Preparation Of Chitosan Derivatives And Their Applications As Antimicrobial Materials And Gene Carriers

Chitosan, is a natural derived polysaccharide biological macromolecule, has lots of outstanding properties, such as biocompatibility, biodegradable, hydrophilicity and antimicrobial activity. It has been used in various biomedical areas. Recently, antibacterial activity and gene transfer ability have been considered as two of its most interesting properties. Herein, we reported that a series of novel chitosan derivatives used as antimicrobial material and gene carriers on the basis of the wonderful properties and chemical reactivity of chitosan. There are three parts in this dissertation, including:(1) A series of water-soluble chitosan-N-arginine (CS-N-Arg) with various degrees of substitution (DSs) from 8.7 to 28.4% were 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 (FT-IR), magnetic resonance spectra (NMR), elemental analysis and X-ray diffraction (XRD) as well as thermogravimetric analysis (TG). Results showed that CS-N-Arg had a more amorphous structure than 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 (S. aureus and E. 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 DSs 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 wound dressing.(2) A series of N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan chloride (HTCC) with various degrees of quaternization ranging from 12.4 to 43.7% were synthesized. The structures and properties of HTCC were investigated by FT-IR,1H NMR, conductometric titration, XRD and TG analysis. It was found that HTCC had a more amorphous structure than chitosan. And the thermal stability of HTCC was slightly lower than that of chitosan. Cytotoxicity results revealed that HTCC samples showed significantly lower cytotoxicity than polyethyleneimine. HTCC samples were able to spontaneously form complexes with pGL3 luciferase plasmid. These complexes had desirable particle sizes (160-300 nm) and zeta potentials (10.8-18.7 mV) when the weight ratios of HTCC to plasmid altered in the range of 3:1 to 20:1. In vitro gene transfection results indicated that HTCC had significantly high transfection efficiency as compared with chitosan for delivering pGL3 luciferase plasmid to Hela cells. Results suggested that HTCC would be a promising non-viral vector for safe and efficient pDNA delivery.(3) Quaternary ammonium group conjugated galactosylated chitosan (gal-HTCC) was successfully synthesized by galactosylation and quaternization of chitosan. The degree of galactosylation and degree of quaternization are respectively 13.7% and 30.8%. The physicochemical properties of this novel polymer were investigated by FT-IR,1H NMR, elemental analysis and XRD analysis. It was found that gal-HTCC had a more amorphous structure than chitosan. Gal-HTCC showed a better pDNA condensation capability than gal-chitosan. Complexes formed by gal-HTCC and pDNA had desirable particle sizes (around 250 nm) when the weight ratios of HTCC to plasmid altered in the range of 3:1 to 20:1. Cytotoxicity results revealed that gal-HTCC showed significantly lower cytotoxicity than PEI 25 kDa. In vitro gene transfection results indicated that gal-HTCC had significantly high transfection efficiency as compared with chitosan for delivering pGL3 luciferase plasmid to HepG2 cells. Results suggested that gal-HTCC would be a promising liver-targeting non-viral vector for safe and efficient pDNA delivery.