Main-Chain Polysulfonium Salts: Development of Non-Ammonium Antibacterial Polymers Similar in Their Activity to Antibiotic Drugs Vancomycin and Kanamycin

Typically, quaternary ammonium polymers are employed for antibacterial purposes. However, a century of use has led bacteria to develop resistance to such materials. Therefore, attention is now turning toward other cationic moieties. In this context, the present work explores sulfur-based main-chain cationic polymers. The results indicate that sulfonium polymers with a β-hydroxy motif do not suffer from structural instability issues as is commonly observed in cationic polythioethers. Furthermore, they can be highly effective toward important Gram-positive bacterial strains such as Mycobacterium smegmatis, a model organism to develop drugs against rapidly spreading tuberculosis infections. More importantly, however, more challenging Gram-negative strains such as Escherichia coli can also be targeted by the polysulfoniums with equal effectiveness. Interestingly, side-chain sulfonium polyelectrolytes are observed to be devoid of any significant antibacterial activity. Finally, a comparison with kanamycin and vancomycin suggests the present polymers to be similarly effective as the bactericidal antibiotic drugs. Overall, these results indicate the effectiveness of the main-chain trivalent β-hydroxy sulfonium motif for the development of novel antibacterial polymers with a non-ammonium structure.