Development of label-free immunosensors based on AuNPs-fullerene nanocomposites for the determination of cancer antigen 125

In this study, gold nanoparticles (AuNPs) were synthesized and combined with fullerene, resulting in the formation of nanocomposite structures. The structures were then characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. The nanostructures were functionalized with MPA and employed for covalent binding of CA125 antibody, whereby the antibody-bound nanocomposite structure was utilized for modification of the surface of the SPE. The surface of the immunosensor was protected by Nafion, and the individual stages of the immunosensor design were characterized by CV and EIS. CA125 determination was conducted using the EIS technique, which revealed a linear concentration range of 1–100 U·mL⁻¹ and a LOD value of 0.016 U·mL⁻¹. The immunosensor demonstrated selective recognition of CEA, NSE, HSA, and IgG proteins, exhibiting good reproducibility. The prepared immunosensor demonstrated 80.9% activity even after a 30-day period. Moreover, this immunosensor can be successfully employed in conventional clinical human serum applications. A comparison with existing literature reveals that the superior features of this immunosensor are its low LOD and high stability. Additionally, the short analysis time in comparison to commercial kits is considered a significant advantage. The prepared immunosensor displays valuable characteristics for the determination of CA125, and it has the potential to be developed for use in health applications.