Folding- and Dynamics-Based Electrochemical DNA Sensors

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

Substrate Materials for Biomolecular Immobilization within Electrochemical Biosensors

Electrochemical biosensors have potential applications for agriculture, food safety, environmental monitoring, sports medicine, biomedicine, and other fields. One of the primary challenges in this field is the immobilization of biomolecular probes atop a solid substrate material with adequate stability, storage lifetime, and reproducibility. This review summarizes the current state of the art for covalent bonding of biomolecules onto solid substrate materials. Early research focused on the use of Au electrodes, with immobilization of biomolecules through ω-functionalized Au-thiol self-assembled monolayers (SAMs), but stability is usually inadequate due to the weak Au-S bond strength. Other noble substrates such as C, Pt, and Si have also been studied. While their nobility has the advantage of ensuring biocompatibility, it also has the disadvantage of making them relatively unreactive towards covalent bond formation. With the exception of Sn-doped In2O3 (indium tin oxide, ITO), most metal oxides are not electrically conductive enough for use within electrochemical biosensors. Recent research has focused on transition metal dichalcogenides (TMDs) such as MoS2 and on electrically conductive polymers such as polyaniline, polypyrrole, and polythiophene. In addition, the deposition of functionalized thin films from aryldiazonium cations has attracted significant attention as a substrate-independent method for biofunctionalization.

Highly sensitive determination of DNA via a new type of electrochemical zirconium signaling probe

Exploiting Zr(iv) as a redox probe for the detection of DNA has great potential in clinical analysis.

Understanding Signal and Background in a Thermally Resolved, Single-Branched DNA Assay Using Square Wave Voltammetry

Electrochemical bioanalytical sensors with oligonucleotide transducer molecules have been recently extended for quantifying a wide range of biomolecules, from small drugs to large proteins. Short DNA or RNA strands have gained attention recently due to the existence of circulating oligonucleotides in human blood, yet challenges remain for adequately sensing these targets at electrode surfaces. In this work, we have developed a quantitative electrochemical method which uses target-induced proximity of a single-branched DNA structure to drive hybridization at an electrode surface, with readout by square-wave voltammetry (SWV). Using custom instrumentation, we first show that precise control of temperature can provide both electrochemical signal amplification and background signal depreciation in SWV readout of small oligonucleotides. Next, we thoroughly compared 25 different combinations of binding energies by their signal-to-background ratios and differences. These data served as a guide to select the optimal parameters of binding energy, SWV frequency, and assay temperature. Finally, the influence of experimental workflow on the sensitivity and limit of detection (LOD) of the sensor is demonstrated. This study highlights the importance of precisely controlling temperature and SWV frequency in DNA-driven assays on electrode surfaces while also presenting a novel instrumental design for fine-tuning of such systems.