Abstract
The thickness shear mode acoustic wave device is of interest for the sensing of biomarkers for diseases in various biological fluids, but suffers from the issue of non-specific adsorption of compounds other than those of interest to the electrode surface, thus affecting the device’s output. The aim of this present study was to determine the level of non-specific adsorption on gold electrodes from serum samples with added ovarian cancer biomarker lysophosphatidic acid in the presence of a surface anti-fouling layer. The latter was an oligoethylene molecule with thiol group for attachment to the electrode surface. It was found that the anti-fouling layer had a minimal effect on the level of both adsorption of components from serum and the marker. This result stands in sharp contrast to the analogous monolayer employed for anti-fouling reduction on silica.
Highlights
Lysophosphatidic Acid in SerumThe thickness shear mode (TSM) acoustic wave biosensor, sometimes referred to as a “quartz crystal microbalance”, is typically composed of a pair of gold electrodes placed on both sides of a thin disc of piezoelectric quartz
Individual experimental responses in TSM frequency and motional resistance over time can be found in the Supporting Information (Figures S1–S8)
The frequency drop was lowest when there was no serum present, there was statistically minimal change in the frequency drop between 10% and 50% serum when lysophosphatidic acid (LPA) was present, which suggests that the amount of material deposited onto the device is invariable over this concentration range
Summary
The thickness shear mode (TSM) acoustic wave biosensor, sometimes referred to as a “quartz crystal microbalance”, is typically composed of a pair of gold electrodes placed on both sides of a thin disc of piezoelectric quartz. Sensing can be achieved by binding a probe molecule to the surface of the gold substrate, which binds selectively to the analyte of interest, causing a measurable change in vibrational frequency and motional resistance. Due to the complex nature of bio fluids, non-specific adsorption or fouling of compounds on the electrode surface, other than those of interest, renders these devices difficult to use in these fluids [3]. A vast literature describes the many attempts that have been made to avoid the fouling of surfaces by components of biological fluids [6]; this includes gold as a substrate
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