Effect of Octreotide-Polyethylene Glycol(100) Monostearate Modification on the Pharmacokinetics and Cellular Uptake of Nanostructured Lipid Carrier Loaded with Hydroxycamptothecine

A new conjugate, octreotide-polyethylene glycol(100) monostearate (OPMS), was developed for the enhancement of targeting delivery of hydroxycamptothecine (HCPT) loaded in nanostructured lipid carrier (NLC). 2. x 10(-3) and 5 x 10(-3) mmol of OPMS were respectively used to modify NLC so that the targeted nanocarriers with low and high ligand density were obtained. For comparison, the pegylated NLCs without octreotide were prepared by adding equal molar amounts of polyethylene glycol(100) monostearate (PGMS). The relation between the modification levels and properties of various NLCs were studied in vivo and in vitro. At a high modification level, a slower release rate of HCPT and the more stable nanocarriers was achieved. At the same time, the fixed aqueous layer thickness (FALT) and average surface density of PEG chains (SDPEG) was increased, but the distance (D) between two neighboring PEG grafting sites became narrower. The in vivo pharmacokinetic study in healthy rat indicated that the modified NLCs had a longer circulation than NLC (P < 0.05) due to pegylation effect and OPMS modified NLCs had larger MRT and AUC(0-t) than that of PGMS modified NLCs at the same modification level. Furthermore, the florescence microscopy observation also showed the targeting effect of octreotide modification on somatostatin receptors (SSTRs) of tumor cell (SMMC-7721). The uptake of SMMC-7721 was much more than that of normal liver cell (L02) for OPMS modified NLC, and the highest uptake was observed for 5 x 10(-3) mmol of OPMS modified one. No obvious difference was found among the L02 uptake of OPMS modified NLCs and NLC, but their uptake was higher than that of PGMS modified NLCs. All the results indicated that the OPMS highly modified NLCs would improve the effect of antitumor therapy by inhibiting the degradation, evading RES and enhancing the drug uptake of tumor cells.