Antimicrobial Properties of Chitosan and Its Derivatives

The investigations of chitosan as an antimicrobial substance came into focus in the 1990s. The number of publications on this topic has been rapidly increasing since then, with more than 2,500 papers published in 2020. Initially, the interest was mainly related to potential applications in agriculture and food products, but currently, the emphasis on the medical use of chitosan and chitosan derivatives is continuously increasing. Common derivatives of chitosan include carboxymethyl chitosan (CMC), N,N,N-trimethyl chitosan (TMC), N-(2-hydroxyl), propyl-3-trimethyl ammonium chitosan chloride (HTCC), hydroxypropyl chitosan (HPC), and glycol chitosan. All of these derivatives have been investigated as antimicrobial polymers in various applications, but most such studies involve using the cationic derivatives TMC and HTCC. Countless other antimicrobial chitosan derivatives have been reported in at least one publication. Many researchers have studied the antimicrobial mechanism of action against bacteria and fungi and found that the polymers affect the cell membrane, but the details of the interaction are still debated. Other studies have indicated intracellular nucleic acids, surface proteins, and lipopolysaccharides as possible targets. Various applications, including plant protection, food preservation, wound treatment, and water purification, have been considered to utilize the antimicrobial properties of chitosan-based materials. Structure-activity relationship studies are helpful to elucidate the function and importance of different structural characteristics that may influence activity, including the degree of acetylation (DA), charge, the structure of the substituted, degree of substitution (DS), and molecular weight (Mw).