Cholic-Acid Derived, Guanidine-Functionalized Polymers as Broad-Spectrum Antimicrobial Agents

In this study, we report the design of a new guanylated, cholic-acid-based monomer (GM) to combat antimicrobial resistance. The microbial activity stems from the interfacial amphiphilicity of cholic acid, while guanidine shows a strong association with phosphate, which promotes binding to membrane phospholipids. The monomer showed strong antimicrobial activity; however, surprisingly, homopolymers synthesized by photoiniferter reversible addition-fragmentation chain-transfer (RAFT) polymerization of GM completely lost their activity likely due to the conformation of the polymer. In contrast, the design of GM copolymers with poly(ethylene glycol) methyl ether methacrylate (PEGMA) or 2-hydroxyethyl methacrylate (HEMA) allowed recovery of their antimicrobial activity. Due to the existence of cholesterol in cell membranes, hemolysis was highly dependent on the content of GM incorporated. This study highlights the unique and intriguing properties of this novel amphiphilic monomer and its polymers, providing valuable insights into the development of more potent antimicrobial materials.