Mechano-assisted synthesis of lignin-based hybrid materials for antimicrobial applications

Lignin and lignin-based materials represent a great opportunity to develop novel materials that combine the antioxidant and antibacterial properties of the polyphenolic matrix with the biological profile of an inorganic phase. We here use a mechano-assisted approach to obtain straightforward isolation of the hybrid materials HMW@ZnO, HMW@Cu₂O, and the mixed-oxide HMW@ZnO_Cu₂O, where HMW (High Molecular Weight) is a Kraft lignin from Pinus taeda. Full material characterization confirmed that mechano-synthesis is an efficient method for smoothly forming products with controlled amounts of Zn, Cu or both, embedded within the Kraft lignin matrix. In vitro testing against four pathogens (Staphylococcus aureus, Lactococcus garvieae, Escherichia coli, and Aeromonas veronii) showed that all lignin hybrids exhibited enhanced antimicrobial activity compared to pure reference metal oxides. Crucially, the HMW@ZnO_Cu₂O hybrid demonstrated superior efficacy (lower MBC values) against S. aureus and A. veronii compared to the single-oxide hybrids, suggesting a positive interaction mechanism between the combined metal phases. These findings validate mechano-assisted synthesis as an effective route for developing potent, lignin-based antimicrobials.