Characterization of biomimetic calcium phosphate on phosphorylated chitosan films

This study examined the effect of chitosan degree of deacetylation (DDA), concentration of simulated body fluid (SBF), and mineralization time on the composition, structure, and crystallinity of calcium phosphate (CaP) biomimetically deposited on chitosan and on osteoblast cell growth. Phosphorylated chitosan films of 92.3%, 87.4%, and 80.6% DDA were soaked in SBF (1.0x or 1.5x) for 7, 14, or 21 days. Scanning electron microscopy revealed that CaP precipitated from 1.5x SBF had a porous, granular morphology; while the coatings precipitated in 1.0x SBF were smoother and more uniform. X-ray diffraction showed that films mineralized in 1.0x SBF were amorphous, while films mineralized in 1.5x SBF for 21 days exhibited crystalline peaks similar to hydroxyapatite, with the most crystalline peaks seen on 92.3% DDA chitosan. When mineralized films were placed in cell media for 14 days, more calcium phosphate precipitated onto all films, and the most calcium phosphate was found on 92.3% DDA films mineralized in 1.5x SBF. After seven days of osteoblast culture, there were approximately three times as many cells (based on DNA measurements, p < 0.05) on 92.3% DDA films soaked in 1.0x SBF for seven or 21 days than on 80.6% DDA films soaked in 1.0x SBF for any length of time or any films soaked in 1.5x SBF. The DDA of chitosan, concentration of SBF and mineralization time affect the structure of and biological response to chitosan/biomimetic CaP films, and these factors must be considered when designing new materials to be used in orthopaedic and dental/craniofacial implant applications.