The effect of biomimetic apatite structure on osteoblast viability, proliferation, and gene expression.

The conventional biomimetic apatite coating process can be accelerated by immersing substrates into concentrated simulated body fluid (5 x SBF) at 37 degrees C to form an initial coating of apatite precursor spheres, and transform the precursors into plate-like apatite structures. Depending on processing parameters, different apatite structures can be created over the same substrate. The purpose of this study is to investigate the effects of the different apatite microenvironment on cell spreading, viability, proliferation, and gene expression. MC3T3-E1 preosteoblasts were cultured on five surfaces: conventional apatite (CA), precursor apatite spheres (PreA), large plate-like apatites (LgA), small plate-like apatites (SmA), and tissue culture grade polystyrene (TCPS). PreA induced significantly higher cell death during the first two weeks. TCPS supported more uniform spreading (1 day) and higher proliferation (2 weeks) than CA, LgA, and SmA. Apatites restricted spreading and promoted the extension of cellular projections along the textured surfaces under confocal microscopy observation. By 3 weeks, LgA induced highest expression of mature osteogenic markers osteocalcin (OCN) and bone sialoprotein (BSP) in both regular and osteogenic culture media based on quantitative real-time RT-PCR. The results of this study suggest differential cell responses to subtle changes in apatite microenvironment.

Physiochemical characterization of cardiovascular calcified deposits. I. Isolation, purification and instrumental analysis.

Calcified human aortic atherosclerotic deposits and calf ventricular assist device bioprosthetic deposits were isolated and deproteinated by hydrazine treatment. Detailed chemical and instrumental analyses were applied to gain comprehensive physicochemical information which makes possible establishing compositional and structural similarities between the 2 types of pathologic mineral deposits which form on different host surfaces. These microcrystalline deposit materials are morphologically very heterogeneous and can be represented chemically as carbonate substituted apatite which, in some of its properties, significantly differs from hydroxyapatite. It is indicated that the mechanism for the formation of cardiovascular deposits proceeds through hydrolysis of octacalcium phosphate precursor.

Prediction of apatite lattice constants from their constituent elemental radii and artificial intelligence methods.

Lattice constants (LCs) of all possible 96 apatite compounds, A(5)(BO(4))(3)C, constituted by A[double bond]Ba(2+), Ca(2+), Cd(2+), Pb(2+), Sr(2+), Mn(2+); B[double bond]As(5+), Cr(5+), P(5+), V(5+); and C[double bond]F(1-), Cl(1-), Br(1-), OH(1-), are predicted from their elemental ionic radii, using pattern recognition (PR) and artificial neural networks (ANN) techniques. In particular, by a PR study it is demonstrated that ionic radii predominantly govern the LCs of apatites. Furthermore, by using ANN techniques, prediction models of LCs a and c are developed, which reproduce well the measured LCs (R(2)=0.98). All the literature reported on 30 pure and 22 mixed apatite compounds are collected and used in the present work. LCs of all possible 66 new apatites (assuming they exist) are estimated by the developed ANN models. These proposed new apatites may be of interest to biomedical research especially in the design of new apatite biomaterials for bone remodeling. Similarly these techniques may also be applied in the study of interface growth behaviors involving other biomaterials.

Thermal decomposition of developing enamel.

The decomposition of forming, maturing, and mature enamel was studied between room temperature and 1,000 degrees C by powder X-ray diffraction and infrared absorption methods. In mature dental enamel, carbonate decomposition proceeds relatively fast until 500 degrees C and at a slower rate beyond it. In forming and maturing enamel, decomposition is faster and is completed around 800 degrees C. The formation of beta-Ca3(PO4)2 is observed in dental enamel at 500 degrees C. At 1,000 degrees C, the apatite phase in forming and maturing enamel transforms almost completely to beta-Ca3(PO4)2, whereas in mature enamel, even at 1,000 degrees C, only partial decomposition occurs. Infrared results show the appearance in dental enamel of (1) A-type carbonate at room temperature and in the 500-900 degrees C range, in addition to the commonly observed B-type carbonate, and (2) intermediate CO2 molecules during carbonate decomposition (200-500 degrees C).