Functionalized MnO₂ Nanosheets For Gene Transfection And Glutathione Detection

With the development of nanotechnology,a series of nanomaterials with special physicochemical properties have been widely used in biomedical fields.Among them,MnO₂ nanosheets have attracted tremendous attention in the fields of cancer therapy and imaging owing to the appealing advantages,such as good biocompatibility,low toxicity,strong fluorescence quenching ability and degradable.Efficient gene delivery plays an important role in tumor gene therapy.However,MnO₂ can only effectively deliver single-stranded DNA into cells,and it has no strong interaction with double-stranded DNA.Moreover,it has not yet been reported for transfection of plasmid DNA.Therefore,it is necessary to develop a low toxicity and effective nanocarrier based on MnO₂ nanosheets for gene transfection.In addition,MnO₂nanosheets have great advantages in the aspect of developing simple and sensitive fluorescent probes due to its good oxidation performance and fluorescence quenching ability.Thus,in this thesis,different functionalized MnO₂ nanosheets are designed and synthesized for gene transfection and glutathione detection,respectively.The main research contents are as follows:1.Polyethylenimine functionalized MnO₂ nanosheets as a safe and efficient vehicle for gene transfectionIn order to develop a safe and effective gene delivery vector,it is a feasible strategy to integrate cationic polymers and nanomaterial.In this work,functionalized MnO₂ nanosheets were successfully synthesized for gene transfection.Polyethylenimine?PEI,25 kDa?,one of the cationic polymers,was modified on MnO₂nanosheets by electrostatic interactions to synthesize MnO₂-PEI with positive charge,which is capable of interacting with plasmid DNA?gel electrophoresis assay?.In addition,MTT assay exhibited that MnO₂-PEI is significantly less cytotoxic than PEI.Importantly,the vehicle achieved considerably higher transfection efficiency of the enhanced green fluorescence protein?EGFP?gene in HeLa cells than that of the PEI.Furthermore,p53 gene delivery of MnO₂-PEI for inhibition effect and the expression of p53 protein against HeLa cells also proved the efficient transfection ability.The results suggest that functionalized MnO₂ nanosheets have the potential as a promising safe and efficient non-viral vehicle for gene delivery and therapy.2.Molybdenum disulfide quantum dots functionalized MnO₂ nanosheets for glutathione detectionGlutathione?GSH?serves various cellular functions and plays a vital role in biological systems.In this section,a convenient fluorescence nanosensor was constructed for GSH detection using molybdenum disulfide quantum dots?MoS₂ QDs?as fluorescence units and MnO₂ nanosheets as fluorescence nanoquencher as well as GSH recognizer.In the nanosensor,the fluorescence of MoS₂ QDs could be quenched by MnO₂ nanosheets through fluorescence resonance energy transfer?FRET?.However,the presence of GSH would trigger the decomposition of MnO₂ nanosheets,resulting in the release of MoS₂ QDs and the recovery of fluorescence.The nanosensor displayed a good linear relationship to GSH in the range of 10-600?M and with a 1.64?M detection limit.Furthermore,MnO₂-MoS₂ QDs with good membrane permeability and excellent biocompatibility was successfully applied for fluorescence imaging of intracellular GSH level in living cells,and distinguishing the normal cells and cancer cells,indicating its great potential to be employed in disease diagnosis.