An electroanalytical platform for nereistoxin-related insecticide detection based on DNA conformational switching and exonuclease III assisted target recycling

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%.

Marine Origin Ligands of Nicotinic Receptors: Low Molecular Compounds, Peptides and Proteins for Fundamental Research and Practical Applications

The purpose of our review is to briefly show what different compounds of marine origin, from low molecular weight ones to peptides and proteins, offer for understanding the structure and mechanism of action of nicotinic acetylcholine receptors (nAChRs) and for finding novel drugs to combat the diseases where nAChRs may be involved. The importance of the mentioned classes of ligands has changed with time; a protein from the marine snake venom was the first excellent tool to characterize the muscle-type nAChRs from the electric ray, while at present, muscle and α7 receptors are labeled with the radioactive or fluorescent derivatives prepared from α-bungarotoxin isolated from the many-banded krait. The most sophisticated instruments to distinguish muscle from neuronal nAChRs, and especially distinct subtypes within the latter, are α-conotoxins. Such information is crucial for fundamental studies on the nAChR revealing the properties of their orthosteric and allosteric binding sites and mechanisms of the channel opening and closure. Similar data are provided by low-molecular weight compounds of marine origin, but here the main purpose is drug design. In our review we tried to show what has been obtained in the last decade when the listed classes of compounds were used in the nAChR research, applying computer modeling, synthetic analogues and receptor mutants, X-ray and electron-microscopy analyses of complexes with the nAChRs, and their models which are acetylcholine-binding proteins and heterologously-expressed ligand-binding domains.

Highly Sensitive Electrochemical Aptasensor for Detection of Glypican-3 Using Hemin-Reduced Graphene Oxide-Platinum Nanoparticles Coupled with Conductive Reduced Graphene Oxide-Gold Nanoparticles

An electrochemical aptasensor for quantitatively detecting glypican-3 (GPC3) was constructed by combining hemin-reduced graphene oxide-platinum (H-rGO-Pt) nanoparticles (NPs) with reduced graphene oxide-gold (rGO-Au) nanoparticles (NPs). Herein, the rGO-Au NPs deposited onto screen-printed electrodes resulted in signal amplification due to their large surface areas. Meanwhile, highly conductive H-rGO-Pt NPs acted as a sensing medium that improved electrical conductivity and as an indicator for monitoring peak current for determination. A GPC3 aptamer (GPC3apt) with a low equilibrium dissociation constant was used as a bio-recognition molecule. GPC3apt specifically captured GPC3 proteins and formed aptamer-GPC3 complexes, which impeded electron transfer and thus hampered the redox signal of hemin in H-rGO-Pt NPs. This developed electrochemical aptasensor showed a linear response to GPC3 (from 0.001 μg/mL to 10 μg/mL) and had a detection limit of 0.001 μg/mL. This work provides a low-cost and highly sensitive detection with and good recovery for GPC3 and holds great promise for the clinical diagnosis of hepatocellular carcinoma.

Emerging nanobiotechnology in agriculture for the management of pesticide residues

Utilization of pesticides is often necessary for meeting commercial requirements for crop quality and yield. However, incessant global pesticide use poses potential risks to human and ecosystem health. This situation increases the urgency of developing nano-biotechnology-assisted pesticide formulations that have high efficacy and low risk of side effects. The risks associated with both conventional and nanopesticides are summarized in this review. Moreover, the management of residual pesticides is still a global challenge. The contamination of soil and water resources with pesticides has adverse impact over agricultural productivity and food security; ultimately posing threats to living organisms. Pesticide residues in the eco-system may be treated via several biological and physicochemical processes, such as microbe-based degradation and advanced oxidation processes. With these issues in mind, we present a review that explores both existing and emerging techniques for management of pesticide residues and environmental risks. These techniques can offer a sustainable solution to revitalize the tarnished water/soil resources. Further, state-of-the-art research approaches to investigate biotechnological alternatives to conventional pesticides are discussed along with future prospects and mitigation techniques are recommended.