Water-Soluble Modified Chitosan and Its Interaction with a Polystyrenesulfonate Anion

The selective alkylation of primary amino groups of polysaccharide is conducted through the interaction of chitosan with glycidyltrimethylammonium chloride with introduction of the quaternized amino group into every alkylated unit, thereby ensuring a positive charge and solubility of the polymer over the entire pH range. The structure of the modified chitosan is studied via FTIR spectroscopy and (13)C and (1)H NMR measurements. On the basis of the potentiometric titration of solutions of the parent polysaccharide, its modified derivative, and their mixtures with the polystyrenesulfonate anion, as well as zeta-potential measurements and turbidimetric titration of polymer mixtures, it is demonstrated that the secondary amino group of the complexed modified chitosan can be protonated in weakly acidic solutions. This behavior is of particular importance for the design of biocompatible and biodegradable vehicles suitable for the delivery of genetic material and drugs to cells.