Developing a deposited calcium-phosphate layer on zirconia surface by chemical grafting of L-Serine molecules

Due to the proper mechanical properties and desirable aesthetic properties of zirconia, it is considered as a good candidate for replacement of metallic implants. In this study, zirconia was functionalized by l-serine amino acid to provide surface COOH/OH groups for calcium-phosphate formation (CPF) of hydroxyapatite and chemical bonding to bone tissue following implantation. Magnesia-partially stabilized zirconia (Mg-PSZ) discs were prepared and hydroxylated using hydrothermal process at 120 °C for different times to provide reactive hydroxyl groups. Thereafter, the discs were immersed in 0.01 mg/mL aqueous l-Serine solution at temperatures between 40 °C and 80 °C for different times and pH to graft l-Serine molecules on the zirconia surface. Afterward, the specimens were incubated in simulated body fluid (SBF) for 7 and 21 days. The results indicated that the grafting of l-Serine on the zirconia surface, at 80 °C in neutral pH, created negative charges. The hydroxyl apatite, on the surfaces grafted with l-Serine, started to nucleate and grow almost simultaneously after 7 days of exposure to alkaline pH. The soaking was continued for 21 days to form more uniform mineral apatite with developed surface wettability (i.e., contact angle of 18.3° ± 1.3). Herein, the absorption of calcium and phosphate ions caused the formation of hydroxyapatite nucleation and growth in 21 days.