Antibacterial Amino Acid-Based Poly(ionic liquid) Membranes: Effects of Chirality, Chemical Bonding Type, and Application for MRSA Skin Infections

Bacteria induced infection remains a serious medical hazard to humans. Antibacterial polymeric materials, which can kill or inhibit bacteria by disrupting cell membranes, inhibiting certain enzymes, or interfering with the transcription or synthesis of DNA or RNA, have been applied to reduce or inhibit microbial drug resistance. Herein, amino acid-based ionic liquids (ILs) and poly­(ionic liquid) (PIL) membranes were synthesized and used as antibacterial materials to treat skin wounds infected by methicillin-resistant Staphylococcus aureus (MRSA). The effects of chirality (D- or L-enantiomers) and chemical bonding (ionic or covalent) of the amino acid groups attached to the IL (or PIL) on antibacterial properties were investigated. Both the ILs and PIL membranes containing D-enantiomeric amino acid groups exhibited higher antibacterial activities compared with those containing L-enantiomeric amino acids. In addition, the ionically-bonded PIL membranes showed higher antibacterial activities than the corresponding covalently-bonded polymeric membranes. These results indicate that both the chirality and chemical bonding type of amino acid groups affect the antimicrobial activity of the PIL membranes. Additionally, the amino acid-based PIL membranes accelerated the wound-healing process, alleviated local tissue inflammation, and reduced the influence of bacteria on vital organs (liver and spleen) in MRSA-infected mouse models, demonstrating the potential applications for antimicrobial wound dressing.