Previous investigation of elastin-like polymer (ELP) modified surfaces showed successful modification followed by a reversible extension and collapse, as measured by electrochemical impedance spectroscopy (EIS). This work indicated successful modification of an electrode with ELP corresponds with a charge transfer resistance of 10-20 kOhms in 10 mM ferri/ferrocyanide (FFC).1 The EIS charge transfer resistance value can be seen to increase with a stimulus predicted to cause ELP collapse and then decrease again with a re-extension of the ELP. We investigated the effects of the FFC concentration and other solution conditions on the interpretation of EIS signals in monitoring ELP response.
For these experiments, ELP was attached to the surface of a gold electrode by binding a cysteine thiol from the ELP to the gold surface in the presence of the reducing agent TCEP. This was followed by EIS experiments to measure the electrochemical impedance of the same ELP-modified surface under three different electrochemical mediator conditions: (1) 5 mM FFC in water, (2) 10 mM FFC in water, and (3) 5 mM FFC in 0.5 M KCl aqueous solution. Before the exchange of electrochemical mediator, the electrode was washed. We observed an increased charge transfer resistance in the presence of 5 mM FFC and a decrease in charge transfer resistance in the presence of 5 mM FFC 0.5 M KCl relative to experiments performed in 10 mM FFC. We predict that the type of electrochemical mediator and supporting electrolyte used in conjunction with ELP modified surfaces will impact the interpretation of data. We will present our progress on the interpretation of ELP-modified surfaces using different electrochemical mediator concentrations, and what we learned from these results.
Acknowledgments: This work was supported by NIH P20 GM113131
References
M. A. Morales, W. A. Paiva, L. Marvin, E. R. M. Balog, and J. M. Halpern, Soft Matter, 15, 9640–9646 (2019).
