PLA-modified magnesium phosphate bone cement with anti-washout property and degradability

Abstract

Magnesium phosphate cement (MPC) has been widely used in civil engineering as fast-setting repair material. Recently, the biomedical applications of MPC have attracted much attention. MPC has the advantages of fast setting, high early strength and good degradability in vivo. Due to its higher adhesive strength than calcium phosphate cement (CPC), MPC is suggested be used as bone adhesive for unstable fracture treatment. The conventional MPC employed water as the setting liquid and the paste normally showed poor washout resistance when came in contact with water immediately after mixing. This disadvantage might compromise its clinical performance. The aim of this work was to improve the anti-washout property of MPC by incorporating polylactide (PLA) into the liquid phase. The mixing liquid was prepared by dissolving 20% w/w PLA in N-methyl-2-pyrrolidone (NMP). The PLA-modified MPC paste exhibited excellent water resistance, without disintegration even being contact with water immediately after mixing. The setting time ranged from 25 to 56 minutes with varying powder to liquid ratios. The maximum compressive strength reached 27 MPa which was suitable for non-load-bearing applications. XRD and IR analysis indicated that the hardened product was a mixture of NH4MgPO4•6H2O and PLA. In vitro Tris-HCl immersion tests revealed that the degradation of PLA-modified MPC was faster than the conventional MPC. In conclusion, with excellent anti-washout property and improved degradability, the PLA-modified MPC could be applied as bone adhesive and bone substitution material.