Bowl-shaped alkylated lignin nanoparticles: A novel platform for stable antibacterial Pickering emulsions

Pickering emulsions stabilized by nanoparticles exhibit enhanced stability and broad application potential compared to traditional surfactant-based emulsions. Herein, we report a novel approach for developing antibacterial Pickering emulsions using alkylated lignin nanoparticles (ALC_χNPs). The alkylation of lignin was achieved through a systematic synthesis of derivatives with varying alkyl chain lengths, followed by nanoparticle formation via a solvent-exchange method. Characterization revealed that increasing alkyl chain length resulted in smaller nanoparticles and a unique bowl-shaped morphology. Among them, dodecyl-modified ALC₁₂NPs demonstrated optimal amphiphilicity, leading to the most stable and homogeneous emulsions with versatile plant oils including canola oil and cinnamaldehyde. The resulting Pickering emulsions exhibited potent antibacterial activity against both Escherichia coli and Staphylococcus aureus due to synergistic effects of ALC₁₂NPs and cinnamaldehyde enhanced bacterial membrane disruption. This study provides a sustainable pathway for designing biocompatible, lignin-based Pickering emulsifiers with tailored properties for biomedical and antibacterial applications.