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Center for Nonlinear Studies |
We have fabricated single asymmetric nanopores which mimic behavior of biological voltage-gated channels. The pores have been prepared by the track-etching technique based on irradiating polymer films with energetic heavy ions and subsequent chemical etching of the latent ion tracks. The pores are conical in shape with the small opening as small as several nm and the big opening in the micrometer range. We have designed two nanotube systems, which exhibit ion current rectification through two distinct mechanisms (i) electrostatic interactions, based on asymmetric, ratchet-like shape of electrostatic potential inside the pore, and (ii) electro-mechanical gate placed at the entrance of the conical pore, responsive to the external field applied across the membrane. The direction and degree of rectification can be modulated by the control of surface chemistry. We have also designed single nanopore system, which produces voltage-dependent ion current fluctuations with the kinetics of opening and closing similar to voltage-gated ion channels in biological membranes. I will also discuss application of synthetic voltage-gated nanopores as platforms in biosensing. The internal surfaces of the nanopores have been modified with a specific biochemical molecular-recognition agent (the "capture" agent, e.g., an antibody) which interacts specifically with a given biomolecule (the analyte) brought into contact with the nanotube. The binding interaction between the nanotube-bound capture agent and the solution-phase analyte is transduced as a change in the ion current that flows through the nanotube. We have demonstrated operation of the sensor for detection of ricin and immunoglobins