Synthesis,structural characterization and properties of water-soluble N-(gamma-propanoyl-amino acid)-chitosans

摘要

Water-soluble peptide-chitosans were obtained by reaction of low-molecular-weight chitosan,having a low degree of acetylation,with peptide substituents under mild conditions.These peptide substituents were prepared by standard peptide chemistry from 3-bromopropanoic acid and tery-butyl esters of the alpha-amino acids glycine and phenylalanine.The structure of the new peptide-chito-san polymers was confirmed by proton nuclear magnetic resonance and infrared spectroscopy.The thermotropic and morphological properties of both the new peptide-chitosans and two other analogues,derived from valine and aspartic acid [synthesis reported in Batista,M.K.S.,Pinto,L.F.,Gomes,C.A.R.,& Gomes,P.(2006).Novel highly soluble peptide-chitosan polymers:Synthesis and spectral characterization.Carbohydrate Polymers,64,299-305],were evaluated by differential scanning calorimetry and scanning electron microscopy,respectively.As compared to the parent unmodified chitosan,the four peptide-chitosans had higher thermo-sensitivity,porosity and water-holding capacity,and such effects increased with the hydrophilicity of the peptide ligands.The acid-base properties of the four peptide-chitosans were also evaluated by potentiometric techniques and reflected the influence of the inserted ligands on the polymers' acidity constants.It was also possible to confirm the polymers' solubility over the 2-10 pH range.Overall,these polymers present physico-chemical properties that make them promising candidates for the design of novel drug delivery systems.