Examining the effect of common nitrosating agents on chitosan using a glucosamine oligosaccharide model system

Chitosan has received substantial attention as a biomaterial due to its unique properties. It has become increasingly common to derivatize chitosan to produce nitric oxide (NO)-releasing materials that exert various therapeutic effects through the action of NO. It is generally the case that these NO-releasing polymers are prepared by exposure to high-pressure NO or nitrosating agents like nitrous acid (HNO₂) or alkyl nitrites (RONO). In our study, mass spectrometry and spectroscopic methods demonstrate that both monomeric and oligomeric glucosamine experience chemical alteration after exposure to HNO₂-based nitrosating conditions from the literature. In polymeric chitosan, HNO₂-based nitrosating conditions were found to induce degradation through the formation of 2,5-anhydro-d-mannose and oligosaccharides. In contrast, the RONO tert-butyl nitrite and high-pressure NO were not found to significantly degrade or otherwise alter the structure of glucosamine or its oligomers, supporting the suitability of these approaches.