The ongoing demand for effective antimicrobial materials persists, and lignin emerges as a promising natural antibacterial material with renewable properties. The adaptability of lignin to various chemical modifications offers avenues to enhance its antimicrobial activity. Here, we employed chloromethylation and subsequent functionalization with variable tertiary N-alkyl dimethyl amines to produce C6–C18 quaternary ammonium lignins (QALs) from hardwood (aspen), softwood (pine), and grass (barley straw). Successful synthesis of QALs was confirmed through NMR and FTIR analysis results along with an increase in the surface ζ-potential. Antibacterial activity of QALs against clinical strains of Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus was assessed using minimal bactericidal concentration (MBC) assay and agar growth inhibition zone (ZOI) test. The antibacterial activity of QALs was found to be higher than that of the unmodified lignins. QALs with longer alkyl chains demonstrated an MBC of 0.012 mg/L against K. pneumoniae already after 1 h of exposure with similar effect size reached after 24 h for S. aureus. For all the lignins, an increase in alkyl chain length resulted in an increase in their bactericidal activity. MBC values of C14–C18 QALs were consistently lower than the MBC values of QALs with shorter alkyl chains. Besides the alkyl chain length, MBC values of barley and pine QALs were negatively correlated with the surface ζ-potential. While alkyl chain length was one of the key properties affecting the MBC values in a liquid-based test, the agar-based ZOI test demonstrated an antibacterial optimum of QALs at C12–C14, likely due to limited diffusion of QALs with longer alkyl chains in a semisolid medium.

In this study, we explored the selectivity of softwood lignin toward esterification through chloromethylation. Organosolv pine lignin chloromethylated by a novel greener protocol was subjected to esterification with decanoic acid (C10), tetradecanoic acid (C14), and stearic acid (C18). The success of lignin esterification was confirmed by using FTIR and NMR spectroscopy. For composite preparation, modified lignin was incorporated with PLA in varying proportions (10%, 20%, 30%, and 40%) using the solvent casting technique. The thermal and mechanical properties of the solvent-cast films were analyzed. Notably, lignin esters increased the glass transition temperature (T _g) of PLA by a few degrees: tetradecanoic acid (C14) at 30% loading exhibited increases T _g from approximately 68 to 72 °C. Mechanical testing showed that blending PLA with lignin and its ester derivatives improves its properties. Pure PLA has moderated ductility and stress but lowered stress levels compared to PLA-lignin ester blends. Adding 30% lignin reduced strength and strain, making the material more brittle. In contrast, the PLA + lignin C14 ester (30%) blend achieved the highest stress and strain, enhancing toughness and strength. This makes lignin C14 ester a promising additive for improving the mechanical properties of PLA in applications requiring greater strength and toughness. The composition with optimum properties was selected for production of the 3D-printing filament. Three extrusion temperatures were evaluated, and the advanced mechanical properties of 3D-printed filament along with surface morphology were analyzed.

Farmers from South Asian countries spray insecticides without protective gear, which leads to insecticide exposure through dermal and nasal routes. Acetylcholinesterase plays a crucial role in controlling neuromuscular function. Organophosphate and carbamate insecticides inhibit acetylcholinesterase, which leads to severe neuronal/cognitive dysfunction, breathing disorders, loss of endurance, and death. To address this issue, an Oxime-fabric is developed by covalently attaching silyl-pralidoxime to the cellulose of the fabric. The Oxime-fabric, when stitched as a bodysuit and facemask, efficiently deactivates insecticides (organophosphates and carbamates) upon contact, preventing exposure. The Oxime-fabric prevents insecticide-induced neuronal damage, neuro-muscular dysfunction, and loss of endurance. Furthermore, we observe a 100% survival rate in rats when repeatedly exposed to organophosphate-insecticide through the Oxime-fabric, while no survival is seen when organophosphate-insecticide applied directly or through normal fabric. The Oxime-fabric is washable and reusable for at least 50 cycles, providing an affordable solution to prevent insecticide-induced toxicity and lethality among farmers.