Chain Length Effect On Penetration Behavior Of MPEG-PCL Micelles Using Multicellular Tumor Spheroids And Animal Models

Amphiphilic block copolymers can self-assemble into nano-sized aggregates in the presence of a selective solvent for one of the blocks and aggregates have the structures of hydrophobic core and hydrophilic shell.So it has a wide application in the drug delivery field.In this article,four amphiphilic diblock copolymers mPEG5000-PCL1000,mPEG5000-PCL3000,mPEG5000-PCL5000,mPEG5000-PCL8000 with methoxy poly(ethylene glycol)(mPEG)and different chain lengths of polycaprolactone(PCL)was fabricated and self-assembled into micelles to load the anticancer drug doxorubicin(DOX).The effect of block chain length on drug delivery was investigated.mPEG–PCL diblock copolymers were synthesized by ring-opening polymerization of ?-CL with mPEG homopolymer as macroinitiator and Sn(Oct)2 as the catalyst.and the 1H nuclear magnetic resonance(1H NMR),Gel Permeation Chromatography(GPC)were characterized to confirm the successful synthesis of the copolymers.The size and morphology of mPEG-PCL micelles were tested by DLS and TEM.In vitro drug release profiles exhibited that in a environment similar with that of tumor cells.The cytotoxicity of blank micelles was tested by CCK8 assay against HUVEC cells and Hep G2 cells.The cell viability was measured by CCK8 assay.The cellular uptake and distribution of drug loaded micelles in cells were detected using by confocal laser scanning microscopy(CLSM).To establish implanted liver tumor in nude mice with immediate injection method and to observe the process of tumor penetration with IVIS Spectrum.Four mPEG–PCL block copolymers with different chain lengths of PCL blocks were synthesized.The hydrodynamic diameters of these four kinds of copolymer micelles were less than 100 nm and had good thermal stability by using dynamic light scattering(DLS)method.TEM image showed the micelles were in spherical shape and equally distributed.The release profile indicate that the sustained release of DOX was achieved and the drug release rate could be controlled by modulating the chain length of mPEG and PCL blocks.In vitro cytotoxicity verify the micelles was non-toxic to cells and DOX loaded micelles shows efficient anticancer activity.The penetration behavior was might assist the diffusion of DOX,which was confirmed by confocal microscopy images.The Hep G2 cells treated with mPEG-PCL showed that strong red fluorescence microscopy.This result illustrate that DOX loaded micelles were internalized via an endocytosis process,the DOX could escape from endosomes to fulfill anticancer function.Penetration behavior of tumor spheroids was found to depend on nanoparticle size when the concentration of drug loaded micelles and incubation time were the same.Tumor spheroids treated with mPEG5000-PCL5000 showed the strongest fluorescence within all the four drug loaded micelles.The formation ratio of tumor with immediate injection method was high.The pathologic characteristics of liver tumor were similar to those of the human's.IVIS Spectrum showed mPEG5000-PCL5000 has better penetration in tumor.Results indicate that mPEG-PCL micelles were found to substantially provides an efficient antitumor carrier and reduce drawback of free DOX.