Label-Free Electrochemical Immunosensor Based on One-Step Electrochemical Deposition of AuNP-RGO Nanocomposites for Detection of Endometriosis Marker CA 125

Endometriosis is the third most prominent gynecological disorder. Cancer antigen 125 (CA 125) is the primary serum marker used for late-stage endometriosis diagnosis and management. Herein, we developed a label-free immunosensor for electrochemical detection of CA 125 for endometriosis blood serum samples. The sensor was fabricated by one-step electrochemical deposition of highly conductive gold nanoparticles (AuNPs) and reduced graphene oxide (RGO) nanocomposite, via one-step electrochemical deposition. This method involved in situ reduction of HAuCl₃ and graphene oxide and increased electrocatalytic performance. Different analytical techniques confirmed the morphology and structure of the AuNP/RGO nanocomposite. In addition, the antibody (Ab) was immobilized on the modified electrode surface through the self-assembly monolayer. The square wave voltammetry method has been utilized to measure the interaction of Ab and antigen (Ag). The as-fabricated sensor demonstrates a dynamic linear range of 0.0001 → 300 U mL^-1 and lower limit of detection is 0.000042 U mL^-1 toward CA125 detection. The developed sensor provides acceptable stability, high selectivity, and reproducibility. The proposed immunosensor has been applied to the CA 125 detection in endometriosis patient blood samples, and the results confirm the reliability of the as-fabricated sensor that is further associated with the standard ELISA analysis. The AuNP/RGO-based sensor can be used as an excellent tool for future prospective clinical diagnostics applications.