Preparation And Properties Of Modified Starch And Its Derivatives

Starch and its derivative have many advantages,which are extensive,cheap,environmentally friendly,biodegradable.Modification of starch can obtain products that meet the need of people.Collagen peptides own better biological activity,which is widely applied in the field of pharmaceuticals industry and food industry.In this paper,Microbia transglutaminase(MTGase)was as a biocatalyst,which could catalyze starch derivatives were conbined with collage peptides.New materials which had the capacity of antioxidant and promote the cells viability were prepared.This was in order to lay the foundation for the preparation of new biomedical materials.The contents and results in this paper are as follows:(1)Aminoethyl starch(AES)was obtained by grafting 2-chloroethylamino hydrochloride onto starch backbone.By one-factor-at-a-time experiment,we could obtain the optimal contidions: the reaction temperature was 75 ?,the reaction time was 20 h,the mass ratio of 2-chloroethylamino hydrochloride to starch was 2.0.The water solubility test showed that the starch had good water solubility after aminoethyl group was introduced onto starch,and the more content of amino was,the better solubility of aminothyl starch would be.When the content of amino was 9.88%,the transmittance of aminothyl starch reached about 85%,while the content of amino was 4.36%,the transmittance was reached about 55%.In addition to,we come a conclusion that the more concentration of the sample was,the less transmittance would be.In a word,the solubility of starch was significantly improved after starch was modified with aminoethyl group.The antibacterial activity of AES was indicated that it had a certain inhibition to Escherichia coli and Bacillus subtilis at weakly acid pH while it had no inhibition at the pH is 7.(2)Aminoethyl starch collagen peptides(AES-COP)was prepared with MTGase which was as a biocatalyst.The reaction conditions were optimized.The optimal conditions were obtained as follows: the reaction temperature was 45 ?,the reaction time was 1 h,the mass ratio of collagen peptides to AES was 1.0.Antioxidant test and cell avibility assay were conducted.The antioxidant test showed that AES had no or little antioxidant.However,AES-COP exhibited a certain antioxidant activity.With the DS and concentration increasing of AES-COP,the radical scavenging activity increased.And it was proved that the collage peptides had the ability to scavenging activity.The results of cell viability of fibroblast indicated that AES-COP could sharply promote the growth of the cells when the product at a suitable concentration.While the concentration was too high,the cell viability would show some cytotoxicity.What's more,we found that the cell viability could up to 127% when the DS was 0.436 and the concentration was 0.05 mg/ml.(3)Collagen peptides grafted aminoethyl hydroxypropyl starch(AEHPS)was prepared by an enzyme-catalyzed reaction in the presence of microbial transglutaminase(MTGase).AEHPS was synthesized with 2-chloroethylamine hydrochloride(CEH)which was as an intermediate reactant.The parameters,which influenced the degree of substitution(DS),including reaction time,reaction temperature and the mass ratio of the reactants were investigated.Antioxidant activities of AEHPS-COP were evaluated by the scavenging activity of hydroxyl and 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical.With the DS and concentration increasing of AEHPS-COP,the radical scavenging activity increased.The Methylthiazol tetrazolium(MTT)assay indicated that AEHPS-COP could promote the viability of L929 cells at a suitable circumstance.The cell viability could up to 129% when the DS was 0.576 and the concentration was 0.1 mg/ml.