Preparation And Oral Bioavailability Of Progesterone Loaded Lipid Nanoparticles

Nanoparticles made from solid lipids, the so-called solid lipid nanoparticles (SLN) attract the attention of research groups as an interesting parenteral carrier system. An outstanding advantage of solid lipid nanoparticles (SLNs) over traditional polymeric nanoparticles is the fact that the lipid matrix is made from physiologically tolerated lipid components, which decreases the potential for acute and chronic toxicity. SLN combines the advantages of polymeric nanoparticles such as controlled drug release and avoiding drug leakage, and the advantages of emulsions and liposomes, such as low toxicity, good biocompatibility and higher bioavailability. However, there were some associated problems, including limitation in drug loading capacity, drug expulsion during storage and high water content of aqueous SLN dispersions (70-95 %).To overcome the limitations, nanostructured lipid carriers (NLC) are developed in recent years. NLC are produced by controlled mixing of solid lipids with spatially incompatible liquid lipids leading to special nanostructures with improved properties for drug loading, modulation of the drug release profile and stable drug incorporation during storage. The incorporation of liquid lipid to solid lipids leads to great imperfections in the crystal lattice of nanoparticles, and thus leading to improved drug loading capacity and reduced drug expulsion during storage. Especially the drug has a good solubility in the liquid lipids, the drug entrapment efficiency and drug loading will be improved clearly.The progesterone was used as a model drug to prepare drug loaded lipid nanoparticles. The effects of preparation method, the compound of lipid on lipid on the particle size, drug encapsulation efficiency and release behaviors were also investigated. Three release methods including the suit drug release medium re-dispersion, the diffusion cell and dialysis bag were studied to evaluate the drug release profile from lipid nanoparticles. After the above study, we hoped to get lipid nanoparticles with good drug loading ability and slower release profile. Then the progesterone loaded NLC was prepared by melt-emulsification method, in which monostearin (MS) and stearic acid (SA) were used as solid lipids, and oleic acid (OA) was used as liquid lipid. The properties such as particle size and its distribution, drug loading, drug encapsulation efficiency and drug release behavior of obtained NLC were compared with that of SLN and the NLC prepared by solvent diffusion method. The effect of the liquid liqid content, charged amounts for drug and PEG modification on the particle size, zeta potential, drug loading, drug encapsulation efficiency and release behaviors were also investigated. HPLC was used for the determination of drug content; ~1H-NMR spectrum was then used to analyze the PEG-SA content in NLC.NLC dispersion was administrated orally, the bioavailability and drug-time curve were investigated. We selected HPLC to determine the concentration of progesterone in the plasma, selected Danazol as the internal standard material. To reduce the effect of the progesterone produced by nature in the rate, two ovary of the female rate was removed, the progesterone oil solution was used as the control group, we studied the drug-time curve and the bioavailability after NLC dispersion was administrated orally. Then we compared the bioavailability of PEG modified NLC, to prove the long circulation in blood resulted from the PEG.Lipid nanoparticles produced by solvent diffusion method was with low drug encapsulation efficiency, which is 45.9%, the drug release exhibited biphasic pattern with burst release at the initial stage and sustained drug release. The phenomenon indicated that the drug mostly located at the shell of lipid nanoparticles. The drug encapsulation efficiency of lipid nanoparticles prepared by melt-emulsification was higher, which is 77.48%; the nanoparticles can release the drug slowly. The release methods were found: the medium re-dispersion can't release drug completely; the diffusion cell prevented the diffuseness of the drug molecule; dialysis bag could make drug through the bag faster, did not affect the release profile of the lipid nanoparticles seriously.The study of NLC produced by melt-emulsification proved: The incorporation of liquid led the bigger particle size, and the higher EE, the EE was from 55.35% to 81.32%; the drug release rate of NLC was faster than that of SLN; the faster release occurred with the more amount of OA added. The NLCs with different amounts of charged drug were produced to investigate the drug loading capability of NLC. Although the EE of NLC decreased with the increasing amounts of charged drug, the DL could be highly improved. The drug release rate of NLC enhanced with the increasing of DL, especially the NLC with 11.57% drug loading. PEG-SA was used to prepare the PEG modified NLC, ~1H-NMR spectrum was then used to analyze the PEG-SA content in NLC, about 80% PEG-SA was incorporated into lipid matrix. The PEG modified NLC showed smaller particle size, the drug release rate of NLC increased with the PEG-SA content in NLC, about 90% drug was released in 24h. The drug release rate of NLC increased with the PEG-SA content in NLC.In vivo study was used rats administrated orally, the drug loaded NLC was prepared by melt-emulsification method. There are two peaks in the drug-time curve, the first one was appeared at about 2h. Compared with control group, the second one occurred later due to the absorption via lymph after oral administration, appeared at 8h or so. The curve variety of PEG modified NLC occurred was similar to that of the NLC, which showed there was the same absorption route for NLC and PEG modified NLC. The bioavailability of NLC was 1.93% compared with control group, while that of PEG modified NLC was much higher, that is 2.53%. The concentration of drug was higher in a long time, which can prove that the PEG modified NLC can exist in blood for a long time.