Engineering Poly(lactide)-Lignin Nanofibers with Antioxidant Activity for Biomedical Application

Biodegradable poly(lactic acid) (PLA)-lignin composites are considered to be promising renewable plastic materials toward a sustainable world. The addition of lignin to PLA may assist to combat the oxidative stress induced by PLA as biomaterials. In this study, PLA-lignin copolymers with various contents of alkylated lignin (10-50%) were synthesized by ring-opening polymerization. The molecular weight of such copolymers ranged from 28 to 75 kDa, while the PLA chain length varied from 5 to 38. These PLA-lignin copolymers were further blended with poly(L-lactide) (PLLA) and fabricated into nanofibrous composites by electrospinning. The PLLA/PLA-lignin nanofibers displayed uniform and bead-free nanostructures with fiber diameter of 350-500 nm, indicating the miscibility of PLLA and lignin copolymers in nanoscale. Unlike bulk materials, incorporation of PLA-lignin copolymers did not enhance the mechanical properties of the nanofibrous composites. Antioxidant assay showed that the lignin copolymers and PLLA/PLA-lignin nanofibers rendered excellent radical scavenging capacity for over 72 h. Moreover, three different types of cells (PC12, human dermal fibroblasts, and human mesenchymal stem cells) were cultured on the electrospun nanofibers to evaluate their biocompatibility. Lignin-containing nanofibers exhibited higher cell proliferation compared to neat PLLA nanofibers. PLLA/PLA-Lig20 nanofibers displayed the best biocompatibility as it achieved a balance between the antioxidant activities and the cytotoxicity. With excellent antioxidant activities and good biocompatibility, the PLLA/PLA-lignin electrospun nanofibers hold great potential to be used as biomedical materials for protecting cells from oxidative stress conditions.