Washing-free redox cycling immunoassay technique was developed by Dutta et al. [22, 23] to minimize the washing steps of the immunoassay that allows fast, sensitive, and single-step detection of biomarkers in serum with low interference. Electrochemicalenzymatic (EN) redox cycling (Figure1) was used to amplify the signal-to-background ratios. Biotinylated capture probe (IgG) was immobilized on the ITO electrode surface. A sample solution (contains unknown concentration of biomarker) was

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... with enzyme-conjugated IgG and enzyme-substrate, which was spiked with serum with different concentrations of target antigen. The solution mixture was then injected into the electrochemical cell and incubated for 10 min. The interference effect was minimized by applying a lower applied potential and eliminating the ascorbic acid effect. A calibration plot was obtained with increasing the target concentration. The signal was increased with the target concentration because surface concentration of bound enzyme-