An immunosensing device based on inhibition of mediator's faradaic process for early diagnosis of prostate cancer using bifunctional nanoplatform reinforced by carbon nanotube

In this study, a simple and lable-free voltammetric immunosensor was successfully developed for the ultrasensitive detection of prostate specific antigen (PSA). To do this, multiwalled carbon nanotube (MWCNT)/L-histidine functionalized reduced graphene oxide (His-rGO) was demonstrated as a bifunctional nanoplatform for covalently attaching thionine redox indicator and anti-PSA antibody (Ab). The MWCNT enhanced electrical conductivity and facilitated the electron transfer between thionine and the glassy carbon electrode. While, the presence of anti-PSA antibody blocked the electron transfer of thionine and decreased redox signals. The principle response of proposed immunosensor was based on the selective interaction of PSA with thionine-NH2-GO-COOH-Ab. This selective interaction led to further decrease of response current of attached electrochemical probe. The liner calibration curve for tumor marker determination was 10 fg mL(-1)-20 ng mL(-1) (R-2 = 0.996). Under optimized conditions, the immunosensor was able to selectively detect PSA with a limit of detection (LOD) of 2.8 fg mL(-1) at 3 sigma. The relative standard deviations (RSDs) for single-electrode repeatability and electrode-to-electrode reproducibility were less than 2.9% and 5.7% (n = 5), respectively. Furthermore, the as-proposed immunosensor showed excellent performance in detection of PSA in the human serum and saliva samples, which implies that the current strategy has a promising feature for the clinical assessment of tumor marker status in patients with prostate cancer. Published by Elsevier B.V.