Chitosan: A review of molecular structure, bioactivities and interactions with the human body and micro-organisms.

Chitosan has many desirable attributes e.g. antimicrobial properties and promoting wound healing, and is used in various applications. This article first discusses how degree of deacetylation (DD) and molecular weight (MW) impacts on what level of bioactivities chitosan manifests, then introduces the "molecular chain configuration" model to explain various possible mechanisms of antimicrobial interactions between chitosan with different MW and different types of bacteria. Similarly, the possible pathways of how chitosan reacts with cancer and the body's immune system to demonstrate immune and antitumor effects are also discussed by using this model. Moreover, the possible mechanisms of how chitosan enhances coagulation and wound healing are also discussed. With these beneficial bioactivities in mind, the application of chitosan in surgery, tissue engineering and oncology is outlined. This review concludes that as chitosan demonstrates many beneficial bioactivities via multiple mechanisms, it is an important polymer with a promising future in medicine.

Chitosan: A review of sources and preparation methods.

Chitosan, derived from chitin, has many desirable biomedical attributes. This review aims to explore different sources of chitin and methods of chitosan production with industrial consideration. This article first discussed different sources of chitin for industrial scale production, with considerations given to both their environmental impacts and commercialization potential. Secondly, this article reviews the two categories of chitosan preparation - chemical methods and biological methods - based on existing publications which used lobster by-products as a feedstock source. The mechanisms of the chemical methods are firstly summarized, and then the different chemical agents and reaction parameters used are discussed. Next, both enzymatic and fermentation-based approaches are reviewed under biological methods and compared with chemical methodologies, with lactic fermentation methods as the major focus. This article concludes that lobster cephalothorax could be an ideal source for chitosan preparation on an industrial scale; and chemical methods involve simpler processing overall, while producing chitosan with stronger bioactivities because of the lower molecular weight (MW) and higher degree of deacetylation (DD) achieved by the products. Moreover, due to biological methods inevitably necessitating further chemical processing, an approach involving some unconventional chemical methods has been regarded as a more suitable strategy for industrial scale chitosan production.