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Certain Methods of Electrode Pretreatment Create Misleading Responses in Impedimetric Aptamer Biosensors
journal contribution
posted on 2019-03-26, 08:13 authored by Lance
St. John Ho, Janice L. Limson, Ronen FogelDespite the widespread
knowledge of the influence that electrode
pretreatments have on electroanalysis, pretreatments of gold electrodes
for impedimetric aptasensors remain study-specific. This may be a
neglected reason behind the limited consensus in reports focusing
on creation and testing of aptasensors. To investigate this, several
commonly reported pretreatments were applied to gold electrodes that
were subsequently used to fabricate thrombin-specific impedimetric
aptasensors, which are widely reported in the literature. Layer-by-layer
electrochemical impedance spectroscopy analyses were conducted to
determine the effect the pretreatment selection has on impedimetric
responses during fabrication and testing of the aptasensor. Pretreatments
were evaluated using factors crucial for biosensor deployment: the
repeatability of interelectrode measurements and whether biosensors
produced statistically significant responses when exposed to 2 μM
thrombin. Individual pretreatments were found to impart unique physicochemical
properties to electrode surfaces, indicated by variations in measured
capacitances (impedimetry) and electrode surface topographies (scanning
electron microscopy). Impedimetrically measured resistivity (Rtotal) of electrodes increased during layering
of the biosensor across all the investigated pretreatments: from 852
± 830 Ω (bare electrodes) to 3117 ± 1199 Ω (fabricated
aptasensors exposed to thrombin), consistent with prior literature.
Crucially, the magnitude and reproducibility of Rtotal values measured during fabrication and testing of
the assembled aptasensor were strongly contingent on the pretreatment.
Depending on the pretreatment, interelectrode sensor responses exhibited
relative standard deviations between 38 and 150%. These findings propose
that the choice of gold-surface pretreatment protocols is an overlookedyet
crucialfactor to consider when developing analytically valid
impedimetric aptasensors.
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Keywords
gold-surface pretreatment protocolsthrombin-specific impedimetric aptasensorselectrode surface topographiesImpedimetric Aptamer Biosensorsimpedimetric aptasensors2 μ M thrombininterelectrode sensor responsesLayer-by-layer electrochemical impedance spectroscopy analysesgold electrodesscanning electron microscopy
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