Microband sensor for As(III) analysis: Reduced matrix interference

A portable sensor based on a microband design for arsenic detection in drinking water is presented. The work was focused to minimize interference encountered with a standard screen-printed electrodes featuring an onboard gold working electrode, carbon counter and silver−silver chloride pseudo-reference electrodes as composite coatings on plastic surface. The interference effect was identified as chloride ions interacting with the silver surface of the reference electrode and formation of soluble silver chloride complexes such as AgCl43−. By modification of the reference electrodes with Nafion membrane (5 % in alcohols), the interference was entirely eliminated. However, membrane coverage and uniformity can impact the electrodes reproducibility and performance. Hence, the sensor design was further considered and a microband format was produced lending favorable diffusive to capacitive current characteristics. Using the microband electrodes allowed As(III) detection with limit of detection of 0.8 ppb (in 4 M HCl electrolyte), inherently avoiding the problems of electrode fouling and maximizing analyte signal in river water samples. This is below the World Health Organization limit of 10 μg L−1 (ppb). The electrolyte system was chosen so as to avoid problems from other common metal ions, most notably Cu(II). The presented electrode system is cost effective and offers a viable alternative to the colorimetric test kits presently employed for arsenic analysis in drinking water

The Development of a Sub-Surface Monitoring System for Organic Contamination in Soils and Groundwater

A major problem when dealing with environmental contamination is the early detection and subsequent surveillance of the contamination. This paper describes the potential of sub-surface sensor technology for the early detection of organic contaminants in contaminated soils, sediments, and landfill sites. Rugged, low-power hydrocarbon sensors have been developed, along with a data-logging system, for the early detection of phase hydrocarbons in soil. Through laboratory-based evaluation, the ability of this system to monitor organic contamination in water-based systems is being evaluated. When used in conjunction with specific immunoassays, this can provide a sensitive and low-cost solution for long-term monitoring and analysis, applicable to a wide range of field applications

An electrochemical SARS-CoV-2 biosensor inspired by glucose test strip manufacturing processes

Accurate and rapid diagnostic tests are critical to reducing the impact of SARS-CoV-2. This study presents early, but promising measurements of SARS-CoV-2 using the ACE2 enzyme as the recognition element to achieve clinically relevant detection. The test provides a scalable route to sensitive, specific, rapid and low cost mass testing

SARS-CoV-2 aptasensors based on electrochemical impedance spectroscopy and low-cost gold electrode substrates

SARS-CoV-2 diagnostic practices broadly involve either quantitative polymerase chain reaction (qPCR)-based nucleic amplification of viral sequences or antigen-based tests such as lateral flow assays (LFAs). Reverse transcriptase-qPCR can detect viral RNA and is the gold standard for sensitivity. However, the technique is time-consuming and requires expensive laboratory infrastructure and trained staff. LFAs are lower in cost and near real time, and because they are antigen-based, they have the potential to provide a more accurate indication of a disease state. However, LFAs are reported to have low real-world sensitivity and in most cases are only qualitative. Here, an antigen-based electrochemical aptamer sensor is presented, which has the potential to address some of these shortfalls. An aptamer, raised to the SARS-CoV-2 spike protein, was immobilized on a low-cost gold-coated polyester substrate adapted from the blood glucose testing industry. Clinically relevant detection levels for SARS-CoV-2 are achieved in a simple, label-free measurement format using sample incubation times as short as 15 min on nasopharyngeal swab samples. This assay can readily be optimized for mass manufacture and is compatible with a low-cost meter

Field—Based Supercritical Fluid Extraction of Hydrocarbons at Industrially Contaminated Sites

Examination of organic pollutants in groundwaters should also consider the source of the pollution, which is often a solid matrix such as soil, landfill waste, or sediment. This premise should be viewed alongside the growing trend towards field-based characterisation of contaminated sites for reasons of speed and cost. Field-based methods for the extraction of organic compounds from solid samples are generally cumbersome, time consuming, or inefficient. This paper describes the development of a field-based supercritical fluid extraction (SFE) system for the recovery of organic contaminants (benzene, toluene, ethylbenzene, and xylene and polynuclear aromatic hydrocarbons) from soils. A simple, compact, and robust SFE system has been constructed and was found to offer the same extraction efficiency as a well-established laboratory SFE system. Extraction optimisation was statistically evaluated using a factorial analysis procedure. Under optimised conditions, the device yielded recovery efficiencies of >70% with RSD values of 4% against the standard EPA Soxhlet method, compared with a mean recovery efficiency of 48% for a commercially available field-extraction kit. The device will next be evaluated with real samples prior to field deployment

An uncomplicated electrochemical sensor combining a perfluorocarbon SAM and ACE2 as the bio-recognition element to sensitively and specifically detect SARS-CoV-2 in complex samples.

Emerging in late 2019, the SARS-CoV-2 virus has had a devastating health and economic effects around the world forcing governments to enact restrictions on day to day life, resulting in severe economic and social disruption. The virus has stimulated new research in the fields of drug development, vaccinology and diagnostic testing. Here we present the basis for a simple, mass manufacturable saliva based electrochemical assay for the SARS-CoV-2 virus acheived through adsorption of the Angiotsnsin Converting Enzyme 2 (ACE2) into thiolated amphiphobic prefluoro monolayer assemled on a gold sensor surface. Following sensor preparation, it is possible to measure specific binding of recombinant spike protein and discriminate positive and negative samples of inactivated SARS-CoV-2 following 30 minutes incubation under ambient conditions. Representative calculations of limits of detection are made for recombinant spike protein (1.68 ng/ml) and inactivated virus (37.8 dC/mL). The assay as presented ultimately shows discrimination between positive and negative inactivated SARS-CoV-2 samples originating from clinical molecular standards kit intended for clinical and biomedical assay validation, and which is designed to mimic clinical samples through presence of cells and proteins in the sample medium. The simple design of the label free measurement and the selection of reagents involved means the assay has clear potential for transfer onto mass producible units such as screen-printed electrodes similar to glucose-format test strips, to enable widespread, low cost and rapid testing for SARS-CoV-2 in the general populatio

A SARS-CoV-2 aptasensor based on electrochemical impedance spectroscopy and low-cost gold electrode substrates.

SARS-CoV-2 diagnostic practices broadly involve either qPCR based nucleic amplification or lateral flow assays (LFAs). qPCR based techniques suffer from the disadvantage of requiring thermal cycling (difficult to implement for low-cost field use) leading to limitation on sample to answer time, the potential to amplify viral RNA sequences after a person is no longer infectious and being reagent intense. LFA performance is restricted by qualitative or semi-quantitative readouts, limits on sensitivity and poor reproducibility. Electrochemical biosensors, and particularly glucose test strips, present an appealing platform for development of biosensing solutions for SARS-CoV-2 as they can be multiplexed and implemented at very low cost at point of use with high sensitivity and quantitative digital readout. This work reports the successful raising of an Opti-mer sequence for the spike protein of SARS-CoV-2 and then development of an impedimetric biosensor which utilises thin film gold sensors on low-cost laminate substrates from home blood glucose monitoring. Clinically relevant detection levels for SARS-CoV-2 are achieved in a simple, label-free measurement format using sample incubation times of 15 minutes. The biosensor developed here is compatible with mass manufacture, is sensitive and low-cost CE marked readout instruments already exist. These findings pave the way to a low cost and mass manufacturable test with the potential to overcome the limitations associated with current technologies