Cellular Uptake And Anticancer Activity Of Lipid Nanoparticulate Carriers

Solid lipid nanoparticles (SLN) are colloidal carrier system for controlled drug delivery and followed by the development of emuson, liposomes, microparticles and nanoparticels based on synthetic polymers. Compared with traditional carriers, the SLN combine the advantages of polymeric nanoparticles and o/w fat emulsions for drug delivery administration, such as a good tolerability, a high bioavailability by oral administration. Nanostructured lipid carriers (NLC) composed of a solid lipid matrix with a certain content of liquid lipid is a new generation of solid lipid nanoparticles (SLN). NLC can avoid or minimize the potential problems associated with SLN such as limited drug loading capacity, adjustment of drug release profile and potential drug expulsion during storage. The incorporation of liquid lipids to solid lipids leads to massive crystal order disturbance. The resulting matrix of lipid particles shows great imperfections in the crystal lattice and leaves enough space to accommodate drug molecules, thus, leading to improved drug loading capacity. In addition, by controlling the amounts of liquid lipids added to the formulation, the controlled drug release can be achieved.The conjugate of otcadecylamine-fluorescein isothiocyanate (ODA-FITC) was synthesized by the reaction between isothiocyanate group of FITC and the amino group of ODA, and was used as fluorescence maker to incorporate into lipid nanoparticulate carriers. The cellular uptakes of fluorescence labeled SLN with different lipid material were evaluated by fluorescence microscopy and the measurement of fluorescence intensity, using the A549 cell-lines as model cell-lines. The order of cellular uptake ability was glycerol tristearate SLN > monostearin SLN > stearic acid SLN > Compritol 888 ATO SLN (ATO888 SLN). Chosing paclitaxel as model drug, prepare the paclitaxel loaded SLNs with different lipid material to investigate their size, zeta potential, entrapment efficiency (EE) and drug loading (DL) and the relationship between the cellular uptake and the cytotoxicities of paclitaxel loaded SLN with different lipid material. The cellular cytotoxicities of paclitaxel were highly enhanced by the encapsulation of lipid matrix. Due to the lower drug entrapment efficiency of glycerol tristearate SLN, monostearin SLN was considered as the best lipid material to improve the cellular cytotoxicity of drug. The polyethylene glycol monostearate (PEG-SA, the polymerization degree of ethylene glycol is 40) was further introduced into monostearin SLN. The PEG modified SLN could enhance the cellular uptake of SLN by the membrane disturb ability of PEG chains on the SLN surface, however, the cellular cytotoxicity of paclitaxel loaded SLN did not show the enhancement.The intracellular accumulation may be further optimized through receptor-mediated endocytosis of the paclitaxel loaded nanoparticles (NPs). The amount and activity of folic acid receptor in the membrane of cancer cells was higher than normal cells. In this study, the conjugate of folic acid-stearic acid (FA-SA) was synthesized to incorporate into NPs for the folate targeting with the hope of facilitating the cellular uptake and cytotoxicity. The study demonstrated that folate modified monostearin SLN could enhance both the cellular uptake and cytotoxixity of drug by improved endocytosis mediated by folate receptor.Herein, monostearin nanostructured lipid carriers with various oleic acid (OA) contents were prepared by solvent diffusion method in an aqueous system. FITC-ODA was used as fluorescence maker to incorporate into NLC. Using the A549 cell-lines, the cellular uptakes of the NLC were qualitatively and quantitatively evaluated by employing fluorescence microscopy and the measurement of fluorescence intensity, respectively. The results indicated the cellular uptake of NLC increased with the incorporation amount of OA. The drug loaded NLC was then prepared by using paclitaxel as a model drug. The NLC exhibited improved drug entrapment efficiency and drug loading capacity by increasing OA content. The in vitro drug release rates were enhanced with the increasing of OA content. In vitro cellular cytotoxicity tests demonstrate the blank NLCs were low cellular cytotoxic carriers. The cellular cytotoxicities of paclitaxel loaded NLC were enhanced significantly comparing with free drug, and increased with the increasing of OA content. For the folate targeting, the conjugate of folic acid-stearic acid (FA-SA) was further synthesized to incorporate into NLC. The cellular uptake and cytotoxicity were highly facilitated by the incorporation of FA-SA in NLC. The folated NLC loading paclitaxel could improve 86 times against the free drug, which originated from the higher internalization of drug via the transport of folated NLC.The multidrug resistance (MDR) is the critical point responding for most failure of human cancer chemotherapy. Corresponding to the literature, a key role was p-glycoprotein (p-gp), which efflux out the drug (mainly the hydrophobic drug such as paclitaxel and doxorubicin) through ATP-dependant transport leading to intracellular deficiency concentration of drug. Some study supposed that NPs delivery system may protect the encapsulated drug into cells from P-pg's efflux out and overcome the drug-resistance.The object of this study is to determine whether anticancer drugs incorporated in lipid nanoparticles can enhance the cytotoxicity and reverse the resistance of drug resistant carcinoma cells. The cytotoxicity of doxorubicin (DOX) or paclitaxel (PTX) against human breast cancer MCF-7 cells and derived multidrug resistant cells (MCF-7/ADR) was investigated. Comparing to free drug solution, encapsulated in SLN and NLC efficiently enhanced the cytotoxicity of both PTX and DOX against MCF-7 and MCF-7/ADR cells, and the reversal power of PTX -SLN and DOX-SLN were respectively 31.0 and 4.3 folds, while the reversal power of PTX-NLC and DOX-NLC were respectively 34.3 and 6.4 folds. Modified with FA-SA, NLC presented enhanced reversal power in MCF-7/ADR cells, which were 52.2 folds for folated PTX-NLC and 8.3 folds for folated DOX-NLC.