Review—Advances in Biosensors for Detecting Human Epidermal Growth Receptor-2 Antigen in Serum for Breast Cancer

Breast cancer in women accounts for the second highest number of deaths worldwide. Among the various methods available, bio-sensing/immunosensing methods are comparatively more simple, rapid, sensitive, and specific. These biosensors detect the human epidermal growth factor receptor-2 (HER2) secreted in the serum of breast cancer patients at early stage of cancer. This review describes three types of biosensors depending on type of detection techniques used: Electrochemical techniques, including amperometric, voltametric, and impediametric; Piezoelectric techniques; and Optical techniques, including surface plasmon resonanance and fluorescence. These biosensors worked in the antibody concentration range, 1 fg ml−1 to 500 ng ml−1 or 2 cells/ml with LOD ranging from 1 fg ml−1 to 0.2 ng ml−1 under the optimal assay conditions of pH (7.4−7.5), temperature (25 °C), and response time (10–30 min). The biosensors measured HER2 antigen level in sera of cancer patients, which was significantly higher than those in apparently healthy persons. The biosensors showed good storage stability (40–60 days) and regeneration ability. The merits and demerits of each class of immune-sensors are discussed. These biosensors could be miniaturized to make them portable to use at the bedside of patients.