Label-free electrochemical assessment of human serum and cancer cells to determine the folate receptor cancer biomarker.

The folate receptor (FR) is a well-known biomarker that is overexpressed in many cancer cells, making it a valuable target for cancer diagnostics and therapeutic strategies. However, identifying cancer biomarkers remains a challenge due to factors such as lengthy procedures, high costs, and low sensitivity. This study presents the development of a novel, cost-effective biosensor designed for the detection of FR. To overcome the limitations of traditional immunological methods, which rely on antigen-antibody interactions, we utilized a charge-based affinity approach. Folic acid (FA) was conjugated with poly (diallyl dimethylammonium chloride) (PDDA) using an EDC-NHS linker on the surface of multi-walled carbon nanotubes. The biosensor enabled electrochemical detection of FR through differential pulse voltammetry (DPV), achieving an impressive detection limit of 1.6 pg/mL and a dynamic range of 1-10,000 ng/mL. Additionally, the biosensor exhibited excellent stability (30 days), high selectivity, and repeatability (RSD = 3.14 %, n = 5). This work presents a promising strategy for developing ligand-receptor-based biosensors. It paves the way for future applications in cancer diagnostics and biosystem interfaces, offering high performance and practical advantages.