The impact of green and organic solvent-based lignin fractionation on polylactic acid biomaterial properties and biocompatibility.

Biomass (cardoon)-derived lignin was fractionated using three solvents, gamma-valerolactone (GVL), acetone, and ethanol (EtOH), and incorporated into polylactic acid (PLA) with 1, 3, and 5 wt% of lignin developing biocomposites via solvent casting. The organosolv fractionation and lignin extraction process enabled the selective separation of lignin, with the choice of solvent significantly influencing lignin particle morphology. Scanning electron microscopy revealed GVL promoted particle nucleation through gradual coalescence, acetone led to rapid solidification with a mixture of large and small particles, and EtOH induced rapid supersaturation, forming smaller, irregular particles. Infrared spectroscopy confirmed lignin incorporation into PLA matrix, with variations in hydroxyl and carbonyl group intensities reflecting interfacial interactions. Thermogravimetric analysis indicated low lignin loading was most effective in enhancing the thermal stability of PLA composites containing GVL and acetone fractionated lignin. In contrast, composites with EtOH fractionated lignin exhibited the best thermal performance at higher percentage. Biological evaluations using human adipose-derived stem cells confirmed excellent cytocompatibility over 14 days. Notably, lignin fractionated with EtOH demonstrated the highest protein adsorption, suggesting enhanced cell-material interaction potential. These findings highlight the potential of cardoon-derived lignin as a sustainable reinforcement for PLA and the choice of solvent for lignin fractionation significantly influences material properties.