In vitro biological activity of Zn substituted hydroxyapatite/polyvinyl alcohol composite for orthopaedic applications

Zinc substituted hydroxyapatite (Zn-HAP) Ca5-xZnx(PO4)(3)OH (x = 0, 0.05, 0.2 and 1.0) was synthesized by hydrothermal method. Different weight ratio (30:70, 50:50 and 70:30) of polymer composite (parent HAP and Zn-HAP/PVA (poly vinyl alcohol)) were prepared by solvent casting method. The developed parent and Zn-HAP/PVA composites were characterized by XRD, FTIR and SEM-EDAX to examine the phase composition, functional groups and morphology. Porosity, swelling percentage, mechanical strength, antibacterial activity, hemocompatibility, bioactivity and cytotoxicity were studied. Increase in porosity (88.90 +/- 1.20-97.25 +/- 1.12 %) and mechanical strength (44.45-98.94 MPa) were observed with the increase in the wt% of Zn-HAP in the PVA network. Furthermore, In-vitro hemocompatibility assay showed that all composites were hemocompatible with less than 2% hemolytic ratio. In-vitro biomineralization of the optimized composite (Zn-HAP/PVA with 30:70 (w/w)) showed a new apatite formation on the surface of the composite after soaking in simulated body fluid (SBF) for 28 days. Further, the cytotoxicity of the optimized composite was evaluated against human osteoblast cells (HOS). Zn-HAP/PVA with 30:70 was found to have higher cell viability (p < 0.01) compared to the pure (HAP/PVA) composite.

Automated summary

Zinc substituted hydroxyapatite (Zn-HAP) with different weight ratios of polymer composite was synthesized and characterized. The increase in zinc content led to higher porosity and mechanical strength in the composite materials, while maintaining excellent biocompatibility and bioactivity.