Preparation And In Vitro And In Vivo Evaluation Of Paclitaxel-loaded Oral Polyion Complex Micelles

Paclitaxel (PTX) is a cytotoxic anticancer drugs extracted from the Taxus chinensis and has been demonstrated significant antitumor activity in clinical trials against a broad range of solid tumors such as breast, ovarian and non-small-cell lung cancer. Owing to the poor aqueous solubility of PTX, actually lower than1μg/mL, clinical application of PTX was traditionally limited within intravenous way, which is painful to patients and meaninglessly medical resources-occupied, restricting the clinical application for PTX. However, to improve the oral bioavailability of PTX, the first obstacles is the poor aqueous solubility. Besides, the expression of P-glycoprotein pump (P-gp) reduces the intestinal absorption and accumulation in tumor cell, further reducing the effect of chemotherapy.PTX-loaded F127-GC/NaC orally polyion complex micelles were prepared in the project and the in vivo and in vitro evaluation were investigated with PTX-loaded NaC micelles as the contrast. Potential ability of the F127-GC/NaC micellar system was eventually estimated as an novel drug delivery system for oral administration of PTX. The main works were detailed as follows:1. Synthesis and structure identification of Pluronic F127-chitosan copolymersSuccinic anhydride was used as the bridge molecules between Pluronic F127and chitosan, and the F127-GC copolymers were synthesized. The structure was then identified. Results showed a new peak of carbonyl stretching vibration at1736.16cm-1in the IR spectrum of F127-GC and both typical peaks of chitosan(4.9and3.11) and pluronic(3.65and1.12) in the NMR spectrum of F127-GC, indicating successful synthesis of F127-GC copolymers.2. Preparation and characteristics of PTX-loaded micellesPhysical and chemical properties including particle diameter, drug loading capacity, zeta-potential were used as indicators to select the optimal prescription of PTX-loaded F127-GC/NaC micelles, and the physicochemical characteristics and the critical micelle concentration (CMC) were investigated. Results showed spherical micelles with an average particle diameter of57.5nm and an average potential at-0.27mV. What’s more, the CMC value of F127-GC/NaC micelles was about2.5x10-3mol/L and was obviously reduced compared to the NaC ones, showing a greater stability and stronger antibody dilution capacity.3. In vitro release of PTX-loaded micellesSimulated gastrointestinal fluid containing1%(w/v) Tween-80was used as the release medium to investigate the release properties of PTX-loaded micells in gastrointestinal tract. Result showed PTX-loaded F127-GC/NaC micelles an obvious sustained release effect in both mediums and the accumulated amounts of drug released was within35%at2h and more than80%in SGF and66.78%in SIF after12h.4. Anticancer activity of PTX-loaded micellesCytotoxicity of empty micelles and anticancer activity of drug-loaded micelles in MCF-7/Adr cells were examined using the MTT assay. Besides, cell uptake of the micelles was investigated with Rh123as the model drug. Results showed empty F127-GC/NaC micelles a good biocompatibility at the concentration of lmg/mL with more than90%cells survival after incubation for48h and compared to PTX solution, PTX-loaded F127-GC/NaC micelles performed a stronger anti-tumor activity. What’s more, when entrapped in F127-GC/NaC micelles, cell uptake was significantly enhanced.5. In situ absorption of PTX-loaded micelles in rat intestinal tractAbsorption kinetics of PTX micelles was investigated in rats using in situ perfusion method. Results showed that in the concentration of50-200μg/mL, absorption of PTX in F127-GC/NaC micelles displayed concentration-independent kinetics characteristics. What’s more, Ka of PTX F127-GC/NaC micelles was7.68and1.58times compared with PTX NaC micelles and PTX solution, respectively, exhibiting a higher effect of promoting the intestinal absorption of PTX.6. Pharmacokinetics studies of PTX-loaded micelles in ratsPharmacokinetics characteristics of drug-loaded micelles was studied in rats. Results showed the area under the drug concentration curve (AUC) after oral administration of PTX solution was only0.429mg/L*h. However, after oral administration of PTX NaC micelles and F127-GC/NaC micelles, AUC was promoted to1.262and1.859mg/L*h, respectively. What’s important, relative bioavailability (F%) was raised from8.75%to25.74%and37.91%, respectively.