Stepping gating of ion channels on nanoelectrode via DNA hybridization for label-free DNA detection

Fabrication and Characterization of Iridium Oxide pH Microelectrodes Based on Sputter Deposition Method

pH value plays an important role in many fields such as chemistry and biology; therefore, rapid and accurate pH measurement is very important. Because of its advantages in preparation, wide test range, rapid response, and good biocompatibility, iridium oxide material has received more and more attention. In this paper, we present a method for preparing iridium oxide pH microelectrodes based on the sputter deposition method. The sputtering parameters of iridium oxide are also studied and optimized. Open-circuit potential tests show that microelectrodes exhibit near-Nernstian pH response with good linearity (about 60 mV/pH), fast response, high stability (a slight periodic fluctuation of potential change <2.5 mV in 24 h), and good reversibility in the pH range of 1.00–13.00.

Nucleic Acid Tests for Clinical Translation

Nucleic acids, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are natural biopolymers composed of nucleotides that store, transmit, and express genetic information. Overexpressed or underexpressed as well as mutated nucleic acids have been implicated in many diseases. Therefore, nucleic acid tests (NATs) are extremely important. Inspired by intracellular DNA replication and RNA transcription, in vitro NATs have been extensively developed to improve the detection specificity, sensitivity, and simplicity. The principles of NATs can be in general classified into three categories: nucleic acid hybridization, thermal-cycle or isothermal amplification, and signal amplification. Driven by pressing needs in clinical diagnosis and prevention of infectious diseases, NATs have evolved to be a rapidly advancing field. During the past ten years, an explosive increase of research interest in both basic research and clinical translation has been witnessed. In this review, we aim to provide comprehensive coverage of the progress to analyze nucleic acids, use nucleic acids as recognition probes, construct detection devices based on nucleic acids, and utilize nucleic acids in clinical diagnosis and other important fields. We also discuss the new frontiers in the field and the challenges to be addressed.

Current and Perspective Diagnostic Techniques for COVID-19

Since late December 2019, the coronavirus pandemic (COVID-19; previously known as 2019-nCoV) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been surging rapidly around the world. With more than 1,700,000 confirmed cases, the world faces an unprecedented economic, social, and health impact. The early, rapid, sensitive, and accurate diagnosis of viral infection provides rapid responses for public health surveillance, prevention, and control of contagious diffusion. More than 30% of the confirmed cases are asymptomatic, and the high false-negative rate (FNR) of a single assay requires the development of novel diagnostic techniques, combinative approaches, sampling from different locations, and consecutive detection. The recurrence of discharged patients indicates the need for long-term monitoring and tracking. Diagnostic and therapeutic methods are evolving with a deeper understanding of virus pathology and the potential for relapse. In this Review, a comprehensive summary and comparison of different SARS-CoV-2 diagnostic methods are provided for researchers and clinicians to develop appropriate strategies for the timely and effective detection of SARS-CoV-2. The survey of current biosensors and diagnostic devices for viral nucleic acids, proteins, and particles and chest tomography will provide insight into the development of novel perspective techniques for the diagnosis of COVID-19.

Multi-signal amplification electrochemical DNA biosensor based on exonuclease III and tetraferrocene

Homogeneous electrochemical DNA biosensors' unique qualities have been of great interest to researchers, mainly due to their high recognition efficiency in solutions. However, the processes of introducing additional markers and extra operations to obtain a signal are tedious and time consuming, which limits their overall potential applications. Herein, a novel tetraferrocene was synthesized and used as a homogeneous electrochemical DNA biosensor probe label. It contains four ferrocene units, which provide greater signaling potential compared to monoferrocene. Furthermore, the target DNA triggers the digestion of the double hairpin DNA probe with the aid of exonuclease III, promoting short single stranded DNA probe formation. With the combination of the incorporated tetraferrocene labeled short DNA probe strands and graphene's ability to adsorb single stranded DNA, the hybridization process can produce an electrode signal provided by tetraferrocene. A low detection limit of 8.2 fM toward target DNA with excellent selectivity was achieved. The proposed sensing system avoids tedious and time-consuming steps of DNA modification, making the experimental processes simpler and convenient. The advantages of high sensitivity, selectivity and simple operation make this strategy applicable to DNA detection.