An overview of current knowledge on the properties, synthesis and applications of quaternary chitosan derivatives

Chitosan, a chitin-derivative polysaccharide, known for its non-toxicity, biocompatibility and biodegradability, presents limited applications due to its low solubility in neutral or basic pH medium. Quaternization stands out as an alternative to modify this natural polymer, aiming to improve its solubility over a wide pH range and, consequently, expand its range of applications. Quaternization occurs by introducing a quaternary ammonium moiety onto or outside the chitosan backbone, via chemical reactions with primary amino and hydroxyl groups, under vast experimental conditions. The oldest and most common forms of quaternized chitosan involve N,N,N-trimethyl chitosan (TMC) and N-[(2-hydroxy-3-trimethyl ammonium) propyl] chitosan (HTCC) and, more recently, quaternized chitosan by insertion of pyridinium or phosphonium salts. By modifying chitosan through the insertion of a quaternary moiety, permanent cationic charges on the polysaccharide backbone are achieved and properties such as water solubility, antimicrobial activity, mucoadhesiveness and permeability are significantly improved, enabling the application mainly in the biomedical and pharmaceutical areas. In this review, the main quaternized chitosan compounds are addressed in terms of their structure, properties, synthesis routes and applications. In addition, other less explored compounds are also presented, involving the main findings and future prospects regarding the field of quaternized chitosans12

Coating of surgical masks with quaternized chitosan aiming at inactivating coronavirus and antibacterial activity

SARS-CoV-2 caused a global pandemic with high transmission rates, even with widespread vaccination. In addition to isolation and prevention measures, it is important to find new solutions to inactivate the virus and prevent its viability on surfaces, such as clothing and face masks. Chitosan derivatives, with their antibacterial activity, biocompatibility, and non-toxicity, are a promising option for coating these components with virucidal materials. N-(2-hydroxypropryl)-3-trimethylammonium chloride, a quaternized chitosan derivative with degrees of substitution ranging from 59 to 93%, was synthesized. This derivative was used to coat cotton and polypropylene fabrics, such as face masks, without visibly affecting their morphology or filtering capacity. In vitro tests demonstrated that the coatings produced had high antiviral activity against coronavirus, with efficacy up to 99.99%, and were also bactericidal against E. coli and S. aureus. These results show that quaternized chitosan derivatives have great potential to be used as virucidal coatings, helping to prevent the spread of SARS-Cov-2 and other pathogens on surfaces, which can even be useful for the quick development of solutions for future pandemics