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Shen Y, Zhong Y, Fei F, Sun J, Czajkowsky DM, Gong B, Shao Z. Ultrasensitive liposome-based assay for the quantification of fundamental ion channel properties. Anal Chim Acta 2020; 1112:8-15. [PMID: 32334685 DOI: 10.1016/j.aca.2020.03.044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 02/16/2020] [Accepted: 03/22/2020] [Indexed: 10/24/2022]
Abstract
One of the most widely used approaches to characterize transmembrane ion transport through nanoscale synthetic or biological channels is a straightforward, liposome-based assay that monitors changes in ionic flux across the vesicle membrane using pH- or ion-sensitive dyes. However, failure to account for the precise experimental conditions, in particular the complete ionic composition on either side of the membrane and the inherent permeability of ions through the lipid bilayer itself, can prevent quantifications and lead to fundamentally incorrect conclusions. Here we present a quantitative model for this assay based on the Goldman-Hodgkin-Katz flux theory, which enables accurate measurements and identification of optimal conditions for the determination of ion channel permeability and selectivity. Based on our model, the detection sensitivity of channel permeability is improved by two orders of magnitude over the commonly used experimental conditions. Further, rather than obtaining qualitative preferences of ion selectivity as is typical, we determine quantitative values of these parameters under rigorously controlled conditions even when the experimental results would otherwise imply (without our model) incorrect behavior. We anticipate that this simply employed ultrasensitive assay will find wide application in the quantitative characterization of synthetic or biological ion channels.
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Affiliation(s)
- Yi Shen
- Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yulong Zhong
- Department of Chemistry, The State University of New York at Buffalo, Buffalo, NY, 14260, United States
| | - Fan Fei
- Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jielin Sun
- Shanghai Center for Systems Biomedicine, Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Daniel M Czajkowsky
- Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Bing Gong
- Department of Chemistry, The State University of New York at Buffalo, Buffalo, NY, 14260, United States.
| | - Zhifeng Shao
- Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
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Zhang S, Kieffer SJ, Zhang C, Alleyne AG, Braun PV. Directed Molecular Collection by E-Jet Printed Microscale Chemical Potential Wells in Hydrogel Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1803140. [PMID: 30073702 DOI: 10.1002/adma.201803140] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 07/05/2018] [Indexed: 06/08/2023]
Abstract
A facile approach to locally concentrate analytes of interest will significantly enhance miniaturized, integrated chemical-analysis systems. Here, the directed analyte transport and concentration using ≈200 µm-diameter E-jet printed chemical potential wells in a polyacrylamide hydrogel is demonstrated. Using a cationic well as the model system, anionic analytes are accumulated into a microscale area with a local concentration enhancement of >50-fold relative to the surrounding area. By downscaling the diameter of the chemical potential well from a few millimeters to 100s of micrometers, it is found, using both fluorescence and Raman microscopy, that the molecular collection capacity of the well is greatly improved. Additionally, it is shown that molecules can be simultaneously transported and concentrated to arrays of microscale regions using an array of microscale chemical potential wells. This approach enhances many-fold the limit of detection, enables the formation of microscale potential well arrays with a variety of chemical properties, and provides a novel microscale molecular manipulation technique as an alternative to traditional microfluidic-based systems.
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Affiliation(s)
- Shiyan Zhang
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Spencer J Kieffer
- Department of Mechanical Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Chunjie Zhang
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Andrew G Alleyne
- Department of Mechanical Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Paul V Braun
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
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Waynant KV, Koo HJ, Zhang C, Braun PV. Qualitative degradation of the pesticide coumaphos in solution, controlled aerosol, and solid phases on quaternary ammonium fluoride polymer brushes. POLYM ADVAN TECHNOL 2017. [DOI: 10.1002/pat.3861] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Kristopher V. Waynant
- Department of Chemistry; University of Idaho; Moscow ID 83844 USA
- Department of Materials Science and Engineering and Beckman Institute; University of Illinois Urbana-Champaign; Urbana IL 61801 USA
| | - Hyung-Jun Koo
- Department of Materials Science and Engineering and Beckman Institute; University of Illinois Urbana-Champaign; Urbana IL 61801 USA
- Department of Chemical and Biomolecular Engineering; Seoul National University of Science and Technology; 232 Gongneung-ro Nowon-gu Seoul 139-743 Korea
| | - Chunjie Zhang
- Department of Materials Science and Engineering and Beckman Institute; University of Illinois Urbana-Champaign; Urbana IL 61801 USA
- 3M Company; 3M Center St. Paul MN 55144 USA
| | - Paul V. Braun
- Department of Materials Science and Engineering and Beckman Institute; University of Illinois Urbana-Champaign; Urbana IL 61801 USA
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Mohammadi Sejoubsari R, Martinez AP, Kutes Y, Wang Z, Dobrynin AV, Adamson DH. “Grafting-Through”: Growing Polymer Brushes by Supplying Monomers through the Surface. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b00183] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
| | | | | | - Zilu Wang
- Department
of Polymer Science, University of Akron, Akron, Ohio 44304, United States
| | - Andrey V. Dobrynin
- Department
of Polymer Science, University of Akron, Akron, Ohio 44304, United States
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Koo HJ, Waynant KV, Zhang C, Braun PV. Polymer brushes patterned with micrometer-scale chemical gradients using laminar co-flow. ACS APPLIED MATERIALS & INTERFACES 2014; 6:14320-14326. [PMID: 24960623 DOI: 10.1021/am503609x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present a facile microfluidic method for forming narrow chemical gradients in polymer brushes. Co-flow of an alkylating agent solution and a neat solvent in a microfluidic channel forms a diffusion-driven concentration gradient, and thus a gradient in reaction rate at the interface of the two flows, leading to a quaternization gradient in the underlying poly(2-(dimethylamino)ethyl methacrylate) polymer brush. The spatial distribution of the quaternized polymer brush is characterized by confocal Raman microscopy. The quaternization gradient length in the polymer brush can be varied with the injection flow rate and the distance from the co-flow junction. A chemical gradient in the polymer brush as narrow as 5 μm was created by controlling these parameters. The chemical gradient by laminar co-flow is compared with numerical calculations that include only one adjustable parameter: the reaction rate constant of the polymer brush quaternization. The calculated chemical gradient agrees with the experimental data, which validates the numerical procedures established in this study. Flow of multiple laminar streams of reactive agent solutions enables single-run fabrication of brush gradients with more than one chemical property. As one example, four laminar streams-neat solvent/benzyl bromide solution/propargyl bromide solution/neat solvent-generate multistep gradients of aromatic and alkyne groups. Because the alkyne functional group is a click-reaction available site, the alkyne gradient could allow small gradient formation with a wide variety of chemical properties in a polymer brush.
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Affiliation(s)
- Hyung-Jun Koo
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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