A novel immunosensor based on nanostructured modified electrodes with a conductive copolymer film and gold nanoparticles electrodeposited in ethaline deep eutectic solvent (DES) for the detection of the HER2 ECD breast cancer biomarker

This study introduces a highly sensitive and innovative electrochemical immunosensor for detecting the extracellular domain of human epidermal growth factor receptor 2 (HER2 ECD), a critical biomarker for breast cancer diagnosis. The immunosensor integrates a gold nanoparticle (AuNP)-modified nanostructured electrode with a conductive copolymer film, poly(an-co-8-ansa), synthesized and electrodeposited in an ethaline deep eutectic solvent (DES) doped with HClO₄. This novel approach employs DES not only as a medium for electrode modification but also as a strategy for enhancing the sensor’s uniformity, stability, and electrochemical performance. The platform achieved a limit of detection (LoD) of 0.98 ng mL⁻¹, and the limit of quantification (LoQ) was 3.25 ng mL⁻¹, which is lower than previously reported HER2 ECD biosensors, and demonstrated a linear detection range of 1.0–150 ng mL⁻¹. The immunosensor’s performance was validated in human plasma, revealing its potential for clinical applications. The characterization through cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy confirmed the enhanced properties of the DES-based copolymer films and nanostructures. Integrating DES with AuNP and poly(an-co-8-ansa) film represents a significant advancement in biosensor technology, providing a cost-effective, sensitive, and robust tool for early breast cancer detection. This is the first reported immunosensor leveraging DES for HER2 ECD detection, representing a transformative advancement in biosensing technology. Its sensitivity effectively encompasses the critical HER2 levels observed in breast cancer patients, underscoring its potential as a reliable and powerful tool for future breast cancer diagnosis.