Design And Evaluation Of Oral Insulin Delivery System Based On Phospholipid Complex

It has been the focus of the research works and problem urgently needed to be resolved that improving the relative low entrapment efficiency and oral bioavailability of protein and peptide agents. In this paper, insulin was complexed with phospholipid and subsequently loaded into oil solution, polymeric nanoparticles and self-complex nanopartilces. The hypoglycemic effects of these delivery systems were also evaluated.Insulin-phospholipid complex was prepared with nonaqueous solvent-freezed drying method. The optimal composition and prepare conditions were obtained by phase diagram investigation. It was proved that insulin activity has not been destroyed during the prepare process by hypoglycemic test. IR analysis showed that there existed some interaction between insulin and phospholipid in the complex, but no new characteristic absorption peaks were observed, which indicated that no new covalent bonds were formed. X-ray diffraction analysis exhibited that the complex was in an amorphous form. The solubility of insulin was improved after it was complexed with phospholipid. The apparent partition coefficient of insulin complexed with phospholipid was related to the ionic strength and pH of aqueous dispersion medium. Low ionic strength and pH closed to the isoelectric point of insulin (pI5.3) will be favourable to the binding stability of complex.Insulin-phospholipid complex loaded polymeric nanoparticles (Ins-SPC NP) was prepared by the modified emulsion-solvent evaporation method. Simple factor experiment was employed to obtain the optimal composition and prepare condition. Spherical particles of 225 nm mean diameter, with 90.2% of drug entrapment efficiency and 2.32% of drug loading efficiency, were obtained under optimal conditions. Surface zeta potential analysis showed that the particle was negative charged, which was always enhanced after drug loaded and suggesting interaction between insulin and particles matrix was occurred. Spectrofluorometry suggested that there existed extensive affinity between insulin and nanoparticles containing phospholipid. The research result of drug loading mechanism proved that insulin was mainly combined with particle matrix by adsorption pattern, which contributed over 50% drug loaded. The in vitro drug release was characterized by an initial burst and subsequent delayed release in both pH 6.8 and pH1.2 dissolution mediums.Insulin-phospholipid complex nanoparticles (CNP) were prepared. Simple factor experiment was employed to obtain the optimal composition and prepare condition. Spherical particles of 258 nm mean diameter, with 78.5％of drug entrapment efficiency, were obtained under optimal conditions. After coated with chitosan, 72.39％of drug entrapment efficiency and 396 nm mean diameter was obtained. With increase of drug loading, the absolute value of zeta potential was decreased accordingly, which suggests that the interaction was occurred between the amino group of insulin and phosphate group of phospholipid. The result of in vitro drug release showed sustained release belabor was displayed in complex nanoparticles after coated with chitosan.The hypoglycemic effects of the three delivery systems were further evaluated in normal and diabetic rats. Both the two kinds of oil solution have week hypoglycemic effects in normal rats, the oral relative bioavailability were calculated to be 0.23％(OIL)和2.68％(EmuI-OIL) respectively. Their hypoglycemic effects were improved after enteric administration, the oral relative bioavailability were calculated to be 0.82％(OIL)和3.49％(Emul-OIL) respectively. Ins-SPC NP has significant hypoglycemic effect in normal and diabetic rats, the oral relative bioavailability were calculated to be 14.32％and 8.69％respectively. Serum insulin analysis showed 7.7％of relative bioavailability was obtained after oral administration of Ins-SPC NP to diabetic rats. Although no significant hypoglycemic effect was observed after oral or enteric administration of CNP, application of certain enhancer with CNP could decreased blood glucose level markedly, 12.06％and 19.78％of relative bioavailability were obtained after oral and enteric administration of CNP containing 1％enhancer. After coated with chitosan, the hypoglycemic effects of CNP was sustained and the relative bioavailability was calculated to be 16.82％.The innovation opinion of this thesis: 1) proposed a kind of consideration to improve the lipophilicify of protein drugs by forming phospholipids complex with a novel nonaqueous solvent-freezed drying method. 2) The complex-loaded oil solution has a good application perspective for its simple prepared method. 3) proposed a kind of consideration to improve the hydrophilic drug entrapment efficiency by phospholipids complex, the exploratory study was employed through prepared method, drug load mechanism, in vitro and in vivo evaluation.