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Limaye A, Suvlu D, Willard AP. Water molecules mute the dependence of the double-layer potential profile on ionic strength. Faraday Discuss 2024; 249:267-288. [PMID: 37830233 DOI: 10.1039/d3fd00114h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
We present the results of molecular dynamics simulations of a nanoscale electrochemical cell. The simulations include an aqueous electrolyte solution with varying ionic strength (i.e., concentrations ranging from 0-4 M) between a pair of metallic electrodes held at constant potential difference. We analyze these simulations by computing the electrostatic potential profile of the electric double-layer region and find it to be nearly independent of ionic concentration, in stark contrast to the predictions of standard continuum-based theories. We attribute this lack of concentration dependence to the molecular influences of water molecules at the electrode-solution interface. These influences include the molecular manifestation of water's dielectric response, which tends to drown out the comparatively weak screening requirement of the ions. To support our analysis, we decompose water's interfacial response into three primary contributions: molecular layering, intrinsic (zero-field) orientational polarization, and the dipolar dielectric response.
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Affiliation(s)
- Aditya Limaye
- Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
| | - Dylan Suvlu
- Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
| | - Adam P Willard
- Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
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2
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Cell Surface Charge Mapping Using a Microelectrode Array on ITO Substrate. Cells 2023; 12:cells12040518. [PMID: 36831185 PMCID: PMC9954061 DOI: 10.3390/cells12040518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/26/2023] [Accepted: 02/02/2023] [Indexed: 02/09/2023] Open
Abstract
Many cellular functions are regulated by cell surface charges, such as intercellular signaling and metabolism. Noninvasive measurement of surface charge distribution of a single cell plays a vital role in understanding cellular functions via cell membranes. We report a method for cell surface charge mapping via photoelectric interactions. A cell is placed on an array of microelectrodes fabricated on a transparent ITO (indium tin oxide) surface. An incident light irradiates the ITO surface from the backside. Because of the influence of the cell surface charge (or zeta potential), the photocurrent and the absorption of the incident light are changed, inducing a magnitude change of the reflected light. Hence, the cell surface charge distribution can be quantified by analyzing the reflected light intensity. This method does not need physical or chemical modification of the cell surface. We validated this method using charged microparticles (MPs) and two types of cells, i.e., human dermal fibroblast cells (HDFs) and human mesenchymal stem cells (hMSC). The measured average zeta potentials were in good agreement with the standard electrophoresis light scattering method.
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Xu X, Valavanis D, Ciocci P, Confederat S, Marcuccio F, Lemineur JF, Actis P, Kanoufi F, Unwin PR. The New Era of High-Throughput Nanoelectrochemistry. Anal Chem 2023; 95:319-356. [PMID: 36625121 PMCID: PMC9835065 DOI: 10.1021/acs.analchem.2c05105] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Xiangdong Xu
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | | | - Paolo Ciocci
- Université
Paris Cité, ITODYS, CNRS, F-75013 Paris, France
| | - Samuel Confederat
- School
of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.,Bragg
Centre for Materials Research, University
of Leeds, Leeds LS2 9JT, U.K.
| | - Fabio Marcuccio
- School
of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.,Bragg
Centre for Materials Research, University
of Leeds, Leeds LS2 9JT, U.K.,Faculty
of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | | | - Paolo Actis
- School
of Electronic and Electrical Engineering and Pollard Institute, University of Leeds, Leeds LS2 9JT, U.K.,Bragg
Centre for Materials Research, University
of Leeds, Leeds LS2 9JT, U.K.,
| | | | - Patrick R. Unwin
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.,
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Atomic force and infrared spectroscopic studies on the role of surface charge for the anti-biofouling properties of polydopamine films. Anal Bioanal Chem 2022; 415:2059-2070. [PMID: 36434170 PMCID: PMC10079710 DOI: 10.1007/s00216-022-04431-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 10/27/2022] [Accepted: 11/08/2022] [Indexed: 11/26/2022]
Abstract
Antibacterial polymer materials have gained interest due to their capability to inhibit or eradicate biofilms with greater efficiency in comparison with their monomeric counterparts. Among the antimicrobial and anti-biofouling polymers, catecholamine-based polymers - and in particular polydopamine - have been studied due to their favorable adhesion properties, which can be tuned by controlling the pH value. In this study, we used atomic force microscopy (AFM)-based spectroscopy to investigate the relation between the adhesion properties and surface charge density and the pH of electrochemically deposited polydopamine films presenting a dissociation constant of polydopamine of 6.3 ± 0.2 and a point of zero charge of 5.37 ± 0.06. Furthermore, using AFM and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), the influence of the surface charge density of polydopamine on bacterial adhesion and biofilm formation was investigated. It was shown that the adhesion of Escherichia coli at positively charged polydopamine is three times higher compared to a negatively charged polymer, and that the formation of biofilms is favored at positively charged polymers.
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