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1

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

Microsoft Academic Search

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

Qingguo Xu; Jan T. Czernuszka

2008-01-01

2

Localized drugs delivery hydroxyapatite microspheres for osteoporosis therapy  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

3

Porous hydroxyapatite and gelatin/hydroxyapatite microspheres obtained by calcium phosphate cement emulsion.  

PubMed

Hydroxyapatite and hybrid gelatine/hydroxyapatite microspheres were obtained through a water in oil emulsion of a calcium phosphate cement (CPC). The setting reaction of the CPC, in this case the hydrolysis of ?-tricalcium phosphate, was responsible for the consolidation of the microspheres. After the setting reaction, the microspheres consisted of an entangled network of hydroxyapatite crystals, with a high porosity and pore sizes ranging between 0.5 and 5 ?m. The size of the microspheres was tailored by controlling the viscosity of the hydrophobic phase, the rotation speed, and the initial powder size of the CPC. The incorporation of gelatin increased the sphericity of the microspheres, as well as their size and size dispersion. To assess the feasibility of using the microspheres as cell microcarriers, Saos-2 cells were cultured on the microspheres. Fluorescent staining, SEM studies, and LDH quantification showed that the microspheres were able to sustain cell growth. Cell adhesion and proliferation was significantly improved in the hybrid gelatin/hydroxyapatite microspheres as compared to the hydroxyapatite ones. PMID:21290594

Perez, Roman A; Del Valle, Sergio; Altankov, George; Ginebra, Maria-Pau

2011-02-02

4

Hollow hydroxyapatite microspheres as a device for controlled delivery of proteins  

PubMed Central

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

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

2011-01-01

5

Biological evaluation of nano-hydroxyapatite-zirconia (HA-ZrO2) composites and strontium-hydroxyapatite (Sr-HA) for load-bearing applications.  

PubMed

The biological response of strontium (Sr) doped hydroxyapatite (HA) and hydroxyapatite-zirconia (HA-ZrO?) composites produced by employing sol-gel technology, minimal ZrO? loadings, and novel microwave-sintering regimes thereby retarding decomposition, is reported. In vitro evaluations indicate that all materials induce a favorable response from rat osteosarcoma cells. In vivo evaluations show osteoconductivity and biocompatibility for both the Sr-HA and HA-ZrO?. The materials did not cause any inflammatory response in bone. The Sr-HA displays better biocompatibility which may be due to the incorporation of Sr and the formation of a surface apatite layer. PMID:21926146

Brook, Ian; Freeman, Christine; Grubb, Sarah; Cummins, Niamh; Curran, Declan; Reidy, Colin; Hampshire, Stuart; Towler, Mark

2011-09-16

6

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

7

Effect of surface modified hydroxyapatite on the tensile property improvement of HA/PLA composite  

NASA Astrophysics Data System (ADS)

In this study, we modified the surface of hydroxyapatite (HA) particle by ring-opening polymerization of lactide (LA). The modified HA particles were characterized by IR and TGA. It was shown that LA could be graft-polymerized onto the surface of HA. A series of composites based on modified HA/PLA were further prepared and characterized. It indicated that the modified HA particles were well dispersed in PLA matrix than unmodified HA particles and the adhesion between HA particle and PLA matrix was improved. The modified HA/PLA composites showed good mechanical properties than that of unmodified HA/PLA.

Li, J.; Lu, X. L.; Zheng, Y. F.

2008-11-01

8

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

9

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

2013-04-01

10

Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical properties  

Microsoft Academic Search

Flame-spheroidized feedstock, with excellent known heat transfer and consistent melting capabilities, were used to produce hydroxyapatite (HA) coatings via plasma spraying. The characteristics and inherent mechanical properties of the coatings have been investigated and were found to have direct and impacting relationship with the feedstock characteristics, processing parameters as well as microstructural deformities. Processing parameters such as particle sizes (SHA:

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

2000-01-01

11

Radio frequency (RF) suspension plasma sprayed ultra-fine hydroxyapatite (HA)\\/zirconia composite powders  

Microsoft Academic Search

Ultra-fine hydroxyapatite (HA)\\/ZrO2 composite powders was synthesised by radio frequency (RF) induction suspension plasma spray. A wet suspension of HA\\/ZrO2 was employed as feedstock. The suspension was injected axially into the RF plasma to produce the nano-composite powders, which were subsequently accumulated in cyclone collectors. The particle size and morphology was resolved by using the Zeta potential nano-particle size analyser,

Rajendra Kumar; P. Cheang; K. A. Khor

2003-01-01

12

Process-phase-properties relationship in radio frequency (RF) plasma synthesized hydroxyapatite (HA)  

Microsoft Academic Search

Radio frequency suspension plasma spraying (RFSPS) was used to synthesize ultra-fine (20 nm–2 ?m) hydroxyapatite (HA)–Ca10(PO4)6(OH)2 and ZrO2–HA–Calcium Phosphate (CaP) nano-composite powders. The ultra-fine powders were consolidated using the spark plasma sintering (SPS) process and in-vitro investigation of the sintered compacts revealed bioactive behavior inherent in the original powder. The influence of various plasma processing parameters and HA suspension concentrations

K. A. Khor; Rajendra Kumar; P. Cheang

2004-01-01

13

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

PubMed

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

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

2013-04-03

14

Preparation and evaluation of a new radiopharmaceutical for radiosynovectomy, 111Ag-labelled hydroxyapatite (HA) particles.  

PubMed

Many radionuclides, namely, 166Ho, 90Y, 165Dy, 32P, 198Au, 186Re, etc. have been used for radio-synovectomy. Silver-111 (T 1/2 7.45 d) can be produced in a nuclear reactor and is a potential therapeutic radionuclide decaying by beta(-) emission (92% E beta max=1.037MeV and 8% by beta(-) decay associated with emission of gamma-rays (E gamma=245.4keV, I gamma=1.33%; E gamma=342.1keV, I gamma=6.7%)). Because of the production feasibility and favourable nuclear properties, 111Ag may find use as a suitable radionuclide for radio-synovectomy. Hydroxyapatite (HA), Ca10(PO4)6(OH)2 is one of the preferred particulates for this application. In this work, [111Ag]Ag-HA particulates were successfully prepared with high-labelling yield ( approximately 97%) at various pH values. The radiochemical purity of the [111Ag]Ag-HA particles was 99.9%. Stability studies for 7 days showed that the [111Ag]Ag-HA particles retained their stability. gamma camera images at 15 min, 24h and 5 d after injection of the particles into rabbits revealed the retention of the activity in the synovial joints of the knee, thereby indicating excellent in vivo stability of [111Ag]Ag-HA particles. Therefore, [111Ag]Ag-HA particles would be a potential therapeutic agent in the management of arthritis. PMID:17951062

Chattopadhyay, Sankha; Vimalnath, K V; Saha, Sujata; Korde, Aruna; Sarma, H D; Pal, Sujit; Das, Malay K

2007-09-19

15

Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical properties.  

PubMed

Flame-spheroidized feedstock, with excellent known heat transfer and consistent melting capabilities, were used to produce hydroxyapatite (HA) coatings via plasma spraying. The characteristics and inherent mechanical properties of the coatings have been investigated and were found to have direct and impacting relationship with the feedstock characteristics, processing parameters as well as microstructural deformities. Processing parameters such as particle sizes (SHA: 20-45, 45-75 and 75-125 microm) and spray distances (10, 12 and 14 cm) have been systematically varied in the present study. It was found that the increase of particle sizes and spray distances weakened the mechanical properties (microhardness, modulus, fracture toughness and bond strength) and structural stability of the coatings. The presence of inter- and intralamellar thermal microcracks, voids and porosities with limited true contact between lamellae were also found to degrade the mechanical characteristics of the coatings, especially in coatings produced from large-sized HA particles. An effort was made to correlate the effects of microstructural defects with the resultant mechanical properties and structural integrity of the plasma-sprayed hydroxyapatite (HA) coatings. The effects of different heat treatment temperatures (600, 800 and 900 degrees C) on the mechanical properties of the coatings were also studied. It was found that a heat treatment temperature of 800 degrees C does enhance the microhardness and elastic modulus of the coatings significantly (P < 0.05) whereas a further increment in heat treatment temperature to 900 degrees C did not show any discernable improvements (P > 0.1). The elastic response behaviour and fracture toughness of both the as-sprayed and heat-treated HA coatings using Knoop and Vickers indentations at different loadings have been investigated. Results have shown that the mechanical properties of the coatings have improved significantly despite increasing crack density after heat treatment in air. Coatings produced from the spheroidized feedstock of 20-45 microm (SHA 20-45 microm) sprayed at a stand-off distance of 10 cm were found to possess the most favourable mechanical properties. PMID:10811304

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

2000-06-01

16

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

17

Osteogenic Differentiation of Human Bone Marrow Stromal Cells in Hydroxyapatite-Loaded Microsphere-Based Scaffolds  

PubMed Central

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.

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

2012-01-01

18

Synthesis of Calcium Hydroxyapatite-Tricalcium Phosphate (HA-TCP) Composite Bioceramic Powders and Their Sintering Behavior  

Microsoft Academic Search

Composite (biphasic) mixtures of two of the most important inorganic phases of synthetic bone applications—namely, calcium hydroxyapatite (Ca10(PO4)6(OH)2 (HA)) and tri- calcium phosphate (Ca3(PO4)2 (TCP))—were prepared as submicrometer-sized, chemically homogeneous, and high- purity ceramic powders by using a novel, one-step chemical precipitation technique. Starting materials of calcium ni- trate tetrahydrate and diammonium hydrogen phosphate salts that were dissolved in appropriate

Nezahat Kivrak; A. Cuneyt Tas

1998-01-01

19

Selective laser sintering of porous tissue engineering scaffolds from poly(L: -lactide)/carbonated hydroxyapatite nanocomposite microspheres.  

PubMed

This study focuses on the use of bio-nanocomposite microspheres, consisting of carbonated hydroxyapatite (CHAp) nanospheres within a poly(L: -lactide) (PLLA) matrix, to produce tissue engineering (TE) scaffolds using a modified selective laser sintering (SLS) machine. PLLA microspheres and PLLA/CHAp nanocomposite microspheres were prepared by emulsion techniques. The resultant microspheres had a size range of 5-30 microm, suitable for the SLS process. Microstructural analyses revealed that the CHAp nanospheres were embedded throughout the PLLA microsphere, forming a nanocomposite structure. A custom-made miniature sintering platform was installed in a commercial Sinterstation((R)) 2000 SLS machine. This platform allowed the use of small quantities of biomaterials for TE scaffold production. The effects of laser power; scan spacing and part bed temperature were investigated and optimized. Finally, porous scaffolds were successfully fabricated from the PLLA microspheres and PLLA/CHAp nanocomposite microspheres. In particular, the PLLA/CHAp nanocomposite microspheres appeared to be promising for porous bone TE scaffold production using the SLS technique. PMID:17619975

Zhou, Wen You; Lee, Siu Hang; Wang, Min; Cheung, Wai Lam; Ip, Wing Yuk

2007-07-10

20

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

Microsoft Academic Search

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

Y Shikinami; M Okuno

1999-01-01

21

Hydroxyapatite (HA) coating appears to be of benefit for implant durability of tibial components in primary total knee arthroplasty  

PubMed Central

Background It is unclear whether there is a clinical benefit to adding hydroxyapatite (HA) coatings to total knee implants, especially with the tibial component, where failure of the implant more often occurs. A systematic review of the literature was undertaken to identify all prospective randomized trials for determining whether the overall clinical results (as a function of durability, function, and adverse events) favored HA-coated tibial components. Methods A comprehensive literature search was performed for the years 1990 to September 16, 2010. We restricted our search to randomized controlled trials involving participants receiving either an HA-coated tibia or other forms of tibial fixation. The primary outcome measures evaluated were durability, function, and acute adverse events. Results Data from 926 evaluable primary total knee implants in 14 studies were analyzed. Using an RSA definition for durability, HA-coated tibial components (porous or press-fit) without screw fixation were less likely to be unstable at 2 years than porous and cemented metal-backed tibial components (RR = 0.58, 95% CI: 0.34–0.98; p = 0.04, I2 = 39%, M-H random effects model). There was no significant difference in durability, as measured from revision and evaluated at 2 and 8–10 years, between groups. Also, functional status using different validated measures showed no significant difference at 2 and 5 years, no matter what measure was used. Lastly, there was no significant difference in adverse events. Limitations included small numbers of evaluable patients (? 50) in 7 of the 14 trials identified, and a lack of “hard” evidence of durability with need for replacement (i.e. frank failure, pain, or loss of functionality). Interpretation In patients > 65 years of age, an HA-coated tibial implant may provide better durability than other forms of tibial fixation. Larger trials should be undertaken comparing the long-term durability, function, and adverse events of HA-coated implants with those of other porous-coated tibial implants in younger, more active OA patients.

2011-01-01

22

An investigation of the chemical synthesis and high-temperature sintering behaviour of calcium hydroxyapatite (HA) and tricalcium phosphate (TCP) bioceramics  

Microsoft Academic Search

The experimental conditions for the synthesis of sub-micrometre,spherical particles of calcium hydroxyapatite[Ca10(PO4)6(OH)2] (HA) andtricalcium phosphate [Ca3(PO4)2] (TCP) areinvestigated through chemical coprecipitation from the aqueous solutions ofcalcium nitrate and di-ammonium hydrogen phosphate salts. The precipitationprocess employed was also found to be suitable for the production ofsub-micrometre HA\\/TCP composite powders in situ. The synthesized pureHA and TCP powders were found to be

A CUNEYT TAS; F KORKUSUZ; M TIMUCIN; N AKKAS

1997-01-01

23

Processing of bovine hydroxyapatite (HA) powders and synthesis of calcium phosphate silicate glass ceramics using DC thermal plasma torch  

Microsoft Academic Search

In the present work, hydroxyapatite (Ca10(PO4)6(OH)2) was prepared from bovine bones with calcination method (up to 850°C).The calcinated hydroxyapatite was powdered (30–40?m) using a mechanical grinder; the particles were highly irregular in shape with sharp edges, angular, rounded, circular, dentric, porous and fragmented morphologies. The irregular shaped calcinated hydroxyapatite was plasma processed to produce spherical powders for thermal spray coating

C. P. Yoganand; V. Selvarajan; Junshu Wu; Dongfeng Xue

2008-01-01

24

A prospective consecutive study of instrumented posterolateral lumbar fusion using synthetic hydroxyapatite (Bongros-HA) as a bone graft extender.  

PubMed

A prospective, single institution, clinical case-matched, radiographic study was undertaken. Thirty-two patients underwent posterior lumbar interbody fusion with cages containing laminectomized bone chips and posterolateral lumbar fusion with pedicle screws. Autogenous bone graft (3 mL) plus 3 mL of hydroxyapatite was placed in one side of a posterolateral gutter, and 6 mL of autogenous iliac bone graft was placed on the other side. Bony union, volumes of fusion mass, and bone absorption rates were postoperatively evaluated using simple radiographs and 3D-CT scans. Average postoperative Lenke scores at 3 and 6 months in the hydroxyapatite group were statistically higher than in the autograft group, but at 12 months no difference was found between the hydroxyapatite and autograft groups in terms of fusion rate. Complete fusion rates by 3D-CT were 86.7% in the hydroxyapatite group and 88.9% in the autograft group, which are not significantly different. Volumes of fusion mass and bone absorption rates at 12 months were 2.35 mL in the hydroxyapatite group and 1.31 mL in the autograft group. The mean fusion mass volume was greater in the hydroxyapatite group than in the autograft group. Lumbar posterolateral fusion using a mixture of hydroxyapatite artificial bone and autogenous bone graft showed good bony union similar to that shown with autogenous bone only. This study suggests that hydroxyapatite bone chips could be used usefully as a bone-graft extender in short-segment posterolateral spinal fusion. PMID:18615472

Lee, Jae Hyup; Hwang, Chang-Ju; Song, Byung-Wook; Koo, Ki-Hyung; Chang, Bong-Soon; Lee, Choon-Ki

2009-09-01

25

Fabrication of porous polycaprolactone/hydroxyapatite (PCL/HA) blend scaffolds using a 3D plotting system for bone tissue engineering.  

PubMed

For tissue engineering and regeneration, a porous scaffold with interconnected networks is needed to guide cell attachment and growth/ingrowth in three-dimensional (3D) structure. Using a rapid prototyping (RP) technique, we designed and fabricated 3D plotting system and three types of scaffolds: those from polycaprolactone (PCL), those from PCL and hydroxyapatite (HA), and those from PCL/HA and with a shifted pattern structure (PCL/HA/SP scaffold). Shifted pattern structure was fabricated to increase the cell attachment/adhesion. The PCL/HA/SP scaffold had a lower compressive modulus than PCL and PCL/HA scaffold. However, it has a better cell attachment than the scaffolds without a shifted pattern. MTT assay and alkaline phosphatase activity results for the PCL/HA/SP scaffolds were significantly enhanced compared to the results for the PCL and PCL/HA scaffolds. According to their degree of cell proliferation/differentiation, the scaffolds were in the following order: PCL/HA/SP > PCL/HA > PCL. These 3D scaffolds will be applicable for tissue engineering based on unique plotting system. PMID:21170553

Park, Su A; Lee, Su Hee; Kim, Wan Doo

2010-12-18

26

In vitro degradation and cytocompatibility of dicalcium phosphate dihydrate cements prepared using the monocalcium phosphate monohydrate/hydroxyapatite system reveals rapid conversion to HA as a key mechanism.  

PubMed

We previously showed that dicalcium phosphate dihydrate (DCPD) cements can be prepared using monocalcium phosphate monohydrate (MCPM) and hydroxyapatite (HA). In this study, we have characterized the degradation properties and biocompatibility of these novel cements. To study the degradation properties, cements were prepared using MCPM:HA molar ratios of 4:1, 2:1, 2:3, and 2:5. Degradation was evaluated in vitro by static soaking in PBS, and changes in pH, mass, compressive strength, and composition were monitored. Conversion of DCPD to HA was noted in the 4:1 group, which initially consisted of pure DCPD. However, the 2:1 group, which initially consisted of DCPD and an intermediate amount of unreacted HA, underwent rapid conversion to HA associated with significantly greater pH drop and mass loss as well as a complete loss of mechanical integrity. On the basis of these results, we directly compared the cytocompatibility of 2:1 MCPM:HA cements to DCPD cements prepared with an equivalent percent molar excess of ?-tricalcium phosphate (?-TCP) using an in vitro cell viability assay. Viability of cells co-cultured with 2:1 MCPM:HA cements was significantly reduced after just 48 h, while viability of cells cultured with the ?-TCP-based cements was no different from control cells. In conclusion, this study demonstrates that conversion to HA plays an important role in the degradation of DCPD cements prepared with the MCPM/HA system, affecting both physical properties and cytocompatibility. These results could have important clinical implications for MCPM/HA cements. PMID:22323239

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

2012-02-10

27

Enhancement of Cell-Based Therapeutic Angiogenesis Using a Novel Type of Injectable Scaffolds of Hydroxyapatite-Polymer Nanocomposite Microspheres  

PubMed Central

Background Clinical trials demonstrate the effectiveness of cell-based therapeutic angiogenesis in patients with severe ischemic diseases; however, their success remains limited. Maintaining transplanted cells in place are expected to augment the cell-based therapeutic angiogenesis. We have reported that nano-hydroxyapatite (HAp) coating on medical devices shows marked cell adhesiveness. Using this nanotechnology, HAp-coated poly(l-lactic acid) (PLLA) microspheres, named nano-scaffold (NS), were generated as a non-biological, biodegradable and injectable cell scaffold. We investigate the effectiveness of NS on cell-based therapeutic angiogenesis. Methods and Results Bone marrow mononuclear cells (BMNC) and NS or control PLLA microspheres (LA) were intramuscularly co-implanted into mice ischemic hindlimbs. When BMNC derived from enhanced green fluorescent protein (EGFP)-transgenic mice were injected into ischemic muscle, the muscle GFP level in NS+BMNC group was approximate fivefold higher than that in BMNC or LA+BMNC groups seven days after operation. Kaplan-Meier analysis demonstrated that NS+BMNC markedly prevented hindlimb necrosis (P<0.05 vs. BMNC or LA+BMNC). NS+BMNC revealed much higher induction of angiogenesis in ischemic tissues and collateral blood flow confirmed by three-dimensional computed tomography angiography than those of BMNC or LA+BMNC groups. NS-enhanced therapeutic angiogenesis and arteriogenesis showed good correlations with increased intramuscular levels of vascular endothelial growth factor and fibroblast growth factor-2. NS co-implantation also prevented apoptotic cell death of transplanted cells, resulting in prolonged cell retention. Conclusion A novel and feasible injectable cell scaffold potentiates cell-based therapeutic angiogenesis, which could be extremely useful for the treatment of severe ischemic disorders.

Koyama, Hidenori; Okada, Masahiro; Tanaka, Shinji; Shoji, Tetsuo; Emoto, Masanori; Furuzono, Tsutomu; Nishizawa, Yoshiki; Inaba, Masaaki

2012-01-01

28

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

PubMed

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

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

2013-07-08

29

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

30

The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/poly l-lactide (F-u-HA/PLLA).  

PubMed

Here we document the complete process of bioresorption and bone replacement of rods made of forged composites of unsintered hydroxyapatite particles/poly l-lactide (F-u-HA/PLLA) implanted in the femoral medullary cavities of rabbits. Bioresorption, osteoconductive bioactivity and bone replacement were compared in three implantation sites. In the first site, the end of the rod was located near the endosteum in the proximal medullary cavity. In the second, the rod was located at the centre of the bone marrow space without contacting the endosteum. In the third, the rod was in direct contact with cancellous bone within the distal femoral condyle. Micro-computerised tomography, scanning electron microscopy and photomicrographs of stained sections were used to document the complete process of bioresorption and bone replacement. At the first implantation site, the rod was completely resorbed and unbound u-HA particles were detected in and around the endosteum 5-6 years after implantation. At the second site, the rod showed significant shrinkage 4-5 years after implantation due to the release of almost all the PLLA, although a contracted cylindrical structure containing a few u-HA persisted even after approximately 6 years. At the third site, u-HA particles were almost completely replaced with bone after 5-6 years. Conversely, PLLA-only rods showed little bone conduction, and small amounts of degraded PLLA debris and intervening some tissue persisted even after long periods. Namely, the u-HA/PLLA composites were replaced with bone in the distal femoral condyle, where they were in direct contact with the bone and new bone formation was anatomically necessary. By contrast, composite rods were resorbed without replacement in the proximal medullary cavity, in which new bone growth was not required. We therefore conclude that the F-u-HA30/40 composites containing 30 wt%/40 wt% u-HA particles are clinically effective for use in high-strength bioactive, bioresorbable bone-fixation devices with the capacity for total bone replacement. PMID:15860210

Shikinami, Yasuo; Matsusue, Yoshitaka; Nakamura, Takashi

2005-09-01

31

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

PubMed

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

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

2010-10-23

32

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

33

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

PubMed

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

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

2013-03-04

34

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

35

Hydroxyapatite and Hydroxyapatite-Based Ceramics  

Microsoft Academic Search

Data are summarized on the synthesis of hydroxyapatite (HA) by wet-chemical processes, solid-state reactions, and hydrothermal treatment. The conditions for HA preparation via precipitation from solutions of calcium chloride, dibasic ammonium phosphate, and aqueous ammonia are discussed at length. Detailed analysis of the fabrication and properties of calcium-phosphate-based ceramics is presented. The techniques for producing dense and porous HA ceramics

V. P. Orlovskii; V. S. Komlev; S. M. Barinov

2002-01-01

36

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

2007-06-28

37

Production and characterization of HA and SiHA coatings.  

PubMed

Plasma sprayed hydroxyapatite (HA) coatings on metallic prostheses have been used clinically in dentistry and orthopedics since the mid 1980s. The coating properties are dependent on the spraying parameters. Since silicon-substituted hydroxyapatite (SiHA) has been shown to offer improved bioactivity over phase pure HA, SiHA coatings have the potential for enhanced performance in clinical application. In this study, phase pure HA and 0.8 wt% SiHA powders were synthesized with similar particle size distribution and morphology. The powders were plasma sprayed onto Ti-6Al-4V substrates at 37 kW and 40 kW plasma gun input power respectively. Four kinds of samples were prepared, HAC 37, HAC 40, SiHAC 37 and SiHAC 40. Materials characterization showed that the coatings were of relatively high phase purity. In vitro cell culture demonstrated that human osteoblast cells grew well on all samples, with the highest cell growth observed on SiHA coatings produced under the lower plasma gun input power. PMID:19672562

Tang, Qian; Brooks, Roger; Rushton, Neil; Best, Serena

2009-08-12

38

Yttria stabilized zirconia reinforced hydroxyapatite coatings  

Microsoft Academic Search

The low bonding strength between the coating layer and the substrate of plasma sprayed hydroxyapatite (HA) coatings is the weakness in its application as a bio-medical prosthesis. In this study, 30 wt.% of yttria (8 wt.%) stabilized zirconia (YSZ) has been used to reinforce the hydroxyapatite coatings and to improve the bond strength of the HA coatings. Fine YSZ coated

Lei Fu; Khiam Aik Khor; Joo Peng Lim

2000-01-01

39

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

40

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

41

Reaction of sodium calcium borate glasses to form hydroxyapatite.  

PubMed

This study investigated the transformation of two sodium calcium borate glasses to hydroxyapatite (HA). The chemical reaction was between either 1CaO . 2Na(2)O . 6B(2)O(3) or 2CaO . 2Na(2)O . 6B(2)O(3) glass and a 0.25 M phosphate (K(2)HPO(4)) solution at 37, 75 and 200 degrees C. Glass samples in the form of irregular particles (125-180 microm) and microspheres (45-90 and 125-180 microm) were used in order to understand the reaction mechanism. The effect of glass composition (calcium content) on the weight loss rate and reaction temperature on crystal size, crystallinity and grain shape of the reaction products were studied. Carbonated HA was made by dissolving an appropriate amount of carbonate (K(2)CO(3)) in the 0.25 M phosphate solution. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the reaction products. The results show that sodium calcium borate glasses can be transformed to HA by reacting with a phosphate solution. It is essentially a process of dissolution of glass and precipitation of HA. The transformation begins from an amorphous state to calcium-deficient HA without changing the size and shape of the original glass sample. Glass with a lower calcium content (1CaO . 2Na(2)O . 6B(2)O(3)), or reacted at an elevated temperature (75 degrees C), has a higher reaction rate. The HA crystal size increases and grain shape changes from spheroidal to cylindrical as temperature increases from 37 to 200 degrees C. Increase in carbonate concentration can also decrease the crystal size and yield a more needle-like grain shape. PMID:17486301

Han, Xue; Day, Delbert E

2007-05-08

42

Synthesis and characterization of nano-HA\\/PA66 composites  

Microsoft Academic Search

Based on the bioactivity and biocompatibility of hydroxyapatite (HA) and the excellent mechanical performance of polyamide 66 (PA66), a composite of nanograde HA with PA66 was designed and fabricated to mimic the structure of biological bone which exhibits a composite of nanograde apatite crystals and natural polymer. The HA\\/PA66 composite combines the bioactivity of HA and the mechanical property of

Mei Huang; Jianqing Feng; Jianxin Wang; Xingdong Zhang; Yubao Li; Yonggang Yan

2003-01-01

43

Thick hydroxyapatite coatings by electrophoretic deposition  

Microsoft Academic Search

Submicron hydroxyapatite (HA) powders prepared by thermal plasma spray method were electrophoretically deposited on carbon rod by repeated depositions at room temperature. The thickness of green coating was adjusted by deposition time and the number of depositions. After sintering, a uniform HA ceramic tube was obtained. A range of sintering temperature from 1150 to 1300 °C was studied. From the

Cong Wang; J Ma; Wen Cheng; Ruifang Zhang

2002-01-01

44

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

45

Nutrient-substituted hydroxyapatites: synthesis and characterization.  

PubMed

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. PMID:11543409

Golden, D C; Ming, D W

46

Processing and mechanical properties of HA\\/UHMWPE nanocomposites  

Microsoft Academic Search

A hydroxyapatite (HA) particulate reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite was fabricated by compounding HA and UHMWPE mixtures in paraffin oil using twin-screw extrusion and then compression molding. Scanning electron microscope images revealed that HA aggregates were broken down to nano-sized particles and homogeneously dispersed in UHMWPE by the combined processes of twin-screw extrusion and UHMWPE swelling treatment. Transmission

Liming Fang; Yang Leng; Ping Gao

2006-01-01

47

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

48

Study of two hydroxyapatite\\/poly(alkoxysilane) implant coatings  

Microsoft Academic Search

Bioactive hydroxyapatite coatings onto bioinert metallic implants have recently received considerable attention. This work presents a new low-temperature bi-layer hydroxyapatite (HA) coating. First, a thin pre-coating was made with polyalkoxysilanes to promote the adhesion of hydroxyapatite\\/polyalkoxysilanes composite second layer. In order to optimize the coating cohesion, various parameters were studied such as the metallic support roughness, the nature of alkoxysilanes

C. Damia; S. Sarda; E. Deydier; P. Sharrock

2006-01-01

49

Ion adsorption behaviour of hydroxyapatite with different crystallinities  

Microsoft Academic Search

This study aimed to correlate crystallinity of hydroxyapatite (HA) with the ion adsorption behaviour of the material. Hydroxyapatite powders of various crystallinities (Xc) and specific surface area (SSA) were prepared by precipitation following heat treatment. Adsorption experiments were carried out by using (i) multi-component ion solutions containing a broad range of light and heavy ions to study competitive adsorption and

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

2009-01-01

50

Structural changes of thermally sprayed hydroxyapatite investigated by Rietveld analysis  

Microsoft Academic Search

Hydroxyapatite (HA) coatings were prepared by three thermal spraying methods: flame spraying, high velocity oxygen fuel spraying and plasma spraying. The HA was then examined by Rietveld analysis using the General Structure Analysis Software package (GSAS) and the results compared with those for the precursor powder. A comparison between HA before and after spraying showed that all three spraying methods

J. C. Knowles; K. Gross; C. C. Berndt; W. Bonfield

1996-01-01

51

Production and evaluation of hydroxyapatite reinforced polysulfone for tissue replacement  

Microsoft Academic Search

A variety of bioactive composites have been developed for tissue replacement over the last two decades. In this investigation, a new material consisting of hydroxyapatite (HA) and polysulfone (PSU) was produced and evaluated for potential medical applications. The HA\\/PSU composite containing up to 20 vol % of HA was studied at the initial stage. It was manufactured via a standardized

M. Wang; C. Y. Yue; B. Chua

2001-01-01

52

Calcining influence on the powder properties of hydroxyapatite  

Microsoft Academic Search

The effect of different calcination temperatures on the powder characteristics and the sintered density of synthetic hydroxyapatite (HA) powders, produced using two different processing routes, was examined. Powders were produced by either drying, milling and sieving an as-precipitated HA or by spray-drying a slurry of precipitated HA. Calcining the two powders at temperatures between 400 and 1000 °C did not

N. Patel; I. R. Gibson; S. Ke; S. M. Best; W. Bonfield

2001-01-01

53

Carbon nanotube-hydroxyapatite nanocomposite for DNA complexation  

Microsoft Academic Search

This communication reports that a plasmid DNA molecule could spontaneously interact with hydroxyapatite (HA) functionalized multi-walled carbon nanotubes (MWNTs-HA) in water-solute environment. Gel electrophoresis, UV absorption, FT-IR, and Raman spectra were used to characterize MWNTs-HA\\/DNA complexes. AFM and TEM images revealed that DNA induces the de-aggregation of MWNTs-HA. Our preliminary study suggests that the plasmid DNA significantly interacted with MWNTs-HA,

Shanta Raj Bhattarai; Santosh Aryal; Narayan Bhattarai; Pyong Han Hwang; Ho Keun Yi; Hak Yong Kim

2008-01-01

54

Growth of hydroxyapatite in a biocompatible mesoporous ordered silica  

Microsoft Academic Search

A novel biomaterial (HA-SBA-15) has been developed based on the growth of calcium phosphate hydroxyapatite (HA) nanoparticles within an organized silica structure (SBA-15). Characterization of the material was carried out using a combination of X-ray diffraction, X-ray fluorescence, transmission electron microscopy, N2 adsorption–desorption isotherms and nuclear magnetic resonance. Transmission electron microscopy observations and N2 porosimetry revealed the crystallization of hydroxyapatite

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

2006-01-01

55

Characterization of thermal sprayed hydroxyapatite powders and coatings  

Microsoft Academic Search

Calcium phosphate materials such as hydroxyapatite (HA) have biocompatible properties that can promote osteogenesis or new\\u000a bone formation. Thermal spraying is an economical and effective process for coating the hydroxyapatite onto metal. It has\\u000a been reported that plasma spraying changes the degree of crystallinity as well as the phase composition of the HA. This article\\u000a reports the preparation and characterization

K. A. Khor; P. Cheang

1994-01-01

56

Nonstoichiometric hydroxyapatite granules for orthopaedic applications  

Microsoft Academic Search

A new method for the preparation of nonstoichiometric hydroxyapatite (HA) “dense” and porous granules, round in form and up to 8 mm in sizes designed for application in orthopaedic surgery has been developed. The “dense” granules' porosity was up to 32% and they only contained micropores. They differed from that kind of granules by increased values of compression strength (up

Z. Zyman; V. Glushko; V. Filippenko; V. Radchenko; V. Mezentsev

2004-01-01

57

Fabrication and characterization of needle-like nano-HA and HA/MWNT composites.  

PubMed

Hydroxyapatite (HA) ceramic has been used in tissue engineering and orthopedics for its good biocompatibility and osteoconductivity. However, its clinical applications are usually limited by the low strength and brittleness. The objective of this research was to develop a new kind of HA composites in which multi-wall carbon nanotubes (MWNTs) were introduced to the HA ceramic matrix to improve the mechanical properties of the resulting composites. A simple chemical wet method was applied to synthesize the HA ceramic particles with the aid of surfactant and ultrasonication technique at normal atmospheric pressure. The morphology and microstructure of the synthesized HA were characterized by XRD and TEM as a function of treatment time. The results showed that the synthesized HA particles are needle-like with a length of 80-160 nm along the (211) direction and an aspect ratio of 5-15. MWNTs were treated with a mixture of nitric acid and sulfuric acid. The HA/MWNT composites were prepared by solution blending. The composites were sintered using a hot-press method. The mechanical properties of the HA/MWNT composites with different volume percentages of MWNTs were examined. The fracture toughness and flexural strength were improved by 50% and 28% separately when the volume percentage of MWNTs reached 7%. PMID:17577639

Meng, Y H; Tang, Chak Yin; Tsui, Chi Pong; Chen, Da Zhu

2007-06-19

58

Dissolution of human teeth-derived hydroxyapatite.  

PubMed

We have been interested in human teeth which consist of hydroxyapatite (HA), but do not degrade for a long time. In order to overcome dissolution and mechanical degradation of man-made HA, biologically derived hydroxyapatite (BHA) ceramics were prepared from human teeth and their dissolving behavior was investigated in distilled water for 3-14 days and compared with an artificial HA made of synthetic HA powder. BHA ceramics were prepared by calcining freshly extracted human teeth at 900 degrees C and followed by sintering at 1200 degrees C for 2 h. All detectable peaks in the artificial HA are identical to HA lattice planes, whereas BHA consisted of a mixture of HA and beta-tricalcium phosphate (TCP). Although the artificial HA was expected to be stable in water, the surface dissolution initiated at grain boundaries followed by generated many separated grains and their associated pores. On the other hand, BHA showed that definite grains considered as beta-TCP were predominantly dissolved and the grains were separated from the matrix leaving pores. In the mean time, the rest region, mainly consisting of HA, did not show any evidence of dissolution. It indicates that BHA showed rather stable grain boundaries and lack of excessive dissolution in liquid environment. PMID:17943445

Seo, Dong Seok; Lee, Jong Kook

2007-10-18

59

Characterization of sintered titanium\\/hydroxyapatite biocomposite using FTIR spectroscopy  

Microsoft Academic Search

Fourier transform infrared (FTIR) spectroscopy was employed to characterize the phase changes of hydroxyapatite (Ca10(PO4)6(OH)2, HA) in a titanium\\/HA biocomposite during sintering. The effects of sintering temperature and the presence of Ti on the decomposition\\u000a of HA were examined. It was observed that pure HA was stable in argon atmosphere at temperatures up to 1,200°C, although the\\u000a dehydroxylation of pure

Hezhou Ye; Xing Yang Liu; Hanping Hong

2009-01-01

60

Development of nano-hydroxyapatite coating by electrohydrodynamic atomization spraying  

Microsoft Academic Search

Electrohydrodynamic atomisation (EHDA) spraying of a hydroxyapatite (HA) suspension consisting of nano-particles (nHA) has\\u000a been used to produce a HA coating comprising of nanostructured surface topography. In EHDA the suspension is jetted from a\\u000a needle under an electric field. Obtaining the stable cone-jet mode of EHDA is critical to improve the quality and optimise\\u000a the morphology of HA coatings, therefore

Xiang Li; Jie Huang; Mohan Edirisinghe

2008-01-01

61

Formation of Hydroxyapatite in Cement Systems: Effects of Phosphate  

Microsoft Academic Search

The rate of hydroxyapatite (HA) formation in several calcium phosphate cement (CPC) systems was promoted when a phosphate solution instead of water was used as the cement liquid. The accelerated HA formation reduced the hardening time (HT) of the cements. In the cement system consisting of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA), and distilled water, the presence of small

Laurence C. Chow; Milenko Markovic; Shozo Takagi

1999-01-01

62

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

63

Hydroxyapatite as a concentrating probe for phosphoproteomic analyses  

Microsoft Academic Search

A novel method for the selective enrichment of casein phosphoproteins\\/phosphopeptides (CPP) from complex mixtures is reported herein. This method employs ceramic hydroxyapatite (HA) as a solid-phase adsorbent to efficiently capture phosphoproteins and CPP from complex media. Casein was chosen as the model phosphoprotein to test the protocol. CPP immobilized on HA microgranules formed a complex that was included in the

Gabriella Pinto; Simonetta Caira; Marina Cuollo; Sergio Lilla; Olga Fierro; Francesco Addeo

2010-01-01

64

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

65

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

66

Hydroxyapatite\\/titania composite bioactivity coating processed by sol–gel method  

Microsoft Academic Search

Hydroxyapatite\\/titania composite material was coated onto a titanium (pure Ti) substrate by sol–gel method. The hydroxyapatite (HA) and titania (TiO2) sol were made from precursor and mixed together. The insertion of TiO2 enhanced the chemical affinity and the physical consistency between HA and Ti substrate. The HA\\/TiO2 composite coating adhered tightly to the Ti substrate. Owing to the insertion of

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

2008-01-01

67

Polymer-assisted synthesis of hydroxyapatite nanoparticle  

Microsoft Academic Search

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) nanoparticles were synthesized using calcining calcium dihydrogenphosphate (Ca(H2PO4)2·H2O), calcium hydroxide (Ca(OH)2), and polyethylene glycol (PEG) at 900 °C in an oxygen atmosphere. This one-step process yields HA nanoparticles with similar particle sizes (e.g., 50–80 nm) that are well-crystallized and non-aggregated. PEG is an important factor in controlling the particle size, crystal phase, and degree of aggregation in these HA

Yao-Hsuan Tseng; Chien-Sheng Kuo; Yuan-Yao Li; Chin-Pao Huang

2009-01-01

68

Synthesis and characterization of nano-HA/PA66 composites.  

PubMed

Based on the bioactivity and biocompatibility of hydroxyapatite (HA) and the excellent mechanical performance of polyamide 66 (PA66), a composite of nanograde HA with PA66 was designed and fabricated to mimic the structure of biological bone which exhibits a composite of nanograde apatite crystals and natural polymer. The HA/PA66 composite combines the bioactivity of HA and the mechanical property of PA66. This study focused on the preparation method of HA/PA66 composite and the influence of HA crystals on the characterization of the composite. HA slurry was used directly to prepare HA/PA66 composite by a solution method, in which HA is able to form hydrogen bond, i.e. chemical bonding with PA66. The nano-HA needle-like crystals treated by hydrothermal method are better in the particle size distribution and the particle dispersion. The morphology, crystal structure and crystallinity as well as crystal size of these needle-like crystals are similar to bone apatite. The nano-HA needle-like crystals dispersed uniformly in PA66 matrix with reinforcement effect and can prevent the micro-crackle spreading into cleft and fracture during the deformation process. The mechanical testing shows that the nano-HA/PA66 composite has a good mechanical property, and may be a promising bone replacement material. PMID:15348430

Huang, Mei; Feng, Jianqing; Wang, Jianxin; Zhang, Xingdong; Li, Yubao; Yan, Yonggang

2003-07-01

69

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

PubMed

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

Cheng, Kui; Zhang, Sam; Weng, Wenjian

2007-06-09

70

Surface modification of magnetron-sputtered hydroxyapatite thin films via silicon substitution for orthopaedic and dental applications  

Microsoft Academic Search

There have been a significant advances made in the field of bioceramics, particularly hydroxyapatite (HA) during the past 10years. Emphasis has now shifted towards designing HA with enhanced bioactivity for bone tissue repair. The aim of this study was to assess whether surface wettability can be correlated with cellular interactions with silicon-substituted hydroxyapatite (SiHA)-coated titanium (Ti) substrates. SiHA thin coatings

Eng San Thian; Jie Huang; Zoe H. Barber; Serena M. Best; William Bonfield

2011-01-01

71

The fully hydroxyapatite-coated total hip implant  

Microsoft Academic Search

The clinical and roentgenographic results of 54 fully hydroxyapatite (HA)-coated primary total hip arthroplasties in 45 patients was studied. Both the femoral and the acetabular components had a 200-?m coating of hydroxyapatite. The mean age of the patients was 54.8 years. Twenty-three patients were between 45 and 60 years of age. There were 24 men and 21 women. Nine patients

Ravishankar Vedantam; C. Ruddlesdin

1996-01-01

72

Nanocrystalline hydroxyapatite bio-mineral for the treatment of strontium from aqueous solutions  

Microsoft Academic Search

Hydroxyapatites were analysed using electron microscopy, X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis. Examination\\u000a of a bacterially produced hydroxyapatite (Bio-HA) by scanning electron microscopy showed agglomerated nano-sized particles;\\u000a XRD analysis confirmed that the Bio-HA was hydroxyapatite, with an organic matter content of 7.6%; XRF analysis gave a Ca\\/P\\u000a ratio of 1.55, also indicative of HA. The size of the

Stephanie Handley-Sidhu; Joanna C. Renshaw; Ping Yong; Robert Kerley; Lynne E. Macaskie

2011-01-01

73

Preparation of bioactive porous HA/PCL composite scaffolds  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

74

Evidence of chemical bonding to hydroxyapatite by phosphoric acid esters  

Microsoft Academic Search

Phosphoric acid esters (PAEs) have been used as a self-etching primer for composite-to-enamel bonding in adhesive dentistry. However, the chemical mechanism of their interactions with hydroxyapatite (HA) is not clear. In the present study, HA particles were mixed with Resulcin AquaPrime (Merz Co.) priming agent that contains a mixture of PAEs, and dried. The primer, HA and the mixture of

Baiping Fu; Xuemei Sun; Weixin Qian; Yanqing Shen; Ranran Chen; Matthias Hannig

2005-01-01

75

Biomimetic patterning of polymer hydrogels with hydroxyapatite nanoparticles  

Microsoft Academic Search

We report here an in situ process to produce nano-composite polymer hydrogels having surfaces patterned with hydroxyapatite (HA) nanoparticles (100 nm). Poly (vinyl alcohol) (PVA) has been used as a hydrogel forming medium. A three step process, comprising precipitation of HA nanoparticles in presence of PVA molecules and freeze thawing of obtained PVA-HA emulsion, followed by critical point drying, has been

Arvind Sinha; Avijit Guha

2009-01-01

76

Comparative study of hydroxyapatite from eggshells and synthetic hydroxyapatite for bone regeneration.  

PubMed

OBJECTIVES: The objective of this study was to evaluate the physical properties of synthetic hydroxyapatite (sHA) and hydroxyapatite from eggshells (eHA) by Fourier-transform infrared (FT-IR) and x-ray diffraction (XRD) and to compare the regenerative ability of the bone using sHA and eHA in a rabbit calvarial defect model. STUDY DESIGN: FT-IR and XRD were used to compare the physical properties of sHA and eHA. sHA was purchased from Sigma, and eHA was kindly donated from the Hungarian academy of science. Sixteen New Zealand white rabbits were used for the animal study. After the formation of a bilateral parietal bony defect (diameter 8.0 mm), either sHA or eHA was grafted into the defect. The defect in the control was left unfilled. Bone regeneration was evaluated by histomorphometry at 4 and 8 weeks after the operation. RESULTS: The peak broadening of the XRD experiments were in agreement with scanning electron microscope observation; the sHA had a smaller granule size than the eHA. The eHA had impurities phases of CaO (International Center for Diffraction Data (ICDD) 075-0264) and Ca(OH)(2) (ICDD 072-0156). Total new bone was 17.11 ± 10.24% in the control group, 28.81 ± 12.63% in sHA group, and 25.68 ± 10.89% in eHA group at 4 weeks after the operation. The difference was not statistically significant (P > .05). Total new bone at 8 weeks after the operation was 27.50 ± 10.89% in the control group, 38.62 ± 17.42% in sHA group, and 41.99 ± 8.44% in the eHA group. When comparing the sHA group to the control group, the difference was not statistically significant (P > .05). However, the eHA group was significantly different from the control group (P = .038). When comparing the eHA group to the sHA group, the difference was not statistically significant (P > .05). CONCLUSIONS: Both types of HA showed higher bone formation than the unfilled control. However, eHA had significantly higher bone formation than the unfilled control at 8 weeks after operation. PMID:21696984

Lee, Sang-Woon; Kim, Seong-Gon; Balázsi, Csaba; Chae, Weon-Sik; Lee, Hee-Ok

2011-06-20

77

The nanocomposite scaffold of poly(lactide-co-glycolide) and hydroxyapatite surface-grafted with l-lactic acid oligomer for bone repair  

Microsoft Academic Search

Nanohydroxyapatite (op-HA) surface-modified with l-lactic acid oligomer (LAc oligomer) was prepared by LAc oligomer grafted onto the hydroxyapatite (HA) surface. The nanocomposite of op-HA\\/PLGA with different op-HA contents of 5, 10, 20 and 40wt.% in the composite was fabricated into three-dimensional scaffolds by the melt-molding and particulate leaching methods. PLGA and the nanocomposite of HA\\/PLGA with 10wt.% of ungrafted hydroxyapatite

Yang Cui; Yi Liu; Yi Cui; Xiabin Jing; Peibiao Zhang; Xuesi Chen

2009-01-01

78

Porous bioactive scaffold of aliphatic polyurethane and hydroxyapatite for tissue regeneration  

Microsoft Academic Search

In this study, a new hydroxyapatite (HA)\\/polyurethane (PU) composite porous scaffold was developed by in situ polymerization. Aliphatic isophorone diisocyanate as a nontoxic and safe agent was adopted to produce the rigid segment in polyurethane polymerization. Hydroxyapatite powder was compounded in a PU polymer matrix during the polymeric process. The macrostructure and morphology as well as mechanical strength of the

Li Wang; Yubao Li; Yi Zuo; Li Zhang; Qin Zou; Lin Cheng; Hong Jiang

2009-01-01

79

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

80

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

81

Survival of hydroxyapatite-coated implants: A meta-analytic review  

Microsoft Academic Search

Purpose: Some reports show a benefit of coating dental implants with hydroxyapatite (HA), and others assert that resorption of the HA coating compromises long-term implant survival. This study examined this controversy by systematically reviewing all the current literature that reports the outcomes of HA-coated implants in human clinical trials. Materials and Methods: A systematic Medline computer search of the English

Jessica J Lee; Leyla Rouhfar; O. Ross Beirne

2000-01-01

82

In vitro and in vivo tests of hydrothermally synthesised hydroxyapatite coating  

Microsoft Academic Search

High pure and crystalline Hydroxyapatite (HA) coatings on titanium alloy were prepared by hydrothermal synthesis (HS) of plasma-sprayed (PS) precursors from brushite powders (HS-HA). In vitro and in vivo tests were done to evaluate its biological property. The HS-HA coating was compared with the current PS-HA coating. Cultures of the primary osteoblasts on these two HA coatings showed similar cell

Yumei Zhang; Tao Fu; Yong Han; Qintao Wang; Yimin Zhao; Kewei Xu

2002-01-01

83

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

84

Bone ingrowth on a smooth-surfaced hydroxyapatite-coated acetabular cup  

Microsoft Academic Search

We studied 29 retrieved smooth-surfaced hydroxyapatite (HA)-coated acetabular cups that had been in situ for an average of 54.9 months. The outer surface of all cups carried two circular grooves dividing the smooth surface. The extent of bony in-growth and hydroxyapatite absorption was calculated using a computer imaging system (analySIS-pro 3.0, Soft Imaging System GmbH, Germany). Absorption of HA was

Y. Y. Chung; H. D. Kim; K. S. Kim

2002-01-01

85

Thermal and crystallization studies of nano-hydroxyapatite reinforced polyamide 66 biocomposites  

Microsoft Academic Search

The thermal and crystalline behaviour of nano-hydroxyapatite (n-HA) reinforced polyamide 66 (PA66) biocomposites was studied by thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal properties of PA66 and n-HA\\/PA66 composites were analysed by TG. The effect of hydroxyapatite on the melting and crystallization of PA66 was evaluated by DSC. DSC measurements exhibited an increase in the crystallization temperature, however,

Xiang Zhang; Yubao Li; Guoyu Lv; Yi Zuo; Yuanhua Mu

2006-01-01

86

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

87

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

88

[A new hydroxyapatite cement for craniofacial surgery].  

PubMed

A new stoechiometric mixture of 27% dicalcium-phosphate (DCPA) and 73% tetra-calcium-phosphate (TTCP) can be prepared with water intraoperatively to a paste that subsequently sets to a structurally stabile implant composed of hydroxyapatite (HA). Primary setting time is about 20 min; pH during setting ranges from 6.5 to 8.5. There is no relevant curing heat or expansion or contraction. Compressive strength is about 50 MPa, tensile strength about 8 MPa. Over a period of about 4 h in physiological milieu, the cement converts to hydroxyapatite. This product is no longer redissolvable in normal body fluid. This cement can be used for non-load-bearing applications especially in craniofacial bone surgery. Cranial defects due to tumour or trauma as well as deficits in the facial skeleton may be reconstructed using this new biomaterial. In nine of ten patients we used the hydroxyapatite cement successfully for reconstructions in the craniofacial area. Fluid control of the operation field and implant site is extremely important and sometimes difficult to achieve. Further applications could be all non-load-bearing augmentations such as filling of blocked paranasal sinuses, of dentoalveolar cysts and defects following dental apectomy or fixation of implanted hearing-aid electrodes. The perspectives for the hydroxyapatite cement include its application as a carrier for osteogenic protein preparations, especially because of its isothermic reaction and intrinsic osteoconductive characteristics. PMID:23526011

Pistner, H; Reuther, J; Reinhart, E; Kübler, N; Priessnitz, B

1998-05-01

89

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

SciTech Connect

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

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

2005-06-01

90

Hydroxyapatite ceramics with selected sintering additives.  

PubMed

Several sintering additives for hydroxyapatite (HA) have been tested in order to enhance its sinterability without decomposing the HA and/or decreasing bioactivity and biocompatibility, additionally providing a weak interface for HA ceramics. The ion species of sintering additives were selected from those in the mineral constituents of hard tissues and bioactive glasses. After investigation of phase diagrams in the CaO-P2O5-additive systems, and analysis of physiochemical properties of the additives, several sintering aids for HA have been chosen. Subsequently, densification, phase composition, grain growth and fracture behaviour of HA containing 5 wt% of each additive, sintered at 1000-1100 degrees C, have been studied. H3BO3, CaCl2, KCl, KH2PO4, (KPO3)n and Na2Si2O5 did not enhance densification of HA. K2CO2, Na2CO3, KF and sodium phosphates improved the densification significantly. Expect for KCl and some sodium phosphates, all the additives caused formation of large quantities of undesired beta-tricalcium phosphate or CaO; therefore, they are not appropriate for HA. In the case of sodium phosphate additives, it was possible to avoid formation of CaO or beta-tricalcium phosphate by control of the additive quantity and chemical composition. beta-NaCaPO4 has been found to be an effective sintering agent which causes neither decomposition of HA nor formation of other undesired phases. PMID:9199762

Suchanek, W; Yashima, M; Kakihana, M; Yoshimura, M

1997-07-01

91

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

92

Hydroxyapatite–zirconia composite coatings via the plasma spraying process  

Microsoft Academic Search

Hydroxyapatite (HA) coatings have been deposited on artificial hip prosthesis as a bioactive surface to induce a direct chemical bond with natural bones and hence achieve a biological fixation onto implants. However, its intrinsic weak mechanical properties have always been the main obstacle to its applications, especially in the area of orthopedic applications, where implants have to withstand medium–high loading.

V. J. P Lim; K. A Khor; L Fu; P Cheang

1999-01-01

93

Hydroxyapatite-coated Ti–6Al–4V  

Microsoft Academic Search

The present investigation examines the effect of coating thickness on the fatigue behaviour of hydroxyapatite (HA)-coated Ti–6Al–4V. Uniaxial fatigue tests were conducted on grit blasted Ti–6Al–4V coupons with HA coatings deposited by atmospheric plasma-spray at thicknesses of 0, 25, 50, 75, 100, and 150?m, as well as on grit blasted specimens that had received a stress relieving heat treatment. Coupons

A. K. Lynn; D. L. DuQuesnay

2002-01-01

94

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

95

The effects of ZrO 2 on the phase compositions of plasma sprayed HA\\/YSZ composite coatings  

Microsoft Academic Search

The low bonding strength of plasma sprayed hydroxyapatite (HA) coating has been a point of potential weakness in its application as biomedical prosthesis. In the present study, yttria (8wt.%) stabilized zirconia (YSZ) has been used to enhance the mechanical properties of HA coatings. This paper focused on the effects of YSZ additions (in the range 10–50 wt.%) on the phase

K. A Khor; L Fu; V. J. P Lim; P Cheang

2000-01-01

96

Metallic coating of microspheres  

SciTech Connect

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

Meyer, S.F.

1980-08-15

97

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

98

Electrophoretic deposition of porous hydroxyapatite scaffold.  

PubMed

Bioactive porous hydroxyapatite (HA) scaffold was fabricated using electrophoretic deposition (EPD) technique in the present work. Bulk HA scaffold was achieved by repeated deposition. The green scaffold was sintered at 1200 degrees C to 82% of the theoretical density. Scanning electron microscopy examination and mercury porosimetry measurement have shown that the porosity remains interconnected and a range of pore size from several microns to hundreds of microns was obtained. X-ray diffraction analysis was performed and confirmed that there is no HA decomposition during the sintering process. Mechanical characterization has also shown that the EPD scaffold possesses excellent properties. Cell culturing experiment was carried out and the result shows that the scaffold bioactivity is not only dependent on the interconnectivity of the pores, but also the pore size. PMID:12809779

Ma, J; Wang, C; Peng, K W

2003-09-01

99

Silk fibroin regulated mineralization of hydroxyapatite nanocrystals  

NASA Astrophysics Data System (ADS)

In the present study, silk fibroin was employed to regulate the mineralization of hydroxyapatite (HA) nanocrystals. The calcium phosphate crystals precipitated in the aqueous solution of silk fibroin at pH 8 and room temperature. The depositions collected at different reaction time were detected by X-ray diffraction analysis to investigate the mineralization process of calcium phosphate. The results indicated that fibroin protein could significantly promote the crystal growth of HA. The formed HA crystals were also studied by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The FTIR results revealed that the HA crystals are carbonate-substituted HA and compounded with fibroin. There are strong chemical interactions between HA and fibroin protein, which can be derived from the blue shift of amide II peak (from the position of 1517 1539 cm-1). TEM images showed that the mineralized nanofibrils in the composites are rod like in shape with the diameter of about 2 3 nm. Selected area electron diffraction patterns from the composites exhibit polycrystalline rings, which were well indexed as the HA phase with 0 0 2 preferential orientations.

Kong, X. D.; Cui, F. Z.; Wang, X. M.; Zhang, M.; Zhang, W.

2004-09-01

100

Interface activation and surface characteristics of Ti\\/TiN\\/HA coated sintered stainless steels  

Microsoft Academic Search

Interface activation and surface characteristics of Ti\\/TiN\\/HA film coated sintered stainless steels (SSS) have been investigated\\u000a by electrochemical and biocompatibility tests. HA (hydroxyapatite), Ti, and Ti\\/TiN film coatings were applied using electron-beam\\u000a deposition method (EB-PVD). Ti, Ti\\/TiN, and Ti\\/TiN\\/HA film coated surfaces and layers were investigated by SEM and XPS. The\\u000a coated films showed micro-columnar structure, and Ti\\/TiN\\/HA films were

Han-Cheol Choe; Yeong-Mu Ko

2006-01-01

101

Preparation and characterization of nano-hydroxyapatite\\/silk fibroin porous scaffolds  

Microsoft Academic Search

Novel tissue engineering scaffold materials of nano-hydroxyapatite (nHA)\\/silk fibroin (SF) biocomposite were prepared by freeze-drying. The needle-like nHA crystals of about 10 nm in diameter by 50–80 nm in length, which were uniformly distributed in the porous nHA\\/SF scaffolds, were prepared by a co-precipitation method with a size. The as-prepared nHA\\/SF scaffolds showed good homogeneity, interconnected pores and high porosity.

Lin Liu; Jinying Liu; Mingqi Wang; Sijia Min; Yurong Cai; Liangjun Zhu; Juming Yao

2008-01-01

102

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

Microsoft Academic Search

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

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

2005-01-01

103

High temperature in-situ XRD of plasma sprayed HA coatings  

Microsoft Academic Search

The control of phase transformations in plasma sprayed hydroxyapatite (HA) coatings are critical to the clinical performance of the material. This paper reports the use of high temperature X-ray diffraction (HT-XRD) to study, in-situ, the phase transformations occurring in plasma sprayed HA coatings. The coatings were prepared using different spray power levels (net plasma power of 12 and 15kW) and

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

2002-01-01

104

The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth  

PubMed Central

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

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

2012-01-01

105

Mechanical and biological properties of hydroxyapatite reinforced with 40 vol. % titanium particles for use as hard tissue replacement  

Microsoft Academic Search

Hydroxyapatite (HA)-based composite reinforced with 40 vol. % Ti particles was fabricated by the optimal technical condition of hot pressing technique. The mechanical and biological properties of the composite were studied by mechanical and in vivo methods. The experimental results show that HA and Ti phases are the predominant phases of the composite with partially decomposition of HA phase into

Chenglin Chu; Xiaoyan Xue; Jingchuan Zhu; Zhongda Yin

2004-01-01

106

Effect of particle size on molten states of starting powder and degradation of the relevant plasma-sprayed hydroxyapatite coatings  

Microsoft Academic Search

Crystallinity of hydroxyapatite (HA) coatings is an important parameter to evaluate their stability. Variation of the size distribution of the starting powder is one way to alter crystallinity of coatings. The fundamental reason might be the variation of molten states of HA powders with different particle sizes. In the experiments, HA particles sized between 1 and 180 ?m were divided

Weidong Tong; Jiyong Chen; Xudong Li; Yang Cao; Zongjian Yang; Jiaming Feng; Xingdong Zhang

1996-01-01

107

Microsphere thermal deformeter  

NASA Astrophysics Data System (ADS)

A highly sensitive thermal deformeter was developed for measuring submicron variations in the dimensions of glass microspheres as a function of temperature. This made it possible to determine the maximum temperature at which these microspheres can be DT (deuterium and tritium) filled through permeation without nonreversible deformation in the preparation of inertial confinement fusion targets.

Koo, J. C.

1980-10-01

108

Production of hollow aerogel microspheres  

DOEpatents

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

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

1990-12-31

109

Hydroxyapatite as a carrier for bone morphogenetic protein.  

PubMed

Bone morphogenetic proteins (BMPs) can induce the formation of new bone in numerous orthopedic and dental applications in which loss of bone is the main issue. The combination of BMP with a biomaterial that can carry and deliver proteins has been demonstrated to maximize the therapeutic effects of BMPs. However, no ideal candidate with optimal characteristics as a carrier has emerged for clinical use of BMPs. Hydroxyapatite (HA) is a potential BMP carrier with its osteoconductive properties and desirable characteristics as a bone graft biomaterial. In this study, 3 different methods to load BMP into HA materials were characterized and compared based on the BMP uptake and release profile. BMP was loaded into HA in 3 ways: (1) incorporation of BMP during HA precipitation, (2) HA immersion in BMP solution, and (3) BMP incorporation during dicalcium phosphate dihydrate (DCPD) conversion to HA. The size of HA crystals decreased when BMP was loaded during HA precipitation and HA immersion in BMP solution; however, it did not change when BMP was loaded during DCPD-to-HA conversion. The highest BMP uptake was achieved using the immersion method followed by HA precipitation, and the lowest via DCPD conversion. It is interesting to note that BMP loading during HA precipitation resulted in sustained and prolonged BMP release compared with the 2 other BMP loading methods. In conclusion, BMP incorporation during HA precipitation revealed itself to be the best loading method. PMID:20662667

Rohanizadeh, Ramin; Chung, Kimberly

2010-07-21

110

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

Microsoft Academic Search

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

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

2004-01-01

111

Mechanical and in vivo performance of hydroxyapatite implants with controlled architectures  

Microsoft Academic Search

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

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

2002-01-01

112

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

Microsoft Academic Search

Hydroxyapatite (HA) reinforced high density polyethylene (HDPE) was invented as a biomaterial for skeletal applications. In this investigation, tribological properties (e.g. wear rate and coefficient of friction) of unfilled HDPE and HA\\/HDPE composites were evaluated against the duplex stainless steel in dry and lubricated conditions, with distilled water or aqueous solutions of proteins (egg albumen or glucose) being lubricants. Wear

M. Wang; M. Chandrasekaran; W. Bonfield

2002-01-01

113

Plasma-sprayed carbon nanotube reinforced hydroxyapatite coatings and their interaction with human osteoblasts in vitro  

Microsoft Academic Search

Carbon nanotubes (CNT) possess excellent mechanical properties to play the role as reinforcement for imparting strength and toughness to brittle hydroxyapatite (HA) bioceramic coating. However, lack of processing technique to uniformly distribute multiwalled CNTs in HA coating and limited studies and sparse knowledge evincing toxicity of CNTs has kept researchers in dispute for long. In the current work, we have

Arvind Agarwala

114

Induction plasma sprayed nano hydroxyapatite coatings on titanium for orthopaedic and dental implants  

Microsoft Academic Search

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared

Mangal Roy; Amit Bandyopadhyay; Susmita Bose

2011-01-01

115

Hydroxyapatite nano and microparticles: Correlation of particle properties with cytotoxicity and biostability  

Microsoft Academic Search

Synthetic colloid and gel hydroxyapatite (HA) nanoparticles (NPs) were spray dried to form microparticles (MPs). These are intended for use as slow release vaccine vectors. The physico-chemical properties of gel and colloid NPs and MPs were compared to those of HA obtained commercially. Their cytotoxicity to human monocytes'-derived macrophages (HMMs) was assessed in vitro using a range of techniques. These

M. Motskin; D. M. Wright; K. Muller; N. Kyle; T. G. Gard; A. E. Porter; J. N. Skepper

2009-01-01

116

Water-based sol–gel synthesis of hydroxyapatite: process development  

Microsoft Academic Search

Hydroxyapatite (HA) ceramics were synthesized using a sol–gel route with triethyl phosphite and calcium nitrate as phosphorus and calcium precursors, respectively. Two solvents, water and anhydrous ethanol, were used as diluting media for HA sol preparation. The sols were stable and no gelling occurred in ambient environment for over 5 days. The sols became a white gel only after removal

Dean-Mo Liu; T Troczynski; Wenjea J Tseng

2001-01-01

117

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

Microsoft Academic Search

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

Y. X. Pang; X. Bao

2003-01-01

118

Hydroxyapatite synthesis using EDTA.  

PubMed

Bone comprises structure of the body and 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 being time consuming make the production difficult. In this study, we synthesized hydroxyapatite with EDTA. Freeze-dried bone allograft (Hans Biomed) was used as the control group. Synthesized hydroxyapatite was a rod-shaped, white powdery substance with 2- to 5-?m length and 0.5- to 1-?m width. X-ray diffraction showed the highest sharp peak at 32°C and high peaks at 25.8°C, 39.8°C, 46.8°C, 49.5°C, and 64.0°C, indicating a similar substance to the freeze-dried bone allograft. After 3 days, the cell growth of synthesized hydroxyapatite showed 1.5-fold more than did the bone allograft. Cellular and media alkaline phosphate activity increased similar to the bone allograft. 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 product can be manufactured in large quantity. It can be also transformed into scaffold structure, which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products. PMID:23714942

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

2013-05-01

119

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

Microsoft Academic Search

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

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

2002-01-01

120

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

Microsoft Academic Search

Polyetheretherketone–hydroxyapatite composites were developed as alternative materials for load-bearing orthopedic applications. The amount of hydroxyapatite (HA) incorporated into the polyetheretherketone (PEEK) polymer matrix ranges from 5 to 40vol% and these materials were successfully fabricated by injection molding. This study presents the mechanical and biological behavior of the composite materials developed. It was found that the amount of HA in the

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

2003-01-01

121

Fabrication of corrosion resistant, bioactive and antibacterial silver substituted hydroxyapatite\\/titania composite coating on Cp Ti  

Microsoft Academic Search

The present work is aimed at developing a bioactive, corrosion resistant and anti bacterial nanostructured silver substituted hydroxyapatite\\/titania (AgHA\\/TiO2) composite coating in a single step on commercially pure titanium (Cp Ti) by plasma electrolytic processing (PEP) technique. For this purpose 2.5wt% silver substituted hydroxyapatite (AgHA) nanoparticles were prepared by microwave processing technique and were characterized by X-ray diffraction (XRD), Fourier-transform

Kotharu Venkateswarlu; Nagumothu Rameshbabu; Arumugam Chandra Bose; Veerappan Muthupandi; Sankaran Subramanian; Davoodbasha MubarakAli; Nooruddin Thajuddin

122

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

123

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

124

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

125

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

126

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

127

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

128

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

129

Effect of atmosphere on phase transformation in plasma-sprayed hydroxyapatite coatings during heat treatment.  

PubMed

The purpose of this study was to evaluate the effect of atmosphere on the phase transformation in hydroxyapatite (HA) coatings during heat treatment by varying the atmosphere in the furnace pipe. Heat treatment always increased the crystallinity of HA coatings regardless of the kind of atmosphere. Water molecules in atmosphere further promoted HA recrystallization during heat treatment. In a dry atmosphere, tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) were more stable than HA, so heat treatment could not convert them into HA. However, in a humid atmosphere, heat treatment would transform TCP and TTCP into HA by hydrolytic reactions. PMID:8978648

Chen, J; Tong, W; Cao, Y; Feng, J; Zhang, X

1997-01-01

130

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

SciTech Connect

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

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

2010-04-15

131

Development of nano-hydroxyapatite coating by electrohydrodynamic atomization spraying.  

PubMed

Electrohydrodynamic atomisation (EHDA) spraying of a hydroxyapatite (HA) suspension consisting of nano-particles (nHA) has been used to produce a HA coating comprising of nanostructured surface topography. In EHDA the suspension is jetted from a needle under an electric field. Obtaining the stable cone-jet mode of EHDA is critical to improve the quality and optimise the morphology of HA coatings, therefore a systematic investigation of the effects of several key processing parameters, such as suspension flow rate, applied voltage and distance between the needle and substrate, and needle size was carried out in this work. The HA coatings processed under different spraying parameters were compared and then scored according to uniformity and microstructural integrity. It was found that all of these parameters had a very significant influence on the morphology of nHA coating prepared. Under an optimised processing condition, where a needle orifice diameter of 300 microm, kept at a distance of 20 mm from the substrate, a flow rate of 20 microL/min, and the applied voltage kept within 4.3 kV and 5.2 kV, a uniform nHA coating was obtained. This is a crucial step forward in obtaining advanced nano-hydroxyapatite coatings of high quality for biomedical applications by using EHDA spraying. PMID:17992471

Li, Xiang; Huang, Jie; Edirisinghe, Mohan

2007-11-08

132

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

2012-09-11

133

Immobilization of DNA on nano-hydroxyapatite and their interaction with carbon nanotubes  

Microsoft Academic Search

Here we present a preliminary study on the interaction of bio-molecules (deoxyribonucleic acid (DNA) and nano-hydroxyapatite (HA)) with multi-wall carbon nanotubes (MWCNTs). Initially, nano-size hydroxyapatite was interacted with functionalized carbon nanotubes (FCNTs, HFCNTs) and then 100 base pair (bp) DNA was immobilized (DHFCNTs). Well-known acid treatment was used to functionalize the MWCNTs. The characteristic vibrational and stretching modes of hydroxyl

Rizwan Wahab; S. G. Ansari; Young Soon Kim; T. R. Mohanty; I. H. Hwang; Hyung-Shik Shin

2009-01-01

134

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

135

Biaxial residual stress states of plasma-sprayed hydroxyapatite coatings on titanium alloy substrate  

Microsoft Academic Search

Biaxial residual stress states of plasma-sprayed hydroxyapatite coatings (HACs) on titanium alloy substrate as a function of plasma power, powder feed rate and coating thickness were studied by X-ray `sin2?’ method. The Young's modulus of hydroxyapatite (HA), required for the stress analysis, was measured from the separated free coating by three-point bending test method. It was found that the directions

Y. C Yang; Edward Chang; B. H Hwang; S. Y Lee

2000-01-01

136

Silicate-doped hydroxyapatite and its promotive effect on bone mineralization  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

137

Particle size modeling and morphology study of chitosan/gelatin/nanohydroxyapatite nanocomposite microspheres for bone tissue engineering.  

PubMed

In this study, nanocomposite microspheres based on chitosan/gelatin/nanohydroxyapatite were fabricated, and effects of the nanohydroxyapatite/biopolymer (chitosan/gelatin) weight ratio (nHA/P), stirring rate, chitosan concentration and biopolymer concentration on the particle size, and morphology of nanocomposite microspheres were investigated. Particle size of microspheres was modeled by design of experiments using the surface response method. Particle size, morphology of microspheres, and distribution of nanoparticles within the composite microspheres were evaluated using an optical microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. X-ray diffraction and Fourier transform infrared spectroscopy were applied to study the physical and chemical characteristics of microspheres. Results showed that by modulating the nHA/P ratio, chitosan concentration, polymer concentration, and stirring rate, it is possible to fabricate microspheres in wide rages of particle size (5-150 ?m). Analysis of variance confirmed that the modified quadratic model can be used to predict the particle size of nanocomposite microspheres within the design space. SEM studies showed that microspheres with different compositions had totally different morphologies from dense morphologies to porous ones. TEM images demonstrated that nanoparticles were distributed uniformly within the polymeric matrix. MTT assay and cell culture studies showed that microspheres with different compositions possessed good biocompatibility. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. PMID:23184337

Bagheri-Khoulenjani, Shadab; Mirzadeh, Hamid; Etrati-Khosroshahi, Mohammad; Shokrgozar, Mohammad Ali

2012-11-27

138

HA/DR Lessons Learned.  

National Technical Information Service (NTIS)

Military Humanitarian Assistance and Disaster Relief (HA/DR) operations over the past 7 years produced common learned lessons. After action reports, studies, and independent articles from the Indonesian tsunami in 2004, Hurricane Katrina in 2005, and the ...

M. T. Koch

2011-01-01

139

Osteoclastic resorption of calcium phosphate ceramics with different hydroxyapatite\\/?-tricalcium phosphate ratios  

Microsoft Academic Search

To study the influence of calcium phosphate ceramic solubility on osteoclastic resorption, neonatal rabbit bone cells were cultured for 2 days on hydroxyapatite (HA), ?-tricalcium phosphate (?-TCP) and two types of biphasic calcium phosphate (BCP) with HA\\/?-TCP ratios of 2575 and 7525. Solubility was regulated by varying the ratio of less-soluble HA and more-soluble ?-TCP. After removal of stromal cells

S. Yamada; D. Heymann; J.-M. Bouler; G. Daculsi

1997-01-01

140

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

141

Ectopic osteogenesis with biphasic ceramics of hydroxyapatite and tricalcium phosphate in rabbits  

Microsoft Academic Search

Porous calcium phosphate ceramics consisting of hydroxyapatite (HA) and tricalcium phosphate (TCP) with different HA to TCP ratio were implanted intramuscularly in rabbits for six months in order to carry out a comparative study on osteogenic activity of the ceramics. Bone formation was detected only in HT73 (HA to TCP ratio; 7–3) specimens. Other implants, HT28 (2–8) and HT010 (0–10),

K. Kurashina; H. Kurita; Q. Wu; A. Ohtsuka; H. Kobayashi

2002-01-01

142

Fabrication and characterization of thin nano-hydroxyapatite coatings on titanium  

Microsoft Academic Search

Titanium is the most commonly used metallic material in the manufacture of orthopedic implants, and hydroxyapatite (HA) is bioactive and biocompatible when used as bone substitutes. To achieve better biocompatibility and excellent mechanical performance of prostheses, HA coating is often fabricated on titanium surfaces. The present study used dip-coating techniques to fabricate HA coating of organic sol–gel of Ca(NO3)2·4H2O and

Linghong Guo; Hui Li

2004-01-01

143

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

144

Morphology, hydrogen-bonding and crystallinity of nano-hydroxyapatite\\/polyamide 66 biocomposites  

Microsoft Academic Search

Nano-composites for load-bearing bone repair consisting of nano-hydroxyapatite (n-HA) and polyamide 66 were prepared by co-precipitation in ethanol. The relationships between structure and property of the composites were studied. Infrared spectrum results showed that n-HA and PA66 were mainly linked by hydrogen-bonding, which mainly existed between OH of n-HA and amide of PA66. The X-ray diffraction results revealed that the

Xiang Zhang; Yu-Bao Li; Yi Zuo; Guo-Yu Lv; Yuan-Hua Mu; Hong Li

2007-01-01

145

Hydroxyapatite-reinforced polymer biocomposites for synthetic bone substitutes  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA)-reinforced polymer biocomposites offer a robust system to engineer synthetic bone substitutes with tailored mechanical, biological, and surgical functions. The basic design rationale has been to reinforce a tough, biocompatible polymer matrix with a bioactive HA filler. A large number of studies have investigated modifications to the biocomposite structure and composition, aimed at improving the mechanical properties, often through modified or novel processing methods. In this article, the effects of the polymer composition and molecular orientation; the HA/polymer interface; and the HA-reinforcement content, morphology, preferred orientation, and size are reviewed with respect to mechanical properties, drawing frequent comparisons between various HA-reinforced polymer composites and bone tissue.

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

2008-03-01

146

Surface modification of zinc-containing hydroxyapatite by tartaric acid  

NASA Astrophysics Data System (ADS)

The surface of Zn-substituted hydroxyapatites (Ca(10-x)Znx(PO4)6(OH)2, with 0 ? x ? 2, CaxZnxHA) modified by tartaric acid was investigated by various techniques. XRD powder patterns revealed that synthesized samples were single phase of HA with broadened XRD re?ections. FTIR and (13C, 1H and 31P) MAS NMR measurements confirmed the grafting of the tartaric acid on the apatite surface. Chemical analysis showed that for ZnHA the grafted acid amount increases with the increase of the acid concentration in the starting solutions, while for HA, it remained constant, indicating more reactivity for ZnHA surface. A mechanism of surface modification is proposed based on the obtained results.

Turki, Thouraya; Othmani, Masseoud; Bac, Christophe Goze; Rachdi, Férid; Bouzouita, Khaled

2013-11-01

147

Crystal chemistry of hydroxyapatite deposited on titanium by sputtering technique.  

PubMed

Crystalline hydroxyapatite (HA) powder was coated on titanium substrate by radio frequency (RF) magnetron sputtering. The coating was homogeneous thin film and the thickness was 1microm. Crystallinity of the HA coating was low and Ca/P ratio was high as 3.0. Particle sizes were 40 to approximately 100 nm, and the crystallite size was calculated by 30 to approximately 50 nm using an X-ray diffractometry (XRD) and a transmission electron microscopy (TEM). When the coating was heated at 800 degrees C for 1 h, the low crystalline HA grew up crystalline HA, and a diffraction pattern of CaO appeared. When the coating was immersed in pH 7.4 of bovine serum for 1 week, c-axis of HA increased. PMID:11202150

Ozeki, K; Yuhta, T; Aoki, H; Nishimura, I; Fukui, Y

2000-01-01

148

Electrohydrodynamic coating of metal with nano-sized hydroxyapatite.  

PubMed

Electrohydrodynamic spray deposition of a hydroxyapatite (HA) suspension consisting of nano-particles has been used to create a hydroxyapatite coating comprising of nanostructured surface topography. Preliminary coating experiments were carried out on an Al substrate and 30 s was found to be the most appropriate coating time. HA coating on titanium for this duration was found to be well-bonded to the substrate after heat-treatment. A thickness of 2 mum was achieved in 30 s and formation of a bone-like apatite on the surface was detected after incubation of the heat-treated coated Ti in simulated body fluid. Therefore, we have uncovered a new procedure by which nano-biomaterials can be deposited on real orthopedic substrates to prepare bioactive thin coatings in a simple and easy manner. PMID:18032815

Li, Xiang; Huang, Jie; Ahmad, Zeeshan; Edirisinghe, Mohan

2007-01-01

149

Sonochemical IN SITU Synthesis of Hydroxyapatite in Hdpe and PMMA  

NASA Astrophysics Data System (ADS)

In the present work, characterization of composite materials based on HDPE and PMMA filled with nanometric hydroxyapatite synthesized in situ by high frequency ultrasound has been carried out. For the composites preparation dilutions of the commercial polymers, using decaline as solvent for the HDPE and 2-butanone for PMMA, were employed. For the synthesis of Hydroxyapatite (HA), ammonium phosphate [(NH4)2HPO4] and calcium hydroxide [Ca(OH)2] were used as precursors. The products obtained were characterized by FTIR and TEM. The results showed that when PMMA was used as matrix, the presence of nanometric HA with clear interactions with the PMMA matrix was obtained. When HDPE was used as matrix a complex complex calcium phase was obtained and without interaction with the matrix.

Cristina, Parra; Gema, González; Carmen, Albano

2008-08-01

150

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:24092200

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

2013-01-01

151

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

152

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.

153

Formation of highly oriented hydroxyapatite in hydroxyapatite/titanium composite coating by radio-frequency thermal plasma spraying.  

PubMed

Highly oriented hydroxyapatite (HA) coatings with excellent adhesion were successfully obtained on titanium (Ti) and titanium alloy through a radio-frequency thermal plasma spraying method. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the composition from Ti-rich to HA-rich toward the upper layer of the formed coatings. The bond (tensile) strength of the HA/Ti composite coatings was ca. 40-50 MPa. XRD patterns showed that the topmost HA layer of the coatings had an apatite structure with (00l) preferred orientation. The degree of this orientation showed a tendency to increase with an increase in the substrate temperature during spraying. PMID:15348531

Inagaki, Masahiko; Yokogawa, Yoshiyuki; Kameyama, Tetsuya

2003-10-01

154

Formation of hydroxyapatite in new calcium phosphate cements  

Microsoft Academic Search

SynopsisTetracalcium phosphate (TTCP) has been shown previously to be an essential component of self-setting calcium phosphate cements that form hydroxyapatite (HA) as the only end-product. We report herein on a new self-setting calcium phosphate cement that does not contain TTCP. These cements consist of dicalcium phosphate anhydrous (DCPA), dicalcium phosphate dihydrate (DCPD), ?-tricalcium phosphate, or amorphous calcium phosphate and, as

S. Takagi; L. C. Chow; K. Ishikawa

1998-01-01

155

Two zones microstructure of suspension plasma sprayed hydroxyapatite coatings  

Microsoft Academic Search

The plasma spraying process of hydroxyapatite (HA) suspension was optimized in order to obtain possibly dense and well adherent coatings onto aluminum and titanium alloy substrates. The process variables included the suspension liquid (water, ethanol or their mixture), the pneumatic pressure applied to inject the suspension (0.2 to 0.8bar), type of injection (nozzle or atomizer), geometry of suspension injection to

Stefan Kozerski; Lech Pawlowski; Roman Jaworski; Francine Roudet; Fabrice Petit

2010-01-01

156

Total hip replacement with an entirely hydroxyapatite-coated prosthesis  

Microsoft Academic Search

The first 100 consecutive entirely hydroxyapatite (HA)-coated hip arthroplasties in 86 patients (mean age, 56.2 years [range, 32–73 years]; female-to-male ratio, 75:25) were followed with standardized radiographs annually up to 5 years. All components developed 100% intimate bone-implant contact, being gradually reduced to 99.5% ± 3.8% by 2 partial periacetabular lines and on the femoral side to 94.0% ± 6.1%

M. Røkkum; A. Reigstad

1999-01-01

157

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

158

Plasma spraying of functionally graded hydroxyapatite\\/Ti–6Al–4V coatings  

Microsoft Academic Search

Functionally graded hydroxyapatite (HA)\\/Ti–6Al–4V coatings were produced by plasma spray process using specially developed HA-coated Ti–6Al–4V composite powders as feedstock. The microstructure, density, porosity, microhardness, and Young's modulus (E) were found to change progressively through the three-layered functionally graded coating that composed of the layers 50 wt.% HA\\/50 wt.% Ti–6Al–4V; 80 wt.% HA\\/20 wt.% Ti–6Al–4V, and HA. No distinct interface

K. A Khor; Y. W Gu; C. H Quek; P Cheang

2003-01-01

159

Effect of Hydrothermal Treatment on Sinterability of Hydroxyapatite  

NASA Astrophysics Data System (ADS)

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 °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 °C, 900 °C and 1000 °C for 10 min with the heating rate of 25 °C.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 °C, 900 °C and 1000 °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 °C and 1000 °C.

Kawagoe, D.; Fujimori, H.; Goto, S.; Yamasaki, N.; Ioku, K.

2006-05-01

160

Dual functional selenium-substituted hydroxyapatite  

PubMed Central

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

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

2012-01-01

161

Microstructures and bond strengths of plasma-sprayed hydroxyapatite coatings on porous titanium substrates.  

PubMed

Hydroxyapatite (HA) coating was carried out by plasma spraying on bulk Ti substrates and porous Ti substrates having a Young's modulus similar to that of human bone. The microstructures and bond strengths of HA coatings were investigated in this study. The HA coatings with thickness of 200-250 microm were free from cracks at interfaces between the coating and Ti substrates. XRD analysis revealed that the HA powder used for plasma spraying had a highly crystallized apatite structure, while the HA coating contained several phases other than HA. The bond strength between the HA coating and the Ti substrates evaluated by standard bonding test (ASTM C633-01) were strongly affected by the failure behavior of the HA coating. A mechanism to explain the failure is discussed in terms of surface roughness of the plasma-sprayed HA coatings on the bulk and porous Ti substrates. PMID:15965595

Oh, Ik-Hyun; Nomura, N; Chiba, A; Murayama, Y; Masahashi, N; Lee, Byong-Taek; Hanada, S

2005-07-01

162

In Vitro and In Vivo Evaluation of a nHA\\/PA66 Composite Membrane for Guided Bone Regeneration  

Microsoft Academic Search

A nano-hydroxyapatite\\/polyamide 66 (nHA\\/PA66) composite with good bioactivity and osteoconductivity is employed to develop a novel porous membrane with an asymmetric structure. In order to investigate the biocompatibility and the effect on guided bone regeneration (GBR) of nHA\\/PA66 porous membrane, the proliferation, viability, morphology and alkaline phosphatase activity (ALP) of the osteoblast-like cell line (MG63) cultured on the membrane were

Jidong Li; Yi Man; Yi Zuo; Li Zhang; Cui Huang; Man Liu; Yubao Li

2011-01-01

163

Processing of HA-coated Ti–6Al–4V by a ceramic slurry approach: an in vitro study  

Microsoft Academic Search

Hydroxyapatite-coated titanium alloy composite powders (Ti–6Al–4V\\/HA) was produced by a ceramic slurry approach. The aim was to evaluate the stability of the coating when subjected to a physiological mediumsimulated body fluid (SBF). Three consolidation conditions (700°C for 5h, 700°C for 8h and 700°C for 11h) were used in the production of the Ti–6Al–4V\\/HA composite powders. Results showed that biodissolution followed

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

2001-01-01

164

Growth of hydroxyapatite in a biocompatible mesoporous ordered silica.  

PubMed

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

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

2006-02-03

165

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

166

Characterization of sintered titanium/hydroxyapatite biocomposite using FTIR spectroscopy.  

PubMed

Fourier transform infrared (FTIR) spectroscopy was employed to characterize the phase changes of hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), HA) in a titanium/HA biocomposite during sintering. The effects of sintering temperature and the presence of Ti on the decomposition of HA were examined. It was observed that pure HA was stable in argon atmosphere at temperatures up to 1,200 degrees C, although the dehydroxylation of pure HA was promoted by the increase in sintering temperature. In the Ti/HA system, on the other hand, the presence of Ti accelerated dehydroxylation and the decomposition of HA was detected at a temperature as low as 800 degrees C. Tetracalcium phosphate (Ca(4)P(2)O(9), TTCP) and calcium oxide (CaO) were the dominant products of the decomposition, but no tricalcium phosphate (Ca(3)(PO(4))(2), TCP) was detected due to phosphorus diffusion and possible reactions during the thermal process. The main decomposed constituents of HA in Ti/HA system at high temperatures (> or =1,200 degrees C) would be CaO and amorphous phases. PMID:19034619

Ye, Hezhou; Liu, Xing Yang; Hong, Hanping

2008-11-26

167

New model for the hydroxyapatite-octacalcium phosphate interface.  

PubMed

Some experimental results have indicated that hydroxyapatite (HA) and octacalcium phosphate (OCP) can form an epitaxic interface. Subsequently the OCP-HA interface has become of great biological interest in the context of mineralized tissue formation. In this work a new OCP-HA interface model based on Brown's proposed configuration [Brown (1962), Nature, 197, 1048-1050] and using the minimum interface free-energy optimization is presented. This new model is formed by half a unit cell of HA and one unit cell of OCP, as in Brown's model, but in our case [1-210] of HA is 'glued' with [010] of OCP. Therefore, the relationship found was: [000-1](HA) parallel to [001](OCP) and [1-210](HA) parallel to [010](OCP). Self-consistent field methods were used for the analysis of Brown's model and ours. It is shown that the atoms in our model have similar environments as in the HA and OCP unit cells and that, as a result of the differences between HA and OCP unit-cell parameters, this interface presents misfit-dislocation-like features. High-resolution transmission electron microscopy (HREM) simulated images for the new interface model have been included and, when they are compared with the experimental ones, the similarity is quite good. PMID:12657811

Fernández, M E; Zorrilla-Cangas, C; García-García, R; Ascencio, J A; Reyes-Gasga, J

2003-03-26

168

Antibacterial Property of Cold-Sprayed HA-Ag/PEEK Coating  

NASA Astrophysics Data System (ADS)

The antibacterial behavior of HA-Ag (silver-doped hydroxyapatite) nanopowder and their composite coatings were investigated against Escherichia coli (DH5?). HA-Ag nanopowder and PEEK (poly-ether-ether-ketone)-based HA-Ag composite powders were synthesized using in-house powder processing techniques. Bacteria culture assay of HA-Ag nanopowder and their composite powders displayed excellent bacteriostatic activity against E. coli. The antibacterial activity increased with increasing concentration of HA-Ag nanoparticle in these composite powders. These nanocomposite powders were subsequently used as feedstock to generate antibacterial coatings via cold spray technology. The ratios of HA-Ag to PEEK in their composite powders were 80:20, 60:40, 40:60, and 20:80 (wt.%). Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out using FESEM/EDX and XRD. Antibacterial nanocomposite HA-Ag/PEEK coatings were successfully deposited using cold spraying parameters of 11-12 bars at preheated air temperature between 150 and 160 °C. These as-sprayed coatings of HA-Ag/PEEK composite powders comprising varying HA-Ag and PEEK ratios retained their inherent antibacterial property as verified from bacterial assay. The results indicated that the antibacterial activity increased with increasing HA-Ag nanopowder concentration in the composite powder feedstock and cold-sprayed coating.

Sanpo, Noppakun; Tan, Meng Lu; Cheang, Philip; Khor, K. A.

2009-03-01

169

Nanostructured nickel-free austenitic stainless steel composites with different content of hydroxyapatite  

NASA Astrophysics Data System (ADS)

The aim of this work is to show that Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite can be synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). Hydroxyapatite was introduced into stainless steel because it is intensively studied for bone repair and replacement applications. Nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels. Therefore it's combination with hydroxyapatite that has high biocompatibility and ability to bond to bone could have improved properties, as well.To confirm nanocrystalline structure of obtained material and reveal topographical features of the surface, small-angle X-ray analysis (SAXS) and atomic force microscopy (AFM) were used. Results are consistent and the mean grain size of the obtained materials do not exceed 100 nm.

Tulinski, Maciej; Jurczyk, Mieczyslaw

2012-11-01

170

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 30nm. A fibrous morphology (~400nm) of HA observed by TEM indicates that HA nucleates on chitosan chains. PMID:24094157

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

2013-07-12

171

Dissolution of calcium-deficient hydroxyapatite synthesized at different conditions  

SciTech Connect

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 168 h, the calcium and phosphate contents in solution were measured by induced coupled plasma optical emission spectrometry (OES). The dissolution behavior of calcium-deficient HA was highly dependent on the sample calcium/phosphorus (Ca/P) molar ratio of the original HA. Dissolution in water was enhanced with decreasing HA sample molar ratio. However, the dissolution process equilibrium was not achieved at the end of 168 h (7 days)

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

2003-03-15

172

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

PubMed

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. The sintered HA and HA-coated Ti surfaces enhanced osteoblast phenotypes in comparison with the bare Ti surface. The HA-coated Ti enabled antimicrobial activity against early colonizers of supra-gingival plaques, namely Streptococcus mitis and Streptococcus gordonii. Such antimicrobial activity may be caused by the surface hydrophilicity, thereby leading to a repulsion force between the HA-coated Ti surface and the bacterial cell membranes. On the contrary, the sintered HA sample was susceptible to infection of microorganisms. Thus, hydrophilic-modified HA-coated Ti may have potential for use in implantable medical devices. From the Clinical Editor: This study establishes that Hydroxyapatite (HA)-coated titanium (Ti) surface of implanted devices may result in an optimal microenvironment to control and prevent infections and may have potential future clinical applications. PMID:21782779

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

2011-07-23

173

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.

174

[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

175

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

2012-08-10

176

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

177

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

178

Mechanical performance and osteoblast-like cell responses of fluorine-substituted hydroxyapatite and zirconia dense composite  

Microsoft Academic Search

A fluorine-substituted hydroxyapatite (FHA) and zirconia (ZrO2) dense composite (50:50 by volume) was fabricated, and its feasibility for hard tissue applications was investigated in terms of its mechanical properties and osteo- blast-like cell (MG63) responses in vitro. The incorporation of fluorine into the hydroxyapatite (HA) structure was highly effective in producing a completely dense apatite-ZrO2 composite through a pressureless sintering

Hae-Won Kim; Jonathan C. Knowles; Long-Hao Li; Hyoun-Ee Kim

2005-01-01

179

Hydroxyapatite-alginate nanocomposite as drug delivery matrix for sustained release of ciprofloxacin.  

PubMed

Hydroxyapatite is a bioceramic which has a wide range of medical application for bone diseases. To enhance its usage, we have prepared ciprofloxacin loaded nano hydroxyapatite (HA) composite with a natural polymer, alginate, using wet chemical method at low temperature. The prepared composites were analyzed by various physicochemical methods. The results show that the nano HA crystallites are well intact with the alginate macromolecules. For the composite system FT-IR and micro Raman results are reported in this paper. Studies on the drug loading and drug release have been done. The drug is pre-adsorbed onto the ceramic particle before the formation of composite. The thermal behavior of composite has been studied using thermo gravimetric analysis (TGA). This work, reports that the nanocomposite prepared under optimum condition could prolong the release of ciprofloxacin compared with the ciprofloxacin loaded hydroxyapatite. PMID:22416574

Venkatasubbu, G Devanand; Ramasamy, S; Ramakrishnan, V; Kumar, J

2011-12-01

180

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

181

Accelerated degradation and improved bone-bonding ability of hydroxyapatite ceramics by the addition of glass.  

PubMed

Dense hydroxyapatite (HA) ceramics are useful bone substitutes, but they degrade minimally. One solution is to incorporate degradable materials in the HA. In this study, we manufactured glass-containing HA and investigated whether the degradability and bone-bonding ability of the HA were improved. The glass-containing HA was manufactured from a mixture of HA powder and 1.0 wt% glass powder. The control HA was manufactured from pure HA powder. In vitro degradability was evaluated by soaking in physiological saline, and a rabbit model was used to evaluate in vivo degradability and bone-bonding ability. Detaching tests were performed for all removed samples to quantify bone-bonding ability of each type of HA. The glass-containing HA showed higher degradability than the control HA, both in vitro and in vivo. The detaching failure load of the glass-containing HA was rapidly elevated after implantation and was higher than that of the control HA. Our results suggest that the dissolution of the added glass made the glass-containing HA degradable and that the detaching failure load of the glass-containing HA was elevated by reinforcement of the mechanical locking at the roughened interface. Incorporation of glass additives into HA can be concluded to be a good candidate for producing a bone substitute that can partially degrade and bond to bone firmly and rapidly. PMID:16753209

So, Kazutaka; Fujibayashi, Shunsuke; Neo, Masashi; Anan, Yukiko; Ogawa, Tetsuro; Kokubo, Tadashi; Nakamura, Takashi

2006-06-06

182

Hydroxyapatite formed on/in agarose gel induces activation of blood coagulation and platelets aggregation.  

PubMed

We reported earlier that hydroxyapatite (HA) formed on/in agarose gels (HA/agarose) produced by alternate soaking process is a bone-filling material possessing osteoconductive and hemostatic effects. This process could allow us to make bone-like apatite that was formed on/in organic polymer hydrogel matrices. Here, we investigated the mechanism of hemostasis induced by HA/agarose and found that HA/agarose, but not agarose or HA powder, significantly shortened activated partial thromboplastin time (APTT). While HA/agarose did not show significant platelet aggregation, it markedly enhanced adenosine diphosphate (ADP)-induced platelet aggregation. Moreover, Western blot analysis revealed selective adsorption of vitronectin onto HA/agarose. We also observed marked differences between HA powder and HA/agarose in their XRD patterns. The crystallinity of HA powder was much higher compared to that of HA/agarose. Furthermore, 50-100 nm of tube-form aggregations was observed in HA powder on the other hand 100-200 nm of particles was observed in HA/agarose by SEM observation. Thus 100-200 nm of low crystallized particles on the surface structure of HA/agarose may play an important role in hemostasis. Our results demonstrated a crucial role of HA/agarose in the mechanism of hemostasis and suggested a potential role for HA/agarose as a bone-grafting material. PMID:17022065

Arimura, Shin-ichiro; Kawahara, Ko-ichi; Biswas, Kamal Krishna; Abeyama, Kazuhiro; Tabata, Masashi; Shimoda, Toru; Ogomi, Daisuke; Matsusaki, Michiya; Kato, Shinya; Ito, Takashi; Sugihara, Kazumasa; Akashi, Mitsuru; Hashiguchi, Teruto; Maruyama, Ikuro

2007-05-01

183

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

2006-09-13

184

Biomedical nanocomposites of hydroxyapatite/polycaprolactone obtained by surfactant mediation.  

PubMed

The composite approach to combining bioactive ceramic and degradable polymer is a promising strategy in the development of bone regenerative matrices. Moreover, in the fabrication of composites, the nanoscale organization of each component should improve the level of structural integration as well as the resultant mechanical and biological properties. The aim of this study was to develop a novel nanocomposite system consisting of hydroxyapatite (HA) and poly(epsilon-caprolactone) (PCL), wherein the HA nanoparticles were uniformly dispersed within the PCL matrix. The strategy was based on applying an amphiphilic surfactant, oleic acid in this case, between the HA and PCL. Oleic acid, which belongs to the fatty acid family and is generally noncytotoxic at the levels used in this study, is believed to mediate the interaction between the hydrophilic HA and hydrophobic PCL. With the mediation of oleic acid, the HA nanoparticles were distributed uniformly within the PCL matrix on the nanoscale (distributed particle size of less than 1 microm), which is in marked contrast to the conventionally mixed HA-PCL composite, in which the HA particles were severely agglomerated. The developed nanocomposite had significantly higher mechanical strength than did the conventional composite and the pure PCL. Moreover, the osteoblastic cells showed a better proliferation behavior on the nanocomposite than on the conventional composite. This HA-PCL nanocomposite mediated by oleic acid is expected to be useful in the bone regeneration field. Moreover, this methodology is applicable to the nanocomposite processing of other biomedical materials. PMID:17390319

Kim, Hae-Won

2007-10-01

185

Porous chitosan microsphere for controlling the antigen release of Newcastle disease vaccine: preparation of antigen-adsorbed microsphere and in vitro release.  

PubMed

Porous chitosan microspheres suitable for the delivery of antigen were prepared using a wet phase-inversion method. The pore structure of the chitosan microsphere could be modified by the change of pH value of the coagulation medium, which is the aqueous tripolyphosphate (TPP) solution. High porosity of chitosan microsphere with an open porous structure on its surface was prepared by coagulation in TPP aq. solution of pH 8.9. The porous chitosan microspheres were modified chemically with reagents to introduce three types of functional groups; carboxyl, hydrophobic acyl and quaternary ammonium groups. Antigen of ND vaccine was immobilized into the pores of porous chitosan microspheres and the adsorbed antigen was assayed by the Hemoglobin Aggregation (HA) analytical method. Sustained-release of ND vaccine's antigen could be achieved through an adsorption-desorption release test. The chemical modifications of the porous chitosan microspheres have a strong large influence on the adsorption efficiency or release rates of the antigen investigated. The porous microspheres have a higher adsorption efficiency and the slower release rate of antigen when modified chemically with 3-chloro-2-hydroypropyltrimethylamonium chloride. PMID:10482415

Mi, F L; Shyu, S S; Chen, C T; Schoung, J Y

1999-09-01

186

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

187

In situ processing and properties of nanostructured hydroxyapatite\\/alginate composite  

Microsoft Academic Search

A series of hydroxyapatite\\/alginate (HA\\/Alg) nanocomposites with alginate amounts varying from 10 to 40 wt% were prepared\\u000a through in situ hybridization technique. The inorganic phase in the composites was carbonate-substituted HA with low crystallinity.\\u000a The crystallinity of HA decreased with the increase of alginate content. HA crystallites were needle-like in shape with a\\u000a typical size of 20 to 50 nm in length and

Li Wang; Yue Li; Chunzhong Li

2009-01-01

188

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

2012-03-14

189

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

Microsoft Academic Search

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

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

2002-01-01

190

Inhibition of Streptococcus mutans Adsorption to Hydroxyapatite by Low-molecular-weight Chitosans  

Microsoft Academic Search

The role of Streptococcus mutans in the initiation of dental caries has been recognized and attributed, at least in part, to its ability to colonize the tooth surface. Therefore, factors which prevent S. mutans attachment to hydroxyapatite (HA) are of considerable interest for the prophylaxis of this infectious disease. Chitosan, a chitin derivative by N-deacetylation, is an interesting candidate in

R. Tarsi; R. A. A. Muzzarelli; C. A. Guzmàn; C. Pruzzo

1997-01-01

191

Increasing hydroxyapatite incorporation into poly(methylmethacrylate) cement increases osteoblast adhesion and response  

Microsoft Academic Search

Poly(methylmethacrylate) (PMMA) is the current standard for cement held prostheses. It forms a strong bond with the implant, but the bond between the cement and the bone is considered to be weak, with fibroblastic cells observed at the implant site, rather than direct bone contact, a contributing factor leading to implant failure. Incorporation of hydroxyapatite (HA) increases the biological response

M. J. Dalby; L. Di Silvio; E. J. Harper; W. Bonfield

2002-01-01

192

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

193

Impaction grafting with morsellised allograft and tricalcium phosphate–hydroxyapatite: incorporation within ovine metaphyseal bone defects  

Microsoft Academic Search

An ovine model was used to investigate the in vivo properties of impacted tricalcium phosphate–hydroxyapatite (TCP–HA) aggregates, varying in chemical composition (ratio of TCP to HA) and particle size distribution (8 versus 3 particle size ranges). All pellets were impacted to a standard compactive effort.Eight sheep underwent implantation of pellets in 4 metaphyseal defects in both rear limbs. Treatment groups

J. N. J. Pratt; D. J. Griffon; D. G. Dunlop; N. Smith; C. R. Howie

2002-01-01

194

Adhesion study of pulsed laser deposited hydroxyapatite coating on laser surface nitrided titanium  

Microsoft Academic Search

Hydroxyapatite (HA) coatings were fabricated by pulsed laser deposition (PLD) on commercially pure titanium which had been subjected to different types of pre-treatment. These include: (i) 60-grit SiC grinding, (ii) 320-grit SiC grinding, (iii) 1-µm diamond paste mirror-finishing, (iv) etching with Knoll solution, and (v) laser surface nitriding followed by selective etching. The HA coatings were pulsed laser deposited at

H. C. Man; K. Y. Chiu; F. T. Cheng; K. H. Wong

2009-01-01

195

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

196

Biological fixation of hydroxyapatite-coated versus grit-blasted titanium hip stems: a canine study  

Microsoft Academic Search

Background. The purpose of the study was to evaluate the influence of a proximal hydroxyapatite (HA) coating in comparison with a grit-blasted titanium surface of an anatomic hip stem in an animal model over a maximum duration of 2 years. Methods. Thirty adult dogs underwent implantation of either a proximally HA-coated or a grit-blasted anatomic titanium stem. The animals were

Anke Eckardt; Harold M. Aberman; Dan H. Cantwell; Jochen Heine

2003-01-01

197

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

Microsoft Academic Search

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

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

1999-01-01

198

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

199

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

200

Preparation of hydroxyapatite spheres with an internal cavity as a scaffold for hard tissue regeneration  

Microsoft Academic Search

Microparticulates are currently regarded as a useful matrix for the delivery of bioactive molecules and tissue cells. Herein,\\u000a hydroxyapatite (HA) spherical microparticulates with an internal cavity were produced using an oil-in-water emulsion technique.\\u000a The HA slurry in the organic solvent was formulated into spherical particles in a water bath containing a surfactant. Rapid\\u000a evaporation of the solvent helped create a

Hae-Hyoung Lee; Seok-Jung Hong; Chul-Hwan Kim; Eun-Cheol Kim; Jun-Hyeog Jang; Hong-In Shin; Hae-Won Kim

2008-01-01

201

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

202

Impact formation and microstructure characterization of thermal sprayed hydroxyapatite\\/titania composite coatings  

Microsoft Academic Search

Formation mechanism of hydroxyapatite (HA)\\/titania (TiO2) composite coating deposited by high velocity oxy-fuel (HVOF) thermal spray process was studied, and its structural characterization was conducted and elaborated in this paper. The impact theory was employed to analyze the formation procedure of the HA\\/titania composite coatings. Results revealed that the crater caused by the impact of entirely unmelted TiO2 particles on

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

2003-01-01

203

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

Microsoft Academic Search

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

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

204

PHBV\\/PLLA-based composite scaffolds containing nano-sized hydroxyapatite particles for bone tissue engineering  

Microsoft Academic Search

Composite scaffolds made of PHBV\\/PLLA blends and nano-sized hydroxyapatite (HA) particles can be useful for bone tissue engineering as different blends of PHBV with PLLA should have higher degradation rates than PHBV itself and scaffolds containing bioactive HA particles will provide desired osteoconductivity. In this investigation, composite scaffolds were produced via an emulsion freezing\\/freeze-drying process and subsequently characterised using several

N. Sultana; M. Wang

2008-01-01

205

Physicochemical and Biological Properties of Nano-hydroxyapatite-Reinforced Aliphatic Polyurethanes Membranes  

Microsoft Academic Search

Polymer nano-composite membranes, based on aliphatic biodegradable polyurethane (PU) elastomers and nano-hydroxyapatite (n-HA), were prepared by solvent casting and freeze-drying. The PU matrix was synthesized from 4,4?-dicyclohexylmethane diisocyanate (H12 MDI), poly(ethylene glycol) (PEG), castor oil (CO) and 1,4-butandiol (BDO). The n-HA\\/PU membranes were characterized by SEM, XRD, IR, TG, mechanical test and in vitro biocompatibility. The results revealed that incorporation

Haohuai Liu; Li Zhang; Jidong Li; Qin Zou; Yi Zuo; Weidong Tian; Yubao Li

2010-01-01

206

Preparation and cell–materials interactions of plasma sprayed strontium-containing hydroxyapatite coating  

Microsoft Academic Search

The use of strontium-containing hydroxyapatite (Sr-HA) as a biomaterial has been reported recently. In vitro and in vivo studies have shown that Sr-HA promotes osteoblast response and stimulates new bone formation. In order to extend its usage to major load-bearing applications, such as artificial hip replacement, it has been proposed that the material could be used in the form of

Weichang Xue; Howard L. Hosick; Amit Bandyopadhyay; Susmita Bose; Chuanxian Ding; K. D. K. Luk; K. M. C. Cheung; W. W. Lu

2007-01-01

207

Porous microsphere and its applications.  

PubMed

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

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

2013-03-15

208

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

209

Incorporation of Hydroxyapatite Sol Into Collagen Gel to Regulate the Contraction Mediated by Human Bone Marrow-Derived Stromal Cells  

Microsoft Academic Search

In this paper, hydroxyapatite (HA) sol composed of nanosized HA particles was incorporated into collagen gel to regulate cell-mediated collagen contraction. Human bone marrow derived stromal cells (hMSCs) were cultured for 37 days in gels with HA to collagen ratios of 0:1, 0.5:1, 1:1, 1.5:1, and 2:1, respectively. The contraction of gels was evaluated by measuring diameter change with incubation

Yang Liu; David J. Williams

2010-01-01

210

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

211

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

PubMed Central

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

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

2012-01-01

212

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

213

Increased osteoblast adhesion on nanoparticulate crystalline hydroxyapatite functionalized with KRSR  

PubMed Central

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

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

2006-01-01

214

Nanocrystalline hydroxyapatite/titania coatings on titanium improves osteoblast adhesion.  

PubMed

Bulk hydroxyapatite (HA) and titania have been used to improve the osseointegration of orthopedic implants. For this reason, composites of HA and titania have been receiving increased attention in orthopedics as novel coating materials. The objective of this in vitro study was to produce nanophase (i.e., materials with grain size less than 100 nm) HA/titania coatings on titanium. The adhesion of bone forming cells (osteoblasts) on the composite coatings were also assessed and compared with single-phase nanotitania and nano-HA titanium coatings. Nanocrystalline HA powders were synthesized through wet chemistry and hydrothermal treatments at 200 degrees C. Nanocrystalline titania powders obtained commercially were mixed with the nanocrystalline HA powders at various weight ratios. The mixed powders were then deposited on titanium utilizing a room-temperature coating process called IonTite. The results of the present study showed that such coatings maintained the chemistry and crystallite size of the original HA and titania powders. Moreover, osteoblasts adherent on single-phase nanotitania coatings were well-spread whereas they became more round and extended distinct filopodia on the composite and single-phase HA coatings. Interestingly, the number of osteoblasts adherent on the nanotitania/HA composite coatings at weight ratios of 2/1 and 1/2 were significantly greater compared with single-phase nanotitania coatings, currently-used plasma-sprayed HA coatings, and uncoated titanium. These findings suggest that nanotitania/HA coatings on titanium should be further studied for improved orthopedic applications. PMID:17607739

Sato, Michiko; Aslani, Arash; Sambito, Marisa A; Kalkhoran, Nader M; Slamovich, Elliott B; Webster, Thomas J

2008-01-01

215

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

216

Barium Vanadate Microspheres  

NASA Astrophysics Data System (ADS)

It has been found that many glass powders can form micro- or nanospheres when heated in a flame or by a laser. Much of the research in this area of microspheres has concentrated on making hollow spheres, called microballoons, of silica and borosilicate glasses. Our aim was to create highly porous barium vanadate microspheres for possible future applications in material storage. The surface area of porous spheres would provide a greater amount of bonding surface area for dopants than hollow spheres. Barium vanadate glass with a molar fraction of 0.4 to 0.6 barium oxide was used because this glass is stable and has a low Tg. Size distributions of the spheres were quantified and the extent of sphere formation and porosity was examined using a scanning electron microscope. The size of spheres formed is affected by powder size, dropping method, and flame position. The porosity of the microspheres is affected by flame temperature, time spent in flame, and the material onto which the spheres fall. The greatest porosity was achieved by first heating the glass powder at a low temperature and then immediately sending it through the flames of two MAPP gas torches at approximately 2100^oC onto a metal sheet.

Yosinski, Shari; Tweeton, Landon; Feller, Steve; Affatigato, Mario

2009-11-01

217

Peptide Probe for Crystalline Hydroxyapatite: In Situ Detection of Biomineralization  

NASA Astrophysics Data System (ADS)

While cells template mineralization in vitro and in vivo, specific detection strategies that impart chemical and structural information on this process have proven elusive. Recently we have developed an in situ based peptide probe via phage display methods that is specific to crystalline hydroxyapatite (HA). We are using this in fluorescence based assays to characterize mineralization. One application being explored is the screening of tissue engineering scaffolds for their ability to support osteogenesis. Specifically, osteoblasts are being cultured in hydrogel scaffolds possessing property gradients to provide a test bed for the HA peptide probe. Hydrogel properties that support osteogenesis and HA deposition will be identified using the probe to demonstrate its utility in optimizing design of tissue scaffolds.

Cicerone, Marcus; Becker, Matthew; Simon, Carl; Chatterjee, Kaushik

2009-03-01

218

Recombinant human-like collagen directed growth of hydroxyapatite nanocrystals  

NASA Astrophysics Data System (ADS)

Bones are biocomposites with hierarchical structure that require controlled mineral deposition during their self-assembly to form tissues with unique mechanical properties. Type I collagen proteins, acidic extracellular matrix proteins, play a critical role in mineral formation and many researches on artificial bones have been made inspired by nature using type I collagen derived from animal tissues. Here we report that recombinant human-like type I collagen, an acidic protein, can direct growth of hydroxyapatite (HA) nanocrystals in vitro in the form of self-assembly of nano-fibrils of mineralized collagen resembling extracellular matrix. The mineralized collagen fibrils aligned parallel to each other to form mineralized collagen fibers. HA nanocrystals grew on the surface of these collagen fibrils with the c-axis of nanocrystals of HA orienting along the longitudinal axis of the fibrils. These artificial analogs of bone have a potential clinical application in bone repair.

Zhai, Y.; Cui, F. Z.

2006-05-01

219

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

220

Sr-substituted hydroxyapatites for osteoporotic bone replacement.  

PubMed

Porous apatites, which during resorption can release in situ Sr ions, were prepared to associate an anti-osteoporotic action with the peculiar features of the inorganic phase constituting the bone. Sr-substituted hydroxyapatite (SrHA) powder was directly synthesized using the classical neutralization route, but including Sr ions, and characterized. The higher solubility of SrHA granules of 400-600 microm size, potentially usable as a bone filler, was assessed compared with that of analogous stoichiometric HA granules. The Sr released in synthetic body fluid became constant after 1 week. The Ca release is improved for SrHA compared with stoichiometric HA, due to the higher solubility of the first material. Porous scaffolds with micro-macro interconnected porosity, which mimic the morphology of the spongy bone, were prepared by the impregnation of cellulose sponges with suspensions of the powder and a specific sintering process. A compressive strength of 4.52+/-1.40 MPa was obtained for SrHA scaffolds characterized with 45 vol.% of porosity. Promising biomedical applications, such as resorbable bone filler or bone substitute releasing in situ Sr ions for a prolonged time, can be hypothesized for the SrHA materials when pathologies related with Sr deficiency are present. PMID:17618844

Landi, Elena; Tampieri, Anna; Celotti, Giancarlo; Sprio, Simone; Sandri, Monica; Logroscino, Giandomenico

2007-06-19

221

A functionally graded titanium/hydroxyapatite film obtained by sputtering.  

PubMed

A functionally graded film of titanium/hydroxyapatite (HA) was prepared on a titanium substrate using a radio frequency magnetron sputtering. The ratio of titanium to HA was controlled by moving the target shutter. The film was composed of five layers, with overall film thickness of 1 microm. The HA was concentrated close to the surface, while the titanium concentration increased with proximity to the substrate. The bonding strength between the film and the substrate was 15.2 MPa in a pull-out test and the critical load from a scratch test was 58.85 mN. The corresponding values of a pure HA sputtered film were 8.0 MPa and 38.47 mN, respectively. The bonding strength of a pure HA plasma spray coating was 10.4 MPa in the pull-out test. The graded film and the pure HA film were sputter-coated to a thickness of 1 microm on titanium columns (10 mm in length and 4 mm in diameter). These columns were implanted in diaphyses of the femora of six adult dogs and a push-out test was carried out after 2, 4, and 12 weeks. After 12 weeks, the push-out strengths of the graded film, the pure HA film and the non-coated columns were 3.7, 3.5, and 1.0 MPa. PMID:15348621

Ozeki, Kazuhide; Yuhta, Toshio; Fukui, Yasuhiro; Aoki, Hideki; Nishimura, Ikuya

2002-03-01

222

A simple and rapid method to graft hydroxyapatite on carbon nanotubes.  

PubMed

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 H(2)SO(4) and HNO(3). 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 Ca(2+) and PO(4) (3-) 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. PMID:21927541

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

2011-10-10

223

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

224

The nano-scratch behavior of biocompatible hydroxyapatite reinforced with aluminum oxide and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) reinforced with sub-micrometer Al2O3 and carbon nanotubes (CNTs) has been synthesized as a coating on the Ti-6Al-4V substrate via plasma spraying. The addition of Al2O3 and CNTs to HA has shown improvement in the hardness and elastic modulus by 65% and 50%, respectively, when compared to HA. Consequently, HA-Al2O3-CNT coatings have been nano-scratched to understand their wear performance. Reinforcement of HA by Al2O3 shows a decrease in the wear volume by more than 13 times, whereas HA-Al2O3-CNT coating demonstrated further wear volume reduction of five times compared to that of HA-Al2O3 coating.

Balani, Kantesh; Lahiri, Debrupa; Keshri, Anup K.; Bakshi, S. R.; Tercero, Jorge E.; Agarwal, Arvind

2009-09-01

225

Nanocrystalline hydroxyapatite and zinc-doped hydroxyapatite as carrier material for controlled delivery of ciprofloxacin  

Microsoft Academic Search

In bone disorders infections are common. The concentration of majority of antibiotics is very low in the bone tissue. A high\\u000a local dose can be obtained from the ciprofloxacin-loaded hydroxyapatite nanoparticles. The present study is aimed at developing\\u000a the use of hydroxyapatite and zinc-doped hydroxyapatite nanoparticles as a carrier for ciprofloxacin drug delivery system.\\u000a The ciprofloxacin-loaded hydroxyapatite and zinc-doped hydroxyapatite

G. Devanand Venkatasubbu; S. Ramasamy; V. Ramakrishnan; J. Kumar

226

High-temperature hydroxyapatite-titanium interaction  

Microsoft Academic Search

Hydroxyapatite-titanium interaction has been studied in the temperature range 700 to 1200°C with a view to designing biocompatible\\u000a dispersion-hardened hydroxyapatite-matrix materials for bone implants. The sequence of phase transformations in hydroxyapatite-titanium\\u000a powder mixtures during heating in air has been identified using IR spectroscopy, differential thermal analysis, and X-ray\\u000a diffraction. It is shown that hydroxyapatite decomposition can be inhibited via heat

A. A. Egorov; V. V. Smirnov; L. I. Shvorneva; S. V. Kutsev; S. M. Barinov

2010-01-01

227

Corrosion behavior of plasma sprayed hydroxyapatite and hydroxyapatite-silicon oxide coatings on AISI 304 for biomedical application  

NASA Astrophysics Data System (ADS)

The objective of this study is to evaluate corrosion resistance of plasma sprayed hydroxyapatite (HA) and HAsbnd silicon oxide (SiO2) coated AISI 304 substrates. In HAsbnd SiO2 coatings, 10 wt% SiO2 and 20 wt% SiO2 was mixed with HA. The feedstock and coatings were characterized by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy. The corrosion resistance was determined for the uncoated and coated samples. The corrosion resistance of the AISI 304 was found more after the deposition of the HAsbnd SiO2 coatings rather than HA coating and uncoated. All the coatings were crack free after 24 h dipping in Ringer's solution for electrochemical corrosion testing.

Singh, Gurpreet; Singh, Hazoor; Sidhu, Buta Singh

2013-11-01

228

Fabrication and characterization of sol–gel derived hydroxyapatite\\/zirconia composite nanopowders with various yttria contents  

Microsoft Academic Search

Homogeneous composite nanopowders of hydroxyapatite\\/30wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8mol% Y2O3 (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared

S. Salehi; M. H. Fathi

2010-01-01

229

Silicon Microspheres for Terahertz Communication  

NASA Astrophysics Data System (ADS)

Silicon microspheres can be used for free space optical communication applications in the THz communication bands. The morphology dependent resonances of the microsphere have quality factors of 100000, which provide the narrow linewidths for high resolution filtering, Raman lasers, modulators, and CMOS compatible detectors.

Akatlar, Onur; Serpengüzel, Ali

2007-04-01

230

The influence of plasma technology coupled to chemical grafting on the cell growth compliance of 3D hydroxyapatite scaffolds.  

PubMed

The development of advanced materials with biomimetic features in order to elicit desired biological responses and to guarantee tissue biocompatibility is recently gaining attention for tissue engineering applications. Bioceramics, such as hydroxyapatite-based biomaterials are now used in a number of different applications throughout the body, covering all areas of the skeleton, due to their biological and chemical similarity to the inorganic phases of bones. When bioactive sintered hydroxyapatite (HA) is desired, biomolecular modification of these materials is needed. In the present work, we investigated the influence of plasma surface modification coupled to chemical grafting on the cell growth compliance of HA 3D scaffolds. PMID:22875605

Russo, Laura; Zanini, Stefano; Giannoni, Paolo; Landi, Elena; Villa, Anna; Sandri, Monica; Riccardi, Claudia; Quarto, Rodolfo; Doglia, Silvia M; Nicotra, Francesco; Cipolla, Laura

2012-08-09

231

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

232

Biodegradable microspheres in drug delivery.  

PubMed

General aspects of biodegradable microspheres prepared from natural and synthesized polymers used in drug delivery systems are reviewed first from various viewpoints: characteristics of biodegradable polymers (physicochemical properties, bioerosion mechanism, biocompatibility), preparation method for the microspheres, drug release from parenteral products and briefly nonparenteral products. The relationship between release pattern and pharmacological activity of therapeutic peptides and proteins and rational controlled release design are also discussed. In the latter half, successful sustained release depot formulations of peptides, leuprorelin acetate, and thyrotropin-releasing hormone (TRH), utilizing poly(lactic acid) (PLA) and poly(lactic/glycolic acid) (PLGA) microspheres are reviewed with respect to preparation, drug release, biocompatibility, pharmacological effects, and results of clinical studies. Thereafter, studies on antitumor therapy by chemoembolization using PLGA microspheres containing an angiogenesis inhibitor (TNP-470) are described as an example of targeted drug delivery with biodegradable microspheres. PMID:8521523

Okada, H; Toguchi, H

1995-01-01

233

Intrinsic magnetism and hyperthermia in bioactive Fe-doped hydroxyapatite.  

PubMed

The use of magnetic activation has been proposed to answer the growing need for assisted bone and vascular remodeling during template/scaffold regeneration. With this in mind, a synthesis procedure was developed to prepare bioactive (Fe2+/Fe3+)-doped hydroxyapatite (Fe-HA), endowed with superparamagnetic-like properties. This new class of magnetic hydroxyapatites can be potentially employed to develop new magnetic ceramic scaffolds with enhanced regenerative properties for bone surgery; in addition, magnetic Fe-HA can find application in anticancer therapies, to replace the widely used magnetic iron oxide nanoparticles, whose long-term cytotoxicity was recently found to reach harmful levels. An extensive physicochemical, microstructural and magnetic characterization was performed on the obtained Fe-HA powders, and demonstrated that the simultaneous addition of Fe2+ and Fe3+ ions during apatite nucleation under controlled synthesis conditions induces intrinsic magnetization in the final product, minimizing the formation of magnetite as secondary phase. This result potentially opens new perspectives for biodevices aimed at bone regeneration and for anti-cancer therapies based on hyperthermia. PMID:22005331

Tampieri, Anna; D'Alessandro, Teresa; Sandri, Monica; Sprio, Simone; Landi, Elena; Bertinetti, Luca; Panseri, Silvia; Pepponi, Giancarlo; Goettlicher, Joerg; Bañobre-López, Manuel; Rivas, Jose

2011-09-29

234

Ion adsorption behaviour of hydroxyapatite with different crystallinities.  

PubMed

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

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

2009-07-07

235

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

PubMed

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

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

2010-06-16

236

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

237

Evaluating Titanium Alloys Bioactivity in Terms of Hydroxyapatite (HA) Forming Capability  

Microsoft Academic Search

Titanium and its alloys are well-established biomaterials, successfully used in the biomedical domain, for the fabrication of implants due to their good mechanical properties combined with their biocompatibility (1-2). The bone-forming bioactivity of TiAlNb is associated to their chemical and structural properties, including composition, porosity, specific surface area and particle size. For better osteointegration in the body of a biometallic

ELENA ALDEA; NICOLETA BADEA; IOANA DEMETRESCU

238

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

2013-01-28

239

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

240

Influence of hydroxyapatite on the corrosion resistance of the Ti-13Nb-13Zr alloy.  

PubMed

Electrochemical analyses on the biocompatible alloy Ti-13Nb-13Zr wt% in an electrolyte simulating physiological medium (PBS solution) are reported. Hydroxyapatite (HA) films were obtained on the alloy by electrodeposition at constant cathodic current. Samples of the alloy covered with an anodic-oxide film or an anodic-oxide/HA film were analyzed by open circuit potential and electrochemical impedance spectroscopy measurements during 180 days in the PBS electrolyte. Analyses of the open-circuit potential (E (oc)) values indicated that the oxide/HA film presents better protection characteristics than the oxide only. This behavior was corroborated by the higher film resistances obtained from impedance data, indicating that, besides improving the alloy osteointegration, the hydroxyapatite film may also increase the corrosion protection of the biomaterial. PMID:19083081

Duarte, Laís T; Biaggio, Sonia R; Rocha-Filho, Romeu C; Bocchi, Nerilso

2008-12-13

241

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

242

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

2008-11-25

243

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

244

Osteoconductive hydroxyapatite coated PEEK for spinal fusion surgery  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

245

Role of osteopontin in modulation of hydroxyapatite formation.  

PubMed

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

Hunter, Graeme K

2013-01-19

246

Addressing processing problems associated with plasma spraying of hydroxyapatite coatings.  

PubMed

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

Cheang, P; Khor, K A

1996-03-01

247

Electrophoretic deposition of composite hydroxyapatite-silica-chitosan coatings  

SciTech Connect

Electrophoretic deposition (EPD) method has been developed for the fabrication of nanocomposite silica-chitosan coatings. Cathodic deposits were obtained on various conductive substrates using suspensions of silica nanoparticles in a mixed ethanol-water solvent, containing dissolved chitosan. Co-deposition of silica and hydroxyapatite (HA) nanoparticles resulted in the fabrication of HA-silica-chitosan coatings. The deposition yield has been studied at a constant voltage mode at various deposition durations. The method enabled the formation of coatings of different thickness in the range of up to 100 {mu}m. Deposit composition, microstructure and porosity can be varied by variation of HA and silica concentration in the suspensions. It was demonstrated that EPD can be used for the fabrication of HA-silica-chitosan coatings of graded composition and laminates. The method enabled the deposition of coatings containing layers of silica-chitosan and HA-chitosan nanocomposites using suspensions with different HA and silica content. Obtained coatings were studied by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The mechanism of deposition is discussed.

Grandfield, K. [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7 (Canada); Zhitomirsky, I. [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L7 (Canada)], E-mail: zhitom@mcmaster.ca

2008-01-15

248

Weibull modulus and fracture strength of highly porous hydroxyapatite.  

PubMed

Porous hydroxyapatite (HA) is used in a variety of applications including biomedical materials such as engineered bone materials and microbe filters. Despite the utility of the Weibull modulus, m, as a gauge of the mechanical reliability of brittle solids, there have been very few studies of m for porous HA. A recent study of porous HA that included the current authors (Fan, X., Case, E.D., Ren, F., Shu, Y., Baumann, M.J., 2012a. Journal of the Mechanical Behavior of Biomedical Materials. 8, 21-36) showed increases in m for porosity, P, approaching PG, the porosity of the green (unfired) specimen. In this paper, 18 groups of highly porous HA specimens (12 groups fabricated in this study and 6 groups from Fan et al., 2012a) were analyzed with P values from 0.59 to 0.62, where PG=0.62. The partially sintered HA specimens were fractured in biaxial flexure using a ring-on-ring test fixture. The fracture strength decreased monotonically with decreasing sintering temperature, Tsinter, from 4.8MPa for specimens sintered at 1025°C-0.66MPa for specimens sintered at 350°C. However, the Weibull modulus remained surprisingly high, ranging from 6.6 to 15.5. In comparison, for HA specimens with intermediate values of P, from about 0.1-0.55, the Weibull modulus tended to be lower (ranging from about 4 to 11) than the highly porous specimens included in this study. PMID:23478051

Fan, X; Case, E D; Gheorghita, I; Baumann, M J

2013-02-13

249

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

250

Enhanced mechanical strength and biocompatibility of electrospun polycaprolactone-gelatin scaffold with surface deposited nano-hydroxyapatite.  

PubMed

In this study for the first time, we compared physico-chemical and biological properties of polycaprolactone-gelatin-hydroxyapatite scaffolds of two types: one in which the nano-hydroxyapatite (n-HA) was deposited on the surface of electrospun polycaprolactone-gelatin (PCG) fibers via alternate soaking process (PCG-HAAS) and other in which hydroxyapatite (HA) powders were blended in electrospinning solution of PCG (PCG-HAB). The microstructure of fibers was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which showed n-HA particles on the surface of the PCG-HAAS scaffold and embedded HA particles in the interior of the PCG-HAB fibers. PCG-HAAS fibers exhibited the better Young's moduli and tensile strength as compared to PCG-HAB fibers. Biological properties such as cell proliferation, cell attachment and alkaline phosphatase activity (ALP) were determined by growing human osteosarcoma cells (MG-63) over the scaffolds. Cell proliferation and confocal results clearly indicated that the presence of hydroxyapatite on the surface of the PCG-HAAS scaffold promoted better cellular adhesion and proliferation as compared to PCG-HAB scaffold. ALP activity was also observed better in alternate soaked PCG scaffold as compared to PCG-HAB scaffold. Mechanical strength and biological properties clearly demonstrate that surface deposited HA scaffold prepared by alternate soaking method may find application in bone tissue engineering. PMID:23498272

Jaiswal, A K; Chhabra, H; Soni, V P; Bellare, J R

2013-02-09

251

Synthesis of fluorapatite-hydroxyapatite nanoparticles and toxicity investigations.  

PubMed

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

Montazeri, N; Jahandideh, R; Biazar, Esmaeil

2011-01-28

252

Calcium Deficient Hydroxyapatite for Medical Application Prepared by Hydrothermal Method  

NASA Astrophysics Data System (ADS)

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

Ioku, Koji; Kamitakahara, Masanobu; Ikeda, Tohru

2010-11-01

253

Measurement of extent of bone ongrowth and hydroxyapatite absorption in retrieved acetabular cups  

Microsoft Academic Search

Background  To understand why hydroxyapatite (HA)-coated acetabular cups did not produce satisfactory results, we measured the extent\\u000a of bone ongrowth and HA absorption of the retrieved cups.\\u000a \\u000a \\u000a \\u000a Methods  Between March 1992 and June 1998, a total of 289 patients underwent total hip arthroplasty with an HA-coated ABG (Anatomical\\u000a Benoist Giraud) prosthesis in our hospital. We revised 71 cups in our hospital, 43

Young-Yool Chung; Jin Kim; Chae Hyun Lim; Ki-Soo Kim; Yeon Soo Lee

2008-01-01

254

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

255

Modulation of nano-hydroxyapatite size via formation on chitosan–gelatin network film in situ  

Microsoft Academic Search

Natural bone is actually an inorganic\\/organic composite mainly make up of nano-hydroxyapatite (Ca10(PO4)6(OH)2, nHA) and collagen fibers. It is most important to form nHA\\/polymer composites in order to provide good biocompatibility and integration with bone tissue. In this work, nHA was formed in-situ on the surface of chitosan–gelatin (CG) network films in tris-buffer solution containing Ca(NO3)2-Na3PO4. The interaction between CG

Junjie Li; YiPing Chen; Yuji Yin; Fanglian Yao; Kangde Yao

2007-01-01

256

Nano-hydroxyapatite surfaces grafted with electroactive aniline tetramers for bone-tissue engineering.  

PubMed

An electroactive amino/carboxyl-capped aniline tetramer (AT) is covalently grafted to the surface of hydroxyapatite (HA) nanoparticles to generate novel electroactive HA-AT nanoparticles. The amount of AT ranges from 16.5 to 34.0?wt% and is characterized by thermogravimetric analysis (TGA). The HA-AT nanoparticles are characterized by Fourier transform IR (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and scanning electron microscopy (SEM). For the excellent electroactivity of HA-AT, the mixture of HA-AT and PLA shows much better adhesion ability and proliferation ability than that of HA and a PLA matrix. At a 15?wt% AT grafting amount, the matrix shows the best biocompatibility. PMID:23378280

Liu, Yadong; Cui, Haitao; Zhuang, Xiuli; Zhang, Peibiao; Cui, Yi; Wang, Xianhong; Wei, Yen; Chen, Xuesi

2013-02-01

257

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

PubMed

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

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

2012-04-17

258

Hydroxyapatite coating of cellulose sponges attracts bone-marrow-derived stem cells in rat subcutaneous tissue  

PubMed Central

The presence of bone-marrow-derived stem cells was investigated in a wound-healing model where subcutaneously implanted cellulose sponges were used to induce granulation tissue formation. When cellulose was coated with hydroxyapatite (HA), the sponges attracted circulating haemopoietic and mesenchymal progenitor cells more efficiently than uncoated cellulose. We hypothesized that the giant cells/macrophages of HA-coated sponges recognize HA as foreign material, phagocyte or hydrolyse it and release calcium ions, which are recognized by the calcium-sensing receptors (CaRs) expressed on many cells including haemopoietic progenitors. Our results showed, indeed, that the HA-coated sponges contained more CaR-positive cells than untreated sponges. The stem cells are, most probably, responsible for the richly vascularized granulation tissue formed in HA-coated sponges. This cell-guiding property of HA-coated cellulose might be useful in clinical situations involving impaired wound repair.

Tommila, Miretta; Jokilammi, Anne; Terho, Perttu; Wilson, Timothy; Penttinen, Risto; Ekholm, Erika

2009-01-01

259

Aligned PLGA/HA nanofibrous nanocomposite scaffolds for bone tissue engineering.  

PubMed

Aligned nanofibrous scaffolds based on poly(d,l-lactide-co-glycolide) (PLGA) and nano-hydroxyapatite (nano-HA) were synthesized by electrospinning for bone tissue engineering. Morphological characterization using scanning electron microscopy showed that the addition of different amounts of nano-HA (1, 5, 10 and 20wt.%) increased the average fiber diameter from 300nm (neat PLGA) to 700nm (20% nano-HA). At higher concentrations (>or=10%), agglomeration of HA was observed and this had a marked effect at 20% concentration whereby the presence of nano-HA resulted in fiber breaking. Thermal characterization showed that the fast processing of electrospinning locked in the amorphous character of PLGA; this resulted in a decrease in the glass transition temperature of the scaffolds. Furthermore, an increase in the glass transition temperature was observed with increasing nano-HA concentration. The dynamic mechanical behavior of the scaffolds reflected the morphological observation, whereby nano-HA acted as reinforcements at lower concentrations (1% and 5%) but acted as defects at higher concentrations (10% and 20%). The storage modulus value of the scaffolds increased from 441MPa for neat PLGA to 724MPa for 5% nano-HA; however, further increasing the concentration leads to a decrease in storage modulus, to 371MPa for 20% nano-HA. Degradation characteristics showed that hydrophilic nano-HA influenced phosphate-buffered saline uptake and mass loss. The mechanical behavior showed a sinusoidal trend with a slight decrease in modulus by week 1 due to the plasticizing effect of the medium followed by an increase due to shrinkage, and a subsequent drop by week 6 due to degradation. PMID:18778977

Jose, Moncy V; Thomas, Vinoy; Johnson, Kalonda T; Dean, Derrick R; Nyairo, Elijah

2008-07-31

260

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

261

Microstructure and properties of plasma-sprayed bio-coatings on a low-modulus titanium alloy from milled HA\\/Ti powders  

Microsoft Academic Search

New composite hydroxyapatite\\/titanium (HA\\/Ti) coatings were fabricated by plasma spraying on Ti–24Nb–4Zr–7.9Sn alloy from milled precursor powders. The microstructures, mechanical properties and apatite-induction abilities of the coatings were investigated, and the influences of the initial HA\\/Ti ratios on microstructure and properties were highlighted. XRD, SEM and TEM were used to analyze the microstructures of the coatings. The micro-hardness and elastic

G. Zhao; L. Xia; G. Wen; L. Song; X. Wang; K. Wu

262

The release properties of silver ions from Ag-nHA\\/TiO2\\/PA66 antimicrobial composite scaffolds  

Microsoft Academic Search

Implant-associated bacterial infection can jeopardize the clinical success of implants and result in loss of supporting bone. The purpose of this study was to develop a novel porous scaffold with long-term antibacterial activity for bone repair or regeneration. Porous nano-hydroxyapatite\\/titania\\/polyamide66 scaffolds containing different amounts of silver ions (Ag-nHA\\/TiO2\\/PA66) were prepared by a phase inversion technique. The release of silver ions

Xia Wu; Jidong Li; Li Wang; Di Huang; Yi Zuo; Yubao Li

2010-01-01

263

Characterization of dicalcium phosphate dihydrate cements prepared using a novel hydroxyapatite-based formulation.  

PubMed

Dicalcium phosphate dihydrate (DCPD) cements are typically prepared using beta-tricalcium phosphate (beta-TCP) as the base component. However, hydroxyapatite (HA) is an interesting alternative because of its potential for reducing cement acidity, as well as modulating cement properties via ionic substitutions. In the present study, we have characterized DCPD cements prepared with a novel formulation based on monocalcium phosphate monohydrate (MCPM) and HA. Cements were prepared using a 4:1 MCPM:HA molar ratio. The reactivity of HA in this system was verified by showing DCPD formation using poorly crystalline HA, as well as highly crystalline HA. Evaluation of cements prepared with poorly crystalline HA revealed that setting occurs rapidly in the MCPM/HA system, and that the use of a setting regulator is necessary to maintain workability of the cement paste. Compressive testing showed that MCPM/HA cements have strengths comparable to what has previously been published for DCPD cements. However, preliminary in vitro analysis of cement degradation revealed that conversion of DCPD to HA may occur much more rapidly in the MCPM/HA system compared to cements prepared with beta-TCP. Future studies should investigate this property further, as it could have important implications for the use of HA-based DCPD cement formulations. PMID:19349655

Alge, Daniel L; Santa Cruz, Grace; Goebel, W Scott; Chu, Tien-Min Gabriel

2009-04-06

264

Synthesis of hydroxyapatite from eggshells  

Microsoft Academic Search

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

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

1999-01-01

265

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

266

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

267

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

268

Biomimetic silica microspheres in biosensing.  

PubMed

Lipid vesicles spontaneously fuse and assemble into a lipid bilayer on planar or spherical silica surfaces and other substrates. The supported lipid bilayers (SLBs) maintain characteristics of biological membranes, and are thus considered to be biomembrane mimetic systems that are stable because of the underlying substrate. Examples of their shared characteristics with biomembranes include lateral fluidity, barrier formation to ions and molecules, and their ability to incorporate membrane proteins into them. Biomimetic silica microspheres consisting of SLBs on solid or porous silica microspheres have been utilized for different biosensing applications. The advantages of such biomimetic microspheres for biosensing include their increased surface area to volume ratio which improves the detection limits of analytes, and their amenability for miniaturization, multiplexing and high throughput screening. This review presents examples and formats of using such biomimetic solid or porous silica microspheres in biosensing. PMID:20336023

Chemburu, Sireesha; Fenton, Kyle; Lopez, Gabriel P; Zeineldin, Reema

2010-03-17

269

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

NASA Astrophysics Data System (ADS)

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

Rashid, Nancy Elizabeth

2000-10-01

270

The effect of RGD peptides on osseointegration of hydroxyapatite biomaterials  

PubMed Central

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

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

2008-01-01

271

Improved bactericidal activity of silver-loaded zirconium phosphate in the presence of Cl ? by combining with hydroxyapatite  

Microsoft Academic Search

Silver-loaded zirconium phosphate (AgZ) was combined with hydroxyapatite (HA) to prepare an antibacterial composite (AgZ\\/HA) with improved activity in the presence of Cl-. When Escherichia coli cells were deactivated in 154 mM NaCl, the bacterial survival ratio at 90 min for AgZ\\/HA was 3.9×10-4 compared to 1.2×10-1 for AgZ itself. Because the bactericidal activity of AgZ\\/HA decreased with increasing phosphate ion up

Motomu Nishioka; Takuro Nishimura; Akira Ookubo; Masahito Taya

2003-01-01

272

Pressureless sintering of dense hydroxyapatite-zirconia composites.  

PubMed

Hydroxyapatite (HA)-TZP (2.5 mol% Y2O3) containing 2, 5, 7.5 and 10 wt% TZP were prepared using calcium nitrate, diammonium hydrogen orthophosphate, zirconium oxychloride and yttrium nitrate. The composite powder was prepared by a reverse strike precipitation method at a pH of 10.5. The precipitates after aging and washing were calcined at 850 degrees C to yield fine crystallites of HA and TZP. TEM study of the calcined powder revealed that while HA particles had both spherical and cuboidal morphology ( approximately 50-100 nm) the TZP particles were only of spherical nature ( approximately 50 nm). X-ray analysis showed that the calcined powder of all the four composition had only HA and t-ZrO2. Uniaxially compacted samples were sintered in air in the temperature range 1,150-1,250 degrees C. High sintered density (>95% of theoretical) was obtained for composites containing 2 and 5 wt% TZP, while it was 92% for 7.5 wt% and 90% for 10 wt% TZP compositions. X-ray analysis of sintered samples shows that with 2 wt% TZP, the retained phases were only HA and t-ZrO2. However, for 5, 7.5 and 10 wt% TZP addition both TCP and CaZrO3 were also observed along with HA and t-ZrO2. Bending strength was measured by three point bending as well by diametral compression test. While in three point bending, the highest strength was 72 MPa, it was 35.5 MPa for diametral compression. The strength shows a decreasing trend at higher ZrO2 content. SEM pictures show near uniform distribution of ZrO2 in HA matrix. The reduction in sintered density at higher ZrO2 content could be related to difference in the sintering behaviour of HA and ZrO2. PMID:18219555

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

2008-01-25

273

Antibacterial nanosized silver substituted hydroxyapatite: synthesis and characterization.  

PubMed

The silver (0.5-3 at %) substituted nanosize hydroxyapatites (AgHAs) were synthesized by microwave processing. The X-ray diffraction (XRD) peaks are very broad, indicating that the AgHAs were of nanosize (30 nm). Transmission electron microscopy analysis shows needle-like morphology of AgHA, having length 60-70 nm and width 15-20 nm. The AgHA phase was stable up to 700 degrees C without any secondary phases. The antibacterial effect of AgHA against Escherichia coli and Staphylococcus aureus was observed by spread plate method, even for low concentration of silver ions (0.5%) with 1 x 10(5) cells/mL of respective bacterial culture, after a 48 h incubation period. However, some colonies of E. coli were seen with a high dose of 1 x 10(8) cells/mL after 24 h. The zone of inhibition by disc diffusion test method was found to vary with the amount of silver in the sintered AgHA pellets, for both the bacteria, after 24 h of inoculation. Osteoblast cell attachment in varying density was noticed on AgHA samples with 0.5, 1.0, and 1.5% silver substitution. However, osteoblast spreading was significantly greater on 0.5% AgHA compared to 1.0 or 1.5% substituted AgHA samples. Thus, the low amount of AgHA has a potential of minimizing the risk of bacterial contamination, without compromising the bioactivity, and is expected to display greater biological efficacy in terms of osseointegration. PMID:17031822

Rameshbabu, N; Sampath Kumar, T S; Prabhakar, T G; Sastry, V S; Murty, K V G K; Prasad Rao, K

2007-03-01

274

Effect of surface roughness of hydroxyapatite-coated titanium on the bone-implant interface shear strength.  

PubMed

We have investigated the bone-implant interface shear strength of hydroxyapatite (HA)-coated Ti-6Al-4V (HA-coating A) (roughness average, Ra = 3.4 +/- 0.5 microns) and HA-coated Ti-6Al-4V with a rougher surface (HA-coating B) (Ra = 8.4 +/- 1.8 microns). There was no significant difference between HA-coating A and HA-coating B implants with respect to the bone-implant interface shear strength as determined in push-out tests using the transcortical model in adult dogs. The bone-implant interface shear strength of bead-coated porous Ti-6Al-4V was significantly greater than that of both HA-coating A and HA-coating B implants. The failure site, as determined by scanning electron microscopy, was the coating-substrate interface, not the coating-bone interface. This indicates a need to protect the HA coating from the direct shear forces. HA coating enhances early bone growth into the porous surface of the implant. Long-term fixation should depend on bone anchoring to this porous surface. Hydroxyapatite coatings must be developed which do not obstruct the pores of the surface of the implant. PMID:7534485

Hayashi, K; Inadome, T; Tsumura, H; Nakashima, Y; Sugioka, Y

1994-11-01

275

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

276

Mechanisms of uranium interactions with hydroxyapatite: Implications for groundwater remediation  

USGS Publications Warehouse

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

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

2002-01-01

277

Vitamin D, hydroxyapatite, and calcium gluconate in treatment of cortical bone thinning in postmenopausal women with primary biliary  

Microsoft Academic Search

Women with primary bihiary cirrhosis malabsorb calcium, phosphate and vitamin D, and develop accelerated cortical bone thinning. We have assessed the value of parenteral vitamin D, oral hydroxyapatite (HA), and calcium gluconate (CG) in the treatment of cortical bone thinning in primary biliary cirrhosis. Sixty-four postmenopausal women with primary biliary cirrhosis were assigned randomly into three groups: one group receiving

Owen Epstein; Yasuhiro Kato; Robert Dick; Sheila Sherlock

278

Influence of processing parameters in the plasma spraying of hydroxyapatite\\/Ti–6Al–4V composite coatings  

Microsoft Academic Search

Biomedical implants using metals, polymers, ceramics and composites are increasingly being designed to restore body function and to facilitate healing. It is often the material design aspects of such implants that will determine the stability of the device. A hydroxyapatite (HA) coating on Ti–6Al–4V alloy is a common implant used in orthopaedics applications. HA being a bio-active material combined with

C. H. Quek; K. A. Khor; P. Cheang

1999-01-01

279

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

280

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

Microsoft Academic Search

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

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

2000-01-01

281

The effect of varying percentage hydroxyapatite in poly(ethylmethacrylate) bone cement on human osteoblast-like cells  

Microsoft Academic Search

Poly(ethylmethacrylate) (PEMA) bone cement has been developed, and the cements mechanical properties are improved by the incorporation of particulate fillers, such as hydroxyapatite (HA). In this in vitro study, human osteoblast-like (HOB) cells were used to examine the effect on cellular behavior of the addition of HA to PEMA using a plain PEMA control. Thymidine uptake (3H-TdR) and total DNA

T. N. Opara; M. J. Dalby; E. J. Harper; L. Di Silvio; W. Bonfield

2003-01-01

282

Structure, mechanical performance and electrochemical characterization of plasma sprayed SiO 2\\/Ti-reinforced hydroxyapatite biomedical coatings  

Microsoft Academic Search

For achieving an excellent bioactivity and mechanical properties, silica and titanium-reinforced hydroxyapatite composite coatings were deposited onto 304 SUS substrate by using a gas-tunnel plasma spraying system. A commercial HA powder of average size 10–45?m was blended with fused amorphous silica and titanium powders with HA:SiO2:Ti wt.% ratios of 75:15:10 respectively. The mixed powders have been plasma sprayed at various

M. F. Morks; N. F. Fahim; A. Kobayashi

2008-01-01

283

Evaluation of human osteoblastic cell response to plasma-sprayed silicon-substituted hydroxyapatite coatings over titanium substrates.  

PubMed

Silicon-substituted hydroxyapatite (Si-HA) coatings have been plasma sprayed over titanium substrates (Ti-6Al-4V) aiming to improve the bioactivity of the constructs for bone tissue repair/regeneration. X-ray diffraction analysis of the coatings has shown that, previous to the thermal deposition, no secondary phases were formed due to the incorporation of 0.8 wt % Si into HA crystal lattice. Partial decomposition of hydroxyapatite, which lead to the formation of the more soluble phases of alpha- and beta-tricalcium phosphate and calcium oxide, and increase of amorphization level only occurred following plasma spraying. Human bone marrow-derived osteoblastic cells were used to assess the in vitro biocompatibility of the constructs. Cells attached and grew well on the Si-HA coatings, putting in evidence an increased metabolic activity and alkaline phosphatase expression comparing to control, i.e., titanium substrates plasma sprayed with hydroxyapatite. Further, a trend for increased differentiation was also verified by the upregulation of osteogenesis-related genes, as well as by the augmented deposition of globular mineral deposits within established cell layers. Based on the present findings, plasma spraying of Si-HA coatings over titanium substrates demonstrates improved biological properties regarding cell proliferation and differentiation, comparing to HA coatings. This suggests that incorporation of Si into the HA lattice could enhance the biological behavior of the plasma-sprayed coating. PMID:20574971

Gomes, Pedro S; Botelho, Cláudia; Lopes, Maria A; Santos, José D; Fernandes, Maria H

2010-08-01

284

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.

285

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

PubMed

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

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

2001-10-01

286

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

287

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

288

Biodegradable HA-PLA 3-D porous scaffolds: effect of nano-sized filler content on scaffold properties.  

PubMed

Scaffolds comprising poly(lactic acid) and nano-hydroxyapatite (HA) were prepared using the solvent-casting/salt-leaching technique. NaCl was used as the leaching agent. Nano-sized HA was synthesized by a hydrothermal method at 170 degrees C and autogenous pressure. High-resolution TEM imaging revealed that the HA particles were ellipsoidal-shaped with needle-like morphologies. The particles had an average size of approximately 25 nm in width and 150 nm in length with aspect ratios ranging from 6 to 8. As the HA content increased in the scaffold from 0 to 50 wt%, the compression modulus of the scaffolds increased from 4.72+/-1.2 to 9.87+/-1.8 MPa, while the yield strength from 0.29+/-0.03 to 0.44+/-0.01 MPa. Such polymeric scaffolds should be suitable materials for non-load sharing tissue-engineering applications. PMID:16701846

Kothapalli, Chandrasekhar R; Shaw, Montgomery T; Wei, Mei

2005-07-22

289

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

290

On the structural, mechanical, and biodegradation properties of HA/?-TCP robocast scaffolds.  

PubMed

Hydroxyapatite/?-tricalcium phosphate (HA/?-TCP) composite scaffolds have shown great potential for bone-tissue engineering applications. In this work, ceramic scaffold with different HA/?-TCP compositions (pure HA, 60HA/40?-TCP, and 20HA/80?-TCP) were fabricated by a robotic-assisted deposition (robocasting) technique using water-based hydrogel inks. A systematic study was conducted to investigate the porosity, mechanical property, and degradation of the scaffolds. Our results indicate that, at a similar volume porosity, the mechanical strength of the sintered scaffolds increased with the decreasing rod diameter. The compressive strength of the fabricated scaffolds (porosity ? 25-80 vol %) varied between ?3 and ?50 MPa, a value equal or higher than that of human cancellous bone (2-12 MPa). Although there was a slight increase of Ca and P ions in water after 5 month, no noticeable degradation of the scaffolds in SBF or water was observed. Our findings from this work indicate that composite calcium phosphate scaffolds with customer-designed chemistry and architecture may be fabricated by a robotic-assisted deposition method. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1233-1242, 2013. PMID:23650043

Houmard, Manuel; Fu, Qiang; Genet, Martin; Saiz, Eduardo; Tomsia, Antoni P

2013-05-07

291

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

PubMed

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

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

2010-09-21

292

The effect of adhesive strength of hydroxyapatite coating on the stability of hydroxyapatite-coated prostheses in vivo at the early stage of implantation  

PubMed Central

Introduction With the increase in joint revision surgery after arthroplasty, defects of hydroxyapatite (HA)-coated prostheses have been observed increasingly often. These defects adversely affect the prosthetic stability in vivo. This study has analyzed the potential effect of the adhesive strength of HA coating on the stability of HA-coated prostheses in vivo after its implantation. Material and methods Sixty experimental rabbits were divided into HA- and Ti-coated groups. HA-coated prostheses were implanted into the bilateral epicondyle of rabbits femurs. Ti-coated prostheses were implanted as control. At different time points(4, 9, and 15 weeks) after implantation, bone tissue samples were fetched out respectively for histomorphometric analysis. Push-out testing was used to detect the ultimate shear strength at the bone-prosthesis interface. Scanning electron microscope (SEM) observation and energy-dispersive X-ray spectroscopy (EDX) analysis were used to observe the changes in surface composition of the prostheses after the ultimate shear strength testing. The coating adhesive strength of two kinds of coatings were also examined by scratch testing. Results Hydroxyapatite coating has an obvious advantage in facilitating osteogenesis and its plays a critical role in the stability of prostheses. However, the ultimate shear strength of HA-coated prostheses is much lower than that of Ti-coated implants (p < 0.01). Further study has demonstrated that the stability of HA-coated prostheses in vivo is affected by the relatively low adhesive strength between coating and substrate. Conclusions Obvious advantage in facilitating osteogenesis around HA-coated prostheses is not the only factor that determines the stability of prostheses in vivo.

Duan, Yonghong; Zhu, Shu; Guo, Fei; Zhu, Jinyu; Li, Mao; Ma, Jie

2012-01-01

293

The response of osteoblasts to nanocrystalline silicon-substituted hydroxyapatite thin films  

Microsoft Academic Search

Magnetron co-sputtering has been employed to fabricate thin nanocrystalline coatings of silicon-substituted hydroxyapatite (SiHA) of different Si compositions: 0.8wt%, 2.2wt%, and 4.9wt%. A human osteoblast-like (HOB) cell model was used to study the long-term interaction between the HOB cells and coatings in vitro. Results showed that the number of cells growing on all coated titanium (Ti) samples were statistically significantly

Eng San Thian; Jie Huang; Serena M Best; Zoe H Barber; Roger A Brooks; Neil Rushton; William Bonfield

2006-01-01

294

Hydroxyapatite coating on Ti6Al4V alloy using a sol–gel derived precursor  

Microsoft Academic Search

A simple rapid-heating method was successfully developed for calcium phosphate coatings on Ti6Al4V substrates deposited by using a sol–gel derived precursor. After five repetitions of coating procedures and heat treatment at 600°C, the formation of hydroxyapatite (HA) has been confirmed by X-ray diffractometry (XRD) analyses and the substrate material was found to be slightly oxidized. The residual organics, as revealed

Ming-Fa Hsieh; Li-Hsiang Perng; Tsung-Shune Chin

2002-01-01

295

Recent Developments in Suspension Plasma Sprayed Titanium Oxide and Hydroxyapatite Coatings  

Microsoft Academic Search

The paper aims at reviewing of the recent studies related to the development of suspension plasma sprayed TiO2 and Ca5(PO4)3OH (hydroxyapatite, HA) coatings as well as their multilayer composites obtained onto stainless steel, titanium and aluminum\\u000a substrates. The total thickness of the coatings was in the range 10 to 150 ?m. The suspensions on the base of distilled water,\\u000a ethanol and

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

2010-01-01

296

Interfacial behaviour of strontium-containing hydroxyapatite cement with cancellous and cortical bone  

Microsoft Academic Search

The bone-bonding behaviors of various biomaterials have been extensively investigated. However, the precise mechanisms of bone bonding have not yet been clarified, and the differences in interfacial behaviors of biomaterial bonding with cancellous bone and cortical bone have not yet been understood. In this study, strontium-containing hydroxyapatite (Sr-HA) cement, in which 10% calcium ions were substituted by strontium, was performed

G. X. Ni; W. W. Lu; B. Xu; K. Y. Chiu; C. Yang; Z. Y. Li; W. M. Lam; K. D. K. Luk

2006-01-01

297

Functionally graded bioactive coatings of hydroxyapatite\\/titanium oxide composite system  

Microsoft Academic Search

Hydroxyapatite powder (P81B, HA, Plasma Biotal, UK) was mixed with titanium oxide (TiO2) in different weight percentages for producing functionally graded bioactive coatings. Composite coatings were made on Ti6Al4V metal substrate. A functionally graded coating was obtained by coating titanium oxide (TiO2) powders of known particle size as the first layer, which was sintered at 900 °C for a few

R Roop Kumar; M Wang

2002-01-01

298

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

299

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

300

Electrodeposition of porous hydroxyapatite/calcium silicate composite coating on titanium for biomedical applications  

NASA Astrophysics Data System (ADS)

A novel method of electrolytic porous hydroxyapatite/calcium silicate (HA/CaSiO3) composite coating was conducted on pure titanium in a mixed solution of nano-SiO2, Ca(NO3)2 and NH4H2PO4. SEM observation showed that the composite layer was porous, thereby providing abundant sites for the osteoblast adhesion. XRD results showed that the composite coating was mainly composed of HA and CaSiO3. Bond strength testing exhibited that HA-CaSiO3/Ti had higher bond strength than HA/Ti. The HA/CaSiO3 coating was more corrosion resistant than the HA coating based on the polarization tests. In vitro cell experiments demonstrated that both the HA and HA/CaSiO3 coatings showed better cell response than the bared titanium. In addition, the proliferation of MC3T3-E1 osteoblast cells grown on the HA/CaSiO3 coating were remarkably higher than those on the bared Ti and pure HA coating.

Huang, Yong; Han, Shuguang; Pang, Xiaofeng; Ding, Qionqion; Yan, Yajing

2013-04-01

301

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

PubMed

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

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

2010-07-01

302

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

303

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

304

Efficiency of hyaluronic acid (HA) sperm selection  

Microsoft Academic Search

Purpose  Hyaluronic Acid (HA) has a role as “physiologic selector” for spermatozoa prior to intracytoplasmic sperm injection (ICSI).\\u000a The objective of this study is to analyze the results achievable by the introduction of a routine HA-ICSI programme.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  We retrospectively observed 293 couples treated with HA-ICSI versus 86 couples treated with conventional PVP-ICSI (historical\\u000a control group). ICSI was performed on a limited

Lodovico Parmegiani; Graciela Estela Cognigni; Walter Ciampaglia; Patrizia Pocognoli; Francesca Marchi; Marco Filicori

2010-01-01

305

Characterization and structural analysis of zinc-substituted hydroxyapatites.  

PubMed

The substitution of Zn in hydroxyapatite (HA) crystals was examined via comprehensive characterization techniques. Nanosized HA crystals were synthesized by the wet chemical method in aqueous solutions including various amounts of Zn ions. X-ray fluorescent spectroscopy was used to examine the amount of Zn in the HA precipitates. Scanning electron microscopy and high-resolution transmission electron microscopy were employed to examine the effects of Zn on the morphology and crystal size of the precipitates. Conventional powder X-ray diffraction and the Rietveld refinement method revealed the apatite lattice parameters and phase changes with the inclusion of Zn. The results indicated that Zn ions partially substituted for Ca ions in the apatite structure. They were not simply adsorbed on the apatite surface or in the amorphous phase. The precipitates maintained the apatite phase up to a Zn:(Zn+Ca) ratio of 15-20 mol.% in the solution. Pure HA was well crystallized and the crystals had regular shapes, whereas the Zn-substituted apatite crystals became irregular and formed agglomerates. The lattice parameters, a and c, decreased at a Zn:(Zn+Ca) ratio of 10 mol.%. PMID:19446055

Ren, Fuzeng; Xin, Renlong; Ge, Xiang; Leng, Yang

2009-05-04

306

Freeze-cast hydroxyapatite scaffolds for bone tissue engineering applications.  

PubMed

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

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

2008-04-15

307

Carbon nanotube-hydroxyapatite-hemoglobin nanocomposites with high bioelectrocatalytic activity.  

PubMed

In this paper, carbon nanotubes-hydroxyapatite (MWCNTs-HA) composite were synthesized by self-assembling technique, and investigated by X-ray diffraction, scanning electron microscopy (SEM) and FT-IR spectroscopy. Hemoglobin (Hb) immobilized in MWCNTs-HA film not only retained its similarly native conformations, but also achieved the direct electron transfer. The apparent heterogeneous electron transfer rate constant (k(s)) was evaluated as (5.05+/-0.41) s(-1) according to Laviron's equation, and the surface coverage (Gamma*) was estimated as (9.25+/-0.69)x10(-10)mol cm(-2). Moreover, the Hb immobilized in MWCNTs-HA film exhibited remarkable bioelectrocatalytic activity for the electrochemical reduction of H(2)O(2). The amperometric response of the biosensor varied linearly with the H(2)O(2) concentration ranging from 0.5microM to 2microM, and the results showed a detection limit of 0.09microM. Furthermore, the Hb-immobilized MWCNTs-HA film exhibited the excellent catalytic reactivity toward trichloroacetic acid (TCA). PMID:19762287

Zhao, H Y; Xu, X X; Zhang, J X; Zheng, W; Zheng, Y F

2009-09-06

308

Adsorption/desorption of amine fluorides to hydroxyapatite.  

PubMed

This study concerned the adsorption and desorption of commercial amine fluoride (AmF) preparations to hydroxyapatite (HA). The influence of pH, ionic strength, temperature, saliva and albumin, the latter as a gingival crevicular fluid analogue, on adsorption/desorption was investigated. AmF levels were determined using a surfactant electrode. AmFs 297 and 335 were found to bind immediately and irreversibly to HA in water over a range of pH values, ionic strengths and temperatures, the amounts increasing with concentration. More monovalent AmF 335 was absorbed than divalent AmF 297. Any AmF desorbed by water from HA was at the lowest end of the minimum inhibitory concentration for oral bacteria. AmF 297 was desorbed by CaCl2, and to a lesser extent by H+, OH-, NH4+, La3+, EDTA, Triton X100 and ethanol, whereas AmF 335 was only slightly desorbed by ethanol. Preadsorption of proteins on HA had little effect on subsequent adsorption or desorption of either AmF. It is postulated that both AmF 297 and AmF 335 are inactivated by an excess of proteins in the surrounding medium, supra- or subgingivally, and not by such proteins preventing or altering the mode or rate of adsorption, or interfering with antibacterial activity, when the AmFs contact a protein-coated tooth surface. PMID:8962946

Sefton, J; Lambert, M; Wilson, M; Newman, H N

1996-01-01

309

A functional agarose-hydroxyapatite scaffold for osteochondral interface regeneration  

PubMed Central

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

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

2013-01-01

310

pH-Responsive hollow polymeric microspheres and concentric hollow silica microspheres from silica-polymer core-shell microspheres.  

PubMed

Nearly monodispersed silica-poly(methacrylic acid) (SiO 2-PMAA) core-shell microspheres were synthesized by distillation-precipitation polymerization from 3-(trimethoxysilyl)propylmethacrylate-silica (SiO 2-MPS) particle templates. SiO 2-PMAA-SiO 2 trilayer hybrid microspheres were subsequently prepared by coating of an outer layer of SiO 2 on the SiO 2-PMAA core-shell microspheres in a sol-gel process. pH-Responsive PMAA hollow microspheres with flexible (deformable) shells were obtained after selective removal of the inorganic SiO 2 core from the SiO 2-PMAA core-shell microspheres by HF etching. The pH-responsive properties of the PMAA hollow microspheres were investigated by dynamic laser scattering (DLS). On the other hand, concentric and rigid hollow silica microspheres were prepared by selective removal of the PMAA interlayer from the SiO 2-PMAA-SiO 2 trilayer hybrid microspheres during calcination. The hybrid composite microspheres, pH-sensitive hollow microspheres, and concentric hollow silica microspheres were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray (EDX) analysis. PMID:18605745

Li, Guoliang; Liu, Gang; Kang, E T; Neoh, K G; Yang, Xinlin

2008-07-08

311

Silicon Microspheres for Optoelectronic Applications  

NASA Astrophysics Data System (ADS)

Having high quality factors, optical microsphere resonators are shown to be ideal circuit elements for wavelength division multiplexing. Silicon, as a common semiconductor and thus being a building block in the integrated circuits, also is a very important material with its optical properties. We have experimentally observed the shifts in resonance wavelengths of an electrically driven silicon microsphere of 500 microns in radius, in the near-IR. We have used a DFB laser at 1475nm, and applied voltages ranging from 0V to 9V to the microsphere and observed the respected shifts in the resonance wavelengths around 0.005 nm to 0.050 nm, and respective shifts in the refractive index are 10-5 to 10-4.

Ayaz, Ula? Kemal; Kurt, Adnan; Serpengüzel, Ali

2007-04-01

312

Hydroxyapatite–collagen–hyaluronic acid composite  

Microsoft Academic Search

The new composite biomaterial made from hydroxyapatite and collagen conjugated with hyaluronic acid has been studied. The structure evaluation of the composite showed more dense arrangement due to the formation of collagen–hyaluronic acid conjugate, and particles of inorganic component are closely anchored in the structure. Mechanical properties and model swelling of this composite are compared with properties of hydroxyapatite–collagen composite

D. Bakoš; M. Soldán; I. Hernández-Fuentes

1999-01-01

313

Nanocrystals of magnesium and fluoride substituted hydroxyapatite  

Microsoft Academic Search

Hydroxyapatite nanocrystals synthetized in the presence of different concentrations of magnesium and fluoride ions in solutions – 1, 5 and 10 at.% have been submitted to a structural and chemical characterization. The syntheses were carried out in the presence of low molecular weight polyacrilic acid, which has been verified to inhibit hydroxyapatite crystallization. The polyelectrolyte is adsorbed into the crystals

Enrico Bertoni; Adriana Bigi; Gianna Cojazzi; Massimo Gandolfi; Silvia Panzavolta; Norberto Roveri

1998-01-01

314

Hydroxyapatite crystal deposition causing rapidly destructive arthropathy of the hip joint  

PubMed Central

Destructive arthropathy of the hip joint can be attributed to various etiologies like rheumatoid arthritis, aseptic necrosis of the femur head, Charcot's joint, subacute septic arthritis, and tubercular arthritis. A disease that results in much rapid destruction of the hip joint and is not associated with clinical syndrome of above mentioned disease has been reported way back in 1970. However, no evidence-based study has been published to support hydroxyapatite (HA) crystals as a probable cause of rapidly destructive arthropathy of the hip joint. We report a case with microscopic and biochemical confirmation of HA crystal deposition causing destructive arthropathy of the hip joint.

Yang, Jae-Hyuk; Oh, Kwang-Jun; Pandher, Dilbans S

2011-01-01

315

Histomorphological researches on large porous hydroxyapatite cylinder tubes with polylactic acid surface coating in different nonskeletal sites in vivo.  

PubMed

Porous hydroxyapatite (HA) ceramic cylinder tubes coated with polylactic acid on the exposed surfaces were implanted in four nonskeletal sites (omentum, peritoneum, vastus lateralis, and side of femur). Six months postoperatively, proper amount of Chinese ink was injected to dye the implanting areas. Decalcified and nondecalcified sections were observed under inverted microscope. The results showed that the soft tissues around the HA cylinder tubes in peritoneum, vastus lateralis, and side of femur groups appeared visible black. Some small blacked vascular architectures were also discernible. However in omentum group, only small number of blacked vessels existed. Histological observations indicated that vascularization and ossification occurred in peritoneum, vastus lateralis, and side of femur groups. In omentum group, there was no any sign of vascularization and ossification. A conclusion could be made in this study that excepting bones and muscles, parietal peritoneum could serve as a potential spot for culturing histoengineering hydroxyapatite (HA)-polylactic acid (PLA) ceramic bone substitutes. PMID:22344718

Zhang, Cong; Huang, Peng; Weng, Jie; Zhi, Wei; Hu, Yonghe; Feng, Huaizhi; Yao, Yimin; Li, Shuo; Xia, Tian

2012-02-18

316

Preparation and characterization of NiW-nHA composite catalyst for hydrocracking.  

PubMed

The synthesis, characterization and catalytic capability of the NiW-nano-hydroxyapatite (NiW-nHA) composite were investigated in this paper. The NiW-nHA catalyst was prepared by a co-precipitation method. Then Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX) were used to analyze this material. In addition, the catalytic capacity of the NiW-nHA composite was also examined by FT-IR and gas chromatography (GC). The results of FT-IR analysis indicated that Ni, W and nHA combined closely. TEM observation revealed that this catalyst was needle shaped and the crystal retained a nanometer size. XRD data also suggested that a new phase of CaWO(4) appeared and the lattice parameters of nHA changed in this system. nHA was the carrier of metals. The rates of Ni/W-loading were 73.24% and 65.99% according to the EDX data, respectively. Furthermore, the conversion of 91.88% Jatropha oil was achieved at 360 °C and 3 MPa h(-1) over NiW-nHA catalyst. The straight chain alkanes ranging from C(15) to C(18) were the main components in the production. The yield of C(15)-C(18) alkanes was up to 83.56 wt%. The reaction pathway involved hydrocracking of the C?C bonds of these triglycerides from Jatropha oil. This paper developed a novel non-sulfided catalyst to obtain a "green biofuel" from vegetable oil. PMID:23128670

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

2012-11-06

317

Cellular proliferation, cellular viability, and biocompatibility of HA-ZnO composites.  

PubMed

One of the important issues in the development of hydroxyapatite (HA)-based biomaterials is the prosthetic infection, which limits wider use of monolithic HA despite superior cellular response. Recently, we reported that ZnO addition to HA can induce bactericidal property. It is therefore important to assess how ZnO addition influences the cytotoxicity property and cell adhesion/proliferation on HA-ZnO composite surfaces in vitro. In the above perspective, the objective of this study is to investigate the cell type and material composition dependent cellular proliferation and viability of pressureless sintered HA-ZnO composites. The combination of cell viability data as well as morphological observations of cultured human osteoblast-like SaOS2 cells and mouse fibroblast L929 cells suggests that HA-ZnO composites containing 10 Wt % or lower ZnO exhibit the ability to support cell adhesion and proliferation. Both SaOS2 and L929 cells exhibit extensive multidirectional network of actin cytoskeleton and cell flattening on the lower ZnO containing (?10 Wt %) HA-ZnO composites. The in vitro results illustrate how variation in ZnO content can influence significantly the cell vitality, as evaluated using MTT biochemical assay. Also, the critical statistical analysis reveals that ZnO addition needs to be carefully tailored to ensure good in vitro cytocompatibility. The underlying reasons for difference in biological properties are analyzed. It is suggested that surface wettability as well as dissolution of ZnO, both contribute to the observed differences in cellular viability and proliferation. PMID:22102555

Saha, Naresh; Dubey, Ashutosh K; Basu, Bikramjit

2011-11-21

318

The effects of ageing time on the microstructure and properties of mesoporous silica-hydroxyapatite nanocomposite  

NASA Astrophysics Data System (ADS)

In this study, a mesoporous silica-hydroxyapatite nanocomposite (MCM-41/HA) was synthesized via sol-gel technique as a drug delivery system. The synthesis of MCM-41/hydroxyapatite nanocomposite was carried out at room temperature. The effect of various ageing time on the nanocomposite properties was studied during synthesis process. 0, 24, 36, and 48 h aging times were chosen. Textural properties and microstructure of the nanocomposites were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), Electron Diffraction pattern (ED), and N2 adsorption-desorption. Results showed that ageing process led to HA crystals nucleation and growth on the surface of mesoporous silica. At 48 h of aging time, the surface area and total pore volume increased from 36.2 to 334 m2/g and 0.14-0.7 cm3/g, respectively. In contrast, the average pore diameter considerably decreased from 20.1 nm for (MCM-41/HA)24 to 8.39 nm for (MCM-41/HA)48. Furthermore, it was observed more homogeneous pore distribution with increasing the ageing time. In conclusion, the ageing time play an important role on textural properties of MCM-41/HA nanocomposite which could have a major effect on drug delivery properties such as molecular loading and release kinetics.

Yousefpour, Mardali; Taherian, Zahra

2013-02-01

319

Rheological, microstructural, and in vitro characterization of hybrid chitosan-polylactic acid/hydroxyapatite composites.  

PubMed

In this work, hybrid chitosan/hydroxyapatite composites material were developed and characterized. The polymer matrix was first dissolved in polylactic acid, and then hydroxyapatite (HA) was added as filler material. The effects of the added amounts of a crosslinking agent (genipin) and of the concentrations of lactic acid, and of the presence of HA powder on the evolution of rheological properties were evaluated. A significant decrease of gelation time with increasing amounts of crosslinking agent was observed, the effect being even more pronounced in the presence of HA. The chitosan matrix and the composites with a chitosan/HA weight ratio of 2/5 were characterized using microstructural analysis and in vitro tests. The formation of large pore sizes in the chitosan-based scaffolds was favored by low concentrations of lactic acid and genipin. The in vitro tests in synthetic body fluid revealed an extensive formation of an apatitic layer onto the surface of the chitosan/HA composite scaffolds crosslinked with genipin. PMID:18384164

Araújo, A B A; Lemos, A F; Ferreira, J M F

2009-03-15

320

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

PubMed Central

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

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

2012-01-01

321

Pulsed laser deposition of hydroxyapatite on titanium substrate with titania interlayer.  

PubMed

Pulsed laser deposition (PLD) has been used to deposit hydroxyapatite (HA) ceramic over titanium substrate with an interlayer of titania. PLD has been identified as a potential candidate for bioceramic coatings over metallic substrates to be used as orthopedic and dental implants because of better process control and preservation of phase identity of the coating component. However, direct deposition of hydroxyapatite on titanium at elevated temperature results in the formation of natural oxide layer along with some perovskites like calcium titanate at the interface. This leads to easy debonding of ceramic layer from the metal and thereby affecting the adhesion strength. In the present study, adherent and stable HA coating over Ti6Al4V was achieved with the help of an interlayer of titania. The interlayer was made to a submicron level and HA was deposited consecutively to a thickness of around one micron by exposing to laser ablation at a substrate temperature of 400°C. The deposited phase was identified to be phase pure HA by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma spectrometry. The mechanical behavior of coating evaluated by scratch test indicates that the adhesion strength of HA coating was improved with the presence of titania interlayer. PMID:21234791

Rajesh, P; Muraleedharan, C V; Komath, Manoj; Varma, Harikrishna

2011-01-14

322

Effect of grain size on mechanical, surface and biological properties of microwave sintered hydroxyapatite.  

PubMed

Hydroxyapatite (HA) compacts having average grain sizes of 168±0.086 nm, 1.48±0.627 ?m and 5.01±1.02 ?m are processed from synthesized HA powder by microwave sintering at varying sintering temperature for different times. Superior mechanical and biological properties are shown by nano-grain HA compacts as compared to their micron grained counterparts. Compressive strength, indentation hardness, and indentation fracture toughness are increased with the decrease in HA grain size. The highest surface energy and maximum wettability are exhibited by nano-grain HA. HA compacts are assessed for cell-material interaction by SEM, MTT and immunochemistry assays using human osteoblast cell line for 1, 5 and 11 days. MTT assays showed higher number of living cells and faster proliferation on nano-grain HA surface. Osteoblast cells on nano-grain HA surface expressed significantly higher amount of vinculin and alkaline phosphatase (ALP) protein markers for cell adhesion and differentiation respectively. This study shows the effect of grain size on physical, mechanical and in vitro biological properties of microwave sintered HA compacts. PMID:23623105

Dasgupta, Sudip; Tarafder, Solaiman; Bandyopadhyay, Amit; Bose, Susmita

2013-03-14

323

In vitro stability predictions for the bone/hydroxyapatite composite system.  

PubMed

Electroacoustic measurements of the zeta (zeta) potential as a function of pH were collected and used to probe the nature of the ionic contributions to the bond formed between synthetic hydroxyapatite (HA) and bone. HA powder and wet bone powder were dispersed into an electrolyte solution comprised of physiologic saline (0.154M NaCl), electroacoustic measurements collected, and the zeta potential calculated as a function of pH. The zeta potential and particle size then were used to calculate the stability of the composite dispersion, where stability is the ability of a particulate suspension to remain unagglomerated. The stability was used to predict the homo- (HA to HA and bone to bone) versus heterocoagulation (HA to bone) behaviors for the HA/bone system. Although single component bone and HA demonstrated stability against agglomeration, the HA/bone interaction was determined to be unstable for all pH levels tested, including pH 7.4, the normal in vivo pH. These results establish one factor responsible for the observed physicochemical bonding between bone and HA noted by many in the orthopedic community. PMID:9788504

Oppermann, D A; Crimp, M J; Bement, D M

1998-12-01

324

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

325

Densification Process of OH Controlled Hydroxyapatite Ceramics by Spark Plasma Sintering  

NASA Astrophysics Data System (ADS)

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

Kawagoe, D.; Koga, Y.; Ishida, E. H.; Ioku, K.

2006-05-01

326

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

327

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

328

Electrosprayed hydroxyapatite on polymer nanofibers to differentiate mesenchymal stem cells to osteogenesis.  

PubMed

Electrospraying of hydroxyapatite (HA) nanoparticles onto the surface of polymer nanofibers provides a potentially novel substrate for the adhesion, proliferation and differentiation of mesenchymal stem cells (MSCs) into bone tissue regeneration. HA nanoparticles (4%) were electrosprayed on the surface of electrospun polycaprolactone (PCL) nanofibers (420 ± 15 nm) for bone tissue engineering. PCL/HA nanofibers were comparatively characterized with PCL/Collagen (275 ± 56 nm) nanofibers by FT-IR analysis to confirm the presence of HA. Fabricated PCL/HA and PCL/Collagen nanofibers and TCP (control) were used for the differentiation of equine MSC into osteogenic lineages in the presence of DMEM/F12 medium supplemented with ?-glycerophosphate, ascorbic acid and dexamethasone. Cell proliferation and differentiation into an osteogenic lineage was evaluated by MTS assay, SEM observation, ALP activity, ARS staining, quantification of mineral deposition and expression of osteocalcin. Proliferation of MSCs increased significantly (P ? 0.05) up to 12% in PCL/Collagen (day 15) compared to PCL/HA nanofibrous substrate. ALP activity was increased 20% in PCL/HA by day 10 confirming the direction of osteogenic lineage from MSCs differentiation. PCL/HA stimulated an increased mineral secretion up to 26% by day 15 on ARS staining compared to PCL/Collagen nanofibers and showing cuboidal morphology by expressing osteocalcin. These results confirmed that the specifically fabricated PCL/HA composite nanofibrous substrate enhanced the differentiation of MSCs into osteogenesis. PMID:22370175

Venugopal, J; Rajeswari, R; Shayanti, M; Low, Sharon; Bongso, Ariff; Dev, V R Giri; Deepika, G; Choon, Aw Tar; Ramakrishna, S

2012-05-11

329

Initial responses of human osteoblasts to sol-gel modified titanium with hydroxyapatite and titania composition.  

PubMed

Sol-gel thin films of hydroxyapatite (HA) and titania (TiO(2)) have received a great deal of attention in the area of bioactive surface modification of titanium (Ti) implants. Sol-gel coatings were developed on Ti substrates of pure HA and TiO(2) and two composite forms, HA+10% TiO(2) and HA+20% TiO(2), and the biological properties of the coatings were evaluated. All the coating layers exhibited thin and homogeneous structures and phase-pure compositions (either HA or TiO(2)). Primary human osteoblast cells showed good attachment, spreading and proliferation on all the sol-gel coated surfaces, with enhanced cell numbers on all the coated surfaces relative to uncoated Ti control at day 1, as observed by MTT assay and scanning electron microscopy. Cell attachment rates were also enhanced on the pure HA coating relative to control Ti. The pure HA and HA+10% TiO(2) composite coating furthermore enhanced proliferation of osteoblasts at 4 days. Moreover, the gene expression level of several osteogenic markers including bone sialoprotein and osteopontin, as measured by RT-PCR at 24h, was shown to vary according to coating composition. These findings suggest that human primary bone cells show marked and rapid early functional changes in response to HA and TiO(2) sol-gel coatings on Ti. PMID:16829219

Harle, Jamie; Kim, Hae-Won; Mordan, Nicky; Knowles, Jonathan C; Salih, Vehid

2006-07-10

330

Study of the gamma irradiation effects on the PMMA/HA and PMMA/SW  

NASA Astrophysics Data System (ADS)

The behavior of the poly(methyl methacrylate) (PMMA) under the action of gamma radiation has been sufficiently studied. In this work, we present results from melt flow index (MFI), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) of PMMA composites with hydroxyapatite (HA) and seaweed residues (SW) irradiated with gamma rays at 1.08 kGy/h. Composites of PMMA/HA and PMMA/SW with 10%, 20% and 30% of the filler were prepared. The results show an increase in the MFI values with the integral dose of radiation, being consistent with chain-scission reactions. No EPR signal was observed in pure PMMA, while in the composites, the typical EPR signal of the PMMA radicals was observed, which increased with the amount of HA or SW. When comparing the relative intensities of the EPR signals for both types of composites, a slight increase in the concentration of free radicals generated in the sample with SW respect to that of PMMA/HA composite was obtained. A decay of the total free radical concentration was observed as time elapsed.

Silva, P.; Albano, C.; Perera, R.; Domínguez, N.

2010-03-01

331

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

332

[Research development of hydroxyapatite-based composites used as hard tissue replacement].  

PubMed

Hydroxyapatite has been considered as the most promising materials for hard tissue replacements, due to its similar chemical composition and crystallographic structure to that of bone mineral. But the brittleness is one of the most serious obstacles for its wider applications as load-bearing implants. Therefore, various HA composites get much attention. In the present paper, HA composites were introduced according to the kind of reinforcement. Although bioactive ceramics, bioactive glass or glass-ceramic, bio-inactive ceramics, polymers and metals all have been used to fabricate HA composites, no one can well satisfy the requirements for hard tissue replacement. The vital problem of the existing HA composites is that the biological properties cannot match with the mechanical properties well. PMID:14565037

Ning, Congqin; Dai, Kerong

2003-09-01

333

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

334

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

Microsoft Academic Search

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

Hyun Jung Chung; Jin Sup Jung; Tae Gwan Park

2011-01-01

335

Crush Strength of Encapsulated Microspheres.  

National Technical Information Service (NTIS)

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 incorpor...

J. E. Marra

1988-01-01

336

Antibacterial coatings of fluoridated hydroxyapatite for percutaneous implants.  

PubMed

Percutaneous orthopedic and dental implants require not only good adhesion with bone but also the ability to attach and form seals with connective tissues and the skin. To solve the skin-seal problem of such implants, an electrochemical deposition method was used to modify the surfaces of metallic implants to improve their antibacterial ability and skin seals around them. A dense and uniform fluoridated calcium phosphate coating with a thickness of about 200 nm was deposited on an acid-etched pure titanium substrate by controlling the current density and reaction duration of the electrochemical process. The as-deposited amorphous fluoridated calcium phosphate transformed to fluoridated hydroxyapatite (FHA) after heat treatment at 600°C in a water vapor environment for 3 h. Both single crystal diffraction patterns and high-resolution transmission electron microscope (HRTEM) images confirmed the phase of the fluoridated calcium phosphate after the heat treatment. The antibacterial activities of FHA coatings were tested against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Porphyromonas gingivalis (P. gingivalis) with the film attachment method. The antibacterial activity of FHA coating is much higher than that of pure hydroxyapatite (HA) coating and acid-etched pure titanium surface. The promising features of FHA coating make it suitable for orthopedic and dental applications. PMID:20725973

Ge, Xiang; Leng, Yang; Bao, Chongyun; Xu, Sherry Li; Wang, Renke; Ren, Fuzeng

2010-11-01

337

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

338

Effects of DCPD cement chemistry on degradation properties and cytocompatibility: comparison of MCPM/?-TCP and MCPM/HA formulations.  

PubMed

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

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

2013-02-22

339

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

340

Bone integration capability of nanopolymorphic crystalline hydroxyapatite coated on titanium implants  

PubMed Central

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

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

2012-01-01

341

Induction plasma sprayed Sr and Mg doped nano hydroxyapatite coatings on Ti for bone implant.  

PubMed

In this study, we report fabrication of strontium (Sr) and magnesium (Mg) doped hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) substrates using inductively coupled radio frequency (RF) plasma spray. HA powder was doped with 1 wt % Sr (Sr-HA) and 1 wt % Mg (Mg-HA), heat treated at 800°C for 6 h and then used for plasma spray coating. X-ray diffraction (XRD) and Fourier transformed infrared spectroscopic (FTIR) analysis indicated that the coatings were primarily composed of phase pure crystalline HA. When compared to undoped HA coating, physical properties such as microstructure, grain size, and adhesive bond strength of the doped HA coatings did not change significantly. Microstructure of the coatings showed coherency in the structure with an average grain size of 200-280 ?m HA particles, where each of the HA grains consisted of 20-30 nm sized particles. An average adhesive bond strength of 17 MPa ensured sufficient mechanical strength of the coatings. A chemistry dependent improvement in bone cell-coating interaction was noticed for doped coatings although it had minimal effect on physical properties of the coatings. In vitro cell-materials interactions using human fetal osteoblasts (hFOB) showed better cell attachment and proliferation on Sr-HA coatings compared to HA or Mg-HA coatings. Presence of Sr in the coating also stimulated hFOB cell differentiation and alkaline phosphatase (ALP) expression. Improvement in bioactivity of Sr doped HA coatings on Ti without compromising its mechanical properties makes it an excellent material of choice for coated implant. PMID:21714088

Roy, Mangal; Bandyopadhyay, Amit; Bose, Susmita

2011-06-28

342

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

343

Mechanical Properties of Hydroxyapatite and OH-carbonated Hydroxyapatite Single Crystals  

Microsoft Academic Search

Single-crystal hydroxyapatite and OH-carbonated hydroxyapatite have bending strength much higher than that of dense hydroxyapatite ceramic, indicating potential applicability to a load-bearing biomaterial. However, the effects of carbonate on the strength are less clear. The objective of the present study was to determine the bending strength and Young's modulus of these single crystals with carbonate contents from 0 to 0.62

K. Teraokal; A. Ito; K. Maekawal; K. Onuma; T. Tateishi; S. Tsutsumi

1998-01-01

344

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

NASA Astrophysics Data System (ADS)

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

Kumar, Alok; Biswas, Krishanu; Basu, Bikramjit

2013-10-01

345

Influence of temperature and aging time on HA synthesized by the hydrothermal method.  

PubMed

The influence of temperature and aging time on the morphology and mechanical properties of nano-sized hydroxyapatite (HA) synthesized by a hydrothermal method is reported here. The pre-mixed reactants were poured into a stirred autoclave and reacted at temperatures between 25-250 degrees C for 2-10 h. HA powders thus obtained were examined using X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FESEM) and a particle size analyzer. It was found that the aspect ratio of the particles increased with the reaction temperature. The length of the HA particles increased with the reaction temperature below 170 degrees C, but it decreased when the temperature was raised above 170 degrees C. The agglomerates of HA particles were formed during synthesis, and their sizes were strongly dependent on reaction temperatures. As the reaction temperature increased, the agglomerate size decreased (p = 0.008). The density of the discs pressed from these samples reached 85-90% of the theoretical density after sintering at 1200 degrees C for 1 h. No decomposition to other calcium phosphates was detected at this sintering temperature. A correlation existed (p = 0.05) between the agglomerate sizes of HA particles synthesized at various conditions and their sintered densities. With the increase of the agglomerate size, the sintered density of the HA compact decreased. It was found that both the sintered density and flexural strength increased with increasing aging time and reaction temperature. A maximum flexural strength of 78 MPa was observed for the samples synthesized at 170 degrees C for 5 h with the predicted average at these conditions being 65 MPa. These samples attained an average sintered density of 88%. PMID:15875254

Kothapalli, C R; Wei, M; Legeros, R Z; Shaw, M T

2005-05-01

346

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.

347

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

PubMed

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

Carradó, Adele

2010-02-01

348

Enhancement of peptide coupling to hydroxyapatite and implant osseointegration through collagen mimetic peptide modified with a polyglutamate domain  

PubMed Central

Hydroxyapatite (HA) is a widely-used biomaterial for bone repair due to its high degree of osteoconductivity. However, strategies for improving HA performance by functionalizing surfaces with bioactive factors are limited. In this study, we explored the use of an HA-binding domain (heptaglutamate, “E7”) to facilitate coupling of the collagen mimetic peptide, DGEA, to two types of HA-containing materials, solid HA disks and electrospun polycaprolactone matrices incorporating nanoparticulate HA. We found that the E7 domain directed significantly more peptide to the surface of HA and enhanced peptide retention on both materials in vitro. Moreover, E7-modified peptides were retained in vivo for at least two months, highlighting the potential of this mechanism as a sustained delivery system for bioactive peptides. Most importantly, E7-DGEA-coupled HA, as compared with DGEA-HA, enhanced the adhesion and osteoblastic differentiation of mesenchymal stem cells, and also increased new bone formation and direct bone-implant contact on HA disks implanted into rat tibiae. Collectively, these results support the use of E7-DGEA peptides to promote osteogenesis on HA substrates, and further suggest that the E7 domain can serve as a universal tool for anchoring a wide variety of bone regenerative molecules to any type of HA-containing material.

Culpepper, B.K.; Phipps, M.C.; Bonvallet, P. P.; Bellis, S.L.

2010-01-01

349

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

350

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

351

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

PubMed

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

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

1997-12-01

352

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. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:2925-2938, 2013. PMID:23529941

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

2013-03-26

353

Effect of the Mass Ratio of CaCO 3 to CaHPO 4·2H 2O on in Situ Synthesis of Hydroxyapatite Coating by Laser Cladding  

Microsoft Academic Search

Hydroxyapatite coatings were fabricated on Ti substrates by laser cladding (LC) using mixed powders of CaCO3 and dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O). The effect of the mass ratio of CaCO3 to DCPD on phase and microstructure formation of the coatings was investigated. The reactions between CaCO3 and DCPD can produce high crystallized hydroxyapatite (HA, Ca5(PO4)3(OH)) in the coatings as well

Lü Xiaowei; Lin Xin; Guan Taihong; Gao Bo; Huang Weidong

2011-01-01

354

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

PubMed

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

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

2013-01-01

355

Characterization of functionally graded hydroxyapatite/titanium composite coatings plasma-sprayed on Ti alloys.  

PubMed

Bioceramic coatings like hydroxyapatite (HA) have shown promising bioactive properties in load-bearing implant applications. The aim of this work is to deposit functionally graded HA/Ti layers consisting of an underlying Ti bond coat, the alternating layer, and an HA top-layer on Ti6Al4V substrates using plasma spray to improve the coating-substrate interface properties. The alternating layers were created by means of changing the feeding rate and input power of Ti and HA powders, which gradually decrease Ti content with increasing depth from the Ti bond-coat. The major consideration is to examine the stability of the graded coatings. Experimental results indicated that surface chemistry and morphology of the graded coatings were similar to those of monolithic HA coatings. The bond strength values of the as-sprayed graded coatings were much superior to those of monolithic HA coatings. The cyclic fatigue did have a statistically significant effect on bond strength of monolithic HA coatings, with a decrease of 23%. However, the graded coatings were able to survive 1 million cycles of loading in air without significantly reduced bond strength. The in vitro electrochemical measurement results also indicated that the graded coatings had a more beneficial and desired behavior than monolithic HA coatings after fatigue. PMID:16292766

Chen, Chun-Cheng; Huang, Tsui-Hsien; Kao, Chia-Tze; Ding, Shinn-Jyh

2006-07-01

356

Oxidative stress and apoptosis induced by hydroxyapatite nanoparticles in C6 cells.  

PubMed

Hydroxyapatite (HA) nanoparticles have been reported to exhibit anti-tumor effects on various human cancers, but the effects of HA on glioma cells remain unclear. The aim of this study was to explore whether HA can inhibit the proliferation and induce the apoptosis of C6 cells. Use of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated that HA induced C6 cell death in a concentration-dependent and time-dependent manner. Results from hoechst 33342 staining and flow cytometry assay showed that HA induced C6 cell apoptosis significantly. Meanwhile, the flow cytometric assay gave clear indication that HA induced intracellular accumulation of reactive oxygen species (ROS). The measurement of superoxide dismutase (SOD) generation showed that HA decreased the total SOD of cellular levels. Interestingly, pretreatment of N-(mercaptopropionyl)-glycine (N-MPG), known as a type of ROS scavenger formulations, could somehow inhibit C6 cell apoptosis induced by HA. These results may provide potential anti-glioma treatment in the future. PMID:22213249

Xu, Jing; Xu, Pengjuan; Li, Zhigui; Huang, Jie; Yang, Zhuo

2011-12-31

357

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

NASA Astrophysics Data System (ADS)

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 low power plasma (1.3-8 kW) and vortex which produces the main plasma with high power level (10-40 kW). Controlling the spraying parameters is the key role for spraying high crystalline HA coatings on the metallic implants. In this study, the arc gun current was changed while the vortex arc current was kept constant at 450 A during the spraying process of HA coatings. The objective of this study is to investigate the influence of gun current on the microstructure, phase crystallinity and hardness properties of HA coatings. The surface morphology and microstructure of as-sprayed coatings were examined by scanning electron microscope. The phase structure of HA coatings was investigated by X-ray diffraction analysis. HA coatings sprayed at high gun current (100 A) are dense, and have high hardness. The crystallinity of HA coatings was decreased with the increasing in the gun current. On the other hand, the hardness was slightly decreased and the coatings suffer from some porosity at gun currents 0, 30 and 50 A.

Morks, M. F.; Kobayashi, A.

2007-06-01

358

Physical Properties and Cellular Responses to Crosslinkable Poly(Propylene Fumarate)/Hydroxyapatite Nanocomposites  

PubMed Central

A series of crosslinkable nanocomposites has been developed using hydroxyapatite (HA) nanoparticles and poly(propylene fumarate) (PPF). PPF/HA nanocomposites with four different weight fractions of HA nanoparticles have been characterized in terms of thermal and mechanical properties. To assess surface chemistry of crosslinked PPF/HA nanocomposites, their hydrophilicity and capability of adsorbing proteins have been determined using static contact angle measurement and MicroBCA protein assay kit after incubation with 10% fetal bovine serum (FBS), respectively. In vitro cell studies have been performed using MC3T3-E1 mouse pre-osteoblast cells to investigate the ability of PPF/HA nanocomposites to support cell attachment, spreading, and proliferation after 1, 4, and 7 days. By adding HA nanoparticles to PPF, the mechanical properties of crosslinked PPF/HA nanocomposites have not been increased due to the initially high modulus of crosslinked PPF. However, hydrophilicity and serum protein adsorption on the surface of nanocomposites have been significantly increased, resulting in enhanced cell attachment, spreading, and proliferation after 4 days of cell seeding. These results indicate that crosslinkable PPF/HA nanocomposites are useful for hard tissue replacement because of excellent mechanical strength and osteoconductivity.

Lee, Kee-Won; Wang, Shanfeng; Yaszemski, Michael J.; Lu, Lichun

2008-01-01

359

X-ray peak broadening studies of nanocrystalline hydroxyapatite by Williamson-Hall analysis  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) nanoparticles were prepared by microwave synthesis method and the obtained powder is annealed at 800 °C for 2 h. The annealed HA particles were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy methods. The HA size and morphology were examined using a transmission electron microscope (TEM). The XRD results reveal that the diffraction peaks of the annealed HA were of well crystalline and correspond to the hexagonal crystal structure. The XRD and FTIR results confirm the absence of secondary phases such as ?-tricalcium phosphate (?-TCP) and calcium oxide in annealed HA particles. The TEM result confirms the hexagonal structure of annealed HA and the particles were observed to be of ellipsoid-like shaped morphology with less agglomeration. The lattice strain, crystallite size, lattice deformation stress and deformation energy density for annealed (800 °C) HA nanoparticles were estimated by Williamson-Hall-isotropic strain model (W-H-ISM), W-H-anisotropic strain model (W-H-ASM) and W-H-energy density model (W-H-EDM) based on Williamson-Hall (W-H) plot from powder X-ray diffraction data. The results of estimated average crystallite size of annealed HA by Scherrer and W-H plot methods were compared with TEM results. It is found that the average crystallite size measured by W-H plot methods is in good agreement with TEM results.

Venkateswarlu, K.; Chandra Bose, A.; Rameshbabu, N.

2010-10-01

360

Study of the composition transfer in the pulsed laser deposition of silicon substituted hydroxyapatite thin films  

NASA Astrophysics Data System (ADS)

The field of biomaterials has lately been showing an important interest in the production of bioactive ceramic coatings capable of improving the adhesion of metal prostheses to the living tissue. Among these ceramics, the most notable is hydroxyapatite (HA) due to its similarities with the mineral part of the bone. The need to emphasize these resemblances led to the production of silicon substituted HA (Si-HA), a material which has shown better biological performance compared to the traditional HA. Coatings were prepared by pulsed laser deposition (PLD) technique, starting from mixtures of pure HA with Si powders. The laser matter interaction successfully transferred the Si-HA to the substrate incorporating the Si atoms within its structure. The Si-HA thin films were characterized in terms of structure and chemical composition by many different techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XPS), energy dispersive spectroscopy (EDS) and ion beam spectroscopy techniques such as Rutherford back scattering (RBS), particle induced X-ray emission (PIXE), elastic recoil detection (ERD) and nuclear reaction analysis (NRA). The analysis demonstrated that Si is efficiently transferred to the HA structure in the form of SiO44- groups. The dependence of the target composition on the film growth and on the Si content of the coatings is also presented.

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

2007-07-01

361

Adsorptive removal of Pb(II) from aqueous solution using nano-sized hydroxyapatite  

NASA Astrophysics Data System (ADS)

This study investigated the sorption of Pb(II) in aqueous solution onto hydroxyapatite (HA) surfaces. Batch experiments were carried out using synthetic HA. The effect of contact time, HA dosage, and initial pH on removal efficiency were also investigated. The adsorption equilibrium and kinetics of Pb(II) on this adsorbent were then examined at 25 °C. Kinetic data were analyzed by pseudo first, second, and intra-particle diffusion models. The sorption data were then correlated with the Langmuir, Freundlich, Halsey, and Harkins-Jura adsorption isotherm models. The optimum dose of HA for Pb(II) removal is found to be 0.12 g/l with the removal efficiency of 97.3 % at an equilibrium contact time of 1 h. It is found that the adsorption kinetics of the Pb(II) on HA follow the pseudo second-order reaction. All the isotherms fitted well for experimental data. Capacity of HA is found as 357.14 mg Pb(II)/g of HA. The Pb(II) immobilization mechanism was studied. The results indicated that HA can be used as an effective adsorbent for removal of Pb(II) from aqueous solution.

Ramesh, S. T.; Rameshbabu, N.; Gandhimathi, R.; Srikanth Kumar, M.; Nidheesh, P. V.

2013-03-01

362

Osteoconductivity of thermal-sprayed silver-containing hydroxyapatite coating in the rat tibia.  

PubMed

A silver-containing hydroxyapatite (Ag-HA) coating has been developed using thermal spraying technology. We evaluated the osteoconductivity of this coating on titanium (Ti) implants in rat tibiae in relation to bacterial infection in joint replacement. At 12 weeks, the mean affinity indices of bone formation of a Ti, an HA, a 3%Ag-HA and a 50%Ag-HA coating were 97.3%, 84.9%, 81.0% and 40.5%, respectively. The mean affinity indices of bone contact of these four coatings were 18.8%, 83.7%, 77.2% and 40.5%, respectively. The indices of bone formation and bone contact around the implant of the 3%Ag-HA coating were similar to those of the HA coating, and no significant differences were found between them (bone formation, p = 0.99; bone contact, p = 0.957). However, inhibition of bone formation was observed with the 50%Ag-HA coating. These results indicate that the 3%Ag-HA coating has low toxicity and good osteoconductivity, and that the effect of silver toxicity on osteoconductivity depends on the dose. PMID:21511931

Yonekura, Y; Miyamoto, H; Shimazaki, T; Ando, Y; Noda, I; Mawatari, M; Hotokebuchi, T

2011-05-01

363

Stability of hydroxyapatite-coatings on titanium oral implants (IMZ). 2 retrieved cases.  

PubMed

2 hydroxyapatite(HA)-coated titanium oral implants (IMZ) were retrieved from 2 patients after more than three years in clinical function. One implant (case I) was removed because of extensive bone resorption and loss of integration, and the other (case II) was retrieved due to fracture of the abutment in sprit of clinical rigidity. The implants and the surrounding soft (case I) and hard (case II) tissues were examined histologically and by scanning electron microscopy (SEM). In case I, the HA-coating was almost degraded, as SEM revealed a resulted rough titanium surface. Histology showed HA particles and inflammation were seen near the implant. In Case II, the HA-coating seemed to be intact and bonded to bone, but scattered HA particles, embedded in bone at a distance from the implant were also observed. The results indicate that HA-coatings may come loose during clinical function. The long-term stability of HA-coatings and the clinical indications for HA-coated implants warrant further study. PMID:9586458

Liao, H; Fartash, B; Li, J

1997-02-01

364

In vivo study on hydroxyapatite scaffolds with trabecular architecture for bone repair.  

PubMed

The objective of this research was to investigate the bone formation and angio-conductive potential of hydroxyapatite (HA) scaffolds closely matched to trabecular bone in a canine segmental defect after 3 and 12 weeks post implantation. Histomorphometric comparisons were made between naturally forming trabecular bone (control) and defects implanted with scaffolds fabricated with micro-size (M-HA) and nano-size HA (N-HA) ceramic surfaces. Scaffold architecture was similar to trabecular bone formed in control defects at 3 weeks. No significant differences were identified between the two HA scaffolds; however, significant bone in-growth was observed by 12 weeks with 43.9 +/- 4.1% and 50.4 +/- 8.8% of the cross-sectional area filled with mineralized bone in M-HA and N-HA scaffolds, respectively. Partially organized, lamellar collagen fibrils were identified by birefringence under cross-polarized light at both 3 and 12 weeks post implantation. Substantial blood vessel infiltration was identified in the scaffolds and compared with the distribution and diameter of vessels in the surrounding cortical bone. Vessels were less numerous but significantly larger than native cortical Haversian and Volkmann canals reflecting the scaffold architecture where open spaces allowed interconnected channels of bone to form. This study demonstrated the potential of trabecular bone modeled, highly porous and interconnected, HA scaffolds for regenerative orthopedics. PMID:18478555

Appleford, Mark R; Oh, Sunho; Oh, Namsik; Ong, Joo L

2009-06-15

365

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

SciTech Connect

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

Dasarathy, H.

1992-01-01

366

Diffusion Flame Synthesis of Hydroxyapatite Nanoparticles using Urea Assisted Precursor Solution  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

367

Immobilization of silver nanoparticles on silica microspheres  

Microsoft Academic Search

The silver nanoparticles (Ag NPs) have been immobilized onto silica microspheres through the adsorption and subsequent reduction\\u000a of Ag+ ions on the surfaces of the silica microspheres. The neat silica microspheres that acted as the core materials were prepared\\u000a through sol–gel processing; their surfaces were then functionalized using 3-mercaptopropyltrimethoxysilane (MPTMS). The major\\u000a aims of this study were to immobilize differently

Chih-Kai Huang; Chia-Yin Chen; Jin-Lin Han; Chii-Chang Chen; Meng-Dan Jiang; Jen-Sung Hsu; Chia-Hua Chan; Kuo-Huang Hsieh

2010-01-01

368

REGISTRATION OF THREE LOW CADMIUM (HA 448, HA 449, AND RHA 450) CONFECTION SUNFLOWER GENETIC STOCKS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Two maintainer (HA 448 and HA 449) and one restorer (RHA 450) confection sunflower (Helianthus annuus L.) genetic stocks were developed cooperatively and released by the USDA-ARS, Fargo, ND, and the North Dakota Agricultural Experiment Station, Fargo, ND. These genetic stocks are available for use b...

369

The importance of amino acid interactions in the crystallization of hydroxyapatite.  

PubMed

Non-collagenous proteins (NCPs) inhibit hydroxyapatite (HA; Ca(5)(PO(4))(3)OH) formation in living organisms by binding to nascent nuclei of HA and preventing their further growth. Polar and charged amino acids (AAs) are highly expressed in NCPs, and the negatively charged ones, such as glutamic acid (Glu) and phosphoserine (P-Ser) seem to be mainly responsible for the inhibitory effect of NCPs. Despite the recognized importance of these AAs on the behaviour of NCPs, their specific effect on HA crystallization is still unclear, and controversial results have been reported concerning the efficacy of HA inhibition of positively versus negatively charged AAs. We focused on a positively charged (arginine, Arg) and a negatively charged (Glu) AA, and their combination in the same solution. We studied their inhibitory effect on HA nucleation and growth at physiological temperature and pH and we determined the mechanism by which they can affect HA crystallization. Our results showed a strong inhibitory effect of Arg on HA nucleation; however, Glu was more effective in inhibiting HA crystal growth during the growth stage. The combination of Glu and Arg was less effective in controlling HA nucleation, but it inhibited HA crystal growth. We attributed these differences to the stability of complexes formed between AAs and calcium and phosphate ions at the nucleation stage, and in bonding strength of AAs to HA crystal faces during the growth stage. The AAs also influenced the morphology of synthesized HA. Presence of either Arg or Glu resulted in the formation of spherulites consisting of preferentially oriented nanoplatelets orientation. This was attributed to kinetic factors favoring growth front nucleation (GFN) mechanism. PMID:23269851

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

2012-12-26

370

Improvement of bioactivity with magnesium and fluorine ions incorporated hydroxyapatite coatings via sol–gel deposition on Ti6Al4V alloys  

Microsoft Academic Search

Magnesium (Mg) is a trace element in natural bone, its existence plays an important role in cell adhesion and bone formation. To improve the biological properties, Mg and fluorine (F) are simultaneously incorporated in hydroxyapatite (HA) to form MgxFHA coating on titanium alloy via sol–gel process. In vitro bioactivity of the coating is evaluated by examination of apatite precipitation on

Yanli Cai; Sam Zhang; Xianting Zeng; Yongsheng Wang; Min Qian; Wenjian Weng

2009-01-01

371

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

Microsoft Academic Search

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

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

2012-01-01

372

Design, fabrication, and characterization of laminated hydroxyapatite-polysulfone composites  

NASA Astrophysics Data System (ADS)

There exists a need to develop devices that can be used to replace hard tissues, such as bone, in load-bearing areas of the body. An ideal hard tissue replacement device is one that stimulates growth of natural tissues, and is slowly resorbed by the body. The implant is also required to have elastic modulus, strength, and toughness values similar to the tissues being replaced. Hydroxyapatite (HA) is the primary mineral phase of bone and has the potential for use in biomedical applications because it stimulates cell growth and is resorbable. Unfortunately, HA is a relatively low strength, low toughness material, which limits its application to only low load-bearing regions of the body. In order to apply HA to greater load-bearing areas of the body, strength and toughness must be improved through the formation of a composite structure. The goal of this study to show that a composite structure formed from HA and a biocompatible polymer can be fabricated with strength and toughness values that are within the range necessary for load-bearing biomedical applications. Therefore, Polysulfone-HA composites were developed and tested. Polysulfone (PSu) is a hard, glassy polymer that has been shown to be biocompatible. Composites were fabricated through a combination of tape casting, solvent casting, and lamination. Monolithic HA and laminate specimens were tested in biaxial flexure. A unique laminate theory solution was developed to characterize stress distributions for laminates. Failure loads, failure stress, work of fracture, and apparent toughness were compared for the laminates against monolithic HA specimens. Initial testing results showed that laminates had a failure stress of 60 +/- 10, which is a 170% improvement over the 22 +/- 2 MPa failure stress for monolithic HA. The work of fracture was improved by 5500% from 11 +/- 2 for the monolithic HA to 612 +/- 240 for the laminates. Work of fracture values gave the laminates an apparent fracture toughness of 7.2 MPa•m1/2 compared to 0.6 MPa•m1/2 for the monolithic HA. Laminates with different geometries were built and tested in an attempt to optimize the strength and toughness of the composites. Laminate behavior was characterized as a function of initial flaw size, HA layer thickness, PSu layer thickness, and stressing rate. The failure stress of the laminates was maximized at a value of 108 +/- 14 MPa, which is a 400% improvement over monolithic HA, and close to the 12-160 MPa range reported for bone. The work of fracture of laminates was maximized at 724 +/- 206 J/m2, which is a 6400% improvement over monolithic HA, and yields an apparent fracture toughness value of 7.5 MPa•m1/2. This apparent toughness value is within the 2-12 MPa•m1/2 range for bone, and an 1100% improvement over the fracture toughness of monolithic HA.

Wilson, Clifford Adams, II

373

In vitro studies of plasma-sprayed hydroxyapatite\\/Ti6Al4V composite coatings in simulated body fluid (SBF)  

Microsoft Academic Search

The bioactivity of plasma-sprayed hydroxyapatite (HA)\\/Ti-6Al-4V composite coatings was studied by soaking the coatings in simulated body fluid (SBF) for up to 8 weeks. This investigation was aimed at elucidating the biological behaviour of plasma-sprayed HA\\/Ti-6Al-4V composite coatings by analyzing the changes in chemistry, and crystallinity of the composite coating in a body-analogous solution. Phase composition, microstructure and calcium ion

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

2003-01-01

374

Hydroxyapatite-collagen composites. Part I: can the decrease of the interactions between the two components be a physicochemical component of osteoporosis in aged bone?  

Microsoft Academic Search

The interactions of Type I acid soluble collagen (Col) with both carbonate-free hydroxyapatite (HA1100) and carbonate-rich one (CHA) were investigated. The aim was to ascertain whether the increase of bone CO3\\u000a 2? with ageing could relate to the disease known as osteoporosis. HA1100-Col and CHA-Col composites with various ratios were prepared and examined. Scanning electron microscopy and differential\\u000a scanning calorimetry

Niccoletta Barbani; Elisabetta Rosellini; Caterina Cristallini; Giulio D. Guerra; Adriano Krajewski; Mauro Mazzocchi

2011-01-01

375

Fabrication and mechanical properties of PLLA\\/PCL\\/HA composites via a biomimetic, dip coating, and hot compression procedure  

Microsoft Academic Search

Currently, the bone-repair biomaterials market is dominated by high modulus metals and their alloys. The problem of stress-shielding,\\u000a which results from elastic modulus mismatch between these metallic materials and natural bone, has stimulated increasing research\\u000a into the development of polymer-ceramic composite materials that can more closely match the modulus of bone. In this study,\\u000a we prepared poly(l-lactic acid)\\/hydroxyapatite\\/poly(?-caprolactone) (PLLA\\/HA\\/PCL) composites

L. F. Charles; M. T. Shaw; J. R. Olson; M. Wei

2010-01-01

376

Ha Emission extraction using Narrowband Photometric Filters  

NASA Astrophysics Data System (ADS)

Maria Mitchell Observatory has explored using Narrowband Photometric (<100A) filters to substitute for spectroscopic observations. The method is thought to have significant signal to noise advantages over spectroscopic observations for small telescopes. These small telescopes offer advantages for projects requiring intensive monitoring where telescope time is limited on larger telescopes. RR Tau, a suspected UXOR, was intensively observed by the MMO 0.6 M RC in Nantucket, Mass and the .29M W28 AAVSOnet telescope from Cloudcroft, New Mexico during the 2010 Winter & Spring season. Observations were made in Ha with 45A and 100A narrowband filters as well as the continuum at 6450 A with 50A and 100A filters. Ha emission was extracted with an error of 8% and compared to the change in the continuum. RR Tau exhibited a 30% change in emission while the continuum change by over a factor of 5.

Walker, Gary E.

2011-05-01

377

Detection of Hydroxyapatite in Calcified Cardiovascular Tissues  

PubMed Central

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

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

2012-01-01

378

Substituted hydroxyapatites for bone repair.  

PubMed

Calcium phosphates such as hydroxyapatite have a wide range of applications both in bone grafts and for the coating of metallic implants, largely as a result of their chemical similarity to the mineral component of bone. However, to more accurately mirror the chemistry, various substitutions, both cationic (substituting for the calcium) and anionic (substituting for the phosphate or hydroxyl groups) have been produced. Significant research has been carried out in the field of substituted apatites and this paper aims to summarise some of the key effect of substitutions including magnesium, zinc, strontium, silicon and carbonate on physical and biological characteristics. Even small substitutions have been shown to have very significant effects on thermal stability, solubility, osteoclastic and osteoblastic response in vitro and degradation and bone regeneration in vivo. PMID:22389101

Shepherd, Jennifer H; Shepherd, David V; Best, Serena M

2012-03-03

379

Adhesion strength characterization of PVDF/HA coating on cp Ti surface modified by laser beam irradiation  

NASA Astrophysics Data System (ADS)

Up to the moment, there is no standardized test for measuring the adhesion strength of polymeric coatings on titanium substrate modified by laser beam irradiation. The present work aimed to assess the adhesion strength of polyvinylidene fluoride (?-PVDF)/hydroxyapatite (HA) composite coating on commercially pure titanium (?-cp Ti) substrate surface modified by laser beam irradiation, using the three-point bending test. The preparation of coating was carried out by mixing ?-PVDF pellets dissolved in dimethylacetamide (DMA) with HA/DMA emulsion. The mixture was poured onto the ?-cp Ti sample and left to dry in an oven. Commercially pure titanium plates were coated with ?-PVDF/HA composite film, in proportions of 100/00 (PVDF) and 60/40 (PVDF/HA) in weight. The Ti-PVDF/HA samples were subjected to the three-point bending test and analyzed by scanning electron microscopy. According to the results, PVDF and PVDF/HA coatings showed a good adhesion strength on ?-cp Ti surface, since no detachment was observed.

Ribeiro, A. A.; Vaz, L. G.; Guastaldi, A. C.; Campos, J. S. C.

2012-10-01

380

Biodegradable microspheres for parenteral delivery.  

PubMed

Nowadays, emphasis is being laid to development of controlled release dosage forms. Interest in this technology has increased steadily over the past few years. Although oral administration of drugs is a widely accepted route of drug delivery, bioavailability of drug often varies as a result of gastrointestinal absorption, degradation by first-pass effect, and hostile environment of gastrointestinal tract. Transdermal administration for percutaneous absorption of drug is limited by the impermeable nature of the stratum corneum. Ocular and nasal delivery is also unfavorable because of degradation by enzymes present in eye tissues and nasal mucosa. Hence, the parenteral route is the most viable approach in such cases. Of the various ways of achieving long-term parenteral drug delivery, biodegradable microspheres are one of the better means of controlling the release of drug over a long time. Because of the lipidic nature of liposomes, problems such as limited physical stability and difficulty of freeze-drying are encountered. Similarly, for emulsions, stability on long-term basis and in suspensions, rheological changes during filling, injecting, and storage poses limitation. Also, in all these systems, the release rate cannot be tailored to the needs of the patient. Parenteral controlled-release formulations based on biodegradable microspheres can overcome these problems and can control the release of drug over a predetermined time span, usually in the order of days to weeks to months. Various FDA-approved controlled-release parenteral formulations based on these biodegradable microspheres are available on the market, including Lupron Depot Nutropin Depot and Zoladex. This review covers various molecules encapsulated in biodegradable microspheres for parenteral delivery. PMID:16566705

Sinha, V R; Trehan, A

2005-01-01

381

Microwave assisted synthesis & properties of nano HA-TCP biphasic calcium phosphate  

NASA Astrophysics Data System (ADS)

Biphasic calcium phosphate (BCP) nanopowders were synthesized by using microwave and non-microwave irradiation assisted processes. The synthesized powders were pressed under a pressure of 90 MPa, and then were sintered at 1000-1200°C for 1 h. The mechanical properties of the samples were investigated. The formed phases and microstructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the synthesis time was shorter, along with a more homogeneous microstructure, when the microwave irradiation assisted method was applied. The compression strength and the Young's modulus of the samples synthesized with microwave irradiation were about 60 MPa and 3 GPa, but those of the samples synthesized without microwave irradiation were about 30 MPa and 2 GPa, respectively. XRD patterns of the microwave irradiation assisted and non-microwave irradiation assisted nanopowders showed the coexistence of hydroxyapatite (HA) and tricalcium phosphate (TCP) phases in the system.

Ghomash Pasand, E.; Nemati, A.; Solati-Hashjin, M.; Arzani, K.; Farzadi, A.

2012-05-01

382

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

PubMed

The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results showed that the HA feedstock decomposed after rf plasma processing. Crystalline HA, alpha-tri-calcium phosphate (alpha-TCP), tetra-calcium phosphate (TTCP) and calcium oxide (CaO) were detected in the plasma-spheroidized powders. Raman spectra results indicated strong presence of amorphous calcium phosphate (ACP) in the spheroidized powders. The particle size distribution and specific surface area were influenced through the rf plasma working plate power levels. The sintering behavior of the rf plasma synthesized powders was analyzed through the SPS process and the results indicated that the spheroidized powders commence sintering at approximately 900 degrees C and through to 1150 degrees C. After sintering above 1100 degrees C for 3min, the relative densities of the SPS compacts reached 96% of the theoretical value. The SPS compacts were immersed in simulated body fluids (SBF) for different durations and the results confirmed their bioactivities. PMID:15585221

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

2005-05-01

383

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

SciTech Connect

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

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

1997-08-01

384

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

PubMed

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

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

2002-01-01

385

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

PubMed

A composite coating of hydroxyapatite (HA)/multi-walled carbon nanotubes (MWNTs) has been fabricated by electrophoretic deposition (EPD). The nano powders of HA and MWNTs were dispersed in ethanol with total concentration of 0.005 g/mL and MWNTs 20% and 30% contents (wt). And the pH value of suspension was adjusted in a range from 4 to 5. After stabilization the mixture was ultrasonically treated for 3 h to form a stable suspension. Prior to the electrophoretic deposition, the titanium substrate was hydrothermally treated at 140 in NaOH (10 mol/L) solution for 6 h. A titanium sheet and circinal net of stainless steel were used as a cathode and an anode respectively, and a constant deposition voltage of 30 V was applied for 50-60 s in the EPD process. The thickness of the coatings was controlled from 10 microm to 20 microm. The samples of composite coating were then sintered in a resistance tube furnace in flowing argon at 700 for 2 h. The structure of the as prepared coating was characterized by SEM and XRD, and the bonding force of the coating/substrate was measured by an interfacial shear strength test. It is shown that the bonding strengths between the coating and the titanium substrate is as high as 35 MPa. The cell culture experiments indicate that the prepared composite coating of HA/MWNTs possesses good biocompatibility. PMID:17619960

Lin, Changjian; Han, Huijuan; Zhang, Fang; Li, Aimin

2007-07-10

386

Characterization and bond strength of electrolytic HA/TiO2 double layers for orthopaedic applications.  

PubMed

Insufficient bonding of juxtaposed bone to an orthopaedic/dental implant could be caused by material surface properties that do not support new bone growth. For this reason, fabrication of biomaterials surface properties, which support osteointegration, should be one of the key objectives in the design of the next generation of orthopaedic/dental implants. Titanium and titanium alloy have been widely used in several bioimplant applications, but when implanted into the human body, these still contain some disadvantages, such as poor osteointegration (forming a fibrous capsule), wear debris and metal ion release, which often lead to clinical failure. Electrolytic hydroxyapatite/titanium dioxide (HA/TiO2) double layers were successfully deposited on titanium substrates in TiCl4 solution and subsequently in the mixed solution of Ca(NO3)2 and NH4H2PO4, respectively. After annealing at 300 degrees C for 1 h in the air, the coated specimens were evaluated by dynamic cyclic polarization tests, immersion tests, tensile tests, surface morphology observations, XRD analyses and cells culture. The adhesion strength of the HA coating were improved by the intermediate coating of TiO2 from 11.3 to 46.7 MPa. From cell culture and immersion test results, the HA/TiO2 coated specimens promoted not only cells differentiation, but also appeared more bioactive while maintaining non-toxicity. PMID:16167097

Lin, Chi-Min; Yen, Shiow-Kang

2005-10-01

387

Characterization and bond strength of electrolytic HA/TiO2 double layers for orthopedic applications.  

PubMed

Insufficient bonding of juxtaposed bone to an orthopedic/dental implant could be caused by material surface properties that do not support new bone growth. For this reason, fabrication of biomaterials surface properties, which support osteointegration, should be one of the key objectives in the design of the next generation of orthopedic/dental implants. Titanium and titanium alloy have been widely used in several bioimplant applications, but when implanted into the human body, these still contain some disadvantages, such as poor osteointegration (forming a fibrous capsule), wear debris and metal ion release, which often lead to clinical failure. Electrolytic hydroxyapatite/titanium dioxide (HA/TiO2) double layers were successfully deposited on titanium substrates in TiCl4 solution and subsequently in the mixed solution of Ca(NO3)2 and NH4H2PO4, respectively. After annealing at 300 degrees C for 1 h in the air, the coated specimens were evaluated by dynamic cyclic polarization tests, immersion tests, tensile tests, surface morphology observations, XRD analyses and cells culture. The adhesion strength of the HA coating were improved by the intermediate coating of TiO2 from 11.3 to 46.7 MPa. From cell culture and immersion test results, the HA/TiO2 coated specimens promoted not only cells differentiation, but also appeared more bioactive while maintaining non-toxicity. PMID:15880934

Lin, Chi-Min; Yen, Shiow-Kang

2004-11-01

388

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

PubMed

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

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

2007-02-01

389

Melt Spinning of Poly(lactic acid) and Hydroxyapatite Composite Fibers: Influence of the Filler Content on the Fiber Properties.  

PubMed

Composite fibers from poly(lactic acid) (PLA) and hydroxyapatite (HA) particles were prepared using melt spinning. Different loading concentrations of HA particles (i.e., 5, 10, 15, and 20 wt %) in the PLA fibers and solid-state draw ratios (SSDRs) were evaluated in order to investigate their influence on the fibers' morphology and thermal and mechanical properties. A scanning electron microscopy investigation indicated that the HA particles were homogeneously distributed in the PLA fibers. It was also revealed by atomic force microscopy and Fourier transform infrared spectroscopy that HA particles were located on the fiber surface, which is of importance for their intended application in biomedical textiles. Our results also suggest that the mechanical properties were independent of the loading concentration of the HA particles and that the SSDR played an important role in improving the mechanical properties of the composite fibers. PMID:23848437

Persson, Maria; Lorite, Gabriela S; Cho, Sung-Woo; Tuukkanen, Juha; Skrifvars, Mikael

2013-07-12

390

Bioactivated collagen-based scaffolds embedding protein-releasing biodegradable microspheres: tuning of protein release kinetics.  

PubMed

In tissue engineering, the recapitulation of natural sequences of signaling molecules, such as growth factors, as occurring in the native extracellular matrix (ECM), is fundamental to support the stepwise process of tissue regeneration. Among the manifold of tissue engineering strategies, a promising one is based on the creation of the chrono-programmed presentation of different signaling proteins. This approach is based upon the integration of biodegradable microspheres, loaded with suitable protein molecules, within scaffolds made of collagen and, in case, hyaluronic acid, which are two of the fundamental ECM constituents. However, for the design of bioactivated gel-like scaffolds the determination of release kinetics must be performed directly within the tissue engineering template. In this work, biodegradable poly(lactic-co-glycolic)acid (PLGA) microspheres were produced by the multiple emulsion-solvent evaporation technique and loaded with rhodamine-labelled bovine serum albumin (BSA-Rhod), a fluorescent model protein. The microdevices were dispersed in collagen gels and collagen-hyaluronic acid (HA) semi-interpenetrating networks (semi-IPNs). BSA-Rhod release kinetics were studied directly on single microspheres through confocal laser scanning microscopy (CLSM). To thoroughly investigate the mechanisms governing protein release from PLGA microspheres in gels, BSA-Rhod diffusion in gels was determined by fluorescence correlation spectroscopy (FCS), and water transport through the microsphere bulk was determined by dynamic vapor sorption (DVS). Moreover, the decrease of PLGA molecular weight and glass transition temperature (T(g)) were determined by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC), respectively. Results indicate that protein release kinetics and delivery onset strongly depend on the complex interplay between protein transport through the PLGA matrix and in the collagen-based release media, and water sequestration within the scaffolds, related to the scaffold hydrophilicity, which is dictated by HA content. The proper manipulation of all these features may thus allow the obtainment of a fine control over protein sequential delivery and release kinetics within tissue-engineering scaffolds. PMID:19449203

Biondi, Marco; Indolfi, Laura; Ungaro, Francesca; Quaglia, Fabiana; La Rotonda, Maria Immacolata; Netti, Paolo A

2009-05-18

391

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

392

A novel jet-based nano-hydroxyapatite patterning technique for osteoblast guidance  

PubMed Central

Surface topography is well known to play a crucial role in influencing cellular responses to an implant material and is therefore important in bone tissue regeneration. A novel jet-based patterning technique, template-assisted electrohydrodynamic atomization spraying, was recently devised to control precisely the surface structure as well as its dimensions. In the present study, a detailed investigation of this patterning process was carried out. A range of nano-hydroxyapatite (nHA) line-shaped patterns <20 µm in width were successfully deposited on a commercially pure Ti surface by controlling the flow of an nHA suspension in an electric field. In vitro studies showed that the nHA patterns generated are capable of regulating the human osteoblast cell attachment and orientation.

Li, Xiang; Koller, Garrit; Huang, Jie; Di Silvio, Lucy; Renton, Tara; Esat, Minoo; Bonfield, William; Edirisinghe, Mohan

2010-01-01

393

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

PubMed

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

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

2013-09-01

394

Novel phosphorus-containing cyclodextrin polymers and their affinity for calcium cations and hydroxyapatite.  

PubMed

Novel phosphorous-containing ?-cyclodextrin (?CD) polymers (CDP) were synthesized easily under "green chemistry" conditions. A simple polycondensation between the hydroxyl groups of ?CD and non-toxic sodium trimetaphosphate (STMP) under basic conditions led to soluble, non-reticulated CDPs with molecular weights (Mw) higher than 10(4)gmol(-1), the actual value depending on the NaOH:?CD and STMP:?CD weight ratios. The presence of both ?CD and phosphate groups in the polymer allows for strong interactions with amphiphilic probes, such as 1-adamantyl acetic acid, or with divalent cations, such as Ca(2+), whose strengths were characterized by isothermal titration microcalorimetry. The obtained phosphated compounds also display high affinity towards hydroxyapatite (HA), leading to HA nanoparticles that could easily be recovered by CDPs, as demonstrated by transmission electron microscopy and quantitative determination of the total amount of phosphated molecules fixed on HA. PMID:23987426

Wintgens, Véronique; Dalmas, Florent; Sébille, Bernard; Amiel, Catherine

2013-07-07

395

Reverse microemulsion-directed synthesis of hydroxyapatite nanoparticles under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Morphology controllable hydroxyapatite (HA) nanoparticles were synthesized using reverse microemulsion (aqueous solution/TX-100/n-butanol/cyclohexane) systems under hydrothermal conditions. The concentration of cetyltrimethylammonium bromide (CTAB) contained in the aqueous solution and pH value had significant effect on the morphology and crystal phases of the final products. All the as-synthesized HA nanoparticles had a larger a value but smaller c value compared with the standard values of the JCPDs card. The existence of CTAB could be attributed to the growth of HA along an axis, but inhibit the growth along the c-axis to some extent. A proposed model was established to explain the change of the lattice parameters.

Sun, Yuxiu; Guo, Guangsheng; Tao, Dongliang; Wang, Zhihua

2007-03-01

396

Experimental Analysis of Spray Dryer Used in Hydroxyapatite Thermal Spray Powder  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

397

Formation of Hydroxyapatite Coating on Anodic Titanium Dioxide Nanotubes via an Efficient Dipping Treatment  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HA) depositions on metallic biomedical implants have been widely applied to generate bioactive surfaces in simulated biological environments. Meanwhile, highly ordered TiO2 nanotubes obtained via anodization have attracted increasing interest for biomedical applications. However, the capability to grow HA coating on TiO2 nanotubes at room temperature remains problematic. In this study, we applied a dipping treatment for biomimetic formation of an adhesive HA coating on titanium dioxide nanotubes. The coatings formed using this procedure did not require high-temperature annealing or high supersaturation of the simulated biological condition. The as-formed TiO2 nanotubes on titanium were treated using several dip-and-dry steps, through which the TiO2 nanotubes were filled and covered with calcium phosphate nucleation sites. The specimens readily grew HA once immersed in the original simulated biological fluid (SBF) after little more than 12 hours. The carbonated HA coating was formed with 10- ?m thickness after 4 days of immersion, while only a few calcium phosphate particles were observed on annealing TiO2 nanotubes immersed in the same solution for the same duration. Tensile testing showed that the bonding strength between HA coating and substrate was 27.2 ± 1.6 MPa. This treatment dramatically improved efficiency for promoting HA formation on anodic TiO2 nanotubes at room temperature.

Wang, Lu-Ning; Luo, Jing-Li

2011-11-01

398

Controlled RGD Peptide Adsorption on Aggregation-Free, Size-Selected Hydroxyapatite Nanoparticle Substrates  

NASA Astrophysics Data System (ADS)

Numerous studies of cell attachment, differentiation, and proliferation have been carried out on nanostructured hydroxyapatite (HA) surfaces with cell adhesive peptides containing the RGD (Arg-Gly-Asp) motif. Although these studies have yielded useful insights into the role of RGD peptides in cell-HA biomaterial interactions, the heterogeneity of typical nanophase HA materials makes it difficult to decouple the effects of nanotopography and biochemical cues. In this work we have used aggregation-free, size-controlled HA nanoparticles with mean size in the 20-70 nm range, synthesized by gas-phase laser ablation and deposited on atomically flat bioinert substrates that may help overcome this challenge. Nanoparticle deposits with adjustable number concentration were characterized by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. RGD peptides modified by the addition of a polyglutamate sequence and a fluorescent conjugate, were coated onto the HA nanoparticle substrates. Intensity histograms of fluorescent microscopy images show that peptide adsorption on the substrates scales with the concentration of HA nanoparticles. High HA nanoparticle concentrations also lead to peptide clustering tunable in the 100-1200 cm-2.

Bapat, Parimal; Culpepper, Bonnie; Bellis, Susan; Camata, Renato

2012-10-01

399

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

PubMed

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

Sopyan, I; Fadli, A; Mel, M

2011-11-26

400

NLRP3 inflammasome plays a critical role in the pathogenesis of hydroxyapatite-associated arthropathy  

PubMed Central

The proinflammatory and catabolic cytokine IL-1? has been implicated in the pathogenesis of osteoarthritis (OA) by mediating synovial inflammation and cartilage degeneration. Although synovial macrophages are suggested to be the source of IL-1?, the mechanism remains unclear. Ectopic deposition of hydroxyapatite (HA) crystals in joints is closely associated with OA and other arthropathies, but the precise role of HA in arthritis pathogenesis has not been clearly demonstrated. Here we show that HA crystals of a particular size and shape can stimulate robust secretion of proinflammatory cytokines IL-1? and IL-18 from murine macrophages in a NLRP3 inflammasome-dependent manner. HA-induced inflammasome activation is dependent on potassium efflux, generation of reactive oxygen species (ROS), and lysosomal damage, but independent of cell death. Mice lacking the inflammasome components are protected against HA-induced neutrophilic inflammation in the air-pouch model of synovitis, and they show decreased joint pathology accompanying spontaneous HA deposition in the ank-deficient mouse model of arthritis. Moreover, calcium crystal positive synovial fluids from some OA patients exhibited inflammasome-stimulatory activity in vitro. These results demonstrate that the NLRP3 inflammasome mediates the pathological effect of HA crystals in vitro and in vivo and suggest a critical role for the inflammasome in the pathogenesis of OA.

Jin, Chengcheng; Frayssinet, Patrick; Pelker, Richard; Cwirka, Diane; Hu, Bo; Vignery, Agnes; Eisenbarth, Stephanie C.; Flavell, Richard A.

2011-01-01

401

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

402

Enrichment and Characterization of Histones by 2D-Hydroxyapatite/Reversed-Phase Liquid Chromatography Mass Spectrometry  

PubMed Central

Here we report a novel two-dimensional LC-MS method that combines offline hydroxyapatite (HA) chromatography with online reversed-phase liquid chromatography mass spectrometry (HA/RP LC-MS). The 2D-LC-MS method was used to enrich and characterize histones and their posttranslational modifications. The 2D HA/RP LC-MS approach separates histones based on their relative binding affinity to DNA and relative hydrophobicity. HA/RP separations showed improvement in the number of histone isoforms detected as compared with 1D reversed-phase LC-MS of acid extracted histones. The improved histone fractionation resulted in better detection of lower abundant histone variants as well as their posttranslationally modified isoforms. Histones eluted from the HA/RP in the following order: H1, H2A/H2B heterodimers followed by H3/H4 heterotetramers, as predicted from their spatial organization in nucleosomes for binding affinity to DNA. Comparison between HA purified and acid-extracted histones revealed similar histone profiles with the exception that the HA fractions showed a greater number of H1 isoforms. Two elution conditions were also examined: batch elution and salt-gradient elution. While both elution techniques were able to sufficiently fractionate the histones, the salt-gradient approach has the most potential for purification of selected histone isoforms.

Su, Xiaodan; Jacob, Naduparambil K.; Amunugama, Ravindra; Hsu, Pang-Hung; Fishel, Richard; Freitas, Michael A.

2009-01-01

403

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

PubMed

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

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

2012-07-23

404

Osteoblast proliferation on hydroxyapatite coated substrates prepared by right angle magnetron sputtering.  

PubMed

The preparation of hydroxyapatite (HA) coatings via a versatile right-angle magnetron sputtering (RAMS) approach for use as a biomaterial has recently been reported. RAMS coatings show some advantages over conventionally sputtered films in that room temperature deposition yields nanocrystalline and nearly stoichiometric HA coatings under appropriate conditions, thereby avoiding the troublesome post deposition annealing treatment. In this article, we present an exploratory study of the biocompatibility of RAMS HA coatings deposited on metallic substrates. RAMS HA coatings with a thickness around 500nm were prepared on various substrates. X-ray diffraction (XRD) analysis showed that the as-deposited HA coatings were polycrystalline with some strongly preferred orientations. Atomic force microscopy (AFM) results showed that the coatings were rather smooth with surface roughness on the order of 10 nm. X-ray photoelectron spectroscopy (XPS) confirmed that the surface chemistry was nearly stoichiometric. To study the biocompatibility of these coatings, murine pre-osteoblastic MC3T3-E1 cells were seeded onto various substrates. Cell density counts using fluorescence microscopy showed that the best osteoblast proliferation is achieved on an HA RAMS-coated titanium substrate. Additionally, in preliminary studies the influence of Zn, Mg, and Al incorporation in the HA crystal lattice on the in vitro behavior was also evaluated. These experiments demonstrate that RAMS is a promising coating technique for biomedical applications. PMID:19705463

Hong, Zhendong; Mello, Alexandre; Yoshida, Tomohiko; Luan, Lan; Stern, Paula H; Rossi, Alexandre; Ellis, Don E; Ketterson, John B

2010-06-01

405

Electrophoretic deposition of hydroxyapatite-CaSiO3-chitosan composite coatings.  

PubMed

Electrophoretic deposition (EPD) method has been developed for the fabrication of hydroxyapatite (HA)-CaSiO(3) (CS)-chitosan composite coatings for biomedical applications. The use of chitosan enabled the co-deposition of HA and CS particles and offered the advantage of room temperature processing of composite materials. The coating composition was varied by the variation of HA and CS concentrations in the chitosan solutions. Cathodic deposits were obtained as HA-CS-chitosan monolayers, HA-chitosan/chitosan multilayers or functionally graded materials (FGM) containing HA-chitosan and CS-chitosan layers of different composition. The thickness of the individual layers was varied in the range of 0.1-20 microm. The deposition yield was studied at different experimental conditions and compared with the results of modeling. It was shown that the moving boundary model for the two component system can explain the non-linear increase in the deposition yield with increasing HA concentration in chitosan solutions. The obtained coatings were studied by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed that these coatings provided corrosion protection of stainless steel substrates in Ringer's physiological solution. The deposition mechanism and kinetics of deposition have been discussed. PMID:19012892

Pang, Xin; Casagrande, Travis; Zhitomirsky, Igor

2008-10-31

406

Preparation and characterization of nano-hydroxyapatite/silk fibroin porous scaffolds.  

PubMed

Novel tissue engineering scaffold materials of nano-hydroxyapatite (nHA)/silk fibroin (SF) biocomposite were prepared by freeze-drying. The needle-like nHA crystals of about 10 nm in diameter by 50-80 nm in length, which were uniformly distributed in the porous nHA/SF scaffolds, were prepared by a co-precipitation method with a size. The as-prepared nHA/SF scaffolds showed good homogeneity, interconnected pores and high porosity. XRD and FT-IR analysis suggested that the silk fibroin was in beta-sheet structure, which usually provides outstanding mechanical properties for silk materials. In this work, composite scaffolds containing as high as 70% (w/w) nHA were prepared, which had excellent compressive modulus and strength, higher than the scaffolds at low nHA content level and other porous biodegradable polymeric scaffolds often considered in bone-related tissue engineering reported previously. The cell compatibility of composite scaffolds was evaluated through cell viability by MTT assay. All these results indicated that these nHA/SF scaffold materials may be a promising biomaterial for bone tissue engineering. PMID:18325234

Liu, Lin; Liu, Jinying; Wang, Mingqi; Min, Sijia; Cai, Yurong; Zhu, Liangjun; Yao, Juming

2008-01-01

407

Controlled growth and kinetics of porous hydroxyapatite spheres by a template-directed method  

NASA Astrophysics Data System (ADS)

Porous hydroxyapatite (HA) spheres with high purity of phase and well-controlled pore size were grown by a template-directed method. We studied for the initial concentration of Ca P how to control the chemical component of the products, and for the concentration of template how to control the aperture and the morphology of porous HA spheres. The experimental results indicated that the lower concentration of Ca P was prone to pure HA phase and the aperture decreased gradually with the increase of the concentration of template. Correspondingly, the crystallization thermodynamics and template-directed growth kinetics were discussed in details. The solubility isotherms of HA and dicalcium phosphate (DCPD) were calculated based on classical crystallization theories of thermodynamics. The results suggested that there was a critical concentration of P=0.048M in the case of Ca:P=5:3 and thus DCPD could be avoided only when P?0.048M in this given reaction system. Kinetic analysis of HA crystal growth revealed that the template depressed the interfacial potential energy E, then enhanced the roughness on the surface of crystal nucleus and directed HA crystal to selectively grow along the [0 0 0 1] direction, and consequently governed the aperture of porous HA spheres. The experimental results were in agreement with the theoretical analysis.

He, Qian Jun; Huang, Zhi Liang

2007-03-01

408

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

PubMed

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

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

2013-08-31

409

Interaction of hydroxyapatite-titanium at elevated temperature in vacuum environment.  

PubMed

In this study, the interaction between hydroxyapatite (HA) and titanium (Ti) at elevated temperature in vacuum environment was investigated. The 80 wt% HA-20 wt% Ti powder mixtures and 90 wt% HA-10 wt% Ti powder mixtures were dry pressed and heat-treated at 1100 degrees C in vacuum environment. HA powders and the commercially pure Ti powders were used as controls. The heat-treated samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscope (SEM) and energy disperse spectra. XRD and SEM indicated densification of metallic Ti specimens during the in-vacuum heat treatment. Heat treatment of HA specimens in vacuum resulted in the loss of hydroxyl groups as well the formation of a secondary beta-tricalcium phosphate phase. Metallic Ti was not observed in the in-vacuum heat-treated HA-Ti specimens. However, alpha-tricalcium phosphate, tetracalcium phosphate and calcium titanium oxide were observed for the in-vacuum heat-treated HA-Ti specimens. It was concluded that the in-vacuum heat-treatment process completely converted the metal-ceramics composites to ceramic composites. PMID:14967524

Yang, Yunzhi; Kim, Kyo-Han; Agrawal, C Mauli; Ong, Joo L

2004-07-01

410

Batch Procedure for Thermal Elution of DNA from Hydroxyapatite.  

National Technical Information Service (NTIS)

Thermal elution of reassociated DNA on hydroxyapatite columns is time-consuming because it is difficult to run more than two samples simultaneously. A batchwise hydroxyapatite thermal elution method that allows simultaneous handling of up to ten samples i...

D. J. Brenner G. R. Fanning A. V. Rake K. E. Johnson

1968-01-01

411

Microsphere estimates of blood flow: Methodological considerations  

SciTech Connect

The microsphere technique is a standard method for measuring blood flow in experimental animals. Sporadic reports have appeared outlining the limitations of this method. In this study the authors have systematically assessed the effect of blood withdrawals for reference sampling, microsphere numbers, and anesthesia on blood flow estimates using radioactive microspheres in dogs. Experiments were performed on 18 conscious and 12 anesthetized dogs. Four blood flow estimates were performed over 120 min using 1 {times} 10{sup 6} microspheres each time. The effects of excessive numbers of microspheres pentobarbital sodium anesthesia, and replacement of volume loss for reference samples