Preparation And Pharmacodynamics Of Insulin-loaded Solid Lipid Nanoparticles

In recent years, solid lipid nanoparticles (SLN) are alternative colloidal carrier system for controlled drug delivery. In the present report, Insulin-loaded solid lipid nanoparticles were prepared by a novel solvent diffusion method in an aqueous system. The model peptide insulin was incorporated to study the entrapment efficiency, size, zeta potential and drug delivery characterization. Covalent conjugation with fluorescein isothiocyanate (FITC) yielded labeled octadecylamine molecules, which was investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) measure. The optimal cryoprotectant was selected by freeze-thaw test and reconstitution of lyophilized products. In the buffers of pH 7.4, the release profiles of insulin from octadecylamine SLN were investigated. To study the intestinal transport, the insulin-loaded SLN were given by gavage. After pulmonary administration to the diabetes animal model, the blood glucose response was evaluated in diabetic male SD rats in vivo.Stearic acid nanoparticles were quickly prepared by a novel solvent diffusion method in aqueous system. The average volume diameters of nanoparticles were300-500nm and the zeta potential was -21 mV dispersed in distilled water. In the medium with different pH values by 3.5, 5.3, 7.5, the insulin encapsulation of nanoparntials were 10.7%, 12.2%, 10.3%, respectively. Aluminium chloride with the positive charges can make nanoparticles aggregation and segregation.Octadecylamine nanoparticles prepared by ionotropic gelation with tripolyphosphate (TPP) anions can improve drug encapsulation efficiency to 84.3%. The average volume diameter of insulin-loaded SLN was 365.1 nm and the zeta potential was 2.3 mV. Poloxamer, manicol and glycocol with different concentration of 0.1 %, 0.3%, 0.5% were proved to be most effective during freeze-thaw test and were therefore selected for the lyophilization studies. The reconstitution of the lyophilized products was performed. Change in particle size distribution during lyophilisation could be minimized by using manicol with the final concentration of 0.5% as cryoprotectant.In the test solution of a pH 7.4 phosphate buffer (simulative intestinal fluid), the drug-release behavior from SLN suspension exhibited a biphasic pattern. After burst drug release at the first 1 hour at a percentage of 35.63% of loaded insulin, a distinctly prolonged release over a monitored period of 24 hours at a percentage of 67.30%. It indicated that the internal structure of the SLN was a polymeric lipid matrix and indicated a long drug release.The bioavailability of insulin-loaded SLN after pulmonary administration was 95.54% with that of subcutaneous injection as reference, which was similar to the same dosage of insulin solution. The glucose concentration given by insulin-loaded SLN was only up to 80% after 12 hours. But the glucose concentrations of insulin solution by injection or pulmonary were up to the level before administration. These results also demonstrate the principle suitability of SLN as a prolonged release formulation for hydrophilic peptide drugs.The DSC and IR investigation demonstrated that the new compound synthesizedwith octadecylamine and FITC has three absorption bands of amide group signals, which can testify that the compound contains an amide group based on the reaction. After the fluorescent-label nanoparticles given by gavage, the fluorescence strength of lymph was much higher than blood. The result showed that SLN could significantly absorb into intestinal lymph after orally administration.