Abstract:The physicochemical nature of chitin and chitosan, which influences the biomedical activity of these compounds, is strongly related to the source of chitin and the conditions of the chitin/chitosan production process. Apart from widely described key factors such as weight-averaged molecular weight (M W ) and degree of N-acetylation (DA), other physicochemical parameters like polydispersity (M W /M N ), crystallinity or the pattern of acetylation (P A ) have to be taken into consideration. From the biological point of view, these parameters affect a very important factor-the solubility of chitin and chitosan in water and organic solvents. The physicochemical properties of chitosan solutions can be controlled by manipulating solution conditions (temperature, pH, ionic strength, concentration, solvent). The degree of substitution of the hydroxyl and the amino groups or the degree of quaternization of the amino groups also influence the mechanical and biological properties of chitosan samples. Finally, a considerable research effort has been directed towards developing safe and efficient chitin/chitosan-based products because many factors, like the size of nanoparticles, can determine the biomedical characteristics of medicinal products. The influence of these factors on the biomedical activity of chitin/chitosan-based products is presented in this report in more detail. OPEN ACCESSPolymers 2011, 3 1876

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The biopolymer chitosan has shown great potential for a tremendous number of applications despite the fact that typical chitosan preparations are always mixtures of different chemical entities, natural impurities and process-induced impurities. However, chitosan preparations described in the literature or offered on the market are analytically highly undefined. Here we propose a T-SAR (thinking in terms of structure-activity-relationships) guided multi-dimensional analysis of distinct chitosan preparations with the aim a) to obtain the information needed for the production of reproducible chitosan preparations and b) to predict biological effects and technological properties of certain chitosan preparations. First, a physico-chemical description (molecular weight (M-W), polydispersity (M-W/M-N), fraction of acetylation (F-A), pattern of acetylation (P-A), hydrodynamic radius (R-h), intrinsic viscosity ([eta])) of six selected samples was done. Furthermore chitosan properties like solubility, crystallinity, conformation (Mark-Houwink-plot) and impurities of all the chitosan preparations from different origins were determined and biological effects were also analyzed using test systems with two different bacteria (Escherichia coli, Vibrio fischeri). It was found that the presence of HCl enabled the water solubility of chitosan, while chloride-free chitosan was only soluble in acetic acid. The pattern of acetylation P-A showed no impact on this behavior. The analyzed biological effects revealed growth inhibition within 30 minutes for E. coli and a decreased bioluminescence for V. fisheri (IC50 = 0.035 w%). Thus, the strategy to check biological effects within a multi-dimensional analysis kit proved to be effective for detecting general structure-property-relationships of chitosan in relation to its biological effects

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