Troubleshooting the Process of Creating an Electrochemically Active Elastin‐Like Polymer

Abstract

Elastin‐like polymers (ELPs) are stimuli‐responsive polymers similar to vertebrate elastin. ELPs undergo a characteristic elongation‐collapse transition that can be induced by various external stimuli, such as pH, ionic strength, and temperature. The ELP elongation‐collapse transition has yet to be monitored electrochemically. Our work has focused on how to best analyze the ELP elongation‐collapse transition using electrochemistry, which, to the best of our knowledge, has never been done. If successful, we could then use ELP as a stimuli‐responsive biorecognition element in point‐of‐care electrochemical biosensors.Initially, our work focused on a bio‐conjugation of ferrocene‐NHS ester to our ELP, because our ELP is not electrochemically active. Since ferrocene‐NHS ester has an active □COOH reactive group, it was theorized that this group would interact with lysine residues present in our ELP construct. Due to issues with solubility, we were unable to successfully purify our conjugated polymer. With solubility issues preventing our ability to create an electrochemically active ELP, we transitioned into the use of electrochemical impendence spectroscopy, EIS, to analyze the ELP collapse onto an Au‐coated quartz crystal surface.Prior to EIS experiments, a self‐assembled monolayer of our ELP was created. We used an ELP construct with a cysteine residue which has the capacity to form a thiol bond with the Au‐coated surface. While there was some success to achieving a self‐assembled monolayer, we did not reach uniformity in our coverage; however, we did preliminary EIS experiments on our ELP surfaces.EIS uses a solution of ferri‐ferrocyanide, Fe2+/Fe3+, for the electron transfer necessary for electrochemical analysis to determine surface coverage. Specifically, EIS determines the amount of molecules present on a surface based on the charge transfer resistance, RCT, or the ability of the electrons to transfer between Fe2+/Fe3+. As the ELP undergo an elongation‐collapse transition, the collapsed ELP on the surface is expected to have a higher RCT, because the electrons cannot as easily interact with the electrode surface. As temperature increases, ELPs undergo a transition from their elongated to collapsed state and are expected to collapse onto the Au surface. The monitored RCT decrease may be caused by an increase in electron movement from warmer temperatures or from a deficit of uniform ELP coverage. From this, we conclude that the temperature effects on EIS had a stronger influence on the RCT compared to the collapsed of ELP.While no concrete conclusions have been produced about the electrochemical nature of ELPs' transition state, this is the preliminary work that forms the basis for future experiments.Support or Funding InformationThe authors would like to also thank Balog's Laboratory and Halpern's Surface Enhanced Electrochemical Diagnostics Sensors (SEEDS) Laboratory for their support and assistance. The authors would like to thank the following funding sources:Hamel Center of Undergraduate Research, College of Engineering and Physical Sciences at University of New Hampshire, and NSF EAGER (CBET 1638896)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.