Development of a sensitive antibody-based label-free electrochemical immunosensors for breast cancer diagnosis

Early detection of human epidermal growth factor receptor 2 (HER2) is crucial for effective breast cancer treatment. This research focuses on the development of a sensitive, label-free electrochemical immunosensor for detecting HER2, which plays a key role in breast cancer diagnosis. The sensor employs a gold electrode functionalized with carboxylic acid molecules (11-mercaptoundecanoic acid, 3-mercaptopropionic acid), activated by coupling agents and modified with anti-HER2 antibodies. Key parameters such as pH, incubation time, and antibody concentration were optimized to enhance the immunosensor's performance. Using differential pulse voltammetry (DPV), the immunosensor achieved a limit of detection (LOD) of 2.3 fM within a range of 0.10 nM to 100 nM. To further improve detection limits and sensitivity, protein G (PG) was incorporated into the next iteration of the immunosensor. Again, a gold electrode was used as the main component, this time functionalized with L-cysteine (CYS) and PG. The PG-enhanced sensor exhibited improved sensitivity and a LOD of 0.51 fM, with a linear range from 1 fM to 0.10 nM. The sensor demonstrated high selectivity for HER2 and maintained performance in human serum samples. These results highlight its potential for rapid diagnostic applications in breast cancer monitoring.