Strategy to improve the characterization of chitosan for sustainable biomedical applications: SAR guided multi-dimensional analysis

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 (IC(50) = 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.