Electrochemical detection of c-reactive protein based on anthraquinone-labeled antibody using a screen-printed graphene electrode.

In this present work, a novel electrochemical immunosensor employing a screen-printed graphene electrode (SPGE) for a simple and highly sensitive determination of C-reactive protein (CRP) in a sandwich-type format was proposed. The sensor comprised of two CRP-specific antibodies: an unlabeled capture primary antibody (Anti-1°Ab) and an electrochemically detectable anthraquinone-labeled signaling secondary (AQ-2°Ab) antibody. The Anti-1°Ab was first covalently anchored onto an L-cysteine/gold-modified disposable SPGE (L-Cys/Au/SPGE) to create the anti-CRP surface. After binding of the CRP and the AQ-2°Ab, the electrochemical signal response was measured using differential pulse voltammetry (DPV). In the presence of CRP, the sensor exhibited a significant increase in the AQ current at AQ-2°Ab compared to the negative control. The CRP concentration was detected in the range of 0.01-150 µg/mL, and the limit of detection (LOD) (S/N = 3) and limit of quantitation (LOQ) (10 SD/Slope) were 1.5 ng/mL and 10 ng/mL, respectively. This sensor exhibited very high sensitivity in determining CRP and was successfully applied to detect CRP in certified human serum with satisfactory results. The developed sensor is suitable as an alternative method for determination of CRP and the same principle may be further applied to determine other clinically important target molecules.