Preparation And Characterization Of An Antibacterial Material Chitosan-N-Guanidine

Chitosan(CS) is a unique alkaline polysaccharide containing nitrogen in nature. It hasoutstanding biocompatibility, biodegradability and antibacterial ability. Chitosan and itsderivative can be used in the fields of wound healing, antibacterial and anti-virus and so on.Guanidine is the strongest organic base in considering its dissociation constant.Antibacterial ability of chitosan derivatives is enhanced by increasing positive electricity.Inthe view of the function of guanidine, chitosan-N-guanidine(CG) with different degree ofsubstitution were synthesized and measured with their antibacterial ability.In this work, chitosan was obtained by highly deacetylating chitin, and thendegradating molecular weight. Guanidine was grafted to chitosan with EDC, NHS, MESasinitiator, catalyst and buffer. Chitosan and guanidine were allowed to react for18h,24h and36h.The final products with three degrees of deacetylation (DD) were named CG-1, CG-2,CG-3. Their degrees fo substitution(DS) were11.03%,13.39%and21.59%. Theantibacterial activities of CS and CG were determined by a plate count agar(PCA) methodand the bacterias were S.aureus which was Gram-positive bacteria and E.coli which wasGram-negative bacteria.The conclusions are as follows: CS and CG exhibit antibacterial abilities against bothS.aureus and E.coli. The antibacterial abilities of CG are stronger than CS.When the concentration is lower than0.3g/L, CS can help S.aureus grow. When theconcentration is higher than0.3g/L, CS exhibits obvious antibacterial ability and inhibitsall of S.aureus. When the concentration is lower than0.2g/L, CS can help E.coli grow. Inthe range of concentrations changing from0.2g/L and0.3g/L, CS exhibits antibacterialability but not obvious. When the concentration is higher than0.3g/L, CS can inhibit all ofE.coli.CG can help S.aureus grow when the concentration is lower than0.15g/L. S.aureus hasbeen completely inhibited when the concentration is higher than0.15g/L. The higher DS CG is, the more stronger antibacterial ability it has. The growth of E.coli is slightlypromoted when the concentration is lower than0.1g/L. At the concentration ranging from0.1g/L and0.15g/L, the antibacterial activities of CG are exhibited. When the concentrationreaches0.15g/L, the growth of E.coli has been completely inhibited.