Integrated Magnetophoretic-Electrochemical platforms for portable detection of HER2 in breast cancer diagnosis.

Early and accurate diagnosis of breast cancer is essential for guiding less invasive and more effective treatment. The overexpression of human epidermal growth factor receptor 2 (HER2) is a key molecular biomarker for breast cancer classification and treatment selection. However, conventional HER2 detection methods, such as immunohistochemistry and ELISA, suffer from limitations including invasive sampling, high cost, and labor-intensive procedures. In this work, we present a magnetic bead-based electrochemical capillary-driven immunoassay (meCaDI). This platform combines magnetic bead-based target enrichment, sensitive electrochemical detection, and a capillary-driven microfluidic format suitable for point-of-care (POC) applications. HER2 is first captured using antibody-functionalized magnetic beads. A sandwich immunocomplex is then formed using a biotinylated detection antibody and a horseradish peroxidase (HRP)-labeled streptavidin conjugate. The complex is magnetically concentrated at the detection zone, where HRP catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Automated reagent delivery and removal are achieved through a low-cost capillary-driven microfluidic device, eliminating the need for washing steps. The system was progressively optimized from a static assay to a semi-automated magnetophoretic slider platform and finally to the fully integrated meCaDI device. The meCaDI platform achieved a limit of detection of 5.8 ng/mL for HER2 and showed good recovery in spiked serum samples (89.36-129.20%). These results demonstrate a sensitive, specific, and portable biosensing platform for HER2 detection, highlighting its potential for on-site breast cancer diagnostics.