| Chemotherapy is an indispensable choice for most cancers due to its high efficiency.However,owing to its severe side effects and high costs,cancer treatment remains a problem that plagues people.With the development of nanoscience and material chemistry,multifunctional nano drug delivery systems have emerged.Through the use of molecular design and self-assembly techniques,the development of smart nano-drug delivery systems with extracellular stability and selective intracellular release of drugs can provide an alternative way to reduce to reduce the toxic side effects of chemotherapy drugs and improve tumor treatment efficiency.In this work,based on the concentration of GSH in tumour cells is significantly higher than those in normal cells and in blood plasma,novel pH-sensitive and GSH-responsive polymer prodrug micelles for leukemia therapy were constructed by conjugating hydrophobic anti-leukemia drug 6-Thioguanine(6-TG)to hydrophilic dialdehyde sodium alginate(DSA)via acid-labile Schiff base linkage followed by the ultrasound-assisted oxidation of thiol groups to disulfide cross-links,and their related properties were studied.The main research work and results are as follows:I.Preparation and characterization of amphiphilic 6-TG-DSA prodrug.DSA was prepared by oxidation of SA with sodium periodate,and then formed an amphiphilic 6-TG-DSA prodrug by Schiff-base conjugation with hydrophobic drug,6-TG.Their structures were characterized by IR and ~1H-NMR.The maximum drug content in the prodrug determined elemental analysis was 17.0%.II.Preparation and characterization of GSH/pH dual-responsive 6-TG-DSA prodrug micelles(1)6-TG-DSA prodrug micelles were prepared by ultrasonic dispersion method.Transmission electron microscopy showed that the nanoparticles were core-shell structures.The dynamic light scattering(DLS)study showed that the resulting micelles had high storage stability and dilution stability in pH 7.4 buffer solution.(2)TEM and DLS observations showed that the micelles had GSH and pH responsiveness.A negligible change in particle size was observed for the micelles in pH 7.4 buffer solutions with 0 and 0.01 mM GSH;however,when GSH was added to a pH 5.0 buffer solution to 10 mM or 20 mM,the micellar particle size increased significantly.In the case of 20 mM GSH,the micelles completely disintegrated after180 hours of incubation,indicating the double responsiveness of the micelles.III.In vitro drug release behavior of GSH/pH dual 6-TG-DSA prodrug micelles(1)In pH 7.4 and 0.01 mM GSH(mimic human blood)buffer,only a very small amount(less than 2%)of 6-TG was released from the polymer prodrug micelles within 228 hours;while at pH 5.0 with 20 mM GSH(simulated tumor intracellular environment)and 10 mM GSH(normal intracellular environment),6-TG release rate for the former were significantly higher than that for the latter within 228 hours.(2)The drug release can be regulated by regulation of drug content.The polymer micelles with higher 6-TG content exhibited slower drug release rates at the same time because of the higher degree of disulfide cross-linking.IV.The cytotoxic,cellular uptake evaluation of GSH/pH dual-responsive6-TG-DSA prodrug micelles.(1)In comparison with free 6-TG,the 6-TG-DSA prodrug micelles exhibited slightly higher inhibition ratio on HL-60 cancer cells and an obviously reduced cytotoxicity against normal L-O2 cells,indicating that the micelles could significantly inhibited the cytotoxicity of 6-TG and protected the L-O2 cells.(2)The 6-TG-DSA prodrug micelles loaded with fluorescent dye Nile Red(NR)could be efficiently taken up by HL-60 tumor cells and released the encapsulated NR in the cytosol,but no NR release was observed within 24 hours in normal cells,which indicated that the polymer prodrug micelles could selectively release the bond drug6-TG in respond to GSH and pH-stimulation in cancer cells. |
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