Characterization of Stimulus Responsive Elastin-like-Polymer Biosensor Using Electrochemical Impedance Spectroscopy

Marissa A. Morales¹, Eva Rose M. Balog², and Jeffery Mark Halpern¹

¹Department of Chemical Engineering – University of New Hampshire – Durham, New Hampshire

²Department of Chemistry and Physics - University of New England – Biddeford, Maine

Elastin-like-polymers (ELP) are a class of proteins that undergo an inverse phase transition where above the transition temperature the protein is soluble and below the transition temperature the protein is an insoluble aggregation form. The aggregation response of ELP can be controlled by protein composition and environmental stimuli. The ELP primary amino acid sequence is comprised of a pentapeptide repeat [VPGXG] (V = valine, P = proline, G = glycine, and X = guest residue). The hydrophobicity of the ELP can affect the transition response; the hydrophobic surface area of the ELP is determined via guest amino acid residue selection, as well as the overall number and pattern of pentapeptide repeat sequences [1]. Environmental stimuli that affect transition temperature include pH, ionic strength, and temperature [2]. This multidimensional control of the stimuli responsive behavior makes ELP interesting for multiple biomedical applications.

The stimulus responsive behavior of ELPs is used extensively in the field of drug delivery for targeted drug release resulting from the conformational change of ELP in response to environment factors [2]. Instead, we propose to use the stimulus responsive dynamic bioanalyte sensor that can take advantage of ELP’s conformational change. This biosensor will be comprised of an ELP functionalized surface that can switch between two distinct states: (1) the extended state with the ELP extended in a brush like array from the sensor surface and (2) the collapsed state where the protein has fallen upon the sensor surface forming a protein aggregate layer.

Surface functionalization will be achieved via thiol chemistry using a well characterized thiol-gold interaction. The extended versus collapsed surface states will be evaluated using electrochemical impedance spectroscopy (EIS) to quantify the resistance to electron flow, impedance, when an alternating voltage potential is applied. We hypothesize that the collapsed state will result in a higher impedance compared to the extended state because the protein aggregate layer formed on the sensor surface will restrict the flow of electrons to the sensor surface compared to the extended state. We will report on our progress on the development of this sensor.

The authors would like to acknowledge NSF EAGER (CBET 1638896) for the funding of this work.

References

[1] R. Herrero-Vanrell, A. C. Rincon, M. Alonso, I. T. Molina-Martinez, and J. C. Rodriguez-Cabello, “Self-assembled particles of an elastin-like polymer as vehicles for controlled drug release,” J. Control. Release, vol. 102, no. 1, pp. 113–112, 2005.

[2] D. Schmaljohann, “Thermo- and pH-responsive polymers in drug delivery,” Adv. Drug Deliv. Rev., vol. 58, no. 15, pp. 1655–1670, 2006.