Studies On Novel Liposomal Drug Delivery Systems Of All-trans-retinoic Acid

All-trans-retinoic acid(ATRA)is the most biologically active metabolite of retinol.It can be used to treat acute promyelocytic leukemia(APL)and many solid tumors?However,ATRA has several drawbacks,such as,poor aqueous solubility,severe side effects and drug resistance.In addition,short half-life time of ATRA in vivo is also a critical problem for clinical application in cancer therapy.In this report,we developed unique drug delivery systems with newly designed two nano preparations.The synthetic route,assembly behavior,physical&chemical properties and in vitro antitumor activity of the conjugate were investigated in detal.The main content and results of the thesis are as follows:(1)Di-ATRA-PC amphiphilic prodrug was synthesized by a facile esterification.The liposomes were prepared by thin-lipid film method without any additive.The loading efficiency of ATRA increased up to 73 wt.%after a simple calculation.The assembled liposomes were characterized by dynamic light scanning(DLS),transmission electron microscope(TEM)and cryogenic transmission electron microscope(cryo-TEM).The results indicate that the liposomes have an average diameter 71.3 nm and negatively charged surface with typical lipid bilayer structure.The Di-ATRA-PC liposomes had good stability in neutral environment,but effectively released free ATRA in a weakly acidic condition.Cellular uptake analysis demonstrated that the liposomes could be internalized by MCF-7 cells and release parent drug.Furthermore,MTT and flow apoptosis studies showed that the liposomes had comparable cytotoxicities to free ATRA against MCF-7 and HL-60 cells.More importantly,in vivo pharmacokinetic assay indicated that Di-ATRA-PC liposomes had longer blood retention time than ATRA in BALB/c mice.(2)The anti-tumor drug ATRA was encapsulated by Di-ART-PC liposomes prepared by the laboratory itself to form a new drug-loaded nanoparticle NPATRA/ART by reverse evaporation method.The loading rate of the nanoparticles was 93.48%and the drug loading was 3.12%,which was higher than that of the normal NPATRA.The drug-loaded nanoparticles showed a narrow particle size distribution(151.7 nm)and a surface charge of-10.3 mV.In PBS(pH 7.4),drug-loaded nanoparticles were able to slowly release the drug ATRA.A series of pharmacological studies were carried out on human promyelocytic leukemia cells(HL-60).Studies have shown that drug-loaded nanoparticles show better cytotoxicity than other drug groups after 72 h of tumor cells.At the same time,administration of this drug delivery system can improve the NBT positive cell rate and CD11b positive cell rate,so that it could promote the differentiation of HL-60 cells more effectively.After drug administration of HL-60 cells for 72 h,drug-loaded nanoparticles could cause more cancer cells to apoptosis.In addition,drug-loaded nanoparticles have a longer blood retention time in mice compared to ATRA,resulting in more effective tumor growth inhibition.In summary,we constructed ATRA as a hydrophobic drug model to construct two novel all-trans retinoic acid nano-pharmaceutical preparations.The nano-preparation has a good anti-tumor effect,which has a potential application value and the significance of in-depth study.