Aptamer-Based Label-Free Immunosensors Using Carbon Nanotube Field-Effect Transistors

Aptamer-based label-free immunosensors were fabricated for immunoglobulin E (IgE) detection using carbon nanotube field-effect transistors (CNTFETs). Aptamers are artificial oligonucleotides and thus are smaller than the Debye length. After aptamers were covalently immobilized on CNT channels. the electrical properties of the CNTFETs were monitored in real time. Introduction of IgE at various concentrations Caused a sharp decrease in the source-drain current and gradual saturation at lower Currents. From the measurement of the dependence of CNTFET electrical properties on IgE concentration, the dissociation constant between aptamer and IgE reactions was estimated to be 1.9 x 10(-9) M using the Langmuir adsorption isotherm.