Exploiting epoxy-rich poly(ethylene glycol) films for highly selective ssDNA sensing via electrochemical impedance spectroscopy

This study introduces an alternative approach to immobilize thiolated single-stranded DNA (ssDNA) for the DNA sensing. In contrast to the standard, monomolecular assembly of such moieties on gold substrate, over the thiolate-gold anchors, we propose to use bioinert, porous polyethylene glycol (PEG) films as a 3D template for ssDNA immobilization. The latter process relies on the reaction between the thiol group of the respectively decorated ssDNA and the epoxy groups in the epoxy-rich PEG matrix. The immobilization process and subsequent hybridization ability of the resulting sensing assembly were monitored using cyclic voltammetry and electrochemical impedance spectroscopy, with the latter tool proving itself as the most suitable transduction technique. Electrochemical data confirmed the successful immobilization of thiol-decorated ssDNA probes into the PEG matrix over the thiol-epoxy linkage as well as high hybridization efficiency, selectivity, and sensitivity of the resulting DNA sensor. Whereas this sensor was equivalent to the direct ssDNA assembly in terms of the efficiency, it exhibited a better selectivity and bioinert properties in view of the bioinert character of the PEG matrix. The above findings place PEG films as a promising platform for highly selective ssDNA sensing, leveraging their flexible chemistry, 3D character, and bioinert properties.

Label-free ultra-sensitive colorimetric detection of hepatitis E virus based on oxidase-like activity of MnO2 nanosheets

Hepatitis E virus (HEV) is an evolving infectious entity that causes viral hepatitis infections worldwide. Current routine methods of identifying and diagnosing HEV are someway laborious and costly. Based on the biomimicking oxidase-like activity of MnO₂ nanosheets, we designed a label-free, highly sensitive colorimetric sensing technique for HEV detection. The prepared MnO₂ catalyst displays intrinsic biomimicking oxidase-like catalytic activity and efficiently oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) substrate from colorless to blue colored oxidized TMB (oxTMB) product which can be measured at 652 nm by UV-visible spectrum. When the HEV-DNA was added, DNA adsorbed easily on MnO₂ surface through physical adsorption and electrostatic interaction which hinders the oxidase-like catalytic activity of MnO₂. Upon the introduction of target, the HEV target DNA binds with its complementary ssDNA on the surface of MnO₂, the hybridized DNA releases from the surface of MnO₂, which leads to recovery of oxidase-like catalytic activity of MnO₂. This strategy was applied to construct a colorimetric technique for HEV detection. The approach works in the linear range of 1 fM-100 nM DNA concentration with the limit of detection (LOD) of 3.26 fM (S/N = 3) and quantitative limit (LOQ) of 36.08 fM. The TMB-MnO₂ platform was highly selective for HEV target DNA detection when compared with potential interferences. Result of serum sample analysis demonstrates that this sensing system can be used for clinical diagnostic applications.

Biomass-Derived Carbon Dots and Their Sensing Applications

Carbon dots (CDs) can be widely used in the field of sensing because of its good water solubility, low toxicity, high fluorescence stability and excellent biocompatibility. It has become a popular trend to prepare high-value, inexpensive, renewable and environmentally friendly CDs sensors from biomass resources. This article reviewed the research progress of biomass-derived CDs as chemical, physical and biological sensors in recent years and studied their preparation processes and sensing abilities. Furthermore, the prospects and challenges of biomass-CDs sensors were discussed. This article is expected to provide inspirations for the design, preparation and application of biomass-CDs sensors in the future.

High-performance electrochemical sensing of hazardous pesticide Paraoxon using BiVO4 nano dendrites equipped catalytic strips

Paraoxon is one of the pesticide that can induce toxicity to nervous system of living organisms. In this work, we focused on synthesizing the catalyst Bismuth Vanadate with the properties that can sense the presence of organophosphorus compounds and characterized them with various characterization methods. The structural studies done by XRD, UV spectroscopy and FTIR spectroscopy. Morphological studies were carried by SEM and TEM. Elemental analysis using XPS spectra. The proposed electrocatalyst was successfully applied as the active electrode material modifying the screen printed carbon electrode for electrochemical sensor applications. The results of the studies indicate that bismuth vanadate modified electrode exhibited four electron transfer process for reduction of nitro group and this lead to the superior electrochemical sensing performance for ethyl Paraoxon with a detection limit of 0.03 μM and good sensitivity 0.345 μA μM^-1 cm^-2 with excellent reproducibility, repeatability, stability and selectivity over common interferents. Furthermore, the practical application was successfully carried using the proposed modified strips to determine Paraoxon presence in the river water sample with satisfactory results. This proposed catalyst can act as a desirable candidate for the rapid electrochemical sensor.

Simple construction of GdBiVO4 assembled on reduced graphene oxide for selective and sensitive electrochemical detection of chloramphenicol in food samples

In the present study, the influence of phase purity and crystallinity on the electrochemical properties of well-designed GdBiVO4@rGO nanocomposite, fabricated by the facile hydrothermal method for the detection of chloramphenicol (CP), is reported.

Cochineal quinone carbon dot synthesis via a keto–enol tautomerism strategy and their intermolecular photo-induced cross-redox interactions with tetracycline

Specific molecular recognition of tetracycline by carminic acid-formed carbon dots taking advantage of the common quinone molecular structural unit.