Surface modification of nanophase hydroxyapatite with chitosan

Nanophase hydroxyapatite (HAp) particles were aged in 0–2.5 wt.% chitosan acetate solutions for 30 days to evaluate the influence of chitosan on HAp surface chemistry. The HAp characterization results from Fourier transform infra-red spectroscopy (FTIR), thermal gravimetric analysis (TGA), Carbon–Hydrogen–Nitrogen (CHN) analysis, and BET N₂ adsorption revealed measurable changes in the HAp surface chemistry after aging in the chitosan acetate solutions. The TGA mass loss exhibited by HAp increased from 3.3–6.5 mass% as the chitosan acetate gel concentration increased from 0–2.5 mass%. The CHN analysis revealed an increase in C and H contents with increasing chitosan acetate concentration while the N concentration remained relatively constant (0.30–0.32 mass%). Chitosan interactions with HAp caused an increase in specific surface area from 85 m²/g up to 160 m²/g for HAp aged in 1.5 mass% chitosan acetate solution (HAp1.5]). Chitosan exhibits strong adsorption interactions with HAp and enhances colloid stability for processing of chitosan/hydroxyapatite nanocomposites.