Development Of Bioadhesive Microspheres Of Silybin And Study Of Its Bioavailability

The project mainly develeped the establishment of analytical methods, study on preparation,evaluation of quality and study on bioavailability of bioadhesive microspheres of silybin. In the establishment of analytical methods,the methods of determining the encapsulation efficiency , adhesive strength and the in vitro release of bioadhesive microspheres of silybin were established.These methods proved to be suitable for control of the quality of microspheres by verification. In the study of preparation, the concentration of sodium alginate, the concentration of calcium chloride, the specifications of syringe needles, the gelation time and drying methods that effect on the nature of microspheres respectively was investigated. The experimental results show that the particle size of microspheres was influenced by two factors.They respectively were the diameter of needle and drying method. The diameter of needle is larger, the particle size of the microspheres is the greater. The particle size of microspheres after freeze-drying remain the same as before drying. The particle size of microspheres after heat-drying was narrowed by about 50%. Encapsulation efficiency was basically not effected on the above five factors. Adhesive strength was mainly influenced by the four factors. Namely, the concentration of sodium alginate, the concentration of calcium chloride, needles specifications, drying methods, and basically was not influenced by gelling time. The in vitro release was mainly influenced by the concentration of sodium alginate, the concentration of calcium chloride, the specifications of syringe needles, the gelation time. On this basis, three main factors of the concentration of sodium alginate, the concentration of calcium chloride, the specifications of syringe needles were optimized by orthogonal designs .The best prescription and precedure were that the concentration of sodium alginate was 1.5%, the concentration of calcium chloride was 0.1% and the specifications of needles was 7# from the results of optimization. The three batches of microspheres were prepared by the best prescription and precedure and quality of the microspheres was studied from the appearance, the shape, the drug loading, the rate of residence and in vitro release. These microspheres were largely spherical. Their surfaces were smooth and slightly concave but can restore to the spherical shape before drying in the presence of metal ions. The average drug-loading of three batches of samples were 52.11%, RSD was 1.7%.This showed that the prescription and precedure were stable. The average residence rate in the small intestinal mucosa in vitro was 94%. This showed that the adhesive strength of the microspheres was good. The in vitro release of the microspheres was pH-dependent. Silybin was not almost released from microspheres in 0.1 mol / LHCL. The dissolution profiles of silybin from microspheres in PH6.8 phosphate buffer solution was fitted with a kinetic characteristics (relative coefficient was 0.9999).Besides, the analytical method of concentration of silybin in plasma was also established. The established chromatographic conditions was that column was Agilent C18 (4.6mm×250mm, 5um), a mobile phase was methanol -20mmol/LKH2PO4 buffer solution (PH = 3.0) (45:55), the temperature of column was 40℃, detective wavelength was 288 nm, flow rate was 1ml / min and injection volume was 50μl. The recoveries of high, medium and low concentration were 86.7%,88.7%,89.2% respectively. Sample recoveries were 88.0%,90.3%,91.0% respectively. Intra-day RSD were 1.13%,2.42%,5.57% respectively. Inter-day RSD were 1.61%,3.03%,6.12% respectively. Quantitative minimum concentration was 50 ng / ml. Above results showed that the established method was suitable for determining the plasma concentration of silybin. Bioavailability in animal vivo was studied by a randomized and controlled study. New Zealand rabbits were used as the tested subjects and suspensions of silybin being fast-release formulations was used as control. Relative bioavailability was 770% between bioadhesive microspheres and suspensions of silybin.The result showed that bioadhesive microshperes promoted the absorption of silybin and increased its oral bioavailability.