Biosensor response from target molecules with inhomogeneous charge localization
Yoshihiro Kobayashi, Osaka University
Carbon nanotube thin film transistors (CNT-TFTs) have been utilized for highly sensitive detection of biomolecules. In principle, the sensor response is originated from conductivity change of channel CNT film caused by the effective charge of target molecules near CNT surface within the Debye length. Accordingly, the charge distribution in the target molecule and its interaction with CNT channel should strongly affect the sensor behavior.
In this work , the sensor response from aptamer-modified CNT-TFTs was analyzed in detail. Immunoglobulin E (IgE) with an inhomogeneous charge distribution was used as target molecule, which spontaneously adsorbs at a specific site of the aptamer bonded to the CNT surface. The net charge of target molecules in the Debye length reflects the polarity of the electrical sensor signal. The complicated sensor response, which depends on the Debye length, can be interpreted by two kinds of adsorption states considering the influence of steric hindrance by previously adsorbed IgE molecules. These results explain the anomalous behavior of the sensor response in previous reports and pave the way for quantitative analysis of biomolecules with high dynamic range and sensitivity. H. Kase, R. Negishi, M. Arifuku, N. Kiyoyanagi, Y. Kobayashi, "Biosensor response from target molecules with inhomogeneous charge localization", J, Appl. Phys., 124(2018)064502.