A simple electrochemical immunosensor platform for detection of Apolipoprotein A1 (Apo-A1) as a bladder cancer biomarker in urine

Bladder cancer is one of the tumors associated with the highest mortality rate. It is clinically characterized by high recurrent rates and poor prognosis once tumors invade the lamina propia. Nevertheless, current diagnostic techniques such as cystoscopy and cytology are invasive, time-consuming, and expensive. To address these challenges, we developed an electrochemical enzyme-linked immunosorbent assay (eELISA) platform on indium tin oxide (ITO) glass strips to quantify Apolipoprotein-A1 (Apo-A1) proteins in urine reported as an early bladder cancer biomarker with high sensitivity and specificity. We thoroughly studied the kinetics of ALP enzyme on the surface of ITO electrode so that we determined the minimum incubation time (2 min) and temperature (25 °C) for electrochemical measurement. Combined with chronocoulometry (CC) method under optimized conditions, our developed ITO-based eELISA platform can sensitively detect the existence of Apo-A1 as low as 1 pM in both PBS and urine with the dynamic range of concentrations (1 pM-100 nM) in a small one-drop assay system. Also, the simply prepared detection platform was successfully applied to urine condition. By using the developed platform, urine samples of bladder patients were clearly distinguished from normal controls. Our developed eELISA platform offers a simple and sensitive immunoassay approach for point-of-care (POC) diagnostic system.