Investigations into amphiphilic chitosan: Properties and availability of original and newly introduced functional groups

The accessibility of functional groups of 3,6-O-chitosansulfate in water is studied using conductometric and polyelectrolyte titration techniques. These studies reveal the good accessibility of protonated amino groups following conductometric titrations and pH dependency on the accessibility of negatively charged sulfate groups following polyelectrolyte titrations. In addition, the influence of negatively charged sulfate groups, introduced onto polymer backbone by synthesis, is analyzed regarding the well-known antimicrobial activities of chitosan. The assessment of the mortality rates of Gram-negative, Gram-positive bacteria, and pathogenic fungi reveal that sulfate groups in chitosan lead to a tremendous loss in antimicrobial activity compared with nonmodified chitosan. The physicochemical behavior of 3,6-O-chitosansulfate in aqueous solution is studied. The accessible amounts of protonated amino groups and the accessible amounts of negatively charged sulfate groups are determined by means of different titration techniques because all important biological characteristics related to chitosan and its derivatives seem to be influenced by the charging behavior of the existing moieties.