The Irradiation Assisted Preparation And Research Of Chitosan Antibacterial Agent

Chitosan is the most common broad-spectrum macromolecule antimicrobial agent with a great amount of yeild in nature, has the properties of safety, nontoxicity, excellent biological affinity and natural decomposition. Chitosan can not fully solve in water and only possess antimicrobial properties in acid environment. In order to obtain water soluble chitosan antibacterial agent which possess better antibacterial properties, O-quaternary,N-carboxymethyl chitosan and chitosan biguanidine acetate was synthesized by introducing different antimicrobial group onto the active amino or hydroxyl of γ-ray preirradiated chitosan.The conditions of reaction 、 product structure、 antibacterial properties and biotoxicity were studied.Quaternized carboxymethyl chitosan(QCMC) were synthesized by two-step: glyoxylic acid react with amino on preirradiated chitosan generating schiff base first, then reduct schiff base to N-carboxymethyl chitosan(N-CMC); Then the N-CMC were quaternized with 2,3-epoxypropyltrimethylammonium chloride(GTA). FT-IR results showed that carboxymethyl substituted on C2-NH3, quaternary ammonium substitution mainly happens on the C6-OH, the QCMC is O-quaternized,Ncarboxymethyl chitosan. The best carboxymethylating conditions as follows: absorb dose of chitosan=50 kGy, n(chitosan): n(glyoxylate)=1: 1.5, the initial concentration of chitiosan = 1%, reacting 12 h; the best quaternization conditions are reacting 12 h at 80oC, m(CMC): m(GTA)=1:3. Degree of carboxymethyl substitution of products reached 78% under the best synthesis condition, and the degree of quaternary ammonium substitution reached 54.76%. Antimicrobial test results suggested that the carboxymethyl chitosan’s Minimum Inhibitory Concentration(MIC) against staphylococcus aureus was 0.5%, and the MIC increase to 0.05% after the introduction of quaternary ammonium groups, which increased 10 times before quaternizartion. The MIC of carboxymethyl chitosan and quaternized carboxymethyl chitosan synthesized by irradiated chitosan increased to 0.25% and 0.025% respectively.Chitosan biguanidine acetate(CBA) was synthesized by introducing biguanidine onto γ-ray irradiated chitosan.The best synthetic conditions as follow: absorbed dose of chitosan = 50 kGy, n(chitosan): n(CH3COOH)=1:3, n(chitosan): n(Dicyandiamide) =1:3, t = 2 h, t = 90oC. Biguanidine groups were successfully introducing onto chitosan under these conditions, the CBA’s degree of biguanindine substitution is 7.1%. CBA can easily solve in water while the p H range from 1 to 14. The experiment results indicat that the yield of CBA increase evidently after irradiation of chitosan. However the main chain structures of chitosan and CBA have no change.The MIC of CBA against staphylococcus aureus was 0.25%, CBA has the equal antimicrobial property with chitosan biguanidine hydrochloride(CBH), and is non-toxic for mice oral intake and nonirritant for rabbit skin.Quaternary carboxymethyl chitosan and chitosan biguanidine actate can be used as biological antibacterial material, and have good application prospects in food industry、 pharmaceuticals industry、 agriculture and textile finishing.