A Review on Nanostructured Electrochemical Immunosensors for the Determination of HER2, a Breast Cancer Biomarker

The amplification or overexpression of HER2, which is observed in approximately 15–20 % of breast cancer patients, is known to be associated with unfavorable prognosis in patients with breast cancer. Current techniques which have been approved for the detection of HER2 status such as in-situ hybridization (ISH) and immunohistochemistry (IHC) are costly, time-consuming, have limited sensitivity and selectivity, and also very invasive, limiting their applicability at the clinic in certain settings. However, electrochemical biosensors are most appropriate based on their relative simplicity with respect to instrumentation and analysis, low cost per assay, high selectivity and superior sensitivity, reliability, fast response time and their potential for miniaturization and scalability. Electrochemical immunosensors have shown promise as fast, easy to fabricate, low-cost, and sensitive sensors for the determination of HER2 mRNA/protein levels. These biosensors take advantage of chemical stability, high surface area, and biocompatibility of antibodies, their high affinity and specificity, and unique conductive properties of nanomaterials to selectively and sensitively determine HER2 levels in biological fluids. In this review, we covered electrochemical immunosensors developed for the determination of HER2 levels in biological fluids such as human serum. We highlighted specific sensing capabilities and analytical performance parameters of these immunosensors, also detailing the design of these electrochemical HER2 immunosensors.