This paper describes a chemical detection strategy utilizing biological nanopores reconstituted in a lipid bilayer formed on the surface of a gold nanoneedle. Nanopore sensing with biological nanopores can detect analytes such as DNA, peptides, and organic molecules at the single-molecule level. In this study, we demonstrate a nanoneedle-based nanopore probe to improve the spatial resolution of nanopore measurements when incorporated into a scanned probe microscopy. Nanoneedle probes comprise gold nanoneedles that are fabricated by electrochemical etching of a 250 μm-diamter gold wire in a CaCl<sub>2</sub> solution. The nanoneedles are modified with thiolated polyethylene glycol (PEG) to prepare a hydrophilic surface sufficient to support a lipid bilayer membrane. To form a membrane, the nanoneedle probe is immersed in a solution of two immiscible layers – an organic/lipid mixture and an aqueous electrolyte solution. When the tip is pushed through the interface of these two layers, a lipid bilayer is formed on the tip. Membrane proteins can be reconstituted into the lipid bilayer, and the channel current recorded using a patch clamp amplifier. In this study, we employed α-hemolysin (αHL) as a representative nanopore, and β-cyclodextrin (βCD) molecules were include in the bath solution as the target molecule. We observed quantized increases in current with the incorporation of αHL, and blocking signals caused by the translocation of βCD in the αHL cannels. However, the channel current and the binding event frequency decayed with time presumably because of the small volume of electrolyte solution in the PEG layer on the needle. To improve this decay, we applied asymmetric salt conditions in the PEG layer and the bath solution. As a result, lower decays of the channel current and event frequency were observed. We believe that the nanoneedle-based nanopore probe has a potent candidate as the high spatial resolution imaging system using ion channels.

Chemical sensing using a nanoneedle-based nanopore probe

256th National Meeting (2018)

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