Development of cationic sulfonium-based gels with inherent antibacterial, excellent antibiofilm, and tunable swelling properties

[Display omitted] •Sulfonium-based gels exhibit excellent bactericidal properties against planktonic Gram-positive and Gram-negative bacteria.•Sulfonium-based gels can eradicate 3-day mature biofilms by killing embedded cells.•The mechanical and swelling properties of sulfonium-based gel can be regulated by tuning the chemical structure and ratio of the precursors. Bacterial biofilms formed on various surfaces can cause serious contamination issues, resulting in economic losses and also threatening public health. However, as a widely used protective material, polymeric gels are usually developed with effective antibacterial properties in killing planktonic bacteria rather than eradicating mature biofilms. Herein, two types of cationic sulfonium-based gels (TEE-S+ and ETT-S+) with inherent antibacterial properties were presented, which can be facilely prepared through the thiol-epoxy “click” reaction and methylation by varying the type and the proportion of precursors. All these gels displayed excellent bactericidal properties (>9-log reduction) against both planktonic Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. The series of TEE-S+ gels presented excellent efficiency in eradicating 3-day mature biofilms of E. coli (∼85 % biomass reduction) by killing embedded cells (>7-log killing efficiency), while ETT-S+ gels with the optimal composition showed outstanding eradication (75%–90% biomass reduction) and killing efficiency (>7-log) against both E. coli and S. aureus biofilm. Moreover, by tuning the crosslinking density of the gel matrix, their compressive modulus and swelling ratio can be adjusted from 5 to 120 kPa and from 17% to 800%, respectively. This work suggests sulfonium-based gels can serve as a promising candidate to provide antibacterial and antibiofilm protection in different application scenarios.