Characterizing the Source of Inconsistent Modification of ELP By Cyclic Voltammetry

Abstract

Elastin-like polymers (ELPs) have gained attention recently for their potential as biorecognition element platforms for biosensors. For surface-bound ELP to be used as a biorecognition platform, consistent surface modification is required to ensure a consistent electrochemical response model. Consistent electrochemical response of gold surfaces with ELP has been a challenge in practice, but can be achieved with careful modification procedure, keeping variables such as temperature, ELP concentration, time of modification, and dissolution procedure consistent. We hypothesize that further ELP surface modification inconsistencies are due to ELP that physiosorbs to the gold surface and other surface-bound ELP. This presentation will share data demonstrating that inconsistencies in electrochemical measurements of surface-bound ELP are due to inconsistent physisorption of non-chemisorbed ELP molecules. Cyclic voltammetry in KOH was applied to surface-bound ELP at different ELP concentrations in order to reduce the ELP - gold thiol surface. This reduction corresponds to a peak in the cyclic voltammogram. The area under this peak is equal to the charge exchanged for the reduction of the thiol bond, which correlates to the amount of ELP removed from the gold surface. Additionally, electrochemical impedance spectroscopy (EIS) was used with a Randles circuit model to determine the charge transfer resistance of the surfaces. By comparing the trend of charge transfer resistance to modification concentration and chemisorbed ELP, we show that the inconsistencies in charge transfer measurements are related to physiosorbed ELP and not chemisorbed ELP. Acknowledgements: The authors would like to acknowledge the financial support from NSF (CBET 1638896) and the Collaborative Research Excellence Initiative Pilot Research Program at the University of New Hampshire. The authors also would like to acknowledge the assistance of Dr. Balog’s laboratory and Dr. Halpern’s laboratory.