Composition and structure of the apatite formed on PET substrates in SBF modified with various ionic activity products

Abstract

An apatite layer was formed on polyethyleneterephthalate (PET) substrates by the following biomimetic process. PET substrates were placed on granular particles of a CaO-SiO2-based glass in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma to form apatite nuclei on their surfaces (first treatment). They then were soaked in modified SBFs, the ion concentrations of which were changed to give a variation in ionic activity product of apatite (IP), in order to make the apatite nuclei grow (second treatment). The Ca/P atomic ratio and the lattice constant c of the formed apatite decreased from 1.54 to 1.40 and from 6.880 to 6.838 A, respectively, with increasing ion concentrations from 0.75 to 2.00 times those of SBF, that is, with increasing IP from 10(-96.6) to 10(-91.9). This was attributed to an increase in the concentration of HPO4(2-) ion substituting for the PO4(3-) ion sites, which gave an increase in the Ca2+ in the apatite. Even the apatite formed in 1.00 SBF showed a Ca/P ratio of 1.51 and lattice constants a of 9.432 A and c of 6.870 A. The Ca/P ratio and lattice constant c were smaller and the lattice constant a was larger than those of the bone apatite; its Ca/P ratio and its lattice constants a and c, were 1.65, 9.419 A, and 6.88 A, respectively. This was attributed to the lower content (2.64 wt%) of the CO3(2-) ion substituting for the PO4(3-) ion sites of the apatite compared to that of the bone apatite (5.80 wt%). The lower content of the CO3(2-) ion in the apatite might be caused by the lower concentration of HCO3- ion in 1.00 SBF compared to that in human blood plasma.

Direct and Rapid Quantification of Calcium Phosphate Precipitate on Titanium by X-Ray Fluorescence Analysis Using Fundamental Parameter Method

“…34,35) Moreover, it has been reported that small amount of CO 3 2¹ ions, which is a constituent of the simulated-body fluid, substitute for PO 4 3¹ sites, resulting in Ca 2+ deficiency form. 36,37) As a result, the value of the [Ca]/[P] ratio obtained by ICP-OES was estimated to be lower than that of the stoichiometric value.…”

Biocompatibility, Bioactivity and Mechanical Properties of Portland Cement and Portland Cement-Metakaolin Blends for Bone Tissue Engineering Applications

“…Ceramics tend to be brittle, present low mechanical strength (in a porous configuration), and unpredictable in vivo degradation/dissolution rates [1,2,6,7]. Polymers on the other hand show reduced osseointegration capabilities, decreased cell-material interactions due to surface hydrophobicity, and excessive ductility for hard tissue replacement applications [1,2,8]. Recent research has been highly focused on the development of polymer-ceramic nanocomposites [1].…”

P(EMA-co-HEA)/SiO2 hybrid nanocomposites for guided dentin tissue regeneration: structure, characterization and bioactivity.

“…This means that the in vivo bone-bonding ability of a given material can be predicted, before animal testing, from the apatite formation on its surface when subjected to this test. Usually, the apatite formed in SBF is carbonate-containing hydroxyapatite similar to bone in composition and structure, but with lower carbonate content than that in the apatite crystals formed in dentin [1] (5.7 wt%) and thus with lower Ca/P molar ratio, which has been attributed to the lower concentration of HCO 3 -ions [54] . The ionic activity product IP of the apatite in an aqueous solution is given by [40,54] : …”

“…This increases the ionic activity product of the apatite while maintaining the Ca/P molar ratio, and thereby make the apatite nuclei grow more rapidly (growth stage) [54,60,61] . Table 1.1 shows the ion concentrations and the ionic activity products of the apatite in 2×SBF.…”

“…Once nucleation occurs, i.e., the surface is already pre-calcified, the glass is not needed and apatite nuclei grow spontaneously on the substrate to form an apatite layer by consuming calcium and phosphate ions from the SBF. Kim et al [54] and Tanahashi et al [61] performed similar experiments on polymeric substrates with different sources of nucleating agents. The latter observed that the adhesive strength of the apatite layer to the substrate varied largely with the kind of polymers.…”