Preparation, Characterization And Application Of Chitooligosaccharide Grafted Copolymer

Chitosan (CS) and polylactide (PLA) were known as biocompatible and biodegradable biomedical materials. However, the extended application of chitosan and polylactide are frequently restricted by their limitations. The affinity to proteins, peptides, genes and cells of PLA can be enhanced by introducing the ammo-containing polysaccharides. So the graft copolymers combined the virtues of natural and synthetic polymers, and are expected to have better applications in biomedical and pharmaceutical fields like drug controlled release, genonic vector, tissue engineering, and so on. Therefore, chitosan grafted biodegradable synthetic polymer has attracted people's attention.The developments of synthesis and application of chitosan derivatives were reviewed. The graft copolymer was synthesised by chitooligosaccharide (LCS) and lactide. The modern analysis methods were used to characterized the chemical structures of the products, including high performance liquid chromatoghaphy (HPLC), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), nuclear magnetic resonance (NMR) and elementary analysis. The releasing behaviors in vitro of PLA-LCS drug-loading microspheres have been studied, by using the protein model drugs——bovine serum albumin (BSA) .The following are the main contents and cpnclusions:1. Chitosan was hydrolyzed to give chitooligosaccharides by alpha-amylase. HPLC FT-IR and TG analysis shows that the molecular weight of degradation products decreases, thermostability was lower. But the structure of chitosan was not changed.2. D, L-lactide was prepared by D, L-lactic acid with zinc dust as a catalyst. The melting point of the crystal was 126°C by melting point determination apparatus. The structure of the expected lactide was proved by FT-IR.3. A graft copolymer of chitooligosaccharides and lactide (LCS-LA) was prepared by solution polymerization using dimethyl sulphoxide as solvent, stannous iso caprylate as catalyst. The detailed molecular structure of LCS-LA was characterized by FT-IR,NMR, DSC, and so on. The results showed that the lipotropy of graft copolymer was stronger as the amount of lactide increased. The particle size of copolymers in aqueous solution was measured by laser particle size analyzer (LPSA), and their average diameters was about 299 nm.4. Poly (D, L-lactide) (PLA) and chitooligosaccharide were chosen to microencapsulate bovine serum albumin (BSA) by emulsification-solvent evaporation method. The results of characterizing BSA-loaded nanoparticles (NPs) prepared according to the optimized formulation showed that the mean size of NPs was 316 nm, encapsulation efficiency reached 85.7%, and BSA-loading level was 12.11%, respectively. The determination of its release rate in vitro revealed it was in sustained release except an abrupt release in the initial 30minutes. Release curve conform to the Higuchi equation.5. Chitosan with free amino groups reacts with lactose to form Maillard products. All pHs, tempertures times and reactants' molar ratios affecting the reaction content and rate were tested, respectively. The antioxidant activity of Maillard reaction products (MRPs) was evaluated with scavenging abilities against superoxide anion which was created by the system of riboflavin-methionine-NBT. The results showed that the reaction rate was fastest when the reactants' molar ratio (lactose : chitosan) was 1 : 1.5, the pH values was 5-6 and the reaction temperture was 80℃. The MRPs showed good ability for scavenging the superoxide anion radical, and the ability was increased as the amount of the MRPs increased.