K. Maehashi and K. Matsumoto (Japan)
carbon nanotube field-effect transistors, local electrolyte gate, channel conductance modulation, label-free protein biosensors, aptamers, association constant
Carbon nanotube field-effect transistors (CNTFETs) with local electrolyte gated in solution provided high performance in terms of subthreshold slope and transconductance, resulting from the modulation of the conduction in the carbon nanotube channel and the large gate capacitance. Using the CNTFETs, label-free protein biosensors have been fabricated to detect immunoglobulin E (IgE), in which CNT channels were modified with aptamers. Since aptamers are artificial oligonucleotides, the aptamers are smaller in size than the Debye length. Therefore, the biosensors are expected to detect IgE with high sensitivity. After the 5’- amino modified aptamers were covalently immobilized on the CNT channels, the electrical properties of the CNTFETs were monitored in real time. The introduction of target IgE at various concentrations caused a sharp decrease in the source-drain current and gradual saturation at lower values. From electrical measurements in IgE concentration dependent, the association constant between IgE molecules and IgE aptamer could be calucated to be 5.14 × 108 (M-1 ) using the Langmuir adsorption isotherm.
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