A label-free electrochemical immunosensor on gold-printed electrode for the electrochemical detection of C-reactive protein from blood samples

The fabrication of a simple, label-free, electrochemical immunosensor for C-reactive protein (CRP) detection is presented using a custom-designed printed circuit board (PCB) gold electrode. To enhance the sensitivity of the sensing platform, the surface of the gold working electrode was modified with multi-walled carbon nanotubes (MWCNTs), leveraging its exceptional conductivity and biocompatibility. The label-free immunosensor operates on immunological principles, with anti-CRP antibodies covalently immobilized on the modified electrode to capture and quantify CRP levels, using differential pulse voltammetry (DPV). The immunosensor demonstrated high specificity to CRP, exhibiting a linear detection range of 1.25 to 80 μg/mL of CRP in 1 × PBS, and achieving a detection limit (LOD) of 0.745 µg/mL within 30 min. Notably, the immunosensor successfully detected CRP in human ethylenediaminetetraacetic acid (EDTA)-anticoagulated whole blood with a detection limit of 0.177 µg/mL, which is within the clinical range for sepsis (5 µg/mL). Furthermore, this immunosensor was able to detect CRP using only 2 µL of EDTA-anticoagulated whole blood samples. These findings highlight the potential of the CRP immunosensor platform for point-of-care (POC) testing in clinical settings, owing to its simple fabrication, ease of operation, low cost, and robust performance.