An electrochemical capacitance immunosensor based on an interdigitated wave‐shaped micro electrode array (IDWμE) for direct and label‐free detection of C‐reactive protein (CRP) was reported. A self‐assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X‐ray spectroscopy (EDX). The nature of gold‐sulfur interactions on SAM‐treated electrode array was probed by X‐ray photoelectron spectroscopy (XPS). The covalent linking of anti‐CRP‐antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate‐buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti‐ CRP‐antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01–10,000 ng mL−1. The electrode showed detection limits of 0.025 ng mL−1 and 0.23 ng mL−1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation, (RSD) 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.
Bibliographical noteFunding Information:
This research was funded by the National Research Foundation of Korea (Grant No. NRF 2017R1D1A1A09000712, 2018R1C1B6009385, 2018M3A9F1023690, and 2019R1A2C1088680).
© 2019 by the authors. Licensee MDPI, Basel, Switzerland.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Information Systems
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering