Improving bioactivity of poly(lactic acid) by incorporating pH-neutral bioactive glass

Abstract

Poly(lactic acid) (PLA) is a representative bioresorbable and biocompatible polyester, which has been used in many clinic applications, for examples, artificial bones and internal fixation screws; however, its inherent bio-inertness has limited the therapeutic outcomes. In this article, bioactive glasses (BGs) were incorporated into PLA via melt compounding to enhance its bioactivity. It was found that the high basicity of conventional BGs (45S5 as the representative) severely degraded PLA chains during thermal processing, causing obvious decrease in PLA composites mechanical properties. Instead, the pH-neutral BG, a phosphosilicate calcium glass (denoted as PSC, with the composition of 10.8 %P₂O₅-54.2 %SiO₂-35.0 %CaO, mol%), showed no deterioration of PLA chains, in terms of molecular weight, etc., therefore retained the good mechanical property of PLA composites. The 10 % mPSC/PLA showed improved mechanical performance, with tensile strengths of 52.2 ± 2.8 MPa, compared to 44.2 ± 2.8 MPa of pure PLA. Furthermore, the composites exhibited enhanced bioactivity and biocompatibility, e.g., 10 % mPSC/PLA showed nearly 6 times improvement in cell adhesion (based on the cell spreading area) than pure PLA. This study highlights the importance of acid-base property on the compatibility between polyesters and inorganic fillers, and has identified PSC as a promising bioactive filler to develop better polyester-based biomedical materials.