Setting behavior, apatite-forming ability, mechanical strength of polymethylmethacrylate bone cement through bioactivity modification of phosphate functional groups combined with Ca2+ ions

Abstract

Bioactivity modification helps polymethylmethacrylate (PMMA) bone cement to reinforce its interfacial adhesion to bone tissues through the chemical bonding of apatite. Since Si-OH groups combined with Ca2+ ions have succeeded in inducing apatite formation, more combinations of functional groups and active ions are being explored. In this study, Bis[2-(methacryloyloxy)ethyl] phosphate (B2meP) containing phosphate (=PO4H) groups and Ca(CH3COO)2 supplying Ca2+ ion were adopted to investigate the feasibility of equipping PMMA bone cement with apatite-forming ability in vitro, more effects under designed contents on setting behavior, injectability, contact angle, cytotoxicity and mechanical strength were also investigated. Results showed B2meP copolymerized with MMA and became one section of PMMA chains, surface = PO4H groups and released Ca2+ ions pushed spherical apatite individuals nucleating and agglomerating into layer horizontally, Increasing B2meP content lowered the contact angle and the peak temperature, enhanced the cell viability of MC3T3-E1, but prolonged apatite forming period. Injectability rate performed a similar trend to setting time. Lower adding content and deposited apatite layer contributed to reduce the strength loss in soaking. Taking biological performance and other properties into balance, cement added with B2meP of 10 wt% in MMA and Ca(CH3COO)2 of 20 wt% in PMMA performed better.