Study Of Lipid-based Nanoparticle Drug Carrier Prepared By Supercritical Assisted Atomization

Solid Lipid Nanoparticles(SLN) is one of micronized drug carriers, which developed since 1990s, and Supercritical assisted atomization(SAA) is a novel supercritical technology for microparticles preparation appeared within recent 10 years. In this study, SAA technology was applied to prepare the SLN encapsulating drug. SAA was found to improve the productivity, reduce solvent residue, and to gain high drug-loading, size-controllable SLN, and seems to be a promising method for lipid nanoparticles preparation.A novel SAA particle-producing equipment was designed based on SAA principle. Using ethanol as an assisted solvent, stearic acid SLN was prepared by this equipment. The effect of lipid concentration, flow ratio of supercritical CO2 and lipid solution and pore size of nozzle, on the particle size of resulted SLN were investigated to explore the appropriate process conditions. The results showed that SLNs with bigger size were obtained when lipid concentration in saturator was higher. When lipid concentration was 1.0% w/v or lower, particle size was smaller than 1μm. When the lipid concentration was lower than 0.5% w/v, diameter of SLN was below 500 nm. Flow ratio of SCF CO2 to lipid solution was negatively correlated with particle size, SLN with below 1μm size was obtained when the flow ratio was 1:1. SLN with below 500 nm size was obtained when flow ratio was more than 3:1. However the particle size was positively correlated with pore size of nozzle. When nozzle size is 0.2 mm or lower, the size of SLN was lower than 400 nm, the size distribution was narrow. The mnostearin SLN prepared by SAA equipment had similar physio-chemical properties with stearic acid SLN.Based above optimal process conditions, insulin, a hydrophilic macromolecule drug, was used as model drug to produce SLN loading insulin (INS-SLN). During SLNs preparation, both stearic acid, monostearin, were choosed as matirx, with or without modified by hydrophilic polymers such as poloxamer and PEG 2000. Physico-chemical properties, such as particle size, zeta-potential, drug entrapment efficiency (EE), loading ratio (DL) and in vitro release profile of SLN were investigated. Mean particle size, EE and DL of INS-SLN was variable from 180 nm to 300 nm, EE from 65% to 80%, and DL 2.8% to 3.8% depending on the fomula, respectively. AFM image showed the INS-SLN was spherical with smooth surface. Unmodified formulation by hydrophilic polymers of SLN was found to be larger size and slower drug releasing profile, and nearly 15% of encapsulated INS couldn't be release within 12 hrs in vitro. Poloxamer used as hydrophilic polymers was introduced to modify the lipid carriers. The modified INS-SLN was smaller (180 nm) and uniform size, but the EE was reduced, and burst release was increased significantly. When poloxamer was replaced by PEG 2000 in monostearin formulation, the particle size and releasing behavior were kept, meanwhile the EE and burst release were improved. Thus the PEG modified formulation was preferred formulation for further in vivo study.Diabetic rats and dogs were established through administration of streptozocin amd/or alloxan, to evaluate the in vivo efficacy of INS-SLN. S.c. injection of INS solution was used as positive control. After oral administration of INS-SLN for 0.5 hr, the blood glucose of rats was decreased, and the maximum hypoglycemic effect of 80% was reached in 8 hr. Relative bioavailability (F) of oral INS-SLN calculated by AAC(0-24h) were 36.4% and 33.3% for dosage of 15 IU/kg and 20 IU/kg. Similar results were observed in diabetic dogs'model, blood glucose was inhibited since 0.5h after administration and maintained for 8 hr or more. Relative bioavailability (F) based on AAC(0-24h) were 27.0% and 21.9% for dosage of 9 IU and 30 IU. Due to the absorption of SLN, the onset time and strength of oral INS-SLN were inferior to s.c. INS injection. However, INS-SLN showed Longer-time hypoglycemic effect (more than 8 hr), which should attribute to extended INS release of SLN. The results indicated clinical development possibility of INS-SLN.