Surface modification of zirconia substrate by silicon-substituted hydroxyapatite coating for enhanced bioactivity

In this study, the surface of zirconia (ZrO2) substrates was modified by the combination of plasma treatment and coating with silicon-substituted hydroxyapatite (Si-HA) sols, comprising an expected theoretical Si content of 0 (Si-HA0), 1.70 (Si-HA1), 3.44 (Si-HA2), and 7.01 wt % (Si-HA4) for improving the biological performance of substrate. The Si-HA-coating layers were successfully deposited on the ZrO2 substrate surface. These coating layers exhibited a three-dimensional interconnected microporous structure and a single-phase crystal owing to HA, implying that the Si content hardly affects the phase composition and microstructure of the coating layers. The dissolution rate of the Si-HA coating layers in deionized water increased with the Si content, which affected the proliferation of mouse calvaria pre-osteoblasts (MC3T3-E1). Cytocompatibility test results revealed that Zr-Si-HA2 substrate, which was coated with Si-HA2, promoted the proliferation and differentiation of MC3T3-E1 more rapidly than the other substrates. These results revealed that Zr-Si-HA substrates are ideal biomaterials for bone tissue engineering.