Chemiresistive CuO sensors for label-free C-reactive protein detection

In this study, we developed fast and highly sensitive, label-free Ca-doped cupric oxide (CuO) based chemiresistive biosensors to detect C-reactive protein (CRP). The Successive Ionic Layer Adsorption and Reaction (SILAR) method was used to deposit pure and Ca-doped CuO thin films on interdigitated gold electrodes. Film surfaces were functionalized with monoclonal anti-C-reactive protein antibody (anti-CRP) by random physisorption method. Sensor fabrication steps were monitored using the linear sweep voltammetry method. Scanning electron microscopy was used to investigate the surface morphology. Energy-dispersive X-ray spectroscopy was used to determine the elemental composition. The structure of the films was investigated by the powder X-ray diffractometry method. Sensor parameters were determined by the change in sensor resistance over time. The sensors showed a good response to CRP with a linear detection range of 0.1–5.0 µg/ml, which was within the clinically significant range. Detection limits of 49.61 and 48.81 ng/ml were estimated using the standard deviation of the y-intercept and the standard deviation of the regression line, respectively. Dynamic response times of all fabricated sensors were found to be less than 30 s •Chemiresistive CuO sensors were fabricated for label-free detection of CRP.•The sensors have shown good responses to CRP in the linear range of 0.1–5.0 µg/ml.•The detection limit and response time were found to be ~ 49 ng/ml and ~ 30 s, respectively.•Ca-doping enhanced the immobilization of anti-CRP to the surface of CuO thin film.