(Invited) T-Chip, a Biosensor Based on the Electron Tunneling: Theory and Experiment

Monday, 29 May 2017: 10:00
Grand Salon A - Section 4 (Hilton New Orleans Riverside)
Y. J. Park, J. Y. Yun, W. C. Lee, Y. E. Lee, and K. Y. Kim (Dept of ECE, Seoul National University)
The presentation covers an electrical biosensor platform (T-chip) based on the electron tunneling phenomenon between the metal electrode and the methylene blue (MB) molecules. Firstly, the general idea of the T-chip is introduced. Secondly, the practical application of the T-chip for detecting biomarkers of the cancer is suggested. Finally, the numerical simulation of the T-chip considering the electron tunneling and the transport of ions in the electrolyte is introduced.

To detect the target biomarkers in aqueous solution, the T-chip is integrated with the peptide molecules as the probe molecule of which end terminal was functionalized with the redox sites providing the electron states for tunneling. An asymmetric gold electrode structure of the T-chip facilitates a simple 2-electrode structure and reliable electrical measurement without adopting a reference electrode used in the conventional electrochemical system.

As an example of the biosensor application, we selected the matrix metalloproteinase-9 (MMP-9) as the target biomarker which indicates metastasis of the cancer and tumor invasion. As the probe molecules, a peptide sequence conjugated with the MB was designed to be cleaved by the MMP-9. As an electrical indicator of the probe-target cleavage event, the MB was chosen. The cleavage event causes the reduction of the number of the MB sites (electron tunneling states) which leads a decrease in the electron tunneling current.

To describe the physical model and evaluate the electrical characteristics of the T-chip, a numerical simulator (3-dimension) has been developed. To estimate the electron tunneling rates between the electrodes and the MB states, we used the non-equilibrium Green’s function (NEGF) method. Additionally, the ion motions in electrolyte is calculated by using drift-diffusion as the continuity equation. Finally, the terminal current due to the electron tunneling and ion movement was extracted by using the extended Ramo-Shockley theorem.

Theory and experiment of the tunneling based biosensor will enhance the potential of success of the electrical biosensor through detailed understanding of the molecules and surface chemistry involved in the sensor system.