MONITORING THE INTERACTION OF SYNTHETIC HYDROXYAPATITES UNDER VARIED IN VITRO TEST CONDITIONS

The experimental work focuses on the detailed monitoring of the interaction of commercial hydroxyapatite (HA) granules with various morphologies and surfaces with simulated body fluid (SBF) under varied in vitro test conditions. The ISO 23317:2014 standard, which specifies methods for the detection of apatite formation on the surface of materials in a simulated body fluid, mainly focuses on one-piece samples (tablets, rectangular shaped samples) under static conditions. The SBF solution modelling the inorganic part of blood plasma is buffered with a Tris buffer which can, under certain conditions, affect the in vitro test results by its own interaction with the tested material. Changes on the surfaces of the tested bioceramic granules with varied porosity and leachates from the buffered and unbuffered SBF solutions were characterised at selected time intervals using the available methods (SEM, BET, AAS, UV-VIS). The kinetics of the formation and morphology of the precipitated hydroxyapatite (HAp) was found to vary under different in vitro test conditions. The leachates from the solutions confirmed different rates of calcium and phosphate ions depletion, especially at the beginning of the assay. The pH analyses of the buffered and unbuffered SBF solutions also showed a Tris buffer effect.