Preparation And Evaluation Of Paclitaxel-loaded Self-micelle Solid Dispersion

Paclitaxel,a naturally occurring diterpenoid,is already one of the most widely used natural anticancer drugs due to its unique anticancer mechanism and biological activity.At present,paclitaxel is mainly administered by injection for the treatment of breast cancer,nodal carcinoma and squamous cell carcinoma.Due to the relatively low solubility of paclitaxel,polyoxyethylene castor oil（Cremophor?）and ethanol are often used as solubilizers in injections to dissolve paclitaxel.However,polyoxyethylene castor oil can release histamine from the body and cause severe allergic reactions.Preclinical pretreatment with parabens and antihistamines is necessary,which brings great inconvenience to patients.Compared with injection,oral administration can reduce infusion-related complications and improve patient compliance,so it is currently the most widely used drug.However,paclitaxel is a Class IV drug in the Biopharmaceutical Classification System（BCS）,and its low water solubility and low permeability result in very poor oral absorption of paclitaxel.In the meantime,paclitaxel is a substrate of P-glycoprotein（P-gp）,and P-gp can efficiently recognize paclitaxel and pump it out of cells uniaxially,preventing further absorption by organisms.These two reasons result in very low oral bioavailability of paclitaxel.In this thesis,a kind of paclitaxel self-micelle solid dispersion（PTX-SMSD）was prepared by using amphiphilic polyvinyl caprolactam（PVC）-polyvinyl acetate（PVA）-polyethylene glycol（PEG）graft copolymer（Soluplus^?）and vitamin E polyethylene glycol succinate（TPGS）as co-carrier.On the one hand,PTX-SMSD can effectively improve the solubility of the hydrophobic drug paclitaxel by self-emulsifying in vivo to produce micelles.On the other hand,TPGS is a P-gp inhibitor,which can increase the intracellular concentration of paclitaxel by inhibiting the efflux of P-gp,thereby increasing the oral bioavailability of paclitaxel.Firstly,the solvent evaporation method was used to prepare PTX-SMSD,and the formulation and preparation process of PTX-SMSD were investigated by single factor experiment and Central Composite Design-Response Surface Methodology（CCD-RSM）with the encapsulation efficiency and drug loading of the formed micelles as evaluation indicators.The results showed that PTX-SMSD could form a drug loading capacity of 4.86±0.08%,an encapsulation efficiency of 92.05±1.74%,a particle size of 74.92±1.97 nm,a polydispersity index（PDI）of 0.132±0.026,and a Zeta potential of-19.90±1.07 m V for micelles when dissolved in water.The results of equilibrium solubility test and dissolution test in vitro showed that the equilibrium solubility and cumulative dissolution rate of PTX-SMSD under three p H conditions were significantly higher than those of the bulk drug.Differential scanning calorimetry（DSC）,X-ray diffraction（XRD）and scanning electron microscopy（SEM）were used to study PTX-SMSD.The results showed that the paclitaxel in the solid dispersion was in an amorphous state.In addition,stability experiments showed that PTX-SMSD has good storage stability.Secondly,in the cell uptake experiment,coumarin（COU）was selected as the fluorescent substance,and the difference in the uptake ability of Caco-2 cells to different processing groups was judged by intracellular fluorescence intensity and cell uptake rate.The results showed that the COU-Soluplus^?/TPGS-SMSD group had similar fluorescence intensity and cell uptake rate to the cell group added with the P-gp inhibitor verapamil and had a marked enhancement compared with the free COU group and the COU-Soluplus^?-SMSD group.The results indicated that TPGS has the similar effect of inhibiting P-gp efflux as verapamil,and can inhibit drug uptake by Caco-2 cells.Therefore,it can be speculated that PTX-SMSD can improve the oral bioavailability of paclitaxel by increasing the uptake of paclitaxel by cells.Finally,an HPLC method was established to determine the PTX content in rat plasma,and the raw material drug was used as a reference to study the pharmacokinetics of PTX-Soluplus^?-SMSD and PTX-Soluplus^?/TPGS-SMSD after intragastric administration in rats.The pharmacokinetic results showed that the peak time(T_max)of PTX,PTX-Soluplus^?-SMSD and PTX-Soluplus^?/TPGS-SMSD were3.00?0.63 h,2.50?0.55 h and 2.00?0.38 h,respectively;the peak concentration(C_max)were 0.22?0.02μg/m L,0.27?0.04μg/m L and 0.40?0.02μg/m L,respectively;the areas under the curve(AUC_0-t)were 2.25?0.21μg/m L·h,3.27?0.34μg/m L·h and3.86?0.30μg/m L·h,respectively.The results showed that the PTX-Soluplus^?/TPGS-SMSD can not only speed up the absorption of paclitaxel in rat and can significantly improve the bioavailability.