Preliminary study on the effect of wear process on drug release of ALN-loaded UHMWPE

Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) for anti-osteolysis was developed in our previous study. As a potential material of artificial joints, ALN-loaded UHMWPE is subjected to friction and wear which probably affect the ALN release in vivo. This study aims to explore the influence of friction and wear on the ALN release rate. For comparison, the specimens of control group, immersed motionlessly in distilled water, were not applied any friction. The morphological change of worn surface of ALN-loaded UHMWPE was observed through an independent wear test and was compared with that of control UHMWPE. The ALN release rate in the friction and wear process was higher than that of non-friction test. The cumulative mass of ALN increased slowly at the onset of wear process and then speeded up. The fibrils-like wear debris accumulated on the worn surface of ALN-loaded UHMWPE but did not appear on that of UHMWPE. The micro-pores formed during wear process, were probably favorable of the dissolution of ALN. It indicated that the ALN release of ALN-loaded UHMWPE was affected by the friction and wear. The frictional factors should be taken into account in predicting the ALN release rate of ALN-loaded UHMWPE.