Continuous Square Wave Voltammetry for High Information Content Interrogation of Conformation Switching Sensors

Square wave voltammetry
(SWV) is a voltammetric technique for measuring
Faradaic current while minimizing contributions from non-Faradaic
processes. In square wave voltammetry, the potential waveform applied
to a working electrode and the current sampling protocols followed
are designed to minimize contributions from non-Faradaic processes
(i.e., double layer charging) to improve voltammetric sensitivity.
To achieve this, the current is measured at the end of each forward
and reverse potential pulse after allowing time for non-Faradaic currents
to decay exponentially. A consequence of sampling current at the end
of a potential pulse is that the current data from the preceding time
of the potential pulse are discarded. These discarded data can provide
information about the non-Faradaic contributions as well as information
about the redox system including charge transfer rates. In this paper,
we introduce continuous square wave voltammetry (cSWV), which utilizes
the continuous collection of current to maximize the information content
obtainable from a single voltammetry sweep eliminating the need for
multiple scans. cSWV enables acquiring a multitude of voltammograms
corresponding to various frequencies and, thus, different scan rates
from a single sweep. An application that benefits significantly from
cSWV is conformation switching, functional nucleic acid sensors. We
demonstrate the utility of cSWV on two representative small molecules
targeting electrochemical, aptamer-based sensors. Moreover, we show
that cSWV provides comparable results to those obtained from traditional
square wave voltammetry, but with cSWV, we are able to acquire dynamic
information about the sensor surfaces enabling rapid calibration and
optimization of sensing performance. We also demonstrate cSWV on soluble
redox markers. cSWV can potentially become a mainstay technique in
the field of conformation switching sensors.