Label-free electrochemical aptasensor for cytochrome c detection using pillar[5]arene bearing neutral red

• Cytochrome c was determined with voltammetric aptasensor.
• Neutral red was covalently attached to polycarboxylated pillar[5]arene as redox label.
• Aptamer – cytochrome c binding decreased the label peak current.
• The minimal detection limit of 0.02 nM was achieved with 20 min incubation.

Novel electrochemical aptasensor toward cytochrome c (Cyt c) has been developed on the base of glassy carbon electrode (GCE) modified with electropolymerized neutral red (Poly-NR) and decacarboxylated pillar[5]arene (P[5]A-COOH) bearing terminal neutral red (NR) and aminated aptamer specific to Cyt c. Addition of Cyt c resulted in decrease of the cathodic peak current of NR on cyclic voltammogram due to suppression of the electron exchange between reduced and oxidized NR forms in the surface layer. The implementation of Cyt c in the surface layer was confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Depending on the content of the surface layer and assembling protocol, the limits of detection (LODs) varied from 0.02 to 1.0 nM and linear range of concentrations was within three orders of magnitude. Interfering influence of some proteins and polyethylene glycol was characterized. The aptasensors developed can find application in detection of Cyt c as apoptosis agent in blood serum. This has been partially validated in model blood serum mimicking the ionic composition of the plasma.

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