Design, fabrication and performance evaluation of interdigital capacitive sensor for detection of Cardiac Troponin-I and Human Epidermal Growth Factor Receptor 2

An interdigital capacitive biosensor has been designed and fabricated for label free detection of cardiac troponin-I (cTn-I) and Human Epidermal Growth Factor Receptor 2(HER2), cardiovascular disease (CVD) and cancer biomarkers respectively. CVD and cancer comprises of many disorders/types and various protein markers indicate the risk of the disease. In order to facilitate simultaneous multiple detection, a sensor chip, which has 2 rows of 6 interdigital capacitor (IDC) arrays was designed and fabricated. The chip was designed using simulation software (Sonnet) and fabricated on borofloat substrate using image reversal photolithography (for pattern transfer) and DC sputtering (for gold deposition). The IDC surface was functionalized using 2% 3-glycidoxypropyl trimethoxysilane (GPTMS) for antibody immobilization. The antibody-antigen binding on the IDC surface results in change in the capacitance of the IDC sensor. This change is directly related to the concentration of the antigen binding to the surface which helps in the quantification. Highly specific and sensitive detection of HER2 and cTn-I protein in real human serum was captured by anti-HER2 and anti-cTn-I antibody immobilized on IDC surface with a detection range of 5 pg/mL–5 ng/ml and50pg–1500 pg/ml respectively has been demonstrated.