Label-free detection of cardiac biomarker using aptamer based capacitive biosensor

Abstract An aptamer based capacitive label-free biosensor was developed for the detection of a cardiac biomarker (C-reactive protein, CRP), based on charge distribution under the applied frequency by Non-Faradaic Impedance Spectroscopy. This capacitive biosensor is based on reagentless processing and developed using gold-interdigitated (GID) capacitor arrays functionalized with synthetic RNA-aptamers. The change in relative capacitance occurred by formation of RNA-CRP complex on GID-capacitors against the applied AC electrical frequency (50–350 MHz) was measured. The binding affinity (Kd) of the RNA-aptamer with CRP was determined and the results showed that at frequencies of 208 and 306 MHz the strong binding occurred with K d = 1.6 μ M and 3.4 μ M , respectively. The dynamic range for CRP was determined to be within 100–500 pg/ml. Our results demonstrate the sensitive detection of RNA-protein complex on GID-capacitors under the applied electric field, which can be extended to other disease protein biomarkers for the development of electrical biosensors.