Flower-like Silver Bismuth Sulfide/Carbon Nanosphere Nanocomposite for Sensitive Electrochemical Tumor Marker Sensing

A portable electrochemical aptasensor was fabricated using a nanocomposite (Silver Bismuth Sulfide/Carbon Nanosphere, AgBiS₂/CNS) for the targeted detection of the cancer biomarker carcinoembryonic antigen (CEA). The prepared nanocomposite provides a higher specific surface area, electrical conductivity, and tunable functionality, which enable more effective aptamer immobilization compared to conventional electrode materials. The aptamer, known for its chemical stability and robust surface binding, was immobilized on the surface-treated screen-printed carbon electrode (SPCE), thereby enhancing the reproducibility and stability of the sensor platform. The fabricated portable sensor demonstrated the ability to detect CEA in an early stage with high sensitivity and selectivity. Quantification and optimization were performed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) in 0.05 M phosphate buffer solution (PBS, pH 7.0) with 0.1 M KCl [Fe-(CN)₆]^3-/4- (5 mM) electrolyte system. The lower limit of detection (LOD) for CEA was found to be 7.6 ng mL^-1. Practical applicability was confirmed by evaluating human serum samples, achieving recovery rates in the range of 98.06% to 99.69%.