Magnetically induced self-assembly electrochemical biosensor with ultra-low detection limit and extended measuring...

An innovative electrochemical biosensor was fabricated for sensitive detection of human epidermal growth factor receptor 2 (HER2) protein, which was considered as an essential tumor marker for diagnosis and treatment evaluation of breast cancer. The sensor was constructed using Apt and PNA as recognition probes incorporated with magnetic Fe₃O₄/α-Fe₂O₃@Au nanocomposites. The sensing strategy was designed to lower the detection limit of HER2, and avoid the large steric interference caused by macromolecular HER2 on the electrode surface. Rigid structure dsDNA (Apt/ssDNA) was designed to improve the sensitivity of the sensor. Apt captured the macromolecular HER2 protein, and ssDNA chains were simultaneously released, causing a sensitive change in the electrochemical signal. PNA captured the released ssDNA chains, which converted the electrochemical signal changes caused by HER2 to those caused by the number of short strand ssDNA, so the detection range was extended. Under optimized conditions, this sensing strategy realized an ultra-low detection LOD of HER2 (4.1 fg·mL^-1), and the detection range was 10 fg·mL^-1-5 × 10⁶ fg·mL^-1. The experimental results confirmed that the electrochemical biosensor had excellent selectivity, reproducibility, and storage stability. Analysis of spiked serum samples exhibited a recovery rate of 95.9-115.7 %, which indicated great promise for HER2 detection in serum samples.