Aptamer-antibody sandwich assay for cytochrome c employing an MWCNT platform and electrochemical impedance
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- Ocaña, C., Lukic, S. & del Valle, M. Microchim Acta (2015) 182: 2045. doi:10.1007/s00604-015-1540-6
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We report on a sensitive aptamer-antibody interaction-based assay for cytochrome c (Cyt c) using electrochemical impedance. 4-Amino benzoic acid is used for the oriented immobilization of aminated aptamers onto multi-walled carbon nanotubes on the surface of a screen-printed electrode via electrochemical grafting. Impedance was measured in a solution containing the redox system ferro/ferricyanide. The change in interfacial charge transfer resistance (Rct) experienced by the redox marker was recorded to confirm the formation of a complex between aptamer and the target (Cyt c). A biotinylated antibody against cytochrome c was then used in a sandwich type of assay. The addition of streptavidin conjugated to gold nanoparticles and signal enhancement by treatment with silver led to a further increase in Rct. Under optimized conditions, a detection limit as low as 12 pM was obtained. Cross-reactivity against other serum proteins including fibrinogen, BSA and immunoglobulin G demonstrated improved selectivity.