Monitoring of C-Reactive Protein Using Ion Sensitive Field Effect Transistor Biosensor

An ion sensitive field effect transistor (ISFET) as a transducer, more precisely an immunologically modified-FET (immuno-FET) device, was utilized for the detection of the C-reactive protein (CRP), a potent marker for inflammation or cardiac risk. The ISFET biosensor investigated in this study was fabricated via a standard CMOS process. Anti-CRP monoclonal antibody was covalently attached to the gate surface using the self-assembled monolayer (SAM) method. The response of anti-CRP antibody to CRP was evaluated via the measurement of the electrical features of the ISFET device. As a consequence, a considerable reduction in drain current was clearly noted upon CRP binding to anti-CRP antibody on the gate, which can be explained by the charge effect, in which negatively charged CRP is predominantly responsible for the current drop in the n-type ISFET. The FET measurement was also verified by surface plasmon resonance (SPA) analysis. Collectively, our data convincingly showed that the FET-type biosensor is potentially applicable to the detection of CRP via antigen antibody binding events on the gate surface.