-07-01

25

Hydroxyapatite nanoparticles as particulate emulsifier: fabrication of hydroxyapatite-coated biodegradable microspheres.  

PubMed

Hydroxyapatite (HAp) nanoparticle-coated micrometer-sized poly(l-lactic acid) (PLLA) microspheres were fabricated via a "Pickering-type" emulsion route in the absence of any molecular surfactants. Stable oil-in-water emulsions were prepared using 40 nm HAp nanoparticles as a particulate emulsifier and a dichloromethane (CH(2)Cl(2)) solution of PLLA as an oil phase. It was clarified that the interaction between carbonyl/carboxylic acid groups of PLLA and the HAp nanoparticles at the CH(2)Cl(2)-water interface played a crucial role to prepare the stable Pickering-type emulsion. The HAp nanoparticle-coated PLLA microspheres were fabricated by the evaporation of CH(2)Cl(2) from the emulsion and characterized in terms of size, particle size distribution, and morphology using scanning/transmission electron microscopes. Scanning electron microscopy study and ultrathin cross section observation using transmission electron microscopy confirmed adsorption of the HAp nanoparticles only at the surface of the PLLA microspheres. Cell-adhesion experiments suggested the HAp nanoparticles on the surface of the PLLA microspheres promoted the cell adhesion and spreading. PMID:19514753

Fujii, Syuji; Okada, Masahiro; Sawa, Hidekatsu; Furuzono, Tsutomu; Nakamura, Yoshinobu

2009-09-01

26

Hollow carbonated hydroxyapatite microspheres with mesoporous structure: hydrothermal fabrication and drug delivery property.  

PubMed

Hollow carbonated hydroxyapatite microspheres with mesoporous structure (HCHAs) have been fabricated by using calcium carbonated microspheres as sacrificial templates according to the following routes: (i) the in situ deposit of carbonated hydroxyapatite on the surfaces of CaCO3 microspheres by hydrothermal method and (ii) the removal of CaCO3 by chemical etching. The HCHAs consist of a hollow core and a mesoporous shell. Interestingly, the shell of the microspheres is constructed by carbonated hydroxyapatite nanoplates as building blocks. Moreover, these nanoplates are composed of many smaller nanoparticles with different crystal orientations, and the mesopores exist among these nanoparticles. The HCHAs exhibit the high drug-loading capacity and sustained drug release property, suggesting that the hierarchically porous microspheres have great potentials for bone-implantable drug-delivery applications. PMID:23706197

Guo, Ya-Jun; Wang, Ying-Ying; Chen, Ting; Wei, Yi-Ting; Chu, Lian-Feng; Guo, Ya-Ping

2013-08-01

27

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

PubMed Central

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) 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/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

2013-01-01

28

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

29

BMP2-loaded hollow hydroxyapatite microspheres exhibit enhanced osteoinduction and osteogenicity in large bone defects  

PubMed Central

The regeneration of large bone defects is an osteoinductive, osteoconductive, and osteogenic process that often requires a bone graft for support. Limitations associated with naturally autogenic or allogenic bone grafts have demonstrated the need for synthetic substitutes. The present study investigates the feasibility of using novel hollow hydroxyapatite microspheres as an osteoconductive matrix and a carrier for controlled local delivery of bone morphogenetic protein 2 (BMP2), a potent osteogenic inducer of bone regeneration. Hollow hydroxyapatite microspheres (100±25 ?m) with a core (60±18 ?m) and a mesoporous shell (180±42 m2/g surface area) were prepared by a glass conversion technique and loaded with recombinant human BMP2 (1 ?g/mg). There was a gentle burst release of BMP2 from microspheres into the surrounding phosphate-buffered saline in vitro within the initial 48 hours, and continued at a low rate for over 40 days. In comparison with hollow hydroxyapatite microspheres without BMP2 or soluble BMP2 without a carrier, BMP2-loaded hollow hydroxyapatite microspheres had a significantly enhanced capacity to reconstitute radial bone defects in rabbit, as shown by increased serum alkaline phosphatase; quick and complete new bone formation within 12 weeks; and great biomechanical flexural strength. These results indicate that BMP2-loaded hollow hydroxyapatite microspheres could be a potential new option for bone graft substitutes in bone regeneration. PMID:25609957

Xiong, Long; Zeng, Jianhua; Yao, Aihua; Tu, Qiquan; Li, Jingtang; Yan, Liang; Tang, Zhiming

2015-01-01

30

BMP2-loaded hollow hydroxyapatite microspheres exhibit enhanced osteoinduction and osteogenicity in large bone defects.  

PubMed

The regeneration of large bone defects is an osteoinductive, osteoconductive, and osteogenic process that often requires a bone graft for support. Limitations associated with naturally autogenic or allogenic bone grafts have demonstrated the need for synthetic substitutes. The present study investigates the feasibility of using novel hollow hydroxyapatite microspheres as an osteoconductive matrix and a carrier for controlled local delivery of bone morphogenetic protein 2 (BMP2), a potent osteogenic inducer of bone regeneration. Hollow hydroxyapatite microspheres (100±25 ?m) with a core (60±18 ?m) and a mesoporous shell (180±42 m(2)/g surface area) were prepared by a glass conversion technique and loaded with recombinant human BMP2 (1 ?g/mg). There was a gentle burst release of BMP2 from microspheres into the surrounding phosphate-buffered saline in vitro within the initial 48 hours, and continued at a low rate for over 40 days. In comparison with hollow hydroxyapatite microspheres without BMP2 or soluble BMP2 without a carrier, BMP2-loaded hollow hydroxyapatite microspheres had a significantly enhanced capacity to reconstitute radial bone defects in rabbit, as shown by increased serum alkaline phosphatase; quick and complete new bone formation within 12 weeks; and great biomechanical flexural strength. These results indicate that BMP2-loaded hollow hydroxyapatite microspheres could be a potential new option for bone graft substitutes in bone regeneration. PMID:25609957

Xiong, Long; Zeng, Jianhua; Yao, Aihua; Tu, Qiquan; Li, Jingtang; Yan, Liang; Tang, Zhiming

2015-01-01

31

Evaluation of bone regeneration in implants composed of hollow HA microspheres loaded with TGF– 1 in a rat calvarial defect model  

PubMed Central

Implants that serve simultaneously as an osteoconductive matrix and as a device for local growth factor delivery may be required for optimal bone regeneration in some applications. In the present study, hollow hydroxyapatite (HA) microspheres (106–150 ?m) in the form of three-dimensional (3D) scaffolds or individual (loose) microspheres were created using a glass conversion process. The capacity of the implants, with or without transforming growth factor- 1 (TGF- 1), to regenerate bone in a rat calvarial defect model was compared. The 3D scaffolds supported the proliferation and alkaline phosphatase activity of osteogenic MLO-A5 cells in vitro, showing their cytocompatibility. Release of TGF- 1 from the 3D scaffolds into phosphate-buffered saline ceased after 2–3 days when 30% of the growth factor was released. Bone regeneration in the 3D scaffolds and the individual microspheres increased with time from 6 to 12 weeks, but it was significantly higher (23%) in the individual microspheres than in the 3D scaffolds (15%) after 12 weeks. Loading with TGF-?1 (5 ?g/defect) enhanced bone regeneration in the 3D scaffolds and individual microspheres after 6 weeks, but had little effect after 12 weeks. 3D scaffolds and individual microspheres with larger HA diameter (150–250 ?m) showed better ability to regenerate bone. Based on these results, implants composed of hollow HA microspheres show promising potential as an osteoconductive matrix for local growth factor delivery in bone regeneration. PMID:23168225

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

2012-01-01

32

Evaluation of bone regeneration in implants composed of hollow HA microspheres loaded with transforming growth factor ?1 in a rat calvarial defect model.  

PubMed

Implants that serve simultaneously as an osteoconductive matrix and as a device for local growth factor delivery may be required for optimal bone regeneration in some applications. In the present study, hollow hydroxyapatite (HA) microspheres (106-150?m) in the form of three-dimensional (3-D) scaffolds or individual (loose) microspheres were created using a glass conversion process. The capacity of the implants, with or without transforming growth factor ?1 (TGF-?1), to regenerate bone in a rat calvarial defect model was compared. The 3-D scaffolds supported the proliferation and alkaline phosphatase activity of osteogenic MLO-A5 cells in vitro, showing their cytocompatibility. Release of TGF-?1 from the 3-D scaffolds into phosphate-buffered saline ceased after 2-3 days when ?30% of the growth factor was released. Bone regeneration in the 3-D scaffolds and the individual microspheres increased with time from 6 to 12 weeks, but it was significantly higher (23%) in the individual microspheres than in the 3-D scaffolds (15%) after 12 weeks. Loading with TGF-?1 (5?g per defect) enhanced bone regeneration in the 3-D scaffolds and individual microspheres after 6 weeks, but had little effect after 12 weeks. 3-D scaffolds and individual microspheres with larger HA diameter (150-250?m) showed better ability to regenerate bone. Based on these results, implants composed of hollow HA microspheres show promising potential as an osteoconductive matrix for local growth factor delivery in bone regeneration. PMID:23168225

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

2013-03-01

33

In situ fabrication of hollow hydroxyapatite microspheres by phosphate solution immersion  

NASA Astrophysics Data System (ADS)

Hollow hydroxyapatite (HAP) microspheres with pores on their surfaces were prepared by converting Li 2O-CaO-B 2O 3 (LCB) glass microspheres in phosphate solution. The structure, phase composition, surface morphology, and porosity of the hollow HAP microspheres were characterized by SEM, SEM-EDS, XRD, FTIR, ICP-AES, and N 2 adsorption-desorption techniques. The formation and conversion mechanism of the hollow HAP microspheres during immersion process were discussed. The as-prepared microspheres consisted of calcium deficient carbonated hydroxyapatite, which is biomimetic. FTIR spectra indicated that the resulting apatite were B-type CO 3HAP, in which carbonate ions occupied the phosphate sites. After 600 °C heating treatment, hollow microspheres were completely composed of calcium deficient hydroxyapatite crystals including CO32-. The pore size distribution of the as-prepared hollow HAP microspheres were mainly the mesopores in the range of 2-40 nm with the pore volume 0.5614 cm 3/g, and the mean pore size 10.5 nm, respectively. The results confirmed that LCB glass were transformed to hydroxyapatite without changing the external shape and dimension of the original glass object and the resulting microspheres possessed good hollow structures. Once immersed in phosphate solution, Ca-P-OH hydrates were in situ formed on the surface of the glass and precipitated in the position occupied by Ca 2+, while the pores were formed in the position occupied by Li + and B 3+. These hollow HAP microspheres with such structures may be used as promising drug delivery devices.

Wang, Yingchun; Yao, Aihua; Huang, Wenhai; Wang, Deping; zhou, Jun

2011-07-01

34

A method to fabricate hydroxyapatite\\/poly(lactic acid) microspheres intended for biomedical application  

Microsoft Academic Search

The interaction between organic and inorganic materials enables one to fabricate inorganic\\/organic microsphere composites. In a novel microemulsion method, we have prepared surfactant-free poly(lactic acid) (PLA)\\/hydroxyapatite (HAp) microspheres by using the interfacial interaction between inorganic and organic materials, because surfactants are undesireble materials for biomedical applications due to their non-biodegradability. The studies that varied the ion concentrations in oil\\/water microemulsions

Fukue Nagata; Tatsuya Miyajima; Yoshiyuki Yokogawa

2006-01-01

35

Controlled release of bovine serum albumin from hydroxyapatite microspheres for protein delivery system  

Microsoft Academic Search

Desorption behavior of a model protein (bovine serum albumin, BSA) on commercial hydroxyapatite (HAp) microspheres and its control were investigated for protein delivery system. The desorption behavior related strongly to the phosphate concentration in phosphate buffer solution: the amount of desorbed BSA increased when the phosphate concentration increased. In physiological buffer solution, which contains 10mM phosphate, the initial burst release

Yaowalak Boonsongrit; Hiroya Abe; Kazuyoshi Sato; Makio Naito; Masahiro Yoshimura; Hideki Ichikawa; Yoshinobu Fukumori

2008-01-01

36

Effects of technological parameters on the microstructure of laser remelted hydroxyapatite (HA) coatings  

Microsoft Academic Search

In this paper, the influence of different laser power and scanning speed on the microstructure of laser remelted as-sprayed hydroxyapatite (HA) coatings was studied and the optimum technological parameters were obtained. The morphologies, elements and phase analysis of both sprayed and remelted coatings were examined by means of electron probe microanalysis, x-ray diffraction and so on. The results show that

Chuanzhong Chen; Diangang Wang; Quanhe Bao; Tingquan Lei

2006-01-01

37

Chlorhexidine-loaded hydroxyapatite microspheres as an antimicrobial delivery system and its effect on in vivo osteo-conductive properties.  

PubMed

Hydroxyapatite (HA) has been investigated as a delivery system for antimicrobial and antibacterial agents to simultaneously stimulate bone regeneration and prevent infection. Despite evidence supporting the bactericidal efficiency of these HA carriers, few studies have focused on the effect of this association on bone regeneration. In this work, we evaluated the physico-chemical properties of hydroxyapatite microspheres loaded with chlorhexidine (CHX) at two different concentrations, 0.9 and 9.1 [Formula: see text], and characterized their effects on in vitro osteoblast viability and bone regeneration. Ultraviolet-visible spectroscopy, scanning and transmission electron microscopy associated with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to characterize the association of CHX and HA nanoparticles. The high CHX loading dose induced formation of organic CHX plate-like aggregates on the HA surface, whereas a Langmuir film was formed at the low CHX surface concentration. Quantitative evaluation of murine osteoblast viability parameters, including adhesion, mitochondrial activity and membrane integrity of cells exposed to HA/CHX extracts, revealed a cytotoxic effect for both loading concentrations. Histomorphological analysis upon implantation into the dorsal connective tissues and calvaria of rats for 7 and 42 days showed that the high CHX concentration induced the infiltration of inflammatory cells, resulting in retarded bone growth. Despite a strong decrease in in vitro cell viability, the low CHX loading dose did not impair the biocompatibility and osteoconductivity of HA during bone repair. These results indicate that high antimicrobial doses may activate a strong local inflammatory response and disrupt the long-term osteoconductive properties of CHX-HA delivery systems. PMID:25791461

Soriano-Souza, Carlos Alberto; Rossi, Andre L; Mavropoulos, Elena; Hausen, Moema A; Tanaka, Marcelo N; Calasans-Maia, Mônica D; Granjeiro, Jose M; Rocha-Leão, Maria Helena M; Rossi, Alexandre M

2015-04-01

38

Porous PLGA microspheres with BMP2 releasing polyphosphate-functionalized nano-hydroxyapatite for enhanced bone regeneration  

Microsoft Academic Search

We report on bone-regenerative porous microspheres surface-decorated with polyphosphate-functionalized nano-hydroxyapatite (n-HAp) that can controllably release bone morphogenetic protein-2 (BMP-2). n-HAp was immobilized onto the pore surface of microspheres and could control the loading and the release of BMP-2.

Ahn Na Koo; Sang Cheon Lee

2011-01-01

39

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

PubMed

Inspired by coralline-derived hydroxyapatite, we designed a methodological route to synthesize carbonated-hydroxyapatite microspheres from the conversion of CaCO3 spherulite templates within a collagen matrix under mild conditions and thus constructed the composite hydrogel of collagen/hydroxyapatite-microspheres. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) were employed to confirm the successful generation of the carbonated hydroxyapatite phase originating from CaCO3, and the ratios of calcium to phosphate were tracked over time. Variations in the weight portion of the components in the hybrid gels before and after the phase transformation of the CaCO3 templates were identified via thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) shows these composite hydrogels have a unique multiscale microstructure consisting of a collagen nanofibril network and hydroxyapatite microspheres. The relationship between the hydroxyapatite nanocrystals and the collagen fibrils was revealed by transmission electron microscopy (TEM) in detail, and the selected area electron diffraction (SAED) pattern further confirmed the results of the XRD analyses which show the typical low crystallinity of the generated hydroxyapatite. This smart synthesis strategy achieved the simultaneous construction of microscale hydroxyapatite particles and collagen fibrillar hydrogel, and appears to provide a novel route to explore an advanced functional hydrogel materials with promising potentials for applications in bone tissue engineering and reconstruction medicine. PMID:25719911

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

2015-03-20

40

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

41

Hierarchical hollow hydroxyapatite microspheres: microwave-assisted rapid synthesis by using pyridoxal-5'-phosphate as a phosphorus source and application in drug delivery.  

PubMed

Three-dimensional (3D) hydroxyapatite (HAP) hierarchical nanostructures, in particular hollow nanostructures, have attracted much attention owing to their potential applications in many biomedical fields. Herein, we report a rapid microwave-assisted hydrothermal synthesis of a variety of hydroxyapatite hierarchical nanostructures that are constructed by the self-assembly of nanorods or nanosheets as the building blocks, including HAP nanorod-assembled hierarchical hollow microspheres (HA-NRHMs), HAP nanorod-assembled hierarchical microspheres (HA-NRMs), and HAP nanosheet-assembled hierarchical microspheres (HA-NSMs) by using biocompatible biomolecule pyridoxal-5'-phosphate (PLP) as a new organic phosphorus source. The PLP molecules hydrolyze to produce phosphate ions under microwave-hydrothermal conditions, and the phosphate ions react with calcium ions to form HAP nanorods or nanosheets; then, these nanorods or nanosheets self-assemble to form 3D HAP hierarchical nanostructures. The preparation method reported herein is time-saving, with microwave heating times as short as 5?min. The HA-NRHMs consist of HAP nanorods as the building units, with an average diameter of about 50?nm. The effects of the experimental conditions on the morphology and crystal phase of the products are investigated. The hydrolysis of PLP under microwave-hydrothermal conditions and the important role of PLP in the formation of 3D HAP hierarchical nanostructures are investigated and a possible formation mechanism is proposed. The products are explored for potential applications in protein adsorption and drug delivery. Our experimental results indicate that the HA-NRHMs have high drug/protein-loading capacity and sustained drug-release behavior. Thus, the as-prepared HA-NRHMs are promising for applications in drug delivery and protein adsorption. PMID:23554329

Zhao, Xin-Yu; Zhu, Ying-Jie; Qi, Chao; Chen, Feng; Lu, Bing-Qiang; Zhao, Jing; Wu, Jin

2013-06-01

42

Porous nano-HA\\/collagen\\/PLLA scaffold containing chitosan microspheres for controlled delivery of synthetic peptide derived from BMP2  

Microsoft Academic Search

It is advantageous to incorporate controlled growth factor delivery into tissue engineering strategies. The purpose of the present study was to develop a novel tissue engineering scaffold with the capability of controlled releasing BMP-2-derived synthetic peptide. Porous nano-hydroxyapatite\\/collagen\\/poly(L-lactic acid)\\/chitosan microspheres (nHAC\\/PLLA\\/CMs) composite scaffolds containing different quantities of chitosan microspheres (CMs) were prepared by a thermally induced phase separation method. Dioxane

Xufeng Niu; Qingling Feng; Mingbo Wang; Xiaodong Guo; Qixin Zheng

2009-01-01

43

Characterization of Polymeric Solutions as Injectable Vehicles for Hydroxyapatite Microspheres  

Microsoft Academic Search

A polymeric solution and a reinforcement phase can work as an injectable material to fill up bone defects. However, the properties\\u000a of the solution should be suitable to enable the transport of that extra phase. Additionally, the use of biocompatible materials\\u000a is a requirement for tissue regeneration. Thus, we intended to optimize a biocompatible polymeric solution able to carry hydroxyapatite

Serafim M. Oliveira; Isabel F. Almeida; Paulo C. Costa; Cristina C. Barrias; M. Rosa Pena Ferreira; M. Fernanda Bahia; Mário A. Barbosa

2010-01-01

44

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

45

Hollow hydroxyapatite microspheres/chitosan composite as a sustained delivery vehicle for rhBMP-2 in the treatment of bone defects.  

PubMed

Composite scaffold comprised of hollow hydroxyapatite (HA) and chitosan (designated hHA/CS) was prepared as a delivery vehicle for recombinating human bone morphogenetic protein-2 (rhBMP-2). The in vitro and in vivo biological activities of rhBMP2 released from the composite scaffold were then investigated. The rhBMP-2 was firstly loaded into the hollow HA microspheres, and then the rhBMP2-loaded HA microspheres were further incorporated into the chitosan matrix. The chitosan not only served to bind the HA microspheres together and kept them at the implant site, but also effectively modified the release behavior of rhBMP-2. The in vitro release and bioactivity analysis confirmed that the rhBMP2 could be loaded and released from the composite scaffolds in bioactive form. In addition, the composite scaffolds significantly reduced the initial burst release of rhBMP2, and thus providing prolonged period of time (as long as 60 days) compared with CS scaffolds. In vivo bone regenerative potential of the rhBMP2-loaded composite scaffolds was evaluated in a rabbit radius defect model. The results revealed that the rate of new bone formation in the rhBMP2-loaded hHA/CS group was higher than that in both negative control and rhBMP2-loaded CS group. These observations suggest that the hHA/CS composite scaffold would be effective and feasible as a delivery vehicle for growth factors in bone regeneration and repair. PMID:25578692

Yao, Ai-Hua; Li, Xu-Dong; Xiong, Long; Zeng, Jian-Hua; Xu, Jun; Wang, De-Ping

2015-01-01

46

Effect of hydroxyapatite-containing microspheres embedded into three-dimensional magnesium phosphate scaffolds on the controlled release of lysozyme and in vitro biodegradation  

PubMed Central

The functionality of porous three-dimensional (3D) magnesium phosphate (MgP) scaffold was investigated for the development of a novel protein delivery system and biomimetic bone tissue engineering scaffold. This enhancement can be achieved by incorporation of hydroxyapatite (HA)-containing polymeric microspheres (MSs) into a bulk MgP matrix, and a paste-extruding deposition (PED) system. In this work, the amount of MS and HA was precisely controlled when manufacturing MS-embedded MgP (MS/MgP) composite scaffolds. The main influence was researched in terms of in vitro lysozyme-release, in vitro biodegradation, mechanical properties, and in vitro calcification. The controlled release of lysozyme was indicated, while showing graded release patterns according to HA content. The composite scaffolds degraded gradually with MS content and degradation time. Due to the effect of HA inclusion, the higher HA-containing MS/MgP scaffolds could, not only delay the biodegradation process but also, compensate for the possible loss of mechanical properties. In this regard, it is reasonable to confirm the inverse relationship between biodegradation and corresponding compressive properties. In order to encourage bioactivity and osteoconductivity, the MS/MgP composite scaffolds were subjected to simulated body fluid treatment. Calcium deposition was, in turn, improved with increasing MS and HA content over time. This quantitative result was also proved using morphological and elemental analysis. In summary, a significant transformation of a monolithic MgP scaffold was directed toward a multifunctional bone tissue engineering scaffold equipped with controlled protein delivery, biodegradability, and bioactivity. PMID:25214782

Lee, Jongman; Yun, Hui-suk

2014-01-01

47

Effect of hydroxyapatite-containing microspheres embedded into three-dimensional magnesium phosphate scaffolds on the controlled release of lysozyme and in vitro biodegradation.  

PubMed

The functionality of porous three-dimensional (3D) magnesium phosphate (MgP) scaffold was investigated for the development of a novel protein delivery system and biomimetic bone tissue engineering scaffold. This enhancement can be achieved by incorporation of hydroxyapatite (HA)-containing polymeric microspheres (MSs) into a bulk MgP matrix, and a paste-extruding deposition (PED) system. In this work, the amount of MS and HA was precisely controlled when manufacturing MS-embedded MgP (MS/MgP) composite scaffolds. The main influence was researched in terms of in vitro lysozyme-release, in vitro biodegradation, mechanical properties, and in vitro calcification. The controlled release of lysozyme was indicated, while showing graded release patterns according to HA content. The composite scaffolds degraded gradually with MS content and degradation time. Due to the effect of HA inclusion, the higher HA-containing MS/MgP scaffolds could, not only delay the biodegradation process but also, compensate for the possible loss of mechanical properties. In this regard, it is reasonable to confirm the inverse relationship between biodegradation and corresponding compressive properties. In order to encourage bioactivity and osteoconductivity, the MS/MgP composite scaffolds were subjected to simulated body fluid treatment. Calcium deposition was, in turn, improved with increasing MS and HA content over time. This quantitative result was also proved using morphological and elemental analysis. In summary, a significant transformation of a monolithic MgP scaffold was directed toward a multifunctional bone tissue engineering scaffold equipped with controlled protein delivery, biodegradability, and bioactivity. PMID:25214782

Lee, Jongman; Yun, Hui-Suk

2014-01-01

48

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

49

Part II: crystalline fluorapatite-coated hydroxyapatite implant material: a dog study with histologic comparison of osteogenesis seen with FA-coated HA grafting material versus HA controls: potential bacteriostatic effect of fluoridated HA.  

PubMed

Success of osteogenesis in bone graft procedures can be enhanced by inhibiting oral bacterial infections through the use of prophylactic bacteriostatic fluoride within the grafting environment. Ideally, the fluoride ion should be chemically sequestered and thus unavailable unless needed at times during the process of early infection. As fluoride within fluorapatite is tightly bound at neutral pH and becomes available only during acidic conditions, fluorapatite is an ideal store for the fluoride ion which becomes released for bacteriostasis only during an acidic environment found with incipient bacterial infection. The purpose of this investigation was to compare the histologic properties of new bone formed surrounding fluorapatite (FA)-coated microcrystalline hydroxyapatite (HA) grafting material with comparable bone formed following the use of control HA material (OsteoGen, Impladent, Ltd, Holliswood, NY). The results of histologic analysis within dog studies here showed no detectable difference in new bone following therapeutic grafting procedures using each of the above 2 mineral coatings. PMID:21028989

Nordquist, William D; Okudera, Hajima; Kitamura, Yutaka; Kimoto, Kazunari; Okudera, Toshimitsu; Krutchkoff, David J

2011-01-01

50

Microspheres  

NASA Technical Reports Server (NTRS)

Vital information on a person's physical condition can be obtained by identifying and counting the population of T-cells and B-cells, lymphocytes of the same shape and size that help the immune system protect the body from the invasion of disease. The late Dr. Alan Rembaum developed a method for identifying the cells. The method involved tagging the T-cells and B-cells with microspheres of different fluorescent color. Microspheres, which have fluorescent dye embedded in them, are chemically treated so that they can link with antibodies. With the help of a complex antibody/antigen reaction, the microspheres bind themselves to specific 'targets,' in this case the T-cells or B-cells. Each group of cells can then be analyzed by a photoelectronic instrument at different wavelengths emitted by the fluorescent dyes. Same concept was applied to the separation of cancer cells from normal cells. Microspheres were also used to conduct many other research projects. Under a patent license Magsphere, Inc. is producing a wide spectrum of microspheres on a large scale and selling them worldwide for various applications.

1990-01-01

51

A comparison of bone formation in biphasic calcium phosphate (BCP) and hydroxyapatite (HA) implanted in muscle and bone of dogs at different time periods.  

PubMed

Physicochemical modification could implement synthetic materials into osteoinductive materials, which induce bone formation in nonosseous tissues. We hereby studied the relevance between the osteogenic capacities of osteoinductive materials in nonosseous tissues and in osseous sites. Biphasic calcium phosphate ceramic (BCP) and hydroxyapatite ceramic (HA) were implanted in femoral muscles and femoral cortical bone of dogs for 7, 14, 21, 30, 45, 60, 90, 180, and 360 days, respectively. Two dogs were used in each time point. In each dog, four cylinders (phi5x6 mm) per material were implanted in femoral muscles and 2 cylinders (phi5x6 mm) per material in femoral cortical bone. The harvested samples were processed for both histological and histomorphometric analyses. Bone was observed in BCP implanted in femoral muscles since day 30, while in HA since day 45. Quantitatively, more bone was formed in BCP than in HA at each time point after day 30 (p<0.05). The earlier and more bone formed in BCP than in HA suggests BCP a higher osteoinductive potential than HA in muscle. In femoral cortical bone defects, a bridge of bone in the defect with BCP was observed at day 21, while with HA at day 30. At days 14, 21, and 30, significantly more bone was formed in BCP than in HA (p<0.05). The results herein show that osteogenic capacities of osteoinductive materials in nonosseous tissues and osseous sites are correlated: the higher the osteoinductive potential of the material, the faster the bone repair. PMID:16619253

Yuan, H; van Blitterswijk, C A; de Groot, K; de Bruijn, J D

2006-07-01

52

Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly l-lactide (PLLA). Part II: practical properties of miniscrews and miniplates  

Microsoft Academic Search

Miniscrews and miniplates made of forged composites composed of raw hydroxyapatite (u-HA) particles (particle size 0.2–20?m, averaging 3.0?m, Ca\\/p=1.69 and containing CO32?) and a poly l-lactide (PLLA, M?v: about 180kDa, containing residual 0.05wt% lactide) with osteological bioactivity such as direct bonding to bone and osteoconductivity, total resorbability and radiopacity were examined for various mechanical properties in order to evaluate their

Y. Shikinami; M. Okuno

2001-01-01

53

In vitro and in vivo evaluations of nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) as a novel bioactive bone screw.  

PubMed

In this study, we prepared nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) bioactive bone screws. The microstructure, morphology and coating of the screws were characterised, and the adhesion, proliferation and viability of MC3T3-E1 cells on n-HA/PA66/GF scaffolds were determined using scanning electron microscope, CCK-8 assays and cellular immunofluorescence analysis. The results confirmed that n-HA/PA66/GF scaffolds were biocompatible and had no negative effect on MC3T3-E1 cells in vitro. To investigate the in vivo biocompatibility, internal fixation properties and osteogenesis of the bioactive screws, both n-HA/PA66/GF screws and metallic screws were used to repair intercondylar femur fractures in dogs. General photography, CT examination, micro-CT examination, histological staining and biomechanical assays were performed at 4, 8, 12 and 24 weeks after operation. The n-HA/PA66/GF screws exhibited good biocompatibility, high mechanical strength and extensive osteogenesis in the host bone. Moreover, 24 weeks after implantation, the maximum push-out load of the bioactive screws was greater than that of the metallic screws. As shown by their good cytocompatibility, excellent biomechanical strength and fast formation and ingrowth of new bone, n-HA/PA66/GF screws are thus suitable for orthopaedic clinical applications. PMID:23861888

Su, Bao; Peng, Xiaohua; Jiang, Dianming; Wu, Jun; Qiao, Bo; Li, Weichao; Qi, Xiaotong

2013-01-01

54

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

55

Tricalcium phosphate/hydroxyapatite (TCP-HA) bone scaffold as potential candidate for the formation of tissue engineered bone  

PubMed Central

Background & objectives: Various materials have been used as scaffolds to suit different demands in tissue engineering. One of the most important criteria is that the scaffold must be biocompatible. This study was carried out to investigate the potential of HA or TCP/HA scaffold seeded with osteogenic induced sheep marrow cells (SMCs) for bone tissue engineering. Methods: HA-SMC and TCP/HA-SMC constructs were induced in the osteogenic medium for three weeks prior to implantation in nude mice. The HA-SMC and TCP/HA-SMC constructs were implanted subcutaneously on the dorsum of nude mice on each side of the midline. These constructs were harvested after 8 wk of implantation. Constructs before and after implantation were analyzed through histological staining, scanning electron microscope (SEM) and gene expression analysis. Results: The HA-SMC constructs demonstrated minimal bone formation. TCP/HA-SMC construct showed bone formation eight weeks after implantation. The bone formation started on the surface of the ceramic and proceeded to the centre of the pores. H&E and Alizarin Red staining demonstrated new bone tissue. Gene expression of collagen type 1 increased significantly for both constructs, but more superior for TCP/HA-SMC. SEM results showed the formation of thick collagen fibers encapsulating TCP/HA-SMC more than HA-SMC. Cells attached to both constructs surface proliferated and secreted collagen fibers. Interpretation & conclusions: The findings suggest that TCP/HA-SMC constructs with better osteogenic potential compared to HA-SMC constructs can be a potential candidate for the formation of tissue engineered bone. PMID:23852290

Sulaiman, Shamsul Bin; Keong, Tan Kok; Cheng, Chen Hui; Saim, Aminuddin Bin; Idrus, Ruszymah Bt. Hj

2013-01-01

56

Facile synthesis of hydroxyapatite nanoparticles, nanowires and hollow nano-structured microspheres using similar structured hard-precursors.  

PubMed

A facile strategy was developed to delicately control the morphologies of hydroxyapatite materials from simple 0D morphologies to complicated 3D architectures using hard-precursors with similar structures. The present study provides a new platform for hydroxyapatite materials to be efficiently synthesized and manipulated. PMID:21698324

Lin, Kaili; Liu, Xiaoguo; Chang, Jiang; Zhu, Yingjie

2011-08-01

57

Facile synthesis of hydroxyapatite nanoparticles, nanowires and hollow nano-structured microspheres using similar structured hard-precursors  

NASA Astrophysics Data System (ADS)

A facile strategy was developed to delicately control the morphologies of hydroxyapatite materials from simple 0D morphologies to complicated 3D architectures using hard-precursors with similar structures. The present study provides a new platform for hydroxyapatite materials to be efficiently synthesized and manipulated.A facile strategy was developed to delicately control the morphologies of hydroxyapatite materials from simple 0D morphologies to complicated 3D architectures using hard-precursors with similar structures. The present study provides a new platform for hydroxyapatite materials to be efficiently synthesized and manipulated. Electronic supplementary information (ESI) available: includes experimental section, XRD patterns of the precursors and chemical composition of the as-synthesized HAp powders. See DOI: 10.1039/c1nr10334b

Lin, Kaili; Liu, Xiaoguo; Chang, Jiang; Zhu, Yingjie

2011-08-01

58

Computer-aided design and manufacturing and rapid prototyped nanoscale hydroxyapatite/polyamide (n-HA/PA) construction for condylar defect caused by mandibular angle ostectomy.  

PubMed

The fracture or defect of the mandibular condyle is one of the serious complications during angle-reduction ostectomy. Reconstruction of such defects also is a daunting task. The case report describes a method based on computer-aided design/computer-aided manufacturing (CAD/CAM) and rapid prototyping nanoscale hydroxyapatite/polyamide (n-HA/PA) for individual design, fabrication, and implantation of a mandibular condyle. A 27-year-old woman with a square-shaped face who had previously undergone mandibular angle reduction reported with malocclusion, deviated mouth, collapse of the right side of the face, and masticatory problems. The reason for the problems was the unintended removal of the condyle during the ostectomy procedure. Using computed tomography (CT) data, a biomimetic n-HA/PA scaffold, and CAD/CAM for rapid prototyping by three-dimensional (3D) printing, a perfect-fitting condylar implant was fabricated. A surgical guide system also was developed to reproduce the procedures accurately so a perfect fit could be obtained during surgery. The patient ultimately regained reasonable jaw contour and appearance, as well as appreciable temporomandibular joint (TMJ) function. PMID:20972567

Li, Jihua; Hsu, Yuchun; Luo, En; Khadka, Ashish; Hu, Jing

2011-08-01

59

Hydroxyapatite hierarchically nanostructured porous hollow microspheres: rapid, sustainable microwave-hydrothermal synthesis by using creatine phosphate as an organic phosphorus source and application in drug delivery and protein adsorption.  

PubMed

Hierarchically nanostructured porous hollow microspheres of hydroxyapatite (HAP) are a promising biomaterial, owing to their excellent biocompatibility and porous hollow structure. Traditionally, synthetic hydroxyapatite is prepared by using an inorganic phosphorus source. Herein, we report a new strategy for the rapid, sustainable synthesis of HAP hierarchically nanostructured porous hollow microspheres by using creatine phosphate disodium salt as an organic phosphorus source in aqueous solution through a microwave-assisted hydrothermal method. The as-obtained products are characterized by powder X-ray diffraction (XRD), Fourier-transform IR (FTIR) spectroscopy, SEM, TEM, Brunauer-Emmett-Teller (BET) nitrogen sorptometry, dynamic light scattering (DLS), and thermogravimetric analysis (TGA). SEM and TEM micrographs show that HAP hierarchically nanostructured porous hollow microspheres consist of HAP nanosheets or nanorods as the building blocks and DLS measurements show that the diameters of HAP hollow microspheres are within the range 0.8-1.5??m. The specific surface area and average pore size of the HAP porous hollow microspheres are 87.3?m(2) g(-1) and 20.6?nm, respectively. The important role of creatine phosphate disodium salt and the influence of the experimental conditions on the products were systematically investigated. This method is facile, rapid, surfactant-free and environmentally friendly. The as-prepared HAP porous hollow microspheres show a relatively high drug-loading capacity and protein-adsorption ability, as well as sustained drug and protein release, by using ibuprofen as a model drug and hemoglobin (Hb) as a model protein, respectively. These experiments indicate that the as-prepared HAP porous hollow microspheres are promising for applications in biomedical fields, such as drug delivery and protein adsorption. PMID:23460360

Qi, Chao; Zhu, Ying-Jie; Lu, Bing-Qiang; Zhao, Xin-Yu; Zhao, Jing; Chen, Feng; Wu, Jin

2013-04-22

60

Fabrication, characterization and evaluation of bioceramic hollow microspheres used as microcarriers for 3-D bone tissue formation in rotating bioreactors  

Microsoft Academic Search

Novel bioactive ceramic hollow microspheres with an apparent density in the range 0.8–1.0gcm-3 have been developed as microcarriers for 3-D bone tissue formation in rotating-wall vessels (RWV). Hollow ceramic microspheres with a composition of 58–72%SiO2, 28–42%Al2O3 (wt%) and an apparent density 0.8–1.0gcm-3 were pretreated in 1.0n NaOH for 2h before being coated with synthesized calcium hydroxyapatite (HA) particulate sol. The

Qing-Qing Qiu; Paul Ducheyne; Portonovo S. Ayyaswamy

1999-01-01

61

Polymeric microspheres  

DOEpatents

The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

2004-04-13

62

Fabrication, characterization and evaluation of bioceramic hollow microspheres used as microcarriers for 3-D bone tissue formation in rotating bioreactors.  

PubMed

Novel bioactive ceramic hollow microspheres with an apparent density in the range 0.8-1.0 g cm(-3) have been developed as microcarriers for 3-D bone tissue formation in rotating-wall vessels (RWV). Hollow ceramic microspheres with a composition of 58-72% SiO2, 28-42% Al2O3 (wt%) and an apparent density 0.8-1.0 g cm(-3) were pretreated in 1.0 N NaOH for 2 h before being coated with synthesized calcium hydroxyapatite (HA) particulate sol. The HA-coated hollow microspheres were sintered for 1 h at 600, 800 and 1000 degrees C. SEM analysis revealed that the grain size and pore size of the calcium phosphate coating increased with the sintering temperature. FTIR analysis showed that crystalline calcium hydroxyapatite was present in the coatings sintered at 600 and 800 degrees C. When sintered at 1000 degrees C, the coating consisted of alpha-tricalcium phosphate. All the coatings adhered well, independent of sintering temperature. The trajectory analysis revealed that the hollow microsphere remained suspended in a rotating-wall vessel (RWV), and experienced a low shear stress (approximately 0.6 dyn cm(-2)). Cell culture studies using rat bone marrow stromal cells and osteosarcoma cells (ROS 17/2.8) showed that the cells attached to and formed 3-D aggregates with the hollow microspheres in a RWV. Extracellular matrix was observed in the aggregates. These data suggest that these hollow bioactive ceramic microspheres can be used as microcarriers for 3-D bone tissue formation in vitro, as well as for the study of the effects of microgravity on bone cell functions. PMID:10378799

Qiu, Q Q; Ducheyne, P; Ayyaswamy, P S

1999-06-01

63

Biomaterials 27 (2006) 58455854 A citric acid-based hydroxyapatite composite for orthopedic implants  

E-print Network

Biomaterials 27 (2006) 5845­5854 A citric acid-based hydroxyapatite composite for orthopedic with hydroxyapatite (HA), a bioceramic that can be found in natural bone. Although HA is very brittle and hard

Yang, Jian

64

Nanoscale adhesion forces between enamel pellicle proteins and hydroxyapatite.  

PubMed

The acquired enamel pellicle (AEP) is important for minimizing the abrasion caused by parafunctional conditions as they occur, for instance, during bruxism. It is a remarkable feature of the AEP that a protein/peptide film can provide enough protection in normofunction to prevent teeth from abrasion and wear. Despite its obvious critical role in the protection of tooth surfaces, the essential adhesion features of AEP proteins on the enamel surface are poorly characterized. The objective of this study was to measure the adhesion force between histatin 5, a primary AEP component, and hydroxyapatite (HA) surfaces. Both biotinylated histatin 5 and biotinylated human serum albumin were allowed to adsorb to streptavidin-coated silica microspheres attached to atomic force microscope (AFM) cantilevers. A multimode AFM with a Nanoscope IIIa controller was used to measure the adhesion force between protein-functionalized silica microspheres attached to cantilever tips and the HA surface. The imaging was performed in tapping mode with a Si3N4 AFM cantilever, while the adhesion forces were measured in AFM contact mode. A collection of force-distance curves (~3,000/replicate) was obtained to generate histograms from which the adhesion forces between histatin 5 or albumin and the HA surface were measured. We found that histatin 5 exhibited stronger adhesion forces (90% >1.830 nN) to the HA surface than did albumin (90% > 0.282 nN). This study presents an objective approach to adhesion force measurements between histatin 5 and HA, and provides the experimental basis for measuring the same parameters for other AEP constituents. Such knowledge will help in the design of synthetic proteins and peptides with preventive and therapeutic benefits for tooth enamel. PMID:24591293

Vukosavljevic, D; Hutter, J L; Helmerhorst, E J; Xiao, Y; Custodio, W; Zaidan, F C; Oppenheim, F G; Siqueira, W L

2014-05-01

65

Hydroxyapatite reinforced collagen scaffolds with improved architecture and mechanical properties.  

PubMed

Hydroxyapatite (HA) reinforced collagen scaffolds have shown promise for synthetic bone graft substitutes and tissue engineering scaffolds. Freeze-dried HA-collagen scaffolds are readily fabricated and have exhibited osteogenicity in vivo, but are limited by an inherent scaffold architecture that results in a relatively small pore size and weak mechanical properties. In order to overcome these limitations, HA-collagen scaffolds were prepared by compression molding HA reinforcements and paraffin microspheres within a suspension of concentrated collagen fibrils (?180mg/mL), cross-linking the collagen matrix, and leaching the paraffin porogen. HA-collagen scaffolds exhibited an architecture with high porosity (85-90%), interconnected pores ?300-400?m in size, and struts ?3-100?m in thickness containing 0-80vol% HA whisker or powder reinforcements. HA reinforcement enabled a compressive modulus of up to ?1MPa, which was an order of magnitude greater than unreinforced collagen scaffolds. The compressive modulus was also at least one order of magnitude greater than comparable freeze-dried HA-collagen scaffolds and two orders of magnitude greater than absorbable collagen sponges used clinically. Moreover, scaffolds reinforced with up to 60vol% HA exhibited fully recoverable elastic deformation upon loading to 50% compressive strain for at least 100,000 cycles. Thus, the scaffold mechanical properties were well-suited for surgical handling, fixation, and bearing osteogenic loads during bone regeneration. The scaffold architecture, permeability, and composition were shown to be conducive to the infiltration and differentiation of adipose-derive stromal cells in vitro. Acellular scaffolds were demonstrated to induce angiogenesis and osteogenesis after subcutaneous ectopic implantation by recruiting endogenous cell populations, suggesting that the scaffolds were osteoinductive. PMID:25644451

Kane, Robert J; Weiss-Bilka, Holly E; Meagher, Matthew J; Liu, Yongxing; Gargac, Joshua A; Niebur, Glen L; Wagner, Diane R; Roeder, Ryan K

2015-04-15

66

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

67

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

68

Synthesis and characterization of hydroxyapatite, fluoride-substituted hydroxyapatite and fluorapatite  

Microsoft Academic Search

Powders of hydroxyapatite (HA), partially fluoride-substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in house using optimum methods to achieve relatively pure powders. These powders were assessed by the commonly used bulk techniques of X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and FT-Raman spectroscopies, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and F-selective electrode. In addition, the current study has

M. Wei; J. H. Evans; T. Bostrom; L. Grøndahl

2003-01-01

69

Cementless hydroxyapatite coated hip prostheses.  

PubMed

More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality. PMID:25802848

Herrera, Antonio; Mateo, Jesús; Gil-Albarova, Jorge; Lobo-Escolar, Antonio; Ibarz, Elena; Gabarre, Sergio; Más, Yolanda; Gracia, Luis

2015-01-01

70

Cementless Hydroxyapatite Coated Hip Prostheses  

PubMed Central

More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality. PMID:25802848

Herrera, Antonio; Mateo, Jesús; Gil-Albarova, Jorge; Lobo-Escolar, Antonio; Ibarz, Elena; Gabarre, Sergio; Más, Yolanda

2015-01-01

71

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

72

Microspherical catalysts  

SciTech Connect

A catalyst which is a hollow microsphere comprising an outer shell in which there are feeder pores and an active ingredient arranged within the shell. The microsphere has a diameter ranging from 20 to 120 microns and the shell has a thickness ranging from 0.1 to 20.0 microns. The active ingredient fills 1.0% to 100% of the void space within the microsphere.

Hettinger, W. P.; Beck, H. W.

1985-10-22

73

Mechanical properties of hydroxyapatite/mica composite.  

PubMed

Bend specimens of the inorganic synthetic materials hydroxyapatite (HA) and a composite of hydroxyapatite/muscovite mica have been prepared and tested mechanically. Sintering followed by hot isostatic pressing (HIP) without encapsulation gave an increased strength for HA alone, but no significant increase in strength compared with sintering alone for HA/mica composites. The bend strength of the HA/mica composite was inferior to that of HA alone, the reason being inadequate bonding between HA and mica. HIP in glass capsules and an increased cold compaction pressure tended to improve the bend strength of the composite. Corrosion in tris for 7 d did not affect the bend strength of the investigated materials significantly. PMID:7950878

Nordström, E G; Herø, H; Jørgensen, R B

1994-01-01

74

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. The main inorganic phase of human bone is calcium hydroxyapatite (Ca10(PO4)6- (OH)2, HA). To achieve better been used for sample characterization. I. Background CHEMICALLY precipitated calcium hydroxyapatite (Ca

Tas, A. Cuneyt

75

HA Obtained by SGP and WCP  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) has been used as dental implant material and as bone replacement (in bone reconstruction). Ca/P molar ratio varies with the chemical process used, parameter could determine the clinic application. In the present work, HA was synthesized using the wet chemical process (WCP) and the sol-gel process (SGP). The efficiency of both chemical procedures was greater than 90%. HA by SGP was more crystalline and porous than WCP, also its cluster are further homogenous. The ICP-OES technique revealed that the HA by SGP was stoichiometric (Ca/P = 1.67). In meantime, the WCP had the molar ratio Ca/P = 1.56.

Guzmán Vázquez, Carolina; Piña Barba, Cristina

2006-09-01

76

Measurement of Crystallinity and Phase Composition of Hydroxyapatite by XRD  

E-print Network

1 . Measurement of Crystallinity and Phase Composition of Hydroxyapatite by XRD VAMAS TWA#3 Project. #12;2 . The XRD pattern for HA has many peaks in the range from about 7° to about 60° 2 CuK. The most or poorly crystallized HA as illustrated in Figure 2. Figure 1. XRD patterns obtained from phase pure HA

77

Hydroxyapatite-nanotube composites and coatings for orthopedic applications  

Microsoft Academic Search

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

Debrupa Lahiri

2011-01-01

78

Polyacrolein microspheres  

NASA Technical Reports Server (NTRS)

Microspheres of acrolein homopolymers and copolymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Rembaum, Alan (Inventor)

1987-01-01

79

Polyacrolein microspheres  

NASA Technical Reports Server (NTRS)

Microspheres of acrolein homopolymers and co-polymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Rembaum, Alan (Inventor)

1983-01-01

80

Polyacrolein microspheres  

NASA Technical Reports Server (NTRS)

Microspheres of acrolein homopolymers and copolymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Rembaum, Alan (Inventor)

1986-01-01

81

Hydroxyapatite Coating Of Threaded Pins Enhances Fixation  

Microsoft Academic Search

We measured the insertion and extraction torque forces in a randomised study of 76 external fixation screws in 19 patients treated by hemicallotasis for osteoarthritis of the medial side of the knee. The patients were randomised to have either standard tapered screws (Orthofix 6\\/5 mm) or the same screws with hydroxyapatite (HA) coating. One patient had two standard and two

G. Magyar; S. Toksvig-Larsen; A. Moroni

1997-01-01

82

Hydroxyapatite: Mechanism of formation and properties  

Microsoft Academic Search

Hydroxyapatite (HA) was prepared by stirring amorphous calcium phosphate (ACP), which contained occluded Cl? as a tracer ion, in distilled water buffered to pH 7.4 by tris-HCl at 25, 37, 60, 80 and 100°. HA made in this manner contained from less than 1% (25°) to 11% (100°) of the amount originally occluded in the precursor ACP. These results suggest

Norman C. Blumenthal; Aaron S. Posner

1973-01-01

83

Surface characterization of colloidal-sol gel derived biphasic HA\\/FA coatings  

Microsoft Academic Search

Hydroxyapatite (HA) powders are ultrasonically dispersed in the precursor of fluoridated hydroxyapatite (FHA) or fluorapatite\\u000a (FA) to form a “colloidal sol”. HA\\/FA biphasic coatings are prepared on Ti6Al4V substrate via dip coating, 150 ?C drying and\\u000a 600 ?C firing. The coatings show homogenous distribution of HA particles in the FA matrix. The relative phase proportion can\\u000a be tailored by the amount of

Kui Cheng; Sam Zhang; Wenjian Weng

2007-01-01

84

Osteogenesis and Trophic Factor Secretion are Influenced by the Composition of Hydroxyapatite/Poly(Lactide-Co-Glycolide) Composite Scaffolds  

PubMed Central

The use of composite biomaterials for bone repair capitalizes on the beneficial aspects of individual materials while tailoring the mechanical properties of the composite. We hypothesized that substrate composition would modulate the osteogenic response and secretion of potent trophic factors by human mesenchymal stem cells (hMSCs). Composite scaffolds were prepared by combining nanosized hydroxyapatite (HA) and microspheres formed of poly(lactic-co-glycolic acid) (PLG) at varying ratios between 0:1 and 5:1. Scaffolds were seeded with hMSCs for culture in osteogenic conditions or subcutaneous implantation into nude rats. Compressive moduli increased with HA content in a near-linear fashion. The osteogenic differentiation of hMSCs increased in a dose-dependent manner as determined by alkaline phosphatase activity and osteopontin secretion after 4 weeks of culture. Further, endogenous secretion of vascular endothelial growth factor was sustained at significantly higher levels over 28 days for hMSCs seeded in 2.5:1 and 5:1 HA:PLG scaffolds. Eight weeks after implantation, scaffolds with higher HA:PLG ratios exhibited greater vascularization and more mineralized tissue. These data demonstrate that the mechanical properties, osteogenic differentiation, as well as the timing and duration of trophic factor secretion by hMSCs can be tailored through controlling the composition of the polymer–bioceramic composite. PMID:19642853

He, Jiawei; Genetos, Damian C.

2010-01-01

85

Fluorescent microspheres  

NASA Technical Reports Server (NTRS)

Latex particles with attached antibodies have potential biochemical and environmental applications. Human red blood cells and lymphocytes have been labeled with fluorescent microspheres by either direct or indirect immunological technique. Immunolatex spheres can also be used for detecting and localizing specific cell surface receptors. Hormones and toxins may also be bondable.

Rembaum, A.

1978-01-01

86

Cytotoxicity of hydroxyapatite, fluorapatite and fluor-hydroxyapatite: a comparative in vitro study.  

PubMed

The purpose of this study was to evaluate the cytotoxicity of two formulations of hydroxyapatite (HA), namely fluorapatite (FA) and fluor-hydroxyapatite (FHA). HA is used as carrier material for antibiotics or anticancer drugs during treatment of bone metastasis. Negative control, represented by HA, was included for comparative purposes. Leukemia cells were used as a model cell line, and the effect of eluates of tested biomaterials on cell proliferation/viability and mechanism of antiproliferative activity were assessed. Study design attempted to reveal the toxicity of tested biomaterials with an emphasis to decide if tested biomaterials have promise for further studies in vivo. Results showed that eluates of FA and FHA inhibit the growth of leukemia cells and induce programmed cell death through mitochondrial/caspase-9/caspase-3-dependent pathway. Due to these differences compare to HA, it is concluded that FA and FHA have promise for evaluation of their behaviour in vivo. PMID:18505342

Theiszova, M; Jantova, S; Letasiova, S; Palou, M; Cipak, L

2008-01-01

87

Synthesis and characterization of hydroxyapatite-ciprofloxacin delivery systems by precipitation and spray drying technique.  

PubMed

This investigation synthesized and characterized hydroxyapatite (HAP) microspheres, agglomerated microspheres, and implants containing ciprofloxacin. This delivery system is to be used as an implantable drug delivery system for the treatment of bone infections. The HAP microspheres were made by chemical precipitation followed by a spray-drying technique. Agglomerated microspheres were prepared by a wet granulation process using a granulator. Implants were prepared by direct compression of the granules on a Carver press. Ciprofloxacin was analyzed by high-performance liquid chromatography. Characterization of the HAP microspheres include particle size, size distribution, physical state of the drug in the microsphere, and microstructure of the drug delivery system before and after in vitro release. The particle size, porosity, and morphology of the microspheres were dependent on viscosity and concentration of the slurry as well as the atomization pressure used during spray drying. Even at the highest drug load (2% wt/wt), the drug was present in a noncrystalline state. The drug release from the agglomerated microspheres was quick and almost complete within 1 hour. However, compressing the same amount of agglomerated microspheres into an implant greatly reduced the rate of ciprofloxacin release. Only 12% (wt/wt) of the drug was released from the implant within 1 hour. The in vitro release of ciprofloxacin from these implants follows a diffusion-controlled mechanism. This method provides a unique way of producing various shapes and drug loads of HAP microspheres that can be easily manufactured on a commercial scale. PMID:12916954

Pham, Hai H; Luo, Ping; Génin, François; Dash, Alekha K

2002-01-01

88

Fabrication and Characterization of Titanium-doped Hydroxyapatite Thin Films  

E-print Network

in composition and degree of crystallinity. Bone mineral is typically calcium deficient and contains carbonate substitutions. Other ions present in bone mineral include magnesium (Mg2+), sodium (Na+), potassium (K+), fluoride (F-), and chloride (Cl-) ions... .2 Hydroxyapatite 5 2.2.1 Use of HA as an Implant Coating 6 2.2.2 Substituted Hydroxyapatite 7 2.2.2.1 Carbonate 7 2.2.2.2 Magnesium...

Desai, Amit Y

89

Composite biocompatible hydroxyapatite–silk fibroin coatings for medical implants obtained by Matrix Assisted Pulsed Laser Evaporation  

Microsoft Academic Search

The aim of this study was to obtain biomimetic inorganic–organic thin films as coatings for metallic medical implants. These contain hydroxyapatite, the inorganic component of the bony tissues, and a natural biopolymer – silk fibroin – added in view to induce the surface functionalization. Hydroxyapatite (HA), silk fibroin (FIB) and composite HA–FIB films were obtained by Matrix Assisted Pulsed Laser

F. M. Miroiu; G. Socol; A. Visan; N. Stefan; D. Craciun; V. Craciun; G. Dorcioman; I. N. Mihailescu; L. E. Sima; S. M. Petrescu; A. Andronie; I. Stamatin; S. Moga; C. Ducu

2010-01-01

90

Development of biomimetic nano-hydroxyapatite\\/poly(hexamethylene adipamide) composites  

Microsoft Academic Search

In this study, acicular nano-hydroxyapatite (n-HA) was used to make a new biomimetic composite with polyamide (poly hexamethylene adipamide) by a unique technique. The physical and chemical characteristics of the composites were tested. It was found that these synthesized n-HA crystals were similar to bone apatite in size, phase composition and crystal structure. The biomimetic n-HA crystals were uniformly distributed

Xuejiang Wang; Yubao Li; Jie Wei; Klass de Groot

2002-01-01

91

The Activity of Glucosyltransferase Adsorbed onto Saliva-coated Hydroxyapatite  

Microsoft Academic Search

This study aimed to determine physical and kinetic properties of glucosyltransferase (GTF) adsorbed onto hydroxyapatite (HA) surfaces. For development of a solid-phase enzyme assay, 4.0-mg samples of washed HA powder were exposed to centrifuged whole saliva (WSHA) or buffer, and subsequently exposed to a GTF solution. The activities of GTF adsorbed to HA and that remaining in solution were measured.

K. M. Schilling; W. H. Bowen

1988-01-01

92

Hydroxyapatite-Nanotube Composites and Coatings for Orthopedic Applications  

Microsoft Academic Search

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.\\u000aThe aim of the

Debrupa Lahiri

2011-01-01

93

Synthesis of Calcium HydroxyapatiteTricalcium Phosphate (HATCP) Composite Bioceramic Powders and Their Sintering Behavior  

E-print Network

Synthesis of Calcium Hydroxyapatite­Tricalcium Phosphate (HA­TCP) Composite Bioceramic Powders important inorganic phases of synthetic bone applications--namely, calcium hydroxyapatite (Ca10(PO4)6(OH)2 (HA)) and tri- calcium phosphate (Ca3(PO4)2 (TCP))--were prepared as submicrometer-sized, chemically

Tas, A. Cuneyt

94

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

95

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

96

Biomimetic synthesis of carbonated hydroxyapatite thin films  

Microsoft Academic Search

Free-standing continuous carbonated hydroxyapatite (HA) films were synthesized at room temperature through a biomimetic pathway. A stearic acid monolayer was utilized as a template for inducing deposition from supersaturated calcium phosphate solutions. Crystalline films could be collected at the water–air interface after just 8 h at room temperature when the Ca\\/P molar ratio of the supersaturated solution is 1:1, whereas

E. Boanini; A. Bigi

2006-01-01

97

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

98

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

99

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

100

Pitch carbon microsphere composite  

NASA Technical Reports Server (NTRS)

Petroleum pitch carbon microspheres were prepared by flash heating emulsified pitch and carbonizing the resulting microspheres in an inert atmosphere. Microsphere composites were obtained from a mixture of microspheres and tetraester precursor pyrrone powder. Scanning electron micrographs of the composite showed that it was an aggregate of microspheres bonded together by the pyrrone at the sphere contact points, with voids in and among the microspheres. Physical, thermal, and sorption properties of the composite are described. Composite applications could include use as a honeycomb filler in elevated-temperature load-bearing sandwich boards or in patient-treatment tables for radiation treatment of tumors.

Price, H. L.; Nelson, J. B.

1977-01-01

101

Boron nitride nanotube reinforced hydroxyapatite composite: Mechanical and tribological performance and in-vitro biocompatibility to osteoblasts  

Microsoft Academic Search

This study proposes boron nitride nanotube (BNNT) reinforced hydroxyapatite (HA) as a novel composite material for orthopedic implant applications. The spark plasma sintered (SPS) composite structure shows higher density compared to HA. Minimal lattice mismatch between HA and BNNT leads to coherent bonding and strong interface. HA-4 wt% BNNT composite offers excellent mechanical properties—120% increment in elastic modulus, 129% higher

Debrupa Lahiri; Virendra Singh; Ana Paula Benaduce; Sudipta Seal; Lidia Kos; Arvind Agarwal

2011-01-01

102

Poly(vinyl alcohol-co-lactic acid)\\/Hydroxyapatite Composites: Synthesis and Characterization  

Microsoft Academic Search

There is a wide range of applications where calcium phosphate and hydroxyapatite (HA) are used as biomaterials, e.g. as synthetic\\u000a bone grafts, coating on metal prostheses (like hip endoprostheses or dental implants) and drug carriers. In the study, the\\u000a design and synthesis of composites based on poly(vinyl alcohol-co-lactic acid)\\/hydroxyapatite (PVA-co-LA\\/HA) with potential\\u000a for biomedical applications, they are presented. The hydroxyapatite

Nita TudorachiAurica; Aurica P. Chiriac

2011-01-01

103

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

104

Hydrothermal synthesis of hydroxyapatite  

Microsoft Academic Search

A hydrothermal method of synthesizing hydroxyapatite by heating a precipitate, formed by mixing Ca(NO3)2?4H2O and (NH4)2HPO4 with distilled water, in a hydrothermal reactor at 200 C for 24-72 hrs is described. A treatment time of 24 hrs produced single phase (as shown by XRD) hydroxyapatite powder, however for longer treatment times XRD patterns were indicative of the presence of a

J S Earl; D J Wood; S J Milne

2006-01-01

105

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

106

Investigation of a HA/PDLGA/Carbon Foam Material System for Orthopedic Fixation Plates Based on Time-Dependent Properties  

E-print Network

of the same material as healing progresses. The present research focuses on the development and characterization of a material system consisting of carbon foam infiltrated with hydroxyapatite (HA) reinforced poly(D,L-lactide)-co-poly(glycolide) (PDLGA). A...

Rodriguez, Douglas E.

2010-01-14

107

Surface characterization of colloidal-sol gel derived biphasic HA/FA coatings.  

PubMed

Hydroxyapatite (HA) powders are ultrasonically dispersed in the precursor of fluoridated hydroxyapatite (FHA) or fluorapatite (FA) to form a "colloidal sol". HA/FA biphasic coatings are prepared on Ti6Al4V substrate via dip coating, 150 degrees C drying and 600 degrees C firing. The coatings show homogenous distribution of HA particles in the FA matrix. The relative phase proportion can be tailored by the amount of HA in the colloidal sol. The surfaces of the coatings consist of two kinds of distinct domains: HA and FA, resulting in a compositionally heterogeneous surface. The biphasic coating surface becomes increasingly rougher with HA powders, from around 200 nm of pure FA to 400-600 nm in Ra of biphasic coatings. The rougher biphasic HA/FA surfaces with chemically controllable domains will favor cell attachment, apatite layer deposition and necessary dissolution in clinical applications. PMID:17558480

Cheng, Kui; Zhang, Sam; Weng, Wenjian

2007-10-01

108

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...

109

Growth of one-dimensional single-crystalline hydroxyapatite nanorods  

NASA Astrophysics Data System (ADS)

A facile, effective and template/surfactant-free hydrothermal route in the presence of sodium bicarbonate was developed to synthesize highly uniform single-crystalline hydroxyapatite (HA) nanorods with the lengths of several hundred nanometers and aspect ratio up to ˜20. One dimensional (1-D) growth and aspect ratio could be controlled by hydrothermal reaction time and temperature. The longitudinal axis, also the growth direction of the nanorods, is parallel to the [001] direction of HA hexagonal crystal structure.

Ren, Fuzeng; Ding, Yonghui; Ge, Xiang; Lu, Xiong; Wang, Kefeng; Leng, Yang

2012-06-01

110

Porous spherical hydroxyapatite and fluorhydroxyapatite granules: processing and characterization  

Microsoft Academic Search

This study is aimed at the development of a method to fabricate porous spherical hydroxyapatite (HA)—fluorapatite (FA) granules. The method to produce porous granules is based on liquid immiscibility effect. A suspension of HA–FA powder mixtures in aqueous solution of gelatin and oil as a dispersion media were used. By stirring the mixtures of these immiscible liquids, granules of 50–200

V. S. Komlev; S. M. Barinov; E. Girardin; S. Oscarsson; Å. Rosengren; F. Rustichelli; V. P. Orlovskii

2003-01-01

111

Magnetically responsive elastic microspheres  

NASA Astrophysics Data System (ADS)

We report the design, fabrication, and characterization of magnetically responsive elastic microspheres consisting of polydimethylsioxane (PDMS) and magnetic nano-/microparticles. The microspheres can have either core-shell or solid structure, fabricated by using a microfluidic technique. The mechanical characteristics are determined with a modified electronic balance, and the results show that the microspheres exhibit magnetostrictive effect. Such microspheres can in addition behave as a smart material controllable through an external magnetic field. Owing to the transparency, biocompatibility and nontoxicity of PDMS, the magnetically responsive elastic microspheres may have potential applications in drug delivery, biosensing, bioseparation, and medical diagnosis.

Peng, Suili; Zhang, Mengying; Niu, Xize; Wen, Weijia; Sheng, Ping; Liu, Zhengyou; Shi, Jing

2008-01-01

112

Nanostructured nickel-free austenitic stainless steel/hydroxyapatite composites.  

PubMed

In this work Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite are presented and characterized by means of X-ray diffraction and optical profiling. The samples were synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). In our work we wanted to introduce into stainless steel hydroxyapatite ceramics that have been intensively studied for bone repair and replacement applications. Such applications were chosen because of their high biocompatibility and ability to bond to bone. Since nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels, it is possible that composite made of this steel and HA could improve properties, as well. Mechanical alloying and nitriding are very effective technologies to improve the corrosion resistance of stainless steel. Similar process in case of nanocomposites of stainless steel with hydroxyapatite helps achieve even better mechanical properties and corrosion resistance. Hence nanocrystalline nickel-free stainless steels and nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants, e.g., orthopedic implants. In such application, the surface roughness and more specifically the surface topography influences the proliferation of cells (e.g., osteoblasts). PMID:23421285

Tulinski, Maciej; Jurczyk, Mieczyslaw

2012-11-01

113

Hydroxyapatite with environmental applications  

SciTech Connect

The aim of this study was to synthetize new nanoparticles based on methyltrimethoxysilane coated hydroxyapatite (MTHAp) for lead removal in aqueous solutions. The morphological and compositional analysis of MTHAp was investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). Removal experiments of Pb{sup 2+} ions were carried out in aqueous solutions with controlled concentration of Pb{sup 2+} and at fixed pH of 5. After the removal experiment of Pb{sup 2+} ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp-5 via the adsorption of Pb{sup 2+} ions followed by a cation exchange reaction. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb{sup 2+} ions from aqueous solution.

Popa, C. L. [National Institute of Materials Physics, P.O. Box MG 07, Bucharest, Magurele, Romania and Faculty of Physics, University of Bucharest, 405 Atomistilor, CP MG-1, 077125 Magurele (Romania); Ciobanu, C. S.; Predoi, D., E-mail: dpredoi@gmail.com [National Institute of Materials Physics, P.O. Box MG 07, Bucharest, Magurele (Romania); Petre, C. C.; Jiga, G. [University Politehnica of Bucharest, Faculty of Engineering and Management of Technological Systems, Department of Strength of Materials, 060032, Bucharest (Romania); Motelica-Heino, M. [ISTO, UMR 7327 CNRS-Université d'Orléans, 1A rue de la Férollerie 45071 Orléans Cedex 2 (France); Iconaru, S. L. [National Institute of Materials Physics, P.O. Box MG 07, Bucharest, Magurele (Romania); Faculty of Physics, University of Bucharest, 405 Atomistilor, CP MG-1, 077125 Magurele (Romania); ISTO, UMR 7327 CNRS-Université d'Orléans, 1A rue (France)

2014-05-15

114

PREPARATION AND CHARACTERIZATION OF BIODEGRADABLE POLY(p?DIOXANONE)\\/HYDROXYAPATITE COMPOSITES  

Microsoft Academic Search

Poly(p?dioxanone) (PPDO)\\/hydroxyapatite (HA) composites with high viscosity?average molecular weights (say, 343,000 g\\/mol) were prepared through the in situ ring?opening polymerization of p?dioxanone (PDO) with HA nanopaticles (n?HA) and organically modified HA (EG?HA) in the presence of triethylaluminum as the catalyst. The structures of n?HA and EG?HA synthesized were characterized by Fourier transform infrared spectroscopy and powder X?ray diffractometer. Scanning electron microscopy

Chuan Wang

2009-01-01

115

Hydroxyapatite synthesis using EDTA  

PubMed Central

Bone comprises structure of body and is consisted of inorganic substances. It exists in an organic structure in the body. Even though it is firm and has self healing mechanism, it can be damaged by trauma, cancer, or bone diseases. Allograft can be an alternative solution for autologous bone graft. Hydroxyapatite(Ca10(PO4)6(OH)2), an excellent candidate for allograft, can be applied to bone defect area. There are several methods to produce hydroxyapatite, however economical cost and time consuming make the production difficult. In this study we synthesized the hydroxyapatite with Ethyenediamine tetraacetic acid. Freeze Dried Bone Allograft(Hans Biomed) was used to be a control group. Synthesized hydroxyapatite was a rod shape, white powdery type substance with 2 ~ 5 ?m length and 0.5 ~ 1 ?m width. X-ray diffraction showed the highest sharp peak at 32° and high peaks at 25.8°, 39.8°, 46.8°, 49.5°, and 64.0° indicating a similar substance to the freeze Dried Bone Allograft. 3 days after the cell growth of synthesized hydroxyapatite showed 1.5 fold more than the Bone Allograft. Cellular and media alkaline phosphate activity increased similar to the bone alloagraft. In this study we came up with a new method to produce the hydroxyapatite. It is a convenient method that can be held in room temperature and low pressure. Also the the product can be manufactured in large quantity. It can be also transformed into scaffold structure which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products. PMID:23714942

Kang, Nak Heon; Kim, Soon Je; Song, Seung Han; Choi, Sang mun; Choi, Sik Young; Kim, Youn Jung

2013-01-01

116

Synthesis and characterization of hydroxyapatite, fluoride-substituted hydroxyapatite and fluorapatite.  

PubMed

Powders of hydroxyapatite (HA), partially fluoride-substituted hydroxyapatite (fHA), and fluorapatite (FA) were synthesized in house using optimum methods to achieve relatively pure powders. These powders were assessed by the commonly used bulk techniques of X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and FT-Raman spectroscopies, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and F-selective electrode. In addition, the current study has employed transmission electron microscopy (TEM), involving morphological observation, electron diffraction and energy-dispersive X-ray spectrometry (EDX), as an effective analytical technique to evaluate the powders at a microscopic level. The HA and fHA particles were elongated platelets about 20 x 60 nm in size, while FA particles were over twice this size. Calcination of the HA and fHA powders at 1000 degrees C for 1 h resulted in increased grain size and crystallinity. The calcined fHA material appeared to possess a crystal structure intermediate between HA and FA, as evidenced by the (3 0 0) peak shift in XRD, as well as by the position of the hydroxyl bands in the FTIR spectra. This result was consistent with electron diffraction of individual particles. Small levels of impurities in some of the powders were identified by EDX and electron diffraction, and the carbonate content was detected by FTIR. The use of TEM in conjunction with the bulk techniques has allowed a more thorough assessment of the apatites, and has enabled the constituents in these closely related apatite powders to be identified. PMID:15348455

Wei, M; Evans, J H; Bostrom, T; Grøndahl, L

2003-04-01

117

Processing and mechanical properties of HA/UHMWPE nanocomposites.  

PubMed

A hydroxyapatite (HA) particulate reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite was fabricated by compounding HA and UHMWPE mixtures in paraffin oil using twin-screw extrusion and then compression molding. Scanning electron microscope images revealed that HA aggregates were broken down to nano-sized particles and homogeneously dispersed in UHMWPE by the combined processes of twin-screw extrusion and UHMWPE swelling treatment. Transmission electron microscope images indicated the HA particles and UHMWPE matrix were intimately contacted through mechanical interlocking. The composite with the HA volume fraction of 0.23 exhibited a Young's modulus nine times higher than that of UHMWPE, while the composite maintained the excellent toughness feature of UHMWPE. The fracture strain reached over 300%, significantly higher than other types of biocomposites. PMID:16564570

Fang, Liming; Leng, Yang; Gao, Ping

2006-07-01

118

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

119

Biological activity of lactoferrin-functionalized biomimetic hydroxyapatite nanocrystals.  

PubMed

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

120

The comparison of powder characteristics and physicochemical, mechanical and biological properties between nanostructure ceramics of hydroxyapatite and fluoridated hydroxyapatite  

Microsoft Academic Search

In this study, several fluorine-substituted hydroxyapatite ceramics with the general chemical formula Ca5(PO4)3(OH)1?xFx (0?x?1), where x=0.0 (hydroxyapatite; HA), x=0.68 (fluorhydroxyapatite; FHA) and x=0.97 (fluorapatite; FA) were prepared. The powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), F-selective electrode, atomic absorption spectroscopy (AAS) and EDTA titration analyses. The powders were

Hossein Eslami; Mehran Solati-Hashjin; Mohammadreza Tahriri

2009-01-01

121

Hydrogen microsphere hazard evaluation  

NASA Astrophysics Data System (ADS)

Progress on a preliminary hazard evaluation of hollow glass microspheres for hydrogen transport and storage is reported. The flammability and explosibility of representative hydrogen filled microspheres was assessed. The tests include dust cloud explosion; flame propagation; impact sensitivity; spark ignition; and autoignition furnace. The microspheres can be ignited and propagate flame either in the quiescent bulk form or as a suspended cloud. A preliminary comparison with flammability data for gaseous hydrogen and iron titanium hydride powder indicate that the autoignition temperature of hydrogen filled microspheres is comparable to that or the other forms of hydrogen, but suspended clouds of microspheres produce lower explosion pressures than hydride dust or hydrogen gas. Safety codes and government regulations pertinent to hydrogen filled microspheres are also reviewed.

Zalosh, R. G.; Bajpai, S. N.

1981-03-01

122

Effect of surface roughness of hydroxyapatite on human bone marrow cell adhesion, proliferation, differentiation and detachment strength  

Microsoft Academic Search

Initial attachment of osteoblast cells and mineralization phenomena are generally enhanced on rough, sandblasted substrata. In the present work the effect of surface roughness of hydroxyapatite (HA) on human bone marrow cell response was investigated. Human bone marrow cells were plated onto HA disc-shaped pellets, prepared from synthetic HA powder. The pellets were sintered and polished with SiC paper 180-,

Despina D Deligianni; Nikoleta D Katsala; Petros G Koutsoukos; Yiannis F Missirlis

2000-01-01

123

Chemical synthesis of poly(lactic-co-glycolic acid)\\/hydroxyapatite composites for orthopaedic applications  

Microsoft Academic Search

Hydroxyapatite-biodegradable polymer composites were synthesized by a colloidal non-aqueous chemical precipitation technique at room temperature. The starting materials used for synthesizing hydroxyapatite (HA, Ca10(PO4)6(OH)2) were Ca(NO3)2·4H2O and H3PO4, resulting in single phase HA while poly(d,l-lactic-co-glycolic acid) (PLGA) was used as the biodegradable polymer component. The composites were prepared containing 10, 20, and 30wt.% HA in the presence of the dissolved

Sarah E. Petricca; Kacey G. Marra; Prashant N. Kumta

2006-01-01

124

Dissolution of synthetic and bovine bone-derived hydroxyapatites fabricated by hot-pressing  

NASA Astrophysics Data System (ADS)

Dissolving behavior of hydroxyapatite (HA) ceramics prepared from bovine bone (BHA) was investigated and compared with synthetic HA. BHA power was obtained by calcining at 800 °C for 1 h to remove organics and then attritor-milling for 24 h. Synthetic HA and BHA powders were prepared by hot-pressing at 1000 °C for 0.5 h under the pressure of 30 MPa in Ar atmosphere. Sintered densities of the synthetic HA and the BHA were about 96% and 95%, respectively. The BHA consisted of mainly HA and small amount of magnesium oxide. Immersion test revealed that there was no clear evidence of dissolution for the BHA, whereas extensive dissolution on the surface of the synthetic HA occurred in buffered water. Accordingly, dense hydroxyapatite from bovine bone was more stable than synthetic HA in liquid environment.

Kim, Young Gook; Seo, Dong Seok; Lee, Jong Kook

2008-11-01

125

Effect of CaF 2 on densification and properties of hydroxyapatite–zirconia composites for biomedical applications  

Microsoft Academic Search

Hydroxyapatite (HA) composites with zirconia (ZrO2) up to 40vol% were fabricated with the addition of CaF2. The sinterability of the composites was found to be enhanced markedly by the addition of small amounts of CaF2 (<5vol%). Decomposition of HA to ?-TCP was suppressed due to the substitution of F? for OH?, consequently forming fluor-hydroxyapatite (FHA) solid solution. This suppression of

Hae-Won Kim; Yoon-Jung Noha; Young-Hag Koh; Hyoun-Ee Kim; Hyun-Man Kim

2002-01-01

126

Mechanical and in vivo performance of hydroxyapatite implants with controlled architectures  

Microsoft Academic Search

Internal architecture has a direct impact on the mechanical and biological behaviors of porous hydroxyapatite (HA) implant. However, traditional processing methods provide minimal control in this regard. To address the issue, we developed a new processing method combining image-based design and solid free-form fabrication. We have previously published the processing method showing fabricated HA implants and their chemical properties. This

T.-M. Gabriel Chu; David G. Orton; Scott J. Hollister; Stephen E. Feinberg; John W. Halloran

2002-01-01

127

Solid solution formation at the sintering of hydroxyapatite–fluorapatite ceramics  

Microsoft Academic Search

Fluorhydroxyapatite ceramics are increasingly studied for the use as biomaterials due to their good integration ability in the bone tissue and higher resorption resistance compared to the common hydroxyapatite (HA) ceramics. This study is aimed at the X-ray diffraction investigation of the interaction between HA and fluorapatite (FA) particulates in the sintering temperature range up to 1300 °C. The lattice

S. M. Barinov; L. I. Shvorneva; D. Ferro; I. V. Fadeeva; S. V. Tumanov

2004-01-01

128

Friction and wear of hydroxyapatite reinforced high density polyethylene against the stainless steel counterface  

Microsoft Academic Search

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

M. Wang; M. Chandrasekaran; W. Bonfield

2002-01-01

129

The effect of hydroxyapatite thickness on metal ion release from stainless steel substrates  

Microsoft Academic Search

The corrosion behaviour of 350 stainless steel coated with hydroxyapatite, HA, by plasma spraying was studied in Hank's Balanced Salt Solution, HBSS, and compared with that of polished passivated surfaces. Two different nominal thicknesses, 50 µm and 200 µm, corresponding to what one might consider a thin and a thick coating, respectively, were used. Only HA coatings with a thickness

S. R. Sousa; M. A. Barbosa

1995-01-01

130

Metallic coating of microspheres  

SciTech Connect

Extremely smooth, uniform metal coatings of micrometer thicknesses on microscopic glass spheres (microspheres) are often needed as targets for inertial confinement fusion (ICF) experiments. The first part of this paper reviews those methods used successfully to provide metal coated microspheres for ICF targets, including magnetron sputtering, electro- and electroless plating, and chemical vapor pyrolysis. The second part of this paper discusses some of the critical aspects of magnetron sputter coating of microspheres, including substrate requirements, the sticking of microspheres during coating (preventing a uniform coating), and the difficulties in growing the desired dense, smooth, uniform microstructure on continuously moving spherical substrates.

Meyer, S.F.

1980-08-15

131

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

132

Hydroxyapatite-binding peptides for bone growth and inhibition  

DOEpatents

Hydroxyapatite (HA)-binding peptides are selected using combinatorial phage library display. Pseudo-repetitive consensus amino acid sequences possessing periodic hydroxyl side chains in every two or three amino acid sequences are obtained. These sequences resemble the (Gly-Pro-Hyp).sub.x repeat of human type I collagen, a major component of extracellular matrices of natural bone. A consistent presence of basic amino acid residues is also observed. The peptides are synthesized by the solid-phase synthetic method and then used for template-driven HA-mineralization. Microscopy reveal that the peptides template the growth of polycrystalline HA crystals .about.40 nm in size.

Bertozzi, Carolyn R. (Berkeley, CA); Song, Jie (Shrewsbury, MA); Lee, Seung-Wuk (Walnut Creek, CA)

2011-09-20

133

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

134

Surface modification for titanium implants by hydroxyapatite nanocomposite  

PubMed Central

Background: Titanium (Ti) implants are commonly coated with hydroxyapatite (HA). However, HA has some disadvantages such as brittleness, low tensile strength and fracture toughness. It is desirable to combine the excellent mechanical properties of ZrO2 and the chemical inertness of Al2O3 with respect to the purpose of this project which was coating Ti implants with HA-ZrO2-Al2O3 to modify the surface of these implants by adding ZrO2 and Al2O3 to HA. The purpose of this study was to evaluate the efficacy of hydroxyapatite coating nonocomposite. Methods: From September 2009 to January2011, functionally graded HA-Al2O3-ZrO2 and HA coatings were applied on Ti samples. HA-Al2O3-ZrO2 and HA sols were orderly dip coated on the substrates and calcined. Scanning electron microscopy and EDS were used to estimate the particle size of the surfaces and for morphological analysis. The morphology of non-coated HA-coated HA-Al2O3-ZrO2 (composite-coated) and double-layer composite coated samples were compared with one other. Mechanical test (heat & quench) was also done for comparing single-phase (HA), composite and double-layer composite samples. Results: The morphology of HA-Al2O3-ZrO2 coating is more homogenous than HA-coated and uncoated samples. Furthermore, single-layer coating is more homogenous than double-layer coating. EDS analysis was done on HA-coated sample and showed that the Ca/P ratio in the film was similar to the theoretical value 1.67 in HA. Conclusion: Surface modification of Ti implants can be done by coating them with single-layer of HA-Al2O3-ZrO2. Single-layer hydroxyapatite-alumina-zirconia coated sample has the most homogenous morphology on the surface. PMID:24009915

Family, Roxana; Solati-Hashjin, Mehran; Namjoy Nik, Shahram; Nemati, Ali

2012-01-01

135

Controlled, sustained release of proteins via an injectable, mineral-coated microsphere delivery vehicle  

NASA Astrophysics Data System (ADS)

Hydroxyapatite interfaces have demonstrated strong protein binding and protein selection from a passing solution and can serve as a biocompatible carrier for controlled protein delivery. Hydroxyapatite is a major component of long bones and tooth enamel and is the most stable of all calcium phosphate isoforms in aqueous solutions at physiologic pH, providing a sensitive chromatographic mechanism for separating proteins. Here we describe an approach to create a synthetic hydroxyapatite coating through a biomimetic, heterogeneous nucleation from a modified simulated body fluid--supersaturated with calcium and phosphate ions on the surface of injectable polymer microspheres. We are able to bind and release bioactive growth factors into a variety of in vitro and in vivo conditions, demonstrating the functionality and advantage of the biomaterial. Creating a hydroxyapatite layer on the Poly(D,L-lactide-co-glycolide) (PLG) microsphere surface, avails the microsphere interior for another application that will not compete with protein binding and release. Encapsulating an imaging agent within the aqueous phase of the emulsion provides a visual reference for the injectable therapy upon microsphere fabrication. Another advantage of this system is that the mineral coating and subsequent protein binding is not compromised by the encapsulated imaging agent. This dual function delivery vehicle is not only advantageous for spatial tracking therapeutic applications, but also determining the longevity of the delivery vehicle once injected. In the broader sense, providing a mechanism to image and track our temporally controlled, sustained delivery system gives more evidence to support the effects of released protein on in vivo responses (bioactivity) and locate microspheres within different biological systems.

Franklin-Ford, Travelle

136

Hydroxyapatite adherence as a means to concentrate bacteria.  

PubMed Central

Adherence to hydroxyapatite (HA) was examined as a method to concentrate bacteria from foods. Using HA at a level of 10% and suspensions of an Escherichia coli strain containing 10(9), 10(6), and 10(3) cells per ml, kinetic studies revealed that maximum adherence was attained within 5 min for all cell concentrations and that comparable log reductions (1.0 to 1.5) of cells in suspension were seen regardless of initial cell concentration. Eleven species of spoilage and pathogenic bacteria were found to adhere to HA, with seven species adhering at proportions of greater than 95%. Fluorescent viability staining revealed that cells bound to HA remained viable. There was greater than 92% adherence of indigenous bacteria to HA from three of five 1:10 dilutions of ground beef, indicating promise for the use of HA for concentrating bacteria from meat and other food samples. PMID:9327570

Berry, E D; Siragusa, G R

1997-01-01

137

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

138

Characterization, Corrosion Resistance, and Cell Response of High-Velocity Flame-Sprayed HA and HA/TiO2 Coatings on 316L SS  

NASA Astrophysics Data System (ADS)

The main aim of this study is to evaluate corrosion and biocompatibility behavior of thermal spray hydroxyapatite (HA) and hydroxyapatite/titania bond (HA/TiO2)-coated 316L stainless steel (316L SS). In HA/TiO2 coatings, TiO2 was used as a bond coat between HA top coat and 316L SS substrate. The coatings were characterized by x-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy, and corrosion resistance determined for the uncoated substrate and the two coatings. The biological behavior was investigated by the cell culture studies using osteosarcoma cell line KHOS-NP (R-970-5). The corrosion resistance of the steel was found to increase after the deposition of the HA and HA/TiO2 bond coatings. Both HA, as well as, HA/TiO2 coatings exhibit excellent bond strength of 49 and 47 MPa, respectively. The cell culture studies showed that HA-coated 316L SS specimens appeared more biocompatible than the uncoated and HA/TiO2-coated 316L SS specimens.

Singh, Tejinder Pal; Singh, Harpreet; Singh, Hazoor

2012-09-01

139

Making Polymeric Microspheres  

NASA Technical Reports Server (NTRS)

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

140

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

141

Polyurethane Microspheres as Drug Carriers  

Microsoft Academic Search

Polyurethane microspheres were prepared by reacting polyethylene glycol [PEG] (of different molecular weights) with different mole ratios of tolylene diisocyanate. A conventional drug was incorporated into the microspheres. The polyurethane microspheres were characterized by FTIR, optical microscopy and particle size analysis. The equilibrium fluid content of microspheres was determined in suitable buffer media. The release pattern of the drug entrapped

P. V. Siva Reddy; G. N. Mahesh; S. Ramesh; P. A. Sivakumar; Ganga Radhakrishnan

1995-01-01

142

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

143

Metabolism of proteinoid microspheres  

NASA Technical Reports Server (NTRS)

The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolyis, decarboxylation, amination, deamination, and oxidoreduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres; these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature.

Nakashima, T.; Fox, S. W. (Principal Investigator)

1987-01-01

144

Metabolism of proteinoid microspheres  

NASA Technical Reports Server (NTRS)

The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolysis, decarboxylation, amination, deamination, and oxidoreduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres; these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature.

Nakashima, T.; Fox, S. W. (Principal Investigator)

1987-01-01

145

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

146

Effect of Thickness of HA-Coating on Microporous Silk Scaffolds Using Alternate Soaking Technology  

PubMed Central

Hydroxyapatite (HA) can be coated on various materials surface and has the function of osteogenicity. Microporous silk scaffold has excellent biocompatibility. In this study, alternate soaking technology was used to coat HA on microporous silk scaffolds. However, the cell proliferation was found to decrease with the increasing thickness (cycles of soaking) of HA-coating. This study aims to determine the best thickness (cycles of soaking) of HA-coating on microporous silk scaffolds. The SEM observation showed that group with one cycle of alternate soaking (1C-HA) has the most optimal porosity like non-HA-modified microporous silk scaffolds. The proliferation of osteoblasts has no significant difference between noncoated HA (N-HA) and 1C-HA groups, which are both significantly higher than those in two cycles of soaking (2C-HA) and three cycles of soaking (3C-HA) groups. The transcription levels of specific genes (runx2 and osteonectin) in osteoblasts of 1C-HA group were significantly higher than those of N-HA group. Moreover, the levels showed no significant difference among 1C-HA, 2C-HA, and 3C-HA groups. In conclusion, microporous silk scaffold with 1 cycle of HA-coating can combine the biocompatibility of silk and osteogenicity of HA. PMID:25093176

Zhu, Rui; Xue, Yingsen; Hao, Zhangying; Xie, Zhenghong; Fan, Xiangli; Fan, Hongbin

2014-01-01

147

Hydrothermal synthesis of hydroxyapatite  

NASA Astrophysics Data System (ADS)

A hydrothermal method of synthesizing hydroxyapatite by heating a precipitate, formed by mixing Ca(NO3)2bold dot4H2O and (NH4)2HPO4 with distilled water, in a hydrothermal reactor at 200 °C for 24-72 hrs is described. A treatment time of 24 hrs produced single phase (as shown by XRD) hydroxyapatite powder, however for longer treatment times XRD patterns were indicative of the presence of a secondary phase, monetite (CaHPO4). SEM examination of the treated powders displayed particles of rod-like morphology with dimensions 100-500 nm in length and 10-60 nm in diameter. Preliminary results on the use of the particles for the infiltration of dentine tubules are presented.

Earl, J. S.; Wood, D. J.; Milne, S. J.

2006-02-01

148

Effects of Human Milk on Adhesion of Streptococcus mutans to Saliva-Coated Hydroxyapatite in vitro  

Microsoft Academic Search

Adhesion of bacteria to pellicle-coated tooth surfaces is the first step in biofilm formation on teeth. The aim of this study was to explore whether human milk prevents or promotes adhesion of cariogenic Streptococcus mutans to saliva-coated hydroxyapatite (HA) using an in vitromodel system. S. mutans binding to HA coated with human parotid saliva (s-HA) or human milk was studied,

J. Wernersson; L. Danielsson Niemi; S. Einarson; O. Hernell; I. Johansson

2006-01-01

149

Reaction Sintering and Mechanical Properties of Hydroxyapatite-Zirconia Composites with Calcium Fluoride Additions  

Microsoft Academic Search

The effects of calcium fluoride (CaF2) additions on the densi- fication and mechanical properties of hydroxyapatite-zirconia composites (HA-ZrO2) were investigated. When small amount of CaF2 was added, the density of the composites was markedly enhanced. The reactions of HA with CaF2, which led to the formation of fluorapatite (FA), were attributed to the observed improvements in densification. When HA-20-vol%-ZrO2 com-

Hae-Won Kim; Young-Hag Koh; Byung-Ho Yoon; Hyoun-Ee Kim

2002-01-01

150

Porous ZrO 2 bone scaffold coated with hydroxyapatite with fluorapatite intermediate layer  

Microsoft Academic Search

Highly porous zirconia (ZrO2) bone scaffolds, fabricated by a replication technique using polymeric sponge, were coated with hydroxyapatite (HA). To prevent the chemical reactions between ZrO2 and HA, an intermediate fluorapatite (FA) layer was introduced. The strength of the porous ZrO2 was higher than that of pure HA by a factor of 7, suggesting the feasibility of ZrO2 porous scaffolds

Hae-Won Kim; Seung-Yong Lee; Chang-Jun Bae; Yoon-Jung Noh; Hyoun-Ee Kim; Hyun-Man Kim; Jea Seung Ko

2003-01-01

151

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

152

Histomorphometric analysis of rat alveolar wound healing with hydroxyapatite alone or associated to BMPs.  

PubMed

Several materials and techniques have been proposed to improve alveolar wound healing and decrease loss of bone height and thickness that normally follow dental extraction. The objective of this research was the histologic analysis of bone morphogenetic proteins implanted into dental alveoli of rats after extraction. A total of 45 adult male Wistar rats were divided into three groups of 15 animals each: control (no treatment), implanted with pure hydroxyapatite (HA, 3 mg) and implanted with hydroxyapatite plus bone morphogenetic proteins (HA/BMPs, 3 mg). Five animals from each group were sacrificed at 7, 21 and 42 days after extraction for the histometric analyses of the osteoconductive potential of hydroxyapatite associated or not with BMPs. After dissection, fixation, decalcification and serial microtomy of 6-micron thick sections, the samples were stained with hematoxylin-eosin for histologic and histometric analyses. Both HA and HA/BMPs caused a delay in wound healing compared to control animals, evaluated by the percentage of bone tissue in the alveoli. The treatment with HA/BMPs had the greatest delay at 21 days, even though it produced values similar to the control group at 42 days. The materials did not improve alveolar repair in the normal period of wound healing and the association of HA/BMPs did not have osteoconductive properties with granulated hydroxyapatite as the vehicle. PMID:12428586

Brandão, Alexandre C; Brentegani, Luís Guilherme; Novaes, Arthur B; Grisi, Márcio Fernando M; Souza, Sérgio Luís Scombatti de; Taba Júnior, Mario; Salata, Luiz Antônio

2002-01-01

153

Hydroxyapatite grafted carbon nanotubes and graphene nanosheets: promising bone implant materials.  

PubMed

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. PMID:24892524

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

2014-11-11

154

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

155

Microsphere Insulation Panels  

NASA Technical Reports Server (NTRS)

Microsphere insulation panels (MIPs) have been developed as lightweight, longlasting replacements for the foam and vacuum-jacketed systems heretofore used for thermally insulating cryogenic vessels and transfer ducts. The microsphere core material of a typical MIP consists of hollow glass bubbles, which have a combination of advantageous mechanical, chemical, and thermal-insulation properties heretofore available only separately in different materials. In particular, a core filling of glass microspheres has high crush strength and low density, is noncombustible, and performs well in soft vacuum.

Mohling, R.; Allen, M.; Baumgartner, R.

2006-01-01

156

Dual functional selenium-substituted hydroxyapatite  

PubMed Central

Hydroxyapatite (HA) doped with trace elements has attracted much attention recently owing to its excellent biological functions. Herein, we use a facile co-precipitation method to incorporate selenium into HA by adding sodium selenite during synthesis. The obtained selenium-substituted HA products are needle-like nanoparticles which have  size and crystallinity that are similar to those of the pure HA nanoparticles (HANs) when the selenium content is low. HANs are found to have the ability to induce the apoptosis of osteosarcoma cells, and the anti-tumour effects are enhanced after incorporation of selenium. Meanwhile, the nanoparticles can also support the growth of bone marrow stem cells. Furthermore, the flow cytometric results indicate that the apoptosis induction of osteosarcoma cells is caused by the increased reactive oxygen species and decreased mitochondrial membrane potential. These results show that the selenium-substituted HANs are potentially promising bone graft materials in osteosarcoma treatment due to their dual functions of supporting normal cell growth and inducing tumour cell apoptosis. PMID:23741613

Wang, Yanhua; Ma, Jun; Zhou, Lei; Chen, Jin; Liu, Yonghui; Qiu, Zhiye; Zhang, Shengmin

2012-01-01

157

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

158

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

159

Influence of interphase layer on the overall elasto-plastic behaviors of HA\\/PEEK biocomposite  

Microsoft Academic Search

A three-dimensional finite element unit cell model has been designed and constructed for studying mechanical properties of hydroxyapatite (HA) reinforced polyetheretherketone (PEEK) biocomposite. The model consists of an elastic-brittle HA spherical particle, an elasto-plastic matrix and an interphase layer between the particle and the matrix. The interphase layers with four different kinds of material behaviors have been taken into consideration

J. P. Fan; C. P. Tsui; C. Y. Tang; C. L. Chow

2004-01-01

160

Towards optimization of the silanization process of hydroxyapatite for its use in bone cement formulations.  

PubMed

The aim of this work was to provide some fundamental information for optimization of silanization of hydroxyapatite intended for bone cement formulations. The effect of 3-(trimethoxysilyl) propyl methacrylate (MPS) concentration and solvent system (acetone/water or methanol/water mixtures) during HA silanization was monitored by X-ray diffraction (XRD), FTIR spectroscopy and EDX analysis. The effect of silanized HA on the mechanical properties of acrylic bone cements is also reported. It was found that the silanization process rendered hydroxyapatite with lower crystallinity compared to untreated HA. Through EDX, it was observed that the silicon concentration in the HA particles was higher for acetone-water than that obtained for methanol-water system, although the mechanical performance of cements prepared with these particles exhibited the opposite behavior. Taking all these results together, it is concluded that methanol-water system containing MPS at 3wt.% provides the better results during silanization process of HA. PMID:24857478

Cisneros-Pineda, Olga G; Herrera Kao, Wilberth; Loría-Bastarrachea, María I; Veranes-Pantoja, Yaymarilis; Cauich-Rodríguez, Juan V; Cervantes-Uc, José M

2014-07-01

161

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

162

Compartmentalization in proteinoid microspheres  

NASA Technical Reports Server (NTRS)

Proteinoid microspheres with stable internal compartments and internal structure are made from acidic proteinoid and basic proteinoid with calcium. The populations of microspheres are characterized by a wide diversity of structure. A model of primitive intracellular communication is suggested by the observed movement of internal particles between compartments of a multicompartmentalized unit. Differential response to pH change and to temperature change has been demonstrated within one population and suggests one mode of adaptive selection among primordial cell populations.

Brooke, S.; Fox, S. W.

1977-01-01

163

Evaluation of hydroxyapatite as a metal immobilizing soil additive for the remediation of polluted soils. Part 1. Influence of hydroxyapatite on metal exchangeability in soil, plant growth and plant metal accumulation  

Microsoft Academic Search

In order to evaluate the possible use of hydroxyapatite (HA) as a soil additive for the in situ remediation of metal contaminated soils, the immobilizing capacity of this product was investigated. Three different concentrations of HA (0.5%, 1%, and 5% by weight (w\\/w)) were applied to a metal (Zn, Pb, Cu, Cd) and As contaminated soil originating from an old

J. Boisson; A. Ruttens; M. Mench; J. Vangronsveld

1999-01-01

164

Effect of trisodium citrate on electrolytic deposition of hydroxyapatite coatings.  

PubMed

Hydroxyapatite coatings were deposited on the titanium substrate by using various content Na?Cit as an organic modifier in electrolytes. The influence of the Na?Cit on the sizes of the HA crystals during electrolytic deposition was investigated under different molar ratio of Na?Cit to calcium ions. The experimental results showed that the size of HA crystal was well controlled by the addition of Na?Cit. When the molar ratio of Na?Cit to calcium ions was equal or greater than five, the obtained HA coating consisted of nanosized crystals. The HA nanoparticles were precipitated without a precursor phase when the molar ratio of Na?Cit to calcium ions was five; otherwise, the CaP coating experienced a phase conversion from octacalcium phosphate (OCP) to HA during the ELD. The effect of pH on saturation indexes with respect to hydroxyapatite, OCP, and dicalcium dihydrogen phosphate of these electrolytes was calculated by a computer program PHREEQC. The calculation showed the nucleation of OCP as the precursor during the deposition could be inhibited with increasing Na?Cit content in the electrolytes. PMID:21086428

Lin, Dong-Yang; Wang, Xiao-Xiang; Jiang, Yong

2011-01-01

165

Growth of hydroxyapatite in a biocompatible mesoporous ordered silica.  

PubMed

A novel biomaterial (HA-SBA-15) has been developed based on the growth of calcium phosphate hydroxyapatite (HA) nanoparticles within an organized silica structure (SBA-15). Characterization of the material was carried out using a combination of X-ray diffraction, X-ray fluorescence, transmission electron microscopy, N2 adsorption-desorption isotherms and nuclear magnetic resonance. Transmission electron microscopy observations and N2 porosimetry revealed the crystallization of hydroxyapatite nanoparticles inside the mesopore cavities of the silica structure. Specific surface areas of 760 m2 g(-1) and 260 m2 g(-1) were measured for the SBA-15 and the HA-SBA-15 material, respectively. The hydroxyl groups present in the silica nanostructure surface have brought about cationic defects in the silicium sites, mainly with those of tetrahedral symmetry, and promoted the formation of siloxanes. 29Si MAS-NMR analysis shows a significant reduction of the silanol groups concentration with HA growing within the base (SBA-15) material. Studies and brain tissue biocompatibility tests were carried out. Histopathological studies on the SBA-15 implant material showed no changes to the tissue nearby. The results confirmed the synthesis of a silica-based composite containing HA nanoparticles with the potential for biomedical applications. PMID:16701875

Díaz, A; López, T; Manjarrez, J; Basaldella, E; Martínez-Blanes, J M; Odriozola, J A

2006-03-01

166

The effect of cadmium on the formation and properties of hydroxyapatite In vitro and its relation to cadmium toxicity in the skeletal system  

Microsoft Academic Search

In order to understand the biological action of cadmium (Cd) in inducing bone pathologies, the effect of Cd on the formation, structure, and properties of hydroxyapatite (HA) in vitro was investigated using three biologically relevant test systems: (1) direct precipitation of HA with no precursor phase; (2) transformation of amorphous calcium phosphate (ACP) to crystalline HA; and (3) growth of

N. C. Blumenthal; V. Cosma; D. Skyler; J. LeGeros; M. Walters

1995-01-01

167

Post-translational modification of osteopontin: Effects on in vitro hydroxyapatite formation and growth  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Thrombin-cleaved fragments of milk-osteopontin effect hydroxyapatite formation differently. Black-Right-Pointing-Pointer N- and C-terminal fragments promoted hydroxyapatite formation and growth. Black-Right-Pointing-Pointer A central fragment inhibited hydroxyapatite formation and growth. Black-Right-Pointing-Pointer Binding to collagen or hydroxyapatite seed crystals modified these effects. -- Abstract: The manuscript tests the hypothesis that posttranslational modification of the SIBLING family of proteins in general and osteopontin in particular modify the abilities of these proteins to regulate in vitro hydroxyapatite (HA) formation. Osteopontin has diverse effects on hydroxyapatite (HA) mineral crystallite formation and growth depending on the extent of phosphorylation. We hypothesized that different regions of full-length OPN would also have distinct effects on the mineralization process. Thrombin fragmentation of milk OPN (mOPN) was used to test this hypothesis. Three fragments were tested in a de novo HA formation assay; an N-terminal fragment (aa 1-147), a central fragment (aa 148-204) denoted SKK-fragment and a C-terminal fragment (aa 205-262). Compared to intact mOPN the C- and N-terminal fragments behaved comparably, promoting HA formation and growth, but the central SKK-fragment acted as a mineralization inhibitor. In a seeded growth experiment all fragments inhibited mineral proliferation, but the SKK-fragment was the most effective inhibitor. These effects, seen in HA-formation and seeded growth assays in a gelatin gel system and in a pH-stat experiment were lost when the protein or fragments were dephosphorylated. Effects of the fully phosphorylated protein and fragments were also altered in the presence of fibrillar collagen. The diverse effects can be explained in terms of the intrinsically disordered nature of OPN and its fragments which enable them to interact with their multiple partners.

Boskey, Adele L., E-mail: boskeya@hss.edu [Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY (United States); Christensen, Brian, E-mail: bc@mb.au.dk [Department of Molecular Biology and Genetics, Aarhus University (Denmark)] [Department of Molecular Biology and Genetics, Aarhus University (Denmark); Taleb, Hayat, E-mail: Talebh@hss.edu [Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY (United States)] [Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY (United States); Sorensen, Esben S., E-mail: ess@mb.au.dk [Department of Molecular Biology and Genetics, Aarhus University (Denmark)

2012-03-09

168

Nanosilicon carbide/hydroxyapatite nanocomposites: structural, mechanical and in vitro cellular properties.  

PubMed

In this study, bioceramic nanocomposites were synthesized by sintering compacted bodies of hydroxyapatite (HA) mixed with 5 or 15 wt% nanosilicon carbide at 1,100 or 1,200 degrees C in a reducing atmosphere. Pure hydroxyapatite was also prepared for comparison. Phase compositions, structural and physical properties of the composites were studied using appropriate techniques. Some in vitro biological properties of the composites were also investigated by using newrat calvaria osteoblastic cells. X-ray diffraction analysis indicated that tricalcium phosphate (TCP) comprising negligible alpha-TCP and considerable beta-TCP were formed in composites during sintering meanwhile hydroxyapatite and silicon carbide (SiC) were also existed in the composition. Based on the results, that composite made of 5 wt% nanosilicon carbide exhibited higher bending strength, fracture toughness and bulk density than pure HA and composite with 15 wt% silicon carbide. The scanning electron microscopy coupled with energy dispersive X-ray analysis revealed that the addition of nanosilicon carbide suppressed the grain growth and yielded a feature of island-type clusters consisting of blistered calcium phosphate (HA and TCP) and SiC grains. Also, in this study, better proliferation rate and alkaline phosphatase activity were observed for the osteoblastic cells seeded on top of the composites compared to pure HA. Overall, the results indicated that the composite of 95 wt% hydroxyapatite and 5 wt% SiC exhibited better mechanical and biological properties than pure HA and further addition of SiC failed strength and toughness. PMID:20376539

Hesaraki, Saeed; Ebadzadeh, Touraj; Ahmadzadeh-Asl, Shaghayegh

2010-07-01

169

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

170

Comparing Microspheres with Different Internal Phase of Polyelectrolyte as Local Drug Delivery System for Bone Tuberculosis Therapy  

PubMed Central

We use hydrophobic poly(lactic-co-glycolic) acid (PLGA) to encapsulate hydrophilic ofloxacin to form drug loading microspheres. Hyaluronic acid (HA) and polylysine (Pls) were used as internal phase additives to see their influences on the drug loading and releasing. Double emulsion (water-in-oil-in-water) solvent extraction/evaporation method was used for the purpose. Particle size analysis display that the polyelectrolytes have low impact on the microsphere average size and distribution. Scanning electron microscope (SEM) pictures show the wrinkled surface resulted by the internal microcavity of the microspheres. Microspheres with HA inside have higher drug loading amounts than microspheres with Pls inside. The loading drug amounts of the microspheres increase with the HA amounts inside, while decreasing with the Pls amounts inside. All the polyelectrolytes adding groups have burst release observed in experiments. The microspheres with Pls internal phase have faster release rate than the HA groups. Among the same polyelectrolyte internal phase groups, the release rate increases with the amounts increasing when Pls is inside, while it decreases with the amounts increasing when HA is inside. PMID:24707480

Chen, Long; Li, Hong; Deng, Chun-Ling; Chen, Xiao-Feng

2014-01-01

171

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

172

Synthesis of nanosized hydroxyapatite powders.  

PubMed

Hydroxyapatite powder was mechanochemically synthesized from calcium pyrophosphate (Ca2P2O7) and calcium carbonate (CaCO3) using a solid-state reaction. The two powders were mixed in distilled water, milled for 8 hours, dried and calcined at 1100 degrees C for 1 hour. The phase(s) formed was analyzed by x-ray diffraction (XRD). It was found that hydroxyapatite was not the only one formed. This result will be used as the starting point to produce a single-phase hydroxyapatite in terms of excess hydroxyl group in a mechanochemical reaction. PMID:15468867

Zarina, O; Radzali, O

2004-05-01

173

Biodegradation behavior of ultra-high-strength hydroxyapatite\\/poly ( l-lactide) composite rods for internal fixation of bone fractures  

Microsoft Academic Search

The purpose of this study was to investigate the biodegradation behavior of the ultra-high-strength hydroxyapatite\\/(l-lactide) (HA\\/PLLA) composite rods for fracture repair. Two kinds of composite materials were used in this study: u-HA\\/PLLA, which contained 30% by weight of uncalcined HA as reinforcing particles, and c-HA\\/PLLA, which contained 30% by weight of calcined HA as reinforcing particles. These composite rods were

Taizo Furukawa; Yoshitaka Matsusue; Tsunoru Yasunaga; Yasuo Shikinami; Masaki Okuno; Takashi Nakamura

2000-01-01

174

Microsphere contrast agents for OCT  

E-print Network

409 CHAPTER 29 Microsphere contrast agents for OCT Stephen A Boppart Kenneth S Suslick INTRODUCTION in achieving this goal for OCT15 , with the development of contrast agents such as microspheres16 describes the fabrication, characterization and application of a new class of engineered protein microsphere

Suslick, Kenneth S.

175

Thermal Transpiration in Microsphere Membranes  

Microsoft Academic Search

Self-assembled glass microsphere membranes as an alternative transpiration membrane for application in a Knudsen Compressor are discussed. A performance model is constructed and used to compare the performance of glass microsphere membranes to silicon aerogel membranes for this application. An initial experimental Knudsen Compressor stage based on glass microsphere membranes has been designed and experimentally tested. Preliminary performance results show

Marcus Young; Yen Lin Han; E. P. Muntz; G. Shiflett; Andrew Ketsdever; Amanda Green

2003-01-01

176

Strontium-substituted hydroxyapatite coatings deposited via a co-deposition sputter technique.  

PubMed

The bioactivity of hydroxyapatite (HA) coatings can be modified by the addition of different ions, such as silicon (Si), lithium (Li), magnesium (Mg), zinc (Zn) or strontium (Sr) into the HA lattice. Of the ions listed here, strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as Sr has been shown to promote osteoblast proliferation and differentiation, and reduce osteoclast activity. In this study, SrHA coatings were deposited onto titanium substrates using radio frequency (RF) magnetron co-sputtering (and compared to those surfaces deposited from HA alone). FTIR, XPS, XRD, and SEM techniques were used to analyse the different coatings produced, whereby different combinations of pure HA and 13% Sr-substituted HA targets were investigated. The results highlight that Sr could be successfully incorporated into the HA lattice to form SrHA coatings. It was observed that as the number of SrHA sputtering targets in the study were increased (increasing Sr content), the deposition rate decreased. It was also shown that as the Sr content of the coatings increased, so did the degree of preferred 002 orientation of the coating (along with obvious changes in the surface morphology). This study has shown that RF magnetron sputtering (specifically co-sputtering), offers an appropriate methodology to control the surface properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface morphology. PMID:25491990

Boyd, A R; Rutledge, L; Randolph, L D; Meenan, B J

2015-01-01

177

Chemical characterization of some substituted hydroxyapatites  

PubMed Central

Synthetic multi-substituted hydroxyapatite nano powders containing silicon and or carbonate prepared by a wet chemical method. The process parameters are set up to allow the simultaneous substitution of carbonate and silicon ions in the place of phosphorus. The chemical and structural characterizations of the prepared powders are determined with the aid of; XRF, ICP, XRD and FTIR. The results show that, the ion substitution in the crystal lattice of HA caused a change in the unit cell dimensions and affected the degree of crystallization of the produced powders. The apatite formation abilityy of the prepared discs from the synthesized powders is determined by immersing in SBF solution for different periods. The degree of ion release was determined in the obtained solutions. The examined surface of the immersed discs under SEM and analyzed by CDS showed a more dense HA layer than those of un-substituted ones. The HA with the substituted silicon and carbonate ions, showed the highest solubility with greater rate of ion release, compared with carbonate-free powder. All prepared powders took sodium ion from the SBF solution during immersion, which was not recorded before. PMID:22122971

2011-01-01

178

Comparison of murine fibroblast cell response to fluor-hydroxyapatite composite, fluorapatite and hydroxyapatite by eluate assay.  

PubMed

Fluorapatite (FA) is one of the inorganic constituents of bone or teeth used for hard tissue repairs and replacements. Fluor-hydroxyapatite (FHA) is a new synthetic composite that contains the same molecular concentration of OH(-) groups and F(-) ions. The aim of this experiment was to evaluate the cellular responses of murine fibroblast NIH-3T3 cells in vitro to solid solutions of FHA and FA and to compare them with the effect of hydroxyapatite (HA). We studied 24, 48 and 72 h effects of biomaterials on cell morphology, proliferation and cell cycle of NIH-3T3 cells by eluate assay. Furthermore, we examined the ability of FHA, FA and HA to induce cell death and DNA damage. Our cytotoxic/antiproliferative studies indicated that any of tested biomaterials did not cause the total inhibition of cell division. Biomaterials induced different antiproliferative effects increasing in the order HA < FHA < FA which were time- and concentration-dependent. None of the tested biomaterials induced necrotic/apoptotic death of NIH-3T3 cells. On the other hand, after 72 h we found that FHA and FA induced G0/G1 arrest of NIH-3T3 cells, while HA did not affect any cell cycle phases. Comet assay showed that while HA demonstrated weaker genotoxicity, DNA damage induced by FHA and FA caused G0/G1 arrest of NIH-3T3 cells. Fluoridation of hydroxyapatite and different FHA and FA structure caused different cell response of NIH-3T3 cells to biomaterials. PMID:19378927

Jantová, Sona; Letasiová, Silvia; Theiszová, Marica; Palou, M

2009-03-01

179

Synthesis of sodium caseinate-calcium carbonate microspheres and their mineralization to bone-like apatite  

NASA Astrophysics Data System (ADS)

Phosphoproteins can induce and stabilize calcium carbonate (CaCO3) vaterite, which has desirable features for high reactivity. The purpose of this study was to synthesize bioactive CaCO3 microspheres for bone regeneration. Sodium caseinate (NaCas)-containing CaCO3 microspheres, with the crystal phase of vaterite, were synthesized by fast precipitation in an aqueous solution of CaCl2, Na2CO3, and 2 mg/mL of NaCas. The uniform microspheres exhibited rougher surfaces and lower negative charges than CaCO3 particles without NaCas addition. Fourier-transform infrared spectroscopy (FT-IR) of the microspheres showed characteristic peaks or bands corresponding to phosphate and hydroxyl groups. Thermogravimetric analysis (TGA) curves exhibited approximately 5% weight loss below 600 °C due to the decomposition of NaCas. Scanning electron microscope (SEM) images showed lath-like hydroxyapatite (HAp) on the surface after soaking in simulated body fluid (SBF) at 37 °C for 5 and 10 days. Energy dispersive X-ray spectrometry (EDS) revealed that the agglomerates were composed of Ca, C, O, P, Na, and Mg elements, and the Ca/P ratios ranged from 1.53 to 1.56. X-ray diffraction (XRD) patterns exhibited peaks characteristic of hydroxyapatite. The results of this study demonstrated that the addition of NaCas induced the formation of vaterite microspheres which possesses an enhanced apatite formation after soaking in SBF at 37 °C for 5 and 10 days. These NaCas-CaCO3 microspheres may be a potential biomaterial for bone regeneration.

Xu, Zhewu; Liang, Guobin; Jin, Lin; Wang, Zhenling; Xing, Chao; Jiange, Qing; Zhang, Zhiguang

2014-06-01

180

Formation of hydroxyapatite coating using novel chemo-biomimetic method.  

PubMed

A novel chemo-biomimetic method was developed to deposit hydroxyapatite (HA), simulating the porous nano-scale structure and chemical composition of natural bone. Electrochemical activation in NaOH solution, a prerequisite process to heterogeneously nucleate hydroxyapatite in this investigation, creates nano-scale porous structure on the surface of Ti6Al4V alloy. XPS analysis confirmed that the surface of activated Ti6Al4V substrate converted to TiO2 during activation, existing in the form of hydrated TiO2. Benefiting from the biocompatible top-layer of hydrated TiO2 and the favorable alkaline surface chemistry created through the electrochemical activation, the HA coating nucleates heterogeneously and grows continuously on the activated substrate resembling the nano-scale porous bone-like structure. The coating was characterized using XRD, SEM/FESEM/EDX, TEM and FTIR, and was confirmed as pure hydroxyapatite. A coating thickness of 50 microm was achieved, which is preferable and acceptable for medical implant application to promote bone ingrowth, thus enhancing fixation and biocompatibility of implant surface. PMID:18452030

Xie, Jianhui; Luan, Ben Li

2008-10-01

181

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

182

Bioactive glass/hydroxyapatite composites: Mechanical properties and biological evaluation.  

PubMed

Bioactive glass/hydroxyapatite composites for bone tissue repair and regeneration have been produced and discussed. The use of a recently developed glass, namely BG_Ca/Mix, with its low tendency to crystallize, allowed one to sinter the samples at a relatively low temperature thus avoiding several adverse effects usually reported in the literature, such as extensive crystallization of the glassy phase, hydroxyapatite (HA) decomposition and reaction between HA and glass. The mechanical properties of the composites with 80wt.% BG_Ca/Mix and 20wt.% HA are sensibly higher than those of Bioglass® 45S5 reference samples due to the presence of HA (mechanically stronger than the 45S5 glass) and to the thermal behaviour of the BG_Ca/Mix, which is able to favour the sintering process of the composites. Biocompatibility tests, performed with murine fibroblasts BALB/3T3 and osteocites MLO-Y4 throughout a multi-parametrical approach, allow one to look with optimism to the produced composites, since both the samples themselves and their extracts do not induce negative effects in cell viability and do not cause inhibition in cell growth. PMID:25842126

Bellucci, Devis; Sola, Antonella; Anesi, Alexandre; Salvatori, Roberta; Chiarini, Luigi; Cannillo, Valeria

2015-06-01

183

Doppler cooling a microsphere  

E-print Network

Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity dependent scattering force from narrow whispering gallery mode (WGM) resonances is described. Light that is red detuned from the WGM resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. Leakage of photons out of the microsphere when the incident field is near resonant with the narrow WGM resonance acts to damp the motion of the sphere. The scattering force is not limited by saturation, but can be controlled by the incident power. Cooling times on the order of seconds are calculated for a 20 micron diameter silica microsphere trapped within optical tweezers, with a Doppler temperature limit in the microKelvin regime.

P. F. Barker

2010-04-08

184

Doppler cooling a microsphere  

E-print Network

Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity dependent scattering force from narrow whispering gallery mode (WGM) resonances is described. Light that is red detuned from the WGM resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. Leakage of photons out of the microsphere when the incident field is near resonant with the narrow WGM resonance acts to damp the motion of the sphere. The scattering force is not limited by saturation, but can be controlled by the incident power. Cooling times on the order of seconds are calculated for a 20 micron diameter silica microsphere trapped within optical tweezers, with a Doppler temperature limit in the microKelvin regime.

Barker, P F

2010-01-01

185

Osteogenic Properties of PBLG-g-HA/PLLA Nanocomposites  

PubMed Central

New development of biomaterial scaffolds remains a prominent issue for the regeneration of lost or fractured bone. Of these scaffolds, a number of bioactive polymers have been synthesized and fabricated for diverse biological roles. Although recent evidence has demonstrated that composite scaffolds such as HA/PLLA have improved properties when compared to either HA or PLLA alone, recent investigations have demonstrated that the phase compatibility between HA and PLLA layers is weak preventing optimal enhancement of the mechanical properties and making the composites prone to breakdown. In the present study, poly (?-benzyl-L-glutamate) modified hydroxyapatite/(poly (L-lactic acid)) (PBLG-g-HA/PLLA) composite scaffolds were fabricated with improved phase compatibility and tested for their osteogenic properties in 18 Wistar female rats by analyzing new bone formation in 3 mm bilateral femur defects in vivo. At time points, 2, 4 and 8 weeks post surgery, bone formation was evaluated by µ-CT and histological analysis by comparing 4 treatment groups; 1) blank defect, 2) PLLA, 3) HA/PLLA and 4) PBLG-g-HA/PLLA scaffolds. The in vivo analysis demonstrated that new bone formation was much more prominent in HA/PLLA and PBLG-g-HA/PLLA groups as depicted by µ-CT, H&E staining and immunohistochemistry for collagen I. TRAP staining was also utilized to determine the influence of osteoclast cell number and staining intensity to the various scaffolds. No significant differences in either staining intensity or osteoclast numbers between all treatment modalities was observed, however blank defects did contain a higher number of osteoclast-like cells. The results from the present study illustrate the potential of PBLG-g-HA/PLLA scaffolds for bone tissue engineering applications by demonstrating favorable osteogenic properties. PMID:25184285

Liao, Lan; Yang, Shuang; Miron, Richard J.; Wei, Junchao; Zhang, Yufeng; Zhang, Meng

2014-01-01

186

In vitro studies of human and rat osteoclast activity on hydroxyapatite, ?-tricalcium phosphate, calcium carbonate  

Microsoft Academic Search

Investigations on the ceramic degradation caused by osteoclasts are designed to assess osteoclast–ceramic interactions and to determine which ceramics are more suitable for use as bone substitute. This study investigated the resorptive activity of osteoclasts on ceramics presenting different solubility rates. Osteoclasts isolated from new-born rat and from human giant cell tumour were cultured on different bioceramics: hydroxyapatite (HA), ?-tricalcium

F Monchau; A Lefèvre; M Descamps; A Belquin-myrdycz; P Laffargue; H. F Hildebrand

2002-01-01

187

Deposition of hydroxyapatite thin films by Nd:YAG laser ablation: a microstructural study  

SciTech Connect

Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation at {lambda} = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 deg. C and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at {lambda} = 335 nm laser wavelength and 300 deg. C substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP)

Nistor, L.C. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania); Ghica, C. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania); Teodorescu, V.S. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania); Nistor, S.V. [National Institute of Materials Physics, P.O. Box MG-7, Magurele, RO-76900, Bucharest (Romania)]. E-mail: snistor@alpha1.infim.ro; Dinescu, M. [National Institute of Lasers, Plasma and Radiation Physics, P.O. Box MG-26, Magurele, RO-76900, Bucharest (Romania); Matei, D. [National Institute of Lasers, Plasma and Radiation Physics, P.O. Box MG-26, Magurele, RO-76900, Bucharest (Romania); Frangis, N. [Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki (Greece); Vouroutzis, N. [Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki (Greece); Liutas, C. [Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki (Greece)

2004-11-02

188

Mechanical and dynamic viscoelastic properties of hydroxyapatite reinforced poly(?-caprolactone)  

Microsoft Academic Search

Poly(?-caprolactone)\\/hydroxyapatite (PCL\\/HA) composites as potential bone substitutes were prepared by melt-blending. The melting, crystallization and glass transition temperatures deduced from differential scanning calorimetery and dynamic mechanical thermal analysis (DMTA) were all changed by the addition of HA, suggesting an interaction at the interface of these two phases. Quasi-static mechanical testing shows that the yield strength and Young's modulus of PCL

Biqiong Chen; Kang Sun

2005-01-01

189

Low-intensity pulsed ultrasound increases bone ingrowth into porous hydroxyapatite ceramic  

Microsoft Academic Search

Synthetic porous ceramic made of hydroxyapatite (HA) has been used as a bone graft substitute. In the present study we investigated\\u000a whether low-intensity pulsed ultrasound (LIPUS) accelerates bone ingrowth into the pores of HA ceramic. Application of LIPUS\\u000a did not mechanically weaken porous ceramic that was immersed in water in vitro. In vivo experiments using rabbits showed that\\u000a LIPUS application

Takao Iwai; Yoshifumi Harada; Koichi Imura; Sadahiro Iwabuchi; Junko Murai; Kunihiko Hiramatsu; Akira Myoui; Hideki Yoshikawa; Noriyuki Tsumaki

2007-01-01

190

The use of hydroxyapatite granules for the correction of skeletal facial deformities  

Microsoft Academic Search

Augmentation of the craniomaxillofacial region is required for many esthetic and reconstructive procedures. Although a variety\\u000a of different materials and techniques have been described, coral-derived hydroxyapatite granules (HA), which are biocompatible\\u000a with bone, seem to be the ideal material. In the past 25 years, we have observed HA granules to be a safe, stable, easy to\\u000a use, and cost-effective material that

Puneet Tuli; Frank Farbod; Barbara Beal; Ian T. Jackson

191

Influence of Fluoride on the Rate of Dissolution of Hydroxyapatite in Acidic Buffer Solution  

Microsoft Academic Search

The solubility of powdered hydroxyapatite (HA) in acidic buffer solution (pH 4.65) was reduced by 71% by adding sufficient fluoride (F––; either by previously treating the HA with NaF solution or by introducing NaF at the start of the dissolution) to replace approximately 25% of all surface unit cell OH–– ions. The same amount of F–– was less effective if

D. S. Magrill

1975-01-01

192

High-affinity integration of hydroxyapatite nanoparticles with chemically modified silk fibroin  

Microsoft Academic Search

Hydroxyapatite (HA)-based nanocomposites were prepared by a co-precipitation method with silk fibroin (SF) serving as organic\\u000a matrix. Silk fibroin was chemically modified with an alkali solution or an enzyme attempting to improve the interface between\\u000a the mineral and the organic matrix. The influences of the alkali and enzyme pretreatments on microstructure and physicochemical\\u000a properties of HA–SF composite were examined and

Li Wang; Chunzhong Li; Mamoru Senna

2007-01-01

193

Biocompatibility and osteogenesis of biomimetic nano-hydroxyapatite\\/polyamide composite scaffolds for bone tissue engineering  

Microsoft Academic Search

In this study, we prepared nano-hydroxyapatite\\/polyamide (n-HA\\/PA) composite scaffolds utilizing thermally induced phase inversion processing technique. The macrostructure and morphology as well as mechanical strength of the scaffolds were characterized. Mesenchymal stem cells (MSCs) derived from bone marrow of neonatal rabbits were cultured, expanded and seeded on n-HA\\/PA scaffolds. The MSC\\/scaffold constructs were cultured for up to 7 days and

Huanan Wang; Yubao Li; Yi Zuo; Jihua Li; Sansi Ma; Lin Cheng

2007-01-01

194

Preparation and histological evaluation of biomimetic three-dimensional hydroxyapatite\\/chitosan-gelatin network composite scaffolds  

Microsoft Academic Search

A novel biodegradable hydroxyapatite\\/chitosan-gelatin network (HA\\/CS-Gel) composite of similar composition to that of normal human bone was prepared as a three-dimensional biomimetic scaffold by phase separation method for bone tissue engineering. Changing the solid content and the compositional variables of the original mixtures allowed control of the porosities and densities of the scaffolds. The HA granules were dispersed uniformly in

Feng Zhao; Yuji Yin; William W. Lu; J. Chiyan Leong; Wenyi Zhang; Jingyu Zhang; Mingfang Zhang; Kangde Yao

2002-01-01

195

Stimulation of osteoblast responses to biomimetic nanocomposites of gelatin–hydroxyapatite for tissue engineering scaffolds  

Microsoft Academic Search

Collagen-derived gelatin\\/hydroxyapatite (HA) nanocomposites were biomimetically synthesized for hard tissue engineering scaffold. In vitro osteoblastic cellular responses to the nanocomposites were assessed in comparison with those conventionally mixed gelatin–HA composites. A three-dimensional culture method involving floating cells in a culture medium was introduced to assist in the initial attachment of the cells to the scaffolds, and the proliferation and differentiation

Hae-Won Kim; Hyoun-Ee Kim; Vehid Salih

2005-01-01

196

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

197

Fabrication of Hydroxyapatite\\/Ethylene-Vinyl Acetate\\/Polyamide 66 Composite Scaffolds by the Injection-Molding Method  

Microsoft Academic Search

This research investigated the injection-molding techniques to produce hydroxyapatite (HA)\\/ethylene-vinyl acetate (EVA)\\/polyamide 66 (PA66) composite scaffolds. The effects of HA, EVA, azodicarbonamide (AC) content and shot size on the mechanical properties, pore morphology, porosity and crystallization behavior of the composite scaffolds were analyzed by XRD, DSC, SEM and mechanical test. The compressive modulus and strength of the HA\\/EVA\\/PA66 scaffolds with

Song Zhou; Li Zhang; Yan-Ying Wang; Yi Zuo; Shi-Bo Gao; Yu-Bao Li

2011-01-01

198

Processing and Performance of Hydroxyapatite\\/Fluorapatite Double Layer Coating on Zirconia by the Powder Slurry Method  

Microsoft Academic Search

A hydroxyapatite\\/fluorapatite (HA\\/FA) double layer was coat- ed on ZrO2 by a powder slurry method. The FA layer between the HA layer and the ZrO2 substrate was effective in suppress- ing the reaction between HA and ZrO2. The rheological prop- erties of the slurry and the thermal treatment conditions were optimized. Addition of small amounts of tri-ethyl phosphate dis- persant

Hae-Won Kim; Byung-Ho Yoon; Young-Hag Koh; Hyoun-Ee Kim

2006-01-01

199

Effects of bioactive glass, hydroxyapatite and bioactive glass – Hydroxyapatite composite graft particles in the treatment of infrabony defects  

PubMed Central

Background: Several synthetic alloplastic materials have been used in the past as an implant in infrabony defects with a goal to reconstruct the lost part of attachment apparatus via new osseous tissue formation. The present study was undertaken to evaluate and compare clinico-radiographically, the effect of bioactive glass (BG), hydroxyapatite (HA), and BG-HA composite bone graft particles in the treatment of human infra-bony periodontal defects. Materials and Methods: Indigenous synthetic HA, BG, and BG-HA composite bone graft materials were developed in the laboratory. Twenty eight infrabony periodontal defects were equally distributed (i.e., seven defects) into four groups. The defects were treated separately with three types of graft materials and non-grafted manner (open flap debridement alone, control) to evaluate both the soft and hard tissue responses after six months of surgery. Evaluation was done by studying different parameters such as plaque index, gingival index, relative attachment level, probing pocket depth, and radiographic bone fill in Intra Oral Peri-Apical radiograph. Results: The healing of defects was uneventful and free of any biological complications. The gain in relative attachment level, reduction of probing pocket depth, and bone fill was statistically significant in all four groups. BG and BG-HA synthetic bone graft implanted sites showed significant bone fill (P<0.05) than hydroxyapatite and unimplanted control sites. Conclusion: The performance of BG and its composite was better compared to HA and open flap debridement alone for the reconstruction of infrabony defects. The BG-HA composite particles may effectively be used as an alternative bone graft material for infrabony defects. PMID:23055592

Mistry, Surajit; Kundu, Debabrata; Datta, Someswar; Basu, Debabrata

2012-01-01

200

Monolithic Pellets, Composites and Thick Films of Hydroxyapatite: Correlation of Mechanical Properties with Microstructure.  

NASA Astrophysics Data System (ADS)

Hydroxyapatite Ca_{10}(PO _4)_6(OH)_2 (abbreviated as HA) has great biocompatibility. Poor mechanical properties of HA implants and decomposition of HA during processing are the major obstacles for widespread uses of HA. In the present thesis we have attempted to understand the sintering behavior of monolithic HA and metal-reinforced HA-matrix composites, and the mechanism of formation of HA coating in the solutions at the normal temperature. The powders of two calcium phosphates, namely hydroxyapatite and dicalcium phosphate (DCP: chemical formula Ca_2P_2O_7), were sintered at various temperatures and in various environments. The density, flexural strength and knoop hardness of both phosphates sintered in air for 4 h initially increased with the sintering temperature, reaching maxima at around 1000-1150 ^circC, and then decreased due to decomposition. To reduce dehydroxylation, HA powder was sintered in moisture at various temperatures up to 1350^circ C and X-ray diffraction study did not indicate any decomposition at the highest sintering temperature. It is seen that dehydroxylation did not hinder sintering, but decomposition obstructed sintering of both HA and DCP. Ductile-phase reinforcement of hydroxyapatite was achieved by addition of silver particulates (5-30 vol.%) in HA powder compacts. A composite made by sintering 10 vol.% Ag and balance HA at 1200^circ C for 1 h in air had flexural strength of 75 +/- 7 MPa, which was almost double that of pure HA sintered under an identical condition. Silver in the composite melted during sintering, but due to poor wetting, did not spread in between HA particles. The increase in the flexural strength of the composites was thought to be due to crack-bridging and crack-arrest by silver inclusions. Thick films (several ?m) of hydroxyapatite were deposited on silicon single crystal placed in close proximity to a plate of apatite- and wollastonite -containing glass and dipped into a simulated body fluid (SBF) at 36^circC. Amorphous calcium phosphate phase present in the glass leached into the SBF, causing supersaturation of Ca^ {2+} and (PO_4)^ {3-} ions. HA films grown on Si(111) showed strong (102) texture. As a contrast hardly any HA film could be grown on Si(100) surface. Our results suggest that the driving force for formation of apatite films arises from lowering of free energy of the supersatured solution by deposition of ions in certain crystallographic arrangements on suitable substrates with low interface energies.

Wang, Pauchiu Either

201

Nano-hydroxyapatite and its applications in preventive, restorative and regenerative dentistry: a review of literature  

PubMed Central

Summary This study aims to critically summarize the literature about nano-hydroxyapatite. The purpose of this work is to analyze the benefits of using nano-hydroxyapatite in dentistry, especially for its preventive, restorative and regenerative applications. We also provide an overview of new dental materials, still experimental, which contain the nano-hydroxyapatite in its nano-crystalline form. Hydroxyapatite is one of the most studied biomaterials in the medical field for its proven biocompatibility and for being the main constituent of the mineral part of bone and teeth. In terms of restorative and preventive dentistry, nano-hydroxyapatite has significant remineralizing effects on initial enamel lesions, certainly superior to conventional fluoride, and good results on the sensitivity of the teeth. The nano-HA has also been used as an additive material, in order to improve already existing and widely used dental materials, in the restorative field (experimental addition to conventional glass ionomer cements, that has led to significant improvements in their mechanical properties). Because of its unique properties, such as the ability to chemically bond to bone, to not induce toxicity or inflammation and to stimulate bone growth through a direct action on osteoblasts, nano-HA has been widely used in periodontology and in oral and maxillofacial surgery. Its use in oral implantology, however, is a widely used practice established for years, as this substance has excellent osteoinductive capacity and improves bone-to-implant integration. PMID:25506416

Pepla, Erlind; Besharat, Lait Kostantinos; Palaia, Gaspare; Tenore, Gianluca; Migliau, Guido

2014-01-01

202

Polyvinyl pyridine microspheres  

NASA Technical Reports Server (NTRS)

Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

1979-01-01

203

Microsphere insulation systems  

NASA Technical Reports Server (NTRS)

A new insulation system is provided that contains microspheres. This insulation system can be used to provide insulated panels and clamshells, and to insulate annular spaces around objects used to transfer, store, or transport cryogens and other temperature-sensitive materials. This insulation system provides better performance with reduced maintenance than current insulation systems.

Allen, Mark S. (Inventor); Willen, Gary S. (Inventor); Mohling, Robert A. (Inventor)

2005-01-01

204

Polyvinyl pyridine microspheres  

NASA Technical Reports Server (NTRS)

Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

1980-01-01

205

Fusion microsphere targets  

SciTech Connect

It was shown that a microsphere within the structure limitations is hydrodynamically stable. To insure its perfect formation, the initial chemical compositions must have a blowing capability, more important, the resultant liquid compositions must also have sufficient surface tension and low viscosity.

Koo, J.C.

1980-07-28

206

Nonstationary nonlinear effects in optical microspheres  

E-print Network

Nonstationary nonlinear effects in optical microspheres Alexey E. Fomin and Michael L. Gorodetsky produce oscillatory instability in optical microspheres. We experimentally demon- strate this instability observed slow and irreversible thermo-optical processes in microspheres. © 2005 Op- tical Society

207

Heterogeneous synthesis of fluoridated hydroxyapatites.  

PubMed

Fluoridated hydroxyapatites were synthesized with two different modes of fluoride supply: by supplying F(-)-free solution initially, followed by a F(-)-containing solution whose fluoride concentration was stoichiometrically equal to that of fluorapatite; and with the order of supply of these solutions reversed. Both of these heterogeneously synthesized fluoridated hydroxyapatites showed typical calcium phosphate X-ray diffraction patterns; and both had similar total fluoride contents (0.94 +/- 0.02 and 0.99 +/- 0.03 mmol/g, respectively), i.e. half of the maximum fluoride content of fluorapatite. However, they differed considerably in their physico-chemical properties. The former had a wider peak breadth of X-ray diffraction and a lower apparent solubility (Ca = 12.2 +/- 0.7 mmol/l) than the latter (Ca = 19.8 +/- 0.4 mmol/l) at 37 degrees C and pH 4.0. Wavelength dispersive spectroscopy attached to scanning electron microscopy gave clearly different spectra. Electron spectroscopy for chemical analysis of apatite pellets made by pressing and heating showed a slightly larger F1s signal at the crystal surface of the former, although the difference was not marked. These results suggest that two different types of heterogeneous fluoridated hydroxyapatites were formed, hydroxyapatite covered with fluorapatite and fluorapatite covered with hydroxyapatite. PMID:1391396

Okazaki, M

1992-01-01

208

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

209

Osteogenic responses to zirconia with hydroxyapatite coating by aerosol deposition.  

PubMed

Previously, we found that osteogenic responses to zirconia co-doped with niobium oxide (Nb2O5) or tantalum oxide (Ta2O5) are comparable with responses to titanium, which is widely used as a dental implant material. The present study aimed to evaluate the in vitro osteogenic potential of hydroxyapatite (HA)-coated zirconia by an aerosol deposition method for improved osseointegration. Surface analysis by scanning electron microscopy and x-ray diffraction proved that a thin as-deposited HA film on zirconia showed a shallow, regular, crater-like surface. Deposition of dense and uniform HA films was measured by SEM, and the contact angle test demonstrated improved wettability of the HA-coated surface. Confocal laser scanning microscopy indicated that MC3T3-E1 pre-osteoblast attachment did not differ notably between the titanium and zirconia surfaces; however, cells on the HA-coated zirconia exhibited a lower proliferation than those on the uncoated zirconia late in the culture. Nevertheless, ALP, alizarin red S staining, and bone marker gene expression analysis indicated good osteogenic responses on HA-coated zirconia. Our results suggest that HA-coating by aerosol deposition improves the quality of surface modification and is favorable to osteogenesis. PMID:25586588

Cho, Y; Hong, J; Ryoo, H; Kim, D; Park, J; Han, J

2015-03-01

210

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

NASA Technical Reports Server (NTRS)

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 matrix. After the porogen is leached out, an open-cell composite foam remains which has a pore size and morphology defined by the porogen. By changing the weight fraction of the leachable component it was possible to produce composite foams with controlled porosities ranging from 0.47 +/- 0.02 to 0.85 +/- 0.01 (n = 3). Up to a polymer:fiber ratio of 7:6, short hydroxyapatite fibers served to reinforce low-porosity PLGA foams manufactured using gelatin microspheres as a porogen. Foams with a compressive yield strength up to 2.82 +/- 0.63 MPa (n = 3) and a porosity of 0.47 +/- 0.02 (n = 3) were manufactured using a polymer:fiber weight ratio of 7:6. In contrast, high-porosity composite foams (up to 0.81 +/- 0.02, n = 3) suitable for cell seeding were not reinforced by the introduction of increasing quantities of hydroxyapatite short fibers. We were therefore able to manufacture high-porosity foams which may be seeded with cells but which have minimal compressive yield strength, or low porosity foams with enhanced osteoconductivity and compressive yield strength.

Thomson, R. C.; Yaszemski, M. J.; Powers, J. M.; Mikos, A. G.; McIntire, L. V. (Principal Investigator)

1998-01-01

211

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

PubMed

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 matrix. After the porogen is leached out, an open-cell composite foam remains which has a pore size and morphology defined by the porogen. By changing the weight fraction of the leachable component it was possible to produce composite foams with controlled porosities ranging from 0.47 +/- 0.02 to 0.85 +/- 0.01 (n = 3). Up to a polymer:fiber ratio of 7:6, short hydroxyapatite fibers served to reinforce low-porosity PLGA foams manufactured using gelatin microspheres as a porogen. Foams with a compressive yield strength up to 2.82 +/- 0.63 MPa (n = 3) and a porosity of 0.47 +/- 0.02 (n = 3) were manufactured using a polymer:fiber weight ratio of 7:6. In contrast, high-porosity composite foams (up to 0.81 +/- 0.02, n = 3) suitable for cell seeding were not reinforced by the introduction of increasing quantities of hydroxyapatite short fibers. We were therefore able to manufacture high-porosity foams which may be seeded with cells but which have minimal compressive yield strength, or low porosity foams with enhanced osteoconductivity and compressive yield strength. PMID:9863527

Thomson, R C; Yaszemski, M J; Powers, J M; Mikos, A G

1998-11-01

212

Bone-like apatite layer formation on hydroxyapatite prepared by spark plasma sintering (SPS).  

PubMed

Hydroxyapatite (HA) compacts with high density and superior mechanical properties were fabricated by spark plasma sintering (SPS) using spray-dried HA powders as feedstock. The formation of bone-like apatite layer on SPS consolidated HA compacts were investigated by soaking the HA compacts in simulated body fluid (SBF) for various periods (maximum of 28 days). The structural changes in HA post-SBF were analyzed with scanning electron microscopy, grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. It was found that a layer consisting microcrystalline carbonate-containing hydroxyapatite was formed on the surface of HA compacts after soaking for 24h. The formation mechanism of apatite on the surface of HA compacts after soaking in SBF was attributed to the ion exchange between HA compacts and the SBF solution. The increase in ionic concentration of calcium and phosphorus as well as the increase in pH after SBF immersion resulted in an increase in ionic activity product of apatite in the solution, and provided a specific surface with a low interface energy that is conducive to the nucleation of apatite on the surface of HA compacts. PMID:15046903

Gu, Y W; Khor, K A; Cheang, P

2004-08-01

213

Production of hollow aerogel microspheres  

SciTech Connect

A process is described for preparing hollow aerogel microspheres, comprising the steps of: reacting metal alkoxide with water and base catalyst in alcohol solvent until a viscous alcogel is attained; forming a drop of viscous alcogel; injecting inert gas and base catalyst into the drop, at the time of drop formation, to form a hollow alcogel microsphere; blowing the hollow alcogel microsphere free of the viscous alcogel to fall into an atmosphere of inert gas and base catalyst; capturing said hollow alcogel microsphere on foam; and subjecting said hollow alcogel microsphere to supercritical drying to form a hollow aerogel microsphere of 800-1,200 [mu]m diameter with a wall thickness of 100-300 [mu]m and a wall density of 0.03 to 0. 3 g/cm[sup 3].

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

1993-07-13

214

Ion adsorption behaviour of hydroxyapatite with different crystallinities.  

PubMed

This study aimed to correlate crystallinity of hydroxyapatite (HA) with the ion adsorption behaviour of the material. Hydroxyapatite powders of various crystallinities (X(c)) and specific surface area (SSA) were prepared by precipitation following heat treatment. Adsorption experiments were carried out by using (i) multi-component ion solutions containing a broad range of light and heavy ions to study competitive adsorption and (ii) lead and zinc solutions with concentrations up to 250 ppm to determine the adsorption isotherms of the material. While as-prepared HA powders of low crystallinity (X(c)=0%) and a high SSA of 170 m(2)/g showed quantitative removal for divalent Pb, Zn, Be, U, Bi, V, Al, Cu and Ga ions, calcined powders with higher crystallinity (X(c)=65-95%) and lower SSA between 5 and 30 m(2)/g led to a quantitative removal only for a few elements (Pb, Bi, Ga). The time and concentration dependant ion removal capacity for Pb(2+) and Zn(2+) single element solutions showed quantitative removal even after short immersion times of less than 10 min for as-prepared HA powders. XRD analysis of the powders after ion adsorption revealed the presence of pyromorphite (Pb(5)(PO(4))(3)OH) and hopeite (Zn(3)(PO(4))(2)) phases, respectively. PMID:19640688

Stötzel, C; Müller, F A; Reinert, F; Niederdraenk, F; Barralet, J E; Gbureck, U

2009-11-01

215

Rabbit synoviocyte inositol phospholipid metabolism is stimulated by hydroxyapatite crystals  

SciTech Connect

Inhibition of prostaglandin E2 synthesis partially ameliorates some aspects of synovitis, but joint destruction still progresses. Other aspects of phospholipid metabolism may play a role in synovial tissue pathophysiology. Products of phosphatidylinositol metabolism can activate intracellular processes in response to extracellular stimuli. We asked whether this pathway is activated in synoviocytes in monolayer tissue culture by the addition of hydroxyapatite (HA) crystals in medium. These crystals are found in pathological human synovial fluid. These crystals are associated with the secretion of degradative enzymes and with a destructive arthritis in humans. Rabbit synoviocyte cultures, previously incubated with (3H)inositol to label inositol phospholipids, were stimulated with the addition of hydroxyapatite (180 micrograms/ml) to the cultures. There was enhanced intracellular accumulation of (3H)inositol monophosphate (30-100%) after 4 h. This indicated an increased phospholipase C activity. The radioactivity in (3H)inositol bis- and trisphosphates was too low to reliably measure. The use of (32P)Pi allowed detection of these compounds. In the presence of HA, incorporation of (32P)Pi into phosphatidylinositol, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate was increased. In addition, cultures exposed to (32P)Pi during stimulation with HA had an increased content of (32P)inositol monophosphate, bisphosphate, and trisphosphate.

Rothenberg, R.J.; Cheung, H.

1988-04-01

216

Hydroxyapatite electrodeposition on anodized titanium nanotubes for orthopedic applications  

NASA Astrophysics Data System (ADS)

Nanotubes modification for orthopedic implants has shown interesting biological performances (such as improving cell adhesion, cell differentiation, and enhancing osseointegration). The purpose of this study is to investigate effect of titanium dioxide (TiO2) nanotube feature on performance of hydroxyapatite-coated titanium (Ti) bone implants. TiO2 nanotubes were prepared by anodization using ammonium fluoride electrolyte (NH4F) with and without modifiers (PEG400 and Glycerol) at various potential forms, and times. After anodization, the nanotubes were subsequently annealed. TiO2 nanotubes were characterized by scanning electron microscope and X-ray diffractometer. The amorphous to anatase transformation due to annealing was observed. Smooth and highly organized TiO2 nanotubes were found when high viscous electrolyte, NH4F in glycerol, was used. Negative voltage (-4 V) during anodization was confirmed to increase nanotube thickness. Length of the TiO2 nanotubes was significantly increased by times. The TiO2 nanotube was electrodeposited with hydroxyapatite (HA) and its adhesion was estimated by adhesive tape test. The result showed that nanotubes with the tube length of 560 nm showed excellent adhesion. The coated HA were tested for biological test by live/dead cell straining. HA coated on TiO2 nanotubes showed higher cells density, higher live cells, and more spreading of MC3T3-E1 cells than that growing on titanium plate surface.

Parcharoen, Yardnapar; Kajitvichyanukul, Puangrat; Sirivisoot, Sirinrath; Termsuksawad, Preecha

2014-08-01

217

[The in vitro biological behavior of TiNb30 alloy treated with hydroxyapatite and tricalcium phosphates].  

PubMed

An in vitro study has been carried out in different cell systems to determine the biological response of TiNb30 alloy before and after a surface treatment with hydroxyapatite (HA) and tricalcium phosphate (TCP) by the sol-gel method. TiNb30 pure Ti induce favorable cell viability with respect to pure Ni showing a high cytotoxic effect. After surface treatment with HA or HA-TCP mixtures, no difference in cell proliferation can be observed between amorphous and cristalline forms. However, HA decreases (75 +/- 15%) and HA-TCP mixtures increase (133 +/- 11%) significantly cell proliferation compared with controls. PMID:9471695

Floquet, I; Ralison, A; Eisenbarth, E; Iost, A; Breme, J; Hildebrand, H F

1997-11-01

218

Microspheres and nanoparticles from ultrasound  

Microsoft Academic Search

Improved preparations of various examples of monodispersed, porous, hollow, and core-shell metal and semiconductor nanoparticles or nanowires have been developed. Now titania microspheres and nanoparticles and silica microspheres can be synthesized using an inexpensive high frequency (1.7 MHz) ultrasonic generator (household humidifier; ultrasonic spray pyrolysis; USP). Morphology and pore size of titania microspheres were controlled by the silica to Ti(IV)

Won Hyuk Suh

2006-01-01

219

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

220

Tensile properties, tension-tension fatigue and biological response of polyetheretherketone-hydroxyapatite composites for load-bearing orthopedic implants.  

PubMed

Polyetheretherketone-hydroxyapatite composites were developed as alternative materials for load-bearing orthopedic applications. The amount of hydroxyapatite (HA) incorporated into the polyetheretherketone (PEEK) polymer matrix ranges from 5 to 40 vol% and these materials were successfully fabricated by injection molding. This study presents the mechanical and biological behavior of the composite materials developed. It was found that the amount of HA in the composite influenced the tensile properties. Dynamic behavior under tension-tension fatigue revealed that the fatigue-life of PEEK-HA composites were dependent on the HA content as well as the applied load. The biological responses of PEEK-HA composites carried out in vivo verified the biocompatibility and bioactive nature of the composite materials. PMID:12699660

Abu Bakar, M S; Cheng, M H W; Tang, S M; Yu, S C; Liao, K; Tan, C T; Khor, K A; Cheang, P

2003-06-01

221

Thin-Layer Hydroxyapatite Deposition on a Nanofiber Surface Stimulates Mesenchymal Stem Cell Proliferation and Their Differentiation into Osteoblasts  

PubMed Central

Pulsed laser deposition was proved as a suitable method for hydroxyapatite (HA) coating of coaxial poly-?-caprolactone/polyvinylalcohol (PCL/PVA) nanofibers. The fibrous morphology of PCL/PVA nanofibers was preserved, if the nanofiber scaffold was coated with thin layers of HA (200?nm and 400?nm). Increasing thickness of HA, however, resulted in a gradual loss of fibrous character. In addition, biomechanical properties were improved after HA deposition on PCL/PVA nanofibers as the value of Young's moduli of elasticity significantly increased. Clearly, thin-layer hydroxyapatite deposition on a nanofiber surface stimulated mesenchymal stem cell viability and their differentiation into osteoblasts. The optimal depth of HA was 800?nm. PMID:22319242

Prosecká, Eva; Buzgo, Matej; Rampichová, Michala; Kocourek, Tomáš; Kochová, Petra; Vysloužilová, Lucie; Tvrdík, Daniel; Jelínek, Miroslav; Lukáš, David; Amler, Evžen

2012-01-01

222

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

223

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

224

Part I: crystalline fluorapatite-coated hydroxyapatite, physical properties.  

PubMed

Crystalline fluorapatite-coated hydroxyapatite (FA-HA) is studied using scanning electron microscopy (SEM), X-ray diffraction (XD), energy dispersive X-ray analysis (EDX), and EDX analysis mapping (EDXM). Fluoridated HA (fluorapatite) was prepared by reacting resorbable synthetic HA (OsteoGen, Impladent, Ltd, Holliswood, NY) with 4.3% sodium fluoride (NaF) for 2 minutes. After washing and drying, the resultant powder was subjected to physical property analysis using the methods listed above. SEM showed little evidence of surface change. Changes, if any, consisted of a slightly more distinct crystalline clarity on the surface of the FA sample. XD patterns showed significant random noise dispersion of the untreated HA sample compared with the lack of noise patterns in the treated FA sample. Characteristic monetite peaks were noted in analysis of the nontreated HA control sample, whereas there was no evidence of monetite in XD analysis of the treated FA material. It was determined that the fluoridation reaction, as described, served as a purification procedure of the initial HA reagent to eliminate a more soluble monetite contaminant. Also, the reaction of fluoride ion with surface HA (whether it be from or a combination of dissolution-reapposition or isomorphic substitution) produces a more purified, crystalline FA sample that was characterized by a more characteristic and sharp XD pattern. EDX analysis of the FA sample revealed a fluoride peak at 0.70 KeV that was not seen in the nonfluoridated control. EDX mapping showed an evenly distributed needle-like crystalline-shaped particulate pattern over the entire surface of the FA sample, which was lacking in the HA control. From a variety of analytic methods (as described), it was concluded that reaction of synthetic resorbable HA with 4.3% NaF solution at neutral pH produces FA-coated HA. PMID:20594065

Kimoto, Kazunari; Okudera, Toshimitsu; Okudera, Hajima; Nordquist, William D; Krutchkoff, David J

2011-01-01

225

Mechanism of Zn stabilization in hydroxyapatite and hydrated (0 0 1) surfaces of hydroxyapatite  

NASA Astrophysics Data System (ADS)

A basic understanding of Zn incorporation on bulk and hydrated (0 0 1) surfaces of hydroxyapatite (HA) is attained through electronic structure calculations which use a combined first principles density functional (DFT) and extended Hückel tight binding (EHTB) methodology. A Zn substituted hydroxyapatite relaxed structure is obtained through a periodic cell DFT geometry optimization method. Electronic structure properties are calculated by using both cluster DFT and periodic cell EHTB methods. Bond order calculations show that Zn preference for the Ca2 vacancy, near the OH channel and with greater structural flexibility, is associated with the formation of a four-fold (bulk) and nearly four-fold (surface) coordination, as in ZnO. When occupying the octahedral Ca1 vacancy, Zn remains six-fold in the bulk, but coordination decreases to five-fold in the surface. In the bulk and surface, Zn2 is found to be more covalent than Zn1, due to a decrease in bond lengths at the four-fold site, which approach the 1.99 Å ZnO value. Zn is however considerably less bound in the biomaterial than in the oxide, where calculated bond orders are twice as large as in HA. Surface phosphate groups (PO4) and hydroxide ions behave as compact individual units as in the bulk; no evidence is found for the presence of HPO4. Ca-O bond orders decrease at the surface, with a consequent increase in ionicity. Comparison between DFT and EHTB results show that the latter method gives a good qualitative account of charge and bonding in these systems.

Matos, M.; Terra, J.; Ellis, D. E.

2010-04-01

226

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

227

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

228

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

229

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

230

Synthesis of fluorapatite-hydroxyapatite nanoparticles and toxicity investigations.  

PubMed

In this study, calcium phosphate nanoparticles with two phases, fluorapatite (FA; Ca(10)(PO(4))(6)F(2)) and hydroxyapatite (HA; Ca(10)(PO(4))(6)(OH)(2)), were prepared using the solgel method. Ethyl phosphate, hydrated calcium nitrate, and ammonium fluoride were used, respectively, as P, Ca, and F precursors with a Ca:P ratio of 1:72. Powders obtained from the sol-gel process were studied after they were dried at 80°C and heat treated at 550°C. The degree of crystallinity, particle and crystallite size, powder morphology, chemical structure, and phase analysis were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Zetasizer experiments. The results of XRD analysis and FTIR showed the presence of hydroxyapatite and fluorapatite phases. The sizes of the crystallites estimated from XRD patterns using the Scherrer equation and the crystallinity of the hydroxyapatite phase were about 20 nm and 70%, respectively. Transmission electron microscope and SEM images and Zetasizer experiments showed an average size of 100 nm. The in vitro behavior of powder was investigated with mouse fibroblast cells. The results of these experiments indicated that the powders were biocompatible and would not cause toxic reactions. These compounds could be applied for hard-tissue engineering. PMID:21499417

Montazeri, N; Jahandideh, R; Biazar, Esmaeil

2011-01-01

231

Synthesis of fluorapatite–hydroxyapatite nanoparticles and toxicity investigations  

PubMed Central

In this study, calcium phosphate nanoparticles with two phases, fluorapatite (FA; Ca10(PO4)6F2) and hydroxyapatite (HA; Ca10(PO4)6(OH)2), were prepared using the solgel method. Ethyl phosphate, hydrated calcium nitrate, and ammonium fluoride were used, respectively, as P, Ca, and F precursors with a Ca:P ratio of 1:72. Powders obtained from the sol-gel process were studied after they were dried at 80°C and heat treated at 550°C. The degree of crystallinity, particle and crystallite size, powder morphology, chemical structure, and phase analysis were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Zetasizer experiments. The results of XRD analysis and FTIR showed the presence of hydroxyapatite and fluorapatite phases. The sizes of the crystallites estimated from XRD patterns using the Scherrer equation and the crystallinity of the hydroxyapatite phase were about 20 nm and 70%, respectively. Transmission electron microscope and SEM images and Zetasizer experiments showed an average size of 100 nm. The in vitro behavior of powder was investigated with mouse fibroblast cells. The results of these experiments indicated that the powders were biocompatibile and would not cause toxic reactions. These compounds could be applied for hard-tissue engineering. PMID:21499417

Montazeri, N; Jahandideh, R; Biazar, Esmaeil

2011-01-01

232

Functional magnetic microspheres  

NASA Technical Reports Server (NTRS)

Functional magnetic particles are formed by dissolving a mucopolysaccharide such as chitosan in acidified aqueous solution containing a mixture of ferrous chloride and ferric chloride. As the pH of the solution is raised magnetite is formed in situ in the solution by raising the pH. The dissolved chitosan is a polyelectrolyte and forms micelles surrounding the granules at pH of 8-9. The chitosan precipitates on the granules to form microspheres containing the magnetic granules. On addition of the microspheres to waste aqueous streams containing dissolved ions, the hydroxyl and amine functionality of the chitosan forms chelates binding heavy metal cations such as lead, copper, and mercury and the chelates in turn bind anions such as nitrate, fluoride, phosphate and borate.

Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Landel, Robert F. (Inventor)

1981-01-01

233

Hydroxyapatite coating modifies implant membrane formation. Controlled micromotion studied in dogs.  

PubMed

We studied the influence of controlled micromovements between bone and porous titanium alloy implants with and without hydroxyapatite coating. A dynamically loaded unstable device producing approximately 150-microns axial translation of knee implants during each gait cycle was developed. Stable implants served as controls. Matched stable and unstable implants with either porous titanium (Ti) or hydroxyapatite (HA) coating surrounded by a gap of 0.75 mm were inserted into the weight-bearing regions of the medial femoral condyles in 14 mature dogs. Histologic analysis after 4 weeks showed a fibrous membrane surrounding both types of implants subjected to micromovements, whereas various amounts of bone ingrowth was obtained in the stable implants. The membrane around unstable HA implants was thinner than that around unstable Ti implants. Islands of fibrocartilaginous tissue characterized the membrane around unstable HA implants, whereas fibrous connective tissue surrounded unstable Ti implants. The collagen concentration of the fibrous membranes was higher around unstable HA implants compared with Ti implants. Instability reduced the shear strength of the implants. However, the shear strength of unstable HA implants exceeded that of the Ti implants, both unstable and stable. The greatest shear strength was obtained by stable HA implants, i.e., tenfold greater than that of stable Ti implants. The gap-healing capacity around stable HA implants increased toward the HA surface, and was greater than that around Ti implants. Our study demonstrates that micromovements between bone and implant inhibit bone ingrowth and lead to the development of a fibrous membrane. The superior fixation of unstable HA implants compared with unstable Ti implants may be ascribed to the presence of fibrocartilage, a higher collagen concentration, and radiating orientation of collagen fibers in the membrane. The strongest mechanical anchorage and the greatest amount of bone ingrowth was obtained by stable implants coated with hydroxyapatite. PMID:1590045

Søballe, K; Brockstedt-Rasmussen, H; Hansen, E S; Bünger, C

1992-04-01

234

Self-assembly of nano-hydroxyapatite on multi-walled carbon nanotubes.  

PubMed

Inspired by self-assembly of nano-hydroxyapatite (nHA) on collagen associated with the 67nm periodic microstructure of collagen, we used multi-walled carbon nanotubes (MWCNTs) with approximately 40nm bamboo periodic microstructure as a template for nHA deposition to form a nHA-MWCNT composite. The assembled apatite was analyzed by transmission electron microscopy and scanning electron microscopy. Defects that were analogous to edge dislocations along the carbon nanotubes' multi-walled surfaces were the nucleation sites for nHA after these defects had been functionalized principally into carboxylic groups. Spindle-shaped units consisting of an assembly of near parallel, fibril-like nHA polycrystals were formed and oriented at a certain angle to the long axis of the carbon nanotubes, unlike nHA-collagen in which the nHA is oriented along the longitudinal axis of the collagen molecule. One possible explanation for this difference is that there are more bonds for calcium chelation (-COOH, >CO) on the collagen fibril surface than on the surface of MWCNTs. Spindle-shaped units that are detached from the MWCNT template are able to maintain the ordered parallel structure of the nHA polycrystal fibril. We have thus created a self-assembled hydroxyapatite on MWCNTs. PMID:17512807

Liao, Susan; Xu, Guofu; Wang, Wei; Watari, Fumio; Cui, Fuzhai; Ramakrishna, Seeram; Chan, Casey K

2007-09-01

235

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

236

Development of electrochemical folic acid sensor based on hydroxyapatite nanoparticles  

NASA Astrophysics Data System (ADS)

We report the synthesis of hydroxyapatite (HA) nanoparticles (NPs) by a simple microwave irradiation method and its application as sensing element for the precise determination of folic acid (FA) by electrochemical method. The structure and composition of the HA NPs characterized using XRD, FTIR, Raman and XPS. SEM and EDX studies confirmed the formation of elongated spherical shaped HA NPs with an average particle size of about 34 nm. The HA NPs thin film on glassy carbon electrode (GCE) were deposited by drop casting method. Electrocatalytic behavior of FA in the physiological pH 7.0 was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. The fabricated HA/GCE exhibited a linear calibration plot over a wide FA concentration ranging from 1.0 × 10-7 to 3.5 × 10-4 M with the detection limit of 75 nM. In addition, the HA NPs modified GCE showed good selectivity toward the determination of FA even in the presence of a 100-fold excess of ascorbic acid (AA) and 1000-fold excess of other common interferents. The fabricated biosensor exhibits good sensitivity and stability, and was successfully applied for the determination of FA in pharmaceutical samples.

Kanchana, P.; Sekar, C.

2015-02-01

237

Bacterial Cellulose-Hydroxyapatite Nanocomposites for Bone Regeneration  

PubMed Central

The aim of this study was to develop and to evaluate the biological properties of bacterial cellulose-hydroxyapatite (BC-HA) nanocomposite membranes for bone regeneration. Nanocomposites were prepared from bacterial cellulose membranes sequentially incubated in solutions of CaCl2 followed by Na2HPO4. BC-HA membranes were evaluated in noncritical bone defects in rat tibiae at 1, 4, and 16 weeks. Thermogravimetric analyses showed that the amount of the mineral phase was 40%–50% of the total weight. Spectroscopy, electronic microscopy/energy dispersive X-ray analyses, and X-ray diffraction showed formation of HA crystals on BC nanofibres. Low crystallinity HA crystals presented Ca/P a molar ratio of 1.5 (calcium-deficient HA), similar to physiological bone. Fourier transformed infrared spectroscopy analysis showed bands assigned to phosphate and carbonate ions. In vivo tests showed no inflammatory reaction after 1 week. After 4 weeks, defects were observed to be completely filled in by new bone tissue. The BC-HA membranes were effective for bone regeneration. PMID:21961004

Saska, S.; Barud, H. S.; Gaspar, A. M. M.; Marchetto, R.; Ribeiro, S. J. L.; Messaddeq, Y.

2011-01-01

238

Effect of modification of hydroxyapatite\\/collagen composites with sodium citrate, phosphoserine, phosphoserine\\/RGD-peptide and calcium carbonate on bone remodelling  

Microsoft Academic Search

This study describes the early interface reaction of cancellous bone to a nanocrystalline hydroxyapatite cement containing type I collagen (HA\\/ Coll) and its modifications with sodium citrate (CI), calcium carbonate (CA), phosphoserine (P) and phosphoserine plus RGD-peptide (RGD). Cylindrical implants of HA\\/Coll and its modifications were inserted into the tibia of Wistar rats. We analysed 6 specimens per group at

Wolfgang Schneiders; Antje Reinstorf; Wolfgang Pompe; Rene Grass; Achim Biewener; Michael Holch; Hans Zwipp; Stefan Rammelt

2007-01-01

239

Trading polymeric microspheres: Exchanging DNA molecules via microsphere interaction.  

PubMed

A new class of artificial molecular transport system is constructed by polymeric microspheres. The microspheres are prepared by self-assembly of poly(ethylene glycol)-block-poly(3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate), PEG-b-PDMAPS, by intermolecular dipole-dipole interaction of sulfobetaine side chains in water. Below the upper critical solution temperature (UCST) of PEG-b-PDMAPS, the microspheres (?1?m) interact with other microspheres by partial and transit fusion. In order to apply the interaction between microspheres, a 3'-TAMRA-labeled single-stranded DNA oligomer (ssDNA) is encapsulated into a PEG-b-PDMAPS microsphere by thermal treatment. The exchange of ssDNA between microspheres is confirmed by fluorescence resonance energy transfer (FRET) quenching derived from double-stranded formation with complementary 5'-BHQ-2-labeled ssDNA encapsulated in PEG-b-PDMAPS microspheres. The exchange rate of ssDNA is controllable by tuning the composition of the polymer. The contact-dependent transport of molecules can be applied in the areas of microreactors, sensor devices, etc. PMID:25731098

Morimoto, Nobuyuki; Muramatsu, Kanna; Nomura, Shin-Ichiro M; Suzuki, Makoto

2015-04-01

240

The influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites  

E-print Network

mechanical properties. Abbreviations: HA, Hydroxyapatite; MPTMS, Mercaptopropyl trimethoxy silane; APTMS, Aminopropyl trimethoxy silane; APTES, Aminopropyl triethoxy silane; PBS, Phosphate buffered saline; ICP-AES, Inductively coupled plasma... mode using a dual cantilever clamp. A multi frequency module was used at four different frequencies: 1, 10, 20 and 50 Hz. The tests were carried out between -10°C to 120°C, with a heating rate used of 3°C/min. Three repeats were carried out for each...

Naik, Ashutosh; Best, Serena M.; Cameron, Ruth E.

2014-12-18

241

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.

2015-01-01

242

Synthesis and photoluminescence study of flower-like hydroxyapatite nanostructure for bioprobe applications  

NASA Astrophysics Data System (ADS)

Biocompatible luminescent materials have received much attention for the development of novel bioprobes. In the present work, we have synthesized the flower-like hydroxyapatite (HA) nanostructure from eggshell biowaste via a simple and rapid microwave conversion process. The synthesized product is identified as Mg containing B-type carbonated HA. It showed an intense blue emission between 360 nm to 550 nm with maximum around 430 nm under UV light excitation (?ex= 344 nm). This blue emission might result from the carbonate related impurities present in the structure of HA and it can be a potential luminescent material for the development biocompatible probes.

Kumar, G. Suresh; Girija, E. K.; Thamizhavel, A.

2013-02-01

243

Regularities of Forming Calcium Phosphate Coatings on Zirconium from Electrolytes Based on Synthesized and Biological Hydroxyapatite  

NASA Astrophysics Data System (ADS)

Physical-chemical and mechanical properties of calcium phosphate coating formed by microarc oxidation method on the zirconium surface were investigated. Two types of electrolytes based on synthesized and biological hydroxyapatite (HA) were used to form the coatings. Deposition of the coating based on synthesized hydroxyapatite lead to an increase in functional properties of coatings (adhesion strength, Ca/P ratio) in comparison with the calcium phosphate coating deposited using biological hydroxyapatite. The x-ray phase analysis and TEM of coatings showed that the coatings have submicrocrystalline structure containing both stoichiometric and non-stoichiometric phases CaZr4(PO4)6, ?-Ca2P2O7, ?-CaP2O6, ZrP2O7, ZrO2, Zr3O1-x, and Zr.

Sharkeev, Yu. P.; Kulyashova, K. S.

2014-02-01

244

Low-Energy Plasma Spray (LEPS) Deposition of Hydroxyapatite/Poly-?-Caprolactone Biocomposite Coatings  

NASA Astrophysics Data System (ADS)

Thermal spraying is widely employed to deposit hydroxyapatite (HA) and HA-based biocomposites on hip and dental implants. For thick HA coatings (>150 ?m), problems are generally associated with the build-up of residual stresses and lack of control of coating crystallinity. HA/polymer composite coatings are especially interesting to improve the pure HA coatings' mechanical properties. For instance, the polymer may help in releasing the residual stresses in the thick HA coatings. In addition, the selection of a bioresorbable polymer may enhance the coatings' biological behavior. However, there are major challenges associated with spraying ceramic and polymeric materials together because of their very different thermal properties. In this study, pure HA and HA/poly-?-caprolactone (PCL) thick coatings were deposited without significant thermal degradation by low-energy plasma spraying (LEPS). PCL has never been processed by thermal spraying, and its processing is a major achievement of this study. The influence of selected process parameters on microstructure, composition, and mechanical properties of HA and HA/PCL coatings was studied using statistical design of experiments (DOE). The HA deposition rate was significantly increased by the addition of PCL. The average porosity of biocomposite coatings was slightly increased, while retaining or even improving in some cases their fracture toughness and microhardness. Surface roughness of biocomposites was enhanced compared with HA pure coatings. Cell culture experiments showed that murine osteoblast-like cells attach and proliferate well on HA/PCL biocomposite deposits.

Garcia-Alonso, Diana; Parco, Maria; Stokes, Joseph; Looney, Lisa

2012-01-01

245

Modulating protein adsorption onto hydroxyapatite particles using different amino acid treatments  

PubMed Central

Hydroxyapatite (HA) is a material of choice for bone grafts owing to its chemical and structural similarities to the mineral phase of hard tissues. The combination of osteogenic proteins with HA materials that carry and deliver the proteins to the bone-defective areas will accelerate bone regeneration. The study investigated the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins to the body. The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m2 g–1. Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby, compared with lysozyme, BSA demonstrated higher affinity towards positively charged Arg-HA. Alternatively, the binding affinity of lysozyme onto the negatively charged Asp-HA was higher when compared with BSA. The BSA and lysozyme adsorptions onto the amino acid-functionalized HA fitted better into the Freundlich than Langmuir model. The amino acid-functionalized HA particles that had higher protein adsorption demonstrated a lower protein-release rate. PMID:21957116

Lee, Wing-Hin; Loo, Ching-Yee; Van, Kim Linh; Zavgorodniy, Alexander V.; Rohanizadeh, Ramin

2012-01-01

246

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 Central

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; Šupová, Monika; Žaloudková, Margit; Balík, Karel; Lisá, V?ra; Šlouf, Miroslav; Ba?áková, Lucie

2014-01-01

247

Porous ZrO2 bone scaffold coated with hydroxyapatite with fluorapatite intermediate layer.  

PubMed

Highly porous zirconia (ZrO(2)) bone scaffolds, fabricated by a replication technique using polymeric sponge, were coated with hydroxyapatite (HA). To prevent the chemical reactions between ZrO(2) and HA, an intermediate fluorapatite (FA) layer was introduced. The strength of the porous ZrO(2) was higher than that of pure HA by a factor of 7, suggesting the feasibility of ZrO(2) porous scaffolds as load-bearing part applications. The coated HA/FA layer, with a thickness of about 30 microm, was firmly adhered to the ZrO(2) body with a bonding strength of 22MPa. The osteoblast-like cells were attached and spread well on the coating layer throughout the porous scaffolds. The alkaline phosphatase activity of the proliferated cells on the HA/FA coated ZrO(2) was comparable to that on pure HA and higher than that on pure ZrO(2). PMID:12763455

Kim, Hae-Won; Lee, Seung-Yong; Bae, Chang-Jun; Noh, Yoon-Jung; Kim, Hyoun-Ee; Kim, Hyun-Man; Ko, Jea Seung

2003-08-01

248

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

249

Advances in Microsphere Insulation Systems  

Microsoft Academic Search

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

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

2004-01-01

250

Phagocytosis of polymer microspheres by macrophages  

Microsoft Academic Search

This article reviews the phagocytosis of polymer microspheres by macrophages with respect to the size and the surface characteristics of the microspheres. Since few investigations have been carried out using well-characterized polymer microspheres, the authors have emphasized own experimental results. The findings provide useful information on the development of polymer microspheres as carriers for drug delivery systems.

Yasuhiko Tabata; Yoshito Ikada

251

Solar energy collector having hollow microspheres  

Microsoft Academic Search

Hollow glass microspheres made from a low heat conductivity glass composition containing a high vacuum and a thin metal coating deposited on the inner wall surface of the microspheres are described. The hollow glass microspheres are used to make superior insulation materials in the construction of highly efficient solar energy collectors. The hollow glass microspheres can also be made to

Torobin

1981-01-01

252

Synthesis, characterization and cell behavior of fluoridated hydroxyapatite  

NASA Astrophysics Data System (ADS)

Fluorine-containing hydroxyapatite (Ca5(PO4) 3(OH)1-xFx FHA), where F- partially replaces OH- in hydroxyapatite (HA), is recognized as a possible biomaterial for bone and tooth implants and gaining attention in the last several years as a possible alternative to HA. In this study, FHA powders were synthesized through a pH-cycling method. It was discovered that fluorine incorporation increased with the fluorine content in the initial solution and the number of pH cycles employed. A relatively low fluorine incorporation efficiency, ˜60%, was attained for most of the FHA samples. The short time of stay at each pH cycle and the limited number of cycles used are believed to be the main reasons of the low fluorine incorporation into the apatite structure. It was also revealed that the FHA particles produced by the pH-cycling method were inhomogeneous. They were a mixture of hydroxyapatite and F-rich apatite (or FA) particles. The mechanisms of incorporation of fluorine ions into hydroxyapatite by a pH cyclicing method were studied using TEM, XRD and fluorine measurement. Instead of forming laminated structures as reported by other research groups, a mixture of nano-sized F-rich apatite (FHA) and hydroxyapatite (HA) particles were obtained using the pH-cyclicing method. After calcination, these FHA particles were homogenized and became single phased FHA. The effect of fluorine content, preparing method, and sintering temperature on both the bulk density and biaxial flexural strength of sintered FHA was studied. Both uniaxially pressed un-milled (UPU) and cold isostatically pressed milled (IPM) FHA discs were sintered at temperatures between 1200˜400°C at an interval of 100°C. It was found that the fluorine content had a significant impact on the sintering behavior, densification, and mechanical properties of FHA discs. A close correlation between the sintered density and biaxial flexural strength of the specimens was revealed, where the biaxial flexural strength increased exponentially with the sintered density. FHA discs with various fluorine contents have been used to investigate the effect of fluorine content on osteoblastic cell behaviors. Rat osteosarcoma (ROS 17/28) cells were cultured on FHA discs for appropriate times. The osteoblastic cell behaviors were examined in terms of cell attachment, proliferation, morphology and differentiation. The fluorine content in FHA strongly affected the cell activities. More cell attachment and proliferation were observed on the fluorine-containing FHA than pure HA. Fluorine content also affected the differentiation behaviors of osteoblastic cells. Cells on fluorine-containing FHA had higher alkaline phosphatase (ALP) activity than pure HA in 2 weeks. The morphology of the cells showed that it took less time for cells to cover the surface of fluorine-containing samples than that of pure HA. These results suggested that fluorine ions had a significant impact on osteoblastic cell behaviors.

Qu, Haibo

253

Metal containing polymeric functional microspheres  

NASA Technical Reports Server (NTRS)

Polymeric functional microspheres containing metal or metal compounds are formed by addition polymerization of a covalently bondable olefinic monomer such as hydroxyethylmethacrylate in the presence of finely divided metal or metal oxide particles, such as iron, gold, platinum or magnetite, which are embedded in the resulting microspheres. The microspheres can be covalently bonded to chemotherapeutic agents, antibodies, or other proteins providing a means for labeling or separating labeled cells. Labeled cells or microspheres can be concentrated at a specific body location such as in the vicinity of a malignant tumor by applying a magnetic field to the location and then introducing the magnetically attractable microspheres or cells into the circulatory system of the subject. Labeled cells can be separated from a cell mixture by applying a predetermined magnetic field to a tube in which the mixture is flowing. After collection of the labeled cells, the magnetic field is discontinued and the labeled sub-cell population recovered.

Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

1979-01-01

254

Soil and Water Lab, DNA Microsphere Procedure Page 1 Protocol for Making DNA Microspheres Large Batch  

E-print Network

Soil and Water Lab, DNA Microsphere Procedure Page 1 Protocol for Making DNA Microspheres ­ Large Batch Last Updated 24 June 2014 Goal: Incorporate DNA into PLA microspheres. DNA serves as identification of specific tracer

Walter, M.Todd

255

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

256

[Preparation and biological safety evaluation of porous n-HA/PA66 composite].  

PubMed

Porous nano-hydroxyapatite/polyamide 66 (n-HA/PA66) composite was developed by injection molding method. Uniformly distributed and interconnected pores with an average size of about 500 microm in matrix were obtained. The evaluation of biological safety of the porous composite including cell cytoxicity test, sensitivity test, pyrogen test, haemolysis test was carried out according to GB/T16886 and GB/T16175. The results showed that the porous n-HA/PA66 composite was of no cytotoxicity, no allergen and pyrogen reactions as well as no hemolytic effect. PMID:19024460

Li, Hong; Li, Yubao; Yan, Yonggang; Zhou, Gang; Wang, Mingbo; Cheng, Lin

2008-10-01

257

Sol-gel preparation and in vitro test of fluorapatite/hydroxyapatite films.  

PubMed

Fluorapatite/hydroxyapatite (FA/HA) films have been demonstrated to be a good alternative to pure hydroxyapatite (HA) ones in medical applications because of their bioactivity and relatively low solubility. In this study, Ca(NO(3))(2), P(2)O(5), and HPF(6) were used to prepare FA/HA films on Ti6Al4V substrate with the use of a sol-gel method. The F contents in the films could be tailored by adjusting the amount of HPF(6) added. The in vitro evaluation of the films was carried out in both SBF9# solution and TRIS buffer solution. The films with appropriate F contents showed a better ability to induce calcium phosphate deposition on their surfaces than either pure HA film and FA/HA films with even higher F content, as well as smaller dissolution amounts than HA film in TRIS buffer solution. Hence, the FA/HA films obtained in this work integrate both good bioactivity and stability, and could be a better choice for bioactive film on titanium alloys to produce high-quality implants. PMID:15015207

Cheng, Kui; Weng, Wenjian; Qu, Haibo; Du, Piyi; Shen, Ge; Han, Gaorong; Yang, Juan; Ferreira, J M F

2004-04-15

258

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

259

Synthesis and characterization of hydroxyapatite nanofiber by chemical precipitation method using surfactants  

SciTech Connect

Highlights: ? We succeeded in synthesizing hydroxyapatite nano fibers by a chemical method. ? The reaction temperature is only 90 °C. ? The synthetic hydroxyapatite nano fiber is single crystal. - Abstract: We report a novel chemical precipitation route for the synthesis of hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, HA) fibers using surfactants as templates. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) reveal the characteristic peaks of HA. Transmission electron microscope (TEM) and high-resolution TEM revealed the nano structure, crystallinity and morphology of the HA fibers. The morphology of the HA fibers after calcinations were characterized by scanning electron microscope (SEM). Br{sup ?} ions were quickly replaced by the excess PO{sub 4}{sup 3?} ions in the solution after the addition of cetyltrime-thylammonium bromide (CTAB). Meanwhile, CTAB formed a rod-like micelles. Precursors reacted with PO{sub 4}{sup 3?} at the surface of CTAB micelles and finally formed the nanofiber structure.

Gao, Shan, E-mail: coralgao@hotmail.com [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Sun, Kangning, E-mail: sunkangning@sdu.edu.cn [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Li, Aimin; Wang, Hongyou [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China)

2013-03-15

260

Keratin-hydroxyapatite composites: biocompatibility, osseointegration, and physical properties in an ovine model.  

PubMed

Reconstituted keratin has shown promise as an orthopaedic biomaterial. This in vivo study investigates the biological response of composite materials prepared from reconstituted keratin containing a high content of hydroxyapatite (HA) (40 wt % HA), implanted for up to 18 weeks in the long bones of sheep. Keratin-HA composites were compared with a commercially available polylactic acid (PLA) HA composite (BIO RCI HA®, Smith and Nephew). Porous keratin-HA materials displayed excellent biocompatibility and osseointegration, with full integration into bone by 12 weeks. Dense keratin-HA materials also showed excellent biocompatibility, with a more limited osseointegration, involving the penetration of new bone into the periphery of the implant after eight weeks. In contrast, the PLA-HA implant did not integrate with surrounding tissue. Microindentation showed that porous keratin-HA implants were initially soft, but became stiffer as new bone penetrated the implant from four weeks onwards. In contrast, although the initial rigidity of dense keratin-HA composites was maintained for at least two weeks, the implant material weakened after four weeks. The PLA-HA implant maintained its physical properties throughout the course of the trial. This study demonstrates the increased osseointegration/osteoconduction capacity of keratin-HA composites and provides further evidence supporting the suitability of keratin-based materials, such as bone graft substitutes and soft tissue fixation devices. PMID:20878901

Dias, George J; Mahoney, Patricia; Swain, Michael; Kelly, Robert J; Smith, Robert A; Ali, Mohammad A

2010-12-15

261

A new hydroxyapatite-based biocomposite for bone replacement.  

PubMed

Since the 1970s, various types of ceramic, glass and glass-ceramic materials have been proposed and used to replace damaged bone in many clinical applications. Among them, hydroxyapatite (HA) has been successfully employed thanks to its excellent biocompatibility. On the other hand, the bioactivity of HA and its reactivity with bone can be improved through the addition of proper amounts of bioactive glasses, thus obtaining HA-based composites. Unfortunately, high temperature treatments (1200°C÷1300°C) are usually required in order to sinter these systems, causing the bioactive glass to crystallize into a glass-ceramic and hence inhibiting the bioactivity of the resulting composite. In the present study novel HA-based composites are realized and discussed. The samples can be sintered at a relatively low temperature (800 °C), thanks to the employment of a new glass (BG_Ca) with a reduced tendency to crystallize compared to the widely used 45S5 Bioglass®. The rich glassy phase, which can be preserved during the thermal treatment, has excellent effects in terms of in vitro bioactivity; moreover, compared to composites based on 45S5 Bioglass® having the same HA/glass proportions, the samples based on BG_Ca displayed an earlier response in terms of cell proliferation. PMID:23827547

Bellucci, Devis; Sola, Antonella; Gazzarri, Matteo; Chiellini, Federica; Cannillo, Valeria

2013-04-01

262

High temperature decomposition of synthetic hydroxyapatite in vacuum  

NASA Astrophysics Data System (ADS)

Starting hydroxyapatite (HA) powders were prepared by chemical synthesis at 40 °C using analytical-grade reagents: Ca(OH)2 and H3PO4. The process of thermal decomposition of HA powders was followed by thermo-XRD in vacuum 10-4 torr. The results show that synthetic HA with a CaP ratio=1.67 is stable below 1100 °C. Beyond 1100 °C HA gradually is transformed into Oxiapatite. In the region of 1400 °C a thermal structural configuration Monoclinic-P was detected with the following parameters: d=3.095x, 2.9593, 2.8602, 3.9521, 2.7161, 2.6121, 2.8541, etc. During the cooling process in normal atmosphere, this configuration is transformed into Ca2P2O7, Ca3(PO4)2 and Ca4P2O9. It can be considered as an important element for the interpretation of HA decomposition mechanism.

Prieto Valdés, J. J.; Gomez, G.; Pacheco, G.; Montoya, J. A.

1996-07-01

263

Mechanisms of uranium interactions with hydroxyapatite: Implications for groundwater remediation  

USGS Publications Warehouse

The speciation of U(VI) sorbed to synthetic hydroxyapatite was investigated using a combination of U LIII-edge XAS, synchrotron XRD, batch uptake measurements, and SEM-EDS. The mechanisms of U(VI) removal by apatite were determined in order to evaluate the feasibility of apatitebased in-situ permeable reactive barriers (PRBs). In batch U(VI) uptake experiments with synthetic hydroxyapatite (HA), near complete removal of dissolved uranium (>99.5%) to <0.05 ??M was observed over a range of total U(VI) concentrations up to equimolar of the total P in the suspension. XRD and XAS analyses of U(VI)-reacted HA at sorbed concentrations ???4700 ppm U(VI) suggested that uranium(VI) phosphate, hydroxide, and carbonate solids were not present at these concentrations. Fits to EXAFS spectra indicate the presence of Ca neighbors at 3.81 A??. U-Ca separation, suggesting that U(VI) adsorbs to the HA surfaces as an inner-sphere complex. Uranium(VI) phosphate solid phases were not detected in HA with 4700 ppm sorbed U(VI) by backscatter SEM or EDS, in agreement with the surface complexation process. In contrast, U(VI) speciation in samples that exceeded 7000 ppm sorbed U(VI) included a crystalline uranium(VI) phosphate solid phase, identified as chernikovite by XRD. At these higher concentrations, a secondary, uranium(VI) phosphate solid was detected by SEM-EDS, consistent with chernikovite precipitation. Autunite formation occurred at total U:P molar ratios ???0.2. Our findings provide a basis for evaluating U(VI) sorption mechanisms by commercially available natural apatites for use in development of PRBs for groundwater U(VI) remediation.

Fuller, C.C.; Bargar, J.R.; Davis, J.A.; Piana, M.J.

2002-01-01

264

Chalcogenide glass microsphere laser.  

PubMed

Laser action has been demonstrated in chalcogenide glass microsphere. A sub millimeter neodymium-doped gallium lanthanum sulphide glass sphere was pumped at 808 nm with a laser diode and single and multimode laser action demonstrated at wavelengths between 1075 and 1086 nm. The gallium lanthanum sulphide family of glass offer higher thermal stability compared to other chalcogenide glasses, and this, along with an optimized Q-factor for the microcavity allowed laser action to be achieved. When varying the pump power, changes in the output spectrum suggest nonlinear and/or thermal effects have a strong effect on laser action. PMID:21165022

Elliott, Gregor R; Murugan, G Senthil; Wilkinson, James S; Zervas, Michalis N; Hewak, Daniel W

2010-12-01

265

Degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid nanocomposite in simulated body fluid  

SciTech Connect

Graphical abstract: In this manuscript, we initiated a systematic study to investigate the effect of HA on thermal properties, inner structure, reduction of mechanical strength, surface morphology and the surface deposit of n-HA/PLGA composite with respect to the soaking time. The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation of n-HA/PLGA composite and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials, and the results would be of reference significance to predict the in vivo degradation and biological properties. - Highlights: • Effect of n-HA on degradation behavior of n-HA/PLGA composite was investigated. • Degradation behaviors of n-HA/PLGA and PLGA were carried out in SBF for 6 months. • Viscosity, thermal properties, inner structure and bending strength were tested. • n-HA can accelerate the degradation and endows it with bioactivity. - Abstract: To investigate the effect of hydroxyapatite(HA) on the degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid (HA/PLGA) nanocomposite, the degradation experiment of n-HA/PLGA composite and pure PLGA were carried out by soaking in simulated body fluid(SBF) at 37 °C for 1, 2, 4 and 6 months. The change of intrinsic viscosity, thermal properties, inner structure, bending strength reduction, surface morphology and the surface deposit of n-HA/PLGA composite and pure PLGA with respect to the soaking time were investigated by means of UbbeloHde Viscometer, differential scanning calorimeter (DSC), scanning electron microscope(SEM), electromechanical universal tester, a conventional camera and X-ray diffraction (XRD). The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation PLGA and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials.

Liuyun, Jiang, E-mail: jlytxg@163.com [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041 (China); Chengdong, Xiong [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041 (China); Lixin, Jiang; Lijuan, Xu [Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041 (China); Graduated School of Chinese Academy of Sciences, Beijing 100039 (China)

2013-10-15

266

Preparation and biological properties of a novel composite scaffold of nano-hydroxyapatite\\/chitosan\\/carboxymethyl cellulose for bone tissue engineering  

Microsoft Academic Search

In this study, we report the physico-chemical and biological properties of a novel biodegradable composite scaffold made of nano-hydroxyapatite and natural derived polymers of chitosan and carboxymethyl cellulose, namely, n-HA\\/CS\\/CMC, which was prepared by freeze-drying method. The physico-chemical properties of n-HA\\/CS\\/CMC scaffold were tested by infrared absorption spectra (IR), transmission electron microscope(TEM), scanning electron microscope(SEM), universal material testing machine and

Jiang Liuyun; Li Yubao; Xiong Chengdong

2009-01-01

267

Clinical effects of nanocrystalline hydroxyapatite paste in the treatment of intrabony periodontal defects: a randomized controlled clinical study  

Microsoft Academic Search

The purpose of the present randomized controlled clinical study was to compare the clinical outcomes of papilla preservation\\u000a flap surgery with or without the application of a novel nanocrystalline hydroxyapatite (nano-HA) bone graft substitute. Fourteen\\u000a patients with paired intrabony periodontal defects of ?4 mm participated in this split-mouth design study. The defects in\\u000a each subject were randomly selected to receive nano-HA

Bernd Heinz; Adrian Kasaj; Marie Teich; Søren Jepsen

2010-01-01

268

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

269

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

270

Preparation and Properties of Biodegradable Composites Derived from Poly(lactide-co-glycolide), Poly (L-lactide) and Nano-hydroxyapatite  

Microsoft Academic Search

Poly (L-lactide-co-glycolide) (PLGA), poly (L-lactide) (PLLA), and nano-hydroxyapatite (HA) were used to prepare a biodegradable bone fixation composite PLGA\\/PLLA\\/HA via blending and melt-molding methods. The ratio of PLGA, PLLA and HA was set to 75.0, 20.0 and 5.0 wt.%, respectively, and the neat PLGA and PLGA \\/PLLA blend were used as controls. Thermal properties were analyzed using thermogravimetric analysis (TGA).

Xia Chen; Liwen Zhang; Xiao Liu; Yanjun Cui; Guanghui Zhao; Yanfeng Li

2012-01-01

271

Characterization of multiwalled carbon nanotube-reinforced hydroxyapatite composites consolidated by spark plasma sintering.  

PubMed

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

272

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

273

Carboxymethyl cellulose-hydroxyapatite hybrid hydrogel as a composite material for bone tissue engineering applications.  

PubMed

Natural bone is a complex inorganic-organic nanocomposite material, in which hydroxyapatite (HA) nanocrystals and collagen fibrils are well organized into hierarchical architecture over several length scales. In this work, we reported a new hybrid material (CMC-HA) containing HA drown in a carboxymethylcellulose (CMC)-based hydrogel. The strategy for inserting HA nanocrystals within the hydrogel matrix consists of making the freeze-dried hydrogel to swell in a solution containing HA microcrystals. The composite CMC-HA hydrogel has been characterized from a physicochemical and morphological point of view by means of FTIR spectroscopy, rheological measurements, and field emission scanning electron microscopy (FESEM). No release of HA was measured in water or NaCl solution. The distribution of HA crystal on the surface and inside the hydrogel was determined by time of flight secondary ion mass spectrometry (ToF-SIMS) and FESEM. The biological performance of CMC-HA hydrogel were tested by using osteoblast MG63 line and compared with a CMC-based hydrogel without HA. The evaluation of osteoblast markers and gene expression showed that the addition of HA to CMC hydrogel enhanced cell proliferation and metabolic activity and promoted the production of mineralized extracellular matrix. PMID:23720392

Pasqui, Daniela; Torricelli, Paola; De Cagna, Milena; Fini, Milena; Barbucci, Rolando

2014-05-01

274

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

275

A new approach to enhancement of bone formation by electrically polarized hydroxyapatite.  

PubMed

An electrical field may affect osteogenesis. Since we found that hydroxyapatite (HA) ceramics may be polarizable, we hypothesized that electrically polarized HA may foster production of new bone in vivo. Both polarized and non-polarized HA ceramics were inserted into the subperiosteum spaces at the parietal bone area of rats. After 2, 4, and 8 weeks, the implant sites were examined histologically. Morphometric analysis revealed that new bone formation was accelerated on the negatively charged surface of the polarized HA (N-surface) at 2 weeks. The newly formed bone approached maturation at 4 weeks and was thicker on the N-surface than in the controls. By 8 weeks, newly formed bone in the controls was almost the same as that on the N-surface. These findings suggest that polarized HA is biocompatible and that bone formation on the N-surface is enhanced in the early stage of bone healing. PMID:11706953

Teng, N C; Nakamura, S; Takagi, Y; Yamashita, Y; Ohgaki, M; Yamashita, K

2001-10-01

276

Processing and in vitro behavior of hydroxyapatite coatings prepared by electrostatic spray assisted vapor deposition method.  

PubMed

Hydroxyapatite (HA) bioactive coatings are often used to improve bone attachment and reduce corrosion of metal prosthesis implants. This paper reports the preparation of HA coatings onto titanium substrates using a novel electrostatic spray assisted vapor deposition (ESAVD)-based method. The deposited coatings are characterized using a combination of Fourier transform infrared spectrometer, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and scratch test. The results confirm that well-crystallized HA coatings can be produced directly via the single-step ESAVD process, without further heat-treatment. The in vitro behavior of the as-deposited HA coating in simulated body fluid (SBF) is also presented. After 14-day immersion in SBF, the adhesion of the HA coating to the substrate increases significantly. PMID:17530629

Hou, Xianghui; Choy, Kwang-Leong; Leach, Sian Ellen

2007-12-01

277

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

278

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings  

PubMed Central

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.

Demnati, Imane; Grossin, David; Marsan, Olivier; Bertrand, Ghislaine; Collonges, Gérard; Combes, Christèle; Parco, Maria; Braceras, Inigo; Alexis, Joel; Balcaen, Yannick; Rey, Christian

2015-01-01

279

The Enamel Protein Amelotin is a Promoter of Hydroxyapatite Mineralization.  

PubMed

Amelotin (AMTN) is a recently discovered protein that is specifically expressed during the maturation stage of dental enamel formation. It is localized at the interface between the enamel surface and the apical surface of ameloblasts. AMTN knock-out mice have hypomineralized enamel whereas transgenic mice overexpressing AMTN have a compact but disorganized enamel hydroxyapatite (HA) microstructure indicating a possible involvement of AMTN in regulating HA mineralization directly. In this study we demonstrated that recombinant human (rh) AMTN dissolved in a metastable buffer system, based on light scattering measurements, promotes HA precipitation. The mineral precipitates were characterized by scanning and transmission electron microscopy and electron diffraction. Colloidal gold immunolabeling of AMTN in the mineral deposits showed that protein molecules were associated with HA crystals. The binding affinity of rh-AMTN to HA was found to be comparable to that of amelogenin, the major protein of the forming enamel matrix. Overexpression of AMTN in mouse calvaria cells also increased the formation of calcium deposits in the culture medium. Overexpression of AMTN during the secretory stage of enamel formation in vivo resulted in rapid and uncontrolled enamel mineralization. Site-specific mutagenesis of the potential serine phosphorylation motif SSEEL reduced the in vitro mineral precipitation to less than 25%, revealing that this motif is important for the HA mineralizing function of the protein. A synthetic short peptide containing the SSEEL motif was only able to facilitate mineralization in its phosphorylated form ((P) S(P) SEEL), indicating that this motif is necessary, but not sufficient for the mineralizing properties of AMTN. These findings demonstrate that AMTN has a direct influence on biomineralization by promoting HA mineralization and suggest a critical role for AMTN in the formation of the compact aprismatic enamel surface layer during the maturation stage of amelogenesis. This article is protected by copyright. All rights reserved. PMID:25407797

Abbarin, Nastaran; Miguel, Symone San; Holcroft, James; Iwasaki, Kengo; Ganss, Bernhard

2014-11-18

280

Electrochemical synthesis of nanosized hydroxyapatite by pulsed direct current method  

SciTech Connect

Synthesis of nanosized of hydroxyapatite (HA) by electrochemical pulsed direct current (PDC) method has been studied. The aim of this work is to study the influence of various PDC parameters (pH initial, electrode distance, duty cycle, frequency, and amplitude) on particle surface area of HA powders. The electrochemical synthesis was prepared in solution Ca{sup 2+}/EDTA{sup 4?}/PO{sub 4}{sup 3+} at concentration 0.25/0.25/0.15 M for 24 h. The electrochemical cell was consisted of two carbon rectangular electrodes connected to a function generator to produce PDC. There were two treatments for particles after electrosynthesized, namely without aging and aged for 2 days at 40 °C. For both cases, the particles were filtered and washed by demineralized water to eliminate the impurities and unreacted reactants. Then, the particles were dried at 100 °C for 2 days. The dried particles were characterized by X-ray diffraction, surface area analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectra and thermogravimetric and differential thermal analysis. HA particles can be produced when the initial pH > 6. The aging process has significant effect on the produced HA particles. SEM images of HA particles showed that the powders consisted of agglomerates composed of fine crystallites and have morphology plate-like and sphere. The surface area of HA particles is in the range of 25 – 91 m{sup 2}/g. The largest particle surface area of HA was produced at 4 cm electrode distance, 80% cycle duty, frequency 0.1 Hz, amplitude 9 V and with aging process.

Nur, Adrian; Rahmawati, Alifah; Ilmi, Noor Izzati; Affandi, Samsudin; Widjaja, Arief [Departement of Chemical Engineering, Faculty of Industrial Technology, Sepuluh Nopember Institute of Technology, Kampus ITS Sukolilo, Surabaya 60111 (Indonesia)

2014-02-24

281

The deposition of strontium-substituted hydroxyapatite coatings.  

PubMed

Strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as strontium (Sr) has been shown to have the dual benefit of promoting bone formation and reducing bone resorption, in vivo. In this work, SrHA coatings were deposited onto polycrystalline titanium surfaces using radio frequency (RF) magnetron co-sputtering and compared to those deposited from HA alone. In particular, the influence of different levels of Sr-substitution of the sputtering targets (5 and 13 % Sr-substituted HA targets) on the properties of the deposited coatings produced at a low discharge power level (150 W) were investigated using FTIR, XPS, XRD, ToFSIMS and AFM techniques (both before and after annealing at 500 °C). The results show that Sr could be successfully incorporated into the HA lattice to form SrHA coatings and that they contained no other impurities. However, the coating produced from the 13 % Sr-substituted target had a higher Ca + Sr/P ratio (1.95 ± 0.14) and Sr content when compared to the coating produced from the 5 % Sr-substituted target (1.58 ± 0.20). The deposition rate also decreased with increasing Sr content of the sputtering targets. Furthermore, as the Sr content of the coatings increased, so did the preferred 002 orientation of the coating along with increased surface roughness and heterogeneity of the surface features. Therefore, this study has shown that RF magnetron sputtering offers a means to control attendant properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface topography. PMID:25631262

Boyd, Adrian R; Rutledge, L; Randolph, L D; Mutreja, I; Meenan, B J

2015-02-01

282

Hydroxyapatite-glass composite as a bone substitute in large metaphyseal cavities in rabbits  

Microsoft Academic Search

This study evaluated hydroxyapatite-glass (HA-G) composite as a filler material when implanted into a proximal metaphyseal tibial cavity consisting of medullary tissue and cancellous bone in rabbits. The repair process was compared with that of autogenous bone grafts and untreated controls. Scanning electron microscopy, energy dispersive x-ray studies, radiography, histology with tetracycline fluorescence and morphometric bone measurements were used for

E. A. Suominen; A. J. Aho; J. Juhanoja; A. Yli-Urpo

1995-01-01

283

CCMR: Characterization of Microsphere Lasers  

NSDL National Science Digital Library

Silica microspheres use total internal reflection to stimulate emission and so there is very little loss and an ultrahigh Q. Because of their size (5-10 ?m in radius, their mode volume is incredibly small, and can thus achieve great optical circulating powers. This combination of high Q and small mode volume is condcive to creating microlasers with ultralow threshold power. Unfortunately, these same characteristics make coupling light incredibly difficult. The modes are quite thin, and with a standard laser’s optical frequency at 1015 and a 109 precision, stabilizing the laser’s frequency to be within the microsphere’s mode is tricky. Furthermore, the microspheres are susceptible to noise and thermal fluctuations Our goal is to build an electronic circuit to stabilize the pump laser’s frequency within such a small range.

Tsai, Tracy

2005-08-17

284

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.

285

Development of porous polyurethane/strontium-substituted hydroxyapatite composites for bone regeneration.  

PubMed

Polyurethane (PU) has been widely used for the biomedical applications but its potential for bone regeneration is limited due to its lack of osteoconductive properties. Strontium substituted hydroxyapatite (SrHA) particles, on the other hand, are known to exhibit a positive effect on bone formation. Therefore, the aim of this study was to (i) develop porous polyurethane scaffolds containing strontium SrHA nanoparticles (PU/SrHA) and (ii) compare their in vitro biological performance for applications in bone regeneration to PU scaffolds. SrHA and HA was synthesized using a conventional wet-chemical neutralization reaction at temperatures of 25, 50, and 80°C. Chemical analysis was performed by inductively coupled plasma-optical emission spectrometry. Synthesizing temperatures at 25 and at 50°C were selected for the composite preparation (abbreviated as HA-25, SrHA-25, HA-50, and SrHA-50, respectively). PU was synthesized from isophorone diisocyanate, polytetramethylene ether glycol, and 1,4-butanediol. Composite scaffolds were prepared by addition of HA or SrHA nanoparticles into PU scaffolds during polymer preparation. The results showed that the Sr content in HA nanoparticles increased with increasing synthesis temperature. The addition of nanoparticles decreased the elongation-at-break and tensile strength, but significantly increased the surface wettability of the PU scaffolds. In vitro degradation tests demonstrated that release of cations was significantly higher from PU/SrHA-50 composite scaffolds. Cell culture tests indicated that PU composites containing either HA or SrHA nanoparticles increased proliferation of bone marrow stem cells as compared to plain PU scaffolds, whereas osteogenic differentiation was not affected by the incorporation of HA nanoparticles irrespective of the incorporation of Sr. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014. PMID:25203691

Sariibrahimoglu, Kemal; Yang, Wanxun; Leeuwenburgh, Sander C G; Yang, Fang; Wolke, Joop G C; Zuo, Yi; Li, Yubao; Jansen, John A

2014-09-01

286

Development of wear resistant NFSS-HA novel biocomposites and study of their tribological properties for orthopaedic applications.  

PubMed

Implants made of nickel free austenitic stainless steel can reduce the toxic effect of released nickel ion and compounds from the conventional stainless steels. On the other hand, hydroxyapatite is a ceramic which has been used in orthopaedic applications due to its good osteoconductivity, biocompatibility and bioactivity. However, there is no evidence in the literature up to now on producing composites based on nickel free stainless steel and hydroxyapatite and study of their tribology. The aim of this work was to produce novel biocomposites made up of nickel free stainless steel with hydroxyapatite (prepared by heat treating bone ash) and studying their tribology under various loads in air and in Ringer's physiological solution. Different amounts of hydroxyapatite powder (10, 20, 30 and 40% Vol.) were added to this nickel free stainless steel powder to get the biocomposites. Variation of their density, hardness, wear resistance and friction with the ceramic (hydroxyapatite) content and wear load were investigated in air and in Ringer's solution. The density of the composites was decreased by increasing the volume percentage of the hydroxyapatite, while wear resistance of the composites was increased. The wear mechanism of these composites was changed by increasing the wear load and consequently the volume loss was enhanced dramatically. Furthermore, by increasing the sliding distance, the rate of volume loss was decreased slightly. The friction coefficient of the composites was also decreased by increasing the weight percentage of hydroxyapatite. Effect of the physiological Ringer's solution on wear resistance and friction coefficient of the composites was nearly negligible. The wear mechanisms of the samples were identified by studying the SEM images of the worn surfaces of the tested samples in different wear loads and HA contents. PMID:20129417

Younesi, M; Bahrololoom, M E; Fooladfar, H

2010-02-01

287

Preparation of nano-hydroxyapatite particles with different morphology and their response to highly malignant melanoma cells in vitro  

NASA Astrophysics Data System (ADS)

To investigate the effects of nano-hydroxyapatite (HA) particles with different morphology on highly malignant melanoma cells, three kinds of HA particles with different morphology were synthesized and co-cultured with highly malignant melanoma cells using phosphate-buffered saline (PBS) as control. A precipitation method with or without citric acid addition as surfactant was used to produce rod-like hydroxyapatite (HA) particles with nano- and micron size, respectively, and a novel oil-in-water emulsion method was employed to prepare ellipse-like nano-HA particles. Particle morphology and size distribution of the as prepared HA powders were characterized by transmission electron microscope (TEM) and dynamic light scattering technique. The nano- and micron HA particles with different morphology were co-cultured with highly malignant melanoma cells. Immunofluorescence analysis and MTT assay were employed to evaluate morphological change of nucleolus and proliferation of tumour cells, respectively. To compare the effects of HA particles on cell response, the PBS without HA particles was used as control. The experiment results indicated that particle nanoscale effect rather than particle morphology of HA was more effective for the inhibition on highly malignant melanoma cells proliferation.

Li, Bo; Guo, Bo; Fan, Hongsong; Zhang, Xingdong

2008-11-01

288

Fiber-coupled microsphere laser  

Microsoft Academic Search

We demonstrate a 1.5-mm-wavelength fiber laser formed by placement of glass microsphere resonators along a fiber taper. The fiber taper serves the dual purpose of transporting optical pump power into the spheres and extracting the resulting laser emission. A highly doped erbium:ytterbium phosphate glass was used to form microsphere resonant cavities with large gain at 1.5 mm. Laser threshold pump

M. Cai; K. J. Vahala; P. C. Sercel

2000-01-01

289

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

290

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

291

MC3T3-E1 osteoblast attachment and proliferation on porous hydroxyapatite scaffolds fabricated with nanophase powder  

PubMed Central

Porous bone tissue engineering scaffolds were fabricated using both nano hydroxyapatite (nano HA) powder (20 nm average particle size) and micro HA powder (10 ?m average particle size), resulting in sintered scaffolds of 59 vol% porosity and 8.6±1.9 ?m average grain size and 72 vol% porosity and 588±55 nm average grain size, respectively. Scanning electron microscopy was used to measure both the grain size and pore size. MC3T3-E1 osteoblast (OB) attachment and proliferation on both nano HA and micro HA porous scaffolds were quantified. As expected, OB cell number was greater on nano HA scaffolds compared with similarly processed micro HA scaffolds 5 days after seeding, while OB attachment did not appear greater on the nano HA scaffolds (p<0.05). PMID:17722535

Smith, Ian O; McCabe, Laura R; Baumann, Melissa J

2006-01-01

292

Boron nitride nanotube reinforced hydroxyapatite composite: mechanical and tribological performance and in-vitro biocompatibility to osteoblasts.  

PubMed

This study proposes boron nitride nanotube (BNNT) reinforced hydroxyapatite (HA) as a novel composite material for orthopedic implant applications. The spark plasma sintered (SPS) composite structure shows higher density compared to HA. Minimal lattice mismatch between HA and BNNT leads to coherent bonding and strong interface. HA-4 wt% BNNT composite offers excellent mechanical properties-120% increment in elastic modulus, 129% higher hardness and 86% more fracture toughness, as compared to HA. Improvements in the hardness and fracture toughness are related to grain refinement and crack bridging by BNNTs. HA-BNNT composite also shows 75% improvement in the wear resistance. The wear morphology suggests localized plastic deformation supported by the sliding of outer walls of BNNT. Osteoblast proliferation and cell viability show no adverse effect of BNNT addition. HA-BNNT composite is, thus, envisioned as a potential material for stronger orthopedic implants. PMID:21094479

Lahiri, Debrupa; Singh, Virendra; Benaduce, Ana Paula; Seal, Sudipta; Kos, Lidia; Agarwal, Arvind

2011-01-01

293

Development and Characterization of Biphasic Hydroxyapatite/?-TCP Cements  

PubMed Central

Biphasic calcium phosphate bioceramics composed of hydroxyapatite (HA) and ?-tricalcium phosphate (?-TCP) have relevant properties as synthetic bone grafts, such as tunable resorption, bioactivity, and intrinsic osteoinduction. However, they have some limitations associated to their condition of high-temperature ceramics. In this work self-setting Biphasic Calcium Phosphate Cements (BCPCs) with different HA/?-TCP ratios were obtained from self-setting ?-TCP/?-TCP pastes. The strategy used allowed synthesizing BCPCs with modulated composition, compressive strength, and specific surface area. Due to its higher solubility, ?-TCP was fully hydrolyzed to a calcium-deficient HA (CDHA), whereas ?-TCP remained unreacted and completely embedded in the CDHA matrix. Increasing amounts of the non-reacting ?-TCP phase resulted in a linear decrease of the compressive strength, in association to the decreasing amount of precipitated HA crystals, which are responsible for the mechanical consolidation of apatitic cements. Ca2+ release and degradation in acidic medium was similar in all the BCPCs within the timeframe studied, although differences might be expected in longer term studies once ?-TCP, the more soluble phase was exposed to the surrounding media.

Gallinetti, Sara; Canal, Cristina; Ginebra, Maria-Pau; Ferreira, J

2014-01-01

294

A functional agarose-hydroxyapatite scaffold for osteochondral interface regeneration  

PubMed Central

Regeneration of the osteochondral interface is critical for integrative and functional cartilage repair. This study focuses on the design and optimization of a hydrogel-ceramic composite scaffold of agarose and hydroxyapatite (HA) for calcified cartilage formation. The first study objective was to compare the effects of HA on non-hypertrophic and hypertrophic chondrocytes cultured in the composite scaffold. Specifically, cell growth, biosynthesis, hypertrophy, and scaffold mechanical properties were evaluated. Next, the ceramic phase of the scaffold was optimized in terms of particle size (200 nm vs. 25 µm) and dose (0–6 w/v%). It was observed that while deep zone chondrocyte (DZC) biosynthesis and hypertrophy remained unaffected, hypertrophic chondrocytes measured higher matrix deposition and mineralization potential with the addition of HA. Most importantly, higher matrix content translated into significant increases in both compressive and shear mechanical properties. While cell hypertrophy was independent of ceramic size, matrix deposition was higher only with the addition of micron-sized ceramic particles. In addition, the highest matrix content, mechanical properties and mineralization potential were found in scaffolds with 3% micro-HA, which approximates both the mineral aggregate size and content of the native interface. These results demonstrate that the biomimetic hydrogel-ceramic composite is optimal for calcified cartilage formation and is a promising design strategy for osteochondral interface regeneration. PMID:22531222

Khanarian, Nora T.; Haney, Nora M.; Burga, Rachel A.; Lu, Helen H.

2013-01-01

295

Hydroxyapatite Formation on a Novel Dental Cement in Human Saliva  

PubMed Central

Dental materials have to meet high standards regarding mechanical strength and handling properties. There is however only a limited amount of research that has been devoted to natural formation of hydroxyapatite (HA) in contact with the materials. The objective of the current investigation was to study the surface reactions occurring in human salvia on a novel dental cement. Ceramir Crown & Bridge, a bioceramic luting agent intended for permanent cementation of conventional oral prosthetics, was evaluated by immersing discs made from the cement in human saliva and phosphate buffered saline (PBS) for seven days, after which they were dried and analyzed. The analytical methods used in order to verify HA formation on the surface were grazing incidence X-ray diffraction (GI-XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). All results showed that HA was formed on the surfaces of samples stored in saliva as well as on samples stored in PBS. The possibility of a dental luting cement to promote natural formation of HA at the tooth interface increases the stability and durability of the system and could help prevent secondary caries. PMID:23056955

Engstrand, Johanna; Unosson, Erik; Engqvist, Håkan

2012-01-01

296

A functional agarose-hydroxyapatite scaffold for osteochondral interface regeneration.  

PubMed

Regeneration of the osteochondral interface is critical for integrative and functional cartilage repair. This study focuses on the design and optimization of a hydrogel-ceramic composite scaffold of agarose and hydroxyapatite (HA) for calcified cartilage formation. The first study objective was to compare the effects of HA on non-hypertrophic and hypertrophic chondrocytes cultured in the composite scaffold. Specifically, cell growth, biosynthesis, hypertrophy, and scaffold mechanical properties were evaluated. Next, the ceramic phase of the scaffold was optimized in terms of particle size (200 nm vs. 25 ?m) and dose (0-6 w/v%). It was observed that while deep zone chondrocyte (DZC) biosynthesis and hypertrophy remained unaffected, hypertrophic chondrocytes measured higher matrix deposition and mineralization potential with the addition of HA. Most importantly, higher matrix content translated into significant increases in both compressive and shear mechanical properties. While cell hypertrophy was independent of ceramic size, matrix deposition was higher only with the addition of micron-sized ceramic particles. In addition, the highest matrix content, mechanical properties and mineralization potential were found in scaffolds with 3% micro-HA, which approximates both the mineral aggregate size and content of the native interface. These results demonstrate that the biomimetic hydrogel-ceramic composite is optimal for calcified cartilage formation and is a promising design strategy for osteochondral interface regeneration. PMID:22531222

Khanarian, Nora T; Haney, Nora M; Burga, Rachel A; Lu, Helen H

2012-07-01

297

Biomimetic helical rosette nanotubes and nanocrystalline hydroxyapatite coatings on titanium for improving orthopedic implants  

PubMed Central

Natural bone consists of hard nanostructured hydroxyapatite (HA) in a nanostructured protein-based soft hydrogel template (ie, mostly collagen). For this reason, nanostructured HA has been an intriguing coating material on traditionally used titanium for improving orthopedic applications. In addition, helical rosette nanotubes (HRNs), newly developed materials which form through the self-assembly process of DNA base pair building blocks in body solutions, are soft nanotubes with a helical architecture that mimics natural collagen. Thus, the objective of this in vitro study was for the first time to combine the promising attributes of HRNs and nanocrystalline HA on titanium and assess osteoblast (bone-forming cell) functions. Different sizes of nanocrystalline HA were synthesized in this study through a wet chemical precipitation process following either hydrothermal treatment or sintering. Transmission electron microscopy images showed that HRNs aligned with nanocrystalline HA, which indicates a high affinity between both components. Some of the nanocrystalline HA formed dense coatings with HRNs on titanium. More importantly, results demonstrated enhanced osteoblast adhesion on the HRN/nanocrystalline HA-coated titanium compared with conventional uncoated titanium. Among all the HRN/nanocrystalline HA coatings tested, osteoblast adhesion was the greatest when HA nanometer particle size was the smallest. In this manner, this study demonstrated for the first time that biomimetic HRN/nanocrystalline HA coatings on titanium were cytocompatible for osteoblasts and, thus, should be further studied for improving orthopedic implants. PMID:18990941

Zhang, Lijie; Chen, Yupeng; Rodriguez, Jose; Fenniri, Hicham; Webster, Thomas J

2008-01-01

298

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

299

Osteodifferentiation of mesenchymal stem cells on chitosan/hydroxyapatite composite films.  

PubMed

Chitosan (Ch) is one of the most commonly used natural biomaterials. Osteodifferentiation of mesenchymal stem cells (MSCs) on Ch has drawn extensive interest. Hydroxyapatite (HA) is a component of skeleton and teeth with good biocompatibility. Combination with HA may be a good method to modify Ch to facilitate cellular behaviors and functions on it. In this study, Ch/HA film was prepared and characterized. Its potential to benefit cellular behaviors and osteodifferentiation of MSCs was evaluated. Resultantly, physical properties of composite Ch/HA, including water-in-air contact angle, tensile strength, elastic modulus, and breaking elongation were favorably modified. In cellular culture medium, Ch/HA films absorbed more Ca(2+) than Ch films, and more HA crystalline growths on Ch/HA films. 3-(4,5-Dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and morphological features showed better proliferation and adhesion of MSCs on Ch/HA films. Osteodifferentiation of MSCs on Ch/HA was promoted, indicated by modified transcription level of osteocalcin, osteopontin, collagen I, alkaline phosphatase (ALP), and induced ALP activity. These data suggest biocompatibility of Ch is modified after being blended with HA, which promotes osteodifferentiation of MSCs. This can be a promising approach to modify Ch for its applications in bone tissue engineering. PMID:23589442

Yang, Julin; Liu, Aiming; Han, Yuanyuan; Li, Qingning; Tian, Jinhuan; Zhou, Changren

2014-04-01

300

Fluorescence microscopic analysis of bone osseointegration of strontium-substituted hydroxyapatite implants*  

PubMed Central

The purpose of this study was to analyze the effect of strontium-substituted hydroxyapatite (Sr-HA) on bone osseointegration of the implants using fluorescence microscopy. We allocated 20 implants to two groups: Sr-HA group and HA group. Electrochemically deposited HA and Sr-HA coatings were applied onto the implants separately. All the implants were inserted into femur bone of rabbits. Oxytetracycline hydrochloride, alizarin-complexon, and calcein green were respectively administered 7, 28, and 46 d after the implantation. After eight weeks, femurs were retrieved and prepared for the fluorescence microscopy observation. We analyzed the bone mineral apposition rates (MARs), bone area ratios (BARs), and bone to implant contact (BIC) of the two groups. Fluorescence microscopic observation showed that all groups exhibited extensive early peri-implant bone formation. The MAR of the Sr-HA group was greater than that for pure HA from 7 to 28 d after implantation, but no significant difference was found at later stage. And the BIC showed difference at 7 and 28 d compared with pure HA. We concluded that Sr-HA coating can improve the bone osseointegration of the implant in the early stage compared with the HA coating. PMID:22556174

Fu, Dan-li; Jiang, Qiao-hong; He, Fu-ming; Yang, Guo-li; Liu, Li

2012-01-01

301

Phase stability and biological property evaluation of plasma sprayed hydroxyapatite coatings for orthopedic and dental applications.  

PubMed

In this work we have investigated the effects of strontium (Sr) dopant on in vitro protein release kinetics and in vivo osteogenic properties of plasma sprayed hydroxyapatite (HA) coatings, along with their dissolution behavior. Plasma sprayed HA coatings are widely used in load-bearing implants. Apart from osseointegration, the new generation of HA coating is expected to deliver biomolecules and/or drugs that can induce osteoinduction. This paper reports the preparation of crystalline and amorphous HA coatings on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray, and their stability at different solution pH. Coatings prepared at 110mm working distance from the nozzle showed an average Ca ion release of 18 and 90ppm in neutral and acidic environments, respectively. Decreasing the working distance to 90mm resulted in the formation of a coating with less crystalline HA and phases with higher solubility products, and consequently higher dissolution over 32days. A 92% release of a model protein bovine serum albumin (BSA) in phosphate buffer with pH of 7.4 was measured for Sr-doped HA (Sr-HA) coating, while only a 72% release could be measured for pure HA coating. Distortion of BSA during adsorption on coatings revealed a strong interaction between the protein and the coating, with an increase in ?-helix content. Osteoid formation was found on Sr-HA implants as early as 7weeks post implantation compared to HA coated and uncoated Ti implants. After 12weeks post implantation, osteoid new bone was formed on HA implants; whereas, bone mineralization started on Sr-HA samples. While no osteoid was formed on bare Ti surfaces, bone was completely mineralized on HA and Sr-HA coatings after 16weeks post implantation. Our results show that both phase stability and chemistry can have a significant influence toward in vitro and in vivo response of HA coatings on Ti implants. PMID:25638672

Vahabzadeh, Sahar; Roy, Mangal; Bandyopadhyay, Amit; Bose, Susmita

2015-04-15

302

In vitro corrosion resistance and cytocompatibility of nano-hydroxyapatite reinforced Mg–Zn–Zr composites  

Microsoft Academic Search

Due to good biocompatibility and mechanical properties, magnesium (Mg) and its alloys are considered promising degradable\\u000a materials for orthopedic applications. In this work, a Mg metal matrix composite (MMC) was fabricated using Mg-2.9Zn-0.7Zr\\u000a alloy as the matrix and 1 wt% nano-hydroxyapatite (n-HA) particles as reinforcements. In vitro corrosion behavior and cytocompatibility\\u000a of a Mg–Zn–Zr\\/n-HA composite and a Mg–Zn–Zr alloy were investigated.

Xinyu YeMinfang ChenMeng Yang; Minfang Chen; Meng Yang; Jun Wei; Debao Liu

2010-01-01

303

High-strength nanograined and translucent hydroxyapatite monoliths via continuous hydrothermal synthesis and optimized spark plasma sintering.  

PubMed

The synthesis of high-strength, completely dense nanograined hydroxyapatite (bioceramic) monoliths is a challenge as high temperatures or long sintering times are often required. In this study, nanorods of hydroxyapatite (HA) and calcium-deficient HA (made using a novel continuous hydrothermal flow synthesis method) were consolidated using spark plasma sintering (SPS) up to full theoretical density in ?5 min at temperatures up to 1000°C. After significant optimization of the SPS heating and loading cycles, fully dense HA discs were obtained which were translucent, suggesting very high densities. Significantly high three-point flexural strength values for such materials (up to 158 MPa) were measured. Freeze-fracturing of disks followed by scanning electron microscopy investigation revealed selected samples possessed sub-200 nm sized grains and no visible pores, suggesting they were fully dense. PMID:20883835

Chaudhry, Aqif A; Yan, Haixue; Gong, Kenan; Inam, Fawad; Viola, Giuseppe; Reece, Mike J; Goodall, Josephine B M; ur Rehman, Ihtesham; McNeil-Watson, Fraser K; Corbett, Jason C W; Knowles, Jonathan C; Darr, Jawwad A

2011-02-01

304

Preliminary report on the biocompatibility of a moldable, resorbable, composite bone graft consisting of calcium phosphate cement and poly(lactide-co-glycolide) microspheres.  

PubMed

We have assessed the biocompatibility of a new composite bone graft consisting of calcium phosphate cement (CPC) and poly(lactide-co-glycolide) (PLGA) microspheres (approximate diameter of 0.18-0.36 mm) using cell culture techniques. CPC powder is mixed with PLGA microspheres and water to yield a workable paste that could be sculpted to fit the contours of a wound. The cement then hardens into a matrix of hydroxyapatite microcrystals containing PLGA microspheres. The rationale for this design is that the microspheres will initially stabilize the graft but can then degrade to leave behind macropores for colonization by osteoblasts. The CPC matrix could then be resorbed and replaced with new bone. In the present study, osteoblast-like cells (MC3T3-E1 cells) were seeded onto graft specimens and evaluated with fluorescence microscopy, environmental scanning electron microscopy and the Wst-1 assay (an enzymatic assay for mitochondrial dehydrogenase activity). Cells were able to adhere, attain a normal morphology, proliferate and remain viable when cultured on the new composite graft (CPC-PLGA) or on a control graft (CPC alone). These results suggest that our new cement consisting of CPC and PLGA microspheres is biocompatible. This is the first time that a 'polymer-in-mineral' (PLGA microspheres dispersed in a CPC matrix) cement has been formulated that is moldable, resorbable and that can form macropores after the cement has set. PMID:12038620

Simon, Carl G; Khatri, Chetan A; Wight, Scott A; Wang, Francis W

2002-05-01

305

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

306

Delineation of the hydroxyapatite-nucleating domains of bone sialoprotein.  

PubMed

Bone sialoprotein (BSP) is a highly modified, anionic phosphoprotein that is expressed almost exclusively in mineralizing connective tissues and has been shown to be a potent nucleator of hydroxyapatite (HA). Two polyglutamic acid (poly[E]) regions, predicted to be in an alpha-helical conformation and located in the amino-terminal half of the molecule, are believed to be responsible for this activity. Using a prokaryotic expression system, full-length rat BSP was expressed and tested for HA nucleating activity in a steady-state agarose gel system. The unmodified protein is less potent than native bone BSP, indicating a role for the post-translational modifications in HA nucleation. Site-directed mutagenesis of the poly[E] regions in full-length BSP was performed, replacing the poly[E] with either polyaspartic acid (poly[D]) or polyalanine (poly[A]) to examine role of charge and conformation, respectively, in HA nucleation. Replacement of single domains with either poly[A] or poly[D] did not alter nucleating activity nor did replacement of both domains with poly[D]. Replacement of both domains with poly[A], however, significantly decreased nucleating activity. In addition, two recombinant peptides, each encompassing one of the two poly[E] domains, were expressed and tested for nucleating activity. Whereas the peptide encompassing the second poly[E] domain was capable of nucleating HA, the first domain peptide showed no activity. The conformation of the wild-type and mutated proteins and peptides were studied by circular dichroism and small angle x-ray scattering, and no secondary structure was evident. These results demonstrate that a sequence of at least eight contiguous glutamic acid residues is required for the nucleation of HA by BSP and that this nucleating "site" is not alpha-helical in conformation. PMID:12493752

Tye, Coralee E; Rattray, Kevin R; Warner, Kevin J; Gordon, Jonathan A R; Sodek, Jaro; Hunter, Graeme K; Goldberg, Harvey A

2003-03-01

307

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

308

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

309

Ultrafine palladium particles immobilized on polymer microspheres  

Microsoft Academic Search

Ultrafine palladium particles immobilized on submicrometer copolymer microspheres were prepared by reduction of palladium\\u000a ions in the presence of the copolymer microspheres. Copolymer microspheres with surface carboxylic or cyano functionality\\u000a were used. Transmission electron microscopy observation and X-ray diffraction analysis indicated that ultrafine palladium\\u000a particles of nanometer size were formed and were attached on the surface of the copolymer microspheres.

P. H. Wang; C.-Y. Pan

2001-01-01

310

Bone tissue engineering with a collagen-hydroxyapatite scaffold and culture expanded bone marrow stromal cells.  

PubMed

Osteoprogenitor cells combined with supportive biomaterials represent a promising approach to advance the standard of care for bone grafting procedures. However, this approach faces challenges, including inconsistent bone formation, cell survival in the implant, and appropriate biomaterial degradation. We have developed a collagen-hydroxyapatite (HA) scaffold that supports consistent osteogenesis by donor-derived osteoprogenitors, and is more easily degraded than a pure ceramic scaffold. Herein, the material properties are characterized as well as cell attachment, viability, and progenitor distribution in vitro. Furthermore, we examined the biological performance in vivo in a critical-size mouse calvarial defect. To aid in the evaluation of the in-house collagen-HA scaffold, the in vivo performance was compared with a commercial collagen-HA scaffold (Healos(®) , Depuy). The in-house collagen-HA scaffold supported consistent bone formation by predominantly donor-derived osteoblasts, nearly completely filling a 3.5 mm calvarial defect with bone in all samples (n?=?5) after 3 weeks of implantation. In terms of bone formation and donor cell retention at 3 weeks postimplantation, no statistical difference was found between the in-house and commercial scaffold following quantitative histomorphometry. The collagen-HA scaffold presented here is an open and well-defined platform that supports robust bone formation and should facilitate the further development of collagen-hydroxyapatite biomaterials for bone tissue engineering. PMID:24909953

Villa, Max M; Wang, Liping; Huang, Jianping; Rowe, David W; Wei, Mei

2015-02-01

311

POST-TRANSLATIONAL MODIFICATION OF OSTEOPONTIN: EFFECTS on in vitro HYDROXYAPATITE FORMATION and GROWTH  

PubMed Central

The manuscript tests the hypothesis that posttranslational modification of the SIBLING family of proteins in general and osteopontin in particular modify the abilities of these proteins to regulate in vitro hydroxyapatite (HA) formation. Osteopontin has diverse effects on hydroxyapatite (HA) mineral crystallite formation and growth depending on the extent of phosphorylation. We hypothesized that different regions of full-length OPN would also have distinct effects on the mineralization process. Thrombin fragmentation of milk OPN (mOPN) was used to test this hypothesis. Three fragments were tested in a de novo HA formation assay; an N-terminal fragment (aa 1–147), a central fragment (aa 148–204) denoted SKK-fragment and a C-terminal fragment (aa 205–262). Compared to intact mOPN the C- and N-terminal fragments behaved comparably, promoting HA formation and growth, but the central SKK-fragment acted as a mineralization inhibitor. In a seeded growth experiment all fragments inhibited mineral proliferation, but the SKK-fragment was the most effective inhibitor. These effects, seen in HA-formation and seeded growth assays in a gelatin gel system and in a pH-stat experiment were lost when the protein or fragments were dephosphorylated. Effects of the fully phosphorylated protein and fragments were also altered in the presence of fibrillar collagen. The diverse effects can be explained in terms of the intrinsically disordered nature of OPN and its fragments which enable them to interact with their multiple partners. PMID:22342723

Boskey, Adele L.; Christensen, Brian; Taleb, Hayat; Sørensen, Esben S.

2012-01-01

312

UV curable polyurethane-based microspheres  

Microsoft Academic Search

Radiation curable polyurethane-based microspheres were prepared by modifying conventional procedures for preparing anionic polyurethane dispersions. Vinyl groups were introduced to the side chains and the ends of the polyurethane main chains. Photoinitiators and multifunctional acrylate oligomers were incorporated into each microsphere. The curing behavior of the films obtained from these microspheres under UV were studied. The MEK resistance of UV

Masakazu Hirose; Jianhui Zhou; Fumiyuki Kadowaki

1999-01-01

313

Fabrication of glass microspheres with conducting surfaces  

Microsoft Academic Search

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

Elsholz

1984-01-01

314

Hollow glass microsphere composites: preparation and properties  

Microsoft Academic Search

Composites consisting of bonded hollow glass microspheres are promising for constructions in which materials are needed that combine a high Young's modulus with a low density. The elastic properties of ideally bonded hollow glass microsphere composites are predicted theoretically. Heat-treated castings of quartz glass microspheres approach the theoretical Young's modulus from below. The best result achieved was a Young's modulus

H. Verweij; D. Veeneman

1985-01-01

315

Fabrication of glass microspheres with conducting surfaces  

Microsoft Academic Search

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

Elsholz

1982-01-01

316

Strontium and zoledronate hydroxyapatites graded composite coatings for bone prostheses.  

PubMed

Both strontium and zoledronate (ZOL) are known to be useful for the treatment of bone diseases associated to the loss of bone substance. In this work, we applied an innovative technique, Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE), to deposit gradient thin films with variable compositions of Sr-substituted hydroxyapatite (SrHA) and ZOL modified hydroxyapatite (ZOLHA) on Titanium substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. The coatings display good crystallinity and granular morphology, which do not vary with composition. Osteoblast-like MG63 cells and human osteoclasts were co-cultured on the thin films up to 21days. The results show that Sr counteracts the negative effect of relatively high concentration of ZOL on osteoblast viability, whereas both Sr and ZOL enhance extracellular matrix deposition. In particular, ZOL promotes type I collagen production, whereas Sr increases the production of alkaline phosphatase. Moreover, ZOL exerts a greater effect than Sr on osteoprotegerin/RANKL ratio and, as a consequence, on the reduction of osteoclast proliferation and activity. The deposition method allows to modulate the composition of the thin films and hence the promotion of bone growth and the inhibition of bone resorption. PMID:25706198

Boanini, Elisa; Torricelli, Paola; Sima, Felix; Axente, Emanuel; Fini, Milena; Mihailescu, Ion N; Bigi, Adriana

2015-06-15

317

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

318

Substituted Hydroxyapatites with Antibacterial Properties  

PubMed Central

Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency. PMID:24949423

Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Ró?ycka, Dagmara

2014-01-01

319

[Fracture of macroporous hydroxyapatite prosthesis].  

PubMed

Different prosthesis implants are offered to perform a cranioplasty after a decompressive craniectomy when autologous bone graft cannot be used. The authors report the case of a 25-year-old man who benefited a unilateral decompressive craniectomy after a severe head trauma. Seven months later, a cranioplasty using custom macroporous hydroxyapatite prosthesis was performed. The postoperative course was marked by a generalized seizure leading to a traumatic head injury. The CT-scan showed a comminutive fracture of the prosthesis and an extradural hematoma. The patient underwent a removal of the fractured prosthesis and an evacuation of the extradural clot. The postoperative course was uneventful with a Glasgow outcome scale score at 5. A second cranioplasty using a polyether ether ketone (PEEK) implant was performed. Among cranioplasty prosthesis solutions, hydroxyapatite implants seem to have similar property to the bone. However, its weak mechanic resistance is an actual problem in patients susceptible to present generalized seizures with consecutive head impact. Hence, in patients with decompressive craniectomy who are exposed to potential brain injury, we favor the use of more resistant implant as PEEK prosthesis. PMID:22898300

Adetchessi, A T; Pech-Gourg, G; Metellus, P; Fuentes, S

2012-12-01

320

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

321

Porous hydroxyapatite and biphasic calcium phosphate ceramics promote ectopic osteoblast differentiation from mesenchymal stem cells  

NASA Astrophysics Data System (ADS)

Because calcium phosphate (Ca-P) ceramics have been used as bone substitutes, it is necessary to investigate what effects the ceramics have on osteoblast maturation. We prepared three types of Ca-P ceramics with different Ca-P ratios, i.e. hydroxyapatite (HA), beta-tricalcium phosphate (?-TCP), and biphasic calcium phosphate (BCP) ceramics with dense-smooth and porous structures. Comprehensive gene expression microarray analysis of mouse osteoblast-like cells cultured on these ceramics revealed that porous Ca-P ceramics considerably affected the gene expression profiles, having a higher potential for osteoblast maturation. In the in vivo study that followed, porous Ca-P ceramics were implanted into rat skeletal muscle. Sixteen weeks after the implantation, more alkaline-phosphatase-positive cells were observed in the pores of hydroxyapatite and BCP, and the expression of the osteocalcin gene (an osteoblast-specific marker) in tissue grown in pores was also higher in hydroxyapatite and BCP than in ?-TCP. In the pores of any Ca-P ceramics, 16 weeks after the implantation, we detected the expressions of marker genes of the early differentiation stage of chondrocytes and the complete differentiation stage of adipocytes, which originate from mesenchymal stem cells, as well as osteoblasts. These marker gene expressions were not observed in the muscle tissue surrounding the implanted Ca-P ceramics. These observations indicate that porous hydroxyapatite and BCP had a greater potential for promoting the differentiation of mesenchymal stem cells into osteoblasts than ?-TCP.

Zhang, Lingli; Hanagata, Nobutaka; Maeda, Megumi; Minowa, Takashi; Ikoma, Toshiyuki; Fan, Hongsong; Zhang, Xingdong

2009-04-01

322

Collagen type I increases bone remodelling around hydroxyapatite implants in the rat tibia.  

PubMed

The early interface reaction of cancellous bone to a nanocrystalline hydroxyapatite (HA) cement containing 3 wt% collagen type I (HA/Coll) with a setting under physiological temperature and pH was observed using immunohistochemical techniques. Pure HA served as a control. Cylinders with a diameter of 2 mm were implanted into the proximal tibia of 72 adult Wistar rats. Histological sections of 6 animals were prepared after 1, 2, 4, 6, 14 and 28 days. First, osteoblast-like cells as well as a marked reaction for osteonectin, osteopontin and its ligand CD44 were observed as early as 2 days after implantation at the interface around HA/Coll implants. Further, reactivity for ED1 and cathepsin D, both markers for phagocytotic cells, appeared earlier and stronger around HA/Coll. In cell counts, a significantly higher average number of ED1- and cathepsin D-positive phagocytotic cells was observed around the HA/Coll implants on days 6 (p < 0.01), 14 and 28 (p < 0.05). The number of osteopontin-positive cells was significantly higher around HA/Coll implants at days 6 and 14 (p < 0.05). Two weeks after the implantation, first islands of newly formed woven bone were observed around the HA/Coll implant, but not around the control implant. The amount of direct bone contact after 28 days averaged 28% around pure HA and 51% around HA/Coll implants (p < 0.05). While both implants displayed a good osteoconductivity, a higher bone remodelling activity was observed around collagen-containing HA implants compared to pure HA implants. It appears that the addition of collagen to HA implants can enhance both phagocytotic and osteogenic processes. This may result in an earlier acceptance and better osseointegration of the HA/Coll implants into the surrounding tissue. PMID:15655332

Rammelt, Stefan; Schulze, Eva; Witt, Martin; Petsch, Elisabeth; Biewener, Achim; Pompe, Wolfgang; Zwipp, Hans

2004-01-01

323

Tunable Hydrogel-Microsphere Composites that Modulate Local Inflammation and Collagen Bulking  

PubMed Central

Injectable biomaterials alone may alter local tissue responses, including inflammatory cascades and matrix production (e.g., stimulatory dermal fillers are used as volumizing agents that induce collagen production). To expand upon the available material compositions and timing of presentation, a tunable hyaluronic acid (HA) and poly(lactide-co-glycolide) (PLGA) microsphere composite system was formulated and assessed in subcutaneous and cardiac tissues. HA functionalized with hydroxyethyl methacrylate (HeMA) was used as a precursor to injectable and degradable hydrogels that carry PLGA microspheres (~50 m diameter) to tissues, where the HA hydrogel degradation (~20 or 70 days) and quantity of PLGA microspheres (0–300 mg/ml) are readily varied. When implanted subcutaneously, faster hydrogel degradation and more microspheres (e.g., 75mg/mL) generally induced more rapid tissue and cellular interactions and a greater macrophage response. In cardiac applications, tissue bulking may be useful to alter stress profiles and to stabilize the tissue after infarction, limiting left ventricular (LV) remodeling. When fast degrading HeMA-HA hydrogels containing 75 mg/mL microspheres were injected into infarcted tissue in sheep, LV dilation was limited and the thickness of the myocardial wall and the presence of vessels in the apical infarct region were increased ~35% and ~60%, respectively, compared to empty hydrogels. Both groups decreased volume changes and infarct areas at 8 weeks, compared to untreated controls. This work illustrates the importance of material design in expanding the application of tissue bulking composites to a range of biomedical applications. PMID:22659176

Tous, Elena; Weber, Heather M.; Lee, Myung Han; Koomalsingh, Kevin J.; Shuto, Takashi; Kondo, Norihiro; Gorman, Joseph H.; Lee, Daeyeon; Gorman, Robert C.; Burdick, Jason A.

2012-01-01

324

In vitro corrosion and cytocompatibility properties of nano-whisker hydroxyapatite coating on magnesium alloy for bone tissue engineering applications.  

PubMed

We report here the successful fabrication of nano-whisker hydroxyapatite (nHA) coatings on Mg alloy by using a simple one-step hydrothermal process in aqueous solution. The nHA coating shows uniform structure and high crystallinity. Results indicate that nHA coating is promising for improving the in vitro corrosion and cytocompatibility properties of Mg-based implants and devices for bone tissue engineering. In addition, the simple hydrothermal deposition method used in the current study is also applicable to substrates with complex shapes or surface geometries. PMID:25789500

Yang, Huawei; Yan, Xueyu; Ling, Min; Xiong, Zuquan; Ou, Caiwen; Lu, Wei

2015-01-01

325

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

326

[Research on the extracorporeal cytocompatibility of a composite of HA, carbon fiber and polyetheretherket-one].  

PubMed

The present research was to study the biocompatibility of a composite of hydroxyapatite (HA), carbon fiber (CF) and polyetheretherket-one (PEEK) by co-culturing with the osteoblasts in vitro. Cell relative growth (RGR) was used as a quantitative assessment for cytotoxicity of the biomaterials by CCK-8. The proliferation index of the co-cultured cells and ALP activity was measured to study the effect of PEEK-HA-CF composites. Morphological properties of the osteoblast cells in vitro were observed by scanning electro-microscopy (SEM). The PEEK-HA-CF materials have no cytotoxicity to osteoblasts. The proliferation index of PEEK-HA-CF was higher than that of Ti alloy group, but these was no significant difference compared to that of control group. The ALP activity was the highest on PEEK-HA-CF composites surface after 7 days. The osteoblast cells co-cultured with the PEEK-HA-CF composite were adhered well to the biomaterial as observed under the SEM. The results suggested that the PEEK-HA-CF composites had good biocompatibility in vitro and might be a novel orthopedic implanted material. PMID:22295706

Liu, Xueyong; Deng, Chunbo; Liu, Jiquan; Li, Jianjun; Sui, Guoxin

2011-12-01

327

Strength and fatigue properties of three-step sintered dense nanocrystal hydroxyapatite bioceramics  

NASA Astrophysics Data System (ADS)

Dense hydroxyapatite (HA) ceramic is a promising material for hard tissue repair due to its unique physical properties and biologic properties. However, the brittleness and low compressive strength of traditional HA ceramics limited their applications, because previous sintering methods produced HA ceramics with crystal sizes greater than nanometer range. In this study, nano-sized HA powder was employed to fabricate dense nanocrystal HA ceramic by high pressure molding, and followed by a three-step sintering process. The phase composition, microstructure, crystal dimension and crystal shape of the sintered ceramic were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties of the HA ceramic were tested, and cytocompatibility was evaluated. The phase of the sintered ceramic was pure HA, and the crystal size was about 200 nm. The compressive strength and elastic modulus of the HA ceramic were comparable to human cortical bone, especially the good fatigue strength overcame brittleness of traditional sintered HA ceramics. Cell attachment experiment also demonstrated that the ceramics had a good cytocompatibility.

Guo, Wen-Guang; Qiu, Zhi-Ye; Cui, Han; Wang, Chang-Ming; Zhang, Xiao-Jun; Lee, In-Seop; Dong, Yu-Qi; Cui, Fu-Zhai

2013-06-01

328

Hydroxyapatite bioactivated bacterial cellulose promotes osteoblast growth and the formation of bone nodules  

PubMed Central

The goal of this study was to investigate the feasibility of bacterial cellulose (BC) scaffold to support osteoblast growth and bone formation. BC was produced by culturing Acetobacter xylinum supplemented with hydroxyapatite (HA) to form BC membranes (without HA) and BC/HA membranes. Membranes were subjected to X-ray photoelectron spectroscopy (XPS) analysis to determine surface element composition. The membranes were further used to evaluate osteoblast growth, alkaline phosphatase activity and bone nodule formation. BC was free of calcium and phosphate. However, XPS analysis revealed the presence of both calcium (10%) and phosphate (10%) at the surface of the BC/HA membrane. Osteoblast culture showed that BC alone was non-toxic and could sustain osteoblast adhesion. Furthermore, osteoblast adhesion and growth were significantly (p ?0.05) increased on BC/HA membranes as compared to BC alone. Both BC and BC/HA membranes improved osteoconductivity, as confirmed by the level of alkaline phosphatase (ALP) activity that increased from 2.5 mM with BC alone to 5.3 mM with BC/HA. BC/HA membranes also showed greater nodule formation and mineralization than the BC membrane alone. This was confirmed by Alizarin red staining (ARS) and energy dispersive X-ray spectroscopy (EDX). This work demonstrates that both BC and BC/HA may be useful in bone tissue engineering. PMID:23174338

2012-01-01

329

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

330

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

331

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

332

Hydroxyapatite-coated sillicone rubber enhanced cell adhesion and it may be through the interaction of EF1? and ?-actin.  

PubMed

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

Shi, Xiao-hua; Wang, Shao-liang; Zhang, Yi-ming; Wang, Yi-cheng; Yang, Zhi; Zhou, Xin; Lei, Ze-yuan; Fan, Dong-li

2014-01-01

333

Modeling the Formation of Polyimide Microspheres  

NASA Technical Reports Server (NTRS)

High temperature polyimide microspheres have been developed from polyimide solid residuum by a simple inflation process. Microspheres have been fabricated from several polyimide precursors through the use of a circulating air oven. Microsphere formation and final physical property characterization have been limited to simple mechanical and thermal testing. The present paper focuses on developing an understanding of microsphere formation through simple geometric rules for an incompressible polymeric material and microscopic observations of precursor residuum inflation. Inflation kinematics of the hollow polyimide microspheres as a function of time and temperature is discussed.

Pipes, R. B.; Weiser, E. S.; Gonsoulin, B.; Hubert, P.

2002-01-01

334

Magnetic responsive hydroxyapatite composite scaffolds construction for bone defect reparation  

PubMed Central

Introduction In recent years, interest in magnetic biomimetic scaffolds for tissue engineering has increased considerably. A type of magnetic scaffold composed of magnetic nanoparticles (MNPs) and hydroxyapatite (HA) for bone repair has been developed by our research group. Aim and methods In this study, to investigate the influence of the MNP content (in the scaffolds) on the cell behaviors and the interactions between the magnetic scaffold and the exterior magnetic field, a series of MNP-HA magnetic scaffolds with different MNP contents (from 0.2% to 2%) were fabricated by immersing HA scaffold into MNP colloid. ROS 17/2.8 and MC3T3-E1 cells were cultured on the scaffolds in vitro, with and without an exterior magnetic field, respectively. The cell adhesion, proliferation and differentiation were evaluated via scanning electron microscopy; confocal laser scanning microscopy; and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), alkaline phosphatase, and bone gla protein activity tests. Results The results demonstrated the positive influence of the magnetic scaffolds on cell adhesion, proliferation, and differentiation. Further, a higher amount of MNPs on the magnetic scaffolds led to more significant stimulation. Conclusion The magnetic scaffold can respond to the exterior magnetic field and engender some synergistic effect to intensify the stimulating effect of a magnetic field to the proliferation and differentiation of cells. PMID:22848165

Zeng, Xiao Bo; Hu, Hao; Xie, Li Qin; Lan, Fang; Jiang, Wen; Wu, Yao; Gu, Zhong Wei

2012-01-01

335

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

336

Pulsed laser deposition of strontium-substituted hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

The growing evidence of the beneficial role of strontium in bone has increased the interest of developing strontium-containing biomaterials for medical applications, and specifically biocompatible coatings that can be deposited on metallic implants to benefit from their load-bearing capabilities. In this work, strontium-substituted hydroxyapatite (Sr-HA) coatings have been fabricated by pulsed laser deposition (PLD) from initial targets obtained after mixing and compacting commercial HA and SrCO3 powders in different proportions. The films thus fabricated were then structurally, morphologically and chemically characterized using scanning electron microscopy, optical profilometry, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The macroscopic morphology of the films presented in all cases equivalent spherical shaped aggregates of typical calcium phosphate coatings. The results reveal, however, the incorporation of Sr2+ and carbonate groups in the coatings as a function of the SrCO3 content in the ablation target, being the incorporation of Sr2+ a linear phenomenon that is accompanied by a similarly linear withdrawal of Ca2+. The role of Sr2+ in the modification of the HA structure and a possible mechanism of substitution of Sr2+ atoms in place of Ca2+ atoms are discussed.

Pereiro, I.; Rodríguez-Valencia, C.; Serra, C.; Solla, E. L.; Serra, J.; González, P.

2012-09-01

337

Synthesis of hydroxyapatite via mechanochemical treatment.  

PubMed

Hydroxyapatite powder was synthesized with calcium pyrophosphate (Ca2P2O7) and calcium carbonate (CaCO3) through solid-state reaction. The two powders were mixed in acetone and water, respectively, and the single phase of hydroxyapatite was observed to occur only in the powder milled in water, without the additional supply of water vapor during heat-treatment at 1100 degrees C for 1 h. The results were explained in terms of the mechanochemical reaction that could supply enough amount of hydroxyl group to the starting powders to form a single phase of hydroxyapatite. Practical implication of the results is that the powder of high crystalline hydroxyapatite can be obtained by the simple milling in water and subsequent heat-treatment. PMID:11791918

Rhee, Sang-Hoon

2002-02-01

338

Effects of urinary macromolecules on hydroxyapatite crystal formation.  

PubMed

Particle size analysis was combined with titration data obtained in constant-composition, hydroxyapatite (HA)-seeded, crystal growth assays. With addition of large amounts of HA (250 microg), titration rates were linear, new crystal formation was minimal, and aggregation effects could be detected. With addition of small amounts of HA (62.5 microg), nucleation of new HA was observed. The effects of urinary macromolecules, i.e., osteopontin (OPN), recombinant glutathione-S-transferase-OPN (G-OPN), Tamm-Horsfall protein, chondroitin sulfate, human serum albumin, mixed urinary macromolecules from a stone-former (SFU1), mixed urinary macromolecules from a normal individual (NU1), and polyaspartic acid (PA), were examined in this system. Crystal growth inhibition, as measured by the slope of linear titration curves in this system, was observed with PA, G-OPN, OPN, SFU1, and NU1. All of the macromolecules tested inhibited aggregation, including Tamm-Horsfall protein, which did not inhibit growth. As reflected by the ratio of the final number of particles to the initial number in the 62.5-microg seed addition, the macromolecules that were most effective in inhibiting growth, i.e., OPN, G-OPN, PA, SFU1, and NU1, actually increased secondary nucleation. Recombinant G-OPN demonstrated less inhibitory activity than did OPN isolated from cell culture. Chondroitin sulfate and human serum albumin exhibited no significant effects on the various components of HA crystallization under these conditions. SFU1 and NU1 slowed growth and increased secondary nucleation to similar degrees, and neither exhibited any measurable effect on aggregation. Therefore, crystal surface sites that participate in nucleation, growth, and aggregation processes are affected independently by macromolecules, presumably because of differences in their structural features. These results illustrate the utility of combining these techniques to provide a much greater understanding of crystallization behavior than that possible with either analysis alone. PMID:11562409

Beshensky, A M; Wesson, J A; Worcester, E M; Sorokina, E J; Snyder, C J; Kleinman, J G

2001-10-01

339

Bone integration capability of nanopolymorphic crystalline hydroxyapatite coated on titanium implants  

PubMed Central

The mechanism by which hydroxyapatite (HA)-coated titanium promotes bone–implant integration is largely unknown. Furthermore, refining the fabrication of nano-structured HA to the level applicable to the mass production process for titanium implants is challenging. This study reports successful creation of nanopolymorphic crystalline HA on microroughened titanium surfaces using a combination of flame spray and low-temperature calcination and tests its biological capability to enhance bone–implant integration. Sandblasted microroughened titanium implants and sandblasted + HA-coated titanium implants were subjected to biomechanical and histomorphometric analyses in a rat model. The HA was 55% crystallized and consisted of nanoscale needle-like architectures developed in various diameters, lengths, and orientations, which resulted in a 70% increase in surface area compared to noncoated microroughened surfaces. The HA was free from impurity contaminants, with a calcium/phosphorus ratio of 1.66 being equivalent to that of stoichiometric HA. As compared to microroughened implants, HA-coated implants increased the strength of bone–implant integration consistently at both early and late stages of healing. HA-coated implants showed an increased percentage of bone–implant contact and bone volume within 50 ?m proximity of the implant surface, as well as a remarkably reduced percentage of soft tissue intervention between bone and the implant surface. In contrast, bone volume outside the 50 ?m border was lower around HA-coated implants. Thus, this study demonstrated that the addition of pure nanopolymorphic crystalline HA to microroughened titanium not only accelerates but also enhances the level of bone–implant integration and identified the specific tissue morphogenesis parameters modulated by HA coating. In particular, the nanocrystalline HA was proven to be drastic in increasing osteoconductivity and inhibiting soft tissue infiltration, but the effect was limited to the immediate microenvironment surrounding the implant. PMID:22359461

Yamada, Masahiro; Ueno, Takeshi; Tsukimura, Naoki; Ikeda, Takayuki; Nakagawa, Kaori; Hori, Norio; Suzuki, Takeo; Ogawa, Takahiro

2012-01-01

340

Carbonated apatite and hydroxyapatite in craniofacial reconstruction.  

PubMed

Alloplastic biomaterials have revolutionalized craniofacial reconstruction. Commercially available bone substitute cements allow easy contouring and application, as well as avoidance of postoperative donor site complications. Hydroxyapatite and carbonated apatite are commercially available biomaterials currently being used as moldable bone substitutes in craniofacial reconstruction. This study presents 35 patients with 46 sites of reconstruction using hydroxyapatite or carbonated apatite. The characteristics, effectiveness, advantages, and limitations of each biomaterial are discussed. PMID:12975134

Mathur, Kevin K; Tatum, Sherard A; Kellman, Robert M

2003-01-01

341

On the anisotropic elastic properties of hydroxyapatite.  

NASA Technical Reports Server (NTRS)

Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.

Katz, J. L.; Ukraincik, K.

1971-01-01

342

Production of monodisperse, polymeric microspheres  

NASA Technical Reports Server (NTRS)

Very small, individual polymeric microspheres with very precise size and a wide variation in monomer type and properties are produced by deploying a precisely formed liquid monomer droplet, suitably an acrylic compound such as hydroxyethyl methacrylate into a containerless environment. The droplet which assumes a spheroid shape is subjected to polymerizing radiation such as ultraviolet or gamma radiation as it travels through the environment. Polymeric microspheres having precise diameters varying no more than plus or minus 5 percent from an average size are recovered. Many types of fillers including magnetic fillers may be dispersed in the liquid droplet.

Rembaum, Alan (Inventor); Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chang, Manchium (Inventor)

1990-01-01

343

Physicochemical properties of the novel biphasic hydroxyapatite-magnesium phosphate biomaterial.  

PubMed

Besides high-temperature calcium phosphates (CaPs), low-temperature calcium phosphate bone cements (CPCs), due to excellent biological properties: bioactivity, biocompability and osteoconductivity, are successfully used as bone substitutes. However, some disadvantages, related mainly to their low resorption rate and poor mechanical properties result in limited range of applications of these implant materials to non-loaded places in the skeletal system. To overcome this problem, magnesium phosphate cements (MPCs) with high strength have been considered as biomaterials. The main disadvantage of MPCs is that the acid-base setting reaction is an exothermic process that must be strictly controlled to avoid tissue necrosis. In this work, a new composite bone substitute (Hydroxyapatite Magnesium Phosphate Material - HMPM) based on hydroxyapatite (HA) and magnesium phosphate cement (MPC) with sodium pyrophosphate applied as a retardant of setting reaction was obtained. Its setting time was adequate for clinical applications. Combining properties of HA and MPC has made it possible to obtain microporous (showing bimodal pore size distribution in the range of 0.005-1.700 micrometers) potential implant material showing good surgical handiness and sufficient mechanical strength. Effectiveness of sodium pyrophosphate as a retardant of exothermic setting reaction of the new cement formulation was confirmed. After setting and hardening, the material consisted of hydroxyapatite and struvite as crystalline phases. Unreacted magnesium oxide was not detected. PMID:24215450

Pijocha, Dawid; Zima, Aneta; Paszkiewicz, Zofia; ?lósarczyk, Anna

2013-01-01

344

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

345

Diffusion Flame Synthesis of Hydroxyapatite Nanoparticles using Urea Assisted Precursor Solution  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) or (Ca10(PO4)6(OH)2 has been widely used in orthopedics and dental applications for human bone implant and teeth filler due to their biocompatibility and osteoconductive properties. Fine to nanoparticles of HA with appropriate stoichiometry and purity are preferred because they enhance densification and bioactive properties. Here, we reported the synthesis of hydroxyapatite particles in a diffusion flame reactor. LPG mainly consisting of butane and propane was used as fuel and compressed air was used as oxidizer and carrier gas. The effects of urea adding into precursor on morphology and crystallinity of the generated particles were investigated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe particles morphology and crystallinity, respectively. Purity of the generated particles was analyzed quantitatively from XRD pattern using Rietveld method. Spherical shape of particles morphology was obtained for particles synthesized without urea added into precursor. Increasing fuel flow rate and urea concentration led to further disintegration of the generated particles. Nano sized particles were generated using fuel flow rate of 1 L/min and 30 w% concentration of urea added into precursor. However, increasing urea concentration led to the increase of tricalcium phosphate as a further reaction of hydroxyapatite for flame generated by using LPG as fuel of 1 L/min.

Widiyastuti; Setiawan, Adhi; Setyawan, Heru; Kusdianto; Nurtono, Tantular; Nia, Suci Madha; Winardi, Sugeng

2011-12-01

346

Electrospun polyurethane/hydroxyapatite bioactive Scaffolds for bone tissue engineering: the role of solvent and hydroxyapatite particles.  

PubMed

Polyurethane (PU) is a promising polymer to support bone-matrix producing cells due to its durability and mechanical resistance. In this study two types of medical grade poly-ether urethanes Z3A1 and Z9A1 and PU-Hydroxyapatite (PU-HA) composites were investigated for their ability to act as a scaffold for tissue engineered bone. PU dissolved in varying concentrations of dimethylformamide (DMF) and tetrahydrofuran (THF) solvents were electrospun to attain scaffolds with randomly orientated non-woven fibres. Bioactive polymeric composite scaffolds were created using 15 wt% Z3A1 in a 70/30 DMF/THF PU solution and incorporating micro- or nano-sized HA particles in a ratio of 3:1 respectively, whilst a 25 wt% Z9A1 PU solution was doped in ratio of 5:1. Chemical properties of the resulting composites were evaluated by FTIR and physical properties by SEM. Tensile mechanical testing was carried out on all electrospun scaffolds. MLO-A5 osteoblastic mouse cells and human embryonic mesenchymal progenitor cells, hES-MPs were seeded on the scaffolds to test their biocompatibility and ability to support mineralised matrix production over a 28 day culture period. Cell viability was assayed by MTT and calcium and collagen deposition by Sirius red and alizarin red respectively. SEM images of both electrospun PU scaffolds and PU-HA composite scaffolds showed differences in fibre morphology with changes in solvent combinations and size of HA particles. Inclusion of THF eliminated the presence of beads in fibres that were present in scaffolds fabricated with 100% DMF solvent, and resulted in fibres with a more uniform morphology and thicker diameters. Mechanical testing demonstrated that the Young?s Modulus and yield strength was lower at higher THF concentrations. Inclusion of both sizes of HA particles in PU-HA solutions reinforced the scaffolds leading to higher mechanical properties, whilst FTIR characterisation confirmed the presence of HA in all composite scaffolds. Although all scaffolds supported proliferation of both cell types and deposition of calcified matrix, PU-HA composite fibres containing nano-HA enabled the highest cell viability and collagen deposition. These scaffolds have the potential to support bone matrix formation for bone tissue engineering. PMID:25117379

Tetteh, G; Khan, A S; Delaine-Smith, R M; Reilly, G C; Rehman, I U

2014-11-01

347

Detection of Hydroxyapatite in Calcified Cardiovascular Tissues  

PubMed Central

Objective The objective of this study is to develop a method for selective detection of the calcific (hydroxyapatite) component in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues ex vivo. This method uses a novel optical molecular imaging contrast dye, Cy-HABP-19, to target calcified cells and tissues. Methods A peptide that mimics the binding affinity of osteocalcin was used to label hydroxyapatite in vitro and ex vivo. Morphological changes in vascular smooth muscle cells were evaluated at an early stage of the mineralization process induced by extrinsic stimuli, osteogenic factors and a magnetic suspension cell culture. Hydroxyapatite components were detected in monolayers of these cells in the presence of osteogenic factors and a magnetic suspension environment. Results Atherosclerotic plaque contains multiple components including lipidic, fibrotic, thrombotic, and calcific materials. Using optical imaging and the Cy-HABP-19 molecular imaging probe, we demonstrated that hydroxyapatite components could be selectively distinguished from various calcium salts in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues, carotid endarterectomy samples and aortic valves, ex vivo. Conclusion Hydroxyapatite deposits in cardiovascular tissues were selectively detected in the early stage of the calcification process using our Cy-HABP-19 probe. This new probe makes it possible to study the earliest events associated with vascular hydroxyapatite deposition at the cellular and molecular levels. This target-selective molecular imaging probe approach holds high potential for revealing early pathophysiological changes, leading to progression, regression, or stabilization of cardiovascular diseases. PMID:22877867

Lee, Jae Sam; Morrisett, Joel D.; Tung, Ching-Hsuan

2012-01-01

348

In vitro effects of fluor-hydroxyapatite, fluorapatite and hydroxyapatite on colony formation, DNA damage and mutagenicity.  

PubMed

The number of biomaterials used in biomedical applications has rapidly increased in the past two decades. Fluorapatite (FA) is one of the inorganic constituents of bone or teeth used for hard-tissue repairs and replacements. Fluor-hydroxyapatite (FHA) is a new synthetically prepared composite that in its structure contains the same molecular concentration of OH(-) groups and F(-) ions. The aim of this experimental investigation was to evaluate cytotoxic, genotoxic and mutagenic effects of FHA and FA eluates on Chinese hamster V79 cells and to compare them with the effects of hydroxyapatite (HA) eluate. Cytotoxicity of the biomaterials tested was evaluated by use of the cell colony-formation assay and by direct counting of the cells in each colony. Genotoxicity was assessed by single-cell gel electrophoresis (comet assay) and mutagenicity was evaluated by the Hprt gene-mutation assay and in bacterial mutagenicity tests using Salmonella typhimurium TA100. The results show that the highest test concentrations of the biomaterials (100% and 75% eluates) induced very weak inhibition of colony growth (about 10%). On the other hand, the reduction of cell number per colony induced by these concentrations was in the range from 43% to 31%. The comet assay showed that biomaterials induced DNA breaks, which increased with increasing test concentrations in the order HA

Jantová, S; Theiszová, M; Letasiová, S; Birosová, L; Palou, T M

2008-04-30

349

Structural, microstructural, and residual stress investigations of plasma-sprayed hydroxyapatite on Ti-6Al-4 V.  

PubMed

Plasma-spray (PS) is a classical technique usually employed to cover orthopaedic titanium implant surfaces with hydroxyapatite (HA - Ca(10)(PO(4))(6)(OH)(2)). The objective of the current study is to investigate the structure and microstructure of HA plasma-spray 50 mum thick coating on titanium alloy (Ti-6Al-4 V) and residual stress due to processing in the substrate and in HA coating. The structure of the coatings was determined by high-energy synchrotron X-ray diffraction in energy dispersive (HESXRD), selected area electron diffraction (saed), Scanning Electron Microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). No impurity phases in the HA were identified by HESXRD to keep away from the decomposition of HA at high temperature. hcp phase of HA substrate was detected with slight amorphous background. FTIR spectrum of a HA powder shows a typical spectrum for HA material with the characteristic phosphate peaks for HA at wavenumbers of 1090, 1052, 963, 602, and 573 cm(-1) are present. The morphology of HA powder observed by SEM exhibits grains of ca. 0.1 mum well-adapted for cell proliferation. HA/Ti-6Al-4 V interface observed by cross-section scanning and transmission electron microscopy (TEM) presents microcracks. Residual stresses were analyzed by sin(2) Psi X-ray diffraction method on titanium substrates and HA coating. Although the Ti substrates are in a slightly tensile residual state, the coated ones show a compressive state. PMID:20356205

Carradó, Adele

2010-02-01

350

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. PMID:24574168

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

2014-10-01

351

Effect of aging temperature on formation of sol-gel derived fluor-hydroxyapatite nanoparticles.  

PubMed

Synthetic hydroxyapatite (HA) has been recognized as one of the most important bone substitute materials in orthopaedics and dentistry over past few decades because of its chemical and biological similarity to the mineral phase of human bone. One solution for reduction the solubility of HA in biological environments is replacing F- by OH in HA structure and forming fluor-hydroxyapatite (FHA) solid solution. In this paper, FHA nanoparticles were successfully synthesized by a sol-gel method. Also, the influence of aging temperature on formation of FHA powder was studied. Equimolar solutions of calcium nitrate tetrahydrate, triethyl phosphite and ammonium fluoride in ethanol were used as Ca, P and F precursors. After aging at different temperatures, the synthesized powders were heat treated at 550 degrees C. The powders were investigated with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), selected area electron diffraction pattern (SAED), energy dispersive analysis of X-ray (EDAX) and zetasizer measurement. The results of XRD proved the presence of fluorapatite (FA) and HA in all samples. In addition, the formation of FHA was confirmed by FT-IR results. XRD studies also showed that the crystallites were in nanometric scale. At the same time, this result was in good agreement with the result of zetasizer analysis. PMID:20355519

Joughehdoust, S; Behnamghader, A; Jahandideh, R; Manafi, S

2010-04-01

352

Injectable PLGA microsphere/calcium phosphate cements: physical properties and degradation characteristics.  

PubMed

Calcium phosphate (CaP) cements show an excellent biocompatibility and often have a high mechanical strength, but in general degrade relatively slow. To increase degradation rates, macropores can be introduced into the cement, e.g., by the inclusion of biodegradable microspheres into the cement. The aim of this research is to develop an injectable PLGA microsphere/CaP cement with sufficient setting/cohesive properties and good mechanical and physical properties. PLGA microspheres were prepared using a water-in-oil-in-water double-emulsion technique. The CaP-cement used was Calcibon, a commercially available hydroxyapatite-based cement. 10:90 and 20:80 dry wt% PLGA microsphere/CaP cylindrical scaffolds were prepared as well as microporous cement (reference material). Injectability, setting time, cohesive properties and porosity were determined. Also, a 12-week degradation study in PBS (37 degree C) was performed. Results showed that injectability decreased with an increase in PLGA microsphere content. Initial and final setting time of the PLGA/CaP samples was higher than the microporous sample. Porosity of the different formulations was 40.8% (microporous), 60.2% (10:90) and 69.3% (20:80). The degradation study showed distinct mass loss and a pH decrease of the surrounding medium starting from week 6 with the 10:90 and 20:80 formulations, indicating PLGA erosion. Compression strength of the PLGA microsphere/CaP samples decreased siginificantly in time, the microporous sample remained constant. After 12 weeks both PLGA/CaP samples showed a structure of spherical micropores and had a compressive strength of 12.2 MPa (10:90) and 4.3 MPa (20:80). Signs of cement degradation were also found with the 20:80 formulation. In conclusion, all physical parameters were well within workable ranges with both 10:90 and 20:80 PLGA microsphere/CaP cements. After 12 weeks the PLGA was totally degraded and a highly porous, but strong scaffold remained. PMID:17094642

Habraken, W J E M; Wolke, J G C; Mikos, A G; Jansen, J A

2006-01-01

353

Osteopontin, osteocalcin and OB-cadherin expression in Synthetic nanohydroxyapatite vs bovine hydroxyapatite cultured Osteoblastic-like cells.  

PubMed

Calcium phosphate ceramics have been applied in bone replacement for several decades due to their excellent biocompatibility, bioactivity, osteo-conductivity and mechanical strength. Several studies have demonstrated that porous hydroxyapatite (HA) is an excellent scaffold for osteogenic proliferation and differentiation of the osteoprogenitor cells. However, different methods of synthesis and production of HA ceramic-based materials may have considerable effect on the physical and biological properties. In the present work, two hydroxyapatite-based materials, a natural hydroxyapatite ceramic of bovine origin and a synthetic nano-cristalline hydroxyapatite were tested in vitro with MG63 cell line. The results displayed that both the materials demonstrated a good biocompatibility. The immunocytochemical stain revealed a different positivity of the osteogenic markers between the cultures with the biomaterials, and the control culture. Western blot data confirmed the immunocytochemical stain. Both the materials tested in the present study demonstrated a good biocompatibility with the osteoblastic cells allowing, at the same time, the osteogenic differentiation, and they may be useful in clinical use. PMID:25316140

Santarelli, A; Mascitti, M; Orsini, G; Memè, L; Rocchetti, R; Tiriduzzi, P; Sampalmieri, F; Putignano, A; Procaccini, M; Lo Muzio, L; Bambini, F

2014-01-01

354

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. PMID:24639083

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

2015-01-01

355

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

356

Magnetic Hydroxyapatite Bone Substitutes to Enhance Tissue Regeneration: Evaluation In Vitro Using Osteoblast-Like Cells and In Vivo in a Bone Defect  

Microsoft Academic Search

In case of degenerative disease or lesion, bone tissue replacement and regeneration is an important clinical goal. In particular, nowadays, critical size defects rely on the engineering of scaffolds that are 3D structural supports, allowing cellular infiltration and subsequent integration with the native tissue. Several ceramic hydroxyapatite (HA) scaffolds with high porosity and good osteointegration have been developed in the

Silvia Panseri; Carla Cunha; Teresa DAlessandro; Monica Sandri; Alessandro Russo; Gianluca Giavaresi; Maurilio Marcacci; Clark T. Hung; Anna Tampieri

2012-01-01

357

Preparation and characterization of biodegradable chitosan\\/hydroxyapatite nanocomposite rods via in situ hybridization: a potential material as internal fixation of bone fracture  

Microsoft Academic Search

A transparent and slight yellow chitosan (CS)\\/hydroxyapatite (HA) nanocomposite with high performed, potential application as internal fixation of bone fracture was prepared by a novel and simple in situ hybridization. The method solves the problem of the nano-sized particle aggregation in polymer matrix. XRD, TEM and SEM were used to determine component and morphology of the composite. Results indicated that

Qiaoling Hu; Baoqiang Li; Mang Wang; Jiacong Shen

2004-01-01

358

The influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites.  

PubMed

This study investigates the influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites. Three different silanes (mercaptopropyl trimethoxy silane (MPTMS), aminopropyl trimethoxy silane (APTMS) and aminopropyltriethoxy silane (APTES)) were applied to HA substrates in order to study the effect of head group (which binds to the polymer) and tail group (which binds to the surface hydroxyl groups in HA). A composite of hydroxyapatite (HA) and poly(d,l lactide-co-glycolide (50:50)) (PLGA) was investigated. The influence of concentration, the reaction time, drying temperature and substrate surface on silanisation was examined. TGA was used to detect the degree of silanisation. HA with MPTMS (1wt.% MPTMS with reaction time of 1h) was used as filler in PLGA-30wt.% HA composites for an in-vitro degradation study carried out in PBS. In addition, the mechanical properties of the composites were studied. Silanisation affects the properties of the composite by improving the bonding at the interface and hence it was found to influence the plastic mechanical properties rather than the elastic mechanical properties or the degradation profile of the composite. PMID:25579967

Naik, Ashutosh; Best, Serena M; Cameron, Ruth E

2015-03-01

359

Resonant ultrasound spectroscopy measurement of Young's modulus, shear modulus and Poisson's ratio as a function of porosity for alumina and hydroxyapatite  

Microsoft Academic Search

Modulus–porosity relationships are critical for engineered bone tissue scaffold materials such as hydroxyapatite (HA), where porosity is essential to biological function. Resonant ultrasound spectroscopy (RUS) measurements revealed that the Young's modulus, E, and shear modulus, G, of both alumina and HA decrease monotonically with increasing volume fraction porosity, P, for 0.06 < P < 0.39 (alumina) and 0.05 < P

F. Ren; E. D. Case; A. Morrison; M. Tafesse; M. J. Baumann

2009-01-01

360

POROUS WALL, HOLLOW GLASS MICROSPHERES  

Microsoft Academic Search

Hollow Glass Microspheres (HGM) is not a new technology. All one has to do is go to the internet and Google{trademark} HGM. Anyone can buy HGM and they have a wide variety of uses. HGM are usually between 1 to 100 microns in diameter, although their size can range from 100 nanometers to 5 millimeters in diameter. HGM are used

2012-01-01

361

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

362

SRNL POROUS WALL GLASS MICROSPHERES  

Microsoft Academic Search

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

G Wicks; L Leung Heung; R Ray Schumacher

2008-01-01

363

The importance of amino acid interactions in the crystallization of hydroxyapatite  

PubMed Central

Non-collagenous proteins (NCPs) inhibit hydroxyapatite (HA; Ca5(PO4)3OH) formation in living organisms by binding to nascent nuclei of HA and preventing their further growth. Polar and charged amino acids (AAs) are highly expressed in NCPs, and the negatively charged ones, such as glutamic acid (Glu) and phosphoserine (P-Ser) seem to be mainly responsible for the inhibitory effect of NCPs. Despite the recognized importance of these AAs on the behaviour of NCPs, their specific effect on HA crystallization is still unclear, and controversial results have been reported concerning the efficacy of HA inhibition of positively versus negatively charged AAs. We focused on a positively charged (arginine, Arg) and a negatively charged (Glu) AA, and their combination in the same solution. We studied their inhibitory effect on HA nucleation and growth at physiological temperature and pH and we determined the mechanism by which they can affect HA crystallization. Our results showed a strong inhibitory effect of Arg on HA nucleation; however, Glu was more effective in inhibiting HA crystal growth during the growth stage. The combination of Glu and Arg was less effective in controlling HA nucleation, but it inhibited HA crystal growth. We attributed these differences to the stability of complexes formed between AAs and calcium and phosphate ions at the nucleation stage, and in bonding strength of AAs to HA crystal faces during the growth stage. The AAs also influenced the morphology of synthesized HA. Presence of either Arg or Glu resulted in the formation of spherulites consisting of preferentially oriented nanoplatelets orientation. This was attributed to kinetic factors favoring growth front nucleation (GFN) mechanism. PMID:23269851

Jahromi, M. Tavafoghi; Yao, G.; Cerruti, M.

2013-01-01

364

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

365

Microspheres and nanoparticles from ultrasound  

NASA Astrophysics Data System (ADS)

Improved preparations of various examples of monodispersed, porous, hollow, and core-shell metal and semiconductor nanoparticles or nanowires have been developed. Now titania microspheres and nanoparticles and silica microspheres can be synthesized using an inexpensive high frequency (1.7 MHz) ultrasonic generator (household humidifier; ultrasonic spray pyrolysis; USP). Morphology and pore size of titania microspheres were controlled by the silica to Ti(IV) ratio and silica particle size. Fine tuning the precursor ratio affords sub-50 nm titania nanoparticles as well. In terms of silica microspheres, morphology was controlled by the silica to organic monomer ratio. In liquids irradiated with high intensity ultrasound (20 kHz; HIUS), acoustic cavitation produces high energy chemistry through intense local heating inside the gas phase of collapsing bubbles in the liquid. HIUS and USP confine the chemical reactions to isolated sub-micron reaction zones, but sonochemistry does so in a heated gas phase within a liquid, while USP uses a hot liquid droplet carried by a gas flow. Thus, USP can be viewed as a method of phase-separated synthesis using submicron-sized droplets as isolated chemical reactors for nanomaterial synthesis. While USP has been used to create both titania and silica spheres separately, there are no prior reports of titania-silica composites. Such nanocomposites of metal oxides have been produced, and by further manipulation, various porous structures with fascinating morphologies were generated. Briefly, a precursor solution was nebulized using a commercially available household ultrasonic humidifier (1.7 MHz ultrasound generator), and the resulting mist was carried in a gas stream of air through a quartz glass tube in a hot furnace. After exiting the hot zone, these microspheres are porous or hollow and in certain cases magnetically responsive. In the case of titania microspheres, they are rapidly taken up into the cytoplasm of mammalian cells and nearly noncytoxic. Small molecules like Rhodamine and DHED (dehydroevodiamine HCl; Alzheimer's disease therapeutic) can be delivered along with them. Furthermore, synthesis of carbon nanoparticles and titanate nanotube species are possible utilizing these microspheres. Characterizations were done by SEM, (S)TEM, optical/confocal microscopy, XRD, XPS, EDS, SAED, zeta potential, and BET.

Suh, Won Hyuk

366

Preparation and Characterization of Microspheres of Albumin-Heparin Conjugates  

E-print Network

Preparation and Characterization of Microspheres of Albumin-Heparin Conjugates GLEN S. KWON,* YOU-heparinconjugatewascrosslinkedin a water-in-oilemulsionto formalbumin- heparin microspheres.The compositionofthe conjugatewas determinedby-heparin microspheres.Surfacesofalbumin-heparin and albumin microsphereswerecharacterizedby ESCA

Twente, Universiteit

367

Composite Tectocapsules Containing Porous Polymer Microspheres as Release Gates  

E-print Network

Composite Tectocapsules Containing Porous Polymer Microspheres as Release Gates Lisa M. Croll: Porous and amphiphilic polymer microspheres were incorporated into polyurea capsules in order to control) microspheres were simply encapsulated along with the xylene core solvent, the amphiphilic poly

Hitchcock, Adam P.

368

21 CFR 522.1451 - Moxidectin microspheres for injection.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Moxidectin microspheres for injection. 522.1451 Section...ANIMAL DRUGS § 522.1451 Moxidectin microspheres for injection. (a) Specifications...One contains 10 percent moxidectin microspheres, and the other contains a...

2014-04-01

369

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 their electrostatic interactions, both the initial microsphere stability and the role of nanoparticle additions

Lewis, Jennifer

370

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

371

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

372

Effect of Hydroxyapatite porous characteristics on healing outcomes in rabbit posterolateral spinal fusion model.  

PubMed

Hydroxyapatite (HA) has been commonly used as a bone graft substitute in various kinds of clinical fields. To improve the healing capability of HA, many studies have been performed to reveal its optimal structural characteristics for better healing outcomes. In spinal reconstruction surgery, non-interconnected porous HAs have already been applied as a bone graft extender in order to avoid autogenous bone harvesting. However, there have been few experimental studies regarding the effects of the structural characteristics of HA in posterolateral lumbar intertransverse process spine fusion (PLF). The aims of this study were to investigate the effect of HA porous characteristics on healing outcomes in a rabbit PLF model in order to elucidate appropriate structural characteristics of HA as a bone graft extender. Thirty-six adult female Japanese White rabbits underwent bilateral intertransverse process fusion at the level of L5-6 without internal fixation. We prepared three types of HA with different porosities: HA with 15% porosity (HA15%), HA with 50% porosity (HA50%), and HA with 85% porosity (HA85%), all of which were clinically available materials. The HA15% and HA50% had few interconnecting pores, whereas the HA85%, which was a recently developed material, had abundant interconnecting pores. All rabbits were randomly divided into the following four groups according to the grafted materials: (1) HA15% + autogenous bone, (2) HA50% + autogenous bone, (3) HA85% + autogenous bone, (4) pure autogenous bone graft. The animals were euthanized at 5 weeks after surgery, and post-mortem analyses including biomechanical testing, radiographical and histological evaluations were performed. There was no statistically significant difference in either fusion rate and/or bending stiffness among the three HA groups. However, in histological and radiological analyses, both bone ingrowth rate and direct bone bonding rate in the HA85% group were significantly higher than those in the HA15% and HA50% groups, despite the similar value of bone volume rate in fusion mass among the three HA groups. In the HA85% group, bone ingrowth was achieved throughout the implanted HAs via interconnecting pores and there was excellent unification between the HA granules and the newly mineralized bone. On the other hand, in the non-interconnected porous HA groups, only a little bone ingrowth could be seen at the peripheral pores of the implanted HA, and its surface was mostly covered with fibrous tissue or empty space. The current study demonstrated that the HA porous characteristics had an effect on the histological outcomes in a rabbit PLF model. We would like to conclude that the interconnected high porous structure seems to be promising for the environment of PLF in the point of producing fusion mass with higher cellular viability. This is because the HA85% is superior in terms of integration with the newly formed bone in fusion mass compared to the non-interconnected porous HAs. However, the porous modifications of HA have little influence on fusion rate and mechanical strength because primary stabilization of the fusion segment is mainly achieved by bridging bone between the adjacent transverse processes outside the implanted materials, rather than the degree of integration between the newly formed bone and the HA granules in PLF. PMID:17891422

Motomiya, Makoto; Ito, Manabu; Takahata, Masahiko; Kadoya, Ken; Irie, Kazuharu; Abumi, Kuniyoshi; Minami, Akio

2007-12-01

373

Influence of fluorapatite minor additions on behavior of hydroxyapatite ceramics  

Microsoft Academic Search

Fluorinated hydroxyapatite is known to be less soluble by body fluids, resulting in enhanced resistance to biodegradation in vivo conditions, as compared to the pure hydroxyapatite ceramics. The present work was aimed at the investigation of the effect of minor additions of ultrafine fluorapatite (up to 10 wt %) on the sintering behavior and mechanical properties of hydroxyapatite ceramics. In

S. M. Barinov; F. Rustichelli; V. P. Orlovskii; A. Lodini; S. Oscarsson; S. A. Firstov; S. V. Tumanov; P. Millet; å. Rosengren

2004-01-01

374

Control of cellular activity of fibroblasts on size-tuned fibrous hydroxyapatite nanocrystals.  

PubMed

We controlled the performance of L929 mouse fibroblasts using various hydroxyapatite (HA) nanocrystals, such as nanofibers, nanoneedles, and nanosheets, to better understand the effects of size and shape of the HA nanocrystals on the cells. The cellular activity on nanofibers with a diameter of 50-100 nm was significantly enhanced relative to that on a flat HA surface because large amounts of the proteins needed for adhesion and proliferation could be stored in the substrate. On the other hand, initial adhesion and subsequent proliferation were inhibited on surfaces consisting of fine nanoneedles and nanosheets with a diameter/thickness of less than 30 nm due to the limited area available for the formation of focal adhesions. These facts indicate that fibroblast activity is highly sensitive to the surface topography. Therefore, size tuning of the nanoscale units composing the substrate is essential to enhance cellular performance. PMID:20965284

Okada, Shinnosuke; Nagai, Atsushi; Oaki, Yuya; Komotori, Jun; Imai, Hiroaki

2011-03-01

375

Long-term in vivo experimental investigations on magnesium doped hydroxyapatite bone substitutes.  

PubMed

Despite several efforts to find suitable alternatives to autologous bone, no bone substitute currently available provides the same characteristics and properties. Nevertheless, among the wide range of materials proposed as bone substitutes, calcium phosphate materials represent the most promising category and the present study is aimed at improving the knowledge on non-stoichiometric magnesium-doped hydroxyapatite substitutes (Mg-HA), tested in two different formulations: Mg-HA Putty and Mg-HA Granules. These bone substitutes were implanted bilaterally into iliac crest bone defects in healthy sheep and comparative histological, histomorphometric, microhardness and ultrastructural assessments were performed 9, 12, 18 and 24 months after surgery to elucidate bone tissue apposition, mineralization and material degradation in vivo. The results confirmed that the biomimetic bone substitutes provide a histocompatible and osteoconductive structural support, during the bone formation process, and give essential information about the in vivo resorption process and biological behavior of biomimetic bone substitutes. PMID:24554305

Sartori, M; Giavaresi, G; Tschon, M; Martini, L; Dolcini, L; Fiorini, M; Pressato, D; Fini, M

2014-06-01

376

Surface phenomena of HA\\/TiN coatings on the nanotubular-structured beta Ti–29Nb–5Zr alloy for biomaterials  

Microsoft Academic Search

Surface phenomena of HA\\/TiN coatings on the nanotubular-structured beta Ti–29Nb–5Zr alloy for biomaterials have been investigated by several experimental methods. The nanotubular structure was formed by anodizing the Ti–29Nb–5Zr alloy in 1M H3PO4 electrolytes with 1.0wt.% NaF at room temperature. Hydroxyapatite (HA)\\/titanium nitride (TiN) films were deposited on Ti–29Nb–5Zr alloy specimens using a magnetron sputtering system. The HA target was

Eun-Ju Kim; Yong-Hoon Jeong; Han-Cheol Choe; William A. Brantley

377

Triphasic ceramic coated hydroxyapatite as a niche for goat stem cell-derived osteoblasts for bone regeneration and repair  

Microsoft Academic Search

Current treatment strategies for the repair or replacement of bone use synthetic implants with stem cells and their progeny––a\\u000a new approach to address unmet medical needs. This study has evaluated the effect of a silica-coated bioactive ceramic, namely\\u000a HASi in comparison to hydroxyapatite (HA) on the adhesion, proliferation and osteogenic differentiation of goat bone marrow-derived\\u000a mesenchymal stem cells in vitro in

Manitha B. Nair; H. K. Varma; Annie John

2009-01-01

378

A 5-year comparison of hydroxyapatite-coated titanium plasma–sprayed and titanium plasma–sprayed cylinder dental implants  

Microsoft Academic Search

Objective. A preliminary report from this study showed that hydroxyapatite-coated (HA) titanium plasma–sprayed (TPS) cylinder implants had fewer failures than TPS cylinder implants before prosthetic loading. The purpose of this article is to report the long-term success associated with the 2 systems. In addition, local and systemic factors that may influence the success or failure of the implants were analyzed.

John D. Jones; John Lupori; Joseph E. Van Sickels; Wayne Gardner

1999-01-01

379

Growth of hydroxyapatite nanoparticles on silica gels.  

PubMed

Synthetic, hydroxyapatite nanoparticles were grown on the surface of silica gels. The synthesis of those nanoparticles was obtained by immersing silica gels in a simulated body fluid (SBF) at 37 degrees C. The SBF was replaced every week to keep constant the Ca and P ion concentration and subsequent growth of hydroxyapatite was evaluated after 1-6 weeks of total soaking time in SBF. Hydroxyapatite nanoparticles were observed by scanning electron microscopy (SEM) on the surface of silica gel samples and confirmed by energy dispersive X-ray spectroscopy (EDS), Fourier Transform Infra Red Spectroscopy (FTIR) and powder X-ray Diffractometry (XRD) analysis. These particles show a regular shape and uniform size every week, keeping within the nanoscale always. Both the size and morphology of hydroxyapatite nanoparticles obtained are the result of the use of different chemical additives in the synthesis of silica gels, since they affect the liquid-to-solid interface, and the growth could correspond to a diffusion limited aggregation (DLA) process. A more detailed analysis, with higher magnifications, showed that hydroxyapatite nanoparticles are not solid spheres, showing a branched texture and their size depends on the scale and resolution of the measure instrument. PMID:21770224

Rivera-Muñoz, E M; Huirache-Acuña, R; Velázquez, R; Alonso-Núñez, G; Eguía-Eguía, S

2011-06-01

380

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

381

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

382

Filling Porous Microspheres With Magnetic Material  

NASA Technical Reports Server (NTRS)

New process produces magnetic microspheres with controllable sizes, compositions, and properties for use in medical diagnostic tests, biological research, and chemical processes. Paramagnetic microspheres also made with process. Porous plastic microspheres prepared by polymerization of monomer in diluent by cross-linking agent. When diluent removed, it leaves tiny pores throughout polymerized spheres. Size and distribution of pores determined by amount and type of diluent and cross-linking agent.

Chang, Manchium; Colvin, Michael S.

1990-01-01

383

Micro-spherical probes machining by EDM  

Microsoft Academic Search

This paper describes a new hybrid micro-machining method, which combines wire electro discharge grinding technology with one pulse electro discharge, to fabricate micro-spherical probes and micro-spherical cavities. The results show that a burnished micro-spherical probe with about 40 µm diameter could be formed instantaneously with the hybrid machining process, which is not available in the conventional micro-machining method. The deviation

Dong-Yea Sheu

2005-01-01

384

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

385

Fabrication of porous hollow glass microspheres  

Microsoft Academic Search

Porous hollow glass microspheres have many uses, including porosity enhancers for lead-acid batteries. A fast, facile and high yield synthetic method for fabricating porous hollow glass microspheres with diameters around 45–55?m is demonstrated. The process involves shaking commercially available hollow glass microspheres in dilute hydrofluoric acid for 20min. This process yielded two pore morphologies by using different commercially available starting

Yuqun Xie; Simon D. McAllister; Dean B. Edwards; I. Francis Cheng

2011-01-01

386

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

387

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

388

Biomimetic Collagen–Hydroxyapatite Composite Fabricated via a Novel Perfusion-Flow Mineralization Technique  

PubMed Central

Prevalent three-dimensional scaffolds for bone tissue engineering are mineralized collagen–hydroxyapatite (Col/HA) composites. Conventional mineralization techniques are either to coat collagen scaffold surfaces with minerals or to simply mix collagen and mineral nanoparticles together. These conventional in vitro collagen mineralization methods are different from the in vivo bone formation process and often result in scaffolds that are not suitable for bone tissue engineering. In this study, a unique perfusion-flow (i.e., dynamic) in conjunction with a previously described polymer-induced liquid-precursor (PILP) method was used to fabricate a porous Col/HA composite. The dynamic flow emulated the physiological extracellular fluid flow containing the mineralization ions, while the PILP method facilitated the deposition of the HA crystals within the collagen fibrils (i.e., intrafibrillar mineralization). By utilizing a dynamic PILP technique to mimic the in vivo bone formation process, the resultant Col/HA composite has a similar structure and compositions like human trabecular bone. A comparison of the dynamic and static mineralization methods revealed that the novel dynamic technique facilitates more efficient and homogenous mineral deposition throughout the Col/HA composite. The dynamic intrafibrillar mineralization method generated stiff Col/HA composites with excellent surface property for cell attachment and growth. The human mesenchymal stem cells cultured on the Col/HA composites quickly remodeled the scaffolds and resulted in constructs with an extensive cell-derived extracellular matrix network. PMID:23157544

Antebi, Ben; Cheng, Xingguo; Harris, Jeffrey N.; Gower, Laurie B.; Chen, Xiao-Dong

2013-01-01

389

The effect of adding hydroxyapatite on the flexural strength of glass ionomer cement.  

PubMed

This present study investigated the effects of the addition of hydroxyapatite (HA) on the flexural strength and microstructure of conventional GIC, and its effect on the cement's initial flexural strength at different storage conditions. Specimens were fabricated by mixing HA in whisker or granule form into commercially prepared GIC, and these were subjected to a three-point bending test and SEM observations. Some specimens were stored in different conditions from dry to wet for 15 minutes to an hour prior to testing. When compared to the control, specimens with 16-25% HA whiskers added at P/L 1.75 showed a significant increase in the flexural strength (p < 0.05), and as well with 19% HA whiskers at P/L 1.75 (p < 0.001) and 2.33 (p < 0.05). A significant increase was also noted for those with 8-25% HA granules added at P/L's 1.75 (p < 0.05), 2.5 (p < 0.05) and 3.60 (p < 0.01). The addition of HA hastens the development of early (15 min, 1 hour) flexural strength of GIC in moist or wet conditions. These results indicate that the addition of HA, regardless of form, improve the flexural and microstructural properties of GIC. PMID:12873116

Arita, Kenji; Lucas, Milanita E; Nishino, Mizuho

2003-06-01

390

The differential regulation of osteoblast and osteoclast activity by surface topography of hydroxyapatite coatings.  

PubMed

The behavior of bone cells is influenced by the surface chemistry and topography of implants and scaffolds. Our purpose was to investigate how the topography of biomimetic hydroxyapatite (HA) coatings influences the attachment and differentiation of osteoblasts, and the resorptive activity of osteoclasts. Using strategies reported previously, we directly controlled the surface topography of HA coatings on polycaprolactone discs. Osteoblasts and osteoclasts were incubated on HA coatings having distinct isotropic topographies with submicrometer and micro-scale features. Osteoblast attachment and differentiation were greater on more complex, micro-rough HA surfaces (Ra ~2 ?m) than on smoother topographies (Ra ~1 ?m). In contrast, activity of the osteoclast marker tartrate-resistant acid phosphatase was greater on smoother than on micro-rough surfaces. Furthermore, scanning electron microscopy revealed the presence of resorption lacunae exclusively on smoother HA coatings. Inhibition of resorption on micro-rough surfaces was associated with disruption of filamentous actin sealing zones. In conclusion, HA coatings can be prepared with distinct topographies, which differentially regulate responses of osteoblasts, as well as osteoclastic activity and hence susceptibility to resorption. Thus, it may be possible to design HA coatings that induce optimal rates of bone formation and degradation specifically tailored for different applications in orthopedics and dentistry. PMID:23830579

Costa, Daniel O; Prowse, Paul D H; Chrones, Tom; Sims, Stephen M; Hamilton, Douglas W; Rizkalla, Amin S; Dixon, S Jeffrey

2013-10-01

391

Effect of nano-hydroxyapatite on the axonal guidance growth of rat cortical neurons  

NASA Astrophysics Data System (ADS)

Nanomaterials such as carbon nanotubes (CNT) can improve axonal connecting in a target direction during regeneration, however, it is limited by the neurotoxicity of CNT. Here we investigate the possible protective effect of nano-hydroxyapatite (n-HA) against nerve injury, as well as CNT in cultured rat cortical neurons. In this study the nanomaterials were characterized by X-Ray diffractometry (XRD) and atomic force microscopy (AFM) analysis. Our results showed that axonal migration and extension were increased significantly after n-HA treatment by immunocytochemistry assay. The patch clamp assay results showed that n-HA acts protectively after nerve injury, which inhibited the average amplitude and frequency of excitatory postsynaptic currents (EPSCs). n-HA is not neurotoxic for the electrophysiology activity of cells. To find the effect of n-HA on axonal guidance growth in the cultured cortical neurons, Netrin 1, one of the axonal guidance cues, was determined by RT-PCR and western blot assay. Compared to the control group, n-HA down-regulated the mRNA level of netrin 1, and moreover, the expression of netrin 1 decreased significantly in the cells. n-HA caused the axonal guidance growth to be mediated by netrin 1 during nerve regeneration. Therefore, the data from the present study provided a new approach for the therapy or prevention of nerve injury.

Liu, Meili; Zhou, Gang; Song, Wei; Li, Ping; Liu, Haifeng; Niu, Xufeng; Fan, Yubo

2012-05-01

392

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

393

Gene expression profile study on osteoinductive effect of natural hydroxyapatite.  

PubMed

The aim of this study was to investigate the osteoinductive effect of natural hydroxyapatite (NHA). NHA was extracted from pig bones and prepared into disk-like samples. Then, proliferation of mouse bone mesenchymal stem cells (MSCs) cultured on NHA was assessed by the methylthiazoltetrazolium (MTT) assay. Furthermore, microarray technology was applied to obtain the gene expression profiles of MSCs cultured on NHA at 24, 48, and 72 h. The gene expression profile was then comprehensively analyzed by clustering, Gene Ontology (GO), Gene Microarray Pathway Profiler (GenMAPP) and Ingenuity Pathway Analysis (IPA). According to the results of microarray experiment, 8992 differentially expressed genes were obtained. 90 differential expressed genes related to HA osteogenic differentiation were determined by GO analysis. These genes included not only 6 genes related to HA osteogenic differentiation as mentioned in the literatures but also newly discovered 84 genes. Some important signaling pathways (TGF-?, MAPK, Wnt, etc.) were influenced by these genes. Gene interaction networks were obtained by IPA software, in which the scoring values of two networks were highest, and their main functions were related to cell development. The comprehensive analysis of these results indicate that NHA regulate some crucial genes (e.g., Bmp2, Spp1) and then activate some pathways such as TGF-? signaling pathway, and ultimately osteogenic differentiation was induced. PMID:24115491

Lü, Xiaoying; Wang, Jiandan; Li, Bin; Zhang, Zhiwei; Zhao, Lifeng

2014-08-01

394

Strategies for microsphere-mediated cellular delivery   

E-print Network

Amino-functionalised polystyrene microspheres are promising candidates as delivery systems due to their unique features, tunable surface functionalities, and controllable release of the cargo. Herein several strategies ...

Cardenas-Maestre, Juan Manuel

2011-11-23

395

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

396

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

397

A Rheological Study of Biodegradable Injectable PEGMC/HA Composite Scaffolds.  

PubMed

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

2012-01-01

398

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

399

Second derivative infrared spectra of hydroxyapatite  

NASA Astrophysics Data System (ADS)

Infrared absorption spectra of polycrystalline fluor- and hydroxyapatite are transformed to their second derivatives for resolution enhancement. It is observed that although the symmetry of the hydroxyapatite lattice is lower than that of fluorapatite, the spectra are nearly congruent. The data of polycrystalline samples are analysed on the basis of single crystal Raman and infrared dichroism spectra. The number of vibrational bands that are observed in the spectra of polycrystalline fluor- and hydroxyapatite exceed the number predicted by factor group analysis. The "excess" bands are assigned to vibrations that are expected to be Raman active previously reported in the single crystal Raman data of these two minerals. This can be accounted for by a breakdown of factor group selection rules as applied to the infrared data of polycrystalline apatites.

Leung, Yiuchong; Walters, M. Anton; LeGeros, Racquel Z.

400

Finite Element Simulation of Diametral Strength Test of Hydroxyapatite  

SciTech Connect

In this study, the diametral strength test of sintered hydroxyapatite was simulated by the finite element software, ABAQUS/Standard. Stress distributions on diametral test sample were determined. The effect of sintering temperature on stress distribution of hydroxyapatite was studied. It was concluded that high sintering temperatures did not reduce the stress on hydroxyapatite. It had a negative effect on stress distribution of hydroxyapatite after 1300 deg. C. In addition to the porosity, other factors (sintering temperature, presence of phases and the degree of crystallinity) affect the diametral strength of the hydroxyapatite.

Ozturk, Fahrettin; Toros, Serkan [Nigde University, Department of Mechanical Engineering, Nigde, 51245 (Turkey); Evis, Zafer [Middle East Technical University, Department of Engineering Sciences, Ankara, 06531 (Turkey)

2011-01-17

401

Sol-Gel Derived Hydroxyapatite Coating on Mg-3Zn Alloy for Orthopedic Application  

NASA Astrophysics Data System (ADS)

In recent years, magnesium and its alloys have gained a lot of interest as orthopedic implant constituents because their biodegradability and mechanical properties are closer to that of human bone. However, one major concern with Mg in orthopedics is its high corrosion rate that results in the reduction of mechanical integrity before healing the bone tissue. The current study evaluates the sol-gel-derived hydroxyapatite (HA) coating on a selected Mg alloy (Mg-3Zn) for decreasing the corrosion rate and increasing the bioactivity of the Mg surface. The mechanical integrity of the coating is established as a function of the surface roughness of the substrate and the sintering temperature of the coating. Coating on a substrate roughness of 15-20 nm and sintering at 400°C shows the mechanical properties in similar range of bone, thus making it suitable to avoid the stress-shielding effect. The hydroxyapatite coating on the Mg alloy surface also increases corrosion resistance very significantly by 40 times. Bone cells are also found proliferating better in the HA-coated surface. All these benefits together establish the candidature of sol-gel HA-coated Mg-3Zn alloy in orthopedic application.

Singh, Sanjay; Manoj Kumar, R.; Kuntal, Kishor Kumar; Gupta, Pallavi; Das, Snehashish; Jayaganthan, R.; Roy, Partha; Lahiri, Debrupa

2015-03-01

402

A combined chitosan/nano-size hydroxyapatite system for the controlled release of icariin.  

PubMed

Icariin, a plant-derived flavonol glycoside, has been proved as an osteoinductive agent for bone regeneration. For this reason, we developed an icariin-loaded chitosan/nano-sized hydroxyapatite (IC-CS/HA) system which controls the release kinetics of icariin to enhance bone repairing. First, by Fourier transform infrared spectroscopy, we found that icariin was stable in the system developed without undergoing any chemical changes. On the other hand, X-ray diffraction, scanning electron microscopy and mechanical test revealed that the introduction of icariin did not remarkably change the phase, morphology, porosity and mechanical strength of the CS/HA composite. Then the hydrolytic degradation and drug release kinetics in vitro were investigated by incubation in phosphate buffered saline solution. The results indicated that the icariin was released in a temporally controlled manner and the release kinetics could be governed by degradation of both chitosan and hydroxyapatite matrix. Finally the in vitro bioactivity assay revealed that the loaded icariin was biologically active as evidenced by stimulation of bone marrow derived stroma cell alkaline phosphatase activity and formation of mineralized nodules. This successful IC-CS/HA system offers a new delivery method of osteoinductive agents and a useful scaffold design for bone regeneration. PMID:22083857

Fan, Junjun; Bi, Long; Wu, Tao; Cao, Liangguo; Wang, Dexin; Nan, Kaihui; Chen, Jingdi; Jin, Dan; Jiang, Shan; Pei, Guoxian

2012-02-01

403

Compression molding of aerogel microspheres  

DOEpatents

An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50-800 kg/m.sup.3 (0.05-0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization.

Pekala, Richard W. (Pleasant Hill, CA); Hrubesh, Lawrence W. (Pleasanton, CA)

1998-03-24

404

Compression molding of aerogel microspheres  

DOEpatents

An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner is disclosed. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50--800 kg/m{sup 3} (0.05--0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization. 4 figs.

Pekala, R.W.; Hrubesh, L.W.

1998-03-24

405

Osteogenesis of bone marrow mesenchymal stem cells on strontium-substituted nano-hydroxyapatite coated roughened titanium surfaces  

PubMed Central

Objective: To investigate osteogenesis of bone marrow mesenchymal stem cells (BMSCs) on strontium-substituted nano-hydroxyapatite (Sr-HA) coated roughened titanium surfaces. Methods: Sr-HA coating and HA coating were fabricated on roughened titanium surfaces by electrochemical deposition technique and characterized by field emission scanning electron microscope (FESM). BMSCs were cultured on Sr-HA coating, HA coating and roughened titanium surfaces respectively. Cell proliferation, alkaline phosphatase (ALP) activity, mineralized nodules formation and cell osteocalcin (OC) secretion were measured. Results: Electrochemically deposited Sr-HA coating and HA coating had no effect on the proliferation of BMSCs and demonstrated that the materials have a good biocompatibility. BMSCs cultured on Sr-HA coating showed increased alkaline phosphatase activity, mineralized nodules formation, and cell OC secretion compared with the other two groups. Cells cultured on HA coating also showed increased biological activity compared with the roughened group. Conclusion: Sr-HA coated titanium surfaces by electrochemical deposition can promote osteogenesis of BMSCs in vitro and have the potential to shorten bone healing period and enhance implant osseointegration.

Yang, Hua-Wei; Lin, Mao-Han; Xu, Yuan-Zhi; Shang, Guang-Wei; Wang, Rao-Rao; Chen, Kai

2015-01-01

406

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

407

Nonaggregating Microspheres Containing Aldehyde Groups  

NASA Technical Reports Server (NTRS)

Cobalt gamma irradiation of hydrophilic monomers in presence of acrolein yields exceptionally-stable, nonaggregating microspheres. Mixtures of 2-hydroxyethyl methacrylate (HEMA) and acrolein form homogeneous solutions in distilled water containing 0.4 percent polyethylene oxide (PEO). After deaeration with nitrogen, mixtures irradiated at room temperature with gamma rays from cobalt source; total exposure time 4 hours, at rate of 0.2 milliroentgen per hour. Reaction product centrifuged three times for purification and kept in distilled water.

Rembaum, Alan

1989-01-01

408

Making Latex Microspheres in Space  

NASA Technical Reports Server (NTRS)

Equipment yields larger, more uniform particles. Two NASA reports describe first commercial product to be manufactured in space. Product monodisperse latex, suspension of spherical particles of essentially same diameter. Carried aboard Space Shuttle on its orbital missions, monodisperse latex reactor (MLR) produces spheres of much larger size than possible on Earth. Mircospheres 30 micrometers in diameter produced, whereas 5 micrometers is limit for Earthbound reactors. Microspheres as large as 100 micrometers scheduled for production in MLR.

Kornfeld, D. M.; Vanderhoff, J. W.; El-Aasser, M. S.; Micale, F. J.; Sudol, E. D.; Tseng, C. M.; Silwanowicz, A.

1986-01-01

409

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

410

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

NASA Astrophysics Data System (ADS)

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.

Haider, Adnan; Gupta, Kailash Chandra; Kang, Inn-Kyu

2014-06-01

411

Biologically inspired rosette nanotubes and nanocrystalline hydroxyapatite hydrogel nanocomposites as improved bone substitutes  

NASA Astrophysics Data System (ADS)

Today, bone diseases such as bone fractures, osteoporosis and bone cancer represent a common and significant public health problem. The design of biomimetic bone tissue engineering materials that could restore and improve damaged bone tissues provides exciting opportunities to solve the numerous problems associated with traditional orthopedic implants. Therefore, the objective of this in vitro study was to create a biomimetic orthopedic hydrogel nanocomposite based on the self-assembly properties of helical rosette nanotubes (HRNs), the osteoconductive properties of nanocrystalline hydroxyapatite (HA), and the biocompatible properties of hydrogels (specifically, poly(2-hydroxyethyl methacrylate), pHEMA). HRNs are self-assembled nanomaterials that are formed from synthetic DNA base analogs in water to mimic the helical nanostructure of collagen in bone. In this study, different geometries of nanocrystalline HA were controlled by either hydrothermal or sintering methods. 2 and 10 wt% nanocrystalline HA particles were well dispersed into HRN hydrogels using ultrasonication. The nanocrystalline HA and nanocrystalline HA/HRN hydrogels were characterized by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Mechanical testing studies revealed that the well dispersed nanocrystalline HA in HRN hydrogels possessed improved mechanical properties compared to hydrogel controls. In addition, the results of this study provided the first evidence that the combination of either 2 or 10 wt% nanocrystalline HA and 0.01 mg ml-1 HRNs in hydrogels greatly increased osteoblast (bone-forming cell) adhesion up to 236% compared to hydrogel controls. Moreover, this study showed that HRNs stimulated HA nucleation and mineralization along their main axis in a way that is very reminiscent of the HA/collagen assembly pattern in natural bone. In summary, the presently observed excellent properties of the biomimetic nanocrystalline HA/HRN hydrogel composites make them promising candidates for further study for bone tissue engineering applications.

Zhang, Lijie; Rodriguez, Jose; Raez, Jose; Myles, Andrew J.; Fenniri, Hicham; Webster, Thomas J.

2009-04-01

412

Neutron diffraction residual strain measurements in nanostructured hydroxyapatite coatings for orthopaedic implants.  

PubMed

The failure of an orthopaedic implant can be initiated by residual strain inherent to the hydroxyapatite coating (HAC). Knowledge of the through-thickness residual strain profile in the thermally sprayed hydroxyapatite coating/substrate system is therefore important in the development of a new generation of orthopaedic implants. As the coating microstructure is complex, non-destructive characterization of residual strain, e.g. using neutron diffraction, provides a useful measure of through thickness strain profile without altering the stress field. This first detailed study using a neutron diffraction technique, non-destructively evaluates the through thickness strain measurement in nanostructured hydroxyapatite plasma sprayed coatings on a titanium alloy substrate (as-sprayed, heat treated, and heat treated then soaked in simulated body fluid (SBF)). The influence of crystallographic plane orientation on the residual strain measurement is shown to indicate texturing in the coating. This texturing is expected to influence both the biological and fracture response of HA coatings. Results are discussed in terms of the influence of heat-treatment and SBF on the residual stress profile for these biomedical coatings. The results show that the through thickness residual strain in all three coatings was different for different crystallographic planes but was on average tensile. It is also concluded that the heat-treatment and simulated body fluid exposure had a significant effect on the residual strain profile in the top layers of HAC. PMID:22098904

Ahmed, R; Faisal, N H; Paradowska, A M; Fitzpatrick, M E; Khor, K A

2011-11-01

413

Polarization conversion in a silica microsphere  

E-print Network

We experimentally demonstrate controlled polarization-selective phenomena in a whispering gallery mode resonator. We observed efficient (approx. 75%) polarization conversion of light in a silica microsphere coupled to a tapered optical fiber, optimizing the polarization of the light propagating along the fiber. We present a simple model treating the microsphere as a ring resonator to explain the observed behavior.

Bianucci, P; Robertson, J W; Shvets, G; Shih, C K

2007-01-01

414

Multiplexed microsphere-based flow cytometric assays  

Microsoft Academic Search

Flow cytometry has become an indispensable tool for clinical diagnostics and basic research. Although primarily designed for cellular analysis, flow cytometers can detect any particles in the lower micron range, including inert microspheres of different sizes, dyed with various fluorochromes. Over the past 20 years, microspheres have been used as calibrators for flow cytometers and also as a solid support

Kathryn L Kellar; Marie A Iannone

2002-01-01

415

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

416