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Protein nanolayers(PNLs) formed at an electrochemical liquid|liquid interface between water (W) and a fluorous solvent (F) were examined by using interfacial rheological measurement (IRM) and neutron reflectometry (NR) under the externally controlled condition of the phase boundary potential differences EF W(=φW−φF + const.), where F contained a hydrophobic ionic liquid (IL) as a supporting electrolyte and W, whose pH was 7.4, contained a protein, bovine serum albumin (BSA).The IRM and NR results illuminated that both static and dynamic properties of the PNL at the electrochemical F|W interface were varied by applying EF W. NR found minimal EF W dependence on the adsorption amount of BSA in the PNL. In contrast, IRM revealed that although the interfacial shear loss moduli G″ of the PNL was constant regardless of EF W, the interfacial shear storage G′ of the PNL increased dramatically at more negative EF W, showing a more elastic response.This difference between static and dynamic properties results from the increase in intermolecular and intramolecular interactions between BSA molecules in the PNL at more negative EF W due to the accelerated denaturation of negatively charged BSA that formed complexes with IL cations accumulated on the F side of the F|W interface. The G′ and G″ reversibly responded to switching between different potentials (a positive and a negative EF W).These IRM results unveiled that the viscoelasticity of the PNL at the electrochemical F|W interface is reversibly potential-switchable.The present interface-specific method using the potential control is a new promising method to diversify and switch the PNL structure reversibly. The reversible structural control of the PNL would enable us to perform real-time observation of cells reacting to environmental changes at liquid|liquid interfaces.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: ionic liquid, interface, electrochemistry, viscoelasticity, cell, mechanobiology

Date published: 2025-07-15

Publisher: American Chemical Society (ACS)

Journal:

• Langmuir (ISSN: 07437463) vol. 41 issue. 27 p. 17973-17981

Funding:

• Japan Society for the Promotion of Science 23H02030
• Japan Society for the Promotion of Science 23H03829

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1021/acs.langmuir.5c01819

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Updated at: 2025-09-02 16:30:27 +0900

Published on MDR: 2025-09-02 16:19:01 +0900