Surface modification of PLA nanofibers with plasma and graphene oxide for enzyme immobilization

Polylactic acid (PLA) has emerged as a favorable material for biomedical applications due to its inherent biodegradability and biocompatibility. However, its limited surface wettability constrains its effectiveness in enzyme immobilization. To overcome this limitation, we explored two surface modification strategies aimed at enhancing the enzyme-loading capacity of PLA nanofiber mats: oxygen plasma treatment and the incorporation of graphene oxide (GO) nanosheets. Four sample groups-pure PLA, GO-modified PLA (PLA-GO), plasma-treated PLA (PLA-P), and plasma-treated GO-modified PLA (PLA-GO-P)-were evaluated using glucose oxidase (GOx) and horseradish peroxidase (HRP) as model enzymes. Plasma treatment alone significantly enhanced enzymatic activity, increasing it from 5.5 to 9.2 mUnit/cm², due to improved hydrophilicity. The introduction of GO further improved enzyme immobilization efficiency, achieving 21.1 mUnit/cm². Surprisingly, the combined treatment (PLA-GO-P) did not produce a synergistic effect; instead, the enzymatic activity dropped to 7.9 mUnit/cm².Spectroscopic analyses (XPS, ATR-FTIR, EDS) suggested that plasma exposure may oxidize double bonds and degrade oxygen-containing functional groups on GO, thereby reducing the number of effective binding sites for enzymes. These results were corroborated by molecular dynamics simulations, which indicated reduced interaction enthalpies upon GO incorporation and enhanced hydrophilicity post plasma treatment. These findings underscore the importance of tailoring surface modification protocols to preserve functional groups critical for enzyme binding, ultimately guiding the rational design of PLA-based nanofibrous scaffolds for biomedical enzyme immobilization applications.