Synthesis, Characterization, and Antibacterial Effects of Trimethylated and Triethylated 6-NH2-6-Deoxy Chitosan

Abstract

Chitosan, a biodegradable and biocompatible polymer, has attracted great attention in the pharmaceutical and biomedical fields especially due to its properties to reversibly open the tight junctions of the epithelial tissues and to allow for paracellular transport of hydrophilic macromolecules. However, chitosan exhibits low solubility at pH values above 6 that may prevent its enhancing effects at the sites of intestinal absorption. Hence, a number of alkylated chitosan salts have been synthesized and characterized. These derivatives have been shown to have good solubility at neutral pH and act as effective permeation enhancers. In this study, two new derivatives of chitosan, C2—C6 trimethyl 6-amino-6-deoxy chitosan and C2—C6 triethyl 6-amino-6-deoxy chitosan were synthesized and characterized using 1H-NMR and FTIR spectra. Moreover, the zeta potential and the antibacterial properties of these polymers were compared to chitosan, trimethyl chitosan (TMC) and triethyl chitosan (TEC). Our results suggest that both C2—C6 trimethyl and triethyl 6-amino-6-deoxy chitosan, as highly water soluble polymers, have higher positive surface charge than chitosan, TMC, and TEC. Moreover, the new synthesized polymers show higher antibacterial activity against Gram-positive Staphylococcus aureus bacteria. Consequently, these polymers with substitution degrees of 50—60% may be good candidates for the enhancement of peptides in mucosal drug delivery.