Selection of DNA aptamer and its application as an electrical biosensor for Zika virus detection in human serum.

Zika virus is a highly infectious virus that is part of the flavivirus group. Precise diagnosis of the Zika virus is significant issue for controlling a global pandemic after the COVID-19 era. For the first time, we describe a zika virus aptamer-based electrical biosensor for detecting Zika virus in human serum. The electrical biosensor composed of a Zika virus aptamer/MXene nanoparticle heterolayer on Au micro-gap electrode (AuMGE)/print circuit board (PCB) system. The Zika virus aptamer was designed to bind the envelope protein of the Zika virus by systematic evolution of ligands by exponential enrichment (SELEX) technique. The binding affinity of the aptamer was determined by fluorescence. For improving the sensor signal sensitivity, Ti3C2Tx MXene was introduced to surface of Au micro-gap electrode (AuMGE). The immobilization process was confirmed by atomic force microscopy (AFM). The prepared aptamer/MXene immobilized on AuMGE can detect the Zika virus through capacitance change according to the target concentration. The capacitance signal from the biosensor increased linearly according to increment of envelope proteins in the human serum. The limit of detection was determined to 38.14 pM, and target proteins could be detected from 100 pM to 10 µM. Thus, the developed electrical aptabiosensor can be a useful tool for Zika virus detection.

Rapid electrochemical dual-target biosensor composed of an Aptamer/MXene hybrid on Au microgap electrodes for cytokines detection.

Rapid detection methods for cytokine storm markers, such as tumor necrosis factor α (TNF-α) and interferon gamma (IFN-γ), are required. Herein, we describe the fabrication of a rapid electrochemical dual-target biosensor composed of aptamer/MXene (Ti3C2) nanosheet on an Au microgap electrode. Alternating current electrothermal flow (ACEF) significantly reduced the detection time (<10 min) to achieve the rapid biosensor construction. Additionally, MXene nanosheet was synthesized to improve the detection sensitivity. A dual-type Au microgap electrode was designed to measure TNF-α and IFN-γ levels using a single biosensor. Moreover, it performs 12 measurements using a small sample volume. To reduce detection time with stable aptamer-target complex formation, various ACEF conditions were evaluated and optimized to 10 min. Using the optimal conditions, the limit of detection (LOD) and selectivity were determined by electrochemical impedance spectroscopy (EIS). A linear region was observed in the concentration range of 1 pg/mL to 10 ng/mL of TNF-α and IFN-γ. The LOD of TNF-α and IFN-γ were 0.15 pg/mL and 0.12 pg/mL within 10 min, respectively. Furthermore, the proposed biosensor detected TNF-α and IFN-γ diluted in 10% human serum in the concentration range of 1 pg/mL to 10 ng/mL with LODs of 0.25 pg/mL and 0.26 pg/mL, respectively.

Soft, skin-interfaced microfluidic systems with integrated enzymatic assays for measuring the concentration of ammonia and ethanol in sweat.

Eccrine sweat is a rich and largely unexplored biofluid that contains a range of important biomarkers, from electrolytes, metabolites, micronutrients and hormones to exogenous agents, each of which can change in concentration with diet, stress level, hydration status and physiologic or metabolic state. Traditionally, clinicians and researchers have used absorbent pads and benchtop analyzers to collect and analyze the biochemical constituents of sweat in controlled, laboratory settings. Recently reported wearable microfluidic and electrochemical sensing devices represent significant advances in this context, with capabilities for rapid, in situ evaluations, in many cases with improved repeatability and accuracy. A limitation is that assays performed in these platforms offer limited control of reaction kinetics and mixing of different reagents and samples. Here, we present a multi-layered microfluidic device platform with designs that eliminate these constraints, to enable integrated enzymatic assays with demonstrations of in situ analysis of the concentrations of ammonia and ethanol in microliter volumes of sweat. Careful characterization of the reaction kinetics and their optimization using statistical techniques yield robust analysis protocols. Human subject studies with sweat initiated by warm-water bathing highlight the operational features of these systems.