Electrochemical immunosensor utilizing a multifunctional 3D nanocomposite coating with antifouling capability for urinary bladder cancer diagnosis

Currently available point-of-care tests for Bladder Cancer (BC) are qualitative and prone to high false positives, thus preventing them from replacing clinical cystoscopy as reliable stand-alone diagnostics. In this study, we have targeted this unmet need by developing a label-free electrochemical impedimetric immunosensor for detection of APO-A1, a major high-density lipoprotein that is overexpressed in the urine of early-stage bladder cancer patients. The immunosensor utilizes a novel multifunctional 3D nanocomposite coating consisting of a porous bovine serum albumin (BSA) matrix embedded with a network of highly conductive and biocompatible gold coated silver nanowires (Au@AgNWs). The main components of this nanocomposite coating and their specific functions include: (i) A 3D porous BSA matrix to enable oriented antibody conjugation and prevent non-specific protein adsorption while allowing diffusion of analyte with minimal hindrance as compared to tradi-tional antifouling coatings (ii) Embedded Au@AgNWs that enhance biocompatibility and improve charge transfer to the underlying electrode. The nanocomposite coating demonstrated minimal decrease in electro-chemical performance even after 1-month of incubation in 1% BSA, human serum and human urine. Further-more, the low-cost and disposable screen-printed electrochemical immunosensor exhibited excellent feasibility for sensitive and specific APO-A1 detection in the clinically relevant sensing range of 100 pg/mL to 250 ng/mL with high reproducibility (n = 5, RSD=2.2%) and an impressive LOD of 22 pg/mL. These results highlight the potential of the proposed immunosensor to enable reliable early diagnosis of bladder cancer at the point-of-care and serve as a viable alternative to cystoscopy.