R-001

Aušra Valiūnienė1,2

ausra.valiuniene@ftmc.lt

Gerda Ziziunaite1, Anastasija Aleksandrovič1, Narvydas Dėnas1,2, Gintaras Valincius3

1Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Lithuania

2Center for Physical Sciences and Technology (FTMC), Vilnius, Lithuania

3Unaffiliated scientist, Lithuania

Electrochemical impedance spectroscopy as a tool to study the structural properties of tethered bilayer lipid membranes

Keywords: electrochemical impedance spectroscopy; biosensors; tethered bilayer lipid membrane; α-hemolysin.

Tethered bilayer membranes (tBLMs) can be considered as the most perfect models of biological membranes due to their superior integrity and the possibility to implement tBLM sensors as solid-state chips with a direct electrical read-out of the biological signal. With a good membrane model, it is possible to develop biosensors for the detection of a wide range of membrane-destroying or pore-forming toxins. tBLMs-based sensors contain dielectric layers that, when disrupted, cause significant changes in the signals recorded by electrochemical methods, such as electrochemical impedance spectroscopy (EIS).

The aim of our study was to compare the EIS responses of two different types of tBLMs constructed on Au and FTO substrates, and to determine the sensitivity of these tBLMs to the toxin alpha-hemolysin, in order to enable the intelligent design of biomimetic devices such as tBLM-based biosensors.

The EIS spectra of the tBLMs cannot be fitted with sufficient quality to a conventional equivalent circuit model with resistors and capacitors, because the physical meaning of CPEs with exponents significantly different from 1 (which is typically the case, [2]) is vague, and little specific physical information about the function and/or structure of tBLMs can be derived from such fit. In view of this, we fitted the EIS spectra of tBLMs using a recently developed theoretical framework [3] based on the concept of random or clustered distribution of membrane defects at the nanoscale, which accurately reproduced the shape of the EIS curves of tBLMs and showed that the EIS response and the sensitivity to the toxin alpha-hemolysin were stronger for tBLMs on FTO than on Au. 

Our study demonstrates that EIS, traditionally considered as a method for measuring electrical parameters, can be used to detect changes in the structure and physical properties of tBLM at the molecular level. Importantly, these changes occur at extremely thin, 1-2 nm thick submembrane water-containing reservoir that separates the solid support and the phospholipid bilayer. 

References:

1. Boukamp, B.A., 1986. Solid state ionics 20, 31–44.

2. McGillivray, D.J., Valincius, G., at al., 2007. Biointerphases 2, 21–33. 

3. Ambrulevičius, F., Valinčius, G., 2022. Bioelectrochemistry 146, 108092.