Graphene quantum dots(GQDs) based aptasensor toward intracellular cytokine monitoring in live cells
【摘要】：Cytokines secreted from cells play critical roles in tissue repair, cancer development and progression. Unfortunately, probing what cells "see", and what they secrete as they respond in real time to the surrounding signals is still a major challenge. The ultra-low concentration of cytokine (in the pM range), and extremely dynamic, transient cytokine secretion process make cytokine quantification even difficult. By integrating with nanotechnology, biosensors as the analytical devices for the detection of an analyte, that combines a biological component with a physicochemical detector, have demonstrated huge potential for cytokine sensing. Aptamer based structure-switching biosensing methodology has great potential for real-time sensing of small molecules. We developed an aptasensor being able to dynamically and specifically capture ultra-small amount of cytokines. Cytokine aptamer modified graphene quantum dots (Ap-GQDs)and epitope modified GQDs (Ep-GQDs) were prepared, respectively. The mixture of Ap-GQDs and Ep-GQDs is fluorescence "OFF" due to the self-quenching of GQDs, which can be used as the probe for sensing cytokine intracellularly. The presence of cytokines in cells could displace away epitope and bind with aptamer, resulting in the dissociation of Ap-GQDs and Ep-GQDs bioconjugates and turning "ON" fluorescence. Ap-GQDs and Ep-GQDs bioconjugates were characterised by TEM, electrophoresis, fluorescence and cytotoxicity assay. The aptasensor was used to monitor intercellular cytokine IFN-γsecretion with high sensitivity (0.1 pg/mL). The designed sensing mechanism was very simple and universal, and it could be used for detection of a broad spectrum of cell-secreted molecules in a dynamic manner. It was also essential for understanding cell biology and pathway of cytokine secretion in live cells.