The Synthesis, Structure, and Features of Biocomposites Based on Selenite-Substituted Hydroxyapatite and Collagen

Materials based on selenite-substituted hydroxyapatite and collagen were synthesized. Chemical analysis of solutions after precipitate separation confirmed the substitution of phosphate ions by selenite ions in the hydroxyapatite structure. Results of elemental analysis, X-ray phase analysis (XRD), and infrared spectroscopy (IR) verified these substitutions in the hydroxyapatite structure. Morphological studies revealed a trend of increasing aggregate size with higher concentrations of selenite ions and collagen. Scanning probe microscopy showed that samples with selenite ions exhibited greater surface roughness compared to collagen-containing samples. The BET (Brunauer-Emmett-Teller) method provided specific surface area measurements of synthesized powders. The highest values were recorded for samples with 10.0 g/L selenite ions, while the lowest were for collagen-containing materials. Resorption studies in TRIS-buffer (pH 7.40) and simulated body fluid (SBF) demonstrated increased dissolution rates for samples with high selenite ion content. Collagen addition reduced dissolution rates. Thermal analysis (200–800°C) identified the sample with lowest selenite ion concentration (1.5 g/L) as most thermally stable.