Vincristine Loaded And SGC8 Modified Liposome Nanoparticles As A Potential Targeted Drug Delivery System For Treating Acute Lymphob Lastic Leukemia

Targeted drug delivery system(TDDS)can selectively distribute the drug to the target tissue,the target organ,the target cells.This system can not only reduce the dose of drugs,but also reduce adverse drug reactions,increase the concentration and retention time of drug in the target site,enhance the bioavailability of drugs.We developed a targeted liposomal drug delivery system(sgc8/VCR-Lipo).This technology can specifically deliver VCR to leukemia cells via sgc8 aptamer and maintain a prolonged effective drug concentration by controlled release.This study was to reduce systematic adverse effects of vincristine sulfate(VCR)and improve its therapeutic effects against leukemia.Background: Selective targeting of cancer cells is a critical step in cancer diagnosis and therapy.Objective: Current study is proposed to construct leukemic cell targeted liposomal drug delivery system(sgc8/VCR-Lipo),aiming to deliver vincristine sulfate(VCR)to the tumor cells selectively by using sgc8 aptamer.Meanwhile,liposome strategy will be applied for slowly releasing VCR to maintain an effective concentration longer,resulting in reduced systematic reverse effects and improved therapeutic effect.Method:The Liposome was prepared by the thin-film dispersion method,VCR was encapsulated into liposomes,forming VCR-Lipo,by a transmembrane pH gradient-dependent procedure.VCR-Lipo was further conjugated with sgc8,a specific nucleic acid aptamer bound to the CCRF-CEM cell line(acute lymphoblastic leukemia),to establish a novel target drug delivery system(sgc8/VCR-Lipo).The aptamer sgc8 was conjugated to the phospholipid double layer of the surface of liposome,the thiol(S-S)-modified 5’ end of sgc8 can react and conjugate with the DSPE-PEG2000-MAL on the liposome surface.The particle size,the Zeta potential and the dispersion of the prepared liposome particles were measured by dynamic light scattering(Dynamic Light Scattering Instrument,DLS).The size and morphology of nanoparticles were observed using a transmission microscope.In vitro drug release rates between VCR-Lipo and sgc8/VCR-Lipo were compared at different environmental conditions(pH),at pH 7.4 and at pH 5.0.The binding ability of sgc8/VCR-Lipo to CEM cells was examined by a fluorescence assay and the flow cytometric analysis.The effect of sgc8/VCR-Lipo on cell viability in vitro was determined by MTT assay.A mouse leukemia xenograft model was established by subcutaneously injecting CEM cells into left back of BALB/c nude mice.Di R-labeled Lipo and Di R-labeled sgc8/VCR-Lipo were intravenously injected,respectively.Tissue distribution of sgc8/VCR-Lipo in different organs at different time points was examined using a Bruker imaging system with excitation wavelength of 720 nm and emission wavelength of 790 nm.In vivo anti-tumor activity of sgc8/VCR-Lipo was investigated in a mouse leukemia xenograft model.A mouse leukemia xenograft model was established by subcutaneously injecting CEM cells into left back of BALB/c nude mice.Mice were intravenously injected via tail vein with different drug formulations,Tumor size,mice body weight,tumor weight and survival time were also recorded.For monitoring the side effects of liposomal formulations,changes of mouse body weight(MBW)were observed.Result:The characterization of sgc8/VCR-Lipo was evaluated by different methods.The TEM images showed that sgc8 /VCR-Lipo had good dispensability,uniform size,round or oval appearance and a bilayer membrane with about 110 nm diameter,and negatively charged surface.The sgc8/VCR-Lipo drug delivery system was characterized by 90.63% drug entrapment rate.Drug release rates between VCR-Lipo and sgc8/VCR-Lipo were compared at different environmental conditions.At pH 7.4,drug release from VCR-Lipo and sgc8/VCR-Lipo became slow,not exceeding 50 % during the period of 96 hours,indicating that both of them likely behaved as sustained release which might be due to the addition of PEG2000 during liposome preparation.The fluorescence assay and the flow cytometric analysis demonstrated that the sgc8/VCR-Lipo can specifically bind to CEM cell membrane surface protein by sgc8 aptamer.The result of the MTT assay suggested that sgc8/VCR-Lipo can specifically inhibit proliferation of CEM cells by delivering VCR to the target cells.In tumor-bearing nude mice,sgc8/VCR-Lipo accumulated selectively at tumor site and led to VCR release within tumor tissue and a significant attenuation of tumor growth.Subsequently,survival time of tumor-bearing mice was prolonged.Conclusion: In this study,sgc8/VCR-Lipo was identified as a potential targeted drug delivery system,which may be useful for reducing side effects induced by non-specific drug release and improve anti-tumor efficacy of VCR.Our findings provide reliable and scientific evidence for developing novel aptamer-based targeted drug delivery systems for leukemia treatment.