Antitumor Efficacy Of PH/Redox Dual-responsive Nanogel Drug Delivery System

Cancer is one of the most serious diseases which are dangerous to human health. Although chemotherapy is one of the most effective means to treat cancer, it still has many shortcomings, such as the toxic side effects in normal cells and the drug resistance in tumor cells, etc. Combination chemotherapy with nanotechnology have shown significant promise in cancer treatment. As drug delivery systems, nanogels have a wide range of applications in the biomedical field. In this paper, we designed pH/redox dual sensitive nanogels to explore its application in antineoplastic delivery. The results are as follows:(1) The preparation and characterization of pH/redox nanogel drug system: Using N-isopropyl acrylamide(NIPAAm), acrylic acid(AAc) and N,N’-bis(acryloyl) cystamine(BAC) as raw materials, pH/redox dual-responsive nanogels were synthesized by surfactant-free emulsion polymerization method. Then doxorubicin(DOX) as an anticancer drug model was entrapped into the nanogels by organic solvent evaporation. The characterizations of the nanogel drug system, such as particle sizes, zeta potentials, morphology, environmental response was further performed. The results showed that the constructed nanogels were uniform spheres with 250 nm size and-25 mV potential and showed good pH/redox responsiveness. The loading of DOX did not affect the characterization of the nanogels.(2) The interactions between pH/redox nanogel drug system and HepG2 cells: The nanogels were firstly labeled with fluorescence through chemical conjugation method. The endocytic pathway and intracellular distribution of the nanogels were determined by laser scanning confocal microscopy and flow cytometry. The specific inbitors og thiol groups were used to explore the degradation site of disulfide bond in nanogel drug system at the celluar level. The cytotoxicity of DOX-loaded nanogels to HepG2 cells was further determined by MTT assay. The results indicated that the macropinocytosis, clathrin- and caveolin-mediated endocytic pathways were responsible for the cellular uptake of the nanogels. During internalizations, DOX-loaded nanogels firstly entered the early and late endosomes, and then fused into lysosomes. DOX partially released from nanogels in the lysosomes under acidic enviroment and further released in response to glutathione(GSH) in the cytoplasm. Eventually, DOX entered into the nucleus, however the nanogles are still in the cytoplasm. The nanogels were nontoxic and DOX-loaded nanogels showed strong cytotoxicity to HepG2 cells.(3) The enhanced permeability and retention effect of the DOX-loaded nanogels: Subcutaneous carcinoma model was constructed with BALB/c(SPF grade) male mice. The biodistribution of DOX-loaded nanogels was determined using small animals living imaging techniques. In vivo tumor penetration of intravenously injected DOX-loaded nanogels in tumor-bearing mice was further explored. The results demonstrated that the nanogel drug system had great tumor targeting and retention in the H22 liver cancer model. DOX could be effectively released from the vessel, then entered into the deep seated tumor.In summary, this study constructed pH/redox dual responsive nanogel as carriers of anticancer drug to targetedly deliver DOX to tumors by EPR effects and reduce the side effects of DOX. These results could provide experimental and theoretical basis for nanogel carriers as anticancer drugs.