A highly sensitive and low-background fluorescence assay for pesticides residues based on hybridization chain reaction amplification assisted by magnetic separation

Applications of hybridization chain reaction optical detection incorporating nanomaterials: A review

The development of powerful, simple and cost-effective signal amplifiers has significant implications for biological research and analysis. Hybridization chain reaction (HCR) has attracted increasing attention because of its enzyme-free, simple, and efficient amplification. In the HCR process, an initiator probe triggered a pair of metastable hairpins through a cross-opening process to propagate a chain reaction of hybridization events, yielding a long-nicked double-stranded nucleic acid structure. To achieve more noticeable signal amplification, nanomaterials, including graphene oxide, quantum dots, gold, silver, magnetic, and other nanoparticles, were integrated with HCR. Various types of colorimetric, fluorescence, plasmonic analyses or chemiluminescence optical sensing strategies incorporating nanomaterials have been developed to analyze various targets, such as nucleic acids, small biomolecules, proteins, and metal ions. This review summarized the recent advances of HCR technology pairing diverse nanomaterials in optical detection and discussed their challenges.

Recent advancements in the detection of organophosphate pesticides: a review

Organophosphorus pesticides (OPPs) are generally utilized for the protection of crops from pests. Because the use of OPPs in various agricultural operations has expanded dramatically, precise monitoring of their concentration levels has become the critical issue, which will help in the protection of ecological systems and food supply. However, the World Health Organization (WHO) has classified them as extremely dangerous chemical compounds. Taking their immense use and toxicity into consideration, the development of easy, rapid and highly sensitive techniques is necessary. Despite the fact that there are numerous conventional ways for detecting OPPs, the development of portable sensors is required to make routine analysis considerably more convenient. Some of these advanced techniques include colorimetric sensors, fluorescence sensors, molecular imprinted polymer-based sensors, and surface plasmon resonance-based sensors. This review article specifically focuses on the colorimetric, fluorescence and electrochemical sensors. In this article, the sensing strategies of these developed sensors, analytical conditions and their respective limit of detection are compiled.

Molybdenum disulfide@5-carboxyfluorescein-probe biosensor for unamplified specific fragment detection in long nucleic acids based on magnetic composite probe-actuated deblocking of secondary structure

Secondary structures in long circulating tumor nucleic acids have potential obstacles for specific location point hybridized detection of gene fragments. The exploration of biosensing strategies requires selectively changing the nucleic acids conformation and inducing signal switching. Herein, a self-assembled magnetic composite probe (MCP) was fabricated by the hybridization reaction of Linker DNA and a "Y"-junction-DNA nanostructure on the surface of magnetic beads, contributing to the capture, secondary structure unlocking, and enrichment of the PML/RARα DNA "L" subtype. Then, by integrating the MCP-actuated reactor, a one-step "off-on" signal switching MoS2@FAM-probe biosensing method was developed for the efficient detection of the PML/RARα DNA "L" subtype. The proposed biosensor was capable of detecting 100 bases PML/RARα DNA "L" subtype with a wide linear range of 1 pM to 200 nM and a limit of detection down to 0.223 pM without signal amplification. In addition, the biosensing method was successfully applied for the detection of target in serum samples. It is worth pointing out that this simple biosensing strategy could enable long nucleic acids fragments with secondary structures from ctDNA and ctRNA to be quantitatively assayed based on direct hybridization.

N-methyl mesoporphyrin IX as a highly selective light-up probe for G-quadruplex DNA

N-methyl mesoporphyrin IX (NMM) is a water-soluble, non-symmetric porphyrin with excellent optical properties and unparalleled selectivity for G-quadruplex (GQ) DNA. G-quadruplexes are non-canonical DNA structures formed by guanine-rich sequences. They are implicated in genomic stability, longevity, and cancer. The ability of NMM to selectively recognize GQ structures makes it a valuable scaffold for designing novel GQ binders. In this review, we survey the literature describing the GQ-binding properties of NMM as well as its wide utility in chemistry and biology. We start with the discovery of the GQ-binding properties of NMM and the development of NMM-binding aptamers. We then discuss the optical properties of NMM, focusing on the light-switch effect - high fluorescence of NMM induced upon its binding to GQ DNA. Additionally, we examine the affinity and selectivity of NMM for GQs, as well as its ability to stabilize GQ structures and favor parallel GQ conformations. Furthermore, a portion of the review is dedicated to the applications of NMM-GQ complexes as biosensors for heavy metals, small molecules (e.g. ATP and pesticides), DNA, and proteins. Finally and importantly, we discuss the utility of NMM as a probe to investigate the roles of GQs in biological processes.