Wide-range and selective detection of SARS-CoV-2 DNA via surface modification of electrolyte-gated IGZO thin-film transistors.

The 2019 coronavirus pandemic resulted in a massive global healthcare crisis, highlighting the necessity to develop effective and reproducible platforms capable of rapidly and accurately detecting SARS-CoV-2. In this study, we developed an electrolyte-gated indium-gallium-zinc-oxide (IGZO) thin-film transistor with sequential surface modification to realize the low limit of detection (LoD <50 fM) and a wide detection range from 50 fM to 5 µM with good linearity (R2 = 0.9965), and recyclability. The surface chemical modification was achieved to anchor the single strand of SARS-CoV-2 DNA via selective hybridization. Moreover, the minute electrical signal change following the chemical modification was investigated by in-depth physicochemical analytical techniques. Finally, we demonstrate fully recyclable biosensors based on oxygen plasma treatment. Owing to its cost-effective fabrication, rapid detection at the single-molecule level, and low detection limit, the proposed biosensor can be used as a point-of-care platform to perform timely and effective SARS-CoV-2 detection.

Recent Advances in Biosensor Technologies for Point-of-Care Urinalysis.

Human urine samples are non-invasive, readily available, and contain several components that can provide useful indicators of the health status of patients. Hence, urine is a desirable and important template to aid in the diagnosis of common clinical conditions. Conventional methods such as dipstick tests, urine culture, and urine microscopy are commonly used for urinalysis. Among them, the dipstick test is undoubtedly the most popular owing to its ease of use, low cost, and quick response. Despite these advantages, the dipstick test has limitations in terms of sensitivity, selectivity, reusability, and quantitative evaluation of diseases. Various biosensor technologies give it the potential for being developed into point-of-care (POC) applications by overcoming these limitations of the dipstick test. Here, we present a review of the biosensor technologies available to identify urine-based biomarkers that are typically detected by the dipstick test and discuss the present limitations and challenges that future development for their translation into POC applications for urinalysis.

Ultra-fast and recyclable DNA biosensor for point-of-care detection of SARS-CoV-2 (COVID-19).

Rapid diagnosis and case isolation are pivotal to controlling the current pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, a label-free DNA capacitive biosensor for the detection of SARS-CoV-2 that demonstrates real-time, low-cost, and high-throughput screening of nucleic acid samples is presented. Our novel biosensor composed of the interdigitated platinum/titanium electrodes on the glass substrate can detect the hybridization of analyte DNA with probe DNA. The hybridization signals of specific DNA sequences were verified through exhaustive physicochemical analytical techniques such as Fourier transform infrared (FT-IR) spectrometry, contact-angle analysis, and capacitance-frequency measurements. For a single-step hybridized reaction, the fabricated kit exhibited significant sensitivity (capacitance change, ΔC = ~2 nF) in detecting the conserved region of the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) gene with high sensitivity of 0.843 nF/nM. In addition to capacitive measurements, this selective detection was confirmed by the fluorescence image and intensity from a SARS-CoV-2 gene labeled with a fluorescent dye. We also demonstrated that the kits are recyclable by surface ozone treatment using UV irradiation. Thus, these kits could potentially be applied to various types of label-free DNA, thereby acting as rapid, cost-effective biosensors for several diseases.