Construction of DNA Biosensors for Mercury (II) Ion Detection Based on Enzyme-Driven Signal Amplification Strategy

Berberrubine, A plant alkaloid derivative for superb-selective colorimetric quantification of aqueous mercury (II) in real samples and in aquatic plants

A new colorimetric sensor, berberrubine (BER-OH), was designed and synthesized based on berberine for superb selective sensing of Hg2+ in aqueous medium, addressing limitation of existing probes. The sensor exhibited high selectivity and sensitivity to Hg2+ in aqueous solution (CP buffer solution, pH 7.2) over other common metal ions (Na+, K+, Mg2+, Ca2+, Fe3+, Co2+, Fe2+, Cu2+, Al3+, Ba2+, Pb2+, Cd2+, Zn2+ and Sr2+). Upon addition of Hg2+, a distinct color change from reddish-orange to yellowish was observed due to complexation between BER-OH and Hg2+ in 1:1 stoichiometry. The binding of Hg2+ with BER-OH resulted in increasing absorbance at 347 and 430 nm with concurrent decreasing absorbance of the sensor at 377 and 487 nm. The limit of detection (LOD) values were calculated at absorption bands 347, 377, 487 nm and also using absorbance ratio, A347/A377. The sensor quantitatively analysed Hg2+, and the lowest LOD was found to be 46 nM with the range of 0.1 to 1.0 μM. The analytical tools confirmed that the proposed sensing mechanism involves the coordinate bond between lone pair of oxygen atoms of BER-OH and Hg2+. The sensor has great utility to detect trace Hg2+ in real samples like tap water, river water, and drinking water. A noteworthy application of the sensor is to quantify Hg2+ in aquatic plants which can absorb mercury from freshwater ecosystem. This simple yet effective sensing approach may offer a potential platform for the design of plant alkaloid-based sensing probes for environmentally hazardous elements.

Unique three-dimensional ordered macroporous dealloyed gold-silver electrochemical sensing platforms for ultrasensitive mercury(II) monitoring

To address the requirement of ultra-sensitive detection of trace mercury(II) (Hg2+) ions in the environment and food, we developed an electrochemical biosensor with super-sensitivity, extremely high selectivity, and reusability. This biosensor comprised two signal amplification components: a three-dimensional macroporous dealloyed (3DOMD) Au-Ag thin-film electrode and a multifunctional encoded Au@Pt nanocage (APNC). As a platform for immobilized capture DNA (cDNA), a 3DOMD Au-Ag thin film prepared by a dealloying method with an active surface area 4.8 times higher than that of 3D macroporous gold films generated by cyclic voltammetry (CV) with sulfuric acid was capable of increasing the sensing surface area while also strengthening the electron transport capacity of the sensing substrate due to its multilayered multi-porous framework. In the presence of Hg2+, probe DNA (pDNA) could be hybridized with the mismatched capture DNA (cDNA) through stable thymine-Hg2+-thymine (T-Hg2+-T) linkages, connecting thionine-APNC to the electrode surface and utilizing the large specific surface area to accomplish highly sensitive detection of Hg2+. With an extremely low Hg2+ detection limit of 2 pM and a detection range from 0.01 to 1000 nM, this technique opened up a new avenue for the ultrasensitive detection of a wider range of heavy metal ions or biomolecules.

Recent Advances in DNA Nanotechnology-Enabled Biosensors for Virus Detection

Virus-related infectious diseases are serious threats to humans, which makes virus detection of great importance. Traditional virus-detection methods usually suffer from low sensitivity and specificity, are time-consuming, have a high cost, etc. Recently, DNA biosensors based on DNA nanotechnology have shown great potential in virus detection. DNA nanotechnology, specifically DNA tiles and DNA aptamers, has achieved atomic precision in nanostructure construction. Exploiting the programmable nature of DNA nanostructures, researchers have developed DNA nanobiosensors that outperform traditional virus-detection methods. This paper reviews the history of DNA tiles and DNA aptamers, and it briefly describes the Baltimore classification of virology. Moreover, the advance of virus detection by using DNA nanobiosensors is discussed in detail and compared with traditional virus-detection methods. Finally, challenges faced by DNA nanobiosensors in virus detection are summarized, and a perspective on the future development of DNA nanobiosensors in virus detection is also provided.

Function of Graphene Oxide as the “Nanoquencher” for Hg2+ Detection Using an Exonuclease I-Assisted Biosensor

Graphene oxide is well known for its excellent fluorescence quenching ability. In this study, positively charged graphene oxide (pGO25000) was developed as a fluorescence quencher that is water-soluble and synthesized by grafting polyetherimide onto graphene oxide nanosheets by a carbodiimide reaction. Compared to graphene oxide, the fluorescence quenching ability of pGO25000 is significantly improved by the increase in the affinity between pGO25000 and the DNA strand, which is introduced by the additional electrostatic interaction. The FAM-labeled single-stranded DNA probe can be almost completely quenched at concentrations of pGO25000 as low as 0.1 μg/mL. A simple and novel FAM-labeled single-stranded DNA sensor was designed for Hg²⁺ detection to take advantage of exonuclease I-triggered single-stranded DNA hydrolysis, and pGO25000 acted as a fluorescence quencher. The FAM-labeled single-stranded DNA probe is present as a hairpin structure by the formation of T–Hg²⁺–T when Hg²⁺ is present, and no fluorescence is observed. It is digested by exonuclease I without Hg²⁺, and fluorescence is recovered. The fluorescence intensity of the proposed biosensor was positively correlated with the Hg²⁺ concentration in the range of 0–250 nM (R² = 0.9955), with a seasonable limit of detection (3σ) cal. 3.93 nM. It was successfully applied to real samples of pond water for Hg²⁺ detection, obtaining a recovery rate from 99.6% to 101.1%.

DNA-Based Biosensors for the Biochemical Analysis: A Review

In recent years, DNA-based biosensors have shown great potential as the candidate of the next generation biomedical detection device due to their robust chemical properties and customizable biosensing functions. Compared with the conventional biosensors, the DNA-based biosensors have advantages such as wider detection targets, more durable lifetime, and lower production cost. Additionally, the ingenious DNA structures can control the signal conduction near the biosensor surface, which could significantly improve the performance of biosensors. In order to show a big picture of the DNA biosensor's advantages, this article reviews the background knowledge and recent advances of DNA-based biosensors, including the functional DNA strands-based biosensors, DNA hybridization-based biosensors, and DNA templated biosensors. Then, the challenges and future directions of DNA-based biosensors are discussed and proposed.

Reimagining the Power of Nucleic Acids as Therapeutic and Diagnostic Agents

The central dogma of molecular biology proposes that in a typical cell, the flow of genetic information proceeds from DNA to RNA to polypeptide [...].