Preparation And Cell Proliferation Inhibition Activity Of Cantharidin-loaded Biodegradable Amphiphil Copotymers

Cantharidin（CA）has been used in traditional Chinese medicine for the treatment of cancer.However,it has irritant effects on the urinary and digestive organs.At the same time,the low solubility of CA has restricted the application and development of cantharidin.In this paper,MPEG-b-PCL,an amphiphilic materials,was used to encapsulate anticancer drug CA to improve the solubility,to reduce the toxicity and to enhance the therapeutic efficiency.In aqueous solution,MPEG-b-PCL is able to self-assembly to micelles.PCL,the hydrophobic segment,constituted the hydrophobic core to store drugs;MPEG,the hydrophilic chain segment,constituted the hydrophilic film to maintain the structure of particles in aqueous environment.The contents and results of this experiment are summarized as below:In the first place,hydrophilic polymer polyethylene glycol（MPEG）and caprolactone（CL）were used as raw materials,under the catalysis of diethyzinc,three kinds of amphiphilic block copolymers MPEG_5K-b-PCL_6K,MPEG_5K-b-PCL_9kk and MPEG_5K-b-PCL_12K2K obtained.Emulsifier volatilization,volatilization dialysis and film hydration method were adopted to prepare CA encapsulated nanoparticles.Secondly,the size and distribution of blank micelles and drug-loaded micelles were measured by dynamic light scattering（DLS）.We found that micelles with drug had a bigger size than that without drug under the same preparation conditions.Micelles shape and size were observed by Transmission Electron Microscope（TEM）.There were no significant difference between drug-loaded micelles and drug-free micelles except the particle size.The most common method to determine critical micelle concentration（CMC）of polymer is using pyrene fluorescence probe.The experimental data show that the CMC of MPEG_5K-b-PCL_9KK is 1.58×10^-6.CMC value in a 10^-66 range was very important for keeping the stability of micelles in vitro and keeping their intact structure upon dilution with body liquid in vivo.IR was utilized to determine the structures of blank micelles,CA-loaded micelles and mixture of CA and MPEG-b-PCL.According to IR,the conclusions could be clearly got that the free drug out of the micelles had been removed completely.This makes the experimental results more convincing.High performance liquid chromatography（HPLC）determination of the concentration of cantharidin,and calculate the drug loading and encapsulation efficiency of the drug loaded micelles.Finally,In vitro release and cell proliferation inhibition of the drug loaded micelles prepared by thin film hydration method.A certain micelles solution in a dialysis bag was put into a tube containing fixed amount of phosphate buffer solution（pH5.0,7.0,7.4）,the assay of CA was also done by HPLC.Medium cantharidin showed slow sustained release effect in the different pH release liquid.The cumulative amount of release parabolic slow growth with time and decreases with the increase of pH from pH=5.0 to pH=7.4.Hela cell line,HepG2 cell line and A2780 cell line were chosen as target cells to evaluate the cell proliferation inhibitory activity of CA and drug-loaded micelles.Cancer cells were more sensitive to CA-loaded micelles than CA itself.