Hydrothermal lignin microspheres: Synthesis, structural evolution, and antibacterial performance

This study reported a modified hydrothermal solvent method for preparing lignin microspheres (LNSs) with controllable size and morphology by precisely regulating the reaction temperature (160–220 °C). Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were employed to evaluate the structure, morphological, and dimensional attributes of lignin microspheres, and the synthesis mechanism was discussed. The antibacterial efficacy of the hydrothermally treated lignin microspheres (HTLNSs) was evaluated through phosphate-buffered saline (PBS) culture assays, as well as by assessing nucleic acid and protein leakage, and their inhibitory effect on cell membrane permeability. Among the synthesized samples, HTLNS-180 demonstrated superior bacteriostatic properties, achieving the highest nucleic acid content and bacterial cell permeability post-treatment, suggesting significant bacterial cell wall disruption. Its antibacterial inhibition rate reached 51.0 % against Staphylococcus aureus ( S. aureus ) and 54.3 % against Escherichia coli ( E. coli ). The study provides new insights into the structure-property relationship of lignin-based nanomaterials and their potential in biomedical and antimicrobial applications.