Ovarian cancer remains among the deadliest gynecological malignancies globally, attributed to the absence of identifiable signs, symptoms, and effective screening methods. The design, fabrication, and advancement of reliable, non-invasive diagnostic equipment is a pivotal necessity in preventing and treating this disease. A prominent biomarker for diagnosing ovarian cancer is the cancer antigen 125 (CA-125). In healthy individuals, CA-125 typically maintains a blood concentration of less than 35 U/mL and serves as a crucial indicator for diagnosing and prognosing ovarian cancer. In the present study, the label-free detection of CA-125 on graphene–gold nanocomposite was executed with higher sensitivity with the aid of a 3,3’-dithiolbis(succinimidylpropionate) (DSP) linker for the stable immobilization of the antibody.

Graphene has exceptional electron mobility, allowing very small biological interactions such as antigen–antibody binding to cause measurable changes in electrical signals—leading to high sensitivity. Additionally, the higher surface area, excellent biocompatibility, and fast response time enhance the application of graphene in biosensors. Gold nanodendrites are commonly applied in electronic devices and sensors due to their distinct advantages, such as their large surface area and excellent conductivity, and to preserve the immobilization of biomolecules. In the present study, AuNDs were electrochemically deposited onto graphene and decorated with self-assembled monolayers (SAM) of DSP via the Au-S bond. In the following step, DSP interacted with the primary amine groups from the anti CA-125 antibody to form a stable amide bond. This linker-mediated stable immobilization of the antibodies enabled the successfull capture of CA-125, enhancing sensor performance. The electrochemical detection of CA-125 was carried out on the nanocomposite electrode by monitoring the impedance spectra and ferricyanide response as a measure of CA-125 concentration. Sensitive detection was recorded for the wide range of concentrations, and the stability and reproducibility of the modified electrode were studied. Finally, efficiency was assessed in real blood serum samples and validated with conventional screening methods.