Design,Synthesis And Anti-Tumor Activity Of Vitamin E Succinate Phospholipid Prodrugs

Vitamin E succinate(RRR-a-tocopheryl succinate,VES),one of the most effective anticancer compounds of the vitamin E family,can selectively inhibit the growth of various cancer cell.However,the clinical application of VES has been greatly limited,owing to its poor aqueous solubility and bioavailability.To improve aqueous solubility and develop new nanodelivery system,we prepared a unique liposomal drug delivery system based on newly designed VES amphiphilic prodrugs,which were synthesized by conjugating VES with the hydrophilic glycerophosphorylcholine(GPC)and lysoph-osphatidylcholine(LPC).The synthetic route,assembly behavior,physical&chemical properties and in vitro antitumor activity of the conjugate were investigated in detal.The main contents and results are as follows:(1)Di-VES-GPC conjugate was synthesized by conjugating VES with glycerophosphorylcholine via an ester bond linker.The chemical structure of the conjugate was characterized by ESI-MS,1H-NMR,13C-NMR and HPLC.The self-assembly behaviors of the congjugate were investigated by a fluorescence probe method,dynamic light scattering(DLS),transmission electron microscopy(TEM)and cryogenic transmission electron microscope(Cryo-TEM).The results indicated that Di-VES-GPC conjugate could self-assemble into liposomes with an average diameter of 183 nm and a zeta potential of-18.6 mV.Cryo-TEM data confirmed the formation of multilamellar liposomes with the bilayer thickness about 5 nm by the assembly of the conjugate without any excipient.Furthermore,the in vitro release behavior of Di-VES-GPC liposomes was evaluated in different media.It was found that the liposomes could release free VES in the weakly acidic environment but exhibited good stability under simulated biological condition.Celluar uptake of Di-VES-GPC liposomes was performed using MCF-7 cells by confocal laser scanning microscopy(CLSM)and ESI-MS.The result demonstrated that liposomes could be internalized effectively and release parent drug VES.In vitro antitumor activities of the Di-VES-GPC liposomes were evaluated by MTT assay and flow cytometry.It was revealed that the liposomes showed lower cytotoxicities to free VES.(2)Stimulus-responsive VES-SS-LPC conjugate was synthesized by conjugating VES with lysoph-osphatidylcholine via a disulfide bond linker,resulting in rapid release of VES parent drug intracellular reducing milieu.The chemical structure of the conjugate was characterized by ESI-MS,1H-NMR,13C-NMR and HPLC.The self-assembly behaviors of the congjugate were investigated by electric conductivity method,dynamic light scattering(DLS)and transmission electron microscopy(TEM).The results indicated that VES-SS-LPC could self-assemble into liposomes with an average diameter of 175 nm and a zeta potential of-21.6 mV.Furthermore,the in vitro release behavior of VES-SS-LPC liposomes was evaluated in different media.It was found that the liposomes could rapidly release free VES in the presence of 10 mM GSH mimicking the intracellular environment but exhibited good stability under simulated biological condition.This might be due to cleavage of the disulfide bond in the VES-SS-LPC conjugate under the reductive environment,causing the disintegration of the liposomes.The data revelaed that VES could be rapidly released from VES-SS-LPC liposomes in the intracellular environment.Celluar uptake of VES-SS-LPC liposomes was performed using MCF-7 cells by confocal laser scanning microscopy(CLSM)and ESI-MS.The result demonstrated that liposomes could be internalized effectively and release parent drug VES.In vitro antitumor activities of the VES-SS-LPC liposomes were evaluated by MTT assay.It was revealed that the liposomes presented equivalent cytotoxicities to free VES.In conclusion,two kinds of amphiphilic prodrugs were synthesized by conjugating hydrophobic VES with the hydrophilic glycerophosphorylcholine(GPC)via an ester bond linker and lysoph-osphatidylcholine(LPC)via a disulfide bond linker.They had the ability of assembling into stable liposomes.Furthermore,VES-SS-LPC liposomes could rapidly release free VES and presented effective ancancer activity.Therefore,it could be an effective VES drug delivery system in clinical cancerchemotherapy.