The Preparation And Application Study Of A Water-soluble Chitosan Derivative

Chitosan is biocompatible, biodegradable, bio-adhesive, and has low toxicity, Therefore, in the biomedical field has broad application prospects. However, chitosan is not soluble in water, alkali (pH> 6.5) and general organic solvents, can only dissolve in some inorganic acids and organic acids, such as hydrochloric acid, sulfuric acid, formic acid, acetic acid, tartaric acid and citric acid, thus chitosan is limited in biomedical application domains for the poor solubility。It is necessary to study its various modification to further expand the application scope of chitosan and develop novel and excellent medical polymer materials. A new water soluble chitosan derivative was synthesized, and the chemical structure, molecular weight, solubility, moisture absorption, moisture retention, antibacterial activity, metal ion adsorption, enzyme encapsulation were studied. This thesis mainly includes three parts:1. A new water soluble chitosan derivative was synthesized. At mildly alkaline pH values, such as Ph 8～8.5, alkyl halides such as monochloroacetic acid react preferentially with the amine groups of chitosan rather than with the hydroxyl groups, thus forming N-carboxymethylated chitosan derivatives. The influence of reaction conditions on N,N-dicarboxymethylchitosan (N,N-DCMC or DCMC) were investigated through orthogonal design, such as reaction time, temperature, weight ratio between chitsoan and monochloroacetic acid,then the best conditions were found.Fully substituted N,N-dicarboxymethylchitosan was obtained by the alkylation of chitosan at pH 8～8.5, 90℃for 3 h with monochloroacetic acid (1:4 weight ratio). And the chemical structure, molecular weight, solubility, moisture absorption, moisture retention were studied. 2. A water-soluble N,N-Dicarboxymethylchitosan with high degree of substitution was prepared, as well as its zinc, silver, copper salts.The adsorption properties of DCMC was investigated in relation to its adsorption behavior for Zn2+,Cu2+ and Ag+. The adsorption conditions include the time,temperature,pH value were studied. Then test the antimicrobial activity against Staphylococcus aureus and Escherichia coli, while compared with sodium benzoate. Results show that chitosan, DCMC and its zinc, copper, silver salts have good antibacterial activity compared with sodium benzoate.3.α-Amylase as a model, the enzyme encapsulation property of DCMC was studied. In the reaction between starch andα-Amylase, the reductive product of starch can reacted with 3,5-dinitrosalicylic acid to produce a product with specific absorption wavelength of the absorbance. The enzyme activity and quantity can be measured with the absorbance of the product of 3,5-dinitrosalicylic acid, and then determine the amount of enzyme which was encapsulated by DCMC. The results show that DCMC has good encapsulation efficiency onα-amylase, So DCMC may be used as a new carrier in protein drug delivery system.