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Zhang L, Wahab OJ, Jallow AA, O’Dell ZJ, Pungsrisai T, Sridhar S, Vernon KL, Willets KA, Baker LA. Recent Developments in Single-Entity Electrochemistry. Anal Chem 2024; 96:8036-8055. [PMID: 38727715 PMCID: PMC11112546 DOI: 10.1021/acs.analchem.4c01406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Affiliation(s)
- L. Zhang
- Department
of Chemistry, Texas A&M University, College Station, Texas 77845, United States
| | - O. J. Wahab
- Department
of Chemistry, Texas A&M University, College Station, Texas 77845, United States
| | - A. A. Jallow
- Department
of Chemistry, Texas A&M University, College Station, Texas 77845, United States
| | - Z. J. O’Dell
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - T. Pungsrisai
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - S. Sridhar
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - K. L. Vernon
- Department
of Chemistry, Texas A&M University, College Station, Texas 77845, United States
| | - K. A. Willets
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - L. A. Baker
- Department
of Chemistry, Texas A&M University, College Station, Texas 77845, United States
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2
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Hussein EA, Rice B, White RJ. Tuning the Probe-Bilayer Architecture of Silver Nanoneedle-based Ion Channel Probes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:7234-7241. [PMID: 38498453 DOI: 10.1021/acs.langmuir.4c00454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Ion channel probes, as one of the ion channel platforms, provide an appealing opportunity to perform localized detection with a high precision level. These probes come basically in two classes: glass and metal. While the glass-based probes showed the potential to be employed for molecular sensing and chemical imaging, these probes still suffer from limited resolution and lack of control over protein insertion. On the other hand, metal-based nanoneedle probes (gold and silver) have been recently developed to allow reducing probe dimensions to the nanoscale geometry. More specifically, silver probes are preferable owing to their ability to mitigate the channel current decay observed with gold probes and provide a stable DC channel current. However, there are still some challenges related to the probe design and bilayer curvature that render such probes insensitive to small changes in the tip-substrate distance. Herein, we introduce two main pathways to control the probe-bilayer architecture; the first is by altering the probe shape and geometry during the fabrication process of silver probes. The second pathway is by altering the surface characteristics of the silver probe via an electrophoretic deposition process. Our findings reveal that varying the electrochemical etching parameters results in different probe geometries and producing sharper tips with a 2-fold diameter reduction. In addition, the electrophoretic deposition of a cathodic paint on the silver nanoneedle surface led to a miniaturized exposed silver tip that enables the formation of a confined bilayer. We further investigated the characteristics of bilayers supported on both the sharper nanoneedles and the HSR-coated silver probes produced by controlling the etching conditions and electrodeposition process, respectively. We believe this work paves the way to rationally design silver nanoneedle ion channel probes, which are well suited for localized molecular sensing and chemical imaging.
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Affiliation(s)
- Essraa A Hussein
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Brittany Rice
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Ryan J White
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
- Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, Ohio 45221, United States
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3
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Mimura H, Osaki T, Takamori S, Nakao K, Takeuchi S. Lipid Bilayer Reformation Using the Wiping Blade for Improved Ion Channel Analysis. Anal Chem 2023; 95:17354-17361. [PMID: 37968939 DOI: 10.1021/acs.analchem.3c03707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
The measurement of ion permeation activity across planar lipid bilayers is a useful technique for the functional analysis and drug evaluation of ion channels at the single-molecule level. To enhance the data throughput, parallelization of lipid bilayers is desirable. However, existing parallelized approaches face challenges in simultaneously and efficiently measuring ion channel activities under various conditions on one chip. In this study, we propose an approach to overcome these limitations by developing a device capable of repeated measurements of ion channels incorporated into individually arrayed lipid bilayers. Our device forms an array of a lipid bilayer at a micropore on a separator by merging two lipid monolayers assembled on the surface of aqueous droplets. We introduce a vertically moving, blade-shaped module─referred to as a "wiping blade"─which enables controlled disruption and reformation of the bilayer at the micropore. By optimizing the surface properties and clearance of the wiping blade, we successfully achieved repeated bilayer formation. The arrayed lipid bilayer device with the integrated wiping blade module demonstrates a 5-fold improvement in data throughput during ion channel activity measurements. Finally, we validate the practical utility of our device by evaluating the effects of an ion channel inhibitor. The developed device opens new avenues for high-throughput analysis and screening of ion channels, leading to significant advancements in drug discovery and functional studies of membrane proteins. It offers a powerful tool for researchers in the field and holds promise for accelerating drug development by targeting ion channels.
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Affiliation(s)
- Hisatoshi Mimura
- Kanagawa Institute of Industrial Science and Technology, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
| | - Toshihisa Osaki
- Kanagawa Institute of Industrial Science and Technology, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
- MAQsys Inc., 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
| | - Sho Takamori
- Kanagawa Institute of Industrial Science and Technology, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
| | - Kenji Nakao
- MAQsys Inc., 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
| | - Shoji Takeuchi
- Kanagawa Institute of Industrial Science and Technology, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
- Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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4
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Hussein EA, White RJ. Maintaining Single-Channel Recordings on a Silver Nanoneedle through Probe Design and Feedback Tip Positioning Control. J Phys Chem B 2022; 126:10111-10119. [PMID: 36395597 DOI: 10.1021/acs.jpcb.2c06275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ion channel proteins showed great promise in the field of nanopore sensing and molecular flux imaging applications due to the atomic-level precision of the pore size and a high signal-to-noise ratio. More specifically, ion channel probes, where the protein channels are integrated at the end of a solid probe, can achieve highly localized detection. Metal probe materials such as gold and silver have been developed to support lipid bilayers and enable the use of smaller probes, or nanoneedles, compared to more traditional glass micropipette ion channel probes. Silver probes are preferable because they support sustained DC stable channel current due to the AgCl layer formed around the tip during the fabrication process. However, one of the current challenges in ion channel measurements is maintaining a single-channel recording. Multiple protein insertions complicate data analysis and destabilize the bilayer. Herein, we combine the promising probe material (Ag/AgCl) with an approach based on current feedback-controlled tip positioning to maintain long-term single-channel recordings for up to 3 h. We develop a hybrid positioning control system, where the channel current is used as feedback to control the vertical movement of the silver tip and, subsequently, control the number of protein channels inserted in the lipid membrane. Our findings reveal that the area of the lipid bilayer decreases with moving the silver tip up (i.e., decreasing the displacement in the z-direction). By reducing the bilayer area around the fine silver tip, we minimize the probability of multiple insertions and remove unwanted proteins. In addition, we characterize the effect of lipid properties such as fluidity on the lipid membrane area. We believe that the use of silver nanoneedles, which enables DC stable channel current, coupled with the developed tip displacement mechanism will offer more opportunities to employ these probes for chemical imaging and mapping different surfaces.
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Affiliation(s)
- Essraa A Hussein
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio45221, United States
| | - Ryan J White
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio45221, United States.,Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, Ohio45221, United States
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5
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Hussein EA, Rice B, White RJ. Recent advances in ion-channel probes for nanopore sensing: Insights into the probe architectures. Anal Chim Acta 2022; 1224:340162. [DOI: 10.1016/j.aca.2022.340162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 07/05/2022] [Accepted: 07/08/2022] [Indexed: 11/01/2022]
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6
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Hasegawa N, Shoji K. Microcavity volume control on a tip of Ag/AgCl electrodes for stable channel current measurements of biological nanopores. Analyst 2022; 147:1191-1198. [PMID: 35195650 DOI: 10.1039/d2an00014h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A probe-type channel current measurement system with a planer bilayer lipid membrane (pBLM) at the tip of a probe provided several advantages for pBLM formation and channel current measurements. The procedure for preparing pBLMs was simple (i.e., the probe was submerged into a bath solution layered by an oil/lipid mixture and buffer solution). The probe systems offered local detection of analytes by nanopore sensing. Nevertheless, the current decay caused by changing the ion concentration in the electrolyte held on the tip of the probes influenced the sensing accuracy. Here we applied a cavity microelectrode (CME) technique to fabricate pBLM probes with larger electrolyte volume on the tip. We fabricated silver CMEs with different cavity volumes and measured channel currents of biological nanopores. Furthermore, we evaluated the channel current decay as a function of cavity volume by analyzing the step signals of α-hemolysin nanopores. Consequently, the channel current decay was extended by increasing the cavity volume, indicating that the volume of the electrolyte solution was important for channel current measurements of nanopores. We concluded that the pBLM system using CMEs is useful for channel current measurements of biological nanopores. Additionally, the fundamental evaluation of the relationship between the electrolyte volume and channel current decay will be helpful in the design of pBLM systems made by microfabrication and microfluidic techniques.
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Affiliation(s)
- Naru Hasegawa
- Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
| | - Kan Shoji
- Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
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7
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Shoji K. De-Insertion Current Analysis of Pore-Forming Peptides and Proteins Using Gold Electrode-Supported Lipid Bilayer. Methods Mol Biol 2022; 2402:93-102. [PMID: 34854038 DOI: 10.1007/978-1-0716-1843-1_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Analysis of the pore formation mechanisms of transmembrane peptides and proteins potentially provides an insight into cellular biology because of their significant roles in biological systems. Here, we describe the procedures to analyze the pore formation mechanisms of transmembrane peptides and proteins by measuring de-insertion currents of biological nanopores that can be obtained by unzipping the lipid bilayers.
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Affiliation(s)
- Kan Shoji
- Department of Mechanical Engineering, Nagaoka University of Technology, Niigata, Japan.
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8
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Development of an automated system to measure ion channel currents using a surface-modified gold probe. Sci Rep 2021; 11:17934. [PMID: 34504175 PMCID: PMC8429628 DOI: 10.1038/s41598-021-97237-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 08/18/2021] [Indexed: 11/08/2022] Open
Abstract
Artificial lipid bilayer single-channel recording technique has been employed to determine the biophysical and pharmacological properties of various ion channels. However, its measurement efficiency is very low, as it requires two time-consuming processes: preparation of lipid bilayer membranes and incorporation of ion channels into the membranes. In order to address these problems, we previously developed a technique based on hydrophilically modified gold probes on which are immobilized ion channels that can be promptly incorporated into the bilayer membrane at the same time as the membrane is formed on the probes' hydrophilic area. Here, we improved further this technique by optimizing the gold probe and developed an automated channel current measurement system. We found that use of probes with rounded tips enhanced the efficiency of channel current measurements, and introducing a hydrophobic area on the probe surface, beside the hydrophilic one, further increased measurement efficiency by boosting membrane stability. Moreover, we developed an automated measurement system using the optimized probes; it enabled us to automatically measure channel currents and analyze the effects of a blocker on channel activity. Our study will contribute to the development of high-throughput devices to identify drug candidates affecting ion channel activity.
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9
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Hussein EA, White RJ. Silver Nanoneedle Probes Enable Sustained DC Current, Single-Channel Resistive Pulse Nanopore Sensing. Anal Chem 2021; 93:11568-11575. [PMID: 34378930 DOI: 10.1021/acs.analchem.1c02087] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Resistive pulse sensing using ion channel proteins (biological nanopores) has been evolving as a single-molecule approach to detect small biomolecules owing to atomically precise pore size reproducibility, high signal-to-noise ratio, and molecular selectivity. The incorporation of biological nanopores in sensing platforms requires a stable lipid membrane that can be formed by a variety of methods such as the painting method and droplet-based techniques. However, these methods are limited by the fragility of the unsupported bilayer or the need for specific microdevices. Electrode-supported bilayers, in which a metal electrode is used as a support structure, have been recently developed using a fine gold nanoneedle. We previously described the utility of the gold nanoneedle-supported ion channel probe to detect small molecules with high spatial resolution; however, it exhibited a channel current decay over time, which affected the binding frequency of the target molecule to the protein pore as well. Here, we introduce a silver nanoneedle probe to support the lipid bilayer formation and ion channel measurements. The silver nanoneedle mitigates the current decay observed on gold electrodes and produces stable DC channel currents. Our findings propose the formation of a AgCl layer creating a nonpolarizable electrode. The new nanoneedle is successfully applied for single-molecule detection of sulfonated β-cyclodextrin (S7βCD) using αHL as a test bed protein. We believe that this new silver nanoneedle platform has great potential given the relative ease of lipid bilayer formation and stable open channel currents.
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Affiliation(s)
- Essraa A Hussein
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Ryan J White
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States.,Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, Ohio 45221, United States
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10
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Hirano M, Yamamoto D, Asakura M, Hayakawa T, Mise S, Matsumoto A, Ide T. A Lipid Bilayer Formed on a Hydrogel Bead for Single Ion Channel Recordings. MICROMACHINES 2020; 11:mi11121070. [PMID: 33271761 PMCID: PMC7759777 DOI: 10.3390/mi11121070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 11/28/2020] [Accepted: 11/29/2020] [Indexed: 02/05/2023]
Abstract
Ion channel proteins play important roles in various cell functions, making them attractive drug targets. Artificial lipid bilayer recording is a technique used to measure the ion transport activities of channel proteins with high sensitivity and accuracy. However, the measurement efficiency is low. In order to improve the efficiency, we developed a method that allows us to form bilayers on a hydrogel bead and record channel currents promptly. We tested our system by measuring the activities of various types of channels, including gramicidin, alamethicin, α-hemolysin, a voltage-dependent anion channel 1 (VDAC1), a voltage- and calcium-activated large conductance potassium channel (BK channel), and a potassium channel from Streptomyces lividans (KcsA channel). We confirmed the ability for enhanced measurement efficiency and measurement system miniaturizion.
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Affiliation(s)
- Minako Hirano
- Bio Photonics Laboratory, The Graduate School for the Creation of New Photonics Industries, Shizuoka 431-1202, Japan;
| | - Daiki Yamamoto
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama 700-8530, Japan; (D.Y.); (M.A.); (T.H.)
| | - Mami Asakura
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama 700-8530, Japan; (D.Y.); (M.A.); (T.H.)
| | - Tohru Hayakawa
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama 700-8530, Japan; (D.Y.); (M.A.); (T.H.)
| | - Shintaro Mise
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan; (S.M.); (A.M.)
| | - Akinobu Matsumoto
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan; (S.M.); (A.M.)
| | - Toru Ide
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama 700-8530, Japan; (D.Y.); (M.A.); (T.H.)
- Correspondence: ; Tel.: +81-86-251-8203
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11
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Shoji K, Kawano R, White RJ. Analysis of Membrane Protein Deinsertion-Associated Currents with Nanoneedle-Supported Bilayers to Discover Pore Formation Mechanisms. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:10012-10021. [PMID: 32787048 DOI: 10.1021/acs.langmuir.0c00833] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Analysis of the pore formation mechanisms of biological nanopores can provide insight into pore-forming peptide-induced diseases and into the characterization of nanopores employed in sensing methods. Evaluation of pore formation mechanisms is typically performed using microscopy including atomic force microscopy, transmission electron microscopy, as well as electrically via channel current measurements using a patch-clamp amplifier. However, due to the relatively low temporal resolution of the above-mentioned microscopy techniques and the low analysis accuracy of the channel current measurements, new analytical methods are required. Here, we describe a new analytical strategy to measure and analyze both ionic currents associated with biological nanopore insertion and deinsertion into and out of lipid bilayers to determine pore formation mechanisms for several representative proteins. The current changes associated with protein deinsertion are monitored as the lipid membrane leaflets are pulled apart-a unique phenomenon enabled by our gold nanoneedle measurement probe. This deinsertion current analysis (DiCA) is performed using a gold nanoneedle-supported lipid bilayer at which a bilayer membrane is formed by bringing together two lipid monolayers on the surface of the nanoneedle and at the interface of an aqueous solution and a lipid/oil mixture. The lipid bilayer can be pulled apart by removing the nanoneedle from this interface. In this study, we demonstrate the determination of pore formation mechanisms for four different pore-forming proteins and peptides-α-hemolysin, streptolysin O, alamethicin, and amyloid β 1-42 using DiCA. As a result, we successfully discern the pore formation mechanism, either addition or expansion, for each protein/peptide by analyzing the ratio and magnitude of insertion and deinsertion current events.
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Affiliation(s)
- Kan Shoji
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
- Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka, Niigata 840-2188, Japan
| | - Ryuji Kawano
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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12
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Shoji K, Kawano R, White RJ. Recessed Ag/AgCl Microelectrode-Supported Lipid Bilayer for Nanopore Sensing. Anal Chem 2020; 92:10856-10862. [PMID: 32597640 DOI: 10.1021/acs.analchem.0c02720] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Biological nanopores reconstituted into supported lipid bilayer membranes are widely used as a platform for stochastic nanopore sensing with the ability to detect single molecules including, for example, single-stranded DNA (ssDNA) and miRNA. A main thrust in this area of research has been to improve overall bilayer stability and ease of measurements. These improvements are achieved through a variety of clever strategies including droplet-based techniques; however, they typically require specific microfabrication techniques to prepare devices or special manipulation techniques for microdroplets. Here, we describe a new method to prepare lipid bilayers using a recessed-in-glass Ag/AgCl microelectrode as a support structure. The lipid bilayer is formed at the tip of the microelectrode by immersing the microelectrode into a layered bath solution consisting of an oil/lipid mixture and an aqueous electrolyte solution. In this paper, we demonstrate this stable, supported lipid bilayer structure for channel current measurements of pore-forming toxins and single-molecule detection of ssDNA. This Ag/AgCl-supported lipid bilayer can potentially be widely adopted as a lipid membrane platform for nanopore sensing because of its simple and easy procedure needed to prepare lipid bilayers.
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Affiliation(s)
- Kan Shoji
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States.,Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo 184-8588, Japan.,Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan
| | - Ryuji Kawano
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo 184-8588, Japan
| | - Ryan J White
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States.,Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, Ohio 45221, United States
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Shoji K, Kawano R, White RJ. Spatially Resolved Chemical Detection with a Nanoneedle-Probe-Supported Biological Nanopore. ACS NANO 2019; 13:2606-2614. [PMID: 30724558 DOI: 10.1021/acsnano.8b09667] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this article, we describe the quantitative characterization of a gold nanoneedle ion channel probe and demonstrate the utility of this probe for spatially resolved detection of a small molecule using ion channel activity. Our report builds on recent reports of Ide and co-workers, who reported the use of an etched gold wire modified with a poly(ethylene) glycol monolayer as a support for a lipid bilayer and subsequent single ion channel recordings. Although this nanoneedle electrode approach was reported previously, in our report, we investigate the effects of several operational parameters on the performance of the ion channel measurement and electrochemical phenomenon that occur in the nanoconfined space between the supported bilayer and the gold electrode. More specifically, we address the effects of length of the supporting monolayer and the composition of the electrolyte baths on channel current measurements and provide a quantitative description of what carries current at the working electrode (double-layer charging). In addition, we demonstrate the ability to control the direction of protein insertion (tip side vs bath side) with freely diffusing protein, which has not been previously reported, with the former method (tip side) enabling single-molecule detection of β-cyclodextrin (βCD) using a reconstituted α-hemolysin channel. Finally, anticipating future use of a nanoneedle-based biological nanopore probe in a scanned-probe microscopy, we demonstrate the ability to quantify and spatially resolve the concentration of βCD molecules in a microfluidic channel. We believe, in the long term, the described nanoneedle-based biological nanopore probe can be employed in, for example, scanning ion conductance microscopy using ion channels.
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Affiliation(s)
- Kan Shoji
- Department of Biotechnology and Life Science , Tokyo University of Agriculture and Technology , 2-24-16 Naka-cho , Koganei-shi , Tokyo 184-8588 , Japan
| | - Ryuji Kawano
- Department of Biotechnology and Life Science , Tokyo University of Agriculture and Technology , 2-24-16 Naka-cho , Koganei-shi , Tokyo 184-8588 , Japan
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