Sensitive electrochemical aptasensor for determination of sulfaquinoxaline based on AuPd NPs@UiO-66-NH2/CoSe2 and RecJf exonuclease-assisted signal amplification

The authors designed a sensitive label-free electrochemical aptasensor for the detection of sulfaquinoxaline (SQX), including the AuPd NPs@UiO-66-NH₂/CoSe₂ nanocomposites and RecJf exonuclease-assisted target recycle signal amplification strategy. AuPd NPs@UiO-66-NH₂/CoSe₂ nanocomposite with excellent conductivity and numerous active sites was successfully synthesized to provide a favorable sensing platform and load more double-strand DNA (dsDNA) on the electrode surface. The negatively charged phosphate group of the oligonucleotide and [Fe (CN)₆] ^3-/4- repel each other electrostatically, resulting in very low electrical signals. In the presence of SQX, its corresponding aptamer will be released from the double-stranded structure and then digested by RecJf exonuclease, which resulted in the SQX being released to initiate the next recycling to help amplify the DPV signal. Under the optimal conditions, the peak current has a linear relationship with the logarithmic of SQX concentration in the range of 1 pg/mL∼100 ng/mL and the obtained detection limit was 0.547 pg/mL. Furthermore, the contrasted aptasensor possess reliable specificity, reproducibility and stability toward SQX, and has been applied to detect SQX in pork samples with a satisfied recovery varied from 94.40% to 95.98%.

Molecularly imprinted polymers in toxicology: a literature survey for the last 5 years

The science of toxicology dates back almost to the beginning of human history. Toxic chemicals, which are encountered in different forms, are always among the chemicals that should be investigated in criminal field, environmental application, pharmaceutic, and even industry, where many researches have been carried out studies for years. Almost all of not only drugs but also industrial dyes have toxic side and direct effects. Environmental micropollutants accumulate in the tissues of all living things, especially plants, and show short- or long-term toxic symptoms. Chemicals in forensic science can be known by detecting the effect they cause to the body with the similar mechanism. It is clear that the best tracking tool among analysis methods is molecularly printed polymer-based analytical setups. Different polymeric combinations of molecularly imprinted polymers allow further study on detection or extraction using chromatographic and spectroscopic instruments. In particular, methods used in forensic medicine can detect trace amounts of poison or biological residues on the scene. Molecularly imprinted polymers are still in their infancy and have many variables that need to be developed. In this review, we summarized how molecular imprinted polymers and toxicology intersect and what has been done about molecular imprinted polymers in toxicology by looking at the studies conducted in the last 5 years.

Design of heterostructured hybrids comprising ultrathin 2D bismuth tungstate nanosheets reinforced by chloramphenicol imprinted polymers used as biomimetic interfaces for mass-sensitive detection

Combining nanomaterials in varying morphology and functionalities gives rise to a new class of composite materials leading to innovative applications. In this study, we designed a heterostructured hybrid material consisting of two-dimensional bismuth nanosheets augmented by molecularly imprinted networks. Antibiotic overuse is now one of the main concerns in health management, and their monitoring is highly desirable but challenging. So, for this purpose, the resulting composite interface was used as a transducer for quartz crystal microbalances. The main objective was to develop highly selective mass-sensitive sensor for chloramphenicol. Morphological investigation revealed the presence of ultrathin, square shaped nanosheets, 2-3 nm in height and further supplemented by imprinted polymers. Sensor responses are described as the decrease in the frequency of microbalances owing to chloramphenicol re-binding in the templated cavities, yielding a detection limit down to 0.74 μM. This sensor demonstrated a 100 % specific detection of chloramphenicol over its interfering and structural analogs (clindamycin, thiamphenicol, and florfenicol). This composite interface offers the advantage of selective binding and excellent sensitivity due to special heterostructured morphology, in addition to benefits of robustness and online monitoring. The results suggest that such composite-based sensors can be favorable platforms, especially for commercial prospects, to obtain selective detection of other biomolecules of clinical importance.

QuEChERS pretreatment combined with high-performance liquid chromatography-tandem mass spectrometry for determination of aristolochic acids I and II in Chinese herbal patent medicines

Aristolochic acid I and II (AA I and II), a kind of nephrotoxic and carcinogenic compound, are widely added in Chinese herbal patent medicines though they have been banned due to their toxicity. However, the traditional sample pre-treatment combined with the LC-MS analysis system is not effective to determine AAs in such complicated patent medicines. The QuEChERS pretreatment method possesses some merits such as being quick and effective. In this work, the modified QuEChERS method was first used to determine AA I and II in Chinese herbal patent medicines combined with the HPLC-MS/MS analysis system. Extraction and removal of target analytes from powder, tablet, and capsule samples were conducted using the modified QuEChERS pretreatment. The liquid extracts of Chinese herbal patent medicines could be analyzed directly. The method optimization results show that average recoveries ranged from 96.6% to 110.3% with relative standard deviations ranging from 4.2% to 13.0%. The quantization limits of the three selected matrices are estimated as follows (AA I/II): 2.8/6.5 ng mL^−l in liquid herbal extract, 6.5/12.5 ng g⁻¹ in tablets, and 22.1/42.1 ng g⁻¹ in capsules. This method was conducted to investigate the presence of AAs, which are a type of nephrotoxic and carcinogenic carboxylic acid, in 30 herbal products sold through the Internet in China. AA I and II were detected in 53% and 20%, respectively, of tested samples.

Aristolochic acid I and II (AA I and II), a kind of nephrotoxic and carcinogenic compound, are widely added in Chinese herbal patent medicines though they have been banned due to their toxicity.

A Cu(II)-anchored unzipped covalent triazine framework with peroxidase-mimicking properties for molecular imprinting-based electrochemiluminescent detection of sulfaquinoxaline

The authors describe a method of electrochemiluminescent quantitation of the antibiotic sulfaquinoxaline (SQX). It relies on the use of a molecularly imprinted polymer and a Cu(II)-anchored unzipped covalent triazine framework (UnZ-CCTF) with excellent dispersibility, electrical conductivity, and peroxidaze-like activity. The framework was prepared by unzipping a covalent triazine framework under retention of basic triazine units. It was morphologically and structurally characterized by a range of instrumental techniques. The excellent peroxidase-mimicking effect of UnZ-CCTF on the electrochemiluminescence of the luminol/H₂O₂ system was exploited to design an ultrasensitive SQX assay with a 1.0-20 pM detection range and a detection limit of 0.76 pM (at 3δ/m). The technique was used for SQX quantitation in spiked milk samples, achieving recoveries of 94.0-104.8%. Graphical abstract Scheme of the sulfaquinoxaline molecularly imprinted electrochemiluminescence sensor based on Cu-anchored unzipped covalent triazine frameworks.

Porous SnO2 nanoparticles based ion chromatographic determination of non-fluorescent antibiotic (chloramphenicol) in complex samples

Nowadays, there are rising concerns about the extensive use of the antibiotics such as chloramphenicol (CAP), has threatened the human life in the form of various vicious diseases. The limited selectivity and sensitivity of confirmatory techniques (UV and electrochemical) and non-fluorescence property of CAP make its determination a challenging task in the modern pharmaceutical analysis. In order to redeem the selective, sensitive and cost-effective fluorescence methodology, here by the dual role of synthesized porous SnO2 nanoparticles were exploited; (i) a porous sorbent in a µ-QuEChERS based sample preparation and as (ii) a stimulant for the transformation of non-fluorescent analytes namely CAP and p-nitrophenol (p-NP) into their respective fluorescent product. We report a green, simple, selective and cost effective ion chromatographic method for CAP sensitive determination in three complex matrices including milk, human urine and serum. The synthesized sorbent not only selectively adsorbed and degraded the matrix/interferences but also selectively reduced the non-fluorescent antibiotic CAP into a fluorescent species. This developed ion chromatographic method exhibited good selectivity, linearity (r2 ≥ 0.996) and limit of detection (LOD) was in the range 0.0201-0.0280 µg/kg. The inter- and intraday precisions were also satisfactory having a relative standard deviation (RSDs) less than 14.96% and excellent recoveries of CAP in the range of 78.3-100.2% were retrieved in various complex samples.

QuEChERS extraction for multi-residue analysis of PCBs, PAHs, PBDEs and PCDD/Fs in biological samples

In this study, a fast and rugged method is presented for the analysis of PCBs, PAHs, PBDEs and PCDD/Fs in biological tissues using a simple Quick, Easy, Cheap, Efficient, Rugged and Safe (QuEChERS) extraction and a clean-up by Gel Permeation Chromatography (GPC) and silica Solid Phase Extraction (SPE). Development was performed on blue mussels (Mytilus edulis) and Atlantic salmon (Salmo salar) for evaluation of two ranges of lipid and water content of biological tissues. Statistical validation was performed with Atlantic salmon samples. Forty-five PAHs were analyzed including the priority list of the US EPA and the European Union with 41 PCBs, 24 PBDEs and 17 PCDD/Fs. Instrumental analyses were performed on Gas Chromatography - High Resolution Mass Spectrometry (GC-HRMS). Accuracy was evaluated for PCBs and PCDD/Fs with a certified reference material furnished by the National Research Council Canada (NRCC) and also compared with results obtained by the conventional Soxhlet extraction. Statistical validation showed recoveries for PCBs, PAHs, PBDEs and PCDD/Fs close to 100% with average Relative Standard Deviation (RSD) lower than 10% and internal standard recoveries in the range of 70% with average RSD ranging from 5-15%. Average calculated Method Detection Limits (MDLs) were lower than 0.05μg/Kg for PCBs, 0.2μg/Kg for PAHs and PBDEs and 1ng/Kg for PCDD/Fs. The method is a faster and cheaper alternative to the time-consuming conventional method that has been used in most environmental laboratories.