Preparation and characterization of antimicrobial chitosan-N-arginine with different degrees of substitution

A series of water-soluble chitosan-N-arginine (CS-N-Arg) with various degrees of substitution (DSs) from 8.7 to 28.4% was synthesized by reacting amino groups of chitosan with arginine. The chemical structures and physical properties of CS-N-Arg were characterized by Fourier-transform infrared, magnetic resonance spectra, elemental analysis and X-ray diffraction as well as thermogravimetric analysis. Results showed that CS-N-Arg had a more amorphous structure than that of chitosan, and the thermal stability of CS-N-Arg was slightly lower than that of chitosan. It was found that CS-N-Arg samples were able to inhibit almost all the bacteria (Staphylococcus aureus and Escherichia coli) at a concentration higher than 150 ppm, whereas they could promote the growth of bacteria at a concentration lower than 50 ppm. The antibacterial activity of CS-N-Arg samples was dependent on both DS and concentrations changed in the range from 50 to 150 ppm. Due to their enhanced antimicrobial properties, CS-N-Arg materials would be promising candidates for the applications in skin tissue engineering.