Covalent modification of chitosan surfaces with a sugar amino acid and lysine analogues

This work explores the modification and characterization of chitosan thin films as a model for functionalized polysaccharide interfaces. The solid–liquid interface of oligo- and polysaccharides is crucial for various biological processes such as cell adhesion and recognition. By covalent surface modification of the chitosan via amide formation with different small molecules containing carboxylic acids, e.g. specially designed glycoside hydrolase inhibitors, interactions with biomolecules and living cells could potentially be controlled in the future. As a first step towards this aim, three fluorescent compounds were conjugated onto nanometric chitosan thin films. The layers were analysed by fluorescence spectroscopy, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and atomic force microscopy, to proof the covalent attachment of the target molecules. By this analysis, a uniform and chemically stable covalent attachment of the target molecules on the chitosan thin films could be demonstrated under various conditions. This publication serves as a proof-of-concept-study for further biofunctionalization, pattering, and interaction studies involving polysaccharide interfaces, glycosidase inhibitors, proteins, or living cells.