Hydroxyapatite Ceramic Particles Research Articles

Anodization of a Medical-Grade Ti-6Al-7Nb Alloy in a Ca(H2PO2)2-Hydroxyapatite Suspension

The electrochemical parameters used for surface treatments should be individually determined for each titanium alloy. In this paper, the parameters for the anodization of a medical-grade Ti-6Al-7Nb alloy in hydroxyapatite suspensions were determined. It was found that formation of a favorable porous oxide layer occurred for the plasma electrolytic oxidation process in a Ca(H2PO2)2 solution with 150 g/dm3 hydroxyapatite particles at 350 V and 450 V. The differences in the morphology, chemical and phase composition caused variability in the average surface roughness (up 4.25 μm) and contact angle (strongly hydrophilic) values. Incorporation of the hydroxyapatite ceramic particles into formed TiO2 layer also influenced the layer thickness and adhesion of the layers to the substrate. The oxide layers formed on the Ti-6Al-7Nb alloy were between 5.19 and 31.4 μm in thickness with an average range of approximately 8–15 μm. The formation of a ceramic layer under controlled electrochemical parameters allows the design of a bioactive surface of implants for bone tissue. The hydroxyapatite particles may promote the osseointegration process. Thus, in this study, the formation of ceramic composites on medical-grade Ti surfaces is presented and discussed.

Study on the enhanced protein adsorption of microwave sintered hydroxyapatite nanoceramic particles: Role of microstructure

Currently, nanobioceramics have received much attention due to their potentially high biological performance. In the present study, the interactions between proteins and two types of hydroxyapatite (HA) ceramic particles with distinct microstructures were studied in vitro. Protein adsorption on the microwave sintered and conventionally sintered HA ceramic particles (named as HAMS and HACS, respectively) were carried out in simulated body fluid (SBF) containing model proteins or rat serum and then subjected to protein quantitative evaluation, SDS-PAGE, and Western blotting analysis. The ceramic particles were characterized by nitrogen sorption, Hg penetration, zeta potential, and solubility analysis. It was found that HAMS with nanosized crystallites had greater specific surface area and pore volume and wider pore size distribution ranging from 0.02 to 2 μm than HACS. Although bovine serum albumin and lysozyme have different electrical properties in SBF, both the model proteins showed higher adsorption amounts per gram solid on HAMS than HACS, as could be ascribed to the contribution of the micropores structure of HAMS. Similarly, HAMS adsorbed more serum proteins per gram solid than HACS when incubating in rat serum, and here the surfaces of both particles were almost completely covered by serum proteins, leading to almost the same protein adsorption amounts per unit area solid of HAMS and HACS. SDS-PAGE patterns proved that HA ceramic particles had different binding capacities for different serum proteins and was not highly dependent on the concentrations of the competing protein components present in rat serum. Western blotting analysis confirmed the enhanced adsorption of fibronectin and vitronectin on HAMS, indicating that HAMS might have better bioactivity than HACS.

Effect of Sintering Processes on Surface Properties and Protein Adsorption of Hydroxyapatite Ceramic Particles

Two types of hydroxyapatite(HA) ceramic particles were respectively fabricated by conventional and microwave sintering processes.The conventionally sintered HA was abbreviated as HACS,and the microwave sintered one was HAMS.The phase compositions,surface morphologies and zeta potentials of both particles were respectively analyzed with X-ray diffraction(XRD),scanning electron microscope(SEM) and zetasizer.Bovine serum albumin(BSA) and lysozyme(LSZ) were selected as models to study their adsorption behaviors on HACS and HAMS.Results confirm that both HA particles crystallize completely,but HACS has larger crystal grain size than HAMS.Although both HACS and HAMS show negative surface zeta potentials in phosphate buffered saline(PBS,pH 7.4),the former has higher absolute value than the latter.Besides,both HA particles exhibit different adsorption ability for BSA and LSZ,and HACS adsorbs fewer BSA but more LSZ than HAMS.The microwave sintering can be a good method to produce nano-HA ceramics with excellent bioactivity.

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

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%.

Contribution of Surface Charge to Bovine Serum Albumin Adsorption on Hydroxyapatite Ceramic Particles

Protein adsorption is driven by various interactions. The contribution of surface charge to bovine serum albumin (BSA) adsorption on hydroxyapatite (HA) ceramic was investigated by adjusting the liquid environment in which the solid particles dispersed. Zeta potentials of HA and the adsorption of BSA on the surface were tested as a function of pH, ionic strength, Ca2+ and PO4 3- concentrations in the aqueous solutions, and the results showed that both of them were greatly affected by those experimental variations. Besides, the amount of adsorbed BSA was related to the variation of zeta potential of HA, as could be well understood in terms of electrostatic interactions.

Hydroxyapatite Ceramic Particles as Material for Transfection

Hydroxyapatite Ceramic Particles as Material for Transfection

Hydroxyapatite-based porous aggregates: physico-chemical nature, structure, texture and architecture

At the request of medical teams from the maxillofacial sector, a highly porous ceramic support based on hydroxyapatite of around 70–80% porosity was produced with a pore size distribution similar to bone texture (< 10 μm, ∼3vol%; 10–150 μm, ∼110 vol%; > 150 μm, ∼86 vol%). The ceramic substrates were conceived not only as a fillers for bone cavities, but also for use as drug dispensers and as supports to host cells to produce particular therapeutic agents. A method is suggested to obtain a substrate of high porosity, exploiting the impregnation of spongy substrate with hydroxyapatite ceramic particles. X-ray and scanning electron microscopy analyses were carried out to evaluate the nature of the new ceramic support in comparison with the most common commercial product; pore size distribution and porosity were controlled to known hydroxyapatite ceramic architecture for the different possible uses.

Tensile strength of the interface between hydroxyapatite and bone.

Tensile strength of the interface between hydroxyapatite (HA) and bone was tested. Scanning electron microscopy was used to observe the tensile failure mode and the morphological change of hydroxyapatite ceramic surface in bone. The porosity of hydroxyapatite is 14% and pore size less than 2 microns. After 2 weeks of implantation, the tensile strength of the interface is 0.72 MPa. After 4, 8, and 16 weeks, the average tensile strength stayed at 1.5 MPa. SEM showed that tensile failure occurred at the HA-bone interface at the second week, but after 4 weeks, the failure occurred between HA particles within the bulk, and not at the HA-bone interface. Calcified tissue was directly deposited on the HA ceramic surface and exits also in the micropores. Near the interface, sintered necks among HA ceramic particles were subjected to biodegradation.

Experimental animal investigation of bone regeneration with collagen-apatite.

Multicentric osteoregeneration is a new principle of osteoinduction [31a] which can be realized with the combination of collagen and fine dispersed hydroxyapatite ceramic particles (Collapat). This was histomorphometrically proved in the present study involving 14 rabbits with 28 6-mm-wide bore holes in the distal femoral condyles. With Collapat, an average of 5 times more new bone was regenerated than in the control defects without implant. The Wilcoxon matched-pairs signed-ranks test proved the positive effect of the implant Collapat on osteoregeneration with a significance of P less than 0.0001. At sites of Collapat insertion bone regeneration begins in the 2nd week, reaches its climax in the 3rd week, and is completed after the 4th week. in the course of development the histological picture is typified by a lively bone remodeling. Bone formation can be recognized in direct contact to the apatite granules. Foreign body or allergic reactions are not observed. Remodeling of the bone is not hindered by the slowly resorbable apatite granules. About 250 human implantations have been performed in our hospital since 1979, with good results and no negative effects.