Electrochemical biosensing of sperm protein 17 in clinical samples using a hydrothermally synthesized MoS ₂ @rGO@MWCNTs ternary system without prior pre-treatment

Sperm protein-17, also known as Sp17, is a testis-linked cancerous antigen found in various cancers, making it a potential biomarker for cancer detection. However, detecting Sp17 in human serum is challenging due to its low concentration and the absence of sensitive, specific detection methods. This study presents a fast, accurate, reliable, and cost-effective biosensor for Sp17 detection, utilizing a disposable carbon cloth (CC)-based electrode modified with a ternary nanosystem of molybdenum disulfide (MoS₂), reduced graphene oxide (rGO), and multi-walled carbon nanotubes (MWCNTs). The ternary nanosystem was prepared through a simple hydrothermal approach and characterized using various techniques, including X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and electrochemical studies, which confirmed its robust formation and suitability for Sp17 sensing. The nanosystem exhibited electrocatalytic activity, biocompatibility, and stability. A Sp17-specific antibody (anti-Sp17) was attached to the surface of the electrode, and the immunosensor showed a linearity range from 0.01 to 11 ng mL^-1 with a detection limit (LOD) of 0.23 ng mL^-1 as well as a limit of quantification (LOQ) of 0.79 ng mL^-1, achieving a sensitivity of 9.97 μA ng mL^-1 cm². The mechanism behind the sensing is attributed to charge transfer-induced shifts in the Fermi level, causing band bending at the interface between the nanosystem and the target molecule, leading to enhanced sensitivity. The theoretical analysis correlates these Fermi energy shifts with device sensitivity, particularly with antibody immobilization. The immunosensor was successfully used to detect Sp17 in human serum samples, showing good accuracy, reproducibility, and selectivity. It also correlated with a commercial enzyme-linked immunosorbent assay (ELISA), suggesting its potential for clinical diagnostics, particularly for ovarian and other Sp17-related cancers.