Washing-Free Displacement Immunosensor for Cortisol in Human Serum Containing Numerous Interfering Species

Analytical Chemistry
Ponnusamy NandhakumarHaesik Yang

Abstract

Simple and sensitive competitive immunosensors for small molecules are difficult to obtain, especially in serum containing numerous interfering species (ISs) with different concentrations. Herein, we report a washing-free and sensitive (competitive) displacement immunosensor for cortisol in human serum, based on electron mediation of Os(bpy)2Cl2 between an electrode and a redox label [oxygen-insensitive diaphorase (DI)] (i.e., electrochemical-enzymatic redox cycling). The anticortisol IgG-DI conjugate bound to a cortisol-immobilized electrode is displaced by competitive binding of cortisol in serum and diffuses away from the electrode during incubation; therefore, the concentration of the displaced conjugate near the electrode becomes very low, even without washing. Electrochemically interfering ascorbic acid is converted to a redox-inactive species by ascorbate oxidase during incubation. The remaining bound conjugate mainly contributes to electrochemical currents. Compared with ferrocene methanol, Fe(CN)64-, and Ru(NH3)63+, the electrochemical and redox cycling behaviors of Os(bpy)2Cl2 are influenced significantly less by ISs in serum. Comparative studies reveal that washing-free displacement assay shows better cortisol-induce...Continue Reading

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Citations

Feb 18, 2021·Talanta·Sofia M SafarianVladimir P Drachev
Oct 28, 2019·ACS Sensors·Ponnusamy NandhakumarHaesik Yang

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