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1

Synthesis of aligned porous poly(?-caprolactone) (PCL)/hydroxyapatite (HA) composite microspheres.  

PubMed

We synthesized poly(?-caprolactone) (PCL)/hydroxyapatite (HA) composite microspheres with an aligned porous structure and evaluated their potential applications in bone tissue engineering. A range of HA particles (0, 5, 10 and 20 wt.% in relation to the PCL polymer) were added to a PCL solution in order to improve the biocompatibility of the porous PCL/HA composite microspheres. All the synthesized microspheres showed that the HA particles were distributed well in the PCL matrix, while preserving their aligned porous structure. The average size of the PCL/HA composite microspheres increased from 62±7 to 179±95 ?m with increasing HA content from 0 to 20 wt.%. The incorporation of the HA particles to the PCL polymer led to a considerable improvement in in vitro bioactivity, which was assessed by immersing the PCL/HA composite microspheres in simulated body fluid (SBF). A number of apatite crystals could be precipitated on the surface of the aligned porous PCL/HA composite microspheres after soaking in the SBF for 7 days. PMID:23498257

Kim, Mi-Jin; Koh, Young-Hag

2013-05-01

2

Preparation of hollow hydroxyapatite microspheres  

Microsoft Academic Search

The preparation of hollow hydroxyapatite (HA) microspheres as potential drug-delivery vehicles was investigated. A lithium-calcium-borate\\u000a (10Li2O-15CaO-75B2O3) (mol%) glass, made by fusing the components at 1100C for 1 h, was ground to a powder and passed through a flame at ?1400C\\u000a to spheroidize the particles. The resulting glass microspheres (106–125 ?m in diameter) were reacted in 0.25 M K2HPO4 solution for

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

2006-01-01

3

Proteinoid/hydroxyapatite hybrid microsphere composites.  

PubMed

Organic/hydroxyapatite (HA) hybrid composites are promising materials for orthopedic applications. Proteinoid/HA hybrid microsphere composite is an ideal material for bioresorbable and biocompatible three-dimensional scaffolds. Proteinoids are thermally condensed mixtures of amino acids, forming microspheres via self-assembly of proteinoid chains. Synthesis of an onion-type multilayer proteinoid/HA hybrid composite is achieved by thermally condensing a mixture of amino acids in the presence of commercially available HA. Proteinoid/HA microsphere composite of about 40 ?m are achieved as a result of heterogeneous nucleation of HA on proteinoids chains. The formation mechanism is based on the interaction between calcium ions of HA and carboxyl side groups of proteinoid. The morphology was gleaned by scanning electron microscopy, and the organic and inorganic constituents were characterized by several analytical methods. PMID:21210505

Tallawi, Marwa

2011-02-01

4

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

Microsoft Academic Search

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 µm are obtained by heterogeneous nucleation of HA on CS-PAA hollow spheres. Gelatin (Gel), acting as a novel cross-link

Haibin Zhang; Kechao Zhou; Zhiyou Li; Suping Huang

2009-01-01

5

Strength of hollow hydroxyapatite microspheres prepared by a glass conversion process  

Microsoft Academic Search

Hollow hydroxyapatite (HA) microspheres (diameter = 100–800 ?m) were prepared by reacting solid Li2O–CaO–B2O3 glass spheres in 0.25 M K2HPO4 solution at 37°C. The influence of subsequent heating on the microstructure, surface area, and compressive strength of the\\u000a HA microspheres was evaluated using scanning electron microscopy, the BET method, and nano-mechanical testing. The surface\\u000a area and rupture strength of the as-prepared microspheres were 135 m2\\/g

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

2009-01-01

6

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

7

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

8

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.

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

2011-01-01

9

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

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.

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

2013-01-01

11

Synthesis, characterization and osteoconductivity properties of bone fillers based on alendronate-loaded poly(?-caprolactone)/hydroxyapatite microspheres.  

PubMed

A superior drug controlled release system capable of achieving efficient osteogenesis is in imperative demand because of limited bone substitute tissue for the treatment of bone defect. In the present study, we investigated the potential of using poly(?-caprolactone)-hydroxyapatite (PCL-HA) composite microspheres as an injectable bone repair vehicle by controlled release of alendronate (AL), a medicine that belongs to the bisphosphonates family. The PCL/HA-AL microspheres were prepared with solid/oil/water emulsion technique, which included two processes: (1) AL was loaded on the hydroxyapatite nanoparticles; (2) the HA-AL complex was built in the PCL matrix. The spherical PCL/HA-AL microspheres were characterized with its significantly improved encapsulation efficiency of hydrophilic AL and better sustained release. Human bone mesenchymal stem cells (hMSCs) were cultured on the surface of these microspheres and exhibited high proliferative profile. Specifically, in osteogenic medium, hMSCs on the surface of PCL/HA-AL microspheres displayed superior osteogenic differentiation which was verified by alkaline phosphatase activity assay. In conclusion, by presenting strong osteogenic commitment of hMSCs in vitro, the PCL/HA-AL microspheres have the potential to be used as an injectable vehicle for local therapy of bone defect. PMID:21318627

Chen, Jianhong; Luo, Yun; Hong, Liangqing; Ling, You; Pang, Jun; Fang, Youqiang; Wei, Kun; Gao, Xin

2011-03-01

12

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

13

Biopolymers for Medical Applications: Polyglycerol Sebacate (PGS) doped Hydroxyapatite (HA)  

NASA Astrophysics Data System (ADS)

In the investigation to engineer the ideal scaffolding device for cleft palate repair, polyglycerol sebacate (PGS) doped with hydroxyapatite (HA) were chosen for their elastomeric and biodegradable properties, as well as their cost- effective synthesis. Hydroxyapatite was integrated into the PGS to form a composite with high porosity and improved mechanical properties yielding a good substrate for cell attachment during the repair process. FT-IR scans were performed to characterize the composite polymer. Differential Scanning Calorimetry (DSC) was utilized to identify an acceptable glass transition temperature (Tg), between -18 and -21 ^oC. At this Tg, it was determined that the material was sufficiently polymerized to a point where it was durable yet pliable enough to use for cleft palate devices. In the synthesis of PGS 3% and 5% HA, a Tg of -20.10 ^oC and -21.72 ^oC, respectively, was achieved and further analytical tests were then performed on the polymers. Methods of analysis included X- Ray Diffraction and Tensile Strength Testing.

Teruel, Maria; Kuthirummal, Narayanan; Levi, Nicole

2011-04-01

14

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

15

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

PubMed

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 (HPLG) have been characterised by zeta-potential and particle size measurements and the coating has been confirmed to be calcium deficient HA by analysis of X-ray diffraction, Fourier transform infrared spectroscopy and wavelength dispersive spectroscopy. The morphology of HPLG was studied by scanning electron microscopy, and cross sections of HPLG microspheres were prepared and imaged using focused ion beam microscopy. In-vitro drug release experiments in PBS (pH7.4) showed a sustained release profile for at least 31 days with little initial burst release. It shows a triphasic drug release profile commonly observed for biodegradable polymers. PMID:18325617

Xu, Qingguo; Czernuszka, Jan T

2008-04-21

16

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

17

Preparation, characterization and in-vitro release of gentamicin from coralline hydroxyapatite–chitosan composite microspheres  

Microsoft Academic Search

Composite microspheres have been prepared from bioactive ceramic such as coralline hydroxyapatite [Ca10(PO4)6(OH)2] granules, a biodegradable polymer, chitosan and an antibiotic, gentamicin. In our earlier work, we have shown a simple method of converting the calcium carbonate skeleton of the Indian corals into hydroxyapatite granules. The composite microspheres containing coralline hydroxyapatite and chitosan were prepared by dispersion polymerization technique and

M. Sivakumar; I. Manjubala; K. Panduranga Rao

2002-01-01

18

Synthesis, characterization and osteoconductivity properties of bone fillers based on alendronate-loaded poly(?-caprolactone)\\/hydroxyapatite microspheres  

Microsoft Academic Search

A superior drug controlled release system capable of achieving efficient osteogenesis is in imperative demand because of limited\\u000a bone substitute tissue for the treatment of bone defect. In the present study, we investigated the potential of using poly(?-caprolactone)–hydroxyapatite\\u000a (PCL–HA) composite microspheres as an injectable bone repair vehicle by controlled release of alendronate (AL), a medicine\\u000a that belongs to the bisphosphonates

Jianhong ChenYun; Yun Luo; Liangqing Hong; You Ling; Jun Pang; Youqiang Fang; Kun Wei; Xin Gao

2011-01-01

19

Magnetic mesoporous carbonated hydroxyapatite microspheres with hierarchical nanostructure for drug delivery systems.  

PubMed

Magnetic mesoporous carbonated hydroxyapatite microspheres have been fabricated hydrothermally by using CaCO(3)/Fe(3)O(4) microspheres as sacrificial templates. The high drug-loading capacity and sustained drug release property suggest that the multifunctional microspheres have great potentials for bone-implantable drug-delivery applications. PMID:21998826

Guo, Ya-Ping; Guo, Li-Hua; Yao, Yong-bo; Ning, Cong-Qin; Guo, Ya-Jun

2011-11-28

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.

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

2011-01-01

22

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.

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

2012-01-01

23

Preparation and characterization of hollow hydroxyapatite microspheres by spray drying method  

Microsoft Academic Search

Hollow hydroxyapatite (Ca10(PO4)6(OH)2) microspheres were prepared using a simple spray drying method. The incorporation of ammonium bicarbonate could produce carbon dioxide and ammonia gas bubbles during the spraying, and thus created a hollow inner structure in the resultant microspheres. The hollow microspheres prepared using different amounts of ammonium bicarbonate were also characterized. These microspheres were composed of nanoparticles with an

Ruixue Sun; Yupeng Lu; Kezheng Chen

2009-01-01

24

Characterization of polymeric solutions as injectable vehicles for hydroxyapatite microspheres.  

PubMed

A polymeric solution and a reinforcement phase can work as an injectable material to fill up bone defects. However, the properties of the solution should be suitable to enable the transport of that extra phase. Additionally, the use of biocompatible materials is a requirement for tissue regeneration. Thus, we intended to optimize a biocompatible polymeric solution able to carry hydroxyapatite microspheres into bone defects using an orthopedic injectable device. To achieve that goal, polymers usually regarded as biocompatible were selected, namely sodium carboxymethylcellulose, hydroxypropylmethylcellulose, and Na-alginate (ALG). The rheological properties of the polymeric solutions at different concentrations were assessed by viscosimetry before and after moist heat sterilization. In order to correlate rheological properties with injectability, solutions were tested using an orthopedic device applied for minimal invasive surgeries. Among the three polymers, ALG solutions presented the most suitable properties for our goal and a non-sterile ALG 6% solution was successfully used to perform preliminary injection tests of hydroxyapatite microspheres. Sterile ALG 7.25% solution was found to closely match non-sterile ALG 6% properties and it was selected as the optimal vehicle. Finally, sterile ALG 7.25% physical stability was studied at different temperatures over a 3-month period. It was observed that its rheological properties presented minor changes when stored at 25 degrees C or at 4 degrees C. PMID:20490958

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

2010-06-01

25

Characterization of Polymeric Solutions as Injectable Vehicles for Hydroxyapatite Microspheres  

PubMed Central

A polymeric solution and a reinforcement phase can work as an injectable material to fill up bone defects. However, the properties of the solution should be suitable to enable the transport of that extra phase. Additionally, the use of biocompatible materials is a requirement for tissue regeneration. Thus, we intended to optimize a biocompatible polymeric solution able to carry hydroxyapatite microspheres into bone defects using an orthopedic injectable device. To achieve that goal, polymers usually regarded as biocompatible were selected, namely sodium carboxymethylcellulose, hydroxypropylmethylcellulose, and Na-alginate (ALG). The rheological properties of the polymeric solutions at different concentrations were assessed by viscosimetry before and after moist heat sterilization. In order to correlate rheological properties with injectability, solutions were tested using an orthopedic device applied for minimal invasive surgeries. Among the three polymers, ALG solutions presented the most suitable properties for our goal and a non-sterile ALG 6% solution was successfully used to perform preliminary injection tests of hydroxyapatite microspheres. Sterile ALG 7.25% solution was found to closely match non-sterile ALG 6% properties and it was selected as the optimal vehicle. Finally, sterile ALG 7.25% physical stability was studied at different temperatures over a 3-month period. It was observed that its rheological properties presented minor changes when stored at 25°C or at 4°C.

Almeida, Isabel F.; Costa, Paulo C.; Barrias, Cristina C.; Ferreira, M. Rosa Pena; Bahia, M. Fernanda; Barbosa, Mario A.

2010-01-01

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

Porous hydroxyapatite scaffold with three-dimensional localized drug delivery system using biodegradable microspheres  

Microsoft Academic Search

In this study, ionic immobilization of dexamethasone (DEX)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres was performed on the hydroxyapatite (HAp) scaffold surfaces. It was hypothesized that in vivo bone regeneration could be enhanced with HAp scaffolds containing DEX-loaded PLGA microspheres compared to the use of HAp scaffolds alone. In vitro drug release from the encapsulated microspheres was measured prior to the implantation

Jun Sik Son; Mark Appleford; Joo L. Ong; Joseph C. Wenke; Jong Min Kim; Seok Hwa Choi; Daniel S. Oh

2011-01-01

28

Preparation, characterization, and in vitro release of gentamicin from coralline hydroxyapatite-alginate composite microspheres.  

PubMed

In this work, composite microspheres were prepared from bioactive ceramics such as coralline hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2)] granules, a biodegradable polymer, sodium alginate, and an antibiotic, gentamicin. Previously, we have shown a gentamicin release from coralline hydroxyapatite granules-chitosan composite microspheres. In the present investigation, we attempted to prepare composite microspheres containing coralline hydroxyapatite granules and sodium alginate by the dispersion polymerization technique with gentamicin incorporated by absorption method. The crystal structure of the composite microspheres was analyzed using X-ray powder diffractometer. Fourier transform infrared spectra clearly indicated the presence of per-acid of sodium alginate, phosphate, and hydroxyl groups in the composite microspheres. Scanning electron micrographs and optical micrographs showed that the composite microspheres were spherical in shape and porous in nature. The particle size of composite microspheres was analyzed, and the average size was found to be 15 microns. The thermal behavior of composite microspheres was studied using thermogravimetric analysis and differential scanning calorimetric analysis. The cumulative in vitro release profile of gentamicin from composite microspheres showed near zero order patterns. PMID:12734816

Sivakumar, M; Rao, K Panduranga

2003-05-01

29

Preparation, characterization and in vitro release of gentamicin from coralline hydroxyapatite-gelatin composite microspheres.  

PubMed

Composite microspheres have been prepared from bioactive ceramics such as coralline hydroxyapatite [CHA, Ca10(PO4)6(OH)2] granules, a biodegradable polymer, gelatin and an antibiotic, gentamicin. In our earlier work, we have shown a gentamicin release from CHA granules--chitosan composite microspheres. In the present investigation, an attempt was made to prepare the composite microspheres containing coralline hydroxyapatite and gelatin (CHA-G), which were prepared by the dispersion polymerization technique and the gentamicin was incorporated by the absorption method. The crystal structure of the composite microspheres was analyzed using X-ray powder diffractometer. The Fourier transformed infrared spectrum clearly indicated the presence of amide and hydroxyl groups in the composite microspheres. Scanning electron micrographs and optical micrographs show that the composite microspheres are spherical in shape and porous in nature. The particle size of composite microspheres was analyzed and the average size was found to be 16 microm. The thermal behavior of composite microspheres was studied using thermogravimetric analysis and differential scanning calorimetric analysis. The cumulative in vitro release profile of gentamicin from composite microspheres showed near zero order patterns. PMID:12102189

Sivakumar, M; Panduranga Rao, K

2002-08-01

30

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

31

Development of Nanolayer Hydroxyapatite (HA) on Titanium Alloy via Superplastic Deformation Method  

NASA Astrophysics Data System (ADS)

In this work, hydroxyapatite (HA) is successfully embedded onto titanium alloy using the superplastic deformation method. An embedded layer of approximately 249 nm is obtained at a temperature of 1200 K (927 °C), strain rate of 1 × 10-4 s-1, and process duration of 90 minutes. X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) analyses indicate that HA is retained after the embedment process, and a significant amount of titanium (Ti) is diffused into the HA, forming a dense HA/Ti composite layer. Wear tests under a simulated body fluids (SBF) condition show that the adherent strength of HA and the interfacial strength between the HA layer and substrate are superior compared with the nonsuperplastic sample.

Khalid, Hidayah Mohd; Jauhari, Iswadi; Dom, Adibah Haneem Mohamad

2012-10-01

32

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

33

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

PubMed

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

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

2012-10-01

34

Porous hydroxyapatite scaffold with three-dimensional localized drug delivery system using biodegradable microspheres.  

PubMed

In this study, ionic immobilization of dexamethasone (DEX)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres was performed on the hydroxyapatite (HAp) scaffold surfaces. It was hypothesized that in vivo bone regeneration could be enhanced with HAp scaffolds containing DEX-loaded PLGA microspheres compared to the use of HAp scaffolds alone. In vitro drug release from the encapsulated microspheres was measured prior to the implantation in the femur defects of beagle dogs. It was observed that porous, interconnected HAp scaffolds as well as DEX-loaded PLGA microspheres were successfully fabricated in this study. Additionally, PEI was successfully coated on PLGA microsphere surfaces, resulting in a net positive-charged surface. With such modification of the PLGA microsphere surfaces, DEX-loaded PLGA microspheres were immobilized on the negatively charged HAp scaffold surfaces. Release profile of DEX over a 4week immersion study indicated an initial burst release followed by a sustained release. In vivo evaluation of the defects filled with DEX-loaded HAp scaffolds indicated enhanced volume and quality of new bone formation when compared to defects that were either unfilled or filled with HAp scaffolds alone. This innovative platform for bioactive molecule delivery more potently induced osteogenesis in vivo, which may be exploited in implantable bone graft substitutes for stem cell therapy or improved in vivo performance. It was thus concluded that various bioactive molecules for bone regeneration might be efficiently incorporated with calcium phosphate-based bioceramics using biodegradable polymeric microspheres. PMID:21420453

Son, Jun Sik; Appleford, Mark; Ong, Joo L; Wenke, Joseph C; Kim, Jong Min; Choi, Seok Hwa; Oh, Daniel S

2011-07-30

35

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

PubMed

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

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

2012-01-01

36

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.

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

2012-01-01

37

Effect of interfacial serum proteins on melanoma cell adhesion to biodegradable poly(l-lactic acid) microspheres coated with hydroxyapatite.  

PubMed

We have measured the interaction forces between a murine melanoma cell and a poly(l-lactic acid) (PLLA) microsphere coated with/without hydroxyapatite (HAp) nanoparticles (i.e., an HAp/PLLA or a bare PLLA microsphere) in a serum-free culture medium, using atomic force microscopy (AFM) with colloid probe technique, in order to investigate how the HAp-nanoparticle coating as well as interfacial serum proteins influence the cell-microsphere adhesion. The cell adhesion force of the HAp/PLLA microspheres was 1.4-fold stronger than that of the bare PLLA microspheres. When the microspheres were pretreated with a culture medium supplemented with 10% fetal bovine serum, the cell adhesion force of the HAp/PLLA microspheres was increased by a factor of 2.1; in contrast, no change was observed in the cell adhesion force of the bare PLLA microspheres before/after the pretreatment. Indeed, the cell adhesion force of the HAp/PLLA was 2.8-fold larger than that of the bare PLLA after the pretreatment. Additionally, we have investigated the effect of interfacial serum proteins on the zeta potentials of these microspheres. On the basis of the obtained results, possible mechanism of cell adhesion to the HAp/PLLA and bare PLLA microspheres in the presence/absence of the interfacial serum proteins is discussed. PMID:23524077

Shinto, Hiroyuki; Hirata, Takuya; Fukasawa, Tomonori; Fujii, Syuji; Maeda, Hayata; Okada, Masahiro; Nakamura, Yoshinobu; Furuzono, Tsutomu

2013-08-01

38

Fabrication, characterization, and in vitro evaluation of poly(lactic acid glycolic acid)/nano-hydroxyapatite composite microsphere-based scaffolds for bone tissue engineering in rotating bioreactors.  

PubMed

Dynamic flow culture bioreactor systems have been shown to enhance in vitro bone tissue formation by facilitating mass transfer and providing mechanical stimulation. Our laboratory has developed a biodegradable poly (lactic acid glycolic acid) (PLAGA) mixed scaffold consisting of lighter-than-water (LTW) and heavier-than-water (HTW) microspheres as potential matrices for engineering tissue using a high aspect ratio vessel (HARV) rotating bioreactor system. We have demonstrated enhanced osteoblast differentiation and mineralization on PLAGA scaffolds in the HARV rotating bioreactor system when compared with static culture. The objective of the present study is to improve the mechanical properties and bioactivity of polymeric scaffolds by designing LTW polymer/ceramic composite scaffolds suitable for dynamic culture using a HARV bioreactor. We employed a microsphere sintering method to fabricate three-dimensional PLAGA/nano-hydroxyapatite (n-HA) mixed scaffolds composed of LTW and HTW composite microspheres. The mechanical properties, pore size and porosity of the composite scaffolds were controlled by varying parameters, such as sintering temperature, sintering time, and PLAGA/n-HA ratio. The PLAGA/n-HA (4:1) scaffold sintered at 90 degrees C for 3 h demonstrated the highest mechanical properties and an appropriate pore structure for bone tissue engineering applications. Furthermore, evaluation human mesenchymal stem cells (HMSCs) response to PLAGA/n-HA scaffolds was performed. HMSCs on PLAGA/n-HA scaffolds demonstrated enhanced proliferation, differentiation, and mineralization when compared with those on PLAGA scaffolds. Therefore, PLAGA/n-HA mixed scaffolds are promising candidates for HARV bioreactor-based bone tissue engineering applications. PMID:19030184

Lv, Qing; Nair, Lakshmi; Laurencin, Cato T

2009-12-01

39

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

PubMed

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

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

2013-10-01

40

Porous nano-HA/collagen/PLLA scaffold containing chitosan microspheres for controlled delivery of synthetic peptide derived from BMP-2.  

PubMed

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 was used as the solvent for PLLA. Introduction of less than 30% of CMs (on PLLA weight basis) did not remarkably affect the morphology and porosity of the nHAC/PLLA/CMs scaffolds. However, as the microspheres contents increased to 50%, the porosity of the composite decreased rapidly. The compressive modulus of the composite scaffolds increased from 15.4 to 25.5 MPa, while the compressive strength increased from 1.42 to 1.63 MPa as the microspheres contents increased from 0% to 50%. The hydrolytic degradation and synthetic peptide release kinetics in vitro were investigated by incubation in phosphate buffered saline solution (pH 7.4). The results indicated that the degradation rate of the scaffolds was increased with the enhancement of CMs dosage. The synthetic peptide was released in a temporally controlled manner, depending on the degradation of both incorporated chitosan microspheres and PLLA matrix. In vitro bioactivity assay revealed that the encapsulated synthetic peptide was biologically active as evidenced by stimulation of rabbit marrow mesenchymal stem cells (MSCs) alkaline phosphatase (ALP) activity. The successful microspheres-scaffold system offers a new delivery method of growth factors and a novel scaffold design for bone regeneration. PMID:19100794

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

2009-03-01

41

Osteogenic differentiation of human bone marrow stromal cells in hydroxyapatite-loaded microsphere-based scaffolds.  

PubMed

Calcium-based minerals have consistently been shown to stimulate osteoblastic behavior in vitro and in vivo. Thus, use of such minerals in biomaterial applications has become an effective method to enhance bone tissue engineered constructs. In the present study, for the first time, human bone marrow stromal cells (hBMSC) were osteogenically differentiated on scaffolds consisting only of hydroxyapatite (HAp)-loaded poly(D,L-lactic acid-co-glycolic acid) (PLGA) microspheres of high monodispersity. Scaffold formulations included 0, 5, 10, and 20 wt% Hap, and the hBMSC were cultured for 6 weeks. Results demonstrated suppression of some osteogenic genes during differentiation in the HAp group, but higher end-point glycosaminoglycan and collagen content in 10% and 20% HAp samples, as evidenced by biochemical tests, histology, and immunohistochemistry. After 6 weeks of culture, constructs with 0% and 5% HAp had average compressive moduli of 0.7 ± 0.2 and 1.5 ± 0.9 kPa, respectively, whereas constructs with 10% and 20% HAp had higher average moduli of 17.6 ± 4.6 and 18.9 ± 8.1 kPa, respectively. The results of this study indicate that HAp inclusion in microsphere-based scaffolds could be implemented as a physical gradient in combination with bioactive signal gradients seen in previous iterations of these microsphere-based scaffolds to enhance osteoconduction and mechanical integrity of a healing site. PMID:21992088

Dormer, Nathan H; Qiu, Yue; Lydick, Anna M; Allen, Nicholas D; Mohan, Neethu; Berkland, Cory J; Detamore, Michael S

2012-04-01

42

Hydroxyapatite nanosheet-assembled microspheres: hemoglobin-templated synthesis and adsorption for heavy metal ions.  

PubMed

Hydroxyapatite (HAP) nanostructures have wide potential applications in many fields such as drug delivery, tissue engineering, bone repair, gas sensing, catalysis and water treatment. Inspired with the fact that HAP has a high affinity with proteins, we have designed and developed a new synthetic strategy for three-dimensional (3-D) HAP nanosheet-assembled microspheres (HAP-NMSs) by employing hemoglobin as a soft template. The as-prepared products are characterized by X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (SEM). The experimental results show that 3-D HAP microspheres are constructed by the self-assembly of HAP nanosheets as the building blocks. The influences of hemoglobin concentration, hydrothermal temperature and time on the morphology and crystal phase of the product are investigated. Based on the systematic investigation, a possible formation mechanism of HAP-NMSs is proposed. The as-prepared HAP-NMSs are explored for the potential application in water treatment. The experimental results indicate that the HAP-NMSs have a high adsorption capacity for heavy metal ions and selective adsorption activity for Pb(2+) ions in acidic solution, thus are promising for the application in wastewater treatment. PMID:24370395

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

2014-02-15

43

Injectability of a bone filler system based on hydroxyapatite microspheres and a vehicle with in situ gel-forming ability.  

PubMed

The aim of this study was to test the injectability of a bone filler system based on the combination of ceramic microspheres with a gel-like vehicle, for noninvasive surgery. Porous hydroxyapatite microspheres with a uniform size and an average diameter of 535 +/- 38 mum were prepared, and their compression strength and friability were tested. The sodium-alginate solution with a concentration of 7.25% (w/v) was used as the vehicle. To promote its in situ gelation, calcium carbonate and D-gluconic-delta-lactone were added to the solution. Microspheres were mixed with the vehicle at different percentages (20-40 wt %). Gelation times in the range of 8-20 min, were obtained, depending on the formulation. Mixtures of HAp microspheres with alginate solution at 7.25% originating a gel in 11 min present an adequate handling time to perform an injection. Their injectability was evaluated using an injection device commonly employed in vertebroplasty surgical procedures, coupled to a texturometer in compression mode. Using an extrusion rate of 0.1 mm/s, the force required to extrude any of the mixtures tested was lower than 100 N. For an extrusion rate of 1 mm/s mixtures with 40 wt % of microspheres were very difficult to inject. Mixtures with 35 wt % of microspheres presented the best compromise between injectability and compression strength of the gelled system. MicroCT analysis revealed a homogeneous distribution of the microspheres inside the vehicle, as well as full interconnection of the intra-microspheres spaces. The compression strength for the gelled systems ranged from 80 kPa (gel itself) to 600 kPa (composite with 40 wt % of microspheres). PMID:18437700

Oliveira, Serafim M; Barrias, Cristina C; Almeida, Isabel F; Costa, Paulo C; Ferreira, Maria R Pena; Bahia, Maria F; Barbosa, Mário A

2008-10-01

44

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

PubMed

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

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

2013-05-01

45

In Vitro and In Vivo Evaluations of Nano-Hydroxyapatite/Polyamide 66/Glass Fibre (n-HA/PA66/GF) as a Novel Bioactive Bone Screw  

PubMed Central

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.

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

2013-01-01

46

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.

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

47

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.

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

2013-01-01

48

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

49

Development of Microspheres Covered with Hydroxyapatite Nanocrystals as Cell Scaffold for Angiogenesis  

NASA Astrophysics Data System (ADS)

We prepared poly(L-lactide-co-glycolide) cell scaffolds coated with hydroxyapatite (HAp) nanocrystals with 50-100 nm in diameter via the Pickering emulsion method. Our cell scaffolds were composed of biodegradable polymers and HAp nanocrystals as a core and shell, respectively. The scaffolds were spherical but displayed uneven shapes when altering a shear speed of homogenization during syntheses. The surface coverage of HAp nanocrystals was examined because the HAp-coating ratio for the scaffolds was an important factor as cell scaffolds in order to enhance cell adhesion. On the basis of scanning electron microscopy observations and thermogravimetric analyses, it was found that the cell scaffolds showed distorted morphologies, and the HAp-coating ratio decreased with increasing the shear speed in the synthesis because shear stress influenced shapes of the scaffolds.

Iwamoto, Takashi; Terada, Takahiro; Kogai, Yasumichi; Okada, Masahiro; Fujii, Syuji; Furuzono, Tsutomu

2012-06-01

50

Bioactive, degradable composite microspheres: effect of filler material on surface reactivity.  

PubMed

Composite microspheres with two different fillers were developed using a solid-in-oil-in-water (s/o/w) emulsion solvent removal method. Two types of bioactive ceramic powders, specifically calcium hydroxyapatite (HA) and modified bioactive glass (MBG), were incorporated into degradable poly(lactic acid) (PLA) polymer matrix to form composite microspheres. For each filler material, microspheres with three different weight ratios of filler material to polymer, namely, 1: 1, 1: 3, and 1: 9, were synthesized. In vitro immersion using simulated physiological fluid (SPF) was employed to evaluate the surface reactivity of the microspheres. SEM analysis revealed that after a 14-day immersion the surface of the microspheres containing 50% MBG was fully transformed into a bone-like apatite. In contrast, a limited number of mineral nodules were present on the surface of microspheres containing HA. The solution chemical analyses performed to determine changes of Ca, P, and Si concentrations as a function of the immersion time showed that the ion concentration profiles were similar for all microspheres, except the [Si] profile. A higher Si concentration was detected in the SPF immersed with MBG-containing microspheres. These data show that the MBG filler significantly enhances the surface reactivity of the composite microspheres. This observation enables us to conclude that the composite MBG-containing microspheres are the preferable microspheres for three-dimensional bone tissue engineering. PMID:12446347

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

2002-10-01

51

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

52

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

53

BCP ceramic microspheres as drug delivery carriers: synthesis, characterisation and doxycycline release  

Microsoft Academic Search

Resorbable ceramics such as biphasic calcium phosphates (BCP) are ideal candidates as drug delivery systems. The BCP ceramic\\u000a is based on the optimum balance of the most stable hydroxyapatite (HA) phase and more soluble tricalcium phosphate phase (TCP).\\u000a Doxycycline is a broad-spectrum antibiotic used for the local treatment of periodontitis. The development of BCP microspheres\\u000a and its release kinetics with

Sunita Prem Victor; T. S. Sampath Kumar

2008-01-01

54

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

55

BCP ceramic microspheres as drug delivery carriers: synthesis, characterisation and doxycycline release.  

PubMed

Resorbable ceramics such as biphasic calcium phosphates (BCP) are ideal candidates as drug delivery systems. The BCP ceramic is based on the optimum balance of the most stable hydroxyapatite (HA) phase and more soluble tricalcium phosphate phase (TCP). Doxycycline is a broad-spectrum antibiotic used for the local treatment of periodontitis. The development of BCP microspheres and its release kinetics with doxycycline have been studied. The BCP ceramic powder were prepared by microwave processing and characterised by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) methods. The BCP microspheres were formed by liquid immiscibility effect using gelatin and paraffin oil. Difference in the morphology of the microspheres as a function of gelatin content has been observed. Scanning electron microscope indicated spherical and porous morphology of the microspheres. Drug incorporation was studied at varying pH and the pH 7 was found to be optimal for drug loading. Release pattern tend to depend on the morphology of BCP microspheres. An optimum release of 80% drug has been observed for BCP microsphere with HA:TCP=65:35 ratio. The surface area measurement results also correlate with drug release obtained. PMID:17597367

Victor, Sunita Prem; Kumar, T S Sampath

2008-01-01

56

New bioactive, degradable composite microspheres as tissue engineering substrates.  

PubMed

Novel bioactive, degradable polymer/glass/ceramic composite microspheres were developed using a solid-in-oil-in-water (s/o/w) emulsion solvent removal method. Modified bioactive glass (MBG) powders were encapsulated into the polylactic acid (PLA) matrix. Scanning electron microscopy and energy-dispersive X-ray analyses revealed that the MBG powders were mostly embedded in the polymer matrix, and submicron-size pores were present at the surface. Immersion in simulated physiological fluid (SPF) was used to evaluate the surface reactivity of the microspheres. The polymeric surface was fully transformed into carbonated calcium hydroxyapatite (c-HA) after 3 weeks of immersion. In contrast, PLA microspheres showed no evidence of any calcium phosphate deposition. Ion concentration analyses revealed a decrease in Ca and P concentrations and an increase in Si concentration in the SPF immersed with composite microspheres during the 3-week period. The Ca and P uptake rates decreased after 2 days of incubation. This coincided with the decrease of the Si release rate. These data lend support to the suggestion that the Si released from the MBG powders present in the polymer matrix is involved in the formation of the Ca-P layer. Our results support the concept that these new bioactive, degradable composite microspheres may serve as microcarriers for synthesis of bone and other tissues in vitro and in vivo. PMID:10906676

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

2000-10-01

57

Long-term conversion of 45S5 bioactive glass-ceramic microspheres in aqueous phosphate solution.  

PubMed

The conversion of 45S5 glass and glass-ceramics to a hydroxyapatite (HA)-like material in vitro has been studied extensively, but only for short reaction times (typically <3 months). In this paper, we report for the first time on the long-term conversion of 45S5 glass-ceramic microspheres (designated 45S5c) in an aqueous phosphate solution. Microspheres of 45S5c (75-150 ?m) were immersed for 10 years at room temperature (~25 °C) in K(2)HPO(4) solution with a concentration of 0.01 M or 1.0 M, and with a starting pH of 7.0 or 9.5. The reacted 45S5c microspheres and solutions were analyzed using structural and analytical techniques. Only 25-45 vol% of the 45S5c microspheres were converted to an HA-like material after the 10 year reaction. In solutions with a starting pH of 9.5, an increase in the K(2)HPO(4) concentration from 0.01 to 1.0 M resulted in a doubling of the volume of the microspheres converted to an HA-like material but had little effect on the composition of the HA-like product. In comparison, reaction of the 45S5c microspheres in the solution with a starting pH of 7.0 resulted in an HA-like product in the 0.01 M K(2)HPO(4) solution but a calcium pyrophosphate product, Ca(10)K(4)(P(2)O(7))(6).9H(2)O, in the 1.0 M solution. The consequences of these results for the long-term use of 45S5 glass-ceramics in biomedical applications are discussed. PMID:22415362

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

2012-05-01

58

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

59

Formulation, antimicrobial and toxicity evaluation of bioceramic based ofloxacin loaded biodegradable microspheres for periodontal infection.  

PubMed

In the present study an attempt has been made to load Poly (Lactic-Co-glycolic acid) microspheres with hydroxyapatite (HA) and ofloxacin and propose the composite microspheres to be used as local drug delivery system with the drug releasing capability for periodontitis treatment. A modified single emulsion method has been used for the preparation of microspheres. Experiments were conducted to optimize the formulation by RSM-Box-Behnken Method, which is an independent quadratic design involving three or four independent variables against a pre determined set of dependant parameters. The particle size of composite microspheres was analyzed and the average size was found to be 22.05 ?m. Photomicrographs and scanning electron micrographs showed that the composite microspheres are spherical in shape and porous in nature. The microbiological activity of optimized formulation was evaluated using strain: S. aureus-ATCC- 29213 and E. coli-ATCC-25922. In vivo/in situ toxicity evaluation of the formulation was assessed by MTT assay and the formulation was found to be biocompatible. PMID:22758655

Jamal, Tariq; Rahman, Md Akhlaquer; Mirza, Mohd Aamir; Panda, A K; Talegaonkar, Sushama; Iqbal, Zeenat

2012-09-01

60

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

61

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

62

Multi-functional P(3HB) microsphere/45S5 Bioglass-based composite scaffolds for bone tissue engineering.  

PubMed

Novel multi-functional P(3HB) microsphere/45S5 Bioglass-based composite scaffolds exhibiting potential for drug delivery were developed for bone tissue engineering. 45S5 Bioglass-based glass-ceramic scaffolds of high interconnected porosity produced using the foam-replication technique were coated with biodegradable microspheres (size<2 microm) made from poly(3-hydroxybutyrate), P(3HB), produced using Bacillus cereus SPV. A solid-in-oil-in-water emulsion solvent extraction/evaporation technique was used to produce these P(3HB) microspheres. A simple slurry-dipping method, using a 1 wt.% suspension of P(3HB) microspheres in water, dispersed by an ultrasonic bath, was used to coat the scaffold, producing a uniform microsphere coating throughout the three-dimensional scaffold structure. Compressive strength tests confirmed that the microsphere coating slightly enhanced the scaffold mechanical strength. It was also confirmed that the microsphere coating did not inhibit the bioactivity of the scaffold when immersed in simulated body fluid (SBF) for up to 4 weeks. The hydroxyapatite (HA) growth rate on P(3HB) microsphere-coated 45S5 Bioglass composite scaffolds was very similar to that on the uncoated control sample, qualitatively indicating similar bioactivity. However, the surface topography of the HA surface layer was affected as shown by results obtained from white light interferometry. The roughness of the surface was much higher for the P(3HB) microsphere-coated scaffolds than for the uncoated samples, after 7 days in SBF. This feature would facilitate cell attachment and proliferation. Finally, gentamycin was successfully encapsulated into the P(3HB) microspheres to demonstrate the drug delivery capability of the scaffolds. Gentamycin release kinetics was determined using liquid chromatography-mass spectrometry. The release of the drug from the coated composite scaffolds was slow and controlled when compared to the observed fast and relatively uncontrolled drug release from the bone scaffold (without microsphere coating). Thus, this unique multifunctional bioactive composite scaffold has the potential to enhance cell attachment and to provide controlled delivery of relevant drugs for bone tissue engineering. PMID:20056174

Francis, Lydia; Meng, Decheng; Knowles, Jonathan C; Roy, Ipsita; Boccaccini, Aldo R

2010-07-01

63

Spark plasma sintering of hydroxyapatite powders  

Microsoft Academic Search

Dense hydroxyapatite (HA) compacts have been successfully fabricated by a spark plasma sintering (SPS). The sintering behavior of HA powders at different temperatures ranging from 850°C to 1100°C was studied. Results showed that spark plasma sintering resulted in rapid densification to near theoretical density. The HA compact was homogeneously sintered at 950°C in a short sintering duration of 5min, while

Y. W. Gu; N. H. Loh; K. A. Khor; S. B. Tor; P. Cheang

2002-01-01

64

Electrodeposition of composite hydroxyapatite–chitosan films  

Microsoft Academic Search

Hydroxyapatite (HA) powders were prepared by a chemical precipitation method and used for the fabrication of the HA–chitosan nanocomposite coatings. The proposed method for the coating fabrication is based on the electrochemical deposition of chitosan and electrophoretic deposition of HA. Cathodic deposits of various thicknesses in the range of up to 50?m were obtained on Pt and stainless steel foils,

Xin Pang; Igor Zhitomirsky

2005-01-01

65

Prolonged osteogenesis from human mesenchymal stem cells implanted in immunodeficient mice by using coralline hydroxyapatite incorporating rhBMP2 microspheres.  

PubMed

The local environment plays an important role in osteogenic tissue regeneration. Our previous studies have shown that xenogenic transplantation of human mesenchymal stem cells (hMSCs) alone into immunodeficient mice did not result in long-term bone formation. This study investigates whether bone formation can be prolonged by incorporating human mesenchymal stem cells in mineralized scaffolds together with controlled delivery of a growth factor, BMP2. A composite of coralline hydroxyapatite (CHA) with poly(lactic-co-glycolic acid) (PLGA)-encapsulated rhBMP2 was incorporated with hMSCs in vitro. After 2 weeks in vitro culture the constructs were implanted subcutaneously in CB17 scid beige mice and harvested 10 weeks after implantation. The mineralized tissues were stained by using a fluorescent marker, 5FAM-risedronate, followed by observation with fluorescence microscopy, histology, histomorphometry, mouse-anti-human vimentin immunohistochemistry, and scanning microscopy. The results showed that compared with control materials in which only fibrous tissue formed following implantation of coralline scaffolds, bone-like tissue formed within the CHA composite containing PLGA encapsulated rhBMP2 and hMSCs for up to 10 weeks after implantation. Human cells, identified by the human vimentin-specific monoclonal antibody were seen within the bone-like tissue. In conclusion, incorporation of hMSCs into CHA with controlled delivery of BMP showed prolonged bone formation in immunodeficient mice. Further research is required to optimize the growth factor delivery system and to understand the underlying cellular and molecular mechanisms involved. PMID:19322875

Fu, Kun; Xu, Qingguo; Czernuszka, Jan; McKenna, Charles E; Ebetino, Frank H; Russell, R Graham G; Triffitt, James T; Xia, Zhidao

2010-03-15

66

Densification behaviour of nanocrystalline hydroxyapatite bioceramics  

Microsoft Academic Search

The sinterability of nanocrystalline hydroxyapatite (HA) particles by microwave sintering was compared with conventional pressureless sintering. The results revealed that microwave heating was effective in producing a useful HA body in a very short sintering cycle without disrupting the HA phase stability. The maximum hardness of 7.21GPa and 6.38GPa was obtained for HA sintered at 1050°C by the conventional method

S. Ramesh; C. Y. Tan; S. B. Bhaduri; W. D. Teng; I. Sopyan

2008-01-01

67

Effect of fluoridation of hydroxyapatite in hydroxyapatite-polycaprolactone composites on osteoblast activity  

Microsoft Academic Search

Fluorine was administered to a system of hydroxyapatite (HA)\\/polycaprolactone (PCL) ceramic-polymer bioactive composites for applications as hard tissue regeneratives. The HA was fluoridated at different levels (5%, 25%, 50% and 75%) in order to produce the fluor-hydroxyapatite (FHA)\\/PCL composites. The osteoblastic cellular responses to the composites were examined in terms of the cell attachment, proliferation and differentiation as well as

Hae-Won Kim; Eun-Jung Lee; Hyoun-Ee Kim; Vehid Salih; Jonathan C. Knowles

2005-01-01

68

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

69

First-principles study of hydroxyapatite surfaces and water adsorption  

Microsoft Academic Search

Hydroxyapatite (HA) is the main mineral component of natural bone and an important synthetic biomaterial. The surfaces of this material are critical as the biological action takes place at the interface between the HA and the biological medium. Ab initio total energy methods are used to study the atomic structure and surface chemistry of HA. Low index HA surfaces in

R. Astala; M. J. Stott

2008-01-01

70

In vivo assessment of hydroxyapatite and silicate-substituted hydroxyapatite granules using an ovine defect model.  

PubMed

Phase pure hydroxyapatite (HA) and two silicate-substituted hydroxyapatites (0.8 and 1.5 wt% Si, or 2.6 and 4.9 wt% SiO4) were prepared by aqueous precipitation methods. The filter-cakes of HA and silicate-substituted hydroxyapatite (SiHA) compositions were processed into granules 1.0-2.0 mm in diameter and sintered at 1200 degrees C for 2 h. The sintered granules underwent full structural characterisation, prior to assessment in an ovine defect model by implantation for a period of 6 and 12 weeks. The results indicate that HA and SiHA implants were well accepted by the host tissue, with no evidence of inflammation. New bone formation was observed directly on the surfaces and in the spaces between the granular implants. Quantitative histomorphometry as determined by the percentage of bone ingrowth and bone coverage for both SiHA implant compositions was significantly greater than that for phase pure HA. These findings indicate that the in vivo bioactivity of hydroxyapatite was significantly improved by the incorporation of silicate ions into the HA structure, making SiHA ceramics attractive alternatives to conventional HA materials for use as bone graft substitute ceramics. PMID:15875253

Patel, N; Brooks, R A; Clarke, M T; Lee, P M T; Rushton, N; Gibson, I R; Best, S M; Bonfield, W

2005-05-01

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

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

73

Alternative technique for hydroxyapatite coatings  

Microsoft Academic Search

Flame Assisted Chemical Vapor Deposition (FACVD), a novel technique that shows an enormous potential in porous oxides deposition, was employed for the first time aiming to obtain hydroxyapatite (HA) coatings on 316 L stainless steel metallic substrates. Calcium acetate and ammonium phosphate diluted in ethanol were employed as precursor salts. A Ca\\/P molar ratio of 1.66 was employed in precursor solution,

R. M. Trommer; L. A. Santos; C. P. Bergmann

2007-01-01

74

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

75

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

76

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

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

Osteopenic bone cell response to strontium-substituted hydroxyapatite  

Microsoft Academic Search

Ionic substitution is a powerful tool to improve the biological performance of calcium phosphate based materials. In this\\u000a work, we investigated the response of primary cultures of rat osteoblasts derived from osteopenic (O-OB) bone to strontium\\u000a substituted hydroxyapatite (SrHA), and to hydroxyapatite (HA) as reference material, compared to normal (N-OB) bone cells.\\u000a Strontium (Sr) and calcium (Ca) cumulative releases in

E. Boanini; P. Torricelli; M. Fini; A. Bigi

79

Preparation and bioactivity evaluation of hydroxyapatite-titania\\/chitosan-gelatin polymeric biocomposites  

Microsoft Academic Search

Biocomposites consisting of hydroxyapatite (HA) and natural polymers such as collagen, chitosan, chitin,and gelatin have been extensively investigated. However, studies on the combination of HA and titania with chitosan and gelatin have not been conducted yet. Novel biodegradable hydroxyapatite-titania\\/chitosan-gelatin polymeric composites were fabricated. In this work, our results are concerning with the preparation and characterization of HA powder and HA

Khaled R. Mohamed; Amani A. Mostafa

2008-01-01

80

Laser surface modification of hydroxyapatite and glass-reinforced hydroxyapatite.  

PubMed

Surface treatment of materials with excimer laser radiation often results in the formation of a rough columnar or cone-shaped surface topography, which leads to a considerable increase in the surface area. As a result, the search for a non-porous bioactive material with adequate mechanical properties and a high surface to volume ratio, similar to porous materials, which could be used for drug delivery in the treatment of periodontitis, justified assessing excimer laser surface treatment to promote controlled roughning of hydroxyapatite (HA) and glass-reinforced hydroxyapatite (GR-HA). A KrF excimer laser with 248 nm radiation wavelength and 30 ns pulse duration was used for surface modification. The laser treatment was carried out in air, using wide ranges of radiation fluence and number of laser pulses. In order to identify the physico-chemical changes induced by the laser treatment and the column formation mechanisms in these materials, the treated surfaces were characterised by laser profilometry, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infra-red spectroscopy (FTIR). Laser processing induced the formation of a surface topography consisting of cone-shaped features. The constitution of the surface layer was also modified, as revealed by FTIR, XPS and XRD. This work has shown that laser surface modification increases the surface area of HA and GR-HA and is a promising technique to increase the reactivity and drug delivery capability of both materials. PMID:15120506

Queiroz, Ana C; Santos, José D; Vilar, Rui; Eugénio, Sónia; Monteiro, Fernando J

2004-08-01

81

Electrical characterization of hydroxyapatite-based bioceramics  

Microsoft Academic Search

This paper studies the AC conductivity and permittivity of hydroxyapatite (HA)-based ceramics from 0.1Hz–1MHz at temperatures from room temperature to 1000°C. HA-based ceramics were prepared either as dense ceramics or in porous form with interconnected porosity and were sintered in either air or water vapour. Samples were thermally cycled to examine the influence of water desorption on AC conductivity and

J. P. Gittings; C. R. Bowen; A. C. E. Dent; I. G. Turner; F. R. Baxter; J. B. Chaudhuri

2009-01-01

82

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

83

Using HaXe  

Microsoft Academic Search

haXe is a high-level programming language for web development. It can be compiled into .js files for JavaScript developers\\u000a or into .swf files for Flash, and it also supports the Neko virtual machine. Before going into the details of haXe, I’ll explain\\u000a how it came to be and how it is related to the evolution of Flash, ActionScript, and some

Nicolas Cannasse

84

Development of composite tissue scaffolds containing naturally sourced mircoporous hydroxyapatite  

Microsoft Academic Search

The aims of this work were to investigate the conversion of a marine alga into hydroxyapatite (HA), and furthermore to design a composite bone tissue engineering scaffold comprising the synthesised HA within a porous bioresorbable polymer. The marine alga, Phymatolithon calcareum, which exhibits a calcium carbonate honeycomb structure, with a natural architecture of interconnecting permeable pores (microporosity 4–11?m), provided the

F. Kusmanto; G. Walker; Q. Gan; P. Walsh; F. Buchanan; G. Dickson; M. McCaigue; C. Maggs; M. Dring

2008-01-01

85

Nanostructured hydroxyapatite by microwave sintering.  

PubMed

In this work, nanostructured HA ceramics with dense microstructure were prepared by microwave sintering process and their microstructures were compared with the case of conventional sintering. Commercially obtained HA powder with Ca/P molar ratio of 1.67 was used as a starting material. The powder of granular type consists of nanocrystalline particles of 20-30 nm in size. The as-received HA powder or the powder calcined at 800 degrees C, followed by ball-milling was used for the preparation of HA disks. Microwave sintering was conducted at 1200 degrees C for 5 min with a heating rate of 50 degrees C/min. HA ceramics with the sintered densities of approximately 96-97% of the theoretical were obtained. XRD analysis showed that all detectable peaks are identical to pure hydroxyapatite. The HA sintered body made of calcined and ball-milled powder showed uniform microstructure with grain size of 300-400 nm and with finer sub-grains of 30-40 nm. PMID:18464431

Seo, Dong Seok; Hwang, Kyu Hong; Lee, Jong Kook

2008-02-01

86

Hydroxyapatite coatings.  

PubMed

Four coating techniques were evaluated to determine which is most suitable for producing a dense, highly adherent coating onto metallic and ceramic implant materials. Two of the selected coating methods have serious limitations for use in this particular application, and did not meet the specified criteria for satisfactory coating as defined in the initial stages of the study. For example, the dip coating-sintering technique was judged to be unsatisfactory because of the adverse effect of the high-temperature sintering cycle on the mechanical properties of the metallic substrate materials. These materials could not be used in load-bearing applications because of the excessive grain growth and loss of the wrought structure of both the commercially pure Ti and Ti-6Al-4V substrates, and the loss of ductility in the cast Co-Cr-Mo alloy. Another area of concern was that bond strength between the HA coating and the substrate was not high enough to insure that interfacial failure would not occur during the lifetime of the implant. The immersion-coating technique, in which the metal substrate is immersed into the molten ceramic, was shown in a previous study to be the best method of coating a bioreactive glass onto a Co-Cr-Mo implant. Heating HA above its melting temperature, however, caused undesired compositional and structural changes, and upon solidification very limited adherence between the modified ceramic and substrate material occurred under the conditions of this study. The HIP technique, in which the Ti powder substrate and the HA powder coating are sintered together in a high-pressure autoclave, shows great promise for the fabrication of high-quality composite implants. Initial studies have indicated that high-density Ti substrates with a small grain size that are well bonded to a dense HA coating can be produced under optimum conditions. Sintering and densification additives, such as SiO2 powder, do not appear to be necessary. The main drawback to this technique appears to be the reaction of the encapsulating material--whether soda glass, steel, or fused silica--to the HA coating. More extensive testing will necessary to determine the ideal conditions for the HIP technique, as efforts on this technique were discontinued in order to concentrate on the HIP technique, as efforts on this technique were discontinued in order to concentrate on the optimization of the sputter-coating technique so that coated implants for an animal study could be produced on schedule. Based on the results of this study, sputter coating appears to be the method of choice for forming a dense, adherent coating of HA onto a metal substrate.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3382133

Lacefield, W R

1988-01-01

87

Nanocrystalline spin coated sol–gel hydroxyapatite thin films on Ti substrate: Towards potential applications for implants  

Microsoft Academic Search

Sol-gel spin coating is a promising process to obtain hydroxyapatite (HA) thin films. It is an alternative route to the hydroxyapatite deposition techniques usually employed to cover orthopaedic or dental titanium implant surfaces. The sol–gel (SG) parameters leading to a pure and crystalline HA coatings on Ti substrate were determined. They allow to reach a stoichiometric hydroxyapatite composition (ideal Ca\\/P

Adele Carradò; Nathalie Viart

2010-01-01

88

Microsphere Technology  

PubMed Central

Initiation of effective topical therapy as early as possible within the disease course is associated with improved patient experiences and better therapeutic outcomes in most dermatological diseases. Additionally, patient adherence is associated with better outcomes and lower long-term treatment costs, while poor adherence is directly linked to poor treatment results and patient dissatisfaction. Local cutaneous irritation associated with topical drug formulations has been an historical challenge to therapy initiation and adherence. Retinoids and benzoyl peroxide—essential elements of topical acne treatment—are two of the drugs most commonly associated with application-site adverse events. Novel approaches to product formulation incorporating microsphere technology may improve treatment tolerability, encourage adherence, and contribute to better long-term therapeutic outcomes. Microsphere technology eliminates the rapid delivery of high concentrations of active drug to the application site and instead facilitates controlled release of potentially irritating drugs. It is associated with improved treatment outcomes and minimal irritation. Microsphere formulations of topical tretinoin and benzoyl peroxide currently on the market have demonstrated good efficacy and tolerability and are expected to encourage adherence and long-term therapeutic benefit.

2011-01-01

89

High Aspect Ratio Fatty Acid Functionalized Strontium Hydroxyapatite Nanorod and PMMA Bone Cement Filler  

Microsoft Academic Search

High aspect ratio strontium hydroxyapatite nanorod significant enhances the mechanical strength of bioactive bone cement,\\u000a due to its fiber like nature. However, incompatibility between resin matrix and strontium hydroxyapatite (Sr-HA) reduce the\\u000a maximum filler loading and excessive strontium release leads to cytotoxicity problem. The aim of this study is to design a\\u000a high aspect ratio hydroxyapatite nanorod with good resin

W. M. Lam; C. T. Wong; T. Wang; Z. Y. Li; H. B. Pan; W. K. Chan; C. Yang; K. D. K. Luk; M. K. Fong; W. W. Lu

90

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

91

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

92

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

93

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

Microsoft Academic Search

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

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

94

A prospective randomized study comparing electrochemically deposited hydroxyapatite and plasma-sprayed hydroxyapatite on titanium stems  

PubMed Central

Background and purpose Plasma-sprayed hydroxyapatite (HA) is a successful coating for fixation of uncemented femoral stems. There may be alternative coatings with advantages in bone remodeling and transport of bone-active substances. We investigated whether an electrochemically deposited hydroxyapatite, Bonemaster (BM), might be a safe alternative in total hip arthroplasty. Our hypothesis was that the new coating would not be inferior to the conventional one. Patients and methods 50 patients (55 hips) were included. The stem was tapered and porous-coated proximally. On top of the porous coating was either HA or BM. Patients were evaluated postoperatively and after 3, 6, 12, and 24 months to measure fixation by radiostereometric analysis (RSA), bone mineral density by dual-energy X-ray absorptiometry (DXA), and conventional radiography. Clinical evaluation was performed with Harris hip score and Oxford hip score, both preoperatively and after 2 years. Results After 2 years, the stems had subsided 0.25 (HA) and 0.28 (BM) mm and there were no statistically significant differences between the groups in any direction, regarding both migration and rotation. The BM group retained significantly more bone than the HA group in Gruen zone 1 during the first 2 years. The Harris and Oxford hip scores were similar in both groups. Interpretation Electrochemically deposited hydroxyapatite on an uncemented stem does not appear to be inferior to plasma-sprayed HA regarding clinical and radiological results, bone remodeling, and micromotion after 2 years follow-up.

2011-01-01

95

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

96

The biocompatibility of HA thin films deposition on anodized titanium alloys  

Microsoft Academic Search

A thin hydroxyapatite (HA) film was deposited on anodized titanium for the biocompatibility by RF sputtering method. The anodized titanium has improved its bioactivity further by the HA deposition on the anodized titanium surface. TiO2 layer with 0.2~0.5?m diameter pore size was formed on the Ti surface by anodization. HA film deposited surface showed that the pore size and number

Kang Lee; Han-Cheol Choe; Byung-Hoon Kim; Yeong-Mu Ko

2010-01-01

97

Functionally graded coatings of HA–G–Ti composites and their in vivo studies  

Microsoft Academic Search

Hydroxyapatite (HA) was synthesized by the wet chemical method using phosphoric acid (H3PO4) and calcium hydroxide Ca(OH)2 aqueous solutions. The prepared HA powders were fired at various temperatures ranging from 200 to 1200 °C for 2 h to obtain different degrees of crystallinity. The HA powders having different crystallinities were mixed with glass (G) in different weight percentages to form

R. Roop Kumar; S Maruno

2002-01-01

98

Hydroxyapatite Deposited on Flat and porous Ti  

Microsoft Academic Search

Abstract-Formation of porous Ti layer during electrochemical etching in H3PO4 + NH4F, subsequent deposition of calcium-phosphate and corrosion behavior of the materials was described. Anodic etching results in surface roughening with pits diameter in the range of 7-12 ?m. The subsequent cathodic electrochemical treatment, results in hydroxyapatite (HA) deposition. The source of Ca and P were two types of electrolytes:

J. Jakubowicz; G. Adamek

2010-01-01

99

Development of model hydroxyapatite bone scaffolds with multiscale porosity for potential load bearing applications  

NASA Astrophysics Data System (ADS)

Model hydroxyapatite (HA) bone scaffolds consisting of a latticed pattern of rods were fabricated by a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. An optimal HA paste formulation for this method was developed. Local porosity, i.e. microporosity (1--30 mum) and sintering porosity (less than 1 mum), were produced by including polymer microsphere porogens in the HA pastes and by controlling the sintering of the scaffolds. Scaffolds with and without local porosity were evaluated with and without in vitro accelerated degradation. Percent weight loss of the scaffolds and calcium and phosphorus concentrations in solution increased with degradation time. After degradation, compressive strength and modulus decreased significantly for scaffolds with local porosity, but did not change significantly for scaffolds without local porosity. The compressive strength and modulus of scaffolds without local porosity were comparable to human cortical bone and were significantly greater than the scaffolds with local porosity. Micropores in HA disks caused surface pits that increased the surface roughness as compared to non-microporous HA disks. Mouse mesenchymal stem cells extended their cell processes into these microporous pits on HA disks in vitro. ALP expression was prolonged, cell attachment strength increased, and ECM production appeared greater on microporous HA disks compared to non-microporous HA disks and tissue culture treated polystyrene controls. Scaffolds with and without microporosity were implanted in goats bones. Microporous scaffolds with rhBMP-2 increased the percent of the scaffold filled with bone tissue compared to microporous scaffolds without rhBMP-2. Lamellar bone inside scaffolds was aligned near the rods junctions whereas lamellar bone was aligned in a more random configuration away from the rod junctions. Microporous scaffolds stained darkly with toluidine blue beneath areas of contact with new bone. This staining might indicate either extracellular matrix (ECM) in the rods or dye bound to the degrading scaffold. Although the presence of microporous topography alone did not influence bone healing in vivo, micropores were shown to provide tailorability of scaffold mechanical properties, provide a location for the storage and controlled release of a growth factor, and provide a location for bone integration inside the scaffold rods.

Dellinger, Jennifer Gwynne

100

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.

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

2012-01-01

101

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

102

Performance and characterization of a nanophased porous hydroxyapatite for protein chromatography.  

PubMed

Nanophased porous hydroxyapatite beads with particle diameters of 25 microm and 30 microm intended for use in protein and biomolecule separation are characterized with respect to chromatographic characteristics. These particles were produced from a hydroxyapatite gel by a controlled spray process yielding microspheres containing hydroxyapatite nanocrystals. By calcification of the microspheres, nanophased porous hydroxyapatite beads were obtained. As a reference material, ceramic hydroxyapatite Types I and II with a particle diameter of 40 microm was chosen. SEM pictures show that the surface of the nanophased hydroxyapatite is very rough compared to ceramic hydroxyapatite Types I and Type II. The calcium-to-phosphorous ratio of this nanophased hydroxyapatite is 1.6, which is slightly below the theoretical ratio of 1.67 of pure hydroxyapatite. The porosity is greater than 60%. An IgG binding capacity of 60.7 mg/ml for Bio-Rad Type I and 36.0 mg/ml for Type II, 42.0 mg/ml for the nanophased material with 25 microm and 19.7 mg/ml for the nanophased material with 30 microm were observed. The nanophased material with 30 microm had the lowest mass transfer resistancy as indicated by the dependency of the dynamic binding capacity on velocity. It is assumed that the mass transport properties are characterized by a low particle diffusion resistancy or by slight intraparticle convection. The material also showed high selectivity for IgG. When culture supernatant with 5% FCS containing 3 mg/ml was loaded, pure IgG could be eluted by linear gradient with increasing sodium phosphate concentration. This nanophased material comprises a novel stationary phase for IgG separation. PMID:15281111

Jungbauer, Alois; Hahn, Rainer; Deinhofer, Karin; Luo, Ping

2004-08-01

103

Fabrication and formation of bioactive anodic zirconium oxide nanotubes containing presynthesized hydroxyapatite via alternative immersion method  

Microsoft Academic Search

Hydroxyapatite (HA) coating has been widely applied on metallic biomedical implants to enhance their biocompatibility. It has been reported that HA coating can be formed on annealed zirconium with anodic zirconium oxide nanotubular arrays after immersion in simulated biological fluid (SBF) for about 14days. In the present study, we apply an alternative immersion method (AIM) to form presynthesized HA on

Lu-Ning Wang; Jing-Li Luo

2011-01-01

104

Hydroxyapatite kinetic deposition on solid substrates induced by laser-liquid-solid interaction  

Microsoft Academic Search

Hydroxyapatite (HA) is present in the human body as a mineral constituent of the bones and teeth, as well as a major or minor component of kidney stones. HA deposited on different solid substrates can find applications including biomaterials and biosensors. This work deals with the kinetics of the HA growth by applying a novel method of laser-liquid-solid-interaction (LLSI) process

Liliana Pramatarova; Emilia Pecheva; Todor Petrov; Radina Presker; Martin Stutzmann

2005-01-01

105

Effect of particulate morphology on the tensile behaviour of polymer–hydroxyapatite composites  

Microsoft Academic Search

This study examines the effect of powder morphology on the tensile properties of polymer–hydroxyapatite (HA) composites. Experimental findings show that the surface morphology and structural integrity of the HA powder have considerable influence on the tensile property of the composites. The tensile modulus was observed to be dependent on the surface characteristics of the powder. HA powder with rough surfaces

P Cheang; K. A Khor

2003-01-01

106

The process of electrochemical deposited hydroxyapatite coatings on biomedical titanium at room temperature  

Microsoft Academic Search

Calcium phosphate (CaP) ceramics, especially hydroxyapatite (HA), have received much attention and have been clinically applied in orthopaedics and dentistry due to their excellent biocompatibility. Among several methods for preparing HA coating, electrochemical deposition is a relatively new and possible process. However, documented electrochemical processes were conducted at elevated temperature. In this study, uniform HA coatings have been directly deposited

M. C. Kuo; S. K. Yen

2002-01-01

107

Calcium hydroxyapatite fillers.  

PubMed

Calcium hydroxyapatite fillers have unique advantages over other fillers in regards to duration of action and volume of product required for augmentation, especially in the midface and lower face. In this article, we describe our experience with calcium hydroxyapatite fillers and compare them with other available filler products. PMID:22205523

Tansavatdi, Kristina; Mangat, Devinder S

2011-12-01

108

Thermalstability and sintering behaviour of hydroxyapatite nanopowders  

Microsoft Academic Search

Hydroxyapatite (HA)\\u000a nanopowders were synthesised following two different precipitation routes:\\u000a (a) from calcium nitrate and diammonium hydrogen phosphate solutions and (b)\\u000a from calcium hydroxide suspension and phosphoric acid solution. The influence\\u000a of precipitation process, concentration, and synthesis temperature on HA particle\\u000a size and morphology, phase composition, thermal stability, and sintering behaviour\\u000a was investigated by means of: thermogravimetry and differential thermal

Alessandra Bianco; Ilaria Cacciotti; Mariangela Lombardi; Laura Montanaro; G. Gusmano

2007-01-01

109

In situ deposition of hydroxyapatite on graphene nanosheets  

SciTech Connect

Graphical abstract: A facile chemical precipitation method is reported for effective in situ deposition of hydroxyapatite on graphene nanosheets. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. Display Omitted Highlights: ? It is a facile and effective method for deposition of HA on GR nanosheets. ? It avoids the use of harmful reducing agents like hydrazine, NaBH{sub 4} etc. ? GR nanosheets were produced using bio-compatible, ethylenediamine. ? The graphitic structure of synthesized GR nanosheets was high ordered. ? The ratio of Ca to P in HA was 1.64, which is close to ratio in natural bone. -- Abstract: Graphene nanosheets were effectively functionalized by in situ deposition of hydroxyapatite through a facile chemical precipitation method. Prior to grafting of hydroxyapatite, chemically modified graphene nanosheets were obtained by the reduction of graphene oxide in presence of ethylenediamine. The resulting hydroxyapatite functionalized graphene nanosheets were characterized by attenuated total reflection IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy and thermogravimetric analysis. These characterization techniques revealed the successful grafting of hydroxyapatite over well exfoliated graphene nanosheets without destroying their structure.

Neelgund, Gururaj M. [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States)] [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States); Oki, Aderemi, E-mail: aroki@pvamu.edu [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States)] [Department of Chemistry, Prairie View A and M University, Prairie View, TX 77446 (United States); Luo, Zhiping [Microscopy and Imaging Center and Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843 (United States)] [Microscopy and Imaging Center and Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843 (United States)

2013-02-15

110

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

Microsoft Academic Search

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

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

2004-01-01

111

Comparative study of hydroxyapatite and octacalcium phosphate coatings deposited on metallic implants by PLD method  

Microsoft Academic Search

The aim of the presented study was an analysis of two apatite coatings: hydroxyapatite (HA) and octacalcium phosphate (OCP)\\u000a as coatings materials for metallic implants. Both layers were deposited by means of the PLD method. As a target material,\\u000a synthetic, powdered and pressed hydroxyapatite was used. HA was deposited on 316L steel substrate in two temperature ranges\\u000a for obtaining different

W. Mróz; A. Bombalska; B. Budner; S. Burdynska; M. Jedynski; A. Prokopiuk; E. Menaszek; A. ?cis?owska-Czarnecka; A. Niedzielska; K. Niedzielski

2010-01-01

112

Experimental design of plasma spraying and laser treatment of hydroxyapatite coatings  

Microsoft Academic Search

Plasma spray process of hydroxyapatite (Ca10(PO4)6(OH)2, HA) followed by laser treatment of obtained coatings were optimized by an advanced statistical planning of experiments. The full factorial design of 24 experiments was used to find effects of four principal parameters, i.e. electric power, plasma forming gas composition, carrier gas flow rate and laser power density onto microstructure of hydroxyapatite (HA) coatings

S. Dyshlovenko; C. Pierlot; L. Pawlowski; R. Tomaszek; P. Chagnon

2006-01-01

113

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

NASA Astrophysics Data System (ADS)

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

Joughehdoust, Sedigheh; Manafi, Sahebali

2011-12-01

114

In situ fabrication of alendronate-loaded calcium phosphate microspheres: controlled release for inhibition of osteoclastogenesis.  

PubMed

Bioabsorbable calcium phosphate (CaP) microspheres that can incorporate alendronate (ALD) through an in situ loading process and can control the ALD release rate have been described. ALD loading into CaP microspheres could be accomplished by emulsification (water-in-oil) and a subsequent CaP nucleation/growth process within the water droplets, which was initiated by a urea-mediated solution precipitation technique. ALD-loaded microspheres with a mean size range of 163-195 ?m were obtained in a spherical shape. Inductively coupled plasma mass spectroscopy (ICP-MS), spectrophotometric analysis, and thermogravimetric analysis (TGA) showed that the amount of ALD loaded into the microspheres increased when the ALD feed content increased. Energy-dispersive X-ray spectroscopy (EDX) analysis revealed that the in situ loading process enabled the ALD loading throughout the microspheres. X-Ray diffraction (XRD) analysis demonstrated that crystalline hydroxyapatite (HAp) and amorphous CaP phases coexisted within the microspheres. In addition, the increased loading of ALD resulted in a larger proportion of the amorphous CaP phase within the microspheres. The ALD release rate could be controlled depending on the dissolution rate of microspheres, and ALD could be released over a period of 40 days. The evaluation of the biological activity showed that ALD-loaded CaP microspheres directly blocked osteoclast formation by releasing ALD to monocytic precursor cells and effectively inhibiting their differentiation into osteoclasts. PMID:20600398

Kim, Chan Woo; Yun, Young-Pil; Lee, Hong Jae; Hwang, Yu-Shik; Kwon, Il Keun; Lee, Sang Cheon

2010-10-01

115

Zinc and Carbonate Co-Substituted Nano-Hydroxyapatite  

NASA Astrophysics Data System (ADS)

Synthesis of Zn or CO32- substituted nano-hydroxyapatite (HA) and its physico-chemical properties have been well documented. However, the effects of the simultaneous substitution of Zn and CO32- in nano-HA have not been reported. In the present study, Zn and CO32- substitutions in nano HA independently and concurrently have been done by wet precipitation method and characterized by XRD and FT-IR for its phase purity and chemical homogeneity. Further modulations of the bioactivity and thermal stability of HA due to the substitutions have been studied.

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

2011-07-01

116

Novel nanostructured hydroxyapatite coating for dental and orthopedic implants  

NASA Astrophysics Data System (ADS)

A novel hybrid coating process, combining NanoSpray® (built on electrostatic spray coating) technology with microwave sintering process, was developed for synthesizing hydroxyapatite- (HA-) based nanostructured coating with favorable properties for dental and orthopedic implants. Specifically, HA nanoparticles were deposited on commercially pure titanium substrates using NanoSpray technique to produce the HA coating, which was then sintered in a microwave furnace under controlled conditions. The study showed that the use of NanoSpray followed by microwave sintering results in nanoscale HA coating for dental/orthopedic application.

Liu, Huinan; Jiang, Wenping; Malshe, Ajay

2009-09-01

117

Effect of powder calcination on the sintering of hydroxyapatite.  

PubMed

The sintering behaviour of synthesized HA powder that was calcined at various temperatures ranging from 700 degrees C to 1000 degrees C was investigated in terms of phase stability, bulk density, Young's modulus and Vickers hardness. The calcination treatment resulted in higher crystallinity of the starting HA powder. Decomposition of HA phase to form secondary phases was not observed in all the calcined powders. The results also indicated that powder calcination (up to 900 degrees C) prior to sintering has negligible effect on the sinterability of the HA compacts. However, powder calcined at 1000 degrees C was found to be detrimental to the properties of sintered hydroxyapatite bioceramics. PMID:19024997

Tan, C Y; Ramesh, S; Aw, K L; Yeo, W H; Hamdi, M; Sopyan, I

2008-07-01

118

Enhanced osteoblast response to a polymethylmethacrylate–hydroxyapatite composite  

Microsoft Academic Search

Hydroxyapatite (HA)-reinforced polymers have been proposed as a method of improving the biological properties of bone cements and implant materials. For example, bone cements based on polymethylmethacrylate (PMMA) have long been used to secure orthopedic implants to the skeleton. This composite could also be used as a polished coating on other materials or in bulk form, shaped or molded, to

Amr M. Moursi; Alissa V. Winnard; Phillip L. Winnard; John J. Lannutti; Robert R. Seghi

2002-01-01

119

Nanostructured hydroxyapatite powders produced by a flame-based technique  

Microsoft Academic Search

In this work we reported the production of hydroxyapatite (HA) powder, one of the most studied calcium phosphates in the bioceramics field, using a cost-effective apparatus, composed by three major components: the atomization device, the pilot and main flames and finally the powder collector system. Calcium acetate and ammonium phosphate, diluted in ethanol and water, were used as salts in

R. M. Trommer; L. A. Santos; C. P. Bergmann

2009-01-01

120

Synthesis of Carbon Nanofibers on Hydroxyapatite by Flame Deposition  

Microsoft Academic Search

Flame deposition was used to grow high quality carbon nanofibers (CNFs) on the hydroxyapatite (HA) using methanol as carbon source. The HA was activated with Fe-compound by a dip coating. These CNFs were purified by acid leaching. The as-produced and purified CNFs were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy, and Raman spectroscopy.

Sumit Pramanik; Kamal K. Kar

2011-01-01

121

Hydroxyapatite\\/bacterial cellulose composites synthesized via a biomimetic route  

Microsoft Academic Search

In this work, biomimetic precipitation of hydroxyapatite (HA) from simulated body fluid (SBF) on bacterial cellulose (BC) was studied. BC was firstly chemically modified by soaking in 0.1 M CaCl2 solution at 37 °C prior to biomimetic mineralization. The resulting HA\\/BC composites were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy

L. Hong; Y. L. Wang; S. R. Jia; Y. Huang; C. Gao; Y. Z. Wan

2006-01-01

122

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

123

Fabrication, chemical composition change and phase evolution of biomorphic hydroxyapatite  

Microsoft Academic Search

Biomorphous, highly porous hydroxyapatite (HA) ceramics have been prepared by a combination of a novel biotemplating process\\u000a and a sol–gel method, using natural plants like cane and pine as biotemplates. A HA sol was first synthesized from triethylphosphate\\u000a and calcium nitrate used as the phosphorus and calcium precursors, respectively, and infiltrated into the biotemplates, and\\u000a subsequently they were sintered at

Junmin Qian; Yahong Kang; Wei Zhang; Zhe Li

2008-01-01

124

Hydroxyapatite Deposition Disease.  

National Technical Information Service (NTIS)

Hydroxyapatite deposition disease (HADD), a disease most commonly found in middle-aged individuals, is characterized by deposition of calcium phosphate crystals in periarticular tissues. The deposits frequently occur in tendons near their osseous attachme...

D. P. Beall J. Q. Ly L. Folio S. J. Upton

2006-01-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

126

Selective adsorption of porcine-amelogenins onto hydroxyapatite and their inhibitory activity on hydroxyapatite growth in supersaturated solutions  

Microsoft Academic Search

Summary  The selective adsorption of amelogenins onto synthetic hydroxyapatite (HA) and their inhibitory activity on the seeded HA\\u000a crystal growth were investigated using enamel proteins obtained from the outer layer of immature porcine-enamel (soft, cheeselike\\u000a in consistency) of developing permanent incisors. Special interests were paid to the effect of a postsecretory degradation\\u000a of the original amelogenin(s) on their adsorption and inhibitory

T. Aoba; M. Fukae; T. Tanabe; M. Shimizu; E. C. Moreno

1987-01-01

127

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

Microsoft Academic Search

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

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

2011-01-01

128

Electrophoretic deposition of HA\\/MWNTs composite coating for biomaterial applications  

Microsoft Academic Search

A composite coating of hydroxyapatite (HA)\\/multi-walled carbon nanotubes (MWNTs) has been fabricated by electrophoretic deposition\\u000a (EPD). The nano powders of HA and MWNTs were dispersed in ethanol with total concentration of 0.005 g\\/mL and MWNTs 20% and\\u000a 30% contents (wt). And the pH value of suspension was adjusted in a range from 4 to 5. After stabilization the mixture was\\u000a ultrasonically

Changjian Lin; Huijuan Han; Fang Zhang; Aimin Li

2008-01-01

129

Antimicrobial and osteogenic properties of a hydrophilic-modified nanoscale hydroxyapatite coating on titanium  

Microsoft Academic Search

Hydroxyapatite (HA)-coated titanium (Ti) is commonly used for implantable medical devices. This study examined in vitro osteoblast gene expression and antimicrobial activity against early and late colonizers of supra-gingival plaque on nanoscale HA-coated Ti prepared by discharge in a physiological buffered solution. The HA-coated Ti surface showed super-hydrophilicity, whereas the densely sintered HA and Ti surfaces alone showed lower hydrophilicity.

Asuka Murakami; Takafumi Arimoto; Dai Suzuki; Misato Iwai-Yoshida; Fukunaga Otsuka; Yo Shibata; Takeshi Igarashi; Ryutaro Kamijo; Takashi Miyazaki

130

First principles study of hydroxyapatite surface.  

PubMed

The biomineral hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is the main mineral constituent of mammal bone. We report a theoretical investigation of the HA surface. We identify the low energy surface orientations and stoichiometry under a variety of chemical environments. The surface most stable in the physiologically relevant OH-rich environment is the OH-terminated (1000) surface. We calculate the work function of HA and relate it to the surface composition. For the lowest energy OH-terminated surface we find the work function of 5.1 eV, in close agreement with the experimentally reported range of 4.7 eV-5.1 eV [V. S. Bystrov, E. Paramonova, Y. Dekhtyar, A. Katashev, A. Karlov, N. Polyaka, A. V. Bystrova, A. Patmalnieks, and A. L. Kholkin, J. Phys.: Condens. Matter 23, 065302 (2011)]. PMID:23902010

Slepko, Alexander; Demkov, Alexander A

2013-07-28

131

First principles study of hydroxyapatite surface  

NASA Astrophysics Data System (ADS)

The biomineral hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is the main mineral constituent of mammal bone. We report a theoretical investigation of the HA surface. We identify the low energy surface orientations and stoichiometry under a variety of chemical environments. The surface most stable in the physiologically relevant OH-rich environment is the OH-terminated (1000) surface. We calculate the work function of HA and relate it to the surface composition. For the lowest energy OH-terminated surface we find the work function of 5.1 eV, in close agreement with the experimentally reported range of 4.7 eV-5.1 eV [V. S. Bystrov, E. Paramonova, Y. Dekhtyar, A. Katashev, A. Karlov, N. Polyaka, A. V. Bystrova, A. Patmalnieks, and A. L. Kholkin, J. Phys.: Condens. Matter 23, 065302 (2011)].

Slepko, Alexander; Demkov, Alexander A.

2013-07-01

132

Thermal Diffusivity in Bone and Hydroxyapatite  

NASA Astrophysics Data System (ADS)

We report thermal diffusivity measurements in bull bone and commercial hydroxyapatite (HA), both in powder form, in order to determinate the thermal compatibility between these materials. Besides this, we report a comparison between these measured values and those of metallic samples frequently used in implants, as high purity titanium and stainless steel. Our results show a good thermal compatibility (74%) between HA and bone, both in powder form. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications.

Calderón, A.; Peña Rodríguez, G.; Muñoz Hernández, R. A.; Díaz Gongora, J. A. I.; Mejia Barradas, C. M.

2004-09-01

133

Electrical characterization of hydroxyapatite-based bioceramics.  

PubMed

This paper studies the AC conductivity and permittivity of hydroxyapatite (HA)-based ceramics from 0.1 Hz-1 MHz at temperatures from room temperature to 1000 degrees C. HA-based ceramics were prepared either as dense ceramics or in porous form with interconnected porosity and were sintered in either air or water vapour. Samples were thermally cycled to examine the influence of water desorption on AC conductivity and permittivity. Surface-bound water was thought to contribute to conductivity for both dense and porous materials at temperatures below 200 degrees C. At temperatures below 700 degrees C the permittivity and AC conductivity of HA was also influenced by the degree of dehydration and thermal history. At higher temperatures (700-1000 degrees C), bulk ionic conduction was dominant and activation energies were of the order of approximately 2 eV, indicating that hydroxyl ions are responsible for conductivity. PMID:18829403

Gittings, J P; Bowen, C R; Dent, A C E; Turner, I G; Baxter, F R; Chaudhuri, J B

2009-02-01

134

Importance of nucleation in transformation of octacalcium phosphate to hydroxyapatite.  

PubMed

Octacalcium phosphate (OCP) is regarded as an in vivo precursor of hydroxyapatite (HA). It is important to understand the mechanism of transformation of OCP to HA in order to reveal the mechanism of mineralization and help in the development of artificial bone-repairing materials. Herein, we have examined the behavior of OCP in a simulated body fluid (SBF) and pure water. The OCP particles immersed in the SBF at 37°C did not transform to HA even after 720h of immersion, though the particles showed crystal growth. In distilled water at 60°C, the OCP particles transformed to HA but the unreactive period was observed. Although the immersed solution became supersaturated with HA within 12h of immersion, the OCP was not transformed in the first 36h of immersion. These results indicate that the nucleation of HA is the rate-determining step in the transformation of OCP to HA. PMID:24857473

Ito, Natsuko; Kamitakahara, Masanobu; Yoshimura, Masahiro; Ioku, Koji

2014-07-01

135

Hydroxyapatite crystal growth on calcium hydroxyapatite ceramics  

Microsoft Academic Search

Calcium hydroxyapatite (Ca-HAP) ceramics containing tricalcium phosphate (TCP) were soaked in three solutions: phosphate buffer, tris buffer, and simulated body fluid (SBF). Petal-like crystals of Ca-HAP were deposited on the Ca-HAP ceramics when (i) Ca-HAP ceramics contained a-TCP, (ii) the soaking solution contained phosphate ion and (iii) the pH of soaking solution was higher than 7.3. These conditions facilitate the

Masayuki Asada; Yoshinari Miura; Akiyoshi Osaka; Katsutoshi Oukami; Seishiro Nakamura

1988-01-01

136

Fabrication of HA\\/PHBV composite scaffolds through the emulsion freezing\\/freeze-drying process and characterisation of the scaffolds  

Microsoft Academic Search

Biodegradable polymer-based scaffolds containing osteoconductive hydroxyapatite (HA) particles can be very useful for bone\\u000a tissue engineering. In this investigation, HA nanoparticles were incorporated in poly(hydroxybutyrate-co-valerate) (PHBV) polymer to fabricate osteoconductive composite scaffolds. PHBV and HA\\/PHBV scaffolds were made using an\\u000a emulsion freezing\\/freeze-drying technique. The scaffolds produced were subsequently characterized using several techniques.\\u000a It was found that the scaffolds were highly

Naznin Sultana; Min Wang

2008-01-01

137

Converting ultrasonic induction heating deposited monetite coating to Na-doped HA coating on H 2O 2-treated C\\/C composites by a two-step hydrothermal method  

Microsoft Academic Search

a monetite coating on H2O2-treated C\\/C composites was prepared by ultrasonic induction heating (UIH) technology. Subsequently, this coating was subjected to an ammonia hydrothermal treatment to form a undoped hydroxyapatite (U-HA) coating. Finally, the as-prepared U-HA coating was placed in a NaOH solution and hydrothermally treated to produce the other hydroxyapatite (Na-HA) coating. The structure, morphology and chemical composition of

Xiong Xin-Bo; Hung Jian-Feng; Zeng Xie-Rong; Chu Cen-Cen

2011-01-01

138

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

139

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

140

Effect of gun current on the microstructure and crystallinity of plasma sprayed hydroxyapatite coatings  

Microsoft Academic Search

Hydroxyapatite (HA) is a bioactive material because its chemical structure is close to the natural bone. Its bioactive properties make it attractive material in biomedical applications. Gas tunnel type plasma spraying (GTPS) technique was employed in the present study to deposit HA coatings on SUS 304 stainless steel substrate. GTPS is composed of two plasma sources: gun which produces internal

M. F. Morks; A. Kobayashi

2007-01-01

141

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

Microsoft Academic Search

Calcium hydroxyapatite (HA) is the main chemical constituent of bone. When replacement hip joints are coated with this chemical, the body may be more likely to accept the artificial joint, forming new bone that bonds the joint to the original leg bone. HA deposited by laser ablation in vacuum adheres to the substrate better at high temperatures of up to

T. Chang; M. A. Havstad

1995-01-01

142

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

143

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

144

Hydroxyapatite with environmental applications  

NASA Astrophysics Data System (ADS)

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 Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+ and at fixed pH of 5. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp_5 via the adsorption of Pb2+ ions followed by a cation exchange reaction. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb2+ ions from aqueous solution.

Popa, C. L.; Ciobanu, C. S.; Petre, C. C.; Motelica-Heino, M.; Iconaru, S. L.; Jiga, G.; Predoi, D.

2014-05-01

145

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.

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

2012-01-01

146

Surface modification for titanium implants by hydroxyapatite nanocomposite.  

PubMed

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

147

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.

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

2013-01-01

148

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

149

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

150

Synthesis and in vitro evaluation of hydroxyapatite with controlled morphology  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

151

Posterolateral spinal fusion with ostegenesis induced BMSC seeded TCP/HA in a sheep model.  

PubMed

Autogenous bone graft is the gold standard for fusion procedure. However, pain at donor site and inconsistent outcome have left a surgeon to venture into some other technique for spinal fusion. The objective of this study was to determine whether osteogenesis induced bone marrow stem cells with the combination of ceramics granules (HA or TCP/HA), and fibrin could serve as an alternative to generate spinal fusion. The sheep's bone marrow mesenchymal stem cells (BMSCs) were aspirated form iliac crest and cultured for several passages until confluence. BMSCs were trypsinized and seeded on hydroxyapatite scaffold (HA) and tricalcium phosphate/hydroxyapatite (TCP/HA) for further osteogenic differentiation in the osteogenic medium one week before implantation. Six adult sheep underwent three-level, bilateral, posterolateral intertransverse process fusions at L1-L6. Three fusion sites in each animal were assigned to three treatments: (a) HA constructs group/L1-L2, (b) TCP/HA constructs group/L2-L3, and (c) autogenous bone graft group/L5-L6. The spinal fusion segments were evaluated using radiography, manual palpation, histological analysis and scanning electron microscopy (SEM) 12 weeks post implantation. The TCP/HA constructs achieved superior lumbar intertransverse fusion compared to HA construct but autogenous bone graft still produced the best fusion among all. PMID:24630213

Shamsul, B S; Tan, K K; Chen, H C; Aminuddin, B S; Ruszymah, B H I

2014-04-01

152

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

153

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

154

Nanophase hydroxyapatite coatings for dental and orthopedic applications  

NASA Astrophysics Data System (ADS)

In order to improve dental and orthopedic implant performance, the objective of this study was to synthesize nanocrystalline hydroxyapatite (HA) powders to coat metals (specifically, titanium and tantalum). Precipitated HA powders were either sintered in order to produce UltraCaP HA (or microcrystalline size HA) or were treated hydrothermally to produce nanocrystalline HA. Some of the UltraCaP and nanocrystalline HA powders were doped with yttrium (Y) since previous in vitro studies demonstrated that Y-doped HA in bulk improved osteoblast (or bone-forming cell) function over undoped HA. The nanocrystalline HA powders were also mixed with nanophase titania powders because previous studies demonstrated that titania/HA composite coatings increased coating adhesive strength and HA nucleation. These powders were then deposited onto titanium by a novel room-temperature process, called IonTiteT(TM). The results demonstrated that the chemical properties and crystallite size of the original HA powders were maintained in the coatings. More importantly, in vitro studies showed increased osteoblast (bone-forming cell) adhesion on the single phase nanocrystalline HA and nano-titania/HA coatings compared to traditionally used plasma-sprayed HA coatings and uncoated metals. Results further demonstrated greater amounts of calcium deposition by osteoblasts cultured on nanocrystalline HA coatings compared to UltraCaP coatings and conventionally used plasma-sprayed HA coatings. To elucidate mechanisms that influenced osteoblast functions on the HA coatings, the amount of proteins (fibronectin and vitronectin) onto the HA powders and the adsorbed fibronectin conformation were investigated. Exposure of cell integrin binding domains (in fibronectin III10 segments) was greater in fibronectin adsorbed onto 1.2 mole% Y-doped UltraCaP HA coatings compared to nanocrystalline HA coatings tested. However, 1.2 mole% Y-doped UltraCaP HA coatings did not increase mineralization by osteoblasts compared to the nanocrystalline HA coatings. These results suggested that the availability of integrin binding domains in fibronectin did not correlate to enhanced mineralization by osteoblasts on nanocrystalline HA coatings. Lastly, undoped nanocrystalline HA coatings were studied using a well-established rat calvaria in vivo. Histological analysis showed that nanocrystalline HA coated on tantalum scaffolds increased bone and fibrous tissue infiltration into the scaffolds while uncoated and UltraCaP HA coated scaffolds did not after as early as 6 weeks. In summary, these results encourage further studies on nanocrystalline IonTiteTM HA coatings on various metals for orthopedic and dental applications.

Sato, Michiko

155

Preparation and properties of nano-hydroxyapatite\\/chitosan\\/carboxymethyl cellulose composite scaffold  

Microsoft Academic Search

Carboxymethyl cellulose was first incorporated into nano-hydroxyapatite\\/chitosan to obtain a novel composite of nano-hydroxyapatite\\/chitosan\\/carboxymethyl cellulose (n-HA\\/CS\\/CMC) as a three-dimensional scaffolds by freeze-drying. The surface morphology and properties of the scaffold were investigated by infrared absorption spectra (IR), X-ray diffraction (XRD), scanning electron microscope (SEM), mechanical testing and soaking in simulated body fluids (SBF) soaking. The results showed that strong chemical

Liuyun Jiang; Yubao Li; Xuejiang Wang; Li Zhang; Jiqiu Wen; Mei Gong

2008-01-01

156

Histomorphological study of bone response to hydroxyapatite coating on stainless steel  

Microsoft Academic Search

Bone response to hydroxyapatite coating on stainless steel has not been so extensively tested in animals as it happened for other metallic substrate, like Ti6Al4V. For this reason, authors performed an in vivo histomorphological electron microscopic study of hydroxyapatite coating on duplex stainless steel cylinders, to gather further evidences on the characters of bone apposition at the interface. Sixteen HA-coated

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

2003-01-01

157

Novel selenium-doped hydroxyapatite coatings for biomedical applications.  

PubMed

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

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

2013-03-01

158

Pickering-type water-in-oil-in-water multiple emulsions toward multihollow nanocomposite microspheres.  

PubMed

Multihollow hydroxyapatite (HAp)/poly(L-lactic acid) (PLLA) nanocomposite microspheres were readily fabricated by solvent evaporation from a "Pickering-type" water-in-(dichloromethane solution of PLLA)-in-water multiple emulsion stabilized with HAp nanoparticles. The multiple emulsion was stabilized with the aid of PLLA molecules used as a wettability modifier for HAp nanoparticles, although HAp nanoparticles did not work solely as particulate emulsifiers for Pickering-type emulsions consisting of pure dichloromethane and water. The interaction between PLLA and HAp nanoparticles at the oil-water interfaces plays a crucial role toward the preparation of stable multiple emulsion and multihollow microspheres. PMID:20712353

Maeda, Hayata; Okada, Masahiro; Fujii, Syuji; Nakamura, Yoshinobu; Furuzono, Tsutomu

2010-09-01

159

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

160

Polarization of hydroxyapatite: influence on osteoblast cell proliferation.  

PubMed

Hydroxyapatite (HA) has been used clinically to treat bone defects. However, modifications of the surface properties of HA could improve and control bone matrix deposition and localized host tissue integration. The aim of this study was to investigate the effect of developing a surface charge on HA discs with respect to osteoblast activity in vitro. HA discs (12 mm x 2 mm) were sintered in either air or water vapour. The HA discs were then electrically polarized (positive and negative surfaces) or non-polarized (controls) and seeded with MC3T3-E1 cells. Polarized HA sintered in water vapour was shown to retain six times more charge than polarized HA sintered in air. Picogreen analysis demonstrated that at 4h cell number was significantly higher on the negatively and positively charged HA surface (water sintered) in comparison to the non-charged water and air-sintered HA controls. At 7 days there was a significant increase in cell number on the negatively charged HA (air sintered) sample in comparison to the negatively charged water vapour sintered HA sample and the non-charged water vapour sintered control sample. Also at 7 days, the picogreen data showed a significant increase in cell number on the positively charged water-treated HA sample in comparison to both the air- and water-treated HA non-charged control HA samples. An alamarBlue assay at 7 days demonstrated significant cell metabolic activity on the charged surfaces (both positive and negative) in comparison to the non-charged HA and the tissue culture plastic controls. This study demonstrated that all of the HA discs tested supported cell viability/attachment. However, cell attachment/proliferation/metabolic activity was significantly increased as a result of developing a charge on the HA surface. PMID:19914408

Kumar, D; Gittings, J P; Turner, I G; Bowen, C R; Hidalgo-Bastida, L A; Bastida-Hidalgo, A; Cartmell, S H

2010-04-01

161

Iron(III) and manganese(II) substituted hydroxyapatite nanoparticles: Characterization and cytotoxicity analysis  

NASA Astrophysics Data System (ADS)

Calcium hydroxyapatite (HA) is the main inorganic component of natural bones and can bond to bone directly in vivo. Thus HA is widely used as coating material on bone implants due to its good osteoconductivity and osteoinductivity. Metal ions doped HA have been used as catalyst or absorbents since the ion exchange method has introduced new properties in HA which are inherent to the metal ions. For example, Mn2+ ions have the potential to increase cell adhesion while Fe3+ ions have magnetic properties. Here, Fe(III) substituted hydroxyapatite (Fe-HA) and Mn(II) substituted hydroxyapatite (Mn-HA) were produced by wet chemical method coupled with ion exchange mechanism. Compared with pure HA, the colour of both Fe-HA and Mn-HA nanoparticles changed from white to brown and pink respectively. The intensity of the colours increased with increasing substitution concentrations. XRD patterns showed that all samples were single phased HA while the FTIR spectra revealed all samples possessed the characteristic phosphate and hydroxyl adsorption bands of HA. However, undesired adsorption bands of carbonate substitution (B-type carbonated HA) and H2O were also detected, which was reasonable since the wet chemical method was used in the synthesis of these nanoparticles. FESEM images showed all samples were elongated spheroids with small size distribution and of around 70 nm, regardless of metal ion substitution concentrations. EDX spectra showed the presence of Fe and Mn and ICP-AES results revealed all metal ion substituted HA were non-stoichiometric (Ca/P atomic ratio deviates from 1.67). Fe-HA nanoparticles were paramagnetic and the magnetic susceptibility increased with the increase of Fe content. Based on the extraction assay for cytotoxicity test, both Fe-HA and Mn-HA displayed non-cytotoxicity to osteoblast.

Li, Yan; Teck Nam, Chai; Ooi, Chui Ping

2009-09-01

162

Porous scaffolds of polycaprolactone reinforced with in situ generated hydroxyapatite for bone tissue engineering  

Microsoft Academic Search

Polycaprolactone\\/hydroxyapatite (PCL\\/HA) composites were prepared by in situ generation of HA in the polymer solution starting\\u000a from the precursors calcium nitrate tetrahydrate and ammonium dihydrogen phosphate via sol–gel process. Highly interconnected\\u000a porosity was achieved by means of the salt-leaching technique using a mixture of sodium chloride and sodium bicarbonate as\\u000a porogens. Structure and morphology of the PCL\\/HA composites were investigated

Paola Fabbri; Federica Bondioli; Massimo Messori; Cristina Bartoli; Dinuccio Dinucci; Federica Chiellini

2010-01-01

163

Morphologies of hydroxyapatite nanoparticles adjusted by organic additives in hydrothermal synthesis  

Microsoft Academic Search

Properties of hydroxyapatite (HA, Ca10(PO4)6(OH)2), including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of\\u000a particle composition, particle size and morphology. In order to satisfy various applications, well-crystallized pure HA nanoparticles\\u000a were synthesized at moderate temperatures by hydrothermal synthesis, and HA nanoparticles with different lengths were obtained\\u000a by adding organic additives. X-ray diffractometry (XRD)

Hai-bin Zhang; Ke-chao Zhou; Zhi-you Li; Su-ping Huang; Yan-zhong Zhao

2009-01-01

164

Performance improvement of injectable poly(ethylene glycol) dimethacrylate-based hydrogels with finely dispersed hydroxyapatite  

Microsoft Academic Search

Injectable hydrogels are attractive materials for biomedical application. In this work, a chemical mixing technique was developed to promote the dispersion of hydroxyapatite (HA) in injectable poly(ethylene glycol) dimethacrylate (PEGDMA)-based hydrogels. Nano-sized HA particles were distributed homogenously within the organic network, whereby HA crystals were formed in the presence of PEGDMA macromers. In addition, hydrogels were also prepared by physical

Ziyou Zhou; Yongjuan Ren; Dongzhi Yang; Jun Nie

2009-01-01

165

Laminated and functionally graded hydroxyapatite\\/yttria stabilized tetragonal zirconia composites fabricated by spark plasma sintering  

Microsoft Academic Search

Hydroxyapatite (HA) ceramics have been conventionally strengthened and toughened in the form of composites and coatings. New microstructural designs and processing methodologies are still needed for the improvement of the mechanical properties of HA-based ceramics. This study was to prepare laminated and functionally graded HA\\/yttria stabilized tetragonal zirconia (Y-TZP) composites by the relatively new process of spark plasma sintering (SPS).

Hongbo Guo; Khiam Aik Khor; Yin Chiang Boey; Xigeng Miao

2003-01-01

166

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

Microsoft Academic Search

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

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

2004-01-01

167

Fracture of hydroxyapatite coated prostheses: a report of two cases of stem failure in hip hemiarthroplasty  

Microsoft Academic Search

Hydroxyapatite (HA)-coated implants for hemiarthroplasty for fractures of the femoral neck offer the advantages of stable and permanent fixation. Since April 1994, we have treated 562 patients using the JRI Furlong HA-coated hemiarthroplasty system at the Worthing and Southlands Hospitals. Fracture of the fully-HA-coated stainless steel stem was seen in two patients. To our knowledge, this complication has not been

Maneesh Bhatia; John Edge

2004-01-01

168

Gelatin–Chitosan composite capped gold nanoparticles: a matrix for the growth of hydroxyapatite  

Microsoft Academic Search

Growth of hydroxyapatite (HA) on gelatin–chitosan composite capped gold nanoparticles is presented for the first time by employing\\u000a wet precipitation methods and we obtained good yields of HA. Fourier transform infrared spectroscopy (FTIR) spectrum has shown\\u000a the characteristic bands of phosphate groups in the HA. Scanning electron microscopy (SEM) pictures have shown spherical nanoparticles\\u000a with the size in the range

S. S. Liji Sobhana; J. Sundaraseelan; S. Sekar; T. P. Sastry; A. B. Mandal

2009-01-01

169

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

170

Possibilities for strengthening hydroxyapatite ceramics.  

PubMed

Some physics during heating and sintering of powder pressings of hydroxyapatite (HA) under conventional (usual) conditions have been studied. It is revealed that heating and firing of the pressings of a middle-dispersity powder are accompanied by release of gases. The gas release hinders and can stop the shrinkage (sintering). The microhardness is low and has a complicated distribution on the surface and in the volume of ceramics. A slight degassing (drying) of the pressing before sintering heightens the density and improves the microhardness characteristics of the ceramics. The shrinkage stop effect is eliminated in pressings of a fine powder. On the basis of the results, a technique and some methods for quality improvement of ceramics were proposed and approbated. They consisted of the manufacture of samples of a mixture of two powders with different dispersity, use of a press technique with two male dies, thermal treatment of pressing before sintering, and the choice of moderate sintering conditions. The resulting ceramics had a density close to the theoretical, almost homogeneous microhardness distribution in the sample and much higher values of microhardness and compressive strength. PMID:10357137

Zyman, Z Z; Ivanov, I G; Glushko, V I

1999-07-01

171

Zirconia-toughened hydroxyapatite ceramic obtained by wet sintering.  

PubMed

A toughened hydroxyapatite (HA) ceramic has been obtained through the incorporation of magnesia partially stabilized zirconia (Mg-PSZ) under uniaxial pressing and sintering in wet oxygen at 1250 degrees C for 4 h. The powder X-ray diffraction (XRD) patterns and infrared spectra (FT-IR) show that HA is the only calcium phosphate phase present. The composite (MgPSZ-HA) has a density of 94% the theoretical value. The bending strength and the fracture toughness are around 50% higher for Mg-PSZ reinforced than for HA. The grain size and the fracture surface were studied by scanning electron microscopy (SEM). The influence of the Mg-PSZ particles on the fracture mechanism of the HA ceramic is discussed. PMID:15347939

Delgado, J A; Morejón, L; Martínez, S; Ginebra, M P; Carlsson, N; Fernández, E; Planell, J A; Clavaguera-Mora, M T; Rodríguez-Viejo, J

1999-12-01

172

Hydroxyapatite whisker-reinforced polyetherketoneketone bone ingrowth scaffolds.  

PubMed

Hydroxyapatite (HA) whisker-reinforced polyetherketoneketone (PEKK) bone ingrowth scaffolds were prepared and characterized. High levels of porosity (75-90%) and HA whisker reinforcement (0-40 vol.%) were attained using a powder processing approach to mix the HA whiskers, PEKK powder and a NaCl porogen, followed by compression molding at 350-375 degrees Celsius and particle leaching to remove the porogen. The scaffold architecture and microstructure exhibited characteristics known to be favorable for osteointegration. Scaffold porosity was interconnected with a mean pore size in the range 200-300 microm as measured by micro-computed tomography. HA whiskers were embedded within and exposed on the surface of scaffold struts, producing a microscale surface topography, shown by von Kossa staining and scanning electron microscopy. Therefore, HA whisker-reinforced PEKK bone ingrowth scaffolds may be advantageous for orthopedic implant fixation, including interbody spinal fusion. PMID:19665061

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

2010-03-01

173

Selective effects of hydroxyapatite nanoparticles on osteosarcoma cells and osteoblasts.  

PubMed

The effects of hydroxyapatite nanoparticles (HA-NPs) on two kinds of cells, human MG63 cells and the normal osteoblasts were investigated. According to the MTT assay and fluorescent staining assay, it was proved that HA-NPs could inhibit the growth of MG63 cells but slightly support proliferation of the osteoblasts. Meanwhile, transmission electron microscopy (TEM) was employed to observe the ultrastructural alterations of both cells. The TEM results showed that HA-NPs had entered the two kinds of cells. Typical apoptosis was observed in the MG63 cells, especially in the group of 250 ?g/mL with 5 days culture. While no apoptosis could be found in the normal osteoblasts at any concentration group of HA-NPs. Our results suggested that the HA-NPs had selective effects to different kinds of cells: supporting proliferation to the normal bone cells while causing apoptosis to the osteosarcoma cells. PMID:22903597

Qing, Fangzhu; Wang, Zhe; Hong, Youliang; Liu, Ming; Guo, Bo; Luo, Hongrong; Zhang, Xingdong

2012-09-01

174

Reconstruction of goat femur segmental defects using triphasic ceramic-coated hydroxyapatite in combination with autologous cells and platelet-rich plasma  

Microsoft Academic Search

Segmental bone defects resulting from trauma or pathology represent a common and significant clinical problem. In this study, a triphasic ceramic (calcium silicate, hydroxyapatite and tricalcium phosphate)-coated hydroxyapatite (HASi) having the benefits of both HA (osteointegration, osteoconduction) and silica (degradation) was used as a bone substitute for the repair of segmental defect (2cm) created in a goat femur model. Three

Manitha B. Nair; H. K. Varma; K. V. Menon; Sachin J. Shenoy; Annie John

2009-01-01

175

Preparation and characterisation of calcium-phosphate porous microspheres with a uniform size for biomedical applications  

Microsoft Academic Search

In the present work, a novel route for the preparation of porous ceramic microspheres is described. Two ceramic powders, calcium-titanium-phosphate\\u000a (CTP) and hydroxyapatite (HAp), were mixed with a sodium alginate solution that enabled the preparation of spherical particles,\\u000a using the droplet extrusion method combined with ionotropic gelation in the presence of Ca2+. The spherical particles were subsequently sintered, to burn-off

C. C. Ribeiro; C. C. Barrias; M. A. Barbosa

2006-01-01

176

Hydroxyapatite-reinforced collagen tissue engineering scaffolds  

NASA Astrophysics Data System (ADS)

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

Kane, Robert J.

177

The beneficial effect of hydroxyapatite lasts  

PubMed Central

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

2012-01-01

178

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

179

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

180

Arthroscopic treatment of hydroxyapatite deposition in the iliofemoral ligament  

Microsoft Academic Search

The hydroxyapatite(HA) deposition disease is a common disease with articular and periarticular acute pain, and the supraspinatus\\u000a of shoulder joints is the most frequently occuring site. In the case of the disease occurrence around a hip joint, the gluteus\\u000a maximus tendon, the gluteus medius tendon, and the bursa between the gluteus medius and the greater trochanter usually are\\u000a the disease

Myung-Sik Park; Woo-Chull Chung; Hong-Man Cho; Seung-Ryul Lee

2010-01-01

181

Electrophoretic deposition of hydroxyapatite submicron particles at high voltages  

Microsoft Academic Search

Hydroxyapatite (HA) coatings on stainless steel 316L were produced by electrophoretic deposition (EPD) in ethanol at 200, 400, and 800 V during 0.5 to 3 s. The particle size distribution of the starting suspension was 0.275 to 4.88 ?m, with an average size of 1.805 ?m. Submicron particle coatings were obtained and then sintered at 800 °C during 2 h.

P Mondragón-Cortez; G Vargas-Gutiérrez

2004-01-01

182

Novel hydroxyapatite\\/tantalum surface coating for metallic dental implant  

Microsoft Academic Search

The aim of this study was to design and produce a novel surface composite coating on metallic substrate in order to improve the biocompatibility of metallic dental implant and the bone osteointegration simultaneously.Stainless steel 316L (SS) was used as a metallic substrate and a novel double-layer hydroxyapatite\\/tantalum (HA\\/Ta) coating was prepared on it. Tantalum coating was made using physical vapor

M. H. Fathi; F. Azam

2007-01-01

183

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

184

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

PubMed

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

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

2014-08-01

185

Characterization of porous hydroxyapatite.  

PubMed

Hydroxyapatite has been considered for use in the repair of osseous defects for the last 20 years. Recent developments have led to interest in the potential of porous hydroxyapatite as a synthetic bone graft. However, despite considerable activity in this field, regarding assessment of the biological response to such materials, the basic materials characterization is often inadequate. This paper documents the characterization of the chemical composition, mechanical integrity, macro- and microstructure of a porous hydroxyapatite, Endobon (E. Merck GmbH), intended for the bone-graft market. Specimens possesed a range of apparent densities from 0.35 to 1.44 g cm(-3). Chemical analysis demonstrated that the natural apatite precursor of Endobon was not converted to pure hydroxyapatite, but retained many of the ionic substituents found in bone mineral, notably carbonate, sodium and magnesium ions. Investigation of the microstructure illustrated that the struts of the material were not fully dense, but had retained some traces of the network of osteocyte lacunae. Macrostructural analysis demonstrated the complex inter-relationship between the structural features of an open pore structure. Both pore size and connectivity were found to be inversely dependent on apparent density. Furthermore, measurement of pore aspect ratio and orientation demonstrated a relationship between apparent density and the degree of macrostructural anisotropy within the specimens, while, it was also noted that pore connectivity was sensitive to anisotropy. Compression testing demonstrated the effect of apparent density and macrostructural anisotropy on the mechanical properties. An increase in apparent density from 0.38 to 1.25 g cm(-3) resulted in increases in ultimate compressive stress and compressive modulus of 1 to 11 MPa and 0.2 to 3.1 GPa, respectively. Furthermore, anisotropic high density (> 0.9 g cm(-3)) specimens were found to possess lower compressive moduli than isotropic specimens with equivalent apparent densities. These results underline the importance of full structural and mechanical characterization of porous ceramic implant materials. PMID:15348161

Hing, K A; Best, S M; Bonfield, W

1999-03-01

186

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.

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

2014-01-01

187

Comparing microspheres with different internal phase of polyelectrolyte as local drug delivery system for bone tuberculosis therapy.  

PubMed

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

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

2014-01-01

188

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

189

High protein adsorptive capacity of amino acid-functionalized hydroxyapatite.  

PubMed

Charged functional groups present on the surface of biomaterials play an important role to regulate the affinity and attachment of macromolecules, including proteins, on the surface of biomaterials. In this study, the protein adsorptive capacity of hydroxyapatite (HA) was regulated by introducing different amino acids during the precipitation of HA. After incubation of HA samples in 5000 ?g/mL lysozyme solution at pH 7.4 for 24 h, unmodified HA adsorbed 0.886 mg/m(2) of lysozyme while amino acid-functionalized HA (AA-HA) particles demonstrated higher adsorption capacity ranging from 1.090 to 1.680 mg/m(2). Incorporation of amino acids with longer side chain lengths decreased the crystallinity and increased the negative value of the surface charge of HA particles. The specific surface areas were significantly increased in the presence of amino acids. Protein loading capacity onto AA-HA was further enhanced by regulating the pH of working solution whereby the protein adsorption rate increased with decreasing the pH, while reverse trend obtained in unmodified HA. The study demonstrated that the amount of adsorbed lysozyme onto AA-HA particles was correlated with the particles' surface charges. PMID:23008163

Lee, Wing-Hin; Loo, Ching-Yee; Zavgorodniy, Alexander V; Rohanizadeh, Ramin

2013-03-01

190

Effect of Hydrothermal Treatment on Sinterability of Hydroxyapatite  

SciTech Connect

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

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

2006-05-15

191

First principles study of biomineral hydroxyapatite  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is one of the most abundant materials in mammal bone. It crystallizes within the spaces between the tropocollagen chains and strengthens the bone tissue. The mineral content of human bone increases with age reaching a maximum value from which it starts to decrease leading to diseases such as osteomalacia. Therefore, an emergent application of this study is bone repair and the production of synthetic bone. Despite its importance, little is known about the growth of HA crystallites in bones. Nor is it well understood how the HA attaches to protein chains and interacts with the surrounding aqueous solution. Using density functional theory (DFT) we calculate the theoretical ground state structure, electronic and vibration properties of hexagonal HA. We find several low energy structures and analyze the energy barriers for spontaneous phase transitions. We calculate the phonon density of states and study the surface energetics for different orientations. We identify the surfaces with highest reactivity using the frontier orbital approach and analyze interactions between these surfaces and water molecules/amino acids.

Slepko, Alexander

2010-03-01

192

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

193

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

194

Bioactive inorganic-materials/alginate composite microspheres with controllable drug-delivery ability.  

PubMed

Alginate microspheres are considered a promising material as a drug carrier in bone repair because of excellent biocompatibility, but their main disadvantage is low drug entrapment efficiency and noncontrollable release. The aim of this study was to investigate the effect of incorporating mesoporous bioglass (MBG), nonmesoporous bioglass (BG), or hydroxyapatite (HAp) into alginate microspheres on their drug-loading and release properties. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and atomic emission spectroscopy (AES) were used to analyze the composition, structure, and dissolution of bioactive inorganic materials and their microspheres. Dexamethasone (DEX)-loading and release ability of four microspheres were tested in phosphate buffered saline with varying pH. Results showed that the drug-loading capacity was enhanced with the incorporation of bioactive inorganic materials into alginate microspheres. The MBG/alginate microspheres had the highest drug loading ability. DEX release from alginate microspheres correlated to the dissolution of MBG, BG, and HAp in PBS, and that the pH was an efficient factor in controlling the DEX release; a high pH resulted in greater DEX release, whereas a low pH delayed DEX release. In addition, MBG/alginate, BG/alginate, and HAp/alginate microspheres had varying apatite-formation and dissolution abilities, which indicate that the composites would behave differently with respect to bioactivity. The study suggests that microspheres made of a composite of bioactive inorganic materials and alginate have a bioactivity and degradation profile which greatly improves their drug delivery capacity, thus enhancing their potential applications as bioactive filler materials for bone tissue regeneration. PMID:20225253

Wu, Chengtie; Zhu, Yufang; Chang, Jiang; Zhang, Yufeng; Xiao, Yin

2010-07-01

195

Experimental study of nano-HA artificial bone with different pore sizes for repairing the radial defect  

Microsoft Academic Search

The purpose of this study was to examine the repairing ability of nano-hydroxyapatite (nano-HA) artificial bone with different\\u000a pore sizes. Animal models of bone defects were created in both radii of 60 New Zealand white rabbits. The bone defects in\\u000a A, B, and C groups were repaired with nano-HA artificial bone with three different pore sizes while those in group

Weimin Zhu; Jiande Xiao; Daping Wang; Jianquan Liu; Jianyi Xiong; Lijun Liu; Xiaojun Zhang; Yanjun Zeng

2009-01-01

196

High-energy ion beam implantation of hydroxyapatite thin films grown on TiN and ZrO 2 inter-layers by pulsed laser deposition  

Microsoft Academic Search

Current drawbacks in the hydroxyapatite (HA) thin film production for applications in bone surgery are their poor mechanical strength and limited adherence. This paper presents the ion beam implantation technique as an efficient method to improve the mechanical characteristics of HA films. Crystalline films of HA were grown by pulsed laser deposition, using a KrF* excimer laser (?=248 nm, ??20

V. Nelea; H. Pelletier; P. Mille; D. Muller

2004-01-01

197

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

198

Preparation of bauxite ceramic microsphere  

Microsoft Academic Search

Ceramic microspheres were prepared by using Chinese bauxite as raw materials through the centrifugal spray drying method.\\u000a The control technology of microsphere size, degree of sphericity was researched. The ceramic microspheres were sintered by\\u000a a double sintering process. The microstructure and composition of ceramic microsphere were investigated by X-ray diffraction\\u000a (XRD), scanning electron microscopy (SEM) and X-ray energy spectroscopy. The

Xiaosu Cheng; Pingan Liu; Xiuyan Li; Anze Shui; Lingke Zeng

2007-01-01

199

Preparation and characterization of hydroxyapatite/polycaprolactone-chitosan composites.  

PubMed

Hydroxyapatite (HA)/polycaprolactone (PCL)-chitosan (CS) composites were prepared by melt-blending. For the composites, the amount of HA was varied from 0% to 30% by weight. The morphology, structure and component of the composites were evaluated using environmental scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscope. The tensile properties were evaluated by tensile test. The bioactivity and degradation property were investigated after immersing in simulated body fluid (SBF) and physiological saline, respectively. The results show that the addition of HA to PCL-CS matrix tends to suppress the crystallization of PCL but improves the hydrophilicity. Adding HA to the composites decreases the tensile strength and elongation at break but increases the tensile modulus. After immersing in SBF for 14 days, the surface of HA/PCL-CS composites are covered by a coating of carbonated hydroxyapatite with low crystallinity, indicating the excellent bioactivity of the composites. Soaking in the physiological saline for 28 days, the molecular weight of PCL decreases while the mass loss of the composites and pH of physiological saline increase to 5.86% and 9.54, respectively, implying a good degradation property of the composites. PMID:19572106

Xiao, Xiufeng; Liu, Rongfang; Huang, Qiongyu; Ding, Xiaohong

2009-12-01

200

Crush strength of encapsulated microspheres  

Microsoft Academic Search

The use of coated microsphere fuels has been suggested for the Savannah River Plant's (SRP) operating reactors as well as for the Low-Temperature Heavy-Water (LTHW) New Production Reactor (NPR). A program is underway to examine the feasibility of incorporating coated microsphere fuels into the well developed powder metallurgy (PM) fuel fabrication process. The coated microspheres were developed for use in

Marra

1988-01-01

201

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

202

Cytotoxicity and genotoxicity property of hydroxyapatite-mullite eluates.  

PubMed

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

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

2011-02-01

203

[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

204

Anisotropic growth of hydroxyapatite on the silk fibroin films  

NASA Astrophysics Data System (ADS)

Bombyx mori silk fibroin is of practical interest for its excellent intrinsic properties utilizable in the biotechnological and biomedical fields. Here, the silk fibroin films were pretreated with different methods and then used as the template for the hydroxyapatite (HA) crystal growth. To study the effect of silk films' surface structure on the protein biomineralization, the films were immersed into 1.5 times simulated body fluid (1.5 × SBF) to induce the HA deposition at 37 °C. The results showed that an anisotropic growth of HA crystals was observed on the different films as judging from XRD, TEM and HRTEM data. This was thought that the positions and density of carboxyl groups, C dbnd O and amino groups on the surface of SF films may be different, which play the key effect on HA crystal growth.

Li, Yucheng; Cai, Yurong; Kong, Xiangdong; Yao, Juming

2008-12-01

205

Synthesis and characterization of wool keratin/hydroxyapatite nanocomposite.  

PubMed

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

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

2012-05-01

206

Synthesis of hydroxyapatite whiskers through dissolution reprecipitation process using EDTA  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) has been of interest in many industrial applications, such as ion exchange, catalysis and biomaterials. Chelating agents have often been used to prepare inorganic powders in the form of sphere, rod, whisker and fiber. In this study, HA whiskers were synthesized directly from typically shaped HA powders by refluxing at 80 and 100 °C for 24 h using ethylenediamine tetraacetic acid (EDTA). 3% or 6% of hydrogen peroxide (H 2O 2) was used to promote precipitation of HA crystals. The pH of the solution was adjusted at 7 or 9 by adding ammonia solution. The higher the H 2O 2 concentration, pH value and refluxing temperature, the longer and thinner whiskers were formed. The whiskers produced at 100 °C with 6% of H 2O 2 and pH 9 had the highest aspect ratio of about 50-60 (a length of 3 ?m and a width of 0.05 ?m).

Seo, Dong Seok; Lee, Jong Kook

2008-04-01

207

Preparation and characterization of nano-hydroxyapatite within chitosan matrix.  

PubMed

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

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

2013-12-01

208

Toughening mechanisms in iron-containing hydroxyapatite/titanium composites.  

PubMed

Pure hydroxyapatite (HA) is brittle and it cannot be directly used for the load-bearing biomedical applications. The purpose of this investigation was to develop a new iron-containing HA/titanium composite via pressureless sintering at a relatively low temperature with particular emphasis on identifying the underlying toughening mechanisms. The addition of iron to HA/titanium composites led to a unique and favorable core/shell microstructure of Ti-Fe particles that consisted of outer titanium and inner iron, and good interfacial bonding with HA matrix. While the relative density, hardness and Young's modulus reduced, the flexural strength, fracture toughness, fatigue resistance, and the related fracture surface roughness increased significantly with increasing amount of Ti-Fe particles. Different toughening mechanisms including crack bridging, branching and deflection were observed in the composites, thus effectively increasing the crack propagation resistance and resulting in a substantial improvement in the mechanical properties of the composites. PMID:19954836

Chang, Q; Chen, D L; Ru, H Q; Yue, X Y; Yu, L; Zhang, C P

2010-03-01

209

Gentamicin-impregnated chitosan/nanohydroxyapatite/ethyl cellulose microspheres granules for chronic osteomyelitis therapy.  

PubMed

In this article gentamicin (GM) impregnated microspheres were used to extend the drug release time for the treatment of chronic osteomyelitis. The granules were prepared in solution and consisted of nanohydroxyapatite (nHA), chitosan (CS) and GM loaded ethyl cellulose (EC) microspheres. A rabbit model with chronic osteomyelitis was made by using staphylococcus aureus and morrhuate sodium and special inspection methods were used to test the curative effects of the granules, such as microbiological investigations, tissue, and X-ray observations. The granules were provided with excellent drug release properties, 49 days in vitro and 45 days in vivo, moreover, they showed almost no cytotoxic for fibroblast and osteoblast. The findings indicated that the GM-impregnated CS/nHA/EC microspheres granules showed outstanding curative effect. Generally, it can be concluded that the granules containing GM impregnated microspheres may be used effectively in the treatment of the chronic osteomyelitis. PMID:19743510

Shi, Pujiang; Zuo, Yi; Li, Xiaowei; Zou, Qin; Liu, Haohuai; Zhang, Li; Li, Yubao; Morsi, Yos S

2010-06-01

210

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

211

Preparation and Characterization of Hydroxyapatite-Silica Composite Nanopowders  

NASA Astrophysics Data System (ADS)

One of the most important objectives in the field of biomaterials science and engineering is development of new materials as bone substitutes. Silica (SiO2) has an important role in the biomineralization and biological responses. The aim of this research was to prepare and characterize hydroxyapatite-silica (HA-SiO2) composite nanopowder with different content of silica. Hydroxyapatite-silica composite nanopowders with 20 and 40 wt% silica were prepared using a sol-gel method at 600°C with phosphoric pentoxide and calcium nitrate tetrahydrate as a source of hydroxyapatite; also, tetraethylorthosilicate and methyltriethoxisilane as a source of silica. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for characterization and evaluation of the products. The results indicated the presence of nanocrystalline hydroxyapatite phase beside amorphous silica phase in prepared composite nanopowders. Moreover, by increasing the content of silica in composite nanopowders, the crystallinity will be decreased,and the ability of the product as a bone substitute material might be controlled by changing the content of the ingredients and subsequently its structure.

Latifi, S. M.; Fathi, M. H.; Golozar, M. A.

212

A study on improving mechanical properties of porous HA tissue engineering scaffolds by hot isostatic pressing.  

PubMed

Various interconnected porous hydroxyapatite (HA) ceramic scaffolds are universally used to induct the tissue growth for bone repair and replacement, and serve to support the adhesion, transfer, proliferation and differentiation of cells. Impregnation of polyurethane sponges with a ceramic slurry is adopted to produce highly porous HA ceramic scaffolds with a 3D interconnected structure. However, high porosity always accompanies a decrease in the strength of the HA ceramic scaffolds. Therefore, it is significant to improve the strength of the HA ceramic scaffolds with highly interconnected porosity so that they are more suitable in clinical applications. In this work, highly porous HA ceramic scaffolds are first produced by the polymer impregnation approach, and subsequently further sintered by hot isostatic pressing (HIP). The phase composition, macro- and micro-porous structure, sintering and mechanical properties of the porous HA scaffolds are investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation analysis and compressive test. The experimental results show that the nanohardness and compressive strength of HIP-sintered porous HA ceramics are higher than those of commonly sintered HA scaffolds. The HIP technique can effectively improve the sintering property and densification of porous HA ceramic scaffolds, so inducing an increase in the compression strength. PMID:18458404

Zhao, Jing; Xiao, Suguang; Lu, Xiong; Wang, Jianxin; Weng, Jie

2006-12-01

213

Electrospun PCL/PLA/HA based nanofibers as scaffold for osteoblast-like cells.  

PubMed

Polycaprolactone (PCL), poly (lactic acid) (PLA) and hydroxyapatite (HA) are frequently used as materials for tissue engineering. In this study, PCL/PLA/HA nanofiber mats with different weight ratio were prepared using electrospinning. Their structure and morphology were studied by FTIR and FESEM. FTIR results demonstrated that the HA particles were successfully incorporated into the PCL/PLA nanofibers. The FESEM images showed that the surface of fibers became coarser with the introduction of HA nanoparticles into PCL/PLA system. Furthermore, the addition of HA led to the decreasing of fiber diameter. The average diameters of PCL/PLA/HA nanofiber were in the range of 300-600 nm, while that of PCL/PLA was 776 +/- 15.4 nm. The effect of nanofiber composition on the osteoblast-like MC3T3-E1 cell adhesion and proliferation were investigated as the preliminary biological evaluation of the scaffold. The MC3T3-E1 cell could be attached actively on all the scaffolds. The MTT assay revealed that PCL/PLA/HA scaffold shows significantly higher cell proliferation than PCL/PLA scaffolds. After 15 days of culture, mineral particles on the surface of the cells was appeared on PCL/PLA/HA nanofibers while normal cell spreading morphology on PCL/PLA nanofibers. These results manifested that electrospun PCL/PLA/HA scaffolds could enhance bone regeneration, showing their marvelous prospect as scaffolds for bone tissue engineering. PMID:21138024

Fang, Rui; Zhang, Enwei; Xu, Ling; Wei, Shicheng

2010-11-01

214

Comparative study of mesenchymal stem cells osteogenic differentiation on low-temperature biomineralized nanocrystalline carbonated hydroxyapatite and sintered hydroxyapatite.  

PubMed

Hydroxyapatite with different characteristics in terms of morphology and chemistry were prepared via conventional sintering and low temperature biomimetic mineralization methods. The biomineralization route introduced nanocrystalline carbonate-substituted hydroxyapatite (n-CHA) with needle-like crystals ranging 20-30 nm whereas sintered HA (S-HA) comprised of polygonal grains ranging 2-5 ?m. The response of fibroblastic cells was investigated using the extract of the samples whereas Wistar rat-derived mesenchymal stem cells (MSCs) were evaluated on top of each sample while maintaining in an osteogenic-free medium. The proliferation, activity, and morphology of adherent MSCs were determined at different culturing periods. The osteogenic differentiation of MSCs was also assayed by determining expression of runx2, osteonectin, osteopontin, and osteocalcin genes using real time-PCR analysis. The fibroblastic cells exhibited better proliferation rate at the presence of n-CHA compared to S-HA. Furthermore, the MSCs attached and spread well on both n-CHA and S-HA with better proliferation rate and alkaline phosphatase activity on n-CHA. Interestingly, the osteogenic differentiation of MSCs on n-CHA was confirmed by the expression of bone specific proteins whereas poor expression of these proteins was detected for the cells on S-HA. The results showed that the role of morphology, crystallinity, and chemistry of hydroxyapatite is crucial for osteogenesis differentiation of MSCs. The results predict osteoinductivity of n-CHA, because MSCs differentiation occurred at the absence of osteogenic medium. However, in vivo data are also required to support this suggestion. PMID:23853054

Hesaraki, Saeed; Nazarian, Hamid; Pourbaghi-Masouleh, Milad; Borhan, Shokoufeh

2014-01-01

215

Effects of parameters of sol–gel process on the phase evolution of sol–gel-derived hydroxyapatite  

Microsoft Academic Search

It has been established that hydroxyapatite powders can be produced using an alkoxide-based sol–gel technique. Nanocrystalline powders of hydroxyapatite (HA) were prepared from Ca(NO3)2·4H2O and PO(OC2H5)3 as calcium and phosphorus precursors, respectively, using a sol–gel route. For a number of samples, sol of phosphorus was first hydrolyzed for 24h with distilled water. The sol temperature, aging time and heat treatment

Hossein Eshtiagh-Hosseini; Mohammad Reza Housaindokht; Mohammad Chahkandi

2007-01-01

216

Inhibition of adsorption of Streptococcus mutans strains to saliva-treated hydroxyapatite by galactose and certain amines.  

PubMed Central

Adsorption of all of eight strains of Streptococcus mutans to saliva-treated hydroxyapatite (S-HA) surfaces was inhibited by galactose and melibiose, but not by other neutral sugars tested. This observation supports the hypothesis that lectin-like components participate in the attachment of these streptococci to salivary glycoproteins on saliva-treated hydroxyapatite surfaces. Adsorption of all strains was also inhibited by iodoacetate and spermine; other amines tested reduced adsorption of some strains, but not others.

Gibbons, R J; Qureshi, J V

1979-01-01

217

Hydroxyapatite coating on the Ti–35Nb–xZr alloy by electron beam-physical vapor deposition  

Microsoft Academic Search

The aim of this study was to investigate the hydroxyapatite coating on the Ti–35Nb–xZr alloy by electron beam-physical vapor deposition. The Ti–35Nb–xZr ternary alloys contained from 3wt.% to 10wt.% Zr content were manufactured by arc melting furnace. Hydroxyapatite (HA) coatings were prepared by electron-beam physical vapor deposition (EB-PVD) method, and crystallization treatment was performed in Ar atmosphere at 300 and

Yong-Hoon Jeong; Han-Cheol Choe; Sang-Won Eun

2011-01-01

218

Deposition of titanium nitride and hydroxyapatite-based biocompatible composite by reactive plasma spraying  

NASA Astrophysics Data System (ADS)

Titanium nitride is a bioceramic material successfully used for covering medical implants due to the high hardness meaning good wear resistance. Hydroxyapatite is a bioactive ceramic that contributes to the restoration of bone tissue, which together with titanium nitride may contribute to obtaining a superior composite in terms of mechanical and bone tissue interaction matters. The paper presents the experimental results in obtaining composite layers of titanium nitride and hydroxyapatite by reactive plasma spraying in ambient atmosphere. X-ray diffraction analysis shows that in both cases of powders mixtures used (10% HA + 90% Ti; 25% HA + 75% Ti), hydroxyapatite decomposition occurred; in variant 1 the decomposition is higher compared with the second variant. Microstructure of the deposited layers was investigated using scanning electron microscope, the surfaces presenting a lamellar morphology without defects such as cracks or microcracks. Surface roughness values obtained vary as function of the spraying distance, presenting higher values at lower thermal spraying distances.

Ro?u, Radu Alexandru; ?erban, Viorel-Aurel; Bucur, Alexandra Ioana; Drago?, U?u

2012-02-01

219

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

220

Dynamic Mechanical Analysis of Hydroxyapatite Nanoparticle /Gelatin Porous Scaffolds  

NASA Astrophysics Data System (ADS)

Porous nanoceramic/polymer scaffolds were fabricated by a freeze-drying process from synthetic nanosized hydroxyapatite / gelatin (nanoHA/Gel) mixtures with nanoHA loading varied from 0 to 50 % by weight. The scaffolds had interconnected porosity up to 90%, pore diameter in the range of 20 -- 300 micron, and pore wall thickness in the range of 3 -- 10 micron. Depending on the nanoHA/Gel mixture preparation routine, the HA nanoparticles either distribute uniformly within the matrix, or form aggregates on the surface of the pore walls. Dynamic mechanical analysis (DMA) of nanoHA/Gel scaffolds revealed the bending and tensile moduli up to 500 MPa and 800 MPa, respectively, when nanoHA loading was around 30% by weight. These moduli increase by a factor of 1.6 after the cross-linking of polymer. NanoHA loading above 50 % by weight results in both moduli above 2 GPa, but the cross-linking reduces them significantly. It has been further shown that the uniform dispersion of nanoHA within the polymer matrix improves the mechanical properties of the scaffolds.

Ghossein, H.; Dranca, I.; Vyazovkin, S.; Stanishevsky, A. V.

2010-03-01

221

Luminescence studies of rare-earth doped and Co-doped hydroxyapatite  

NASA Astrophysics Data System (ADS)

Rare-earth doped and co-doped hydroxyapatite (Eu: HA, Eu-Y: HA) were prepared by wet precipitation method by using CTAB as the organic modifier. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Photoluminescence spectra (PL). Upon excitation at 350 nm the samples Eu: HA and Eu-Y: HA shows the emission band in the visible region, which makes it suitable for potential application such as bio-imaging.

Vasugi, G.; Thamizhavel, A.; Girija, E. K.

2012-06-01

222

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

223

Effects of incorporation of HA/ZrO(2) into glass ionomer cement (GIC).  

PubMed

Glass ionomer cements (GICs) are a class of bioactive cements that bond directly to bone. In this paper, a new bioactive hydroxyapatite (HA)/zirconia (ZrO(2))-filled GIC composite was developed to improve the biocompatibility and bioactivity of the GICs with the surrounding bone and connective tissues. Nano-sized HA/30 wt% ZrO(2) powders were heat treated at 700 degrees Celsius and 800 degrees Celsius for 3 h to elucidate the influence of the crystallinity of composite powders on the performance of HA/ZrO(2)-GICs. The effects of different volume percentages of HA/ZrO(2) powders (4, 12, 28 and 40 vol%) substituted within GICs were investigated based on their microhardness, compressive strength and diametral tensile strength. The HA/ZrO(2)-GICs composite was soaked in distilled water for 1 day and 1 week before subjecting the samples to mechanical testing. Results showed that the glass and HA/ZrO(2) particles were distributed uniformly in the GIC matrix. The substitution of highly crystalline HA/ZrO(2) improved the mechanical properties of the HA/ZrO(2)-GICs due to the slow resorption rate for highly crystalline powders in distilled water. The mechanical properties of HA/ZrO(2)-GICs increased with increasing soak time due to the continuous formation of aluminium salt bridges, which improved the final strength of the cements. The compositions 4 and 12 vol% HA/ZrO(2)-GICs exhibited superior mechanical properties than the original GICs. The mechanical properties of HA/ZrO(2)-GICs were found to be much better than those of HA-GICs because ZrO(2) has the attributes of high strength, high modulus, and is significantly harder than glass and HA particles. Furthermore, ZrO(2) does not dissolve with increasing soaking time. PMID:15350775

Gu, Y W; Yap, A U J; Cheang, P; Khor, K A

2005-03-01

224

Titanium--hydroxyapatite porous structures for endosseous applications.  

PubMed

Materials for uncemented endosseous implants have to assure an as short as possible osseointegration time. Thus, a material with both surface bioactivity and a porous outer structure can become a preferred choice for this type of applications. This paper presents a class of titanium-base PM composites, reinforced with particulate hydroxyapatite. Raw materials were titanium powder, obtained through hydriding--milling--dehydriding, with the grain size of 63-100 microm, and sol-gel hydroxyapatite (HA) powder, produced by the reaction between Ca(NO3)2 x 4H2O and (NH4)2HPO4. Blends with 5 to 50% HA were prepared and pressed in a rigid die, producing single composition or gradual composition samples. The applied pressure was of 400, 500 or 600 MPa. Sintering was performed in vacuum, at 1160 ( composite function)C. All samples, although well sintered, displayed swelling during sintering, due to diffusion into the matrix. The increase in volume is more severe for higher amounts of HA in the green compacts and for higher applied compaction pressure. Compacts with a gradual increase of the HA content are recommended from the functional and mechanical point of view, but the increase should be slow, not to produce interlayer cracks. The outer surface shows interconnected pores, suitable for the ingrowth of vital new bone. PMID:16362217

Popa, C; Simon, V; Vida-Simiti, I; Batin, G; Candea, V; Simon, S

2005-12-01

225

In vitro evaluation of the effects of yttria-alumina-silica microspheres on human keratinocyte cells.  

PubMed

The behavior of yttria-alumina-silica spray-dried microspheres was investigated in vitro on a human keratinocyte cell line, first to exclude their cytotoxicity. The HaCaT cells were chosen due to their well-characterized phenotype and their phagocytic ability. Microscopic analysis and cell viability tests showed no negative effect of the microspheres on cells morphology and behavior. Scanning electron microscopy and transmission electron microscopy results evidenced the cellular internalization of the microspheres at 48 h after their incubation with cultured cells. The shape, size distribution, structure, composition, and chemical states of the elements on samples surface were analyzed by SEM, transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy, because these properties could influence their internalization by cells. The yttrium distribution on the microspheres surface was indicated by fluorescence microscopy imaging. The microspheres dimension and shape inside the cells was in accordance with their dimension and shape before incubation. The microspheres seemed captured and engulfed by the cells in native form and appeared resistant to degradation over the first 48 h. Most of the analyzed cells took up more microspheres, suggesting that the microspheres were actively phagocytosed by the cells and accumulated within the cytoplasm. X-ray photoelectron spectroscopy results on Al and Si atomic environments denoted Al-O-Si crosslinks, which improve the surface protection to corrosion. PMID:22887911

Radu, T; Chiriac, M T; Popescu, O; Simon, V; Simon, S

2013-02-01

226

Injectable Poly(ethylene glycol) Dimethacrylate-based Hydrogels with Hydroxyapatite  

Microsoft Academic Search

Injectable hydrogels are attractive materials for tissue engineering as they provide fast reaction rates, low heat release, and biocompatibility for cell proliferation and permanent interface with surrounding tissue. A series of injectable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels with four different weight fractions of hydroxyapatite (HA) particles were prepared and thermal and mechanical properties evaluated. The cytocompatibility was assessed by examining

Ziyou Zhou; Dongzhi Yang; Jun Nie; Yongjuan Ren; Fuzhai Cui

2009-01-01

227

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

PubMed

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

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

2013-10-01

228

Synthesis of hydroxyapatite-based powders by mechano-chemical method and their sintering  

Microsoft Academic Search

Ceramic hydroxyapatite (HA) is on the way to gaining credit as one of the most promising and diversified materials for employment in surgery, thanks to its good characteristics of biocompatibility and bioadaptability. The main and probably unique deficiency of these materials obtained by traditional methods consists in its weak mechanical resistance, that does not allow their use when even low

M. Toriyama; A. Ravaglioli; A. Krajewski; G. Celotti; A. Piancastelli

1996-01-01

229

Cytotoxicity of hydroxyapatite nanoparticles is shape and cell dependent.  

PubMed

Nanosized hydroxyapatite (nHA) has been proposed as drug delivery vehicles because of its biocompatibility. While the possible risks of nHA inducing inflammation have been highlighted, the specific influence of varying nHA particle morphology is still unclear. In order to establish this understanding, nHA of four different shapes--needle (nHA-ND), plate (nHA-PL), sphere (nHA-SP) and rod (nHA-RD)--were synthesized. The particle effects with the concentration of 10-300 ?g/mL on cytotoxicity, oxygen species generation, production of inflammatory cytokines (TNF-? and IL-6), particle-cell association and cellular uptake were evaluated on BEAS-2B and RAW264.7 cells. Results show that nHA-ND and nHA-PL induced the most significant cell death in BEAS-2B cultures compared to nHA-SP and nHA-RD. Necrosis-apoptosis assay by FITC Annexin V and propidium iodide (PI) staining revealed loss of the majority of BEAS-2B by necrosis. No significant cell death was recorded in RAW264.7 cultures exposed to any of the nHA groups. Correspondingly, no significant differences were observed in TNF-? level for RAW264.7 cells upon incubation with nHA of different shapes. In addition, nHA-RD exhibited a higher degree of particle-cell association and internalization in both BEAS-2B and RAW264.7 cells, compared to nHA-ND. The phenomena suggested that higher particle-cell association and increased cellular uptake of nHA need not result in increased cytotoxicity, indicating the importance of particle shape on cytotoxicity. Specifically, needle- and plate-shaped nHA induced the most significant cell-specific cytotoxicity and IL-6 expression but showed the least particle-cell association. Taken collectively, we demonstrated the shape-dependent effects of nHA on cytotoxicity, inflammatory cytokine expression and particle-cell association. PMID:22415765

Zhao, Xinxin; Ng, SuXiu; Heng, Boon Chin; Guo, Jun; Ma, LwinLwin; Tan, Timothy Thatt Yang; Ng, Kee Woei; Loo, Say Chye Joachim

2013-06-01

230

Characterization of the chemically deposited hydroxyapatite coating on a titanium substrate  

Microsoft Academic Search

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

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

2011-01-01

231

Hydroxyapatite coating improves 8- to 10-year performance of the link RS cementless femoral stem  

Microsoft Academic Search

In a prospective randomized clinical study, 12 hydroxyapatite (HA)-coated and 8 identical but noncoated stems were implanted in 20 patients. At 8- to 10-year follow-up, the HA-coated stems displayed excellent clinical and radiographic results in 11 out of 12 patients, whereas 7 out of 8 noncoated stems were failures and had been subject to revision. Despite the small number of

Lars Palm; Sven-Arne Jacobsson; Ingemar Ivarsson

2002-01-01

232

Magnetron co-sputtered silicon-containing hydroxyapatite thin films—an in vitro study  

Microsoft Academic Search

The use of silicon-substituted hydroxyapatite (Si-HA) as a biomaterial has been reported recently. In vivo testing has shown that Si-HA promotes early bonding of the bone\\/implant interface. In order to extend its usage to major load-bearing applications such as artificial hip replacement implants, it has been proposed that the material could be used in the form of a coating on

E. S. Thian; J. Huang; S. M. Best; Z. H. Barber; W. Bonfield

2005-01-01

233

Effect of phospholipids on the transformation of amorphous calcium phosphate to hydroxyapatite in vitro  

Microsoft Academic Search

The conversion of amorphous calcium phosphate (ACP) to crystalline hydroxyapatite (HA) was studiedin vitro in the presence or absence of phosphatidyl serine (PS) and other phospholipids. ACP transformation and HA crystal growth\\u000a were monitored by electron microscopy, selected-area electron diffraction and X-ray diffraction, and by measuring supernatant\\u000a calcium and phosphate. PS, and other acidic phospholipids, had a significant stabilizing effect

R. E. Wuthier; E. D. Eanes

1975-01-01

234

Bioactive glass and hydroxyapatite thin films obtained by pulsed laser deposition  

Microsoft Academic Search

Bioactive glass (BG), calcium hydroxyapatite (HA), and ZrO2 doped HA thin films were grown by pulsed laser deposition on Ti substrates. An UV KrF* (?=248nm, ??7ns) excimer laser was used for the multi-pulse irradiation of the targets. The substrates were kept at room temperature or heated during the film deposition at values within the (400–550°C) range. The depositions were performed

E. Gyorgy; S. Grigorescu; G. Socol; I. N. Mihailescu; D. Janackovic; A. Dindune; Z. Kanepe; E. Palcevskis; E. L. Zdrentu; S. M. Petrescu

2007-01-01

235

Chemical analysis of silica doped hydroxyapatite biomaterials consolidated by a spark plasma sintering method  

Microsoft Academic Search

Silica (SiO2) and the silicate-based biomaterials play an important role due to their in vitro and in vivo biological response. The present study synthesized a novel nano-structured amorphous silica doped hydroxyapatite (HA) via an aqueous precipitation route. HA was prepared with 0, 1, 3 and 5wt% silica, which are comparable to the measured silicon content of natural bone. After spray

J. L. Xu; K. A. Khor

2007-01-01

236

Hydroxyapatite coating enhances fixation of loaded pedicle screws: a mechanical in vivo study in sheep  

Microsoft Academic Search

Loosening of the pedicle screws with subsequent non-union or loss of correction is a frequent problem in spinal instrumentation. In a clinical pilot study, coating of pedicle screws with plasma-sprayed hydroxyapatite (HA) resulted in a significant increase of removal torque. An experimental study was performed to investigate the effects of HA coating on the pull-out resistance. Thirteen sheep were operated

Bengt Sandén; Claes Olerud; Sune Larsson

2001-01-01

237

Effect of hydroxyapatite thickness on metal ion release fkom Ti6AMV  

Microsoft Academic Search

The electrochemical dissolution behaviour of Ti6Al4V alloy coated with hydroxyapatite (HA) by plasma spraying was studied in Hank's balanced salt solution (HBSS) and compared with that of polished and grit-blasted passivated surfaces. Two different nominal thicknesses of HA (50 and 200pm) were used. Taking a polished passivated surface as reference, grit blasting of the substrate increased the electrical charge used

S. R. Sous; M. A. Barbosa

238

Effect of hydroxyapatite thickness on metal ion release from Ti6Al4V substrates  

Microsoft Academic Search

The electrochemical dissolution behaviour of Ti6Al4V alloy coated with hydroxyapatite (HA) by plasma spraying was studied in Hank's balanced salt solution (HBSS) and compared with that of polished and grit-blasted passivated surfaces. Two different nominal thicknesses of HA (50 and 200 ?m) were used. Taking a polished passivated surface as reference, grit blasting of the substrate increased the electrical charge

S. R. Sousa; M. A. Barbosa

1996-01-01

239

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

Microsoft Academic Search

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

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

2009-01-01

240

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

241

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

242

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

243

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

244

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

245

Doped zinc oxide microspheres  

DOEpatents

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

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

1993-01-01

246

Doped zinc oxide microspheres  

DOEpatents

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

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

1993-12-14

247

MICROSPHERES FOR RADIATION THERAPY  

Microsoft Academic Search

The treatment of malignant tumors with ionizing radiation using ceramic ; microspheres that can be localized at selected sites for interstitial therapy is ; discussed. Thus, radiation damage in healthy tissues can be minimized by ; tailoring radioactivity to control dose, dose rate, and volume of tissue ; irradiated. The mean life, radiation energies, and beta-gamma dose can be ;

J. F. Perry; M. K. Loken; J. P. Ryan; L. D. MacLean

1962-01-01

248

Characterization and In Vitro Corrosion Investigations of Thermal Sprayed Hydroxyapatite and Hydroxyapatite-Titania Coatings on Ti Alloy  

NASA Astrophysics Data System (ADS)

In the current investigation, hydroxyapatite (HA) powder was mixed with titania (TiO2) in 50:50 wt pct for depositing composite coatings on a Ti-alloy substrate using a thermal-spray coating technique. The coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) analyses. The corrosion behavior of the coatings was studied by electrochemical corrosion testing in simulated human body fluid. After the corrosion testing, the samples were analyzed by XRD and SEM/EDS analyses. HA and TiO2 (rutile) were the main phases observed in the developed coatings. Bulk HA coating was amorphous; however, the addition of TiO2 effectively improved the crystallinity of HA in HA-TiO2 coating. The SEM analysis confirmed the formation of a well-formed HA-TiO2 composite coating. HA coating exhibited higher bond strength (67.8 MPa) compared with HA-TiO2 composite coating (37.6 MPa). The electrochemical study showed a significant improvement in the corrosion resistance of the Ti alloy after the deposition of the coatings.

Sarao, Tejinder Pal Singh; Sidhu, Hazoor Singh; Singh, Harpreet

2012-11-01

249

A novel nano hydroxyapatite-incorporated Ni–P coating as an effective inter layer for biological applications  

Microsoft Academic Search

Hydroxyapatite (HA) coatings are normally made directly on orthopaedic implants and they possess many demerits such as cracks,\\u000a irregular phase composition and poor adhesion. The present study had a novel approach of providing a nano-HA and phosphorous-rich\\u000a electroless nickel (EN) coating as an interlayer on stainless steel (SS) prior to electrodeposition of pure HA coating. The\\u000a interlayer had the merits

S. M. A. Shibli; A. C. Jayalekshmi

2009-01-01

250

Fabrication of three-dimensional polycaprolactone\\/hydroxyapatite tissue scaffolds and osteoblast-scaffold interactions in vitro  

Microsoft Academic Search

Computer-aided tissue-engineering approach was used to develop a novel precision extrusion deposition (PED) process to directly fabricate Polycaprolactone (PCL) and composite PCL\\/hydroxyapatite (PCL–HA) tissue scaffolds. The process optimization was carried out to fabricate both PCL and PCL–HA (25% concentration by weight of HA) with a controlled pore size and internal pore structure of the 0°\\/90° pattern. Two groups of scaffolds

Lauren Shor; Selçuk Güçeri; Xuejun Wen; Milind Gandhi; Wei Sun

2007-01-01

251

Characterization of Sr-substituted hydroxyapatite thin film by sputtering technique from mixture targets of hydroxyapatite and strontium apatite.  

PubMed

Sr-substituted hydroxyapatite thin films were prepared by sputtering technique from mixture targets of hydroxyapatite (HA) and strontium apatite (SrAp). The HA and SrAp powders were mixed at 0-100% Sr/(Sr+Ca) target ratios. The coated films were recrystallized by a hydrothermal treatment to reduce film dissolution. The films were then characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP). The osteocompatiblity of the films was also evaluated by the size of the bone formation area in osteoblast cells.In the XRD patterns, peaks shifted to lower 2? values with increasing Sr/(Sr+Ca) target ratios, which indicated Sr incorporation into the HA lattice. In the SEM observation of the hydrothermally treated films, the surface was covered with globular particles, and the size of the globular particles increased from Sr0 to Sr40, and then the size decreased from Sr60 to Sr100. The ICP analysis showed that the Sr/(Sr+Ca) film ratios were almost the same as the target ratios. In the cell culture, the bone formation area on the Sr-substituted HA films increased with increasing Sr concentration, and saturated at Sr60. PMID:24642972

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

2014-01-01

252

Synthesis and characterization of TEP-EDTA-regulated bioactive hydroxyapatite  

NASA Astrophysics Data System (ADS)

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

Haders, Daniel Joseph, II

253

Preparation and characterisation of calcium-phosphate porous microspheres with a uniform size for biomedical applications.  

PubMed

In the present work, a novel route for the preparation of porous ceramic microspheres is described. Two ceramic powders, calcium-titanium-phosphate (CTP) and hydroxyapatite (HAp), were mixed with a sodium alginate solution that enabled the preparation of spherical particles, using the droplet extrusion method combined with ionotropic gelation in the presence of Ca(2+). The spherical particles were subsequently sintered, to burn-off the polymer and obtain calcium-phosphate microspheres with a uniform size and an interconnected porous network. CTP microspheres with diameters ranging from 513 +/- 24 microm to 792 +/- 35 microm and with pores of approximately 40 microm were obtained. HAp microspheres presented diameters of 429 +/- 46 microm and 632 +/- 40 microm and pores of ca. 2 microm. Depending on the formulations tested, the structure of both calcium phosphates may become altered during the sintering process, suggesting that the ratio between the ceramic phase and the polymer solution is a critical parameter. Porous microspheres prepared using the described methodology are promising candidates as bone defect fillers and scaffolds for bone tissue regeneration. PMID:16688586

Ribeiro, C C; Barrias, C C; Barbosa, M A

2006-05-01

254

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

255

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

256

Nano hydroxyapatite-coated implants improve bone nanomechanical properties.  

PubMed

Nanostructure modification of dental implants has long been sought as a means to improve osseointegration through enhanced biomimicry of host structures. Several methods have been proposed and demonstrated for creating nanotopographic features; here we describe a nanoscale hydroxyapatite (HA)-coated implant surface and hypothesize that it will hasten osseointegration and improve its quality relative to that of non-coated implants. Twenty threaded titanium alloy implants, half prepared with a stable HA nanoparticle surface and half grit-blasted, acid-etched, and heat-treated (HT), were inserted into rabbit femurs. Pre-operatively, the implants were morphologically and topographically characterized. After 3 weeks of healing, the samples were retrieved for histomorphometry. The nanomechanical properties of the surrounding bone were evaluated by nanoindentation. While both implants revealed similar bone-to-implant contact, the nanoindentation demonstrated that the tissue quality was significantly enhanced around the HA-coated implants, validating the postulated hypothesis. PMID:23045363

Jimbo, R; Coelho, P G; Bryington, M; Baldassarri, M; Tovar, N; Currie, F; Hayashi, M; Janal, M N; Andersson, M; Ono, D; Vandeweghe, S; Wennerberg, A

2012-12-01

257

Strategies for a direct characterization of phosphoproteins on hydroxyapatite surfaces.  

PubMed

We show in this work how systems formed by phosphoproteins on calcium phosphate surfaces can be directly characterized, in real time, in liquid medium, without the need for elution or labeling. Specifically, we show how this is possible by applying three different techniques: ellipsometry, quartz crystal microbalance with dissipation, and atomic force microscopy-based friction force spectroscopy. We apply these techniques to study two different model systems, i.e. those formed upon the adsorption of two model phosphoproteins (?- and ?-casein) on hydroxyapatite (HA) surfaces. Information on the kinetics of adsorption, surface excess, viscoelasticity, water content, thickness of the layers, and protein-surface interaction is provided. Results indicate that both phosphoproteins form homogeneous elastic highly hydrated monolayers on the HA surfaces, the strength of ?-casein layers being higher by approximately a factor of 4. Based on the experimental results, models for the conformation of ?- and ?-casein molecules adsorbed on HA surfaces are proposed. PMID:24296726

Sotres, J; Barrantes, A; Lindh, L; Arnebrant, T

2014-01-01

258

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.

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

2011-01-01

259

A simple and rapid method to graft hydroxyapatite on carbon nanotubes  

PubMed Central

Herein a simple and effective approach is introduced to functionalize single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA). The pristine SWCNTs were chemically activated through introduction of carboxylic groups on their surfaces by refluxing in the mixture of H2SO4 and HNO3. The resulting carboxylated SWCNTs were further utilized for grafting of HA. The Fourier transform infrared and Raman spectroscopic studies demonstrated the formation of HA and its grafting over SWCNTs. The phase composition of HA and existence Ca2+ and PO43? ions were studied using X-ray diffraction and energy dispersive X-ray analyses, respectively. The surface morphology of functionalized SWCNTs was analyzed using scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis confirmed the existence of HA on SWCNTs by exhibiting different thermogram for pure HA and functionalized SWCNTs. Overall this method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding.

Neelgund, Gururaj M.; Olurode, Kehinde; Oki, Aderemi

2011-01-01

260

Fabrication of interconnected microporous biomaterials with high hydroxyapatite nanoparticle loading.  

PubMed

Hydroxyapatite (HA) is known to promote osteogenicity and enhance the mechanical properties of biopolymers. However, incorporating a large amount of HA into a porous biopolymer still remains a challenge. In the present work, a new method was developed to produce interconnected microporous poly(glycolic-co-lactic acid) (PLGA) with high HA nanoparticle loading. First, a ternary blend comprising PLGA/PS (polystyrene)/HA (40/40/20 wt%) was prepared by melt blending under conditions for formation of a co-continuous phase structure. Next, a dynamic annealing stage under small-strain oscillation was applied to the blend to facilitate nanoparticle redistribution. Finally, the PS phase was sacrificially extracted, leaving a porous matrix. The results from different characterizations suggested that the applied small-strain oscillation substantially accelerated the migration of HA nanoparticles during annealing from the PS phase to the PLGA phase; nearly all HA particles were uniformly presented in the PLGA phase after a short period of annealing. After dissolution of the PS phase, a PLGA material with interconnected microporous structure was successfully produced, with a high HA loading above 30 wt%. The mechanisms beneath the experimental observations, particularly on the enhanced particle migration process, were discussed, and strategies for producing highly particle loaded biopolymers with interconnected microporous structures were proposed. PMID:20823506

Zhang, Wei; Yao, Donggang; Zhang, Qingwei; Zhou, Jack G; Lelkes, Peter I

2010-09-01

261

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.

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

2013-01-01

262

Radioactive Microspheres for Medical Applications  

Microsoft Academic Search

This paper reviews the preparation and application of radioactive microspheres for medical purposes. It first discusses the\\u000a properties of relevant radioisotopes and then explores the diagnostic uses of gamma-emitter labelled microspheres, such as\\u000a blood flow measurement and imaging of the liver and other organs. The therapeutic uses of alpha- and beta-emitting microspheres,\\u000a such as radioembolization, local tumour therapy and radiosynovectomy,

Urs HÄfeli

263

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

264

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.

Prosecka, Eva; Buzgo, Matej; Rampichova, Michala; Kocourek, Tomas; Kochova, Petra; Vyslouzilova, Lucie; Tvrdik, Daniel; Jelinek, Miroslav; Lukas, David; Amler, Evzen

2012-01-01

265

Thin-layer hydroxyapatite deposition on a nanofiber surface stimulates mesenchymal stem cell proliferation and their differentiation into osteoblasts.  

PubMed

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

266

Converting ultrasonic induction heating deposited monetite coating to Na-doped HA coating on H 2O 2-treated C/C composites by a two-step hydrothermal method  

NASA Astrophysics Data System (ADS)

a monetite coating on H 2O 2-treated C/C composites was prepared by ultrasonic induction heating (UIH) technology. Subsequently, this coating was subjected to an ammonia hydrothermal treatment to form a undoped hydroxyapatite (U-HA) coating. Finally, the as-prepared U-HA coating was placed in a NaOH solution and hydrothermally treated to produce the other hydroxyapatite (Na-HA) coating. The structure, morphology and chemical composition of the two HA coatings were characterized by XRD, FTIR, SEM and EDS, the adhesiveness and local mechanical properties, e.g. nanohardness and Young's modulus of the two HA coatings to C/C composites was evaluated by a scratch test and nanoindentation technique respectively. The results showed that the two HA coatings had the alike morphology and crystallization. But, compared with the U-HA coating, the Na-HA coating was doped with Na ions, and gave a Ca/P ratio close to a stoichiometric hydroxyapatite, and thus showed a higher nano-indentation value, Young's modulus, and larger bonding strength. These results verified the strengthened effect of Na ion in hydroxyapatite coating on carbon/carbon (C/C) composities.

Xin-bo, Xiong; Jian-feng, Hung; Xie-rong, Zeng; Cen-cen, Chu

2011-10-01

267

Mechanical, thermal, rheological and morphological behaviour of irradiated PP/HA composites  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) reinforced polypropylene (PP) composites are being developed as bone graft materials. In this research, the effect of ? irradiation on mechanical, rheological, thermal and morphological behaviour of PP-HA composites was studied. The melt flow index of polymer increased markedly when it was exposed to radiation. This is indicative of chain scission reaction as the predominant process. During the tensile testing, the composites exhibited brittle behaviour, showing no fluency point. Elongation at break showed a tendency to decrease with the increase in radiation dose while stress at break did not show significant variation with radiation dose. High HA content (>20%) and radiation dose (25 kGy) had significant influence on thermal stability.

Ramírez, C.; Albano, C.; Karam, A.; Domínguez, N.; Sánchez, Y.; González, G.

2005-07-01

268

[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

269

Hydroxyapatite-alumina composites and bone-bonding.  

PubMed

Hydroxyapatite-alumina (HA/Al2O3) composites, with HA contents of 15, 25, 30 and 70, and pure HA as well as pure Al2O3, were densified at 1275 degrees C at a top pressure of 200 MPa for 2 h, using glass-encapsulated hot isostatic pressing. From the sintered ceramics, cylinders 2.8 x 6 mm2 were prepared by ultrasonic machining and implanted into the femoral cortical bones of 12 New Zealand White rabbits for 3 months. After killing the animals, the femur was dissected out and cut into three sections, each containing one cylinder. The specimens were mounted in a push-out device and force was applied along the long axis of the cylinder. The maximum force required to loosen the implant was recorded and the fracture surface of the bone implant was studied by scanning electron microscopy (SEM). The results indicate the important role of HA in new bone apposition to the implants, reflected by increasing bonding strength with increasing HA content in the composites. However, the relationship between HA content and the bonding strength was not linear. The composite with 70% HA and the pure HA ceramic had the same level of bonding strength and similar fracture interfaces in SEM, which supports the high bonding strength detected (about 15 MPa). Fractures occurred both in the bone and in the implant, indicating the stress transfer ability of the contact zone. This study presents qualitatively and quantitatively HA-dependent characteristics in bone-bonding. The mechanical strength of the composites was measured by a three-point bending test. The bending strength of the materials decreases with increasing HA content. PMID:7662828

Li, J; Fartash, B; Hermansson, L

1995-03-01

270

Surface characteristics of a novel hydroxyapatite-coated dental implant  

PubMed Central

Purpose This study evaluated the surface characteristics and bond strength produced using a novel technique for coating hydroxyapatite (HA) onto titanium implants. Methods HA was coated on the titanium implant surface using a super-high-speed (SHS) blasting method with highly purified HA. The coating was performed at a low temperature, unlike conventional HA coating methods. Coating thickness was measured. The novel HA-coated disc was fabricated. X-ray diffraction analysis was performed directly on the disc to evaluate crystallinity. Four novel HA-coated discs and four resorbable blast medium (RBM) discs were prepared. Their surface roughnesses and areas were measured. Five puretitanium, RBM-treated, and novel HA-coated discs were prepared. Contact angle was measured. Two-way analysis of variance and the post-hoc Scheffe's test were used to analyze differences between the groups, with those with a probability of P<0.05 considered to be statistically significant. To evaluate exfoliation of the coating layer, 7 sites on the mandibles from 7 mongrel dogs were used. Other sites were used for another research project. In total, seven novel HA-coated implants were placed 2 months after extraction of premolars according to the manufacturer's instructions. The dogs were sacrificed 8 weeks after implant surgery. Implants were removed using a ratchet driver. The surface of the retrieved implants was evaluated microscopically. Results A uniform HA coating layer was formed on the titanium implants with no deformation of the RBM titanium surface microtexture when an SHS blasting method was used. Conclusions These HA-coated implants exhibited increased roughness, crystallinity, and wettability when compared with RBM implants.

Jung, Ui-Won; Hwang, Ji-Wan; Choi, Da-Yae; Hu, Kyung-Seok; Kwon, Mi-Kyung; Choi, Seong-Ho

2012-01-01

271

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

PubMed

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

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

2005-04-01

272

Comparative evaluation of biocompatibility of dense nanostructured and microstructured Hydroxyapatite/Titania composites.  

PubMed

This work deals with the biocompatibility of dense nano- and micro-structured Hydroxyapatite/Titania composites prepared by two step and conventional sintering, respectively. By application of two step sintering, it was shown that the final grain size of HA-15 wt.% TiO2 is maintained lower than 100 nm while by the application of conventional sintering it reaches higher than 100 nm. Biocompatibility of the dense bulks was evaluated by cell attachment and proliferation experiments. Cell morphology, and viability on each nano- and micro-structured Hydroxyapatite/Titania composites were examined at different time points. The nanostructured HA/Titania dense bulk exhibited higher cell viability than a microstructured one. In addition, the effects of ionic products from nano- and micro-structured bulk dissolution on osteoblasts were studied. The MTT test confirmed that the products from nanostructured HA/Titania dense bulk significantly promoted osteoblast proliferation within a certain concentration range. PMID:23498255

Farzin, A; Ahmadian, M; Fathi, M H

2013-05-01

273

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

PubMed

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

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

2013-05-01

274

Comparative study of hydroxyapatite and octacalcium phosphate coatings deposited on metallic implants by PLD method  

NASA Astrophysics Data System (ADS)

The aim of the presented study was an analysis of two apatite coatings: hydroxyapatite (HA) and octacalcium phosphate (OCP) as coatings materials for metallic implants. Both layers were deposited by means of the PLD method. As a target material, synthetic, powdered and pressed hydroxyapatite was used. HA was deposited on 316L steel substrate in two temperature ranges for obtaining different coatings: 150±30°C and 430±30°C for OCP and HA, respectively. As an intermediate layer, the nanocrystalline diamond layer (NCD) was deposited. Examined calcium phosphate layers were tested for adhesion of osteoblast cell culture (MG-63). Analytical methods (AFM, FTIR) showed the usefulness of the PLD method for deposition of the apatite layers on metallic implants. Both examined layers showed biocompatibility with human osteoblast cells and presented favorable conditions for their proliferation.

Mróz, W.; Bombalska, A.; Budner, B.; Burdy?ska, S.; Jedy?ski, M.; Prokopiuk, A.; Menaszek, E.; ?cis?owska-Czarnecka, A.; Niedzielska, A.; Niedzielski, K.

2010-12-01

275

Hydroxyapatite/titania composite bioactivity coating processed by the sol-gel method.  

PubMed

A hydroxyapatite/titania composite material was coated onto a titanium (pure Ti) substrate by the sol-gel method. HA (hydroxyapatite) and TiO(2) (titania) sols were made from precursors separately and mixed together. The mixed sol was coated onto the Ti substrate by a spin coating method. The coated samples were dried and heat-treated at certain temperature. The XRD data show that there is an improvement in crystallization and growth of the grain size as the temperature increases. The addition of TiO(2) delayed the crystallization of HA and accelerated its decomposition. The composite HA coating has a porous structure. The addition of TiO(2) also improved the corrosion resistance of the coating. PMID:19029606

Han, J Y; Yu, Z T; Zhou, L

2008-12-01

276

Spherical N-carboxyethylchitosan/hydroxyapatite nanoparticles prepared by ionic diffusion process in a controlled manner.  

PubMed

The nanocomposites containing hydroxyapatite (HA) and biomacromolecules have attracted considerable research interest in implants, tissue scaffolds and drug controlled delivery. In this study, the N-carboxyethylchitosan/hydroxyapatite (NCECS/HA) nanoparticles were prepared by the ionic diffusion process in a controlled manner. The crystallization, particle size, size distribution and aggregation morphology of the NCECS/HA nanocomposites were dependent on the mole ratio of the glucosamine unit in NCECS to the Ca(2+). Fourier transform-infrared spectroscopic (FTIR) result indicated that there are chemical bonds formed between NCECS and HA. X-ray diffraction (XRD) analysis showed that the crystallization of HA in NCECS matrix was significantly retarded. Transmission electron microscopy (TEM) results revealed that NCECS/HA nanocomposites have the spherical morphology with the diameter ranging from 10 to 40 nm. The NCECS mineralization is driven by the self-assembly of NCECS and HA. These NCECS/HA nanocomposites have potential applications as the carrier for the controlled delivery of growth factors and drugs. PMID:20890642

Zhu, Aiping; Lu, Yan; Zhou, Yao; Dai, Sheng

2010-12-01

277

Effect of nano-hydroxyapatite suspension on cell proliferation and cycle in human periodontal ligament cells.  

PubMed

The study was aimed to provide insights into the effect of nano-hydroxyapatite (nHA) suspension on cell proliferation and cycle of human periodontal ligament cells, offering the evidence for nHA being used in periodontal therapy. Human periodontal ligament cells (HPDLCs) were cultured in different concentrations of nano-hydroxyapatite/sodium carboxymethyl cellulose (nHA-CMCNa) suspension in vitro. After that, cell proliferation ability was examined by MTT [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometry. MTT assay demonstrated that the Relative Proliferation Rate (RPR) of 0.5% nHA-CMCNa group was significantly higher than other groups (p <0.05), which means that nHA-CMCNa might increase cell proliferation ability. Flow cytometry showed that cells in G1 phase decreased, whilst cells in S phase increased after cultured in nHA-CMCNa suspension for 48 h. The result suggested that part of cells finished G1 phase in advance and get into S phase earlier, which speed up the cell proliferation, nHA-CMCNa suspension had great effect on cell proliferation. The high concentration of nHA-CMCNa could shorten the time in G1 phase, impel part of cells into S phase, and accelerate proliferation rate of HPDLCs. PMID:23901474

Li, Fenghua; Peng, Jieying; Hu, Rui; Dong, Xin; Chen, Wei; Pan, Yifeng; Tang, Xiaohai; Xie, Ping

2013-07-01

278

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

279

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

280

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

281

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

282

Laser fabrication of optical microspheres  

Microsoft Academic Search

A new method for fabrication of optical microspheres with the use of a CW CO2 laser is reported. Conventional method for fabrication of microspheres includes grinding and polishing processes which is not only time consuming, but also difficult of getting optical spheres with diameter less than 500 mum. It will be demonstrated that the laser method is very simple and

Q. K. Kieu; Vadim P. Veiko

2004-01-01

283

Augmentation of engineered cartilage to bone integration using hydroxyapatite.  

PubMed

Articular cartilage injuries occur frequently in the knee joint. Photopolymerizable cartilage tissue engineering approaches appear promising; however, fundamentally, forming a stable interface between the subchondral bone and tissue engineered cartilage components remains a major challenge. We investigated the utility of hydroxyapatite (HA) nanoparticles to promote controlled bone-growth across the bone-cartilage interface in an in vitro engineered tissue model system using bone marrow derived stem cells. Samples incorporated with HA demonstrated significantly higher interfacial shear strength (at the junction between engineered cartilage and engineered bone) compared with the constructs without HA (p < 0.05), after 28 days of culture. Interestingly, this increased interfacial shear strength due to the presence of HA was observed as early as 7 days and appeared to have sustained itself for an additional three weeks without interacting with strength increases attributable to subsequent secretion of engineered tissue matrix. Histological evidence showed that there was ?7.5% bone in-growth into the cartilage region from the bone side. The mechanism of enhanced engineered cartilage to bone integration with HA incorporation appeared to be facilitated by the deposition of calcium phosphate in the transition zone. These findings indicate that controlled bone in-growth using HA incorporation permits more stable anchorage of the injectable hydrogel-based engineered cartilage construct via augmented integration between bone and cartilage. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 922-932, 2014. PMID:24259264

Dua, Rupak; Centeno, Jerry; Ramaswamy, Sharan

2014-07-01

284

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.

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

2011-01-01

285

Rifampicin polylactic acid microspheres for lung targeting.  

PubMed

Rifampicin polylactic acid microspheres for lung targeting were prepared by a modified emulsion-solvent diffusion method. The microspheres were free flowing, spherical with regular surface. Drug content, particle size distribution and in vitro release properties of the prepared microspheres were evaluated. In vivo experiments on rabbits showed remarkable accumulation of microspheres in the lung. PMID:11063425

Zhang, W; Jiang, X; Hu, J; Fu, C

2000-01-01

286

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

287

Immunofluorescence detection methods using microspheres  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

288

In vitro bioactivity and cytocompatibility properties of spark plasma sintered HA-Ti composites.  

PubMed

The present study reports the results of the detailed in vitro bioactivity and cytocompatibility properties of the hydroxyapatite (HA) and the HA-titanium (HA-Ti) composite with varying amount of Ti (5, 10, and 20 wt %), densified using spark plasma sintering process (SPS). Using this technique and tailoring suitable processing parameters, it has been possible to retain both HA and Ti in the sintered ceramics. Importantly, the uniquely designed SPS processing with suitably chosen parameters enables in achieving better mechanical properties, such as higher indentation fracture toughness (~1.5 MPa m(1/2) ) in HA-Ti composites compared with HA. X-ray diffraction and scanning electron microscopic (SEM) observations reveal good bioactivity of the HA-Ti composites with the formation of thick, flaky, and porous apatite layer when immersed in simulated body fluid at 37°C and pH of 7.4. Atomic absorption spectroscopic analysis of the simulated body fluid solution reveals dynamic changes in Ca(+2) ion concentration with more dissolution of Ca(+2) ion from the HA-20Ti composite. However, the measurements with inductively coupled plasma spectrometer do not record dissolution of Ti(+4) ions. Transmission electron microscopic analysis indicates weak crystalline nature of the apatite and confirms the formation of fine-scale apatite crystals. MTT assay, fluorescence, and SEM study demonstrate good cell viability and cell adhesion/proliferation of the Saos -2 cells, cultured on the developed composites under standard culture condition, and the difference in cell viability has been discussed in reference to substrate composition and roughness. Overall, HA-Ti composites exhibit comparable and even better in vitro bioactivity and cytocompatibility properties than HA. PMID:23281190

Kumar, Alok; Dhara, Sharmistha; Biswas, Krishanu; Basu, Bikramjit

2013-02-01

289

Coating of hydroxyapatite on highly porous Al2O3 substrate for bone substitutes.  

PubMed

A thin film of hydroxyapatite (HA) was successfully coated onto a highly porous substrate of alumina by using a novel solution technique. The coated HA bonded strongly to the substrate through a glass sintering aid with an intermediate thermal expansion coefficient. The coating was also found to be microstructurally and chemically uniform on the surfaces of the interconnected pores in the matrix of the substrate. Mechanical property testing results showed that the strength of the HA-coated composite was significantly improved, indicating a high potential for structural bone substitutes in hard tissue prosthetics. PMID:9509347

Jiang, G; Shi, D

1998-01-01

290

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

291

Effect of spark plasma sintering on the microstructure and in vitro behavior of plasma sprayed HA coatings  

Microsoft Academic Search

The crystalline phases and degree of crystallinity in plasma sprayed calcium phosphate coatings on Ti substrates are crucial factors that influence the biological interactions of the materials in vivo. In this study, plasma sprayed hydroxyapatite (HA) coatings underwent post-spray treatment by the spark plasma sintering (SPS) technique at 500°C, 600°C, and 700°C for duration of 5 and 30min. The activity

L.-G Yu; K. A Khor; H Li; P Cheang

2003-01-01

292

Evaluation of hydroxyapatite-bioglass and hydroxyapatite-ethyl vinyl acetate composite extracts on antioxidant defense mechanism and genotoxicity: an in vitro study.  

PubMed

Hydroxyapatite-bioglass (HA BG) and hydroxyapatite-ethyl vinyl acetate (HA EVA) are two composite materials that have been developed for bone substitution. Their activity on antioxidant defense mechanism and genotoxicity has not been investigated before. To further confirm its biocompatibility, the present study was undertaken to investigate the effect of HA BG and HA EVA on mice liver antioxidant mechanism along with chromosomal aberrations in human lymphocytes. Physiological saline extract of HA BG and HA EVA showed no adverse effect on liver antioxidant mechanism compared to the cyclophosphamide (CP)-induced toxicity on mice liver homogenate. The results were judged from the in vitro studies made on reduced glutathione, glutathione reductase and lipid peroxidation. These results were well supported by CP- and mytomycin C (MC)-induced genotoxicity studies on human lymphocytes in the presence and absence of a metabolic activator (S9). Hence, it was suggested that these tests could be considered for preliminary toxicological screening of materials intended for clinical applications ahead of in vivo animal model evaluation. PMID:21834633

Arun, M; Silja, P K; Mohanan, P V

2011-09-01

293

Mechanical properties of hydroxyapatite whisker reinforced polyetherketoneketone composite scaffolds.  

PubMed

The apparent mechanical properties of hydroxyapatite (HA) whisker reinforced polyetherketoneketone (PEKK) scaffolds were evaluated in unconfined, uniaxial compression to investigate the effects of the porosity (75%, 82.5% and 90%), HA content (0, 20 and 40 vol%) and mold temperature (350, 365 and 375 ( composite function)C). Increased porosity resulted in a non-linear decrease in the elastic modulus and yield strength for both reinforced and unreinforced PEKK scaffolds, as expected. The increase in elastic modulus and yield strength with increased relative density followed a power-law, similar to trabecular bone and other open-cell foams. HA whisker reinforcement generally resulted in an increased elastic modulus from 0 to 20 vol% HA and a subsequent decrease from 20 to 40 vol% HA, while the yield strength and strain were decreased in scaffolds with 40 vol% HA compared to those with 0 or 20 vol% HA. Increased mold temperature resulted in an increased elastic modulus, yield strength and yield strain. These effects enabled the mechanical properties to be tailored to mimic human trabecular bone. The elastic modulus was greater than 50 MPa, and the yield strength was greater than 0.5 MPa, for scaffolds with 75% porosity at all combinations of reinforcement level and mold temperature. Scaffolds with 75% porosity and 20 vol% HA molded at 375 ( composite function)C exhibited a mean elastic modulus and yield strength of 149 MPa and 2.2 MPa, respectively, which was the highest of the conditions investigated in this study and similar to human vertebral trabecular bone. Therefore, HA whisker reinforced PEKK scaffolds may be advantageous for permanent implant fixation, including interbody spinal fusion. PMID:19716108

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

2009-12-01

294

Modification and functionalization of hydrogel microspheres  

Microsoft Academic Search

Acrylamide (AAm)-methacrylic acid (MAc)-methylenebisacrylamide (MBAAm) terpolymer microspheres and AAmMAc-MBAAm-nitrophenyl acrylate (NPA) quaterpolymer microspheres with high monodispersity were prepared by precipitation polymerization in alcohol. The former were modified into composite microspheres containing hydrophobic domains or magnetite nanospheres. The active ester in the quaterpolymer microspheres was allowed to undergo hydrolysis or aminolysis to prepare novel microspheres such as highly negative, amphoteric, hydrophobic

Haruma Kawaguchi; Keiji Fujimoto; Yoshiyuki Nakazawa; Mami Sakagawa; Yasushi Ariyoshi; Miwako Shidara; Hitoshi Okazaki; Yukio Ebisawa

1996-01-01

295

Hydrothermal fabrication of hydroxyapatite on the PEG-grafted surface of wood from Chinese Glossy Privet  

NASA Astrophysics Data System (ADS)

Wood-hydroxyapatite composite material was developed by depositing hydrated calcium hydrogen phosphate (HCHP) on the surface of wood from Chinese Glossy Privet (CGP) with polyethylene glycol (PEG, HO(CH2CH2O)nH) as the grafting agent and subsequent hydrothermal vapor treatment. The results illustrated that HCHP could adhere quickly and strongly on the PEG-grafted wood surface. Moreover, this HCHP could be efficiently transformed to hydroxyapatite (HA, Ca10(PO4)6(OH)2) by hydrothermal vapor treatment. IR, XRD analysis and SEM observation indicated that the fabricated hydroxyapatite was pure and its morphology was uniform and microporous. This work provides a new fabricating approach of biocompatible material which may have some potential applications as bone-repairing material.

Wang, Ning; Cai, Chuanjie; Cai, Dongqing; Cheng, Junjie; Li, Shengli; Wu, Zhengyan

2012-10-01

296

Understanding the impact of divalent cation substitution on hydroxyapatite: an in vitro multiparametric study on biocompatibility.  

PubMed

Hydroxyapatite (HA), a stable and biocompatible material for bone tissue therapy, may present a variable stoichiometry and accept a large number of cationic substitutions. Such substitutions may modify the chemical activity of HA surface, with possible impact on biocompatibility. In this work, we assessed the effects of calcium substitution with diverse divalent cations (Pb(2+), Sr(2+), Co(2+), Zn(2+), Fe(2+), Cu(2+), or Mg(2+)) on the biological behavior of HA. Physicochemical analyses revealed that apatite characteristics related to crystallinity and calcium dissolution/uptake rates are very sensitive to the nature of cationic substitution. Cytocompatibility was evaluated by mitochondrial activity, membrane integrity, cell density, proapoptotic potential, and adhesion tests. With the exception of Zn-HA, all the substituted HAs induced some level of apoptosis. The highest apoptosis levels were observed for Mg-HA and Co-HA. Cu-HA was the only material to impair simultaneously mitochondrial activity, membrane integrity, and cell density. The highest relative cell densities after exposure to the modified HAs were observed for Mg-HA and Zn-HA, while Co-HA significantly improved cell adhesion onto HA surface. These results show that changes on surface dissolution caused by cationic substitution, as well as the increase of metal species released to biological media, were the main responsible factors related to alterations on HA biocompatibility. PMID:21626666

de Lima, Ingrid Russoni; Alves, Gutemberg Gomes; Soriano, Carlos Alberto; Campaneli, Ana Paula; Gasparoto, Thais Helena; Ramos, Erivan Schnaider; de Sena, Lídia Ágata; Rossi, Alexandre Malta; Granjeiro, José Mauro

2011-09-01

297

Physical and chemical properties of superparamagnetic Fe-incorporated nano hydroxyapatite.  

PubMed

Nano hydroxyapatite (n-HA) crystals carrying incorporated Fe ions were designed and synthesized by a co-precipitation method. The microstructure and morphology as well as magnetic property of the Fe-incorporated n-HA crystals (denoted as n-Fe-HA) were characterized by TEM, XRD and VSM. The results showed that lattice substitution or incorporation had occurred between Fe ions and n-HA, which was quite different from the mechanical mixture of Fe3O4 nanoparticles and n-HA crystals. The n-Fe-HA with a synthetic molar ratio of 1:2 (calculated by Fe3O4:HA) exhibited a needle like crystal shape and relatively good crystallinity. However, when the molar ratio was up to 1:1, some Fe3O4 nanoparticles were separated from n-Fe-HA crystals. The magnetization measurements showed that n-Fe-HA crystals were in superparamagnetic state, proving that the existence of Fe ions in n-HA crystals contributed to the magnetic properties of n-Fe-HA crystals. As one component of biomedical composite, n-Fe-HA has a potential to promote bone regeneration. PMID:19908688

Jiang, Hong; Li, Yubao; Zuo, Yi; Yang, Weihu; Zhang, Li; Li, Jidong; Wang, Li; Zou, Qin; Cheng, Lin; Li, Junfeng

2009-12-01

298

Zn- and Mg-doped hydroxyapatite nanoparticles for controlled release of protein.  

PubMed

Bovine serum albumin (BSA) protein incorporated with hydroxyapatite (HA) nanoparticles (NPs) were synthesized by an in situ precipitation process. 2 mol % Zn(2+) and Mg(2+) were used as dopants to synthesize Zn(2+)/Mg(2+)-doped HA-BSA NPs. In our study we used BSA as a model protein. The amount of BSA uptake by doped and undoped HA NPs and subsequent release of BSA from NPs were investigated. Zn-doped HA NPs showed the highest amount of BSA uptake, whereas the amount of BSA loaded in undoped HA NPs was the lowest. A two-stage BSA release profile from doped and undoped HA NPs was observed in phosphate buffer solution (PBS) at pH 7.2 +/- 0.2. The initial burst release was due to the desorption of BSA from the HA surface. The later stage of slow release was controlled by the dissolution of BSA incorporated HA NPs. The BSA release rate from Zn-doped HA NPs was found to be the highest, whereas undoped HA NPs released BSA at the slowest rate. Our study showed that the protein release rate from HA NPs can be controlled by the addition of suitable dopants, and doped HA-based NP systems can be used in bone growth factor and drug release study. PMID:20131882

Dasgupta, Sudip; Banerjee, Shashwat S; Bandyopadhyay, Amit; Bose, Susmita

2010-04-01

299

Zinc-substituted hydroxyapatite: a biomaterial with enhanced bioactivity and antibacterial properties.  

PubMed

Hydroxyapatite (HA) is a synthetic biomaterial and has been found to promote new bone formation when implanted in a bone defect site. However, its use is often limited due to its slow osteointegration rate and low antibacterial activity, particularly where HA has to be used for long term biomedical applications. This work will describe the synthesis and detailed characterization of zinc-substituted HA (ZnHA) as an alternative biomaterial to HA. ZnHA containing 1.6 wt% Zn was synthesized via a co-precipitation reaction between calcium hydroxide, orthophosphoric acid and zinc nitrate hexahydrate. Single-phase ZnHA particles with a rod-like morphology measuring ~50 nm in length and ~15 nm in width, were obtained and characterized using transmission electron microscopy and X-ray diffraction. The substitution of Zn into HA resulted in a decrease in both the a- and c-axes of the unit cell parameters, thereby causing the HA crystal structure to alter. In vitro cell culture work showed that ZnHA possessed enhanced bioactivity since an increase in the growth of human adipose-derived mesenchymal stem cells along with the bone cell differentiation markers, were observed. In addition, antibacterial work demonstrated that ZnHA exhibited antimicrobial capability since there was a significant decrease in the number of viable Staphylococcus aureus bacteria after in contact with ZnHA. PMID:23160913

Thian, E S; Konishi, T; Kawanobe, Y; Lim, P N; Choong, C; Ho, B; Aizawa, M

2013-02-01

300

XPS and bioactivity study of the bisphosphonate pamidronate adsorbed onto plasma sprayed hydroxyapatite coatings  

NASA Astrophysics Data System (ADS)

This paper reports the use of X-ray photoelectron spectroscopy (XPS) to investigate bisphosphonate (BP) adsorption onto plasma sprayed hydroxyapatite (HA) coatings commonly used for orthopaedic implants. BPs exhibit high binding affinity for the calcium present in HA and hence can be adsorbed onto HA-coated implants to exploit their beneficial properties for improved bone growth at the implant interface. A rigorous XPS analysis of pamidronate, a commonly used nitrogenous BP, adsorbed onto plasma sprayed HA-coated cobalt-chromium substrates has been carried out, aimed at: (a) confirming the adsorption of this BP onto HA; (b) studying the BP diffusion profile in the HA coating by employing the technique of XPS depth profiling; (c) confirming the bioactivity of the adsorbed BP. XPS spectra of plasma sprayed HA-coated discs exposed to a 10 mM aqueous BP solution (pamidronate) for periods of 1, 2 and 24 h showed nitrogen and phosphorous photoelectron signals corresponding to the BP, confirming its adsorption onto the HA substrate. XPS depth profiling of the 2 h BP-exposed HA discs showed penetration of the BP into the HA matrix to depths of at least 260 nm. The bioactivity of the adsorbed BP was confirmed by the observed inhibition of osteoclast (bone resorbing) cell activity. In comparison to the HA sample, the HA sample with adsorbed BP exhibited a 25-fold decrease in primary osteoclast cells.

McLeod, Kate; Kumar, Sunil; Smart, Roger St. C.; Dutta, Naba; Voelcker, Nicolas H.; Anderson, Gail I.; Sekel, Ron

2006-12-01

301

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

302

Quantification of carbon nanotube induced adhesion of osteoblast on hydroxyapatite using nano-scratch technique  

NASA Astrophysics Data System (ADS)

This paper explores the nano-scratch technique for measuring the adhesion strength of a single osteoblast cell on a hydroxyapatite (HA) surface reinforced with carbon nanotubes (CNTs). This technique efficiently separates out the contribution of the environment (culture medium and substrate) from the measured adhesion force of the cell, which is a major limitation of the existing techniques. Nano-scratches were performed on plasma sprayed hydroxyapatite (HA) and HA-CNT coatings to quantify the adhesion of the osteoblast. The presence of CNTs in HA coating promotes an increase in the adhesion of osteoblasts. The adhesion force and energy of an osteoblast on a HA-CNT surface are 17 ± 2 µN/cell and 78 ± 14 pJ/cell respectively, as compared to 11 ± 2 µN/cell and 45 ± 10 pJ/cell on a HA surface after 1 day of incubation. The adhesion force and energy of the osteoblasts increase on both the surfaces with culture periods of up to 5 days. This increase is more pronounced for osteoblasts cultured on HA-CNT. Staining of actin filaments revealed a higher spreading and attachment of osteoblasts on a surface containing CNTs. The affinity of CNTs to conjugate with integrin and other proteins is responsible for the enhanced attachment of osteoblasts. Our results suggest that the addition of CNTs to surfaces used in medical applications may be beneficial when stronger adhesion of osteoblasts is desired.

Lahiri, Debrupa; Benaduce, Ana Paula; Kos, Lidia; Agarwal, Arvind

2011-09-01

303

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

304

La ions in precipitated hydroxyapatites.  

PubMed

Hydroxyapatites were synthesized by precipitation from an aqueous solution with La3+ (0-0.75%) and with carbonate (0-6.1%) at controlled pH 7.0. Uptake of La3+ was 90-95% complete. Relatively low Ca/P (1.54-1.63) ratios were attributed to nonstoichiometry. Carbonate in samples was identified by IR spectroscopy as B-type carbonate. Lattice parameters of the hexagonal apatite structure were not affected by the La3+ content. Noncarbonated samples heated to 800 degrees C transform partially to beta-Ca3(PO4)2. Thermogravimetric analysis showed release of 0.4 mol adsorbed and 1 mol crystalline water up to 400 degrees C and decomposition of carbonate up to 900 degrees C in the samples. Luminescence data obtained for Gd-containing hydroxyapatites prove that Gd3+ ions are not incorporated in the precipitated hydroxyapatite. These findings suggest that, in the La-containing samples, La3+ is surface absorbed and not incorporated in hydroxyapatite. PMID:10376345

Mayer, I; Layani, J D; Givan, A; Gaft, M; Blanc, P

1999-04-01

305

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

306

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

307

Precise adsorption behavior and mechanism of Ni(II) ions on nano-hydroxyapatite.  

PubMed

The goal of this study was to synthesize use of hydroxyapatite as a high-efficiency adsorbent for Ni(II) ions, and to study its adsorption behavior. Three tests--Fourier-transform infrared spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller were carried out to determine the chemical functionality of the hydroxyapatite powders, to observe its crystal morphology, and to measure the specific surface area. Results indicate that proves the n-HA synthesized by chemical precipitation is an effective adsorbent for the removal of Ni(II) ions from water solution. The synthesized, needle-like nano-hydroxyapatite (n-HA) have a uniform average size of 31.9 X 21.3nm, a large specific surface area (135 m2/g), and typically is a weak crystal with a broad pore distribution. The adsorption isotherm shows the Langmuir model is applicable only when the initial Ni2+ concentration is lower than 0.1 mol/L. Multilayer adsorption was attributed to uneven pore distribution that occurred at higher Ni2+ concentration. The adsorption of Ni2+ onto n-HA was attributed to electrostatic attraction, ion exchange, and dissolution-precipitation reaction. As the result, Ni2+ substitutes Ca2+ and binds with the oxygen atom on the surface, which resulted from the change in crystal-phase composition and in the binding energy of surface elements of n-HA before and after adsorption. PMID:21141390

Zhang, Jun; Wang, Deping; Zhou, Jun; Yao, Aihua; Huang, Wenhai

2010-11-01

308

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.

Liu, Pingsheng; Song, Jie

2013-01-01

309

Laser fabrication of optical microspheres  

NASA Astrophysics Data System (ADS)

A new method for fabrication of optical microspheres with the use of a CW CO2 laser is reported. Conventional method for fabrication of microspheres includes grinding and polishing processes which is not only time consuming, but also difficult of getting optical spheres with diameter less than 500 ?m. It will be demonstrated that the laser method is very simple and capable of producing a wide range of optical spheres with diameter of several millimeters down to 10 micrometers or even less, and a wide range of materials can be used (glasses, porous glasses, glass-like ceramics...). Some applications of microspheres produced by the laser method are discussed.

Kieu, Q. K.; Veiko, Vadim P.

2004-04-01

310

Convective microsphere monolayer deposition  

NASA Astrophysics Data System (ADS)

There is perhaps no simpler way of modifying surface chemistry and morphology than surface deposition of particles. Micron-sized microspheres were deposited into thin films via rapid convective deposition, similar to the `coffee ring effect' using a similar method to that studied by Prevo and Velev, Langmuir, 2003. By varying deposition rate and blade angle, the optimal operating ranges in which 2D close-packed arrays of microspheres existed were obtained. Self-assembly of colloidal particles through a balance of electrostatic and capillary forces during solvent evaporation was revealed. These interactions were explored through a model comparing the residence time of a particle in the thin film and the characteristic time of capillary-driven crystallization to describe the morphology and microstructure of deposited particles. Co-deposition of binary suspensions of micron and nanoscale particles was tailored to generate higher-quality surface coatings and a simple theory describes the immergence of instabilities that result in formation of stripes. Optical and biomedical applications that utilize the described nanoscale control over surface morphology will also be discussed.

Gilchrist, James

2011-03-01

311

Bioactive rosette nanotube-hydroxyapatite nanocomposites improve osteoblast functions.  

PubMed

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

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

2012-09-01

312

Adsorption and spectroscopic characterization of lactoferrin on hydroxyapatite nanocrystals.  

PubMed

Lactoferrin (LF), a well-characterized protein of blood plasma and milk with antioxidant, cariostatic, anticarcinogenic and anti-inflammatory properties, has been adsorbed onto biomimetic hydroxyapatite (HA) nanocrystals at two different pH values (7.4 and 9.0). The interaction was herein investigated by spectroscopic, thermal and microscopic techniques. The positive electrostatic surface potential of LF at pH 7.4 allows a strong surface interaction with the slightly negative HA nanocrystals and avoids the protein-protein interaction, leading to the formation of a coating protein monolayer. In contrast, at pH 9.0 the surface potential of LF is a mix of negative and positive zones favouring the protein-protein interaction and reducing the interaction with HA nanocrystals; as a result a double layer of coating protein was formed. These experimental findings are supported by the good fittings of the adsorption isotherms by different theoretical models according to Langmuir, Freundlich and Langmuir-Freundlich models. The nanosized HA does not appreciably affect the conformation of the adsorbed protein. In fact, using FT-Raman and FT-IR, we found that after adsorption the protein was only slightly unfolded with a small fraction of the ?-helix structure being converted into turn, while the ?-sheet content remained almost unchanged. The bioactive surface of HA functionalized with LF could be utilized to improve the material performance towards the biological environment for biomedical applications. PMID:21152600

Iafisco, Michele; Di Foggia, Michele; Bonora, Sergio; Prat, Maria; Roveri, Norberto

2011-01-28

313

Nucleation and inhibition of hydroxyapatite formation by mineralized tissue proteins.  

PubMed Central

Many proteins found in mineralized tissues have been proposed to function as regulators of the mineralization process, either as nucleators or inhibitors of hydroxyapatite (HA) formation. We have studied the HA-nucleating and HA-inhibiting properties of proteins from bone [osteocalcin (OC), osteopontin (OPN), osteonectin (ON) and bone sialoprotein (BSP)], dentine [phosphophoryn (DPP)] and calcified cartilage [chondrocalcin (CC)] over a wide range of concentrations. Nucleation of HA was studied with a steady-state agarose gel system at sub-threshold [Ca] x [PO4] product. BSP and DPP exhibited nucleation activity at minimum concentrations of 0.3 microgram/ml (9 nM) and 10 micrograms/ml (67 nM) respectively. OC, OPN, ON and CC all lacked nucleation activity at concentrations up to 100 micrograms/ml. Inhibition of HA formation de novo was studied with calcium phosphate solutions buffered by autotitration. OPN was found to be a potent inhibitor of HA formation [IC50 = 0.32 microgram/ml (0.01 microM)] whereas OC was of lower potency [IC50 = 6.1 micrograms/ml (1.1 microM)]; BSP, ON and CC all lacked inhibitory activity at concentrations up to 10 micrograms/ml. The effect of OPN on HA formation de novo is mainly to inhibit crystal growth, whereas OC delays nucleation. These findings are consistent with the view that BSP and DPP may play roles in the initiation of mineralization in bone and dentine respectively. OPN seems to be the mineralized tissue protein most likely to function in the inhibition of HA formation, possibly by preventing phase separation in tissue fluids of high supersaturation.

Hunter, G K; Hauschka, P V; Poole, A R; Rosenberg, L C; Goldberg, H A

1996-01-01

314

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.

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

2012-01-01

315

Strontium-substituted hydroxyapatite coatings synthesized by pulsed-laser deposition: In vitro osteoblast and osteoclast response  

Microsoft Academic Search

The increasing interest in strontium incorporation into biomaterials for hard tissue repair is justified by the growing evidence of its beneficial effect on bone. We successfully synthesized hydroxyapatite (HA) thin films with different extents of strontium substitution for calcium (0, 1, 3 or 7at.%) by pulsed-laser deposition. The coatings displayed a granular surface and a good degree of crystallinity, which

C. Capuccini; P. Torricelli; F. Sima; E. Boanini; C. Ristoscu; B. Bracci; G. Socol; M. Fini; I. N. Mihailescu; A. Bigi

2008-01-01

316

Formation and characteristics of the apatite layer on plasma-sprayed hydroxyapatite coatings in simulated body fluid  

Microsoft Academic Search

Plasma-sprayed hydroxyapatite (HA) coatings were incubated in simulated body fluids (SBFs) for different periods of time to investigate the nucleation and growth of apatite on their surface. The layer that formed was recognized as having similarities to bone apatite because it is poorly crystallized, non-stoichiometric or calcium deficient, and contains carbonate and magnesium. Scanning electron microscopy (SEM) and infrared spectroscopy

Jie Weng; Qing Liu; J. G. C. Wolke; Xingdong Zhang; K. de Groot

1997-01-01

317

Fracture strength and elastic modulus as a function of porosity for hydroxyapatite and other brittle materials Part I  

Microsoft Academic Search

Porous brittle materials are used as filters, catalyst supports, solid oxide fuel cells and biomedical materials. However the literature on the Weibull modulus, m, versus volume fraction porosity, P, is extremely limited despite the importance of m as a gauge of mechanical reliability. In Part I of this study, m is determined for 441 sintered hydroxyapatite (HA) specimens fractured in

Xiaofeng Fan; Eldon D Case; Fei Ren; Yutian Shu; Melissa Baumann

2012-01-01

318

Microwave accelerated synthesis of nanosized calcium deficient hydroxyapatite.  

PubMed

Rapid synthesis of calcium deficient hydroxyapatite (CDHA, Ca(10-x)(HPO4)x(PO4)(6-x)(OH)(2-x)) with Ca/P ratio 1.5 was done by precipitation using calcium nitrate tetra-hydrate and phosphoric acid and subsequently subjecting to microwave irradiation in a domestic microwave oven for 15 min. Transmission electron microscopy analysis shows needle like morphology of CDHA having length 16-39 nm and width 7-16 nm. The synthesized CDHA has the characteristic HPO4(2-) vibration band at 875 cm(-1) in Fourier transform infrared (FT-IR) spectra. The X-ray powder diffraction (XRD) analysis shows a pattern corresponding to stoichiometric hydroxyapatite (HA) with broad peaks suggesting that CDHA particles were nanosized. Fourier transform Raman spectroscopy (FT-Raman) do not indicate any fluorescence band that is characteristic of non-stoichiometric HA. The thermal decomposition of CDHA to beta tricalcium phosphate (beta-TCP) was also studied for the additional confirmation. The nanosized CDHA was found to be stable up to 600 degrees C. PMID:15747179

Siddharthan, A; Seshadri, S K; Sampath Kumar, T S

2004-12-01

319

Synthesis of antimicrobial silver/hydroxyapatite nanocomposite by gamma irradiation  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (AgNPs) were synthesized through ?-irradiation reduction of silver ions into hydroxyapatite as a solid support. The formation of AgNPs incorporated in the hydroxyapatite composite was studied as a function of ?-irradiation doses. The X-ray diffraction and transmission electron microscopy (TEM) measurements showed the fabrication of face-centered cubic AgNPs with a mean diameter of about 39 nm at 20 kGy absorbed dose. When the absorbed dose increases from 20 to 40 kGy the size of AgNPs particles partially increases, while with increasing absorbed dose from 40 to 60 kGy the particle diameters decreases. In addition, the results of XRD analysis indicated that increasing of ?-irradiation doses from 20 to 40 kGy enhances the concentration of AgNPs, without inducing significant changes in degree of HA crystallinity. The antibacterial test study of samples against Escherichia coli indicated a significant enhancement in the antibacterial property of Ag/HA nanocomposites.

Akhavan, A.; Sheikh, N.; Khoylou, F.; Naimian, F.; Ataeivarjovi, E.

2014-05-01

320

Post-spray hot isostatic pressing of plasma sprayed Ti?6Al?4V\\/hydroxyapatite composite coatings  

Microsoft Academic Search

A series of Ti?6Al?4V\\/hydroxyapatite (HA) composite coating was produced by plasma spraying. Several compositions (20, 33 and 80 wt.% HA) were prepared. Subsequent examination of the coatings showed them to have a high level of porosity. However, some amount of porosity, within a specified size range, may be desirable in biomedical applications to enhance bony tissue ingrowth, although inter-lamella pores

K. A. Khor; C. S. Yip; P. Cheang

1997-01-01

321

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

322

In-vitro forming of calcium phosphate layer on sol–gel hydroxyapatite-coated metal substrates  

Microsoft Academic Search

In-vitro deposition of calcium phosphate layer (CPL) on metallic substrate requires special surface preparation in order to provide an interfacial bond. In this work 316 stainless steel surface is modified through deposition of a thin film (~0.5 µm) of sol–gel hydroxyapatite (SG-HA). This well-bonded film acts as an intermediary and nucleation surface of the CPL film. The SG-HA films were

D.-M. Liu; Q. Yang; T. Troczynski

2002-01-01

323

Friction properties of nano-hydroxyapatite reinforced poly(vinyl alcohol) gel composites as an articular cartilage  

Microsoft Academic Search

Nano-hydroxyapatite reinforced poly(vinyl alcohol) gel (nano-HA\\/PVA gel) composite has been proposed as a promising biomaterial, especially used as an articular cartilage repair biomaterial. In this paper, nano-HA\\/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze–thaw cycle process. The effects of various factors on the friction coefficient of the gel composites and stainless steel ball counterpart

Yusong Pan; Dangsheng Xiong

2009-01-01

324

Microstructural self-healing effect of hydrothermal crystallization on bonding strength and failure mechanism of hydroxyapatite coatings  

Microsoft Academic Search

Hydroxyapatite coatings (HACs) are synthesized on Ti–6Al–4V substrates using the plasma spraying process followed by autoclaving hydrothermal treatment at 125 and 150°C. The quantitative analysis of X-ray diffraction indicates that the hydrothermal treatment is available to promote HA crystallization and further eliminate the amorphous and impurity phases of the HACs. The microstructural self-healing effect of hydrothermally treated HA coatings (HT-HACs)

Chung-Wei Yang; Truan-Sheng Lui

2008-01-01

325

Human periodontal ligament fibroblasts stimulated by nanocrystalline hydroxyapatite paste or enamel matrix derivative. An in vitro assessment of PDL attachment, migration, and proliferation  

Microsoft Academic Search

We determined the effects of soluble or coated nanocrystalline hydroxyapatite paste (nano-HA) and enamel matrix derivative\\u000a (EMD) on proliferation, adhesion, and migration of periodontal ligament fibroblasts (PDLs). Cultured PDLs were stimulated\\u000a with nano-HA paste or EMD in a soluble form or were coated to the surface of cell culture dishes. Proliferation of PDLs on\\u000a coated nano-HA and EMD was quantified

Adrian Kasaj; Brita Willershausen; Rüdiger Junker; Stefan-Ioan Stratul; Mirko Schmidt

326

Fabrication and adsorption characterizations of porous glass ceramic microspheres  

Microsoft Academic Search

A method to fabricate the porous glass ceramic microspheres is reported. The fabricated glass microspheres and the porous glass ceramic microspheres are characterized by scanning electroscopy (SEM) and transmission electron microscopy (TEM), respectively. The sizes of glass microspheres and the pore diameters of the porous glass ceramic microspheres are estimated, respectively. The adsorption properties of the porous glass ceramic microspheres

Yun Wu; Hao Lv; Jufang Tong; Aimei Liu; Yaoming Ding; Xunong Yi; Qianguang Li; Xinmin Wang

2010-01-01

327

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.

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

2014-01-01

328

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

329

Actinide Mononitride Microspheres and Process.  

National Technical Information Service (NTIS)

The present invention relates to spherical mononitride reactor fuel particles and processes for making same. Crystalline microspheres containing actinide mononitride having a density of at least 90 percent of theoretical are prepared by converting sol-gel...

T. A. Gens

1975-01-01

330

Microsphere Separation Techniques. Final Report.  

National Technical Information Service (NTIS)

A multiple contact adhesion model has been derived to explain the charge observed on silica dust. This model has good agreement with the observed adhesion of microspheres and microballoons. From theoretical arguments, it appeared feasible that surface aco...

1977-01-01

331

On the microstructure of biocomposites sintered from Ti, HA and bioactive glass.  

PubMed

Sintering reactions and fine structures of the biocomposites prepared from powder mixtures of titanium ( alpha -Ti), hydroxyapatite (HA) and bioactive glass (BG) (SiO2-CaO-P2O5-B2O3-MgO-TiO2-CaF2) were investigated by X-ray diffraction and transmission electron microscopy. The results showed that complex reactions among the starting materials mainly depended on the initial Ti/HA ratios as well as the sintering temperatures. And the reaction could be expressed by the following illustrative equation: Ti+Ca10(PO4)6(OH)2-->CaTiO3+CaO+TixPy+(Ti2O)+(Ca4P2O9)+H2O. PMID:15020110

Ning, C Q; Zhou, Y

2004-08-01

332

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

333

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

PubMed

The aim of current study is to investigate the in vitro and in vivo behavior of dental pulp stem cells (DPSCs) seeded on electrospun poly(epsilon-caprolactone) (PCL)/gelatin scaffolds with or without the addition of nano-hydroxyapatite (nHA). For the in vitro evaluation, DNA content, alkaline phosphatase (ALP) activity and osteocalcin (OC) measurement showed that the scaffolds supported DPSC adhesion, proliferation, and odontoblastic differentiation. Moreover, the presence of nHA upregulated ALP activity and promoted OC expression. Real-time PCR data confirmed these results. SEM micrographs qualitatively confirmed the proliferation and mineralization characteristics of DPSCs on both scaffolds. Subsequently, both scaffolds seeded with DPSCs were subcutaneously implanted into immunocompromised nude mice. Scaffolds with nHA but without cells were implanted as control. Histological evaluation revealed that all implants were surrounded by a thin fibrous tissue capsule without any adverse effects. The cell/scaffold composites showed obvious in vivo hard tissue formation, but there was no sign of tissue ingrowth. Further, the combination of nHA in scaffolds did upregulate the expression of specific odontogenic genes. In conclusion, the incorporation of nHA in nanofibers indeed enhanced DPSCs differentiation towards an odontoblast-like phenotype in vitro and in vivo. PMID:19557787

Yang, Xuechao; Yang, Fang; Walboomers, X Frank; Bian, Zhuan; Fan, Mingwen; Jansen, John A

2010-04-01

334

X-Ray Investigation of Ti-DOPED Hydroxyapatite Coating by Mechanical Alloying  

NASA Astrophysics Data System (ADS)

Ti-addition to hydroxyapatites [Ca10(PO4)6(OH)2-HA] with 5.0 wt.% Ti content, was successfully deposited on titanium substrate by mechanical alloying (MA) method. The X-ray Diffraction (XRD) data indicated that some changes take place in the HA lattice as well as in the Ti substrate. The coating thickness of the as-synthesized sample was about 91.1 ?m. Ti incorporation into the apatite structure caused lattice shrinkage. The heat treated sample shows that dominant phase was HA up to 600°C. The Ti-doped HA steadily transformed to ?- and ?-tricalcium phosphate at 800°C. Scanning Electron Microscopy (SEM) observations revealed cracks above the temperature of 600°C. The presence of cracks could be due to the difference in coefficients of thermal expansion of Ti-doped HA and Ti-alloy substrate.

Hannora, A.; Mamaeva, A.; Mansurov, Z.

335

Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.  

PubMed

An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1?m. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions. PMID:24802965

Parakhonskiy, B V; Svenskaya, Yu I; Yashchenok, A ?; Fattah, H A; Inozemtseva, O A; Tessarolo, F; Antolini, R; Gorin, D A

2014-06-01

336

Sintering behaviour of hydroxyapatite bioceramics.  

PubMed

The sintering behaviour of a commercial HA and synthesized HA was investigated over the temperature range of 700 degrees C to 1400 degrees C in terms of phase stability, bulk density, Young's modulus and Vickers hardness. In the present research, a wet chemical precipitation reaction was successfully employed to synthesize a submicron, highly crystalline, high purity and single phase stoichiometric HA powder that is highly sinteractive particularly at low temperature regimes below 1100 degrees C. It has been revealed that the sinterability of the synthesized HA was significantly greater than that of the commercial HA. The temperature for the onset of sintering and the temperature required to achieve densities above 98% of theoretical value were approximately 150 degrees C lower for the synthesized HA than the equivalent commercial HA. Nevertheless, decomposition of HA phase upon sintering was not observed in the present work for both powders. PMID:19024998

Ramesh, S; Tan, C Y; Aw, K L; Yeo, W H; Hamdi, M; Sopyan, I; Teng, W D

2008-07-01

337

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.

338

Incorporation of carbonate and magnesium ions into synthetic hydroxyapatite: The effect on physicochemical properties  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA), magnesium containing hydroxyapatite (Mg-HA) and magnesium containing carbonated apatite (Mg-CHA) were prepared by the wet chemical synthesis. Various analytical methods, such as X-ray diffraction (XRD), infrared spectroscopy (FTIR) and high-resolution solid-state nuclear magnetic resonance (SSNMR) were applied to characterize physicochemical properties of the studied samples. The synthesized apatites were found nanocrystalline with the absence of additional phases. Mg-CHA was less crystalline than the other samples and presented the highest specific surface area. The material had chemical composition and morphological features similar to that of bone mineral. Chemical differences between crystal surface and crystal interior of the analyzed samples (i.e. Mg 2+, CO32-, HPO42- and water distribution) were discussed.

Kolmas, Joanna; Jaklewicz, Andrzej; Zima, Aneta; Bu?ko, Miros?aw; Paszkiewicz, Zofia; Lis, Jerzy; ?lósarczyk, Anna; Kolodziejski, Waclaw

2011-02-01

339

Hardystonite improves biocompatibility and strength of electrospun polycaprolactone nanofibers over hydroxyapatite: a comparative study.  

PubMed

The aim of this study was to compare physico-chemical and biological properties of hydroxyapatite (HA) and hardystonite (HS) based composite scaffolds. Hardystonite (Ca2ZnSi2O7) powders were synthesized by a sol-gel method while polycaprolactone-hardystonite (PCL-HS) and polycaprolactone-hydroxyapatite (PCL-HA) were fabricated in nanofibrous form by electrospinning. The physico-chemical and biological properties such as tensile strength, cell proliferation, cell infiltration and alkaline phosphatase activity were determined on both kinds of scaffolds. We found that PCL-HS scaffolds had better mechanical strength compared to PCL-HA scaffolds. Addition of HA and HS particles to PCL did not show any inhibitory effect on blood biocompatibility of scaffolds when assessed by hemolysis assay. The in vitro cellular behavior was evaluated by growing murine adipose-tissue-derived stem cells (mE-ASCs) over the scaffolds. Enhanced cell proliferation and improved cellular infiltrations on PCL-HS scaffolds were observed when compared to HA containing scaffolds. PCL-HS scaffolds exhibited a significant increase in alkaline phosphatase (ALP) activity and better mineralization of the matrix in comparison to PCL-HA scaffolds. These results clearly demonstrate the stimulatory role of Zn and Si present in HS based composite scaffolds, suggesting their potential application for bone tissue engineering. PMID:23623116

Jaiswal, Amit K; Chhabra, Hemlata; Kadam, Sachin S; Londhe, Kishore; Soni, Vivek P; Bellare, Jayesh R

2013-07-01

340

Preparation and Functional Assessment of Composite Chitosan-Nano-Hydroxyapatite Scaffolds for Bone Regeneration  

PubMed Central

Composite chitosan-nano-hydroxyapatite microspheres and scaffolds prepared using a co-precipitation method have shown potential for use in bone regeneration. The goal of this research was to improve the functional properties of the composite scaffolds by modifying the fabrication parameters. The effects of degree of deacetylation (DDA), drying method, hydroxyapatite content and an acid wash on scaffold properties were investigated. Freeze-dried 61% DDA scaffolds degraded faster (3.5 ± 0.5% mass loss) than air-dried 61% DDA scaffolds and 80% DDA scaffolds, but had a lower compressive modulus of 0.12 ± 0.01 MPa. Air-dried 80% DDA scaffolds displayed the highest compressive modulus (3.79 ± 0.51 MPa) and these scaffolds were chosen as the best candidate for use in bone regeneration. Increasing the amount of hydroxyapatite in the air-dried 80% DDA scaffolds did not further increase the compressive modulus of the scaffolds. An acid wash procedure at pH 6.1 was found to increase the degradation of air-dried 80% DDA scaffolds from 1.3 ± 0.1% to 4.4 ± 0.4%. All of the formulations tested supported the proliferation of SAOS-2 cells.

Reves, Benjamin T.; Jennings, Jessica A.; Bumgardner, Joel D.; Haggard, Warren O.

2012-01-01

341

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

342

Nanostructuring and texturing of pulsed laser deposited hydroxyapatite thin films  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) [Ca_10(PO_4)_6(OH)_2] is commonly deposited onto orthopedic and dental metallic implants to speed up bone formation around devices, allowing earlier stabilization in a patient. Pulsed laser deposition (PLD) is a suitable means of placing thin HA films on these implants because of its control over stoichiometry, crystallinity, and nanostructure. These characteristics determine the mechanical properties of the films that must be optimized to improve the performance of load-bearing implants and other devices that undergo bone insertion. We have used PLD to produce nanostructured and preferentially oriented HA films and evaluated their mechanical properties. Pure, highly crystalline HA films on Ti-6Al-4V substrates were obtained using a KrF excimer laser (248nm) with energy density of 4-8 J/cm^2 and deposition temperature of 500-700^rcC. Scanning electron and atomic force microscopies reveal that our careful manipulation of energy density and substrate temperature has led to films made up of HA grains in the nanometer scale. Broadening of x-ray diffraction peaks as a function of deposition temperature suggests it may be possible to control the film nanostructure to a great extent. X-ray diffraction also shows that as the laser energy density is increased in the 4-8 J/cm^2 range, the hexagonal HA films become preferentially oriented along the c-axis perpendicular to the substrate. Texture, nanostructure, and phase make-up all significantly influence the mechanical properties. We will discuss how each of these factors affects hardness and Young's modulus of the HA films as measured by nanoindentation.

Kim, Hyunbin; Catledge, Shane; Vohra, Yogesh; Camata, Renato; Lacefield, William

2003-03-01

343

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

344

Fetal and postnatal mouse bone tissue contains more calcium than is present in hydroxyapatite  

Microsoft Academic Search

It has been shown for developing enamel and zebrafish fin that hydroxyapatite (HA) is preceded by an amorphous precursor, motivating us to examine the mineral development in mammalian bone, particularly femur and tibia of fetal and young mice. Mineral particle thickness and arrangement were characterized by (synchrotron) small-angle X-ray scattering (SAXS) combined with wide-angle X-ray diffraction (WAXD) and X-ray fluorescence

C. Lange; C. Li; I. Manjubala; W. Wagermaier; J. Kühnisch; M. Kolanczyk; S. Mundlos; P. Knaus; P. Fratzl

2011-01-01

345

Synthesis and characterization of sol–gel hydroxyapatite coatings deposited on porous NiTi alloys  

Microsoft Academic Search

A hydroxyapatite (HA) coating was deposited onto a porous NiTi alloy via dip-coating using a sol–gel procedure with triethyl phosphite and calcium nitrate as phosphorus and calcium precursors, respectively. Adjusting the concentration and viscosity of the sol as well as changing the spin-coating rotational velocity or dip-coating times, enabled uniform coatings with controllable thickness at the sub-micron scale to be

J. X. Zhang; R. F. Guan; X. P. Zhang

2011-01-01

346

Strontium-Substituted Hydroxyapatite Thin Films Grown by Pulsed Laser Deposition  

NASA Astrophysics Data System (ADS)

Strontium substitution for calcium in the hydroxyapatite structure has lately attracted growing interest due to its beneficial effects on both bone formation and prevention of bone resorption. Coating Ti implants with Sr2+ substituted hydroxyapatite is expected to enhance the bioactivity of the surface and stimulate bone apposition. To this end, we deposited thin films of hydroxyapatite with different substitutions of Sr2+ for Ca2+ on Ti substrates by Pulsed Laser Deposition (PLD). Solid solutions of Sr-Ca hydroxyapatites [Ca10-xSrxHA(x = 0-1)] were prepared by direct synthesis in aqueous medium at 90°C. Sr2+ insertion led to a decrease of crystallinity degree, which accounted for the simultaneous reduction of the crystal dimensions. For PLD experiments, we used an UV excimer (KrF*) laser source (248 nm, ˜7.4 ns) operating at a repetition rate of 2 Hz. The fluence during target irradiation was set at 2.4 J/cm2, and substrate temperature kept at 400°C. The depositions were performed from HA at different degrees of Sr2+ substitution for Ca2+ (x = 0; 0.1; 0.5; 1). All structures were post-treated in a H2O enriched atmosphere for 6 h. The results of structural and morphological characterizations carried out on the obtained structures indicated that the coatings, which adhered well to the substrates, were made of crystalline HA and contained strontium with a (Ca + Sr)/P molar ratio close to the stoichiometric value of HA.

Capuccini, C.; Sima, F.; Axente, E.; Boanini, E.; Gazzano, M.; Bigi, A.; Mihailescu, I. N.

347

Comparison of the osteoblastic activity conferred on Si-doped hydroxyapatite scaffolds by different osteostatin coatings  

Microsoft Academic Search

Parathyroid hormone-related protein (107-111) (osteostatin) induces osteogenic effects in osteoblasts in vitro and in regenerating bone in mice and rabbits. In this study we used osteoblastic MC3T3-E1 cell cultures to evaluate and compare the bioactivity of this peptide either adsorbed or covalently bound (by its C-terminus) to Si-doped hydroxyapatite (Si-HA) scaffolds after organic (–NH2) functionalization. By these means osteostatin can

Miguel Manzano; Daniel Lozano; Daniel Arcos; Sergio Portal-Núñez; Carlos Lopez la Orden; Pedro Esbrit; María Vallet-Regí

2011-01-01

348

Microstructure and mechanical properties of spark plasma sintered zirconia-hydroxyapatite nano-composite powders  

Microsoft Academic Search

ZrO2-hydroxyapatite composites spark plasma sintered (SPS) at 1075±25°C involve inter and intra particle porosities. The porosity level in the compacts (<3–42%) varied with sintering pressure (4.5–17.3 MPa), and apparently contributed to the increase in indentation fracture toughness. Rietveld phase analysis revealed that the powders and SPS compacts composed of HA, tricalcium phosphate (TCP), zirconia (t- and c-ZrO2) and CaZrO3. The

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

2005-01-01

349

Development of phosphate inter layered hydroxyapatite coating for stainless steel implants  

Microsoft Academic Search

As zinc phosphate acts as a versatile material for potential biomedical applications, it was modified into a thin layer coating for orthopaedic applications in the present study. A unique layering system consisting of pure substrate (316L SS), thick Fe–Zn alloy layers, thin ZnP layer on which a hydroxyapatite (HA) layer, was developed and studied. The composition, surface morphology and corrosion

S. M. A. Shibli; A. C. Jayalekshmi

2008-01-01

350

Migration of Co-cultured Endothelial Cells and Osteoblasts in Composite Hydroxyapatite\\/Polylactic Acid Scaffolds  

Microsoft Academic Search

Regeneration of bone in large segmental bone defects requires regeneration of both cortical bone and trabecular bone. A scaffold\\u000a design consisting of a hydroxyapatite (HA) ring surrounding a polylactic acid (PLA) core simulates the structure of bone and\\u000a provides an environment for indirect and direct co-culture conditions. In this experiment, human umbilical vein endothelial\\u000a cells (EC) and normal human primary

Amita R. Shah; Sarita R. Shah; Sunho Oh; Joo L. Ong; Joseph C. Wenke; C. Mauli Agrawal

351

A new bone repair scaffold combined with chitosan\\/hydroxyapatite and sustained releasing icariin  

Microsoft Academic Search

Icariin, a plant-derived flavonol glycoside, has been proved as an osteoinductive agent for bone tissue engineering. A new\\u000a bone repair scaffold was generated by thorough mixing of icariin and chitosan\\/hydroxyapatite (icariin-CS\\/HA) using freeze-drying\\u000a technigue. Characteristics of morphology, mechanical properties, biocompatibility, drug release behavior and bone repair abilities\\u000a in vivo were evaluated. The results show that drug loading process of icariin

Tao Wu; KaiHui Nan; JingDi Chen; Dan Jin; Shan Jiang; PeiRan Zhao; JunChang Xu; Hao Du; XiaoQiang Zhang; JianWei Li; GuoXian Pei

2009-01-01

352

Synthesis of nanocrystalline hydroxyapatite using surfactant template systems: Role of templates in controlling morphology  

Microsoft Academic Search

Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium nitrate and phosphoric acid as starting materials in aqueous phase. Cyclohexane, hexane, and isooctane were used as organic solvents, and Dioctyl sulfosuccinate sodium salt (AOT), dodecyl phosphate (DP), NP5 (poly(oxyethylene)5 nonylphenol ether), and NP12 (poly(oxyethylene)12 nonylphenol ether) as surfactants to make the emulsion. Effect of synthesis parameters, such as

Susanta Kumar Saha; Ashis Banerjee; Shashwat Banerjee; Susmita Bose

2009-01-01

353

Comparative Study on Osteoconductivity by Synthetic Octacalcium Phosphate and Sintered Hydroxyapatite in Rabbit Bone Marrow  

Microsoft Academic Search

Octacalcium phosphate (OCP) is thought to be a precursor of the mineral crystals in biological apatite. Synthetic OCP has\\u000a been shown to be converted into an apatite structure when implanted in murine calvarial bone, to enhance bone regeneration\\u000a more than synthetic hydroxyapatite (HA), and to degrade faster than biodegradable ?-tricalcium phosphate. This study was designed\\u000a to investigate whether OCP implantation

H. Imaizumi; M. Sakurai; O. Kashimoto; T. Kikawa; O. Suzuki

2006-01-01

354

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.

2014-01-01

355

An amphiphilic degradable polymer/hydroxyapatite composite with enhanced handling characteristics promotes osteogenic gene expression in bone marrow stromal cells.  

PubMed

Electrospun polymer/hydroxyapatite (HA) composites combining biodegradability with osteoconductivity are attractive for skeletal tissue engineering applications. However, most biodegradable polymers such as poly(lactic acid) (PLA) are hydrophobic and do not blend with adequate interfacial adhesion with HA, compromising the structural homogeneity, mechanical integrity and biological performance of the composite. To overcome this challenge, we combined a hydrophilic polyethylene glycol (PEG) block with poly(d,l-lactic acid) to improve the adhesion of the degradable polymer with HA. The amphiphilic triblock copolymer PLA-PEG-PLA (PELA) improved the stability of HA-PELA suspension at 25wt.% HA content, which was readily electrospun into HA-PELA composite scaffolds with uniform fiber dimensions. HA-PELA was highly extensible (failure strain>200% vs. <40% for HA-PLA), superhydrophilic (?0° water contact angle vs. >100° for HA-PLA), and exhibited an 8-fold storage modulus increase (unlike deterioration for HA-PLA) upon hydration, owing to the favorable interaction between HA and PEG. HA-PELA also better promoted osteochondral lineage commitment of bone marrow stromal cells in unstimulated culture and supported far more potent osteogenic gene expression upon induction than HA-PLA. We demonstrate that the chemical incorporation of PEG is an effective strategy to improve the performance of degradable polymer/HA composites for bone tissue engineering applications. PMID:23791675

Kutikov, Artem B; Song, Jie

2013-09-01

356

In vitro apatite formation and its growth kinetics on hydroxyapatite/polyetheretherketone biocomposites.  

PubMed

The formation of biologically equivalent carbonate-containing apatite on the surface of synthetic hydroxyapatite (HA) is an important step leading to good bone healing. In this study, HA-reinforced polyetheretherketone (PEEK) composites were prepared by homogeneous mixing of HA and PEEK powders, compaction, and pressureless sintering. The bioactivity of HA/PEEK composite with 10, 20, 30 and 40 vol% HA was evaluated by immersing the composite disks in the simulated body fluid (SBF) for up to 4 weeks. The surface of composite with 40 vol% HA was covered by a layer of bone-like apatite just after 3 days of immersion, while 10 vol% HA was covered only after 28 days. This apatite layer was characterized by SEM, thin film X-ray diffractometer, attenuated total reflectance-Fourier transform infrared spectrometer (FTIR)/FTIR. Introducing a concept called apatite-forming capacity of SBF, growth kinetics of the apatite layer on the surface of the composite disks was carried out. The growth rate constant increased with HA volume fraction of the composite, suggesting that the bioactivity of the HA/PEEK composite increases with increasing HA volume fraction in the composite. PMID:15585237

Yu, Shucong; Hariram, Kithva Prakash; Kumar, Rajendra; Cheang, Philip; Aik, Khor Khiam

2005-05-01

357

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

PubMed

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

358

Evaluation of thermal stress in hydroxyapatite film fabricated by powder jet deposition.  

PubMed

This study aimed to create a thick hydroxyapatite (HA) film on the surface of a human tooth via a powder jet deposition (PJD) device for dental handpieces, and to examine the microstructural and mechanical properties of the HA film. In particular, the effects of thermal stress on this film were evaluated. The HA film was created by blasting 3.18-?m HA particles, calcinated at 1,200°C, onto the enamel substrate at room temperature and atmospheric pressure. An HA film with an area of 3 mm × 3 mm was prepared and polished. The following HA film parameters were evaluated from the three-dimensional surface profile: surface roughness, Vickers hardness, and bonding strength before and after artificial aging induced by 500 cycles of thermal cycling (5-55°C). The HA particles in the deposited film were densely packed, and the surface of the HA film was unchanged after thermal cycling. There were also no significant differences in the hardness and the bonding strength of the HA film before and after thermal cycling. The HA film created in this study demonstrated excellent microstructural and mechanical properties, even after the application of thermal stress. PMID:24028600

Akatsuka, Ryo; Matsumura, Ken; Noji, Miyoko; Kuriyagawa, Tsunemoto; Sasaki, Keiichi

2013-10-01

359

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.

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

2012-01-01

360

ZrO(2)/hydroxyapatite coating on titanium by electrolytic deposition.  

PubMed

In this study, hydroxyapatite (HA) was coated on a titanium (Ti) substrate over a ZrO(2) layer by the electrolytic deposition method, this double layer coating was then compared with a single layer coating of HA. The HA layer was used to increase the bioactivity and osteoconductivity of the Ti substrate, and the ZrO(2) layer was intended to improve the bonding strength between the HA layer and Ti substrate, and to prevent the corrosion of the Ti substrate. The electrolytic deposition formed an HA layer with a thicknesses of approximately 20 mum, which adhered tightly to the Ti substrate. The bonding strength of the HA/ZrO(2) double layer coating on Ti was markedly improved when compared to that of the HA single coating on Ti. The improvement in bonding strength with the use of a ZrO(2) base layer was attributed to the resulting increase in chemical affinity of the ZrO(2) to the HA layer and to the Ti substrate. The osteoblast-like cells cultured on the HA/ZrO(2) coating surface, proliferated in a similar manner to those on the HA single coating and on the pure Ti surfaces. At the same time, the corrosion resistance of Ti was improved by the presence of the ZrO(2) coating, as shown by a potentiodynamic polarization test. PMID:18853237

Hsu, Hsueh-Chuan; Wu, Shih-Ching; Yang, Chih-Hsiung; Ho, Wen-Fu

2009-02-01

361

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.

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

2008-01-01

362

Structural characterization of nanocrystalline hydroxyapatite and adhesion of pre-osteoblast cells  

NASA Astrophysics Data System (ADS)

Nanocrystalline hydroxyapatite (Nano HA), a prototype of minerals of bones and teeth, attracts increasing interest in medicine and dentistry. Different parameters for synthesis and post-treatment were investigated to determine their effects on crystallinity of nano HA, and in vitro cell responses to nano HA were studied. XRD and TEM analyses indicate that the crystallinity of nano HA synthesized by a chemical method was within the range of 15-50 nm, which is adapted to natural minerals of hard tissues. Increasing the ageing temperature significantly increased the crystallinity of nano HA, while lengthening the ageing time or varying the post-ageing drying process did not have any influence on its crystallinity. Nano HA annealed between 300 and 900 °C showed a small increase in crystallinity with increasing annealing temperature due to the long-range ordering effect. Cell attachment and spreading on nano HA were lower than those on pure titanium, and decreased as the crystallinity of nano HA increased. However, cells on nano HA demonstrated well-developed filopodia and lamelliopodia, which facilitate migration of the cells on it. This may benefit osteogenesis at the interface between bone and nano HA in vivo.

Zhu, Xiaolong; Eibl, Oliver; Berthold, Christoph; Scheideler, Lutz; Geis-Gerstorfer, Jürgen

2006-06-01

363

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.

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

2013-01-01

364

Temperature driven morphological changes of chemically precipitated hydroxyapatite nanoparticles.  

PubMed

Hydroxyapatite (HA) is synthesized by a wet chemical route using calcium hydroxide and ortho-phosphoric acid at various temperatures (40, 80, and 100 degrees C). X-ray diffraction of the precipitate particles revealed HA as the predominant phase (>99%) with a small amount of beta-tricalcium phosphate. Fourier transform infrared spectroscopy indicated the presence of carbonate substitution, which decreased with increasing temperature. Transmission electron microscopy observations revealed needle-shaped particles with a high aspect ratio at 40 degrees C, which changed to spheroidal when the precipitation temperature was increased to 100 degrees C. The changes in the morphology with temperature were analyzed taking into account the driving force for the HA precipitation and the supersaturation level of Ca2+ and PO4(3-) ions with respect to HA. The analysis indicated that the supersaturation level of the reactants, especially the concentration of Ca2+ ions, played a predominant role on the precipitate morphology for this classical acid-base reaction. PMID:15986652

Kumar, R; Prakash, K H; Cheang, P; Khor, K A

2004-06-22

365

Analysis of human alveolar osteoblast behavior on a nano-hydroxyapatite substrate: an in vitro study  

PubMed Central

Background Nano-hydroxyapatite (nHA) is a potential ideal biomaterial for bone regeneration. However, studies have yet to characterize the behavior of human osteoblasts derived from alveolar bone on nHA. Thus, the aim of the present study was to evaluate the influence of nHA on the adhesion, proliferation and differentiation of these alveolar bone-derived cells. Methods Primary human alveolar osteoblasts were collected from the alveolar ridge of a male periodontal patient during osseous resective surgery and grown on culture plates coated with either polylysine or polylysine with nano-hydroxyapatite (POL/nHA) composite. The cells were grown and observed for 14 days, and then assessed for potential modifications to osteoblasts homeostasis as evaluated by quantitative reverse transcriptase-polymerase chain reaction (real time RT-PCR), scanning electron microscopy and atomic force microscopy. Results Real time PCR revealed a significant increase in the expression of the selected markers of osteoblast differentiation (bone morphogenetic protein (BMP)-2,-5,-7, ALP, COLL-1A2, OC, ON) in cells grown on the POL/nHA substrate. In addition, as compared with the POL surface, cells grown on the POL/nHA substrate demonstrated better osteoconductive properties, as demonstrated by the increase in adhesion and spreading, likely as a result of the increased surface roughness of the composite. Conclusions The increased expression of BMPs and osteoinductive biomarkers suggest that nano-hydroxyapatite may stimulate the proliferation and differentiation of local alveolar osteoblasts and thus encourage bone regeneration at sites of alveolar bone regeneration.

2014-01-01

366

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

367

Hydrophilic albumin microspheres as cytarabine carriers  

Microsoft Academic Search

The surface of cytarabine-entrapped albumin microspheres was modified by coupling with glycine. Compared with conventionally\\u000a prepared albumin microspheres, the surface modified albumin microspheres showed remarkably increased hydrophilicity, good\\u000a dispersability in aqueous medium and reduced aggregation during storage which met the requirements of injectable drug carriers\\u000a in aqueous vehicle.In vitro cytarabine release from hydrophilic albumin microspheres (HAM) was a function of

Chong-Kook Kim; Myung-Hoa Chung; Yu-Kyoung Oh; Woon-Lyong Lah

1993-01-01

368

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

369

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.

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

370

Synthesis Methods of Magnetic Composite Microspheres  

Microsoft Academic Search

Organic-inorganic composite microspheres have attracted attention because it has found some potential applications in many fields. In this paper, the usual synthesis methods and the problems in the preparation of magnetic composite microspheres of composite microspheres were discussed, and some novel methods of surface modification of the magnetic inorganic particle were summarized. Two new synthesis methods, DPE and ATRP, were

Zhang Hepeng; Zhang Qiuyu; Xie Gang; Zhang Junping; Zhao Wen; Yan Xin; Han Lei

371

Fundamentals and applications of microsphere resonator circuits  

Microsoft Academic Search

Microsphere resonator circuits have emerged as a technology allowing integration of cavities in all three spatial dimensions (3D) in chip-scale structures. This presentation is devoted to fabrication, optical properties and applications of mesoscale structures formed by microspheres. The ldquomesophotonicsrdquo properties of such structures stem from two properties of individual dielectric microspheres with dimensions comparable to the wavelength of light: (i)

Vasily N. Astratov

2009-01-01

372

Review: Radioactive Microspheres for Medical Applications  

Microsoft Academic Search

Summary This paper reviews the preparation and application of radioactive microspheres for medical purposes. It first discusses the properties of relevant radioisotopes and then explores the diagnostic uses of gamma- emitter labeled microspheres, such as blood flow measurement and imaging of the liver and other organs. The therapeutic uses of alpha- and beta-emitting microspheres, such as radioembolization, local tumor therapy

Urs Häfeli

373

Electrodeposition of hydroxyapatite coatings in basic conditions  

Microsoft Academic Search

Hydroxyapatite films have been grown in this work by an electrodeposition method involving both physical and chemical processes and presenting several differences with respect to other reported works. Description of the coating formation is based on the evolution of current through the sample placed as positive electrode in the basic electrolyte. The characterisation of hydroxyapatite films is of special importance

Miguel Manso; Carmen Jiménez; Carmen Morant; Pilar Herrero; JM Mart??nez-Duart

2000-01-01

374

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

375

Comparison of nanocrystalline hydroxyapatite and synthetic resorbable hydroxyapatite graft in the treatment of intrabony defects: A clinical and radiographic study  

PubMed Central

Background: The aim of this study is to compare, clinically and radiographically, the effectiveness of nanocrystalline hydroxyapatite (NHA) and synthetic resorbable hydroxyapatite (HA) in the treatment of intrabony defects. Materials and Methods: Ten subjects with bilateral defects, with probing depth (PD) 6-9 mm and radiographic evidence of an intraosseous component ?4 mm participated in the present study. Subjects were allocated randomly to treatment with NHA (test group) or HA (control group). At baseline, 3 and 6 months after surgery, the following clinical parameters were recorded: Plaque index, gingival index, PD, relative attachment level (RAL), and radiographic reduction in intrabony defect. Results: At 6 months following therapy, the test group showed a reduction in mean PD from 6.4 ± 0.843 to 3.3 ± 0.8232 mm and a change in mean RAL from 12.9 ± 1.197 to 10.1 ± 0.7378 mm, whereas in the control group the mean PD decreased from 7.65 ± 1.8566 to 3.9 ± 1.1005 mm, and mean RAL decreased from 13.9 ± 0.9944 to 10.7 ± 0.6749 mm. On comparison of the mean difference in probing depth between the two groups after the unpaired t-test was applied at baseline, 3 months and 6 months, scores were found to be statistically non-significant (P > 0.01). Conclusion: The results of the present study indicate that both NHA and conventional HA led to the improvement of clinical and radiographic parameters over the course of the study. However, the test group did not show any significant improvement over the control group.

Bansal, Mansi; Kaushik, Mayur; Khattak, Brig B. P.; Sharma, Anamika

2014-01-01

376

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

377

Investigation of the voltage and time effects on the formation of hydroxyapatite-containing titania prepared by plasma electrolytic oxidation on Ti–6Al–4V alloy and its corrosion behavior  

Microsoft Academic Search

Producing titania and hydroxyapatite (HA) bioceramic coating on titanium alloys increases corrosion resistance and biocompatibility of these alloys. Plasma electrolytic oxidation (PEO) is one of the effective techniques for producing this type of coating. This method produces coatings with enough thickness and appropriate adhesion. In this study, titania and HA were directly produced on Ti–6Al–4V by applying PEO process in

M. Montazeri; C. Dehghanian; M. Shokouhfar; A. Baradaran

2011-01-01

378

Comparison of TCP and TCP/HA Hybrid Scaffolds for Osteoconductive Activity  

PubMed Central

Two types of porous ceramic scaffolds were prepared, consisting of ?-tricalcium phosphate (TCP) or the mixed powder of TCP and hydroxyapatite (HA) at a 2:1 mass ratio. A variety of methods have been used to fabricate bone scaffolds, while the sintering approach was adopted in this work. An extremely high temperature was used on sintering that proposed to consolidate the ceramic particles. As revealed by SEM, a well opened pore structure was developed within the scaffolds. The ?-values were measured to be of 73.3° and 6.5° for the composite scaffold and TCP sample, respectively. According to XRD patterns, the existence of grains coalescence and partial bonding between HA and TCP powders was demonstrated. Scaffold mechanical property in the term of flexural strength was also determined. The result showed decreasing of the strength by HA supplement, suggesting the more brittle characteristic of HA in comparison with TCP. By soaking the composite scaffold in PBS for a period of 2 weeks, transformation from particles to flank-like crystalline was clearly observed. Such change was found to be favorable for cell attachment, migration, and growth. By implanting cell-seeded scaffolds into nude mice, an abundant osseous extracellular matrix was identified for the composite implants. In contrast, the matrix was minimally detected in TCP implanted samples. Thus, the composite scaffold was found superior for hard tissue regeneration.

Wongwitwichot, P; Kaewsrichan, J; Chua, K.H; Ruszymah, B.H.I

2010-01-01

379

Bonding capacity in bone of HIP-processed HA-coated titanium: mechanical and histological investigations.  

PubMed

The main problems using plasma-sprayed hydroxyapatite (HA) as a coating material on metallic implants are its porosity, low fatigue strength, and weak adherence to the metallic substrate. To overcome these problems a new technique using hot isostatic pressing (HIP) has been developed for producing HA-coated titanium (Ti) implants. Specimens produced at a maximum temperature of 850 degrees C and a maximum pressure of 720 bar displayed a dense, glassy, 25-microns thick coating with small amounts of porosity and a mean surface roughness of 0.7 microns, as compared with 1.6 microns for sandblasted Ti. Twenty conical HA-coated (720 and 100 bar pressure) and 10 noncoated Ti implants were inserted through the cortex of the lower margin of the mandibles of sheep and allowed to heal for 60 days. Push-out tests for implants processed at 720 bar pressure showed substantially higher bone/implant bonding values than for sandblasted Ti implants. Histological studies indicated a direct contact and probably chemical bonding between bone tissue and the HA coatings. The area of contact was almost 3 times as large as for the Ti implants. The adherence of the 100-bar coating to the Ti surface was inferior to the 720-bar coating, as shown by the loosening of the coatings in several areas. PMID:8582913

Wie, H; Herø, H; Solheim, T; Kleven, E; Rørvik, A M; Haanaes, H R

1995-11-01

380

Low temperature aqueous precipitation of needle-like nanophase hydroxyapatite.  

PubMed

The use of tissue engineered biodegradable porous scaffolds has become an important focus of the biomedical research field. The precursor materials used to form these structures play a vital role in their overall performance thus making the study and synthesis of these selected materials imperative. The authors present a comparison and characterisation of hydroxyapatite (HA), a popular calcium phosphate (CaP) biomaterial, synthesised by an aqueous precipitation (AP) method. The influence of various reaction conditions on the phase, crystallinity, particle size as well as morphology, molecular structure, potential in-vivo bioactivity and cell viability were assessed by XRD, SEM and TEM, FTIR, a simulated body fluid (SBF) test and a live/dead assay using MC3T3 osteoblast precursor cells, respectively. Naturally carbonated nanoparticles of HA with typically needle-like morphology were synthesised by the reported AP method. Initial pH was found to influence the crystallisation process and determine the CaP phase formed as well as the resultant particle and crystallite sizes. A marked change in particle morphology was also observed above pH 9. The use of toluene as a replacement solvent for water up to 60% was found to reduce the crystallinity of as-synthesised HA. This has marked influence on the effect of ethanolamine (5 wt%), which was found to improve HA crystallinity. SEM and EDS were used to confirm the growth of carbonated apatite on the surface of HA pellets immersed in SBF for up to 28 days. Cell culture results revealed viable cells on all samples where pH was controlled and maintained at 10-11 during precipitation, including those that used ethanolamine and toluene in preparation. When the initial alkali pH was not maintained non-viable cells were observed on HA substrates. PMID:24006049

Cox, Sophie C; Jamshidi, Parastoo; Grover, Liam M; Mallick, Kajal K

2014-01-01

381

Fabrication and mechanical evaluation of hydroxyapatite/oxide nano-composite materials.  

PubMed

In the current study, the semiconducting metal oxides such as nano-ZnO and SiO2 powders were prepared via sol-gel technique and conducted on nano-hydroxyapatite (nHA) which was synthesized by chemical precipitation. The properties of fabricated nano-structured composites containing different ratios of HA, ZnO and SiO2 were examined using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. The effect of the variation of ratios between the three components on mechanical, microstructure and in-vitro properties was assessed to explore the possibility of enhancing these properties. The results proved that the mechanical properties exhibited an increment with increasing the ZnO content at the extent of HA. In-vitro study proved the formation and nucleation of apatite onto the surface of the fabricated composites after one week of immersion. It is concluded that HA composites containing SiO2 or SiO2/ZnO content had a suitable mechanical properties and ability to form apatite particles onto the composite surface. Based on bioactivity behavior, Si-HA is more bioactive than pure hydroxyapatite and nano-arrangements will provide an interface for better bone formation. Therefore, these nano-composites will be promising as bone substitutes especially in load bearing sites. PMID:23910323

Mohamed, Khaled R; Beherei, Hanan H; El Bassyouni, Gehan T; El Mahallawy, Nahed

2013-10-01

382

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

PubMed

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

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

2011-10-15

383

Morphological Effects of HA on the Cell Compatibility of Electrospun HA/PLGA Composite Nanofiber Scaffolds  

PubMed Central

Tissue engineering is faced with an uphill challenge to design a platform with appropriate topography and suitable surface chemistry, which could encourage desired cellular activities and guide bone tissue regeneration. To develop such scaffolds, composite nanofiber scaffolds of nHA and sHA with PLGA were fabricated using electrospinning technique. nHA was synthesized using precipitation method, whereas sHA was purchased. The nHA and sHA were suspended in PLGA solution separately and electrospun at optimized electrospinning parameters. The composite nanofiber scaffolds were characterized by FE-SEM, EDX analysis, TEM, XRD analysis, FTIR, and X-ray photoelectron. The potential of the HA/PLGA composite nanofiber as bone scaffolds in terms of their bioactivity and biocompatibility was assessed by culturing the osteoblastic cells onto the composite nanofiber scaffolds. The results from in vitro studies revealed that the nHA/PLGA composite nanofiber scaffolds showed higher cellular adhesion, proliferation, and enhanced osteogenesis performance, along with increased Ca+2 ions release compared to the sHA/PLGA composite nanofiber scaffolds and pristine PLGA nanofiber scaffold. The results show that the structural dependent property of HA might affect its potential as bone scaffold and implantable materials in regenerative medicine and clinical tissue engineering.

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

2014-01-01

384

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

PubMed

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

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

2013-02-01

385

Characterization of thermal sprayed hydroxyapatite coatings on some biomedical implant materials.  

PubMed

Purpose: To characterize two thermal sprayed coatings of different particle-sized hydroxyapatite on some biomedical implant materials. Methods: Characterization of the as-sprayed coatings was performed using x-ray diffractometer (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and x-ray mapping techniques. Bond strength of the sprayed coatings measured as per ASTM-C633 standard and cell culture studies were performed to access the biocompatibility of the coatings. Results: The results indicated that, HA coatings of 10 ?m particle sized powder were completely amorphous, while that of 30 ?m sized powder consisted of crystalline HA with minor tetracalcium phosphate (TTCP) and tricalcium phosphate (TCP) phases. This flame spray HA-A and HA-B coatings exhibited higher bond strength (67.8 and 49.3 MPa respectively) in comparison with other thermal spray HA coating techniques reported in literature. In-vitro biocompatibility studies revealed that HA-B coated specimens had good biocompatibility with a human osteosarcoma cell line KHOSNP (R-970-5). Conclusions: These observations show that particle size of HA powders have a significant effect on the phase composition, microstructure, roughness and biocompatibility of deposited coatings. HA-B coatings were found to be metallurgically better than the HA-A coating from the point of view of biomedical applications. PMID:22798233

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

2014-01-01

386

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

387

Silver oxide-containing hydroxyapatite coating has in vivo antibacterial activity in the rat tibia.  

PubMed

Bacterial infection is a serious postoperative complication of joint replacement. To prevent infections related to implantation, we have developed a novel antibacterial coating with Ag-containing hydroxyapatite (Ag-HA). In the present study, we examined the antibacterial activity of Ag-HA implant coatings in the medullary cavity of rat tibiae. Forty 10-week-old rats received implantation of Ag-HA- or HA-coated titanium rods, then were inoculated with ?1.0?×?10(2) colony-forming units of methicillin-resistant Staphylococcus aureus. Bacterial counts were calculated for rats euthanized at 24, 48, and 72?h postoperatively. Serum levels of Ag (in the Ag-HA group only) were calculated for rats euthanized at 24, 48, 72?h and 4 weeks. Radiographic evaluations of bone infection were also performed at 4 weeks. Tibiae from both groups showing infection were evaluated histologically. Significant differences in bacterial counts were seen at 24, 48, and 72?h. Mean concentrations of Ag in serum peaked about 48?h after implantation, then gradually decreased. Mean radiographic scores for infection were significantly lower with Ag-HA implants than with HA implants. Histological examination showed better results for abscesses, bone resorption, and destruction of cortical bone around Ag-HA-coated implants. These results indicate that Ag-HA coatings may help prevent surgical-site infections associated with joint replacement. PMID:23589130

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

2013-08-01

388

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.

2012-01-01

389

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

PubMed Central

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

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

2013-01-01

390

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

PubMed Central

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

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

2012-01-01

391

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

PubMed

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

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

2011-02-01

392

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

393

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

Microsoft Academic Search

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

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

2009-01-01

394

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

PubMed Central

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

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

2013-01-01

395

Preparation and characterisation of nanophase Sr, Mg, and Zn substituted hydroxyapatite by aqueous precipitation.  

PubMed

Hydroxyapatite (HA) substituted with 2 mol% Sr, 10 mol% Mg, and 2 mol% Zn were precipitated under identical alkaline conditions (pH 11) at 20°C from an aqueous solution. As-synthesised materials were confirmed to be phase pure by XRD and samples prepared in air contained surface adsorbed CO2 as observed by FTIR. SEM studies revealed a globular morphology and agglomeration behaviour, typical of precipitated nHA. EDS spectra confirmed nominal compositions and substitution of Sr, Mg and Zn. At the levels investigated cationic doping was not found to radically influence particle morphology. An indication of the potential in-vivo bioactivity of samples was achieved by analysing samples immersed in SBF for up to 28 days by interferometry and complementary SEM micrographs. Furthermore, a live/dead assay was used and confirmed the viability of seeded MC3T3 osteoblast precursor cells on HA and substituted HA substrates up to 7 days of culture. PMID:24411358

Cox, Sophie C; Jamshidi, Parastoo; Grover, Liam M; Mallick, Kajal K

2014-02-01

396

The influence of sintering temperature on the porosity and strength of porous hydroxyapatite ceramics.  

PubMed

The present paper reports on the influence of sintering temperature on the porosity and strength of porous hydroxyapatite (HA). HA powder was first prepared by the sol-gel precipitation method using calcium hydroxide and ortho-phosporic acid. The fine HA powder, measuring <50 microm was then mixed into a slurry with the addition of binder agent, being a mixture of sago and PVA. A small amount of sodium dodecyl sulphate was also used as a foaming agent. Porous HA samples were then prepared via slip casting technique. The surface morphology of the sintered samples was observed under scanning electron microscopy at 20 kV and the compositions were determined via SEM-EDX. A universal testing machine was used to determine the compaction strength of the sintered samples. PMID:15468866

Rusnah, M; Andanastuti, M; Idris, B

2004-05-01

397

Chitosan based hydrogel microspheres as drug carriers.  

PubMed

Chitosan/tripolyphosphate (CHIT/TPP) and chitosan/tripolyphosphate/chondroitin sulfate (CHIT/TPP/CHS) core-shell type microspheres were prepared by polyelectrolyte complexation in order to develop a biocompatible matrix for drug delivery. The continual method using a multi-loop reactor under sterile conditions was applied for microsphere preparation. All the types of microspheres produced were spherical in shape and had a porous structure. The mechanical resistance of the microspheres increased in the presence of CHS as the second polyanion, which toughened the microsphere shell structure. For a drug release application, the process of microsphere preparation was modified by dissolving ofloxacin (OFL), the fluoroquinolone antibiotic, in CHIT solution before complex formation. This study shows the difference in OFL release comparing the microspheres CHIT/TPP and CHIT/TPP/CHS and implies the potential to control this process. PMID:17477445

Vodná, Lucia; Bubeníková, Silvia; Lacík, Igor; Chorvát, Dusan; Bakos, Dusan

2007-05-10

398

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

399

Calcium Hydroxyapatite for Medical Applications  

Microsoft Academic Search

Biocompatible calcium hydroxyapatite, C?10(??4)6(??)2?, is prepared by the alkoxide method. A functional derivative of 1,3-thiazinon (5,6-dihydro-2-methylimino-3-methyl-1,3-thiazine-4-on-6-carboxylic acid-4-chloroanilide) is synthesized, which is expected to combine anti-inflammatory and antiosteoporotic effects. Its pharmacological activity is analyzed using computer simulation. Adsorption of a 1,3-thiazinon solution in acetone on the C?10(??4)6(??)2 surface is studied with the aim of examining the possibility of preparing C?10(??4)6(??)2-based combined

N. A. Zakharov; I. A. Polunina; K. E. Polunin; N. M. Rakitina; E. I. Kochetkova; N. P. Sokolova; V. T. Kalinnikov

2004-01-01

400

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

NASA Astrophysics Data System (ADS)

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

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

401

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

402

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

NASA Astrophysics Data System (ADS)

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

Mensah-Darkwa, Kwadwo

403

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

NASA Astrophysics Data System (ADS)

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

Santhosh, S.; Prabu, S. Balasivanandha

2012-10-01

404

The effect of varying Al2O3 percentage in hydroxyapatite/Al2O3 composite materials: morphological, chemical and cytotoxic evaluation.  

PubMed

Hydroxyapatite (HA) and HA-alumina (HA/Al2O3) composites, with Al2O3 contents of 5, 10, 20, and 30%, were synthesized using a wet precipitation method and sintered at 900 and 1300 degrees C. We investigated the effect of sintering temperature and relative concentration of HA and Al2O3 on the chemical composition, surface morphology, and cytotoxicity of the composite powders. The XRD results show that in the 1300 degrees C composites, HA partially decomposed into CaO which combined with Al2O3 to form different calcium aluminates. For the 900 degrees C composites the CaO phase was not detected, though a Ca/P ratio larger than 1.67 measured by XPS suggests that CaO was present in trace amounts. SEM-EDX analysis indicated that the HA microstructure was affected by the sintering temperature, and this HA is present on the surface of Al2O3 particles. The cytotoxicity of the composites was assessed indirectly using the MTT assay. The short-term effect of leachables was quantified by exposing a L929 mouse fibroblast cell line to the degradation products released by the composites after immersion in the cell culture medium. Degradation products were less toxic to L-929 at lower extract concentrations (10, 50%) than at 100% concentration. Cell viability was also influenced by leachable size. PMID:17584892

Epure, L M; Dimitrievska, S; Merhi, Y; Yahia, L 'H

2007-12-15

405

Robocasting nanocomposite scaffolds of poly(caprolactone)/hydroxyapatite incorporating modified carbon nanotubes for hard tissue reconstruction.  

PubMed

Nanocomposite scaffolds with tailored 3D pore configuration are promising candidates for the reconstruction of bone. Here we fabricated novel nanocomposite bone scaffolds through robocasting. Poly(caprolactone) (PCL)-hydroxyapatite (HA) slurry containing ionically modified carbon nanotubes (imCNTs) was robotic-dispensed and structured layer-by-layer into macrochanneled 3D scaffolds under adjusted processing conditions. Homogeneous dispersion of imCNTs (0.2 wt % relative to PCL-HA) was achieved in acetone, aiding in the preparation of PCL-HA-imCNTs slurry with good mixing property. Incorporation of imCNTs into PCL-HA composition significantly improved the compressive strength and elastic modulus of the robotic-dispensed scaffolds (~1.5-fold in strength and ~2.5-fold in elastic modulus). When incubated in simulated body fluid (SBF), PCL-HA-imCNT nanocomposite scaffold induced substantial mineralization of apatite in a similar manner to the PCL-HA scaffold, which was contrasted in pure PCL scaffold. MC3T3-E1 cell culture on the scaffolds demonstrated that cell proliferation levels were significantly higher in both PCL-HA-imCNT and PCL-HA than in pure PCL, and no significant difference was found between the nanocomposite scaffolds. When the PCL-HA-imCNT scaffold was implanted into a rat subcutaneous tissue for 4 weeks, soft fibrous tissues with neo-blood vessels formed well in the pore channels of the scaffolds without any significant inflammatory signs. Tissue reactions in PCL-HA-imCNT scaffold were similar to those in PCL-HA scaffold, suggesting incorporated imCNT did not negate the beneficial biological roles of HA. While more long-term in vivo research in bone defect models is needed to confirm clinical availability, our results suggest robotic-dispensed PCL-HA-imCNT nanocomposite scaffolds can be considered promising new candidate matrices for bone regeneration. PMID:23184729

Dorj, Biligzaya; Won, Jong-Eun; Kim, Joong-Hyun; Choi, Seong-Jun; Shin, Ueon Sang; Kim, Hae-Won

2013-06-01

406

Nanostructured Si, Mg, CO3 2- Substituted Hydroxyapatite Coatings Deposited by Liquid Precursor Plasma Spraying: Synthesis and Characterization  

NASA Astrophysics Data System (ADS)

In this study, a novel liquid precursor plasma spraying (LPPS) process was used to deposit Si, Mg, CO3 2- substituted hydroxyapatite (HA) coatings (alone and cosubstituted) onto Ti-6Al-4V substrates. Salts of silicon, magnesium, and carbonate elements were directly added into the HA liquid precursor for subsequent plasma spraying. The phase composition, structure, and morphology of all HA coatings were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The results indicated that the trace elements were successfully incorporated into the HA structure and nanostructured coatings were obtained for all doped HA formulations. The incorporation of trace elements into the HA structure reduced its crystallinity, especially when silicon, magnesium and carbonate ions entered simultaneously into the HA structure. FTIR spectra showed that the Si-HA and Mg-HA coatings had decreased intensities in both the O-H and P-O bands and that the CO3 2--HA coating was mainly a B-type carbonate-substituted HA. The results showed that the LPPS process is an effective and simple method to synthesize trace element substituted biomimetic HA coatings with nanostructure.

Huang, Tao; Xiao, Yanfeng; Wang, Shanling; Huang, Yi; Liu, Xiaoguang; Wu, Fang; Gu, Zhongwei

2011-06-01

407

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

PubMed Central

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

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

2014-01-01

408

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

409

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.

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

2012-01-01

410

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

PubMed

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

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

2013-10-01

411

[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

412

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.

Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Rozycka, Dagmara