Quaternary ammonium salts of chitosan. A critical overview on the synthesis and properties generated by quaternization

The quaternary ammonium salts of chitosan are water soluble derivatives which keep the promise for real life applications in a large realm of biomedical fields, such as antimicrobial products, gene therapy, drug delivery, wound healing, tissue engineering and cosmetics. The increased potential for such applications is gained by a beneficial combination of the intrinsic properties of chitosan with those of the quaternary ammonium units. Since the first report of the synthesis of the quaternary ammonium salts of chitosan, many synthetic routes were developed, each of them with advantages and disadvantages which influence the product’s properties. The aim of this review was to systemize these synthetic procedures and the properties of the resulted products, highlighting these advantages and disadvantages, in the desire to help the researchers working in this productive domain to choose the most suitable synthetic pathway when specific properties are targeted.