Preparation Of Low-molecular-weight Chitosan(LMWC) And The Pharmacodynamics Of LMWC Chitosan Nanoparticles Loaded Insulin In Vivo

Chitosan is composed of 2-amino-2-deoxy-h-d-glucancombined with glycosidic linkages. Compared to many other natural polymers, chitosan has high biocompatibility and low cytotoxitity. Recently, several drug delivery systems using macromolecules as drug carriers have been developed for parenteral administration. However, it has been found that the biodegradality of chitosan was slow and incomplete in vivo, which caused the possibility of chitosan accumulation in the human body. Furthermore, recent reports indicated that usage of chitosan was limited because of its low blood compatibility and cell viability, and such drawbacks of chitosan was related to and physicochemical characteristics such as the N-acetylation degree and molecular weight. Low-molecular-weight chitosan (LMWC) has become the focus of investigation.In this study, we chose chitosan (CS) as delivery system material for macromolecules. Chitosan with different molecular weights were prepared using enzymatic degradation. Their molecular weights were determined by viscometry and gel permeation chromatography (GPC). Chitosan nanoparticles were prepared by solvent diffusion method. Several characteristics of chitosan nanoparticles suchas morphology, particle size, Zeta potential and drug entrapment efficiency were evaluated. After the chitosan nanoparticles loaded insulin (INS), the pharmacodynamics after pulmonary administration in vivo was evaluted.Chitosan with different molecular weights was obtained after control the condition of enzymatic degradation and ultrafiltration separation. The molecular weights of chitosan determined by gel permeation chromatography (GPC) was 20kDa.The chitosan nanoparticles prepared by solvent diffusion technique showed a sphere shape and exhibited a narrow particle size distribution, and became smaller after enhanced the proportion of anhydrous alcohol in system or treatment sonication number of times. The particle size distribution also.turned to small when using lower molecular weight chitosan. The nanoparticle system belongs to stable system due to the higher Zeta potentials of chitosan nanoparticle systems (above +30 mV). The average entrapment efficiency of insulin was 95.54+1.14% (n=3) by treatment of high speed centrifugation and filtration, then determined by HPLC. The releasing curve of chitosan nanoparticles loaded insulin showed slow drug releasing. At the first two hour, it showed burst releasing, then the releasing curve was related to zero-class releasing equation of y = 0.8963x + 16.068(R2 = 0.9914).The pharmacodynamics of chitosan nanoparticles loaded insulin in vivo showed that nanoparticles had certain hypoglycemic effect and behaved rapidly. In comparison to the insulin solution, 0.737 times relative bioavailability was observed with the four times dosage of insulin chitosan nanoparticles after pulmonary administration.