Cationic antibacterial polymers for development of bactericidal materials: Strategies, mechanisms, and applications

The worldwide consumption of antibiotics has significantly contributed to the escalating challenge of antibiotic resistance over the past decades. Therefore, there is a tremendous interest in the development of new non-antibiotic antibacterial agents as alternatives to traditional antimicrobial drugs, which could exhibit prolonged action, enhanced efficacy, and reduced toxicity. Among various antibacterial agents, cationic antibacterial polymers (CAPs) have been particularly appearing due to their plenty of positive-charged groups or segments, enabling them to interact effectively with the negatively charged surfaces of microorganisms, thereby inhibiting their growth. This review paper begins by summarizing the different types and features of CAPs including quaternary ammonium salt (QAS) polymers, guanidine salt (GS) polymers, and quaternary phosphonium salt (QPS) polymers, originating from both natural and synthetic polymers. Subsequently, the antimicrobial mechanisms of CAPs are further discussed, including electrostatic interactions, cell membrane damage, protein precipitation, and DNA damage, and it was pointed out that the synergistic effect of these mechanisms confers strong antimicrobial capabilities to CAPs. Additionally, the article extensively discusses the applications of CAPs in key areas such as textiles, medical care, food packaging, and water treatment, and identifies current challenges, such as the development of resistance, environmental impact, and potential biotoxicity. Moreover, this review summarizes the latest literature on the antibacterial activity of various CAPs combined with different polymers as substrates and provides future directions for exploring the novel non-antibiotic antibacterial agents for various applications.