Interface-Enhanced Mg/PLA Composite with Superior Mechanical, Biodegradable and Biocompatible Properties for Orthopedic Implants

Magnesium (Mg) reinforced polylactic acid (PLA) composites have attracted increasing interest for orthopedic implants to solve the insufficient strength of PLA and to utilize the bioactive advantages of Mg ions in promoting bone formation. However, the weak interfacial adhesion between the Mg and PLA limits the applications of the composite. In this study, a dual interfacial enhancement approach was designed to combine surface fluorination with perforation. During hot pressing, molten PLA infiltrates the pores to form a ‘rivet-like’ mechanical interlocking. This structure significantly alters the load transfer and degradation behaviors of the composite. Compared to pure PLA, the dual treatment significantly elevated the bending strength by 49%, alongside an increase in the bending strain from 15% to 25%. Moreover, in vitro degradation tests revealed that this strategy suppresses H2-induced delamination, and stabilizes both pH and Mg2+ release. Consequently, the bending strength remained at 86% after six weeks of in vitro degradation. In addition, the composite exhibits excellent biocompatibility, with MC3T3-E1 cell viability exceeding 90% in 100% extract. These results demonstrate that the reinforced Mg/PLA composite exhibits excellent mechanical properties, degradation stability, and biocompatibility, showing high potential for load-bearing orthopedic fixation applications.