Detecting multiple cell-secreted cytokines from the same aptamer-functionalized electrode

Inflammatory cytokines are secreted by immune cells in response to infection or injury. Quantification of multiple cytokines in parallel may help with disease diagnosis by illuminating inflammatory pathways related to disease onset and progression. This paper describes development of an electrochemical aptasensor for simultaneous detection of two important inflammatory cytokines, interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). To enable multiplexing, IFN-γ and TNF-α aptamers were labeled with anthraquinone (AQ) and methylene blue (MB) redox reporters respectively. Random immobilization of two aptamer on gold exhibited redox peaks at −0.37V (AQ) and −0.15V (MB) vs. Ag/AgCl reference. When challenged with either IFN-γ or TNF-α, redox signal of the appropriate reporter changed in concentration dependent manner. To demonstrate one possible application of this sensing approach, electrodes were integrated into microfluidic devices and used to dynamically monitor cytokine release from immune cells. Two cell types, primary human CD4 T-cells and U937 monocytic cells, were used to compare differences in cytokine secretions upon stimulation. These cells were infused into the microfluidic devices and stimulated to commence cytokine production. Release of IFN-γ and TNF-α was monitored concurrently from the same small group of cells over the course of 2 h. The strategy of encoding specific aptamer types with unique redox reporters allows sensitive and specific detection of multiple protein biomarkers from the same electrode.