Preparation And Preliminary Study Of Polyelectrolyte Complex Of Carboxylic Derivative Of Starch-Chitosan

The ployelectrolyte complex (PEC) is a kind of novel material that has been developed in recent years. PEC exhibits much more remarkable properties in comparison with mono-component polymer. It is well known that both starch and chitosn are abundant naturally occuring biogradegrable biopolymers. Moreover, chitosan is the only naturally existing cationic polysaccharide that possesses excellent bioactivity. Starch can be chemically modified and transferred into anionic polysaccharicde. Then, a novel biomedical material can be prepared via the interaction of hydrogen bond and/or electrostatic force between two ploylectrolytes. In view of that, experiments are performed and the results are shown as follow.First, two approaches are used to incorporate numerous carboxylic groups (ca. 8-32%) onto starch chains. The esterification reaction of starch with maleic anhydride is a way to provide wider range of the content of carboxylix groups but using organic agents such as pyridine and N, N-Dimethylformamide. The other method is Fenton's reagent intitated graft copolymerization of starch with maleic acid, which can be carried out in a mild condition and all product are water-soluble. To our knowledge, no similar report is found. The structure of carboxylic derivative of starch obtained by two approaches is confirmed by FTIR, TGA and XRD measurements.Then, carboxylic derivative of starch and chitosan of different feeding ratio are blended in solution to form blend membranes. The films are ready to form and no marco- or micro- phase separation is found, which has the advantage over that of chitosan/starch blend. The FTIR, TGA, DSC and fluorescent spectrometry analysis results of the blends indicated that there are interactions such as hydrogen bond and electrostatic force between carboxylic groups and amino groups of chitosan and carboxylic derivative of starch. As a result, the film-forming property, compatibility, and thermal stability of carboxylic derivative of starch/chitosan is better than that of chitosan/starch.The third part of this study presents an interesting fact. A novel polyelectrolyte complex is formed by mixing chitosan with the solution of carboxylic derivative of starch that contains higher carboxylic groups (16% or above). The results of FTIR, XRD, TGA and elementary analysis suggested that the driving force of self-assembly is the electrostatic interaction between carboxylic and amine groups of two components. The release behavior of the polyelectrolyte complex that contains 5-fluorouracil (5-Fu) is examined in buffer solution. It is found that the cumulative release of 5-Fu depends on the pH value of buffer saline and can be adjusted with the feeding ratio of components. Thus, such a PEC can be considered as a potential matrix for drug controlled-release.