Generation of site-specifically labelled fluorescent human XPA to investigate DNA binding dynamics during nucleotide excision repair.

Nucleotide excision repair (NER) promotes genomic integrity by removing bulky DNA adducts introduced by external factors such as ultraviolet light. Defects in NER enzymes are associated with pathological conditions such as Xeroderma Pigmentosum, trichothiodystrophy, and Cockayne syndrome. A critical step in NER is the binding of the Xeroderma Pigmentosum group A protein (XPA) to the ss/ds DNA junction. To better capture the dynamics of XPA interactions with DNA during NER we have utilized the fluorescence enhancement through non-canonical amino acids (FEncAA) approach. 4-azido-L-phenylalanine (4AZP or pAzF) was incorporated at Arg-158 in human XPA and conjugated to Cy3 using strain-promoted azide-alkyne cycloaddition. The resulting fluorescent XPA protein (XPACy3) shows no loss in DNA binding activity and generates a robust change in fluorescence upon binding to DNA. Here we describe methods to generate XPACy3 and detail in vitro experimental conditions required to stably maintain the protein during biochemical and biophysical studies.

An electrochemical sensor based on CS-MWCNT and AuNPs for the detection of mycophenolic acid in plasma.

For patients receiving organ transplants, monitoring the blood concentration of MPA can provide timely information on whether MPA has reached the effective therapeutic window to better function while reducing the incidence of rejection or adverse reactions. In this study, an electrochemical sensor for the detection of MPA was built using a nanocomposite made of CS-MWCNT and AuNPs. At the same time, the high performance liquid phase (HPLC) method for MPA was established and compared with this sensor. The surface morphology, structure, and roughness of the material on the electrode were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and atomic force microscopy (AFM). In addition, the electrochemical behavior of the modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The standard curve was obtained in blank plasma, not pure buffer solution. The peak current was linearly related to the MPA concentration in the linear range of 0.001-0.1 mM with a detection limit of 0.05 µM and good anti-interference ability. Moreover, the sensor was employed with success for the determination of MPA in rat plasma with good recovery. The electrochemical sensor presented here is eco-friendly, and sensitive, and offers a great possibility for practical applicability.

Ethanol and NaCl-Induced Gold Nanoparticle Aggregation Toxicity toward DNA Investigated with a DNA/GCE Biosensor.

Engineered nanomaterials are becoming increasingly common in commercial and consumer products and pose a serious toxicological threat. Exposure of human organisms to nanomaterials can occur by inhalation, oral intake, or dermal transport. Together with the consumption of alcohol in the physiological environment of the body containing NaCl, this has raised concerns about the potentially harmful effects of ingested nanomaterials on human health. Although gold nanoparticles (AuNPs) exhibit great potential for various biomedical applications, there is some inconsistency in the case of the unambiguous genotoxicity of AuNPs due to differences in their shape, size, solubility, and exposure time. A DNA/GCE (DNA/glassy carbon electrode) biosensor was used to study ethanol (EtOH) and NaCl-induced gold nanoparticle aggregation genotoxicity under UV light in this study. The genotoxic effect of dispersed and aggregated negatively charged gold nanoparticles AuNP1 (8 nm) and AuNP2 (30 nm) toward salmon sperm double-stranded dsDNA was monitored by cyclic and square-wave voltammetry (CV, SWV). Electrochemical impedance spectroscopy (EIS) was used for a surface study of the biosensor. The aggregation of AuNPs was monitored by UV-vis spectroscopy. AuNP1 aggregates formed by 30% v/v EtOH and 0.15 mol·L-1 NaCl caused the greatest damage to the biosensor DNA layer.

Morphological Effects of Au Nanoparticles on Electrochemical Sensing Platforms for Nitrite Detection.

Au nanoparticles were synthesized in a soft template of pseudo-polyanions composed of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS) by the in situ reduction of chloroauric acid (HAuCl4) with PVP. The particle sizes and morphologies of the Au nanoparticles were regulated with concentrations of PVP or SDS at room temperature. Distinguished from the Au nanoparticles with various shapes, Au nanoflowers (AuNFs) with rich protrusion on the surface were obtained at the low final concentration of SDS and PVP. The typical AuNF synthesized in the PVP (50 g·L-1)-SDS (5 mmol·L-1)-HAuCl4 (0.25 mmol·L-1) solution exhibited a face-centered cubic structure dominated by a {111} crystal plane with an average equivalent particle size of 197 nm and an average protrusion height of 19 nm. Au nanoparticles with four different shapes, nanodendritic, nanoflower, 2D nanoflower, and nanoplate, were synthesized and used to modify the bare glassy carbon electrode (GCE) to obtain Au/GCEs, which were assigned as AuND/GCE, AuNF/GCE, 2D-AuNF/GCE, and AuNP/GCE, respectively. Electrochemical sensing platforms for nitrite detection were constructed by these Au/GCEs, which presented different detection sensitivity for nitrites. The results of cyclic voltammetry (CV) demonstrated that the AuNF/GCE exhibited the best detection sensitivity for nitrites, and the surface area of the AuNF/GCE was 1.838 times of the bare GCE, providing a linear c(NO2-) detection range of 0.01-5.00 µmol·L-1 with a limit of detection of 0.01 µmol·L-1. In addition, the AuNF/GCE exhibited good reproducibility, stability, and high anti-interference, providing potential for application in electrochemical sensing platforms.

Sustainable architecting of Co2SnO4/CE-BN-based electrochemical platform for highly selective and ultrasensitive detection of 2-nitroaniline in life samples.

A novel binary heterogeneous electrocatalyst, Co2SnO4, decorated on chemically exfoliated boron nitride sheets (CE-BN) with an exceptional capacity to detect electrochemical properties has been prepared by the simple hydrothermal method. The structural, surface morphology and electrochemical characteristics of Co2SnO4/CE-BN were characterized using a range of physicochemical and electrochemical techniques. Various voltammetric approaches were used to observe the analytical behaviour and applications of Co2SnO4/CE-BN/GCE for the determination of 2-nitroaniline (2-NA). The whole experiment is operated in the potential range from 0 to - 1.0 V vs Ag/AgCl (sat. KCl). The impact of operational factors on the peak current of 2-NA was investigated, including the pH, sample concentration, modifier amount and scan speed. With an estimated differential pulse voltammetry detection limit of 0.0371 µM and excellent sensitivity of 1,35 µA µM-1 cm-2, the produced sensor, Co2SnO4/CE-BN/GCE, revealed high electrocatalytic activity (DPV). The system is more practical and sustainable due to its repeatability, stability and reproducibility with respect to the results achieved for detection of 2-NA. The synthesized Co2SnO4/CE-BN-modified sensor may thus be a likely choice for the detection of 2-NA in actual water sample analysis.

Electrochemical investigations for COVID-19 detection-A comparison with other viral detection methods.

Virus-induced infection such as SARS-CoV-2 is a serious threat to human health and the economic setback of the world. Continued advances in the development of technologies are required before the viruses undergo mutation. The low concentration of viruses in environmental samples makes the detection extremely challenging; simple, accurate and rapid detection methods are in urgent need. Of all the analytical techniques, electrochemical methods have the established capabilities to address the issues. Particularly, the integration of nanotechnology would allow miniature devices to be made available at the point-of-care. This review outlines the capabilities of electrochemical methods in conjunction with nanotechnology for the detection of SARS-CoV-2. Future directions and challenges of the electrochemical biosensors for pathogen detection are covered including wearable and conformal biosensors, detection of plant pathogens, multiplexed detection, and reusable biosensors for on-site monitoring, thereby providing low-cost and disposable biosensors.

A Genetically Encoded Isonitrile Lysine for Orthogonal Bioorthogonal Labeling Schemes.

Bioorthogonal click-reactions represent ideal means for labeling biomolecules selectively and specifically with suitable small synthetic dyes. Genetic code expansion (GCE) technology enables efficient site-selective installation of bioorthogonal handles onto proteins of interest (POIs). Incorporation of bioorthogonalized non-canonical amino acids is a minimally perturbing means of enabling the study of proteins in their native environment. The growing demand for the multiple modification of POIs has triggered the quest for developing orthogonal bioorthogonal reactions that allow simultaneous modification of biomolecules. The recently reported bioorthogonal [4 + 1] cycloaddition reaction of bulky tetrazines and sterically demanding isonitriles has prompted us to develop a non-canonical amino acid (ncAA) bearing a suitable isonitrile function. Herein we disclose the synthesis and genetic incorporation of this ncAA together with studies aiming at assessing the mutual orthogonality between its reaction with bulky tetrazines and the inverse electron demand Diels-Alder (IEDDA) reaction of bicyclononyne (BCN) and tetrazine. Results showed that the new ncAA, bulky-isonitrile-carbamate-lysine (BICK) is efficiently and specifically incorporated into proteins by genetic code expansion, and despite the slow [4 + 1] cycloaddition, enables the labeling of outer membrane receptors such as insulin receptor (IR) with a membrane-impermeable dye. Furthermore, double labeling of protein structures in live and fixed mammalian cells was achieved using the mutually orthogonal bioorthogonal IEDDA and [4 + 1] cycloaddition reaction pair, by introducing BICK through GCE and BCN through a HaloTag technique.

Fully automated web-based tool for identifying regulatory hotspots.

BACKGROUND: Regulatory hotspots are genetic variations that may regulate the expression levels of many genes. It has been of great interest to find those hotspots utilizing expression quantitative trait locus (eQTL) analysis. However, it has been reported that many of the findings are spurious hotspots induced by various unknown confounding factors. Recently, methods utilizing complicated statistical models have been developed that successfully identify genuine hotspots. Next-generation Intersample Correlation Emended (NICE) is one of the methods that show high sensitivity and low false-discovery rate in finding regulatory hotspots. Even though the methods successfully find genuine hotspots, they have not been widely used due to their non-user-friendly interfaces and complex running processes. Furthermore, most of the methods are impractical due to their prohibitively high computational complexity. RESULTS: To overcome the limitations of existing methods, we developed a fully automated web-based tool, referred to as NICER (NICE Renew), which is based on NICE program. First, we dramatically reduced running and installing burden of NICE. Second, we significantly reduced running time by incorporating multi-processing. Third, besides our web-based NICER, users can use NICER on Google Compute Engine and can readily install and run the NICER web service on their local computers. Finally, we provide different input formats and visualizations tools to show results. Utilizing a yeast dataset, we show that NICER can be successfully used in an eQTL analysis to identify many genuine regulatory hotspots, for which more than half of the hotspots were previously reported elsewhere. CONCLUSIONS: Even though many hotspot analysis tools have been proposed, they have not been widely used for many practical reasons. NICER is a fully-automated web-based solution for eQTL mapping and regulatory hotspots analysis. NICER provides a user-friendly interface and has made hotspot analysis more viable by reducing the running time significantly. We believe that NICER will become the method of choice for increasing power of eQTL hotspot analysis.

An improved drop casting electrochemical strategy for furosemide quantification in natural waters exploiting chemically reduced graphene oxide on glassy carbon electrodes.

This work exploits the applicability of a chemically reduced graphene oxide (CRGO) modification on the electrochemical response of a glassy carbon electrode (GCE) for the first-time sensitive determination of furosemide in natural waters. The batch injection analysis (BIA) is proposed as an analytical method, where CRGO-GCE is coupled to a BIA cell for amperometric measurements. Acetate buffer (0.1 µmol L-1, pH 5.2) was used as the background electrolyte. The modification provided an increase in sensitivity (0.024 µA/µmol L-1), low limit of detection (0.7 µmol L-1), RSD (< 4%), and broad linear range (1-600 µmol L-1). Recovery tests performed in two different concentration ranges resulted in values between 89 and 99%. Recovery tests were performed and compared with high-performance liquid chromatography (HPLC) with UV-Vis detection using Student's t test at a 95% significance level, and no significant differences were found, confirming the accuracy of the method. The developed method is proven faster (169 h-1) compared with the HPLC analysis (5 h-1), also comparable with other flow procedures hereby described, offering a low-cost strategy suitable to quantify an emerging pharmaceutical pollutant. Graphical abstract.

Subcellular Localization Signals of bHLH-PAS Proteins: Their Significance, Current State of Knowledge and Future Perspectives.

The bHLH-PAS (basic helix-loop-helix/ Period-ARNT-Single minded) proteins are a family of transcriptional regulators commonly occurring in living organisms. bHLH-PAS members act as intracellular and extracellular "signals" sensors, initiating response to endo- and exogenous signals, including toxins, redox potential, and light. The activity of these proteins as transcription factors depends on nucleocytoplasmic shuttling: the signal received in the cytoplasm has to be transduced, via translocation, to the nucleus. It leads to the activation of transcription of particular genes and determines the cell response to different stimuli. In this review, we aim to present the current state of knowledge concerning signals that affect shuttling of bHLH-PAS transcription factors. We summarize experimentally verified and published nuclear localization signals/nuclear export signals (NLSs/NESs) in the context of performed in silico predictions. We have used most of the available NLS/NES predictors. Importantly, all our results confirm the existence of a complex system responsible for protein localization regulation that involves many localization signals, which activity has to be precisely controlled. We conclude that the current stage of knowledge in this area is still not complete and for most of bHLH-PAS proteins an experimental verification of the activity of further NLS/NES is needed.

Effects of green coffee extract supplementation on anthropometric indices, glycaemic control, blood pressure, lipid profile, insulin resistance and appetite in patients with the metabolic syndrome: a randomised clinical trial.

This study was conducted to elucidate the effects of decaffeinated green coffee bean extract (GCE) on anthropometric indices, glycaemic control, blood pressure, lipid profile, insulin resistance and appetite in patients with the metabolic syndrome (Mets). Subjects were randomly allocated to consume 400 mg GCE or placebo capsules twice per d for 8 weeks. Both groups were advised to follow an energy balanced diet. After GCE supplementation, systolic blood pressure (SBP) significantly reduced compared with the placebo group (-13·76 (sd 8·48) v. -6·56 (sd 9·58) mmHg, P=0·01). Also, GCE treatment significantly reduced fasting blood glucose (FBS) (-5·15 (sd 60·22) v. 29·42 (sd 40·01) mg/dl (-0·28 (SD 3·34) v. 1·63 (SD 2·22) mmol/l); P=0·03) and homoeostatic model of assessment of insulin resistance in comparison to placebo (-1·41 (sd 3·33) v. 1·23 (sd 3·84), P=0·02). In addition, waist circumference (-2·40 (sd 2·54) v. -0·66 (sd 1·17) cm, P=0·009) and appetite score (-1·44 (sd 1·72) v. -0·2 (sd 1·32), P=0·01) of the individuals supplemented with GCE indicated a significant decline. Besides, weight and BMI reduction in the intervention group was almost twice as much as the placebo group; however, this discrepancy was marginally significant (weight: -2·08 (sd 2·11) v. -0·92 (sd 1·30) kg, P=0·05). No difference was observed in terms of glycated Hb (HbA1c) percentage and lipid profile parameters between the two groups. To sum up, GCE administration had an ameliorating effect on some of the Mets components such as high SBP, high FBS and Mets main aetiological factors including insulin resistance and abdominal obesity. Furthermore, GCE supplementation could reduce appetite level.

Bacteria-Templated NiO Nanoparticles/Microstructure for an Enzymeless Glucose Sensor.

The bacterial-induced hollow cylinder NiO (HCNiO) nanomaterial was utilized for the enzymeless (without GOx) detection of glucose in basic conditions. The determination of glucose in 0.05 M NaOH solution with high sensitivity was performed using cyclic voltammetry (CV) and amperometry (i-t). The fundamental electrochemical parameters were analyzed and the obtained values of diffusion coefficient (D), heterogeneous rate constant (ks), electroactive surface coverage (Г), and transfer coefficient (alpha-α) are 1.75 × 10(-6) cm²/s, 57.65 M(-1)·s(-1), 1.45 × 10(-10) mol/cm², and 0.52 respectively. The peak current of the i-t method shows two dynamic linear ranges of calibration curves 0.2 to 3.5 µM and 0.5 to 250 µM for the glucose electro-oxidation. The Ni(2+)/Ni(3+) couple with the HCNiO electrode and the electrocatalytic properties were found to be sensitive to the glucose oxidation. The green chemistry of NiO preparation from bacteria and the high catalytic ability of the oxyhydroxide (NiOOH) is the good choice for the development of a glucose sensor. The best obtained sensitivity and limit of detection (LOD) for this sensor were 3978.9 µA mM(-1)·cm(-2) and 0.9 µM, respectively.

Tetrazine Amino Acid Encoding for Rapid and Complete Protein Bioconjugation.

Generating protein conjugates using the bioorthogonal ligation between tetrazines and trans-cyclooctene groups avoids the need to manipulate cysteine amino acids; this ligation is rapid, site-specific, and stoichiometric and allows for labeling of proteins in complex biological environments. Here, we provide a protocol for the expression of conjugation-ready proteins at high yields in Escherichia coli with greater than 95% encoding and labeling fidelity. This protocol focuses on installing the Tet2 tetrazine amino acid using an optimized genetic code expansion (GCE) machinery system, Tet2 pAJE-E7, to direct Tet2 encoding at TAG stop codons in BL21 E. coli strains, enabling reproducible expression of Tet2-proteins that quantitatively react with trans-cyclooctene (TCO) groups within 5 min at room temperature and physiological pH. The use of the BL21 derivative B95(DE3) minimizes premature truncation byproducts caused by incomplete suppression of TAG stop codons, which makes it possible to use more diverse protein construct designs. Here, using a superfolder green fluorescent protein construct as an example protein, we describe in detail a four-day process for encoding Tet2 with yields of ~200 mg per liter of culture. Additionally, a simple and fast diagnostic gel electrophoretic mobility shift assay is described to confirm Tet2-Et encoding and reactivity. Finally, strategies are discussed to adapt the protocol to alternative proteins of interest and optimize expression yields and reactivity for that protein. Key features • Protocol describes site-specific encoding of the tetrazine amino acid Tet2-Et into proteins for bioorthogonal, quantitative, and rapid attachment of trans-cyclooctene-containing labels. • Protocol uses auto-induction methods for the production Tet2-Et protein in E. coli. • This protocol focuses on Tet-protein expressions in BL21(DE3) and B95(DE3) strains, which take approximately 4 days to complete. • SDS-PAGE mobility shift assay using a strained TCO-PEG5000 (sTCO-PEG5000) reagent provides a simple, generalizable method for testing Tet-protein reactivity.

Utility of Guiding Catheter Extensions for Recanalization of Chronic Total Occlusions: A EuroCTO Club Expert Panel Report.

Guiding catheter extensions (GCEs) have become indispensable tools in the modern approach to percutaneous coronary intervention (PCI). The support offered during complex PCI of uncrossable, or tortuous lesions is particularly valuable in the setting of chronic total occlusions (CTO), both for conventional anterograde wire escalation and for anterograde or retrograde dissection and re-entry techniques. This EuroCTO consensus document describes the use of GCE during CTO recanalization and provides a practical guide to anatomies and techniques in which these devices are applicable. We describe the peculiar features of the most-used device and the practical technique for GCE delivery in standard PCI; further specific indications for antegrade and retrograde CTO PCI are discussed in a specific section. In the antegrade approach, the GCEs may be useful to increase support or facilitate antegrade dissection and re-entry techniques, while in the retrograde approach for reverse controlled antegrade and retrograde tracking, to increase retrograde support for gear delivery, for treatment of CTO in bifurcation and ipsilateral externalization with a single guide catheter. The last section of the paper describes GCE-related complications, challenges, limitations, and future perspectives.

Nanostructured N, S, and P-Doped Elaeagnus Angustifolia Gum-Derived Porous Carbon with Electrodeposited Silver for Enhanced Electrochemical Sensing of Acetaminophen.

Acetaminophen (N-acetyl-p-aminophenol, APAP) is regularly used for antipyretic and analgesic purposes. Overdose or long-term exposure to APAP could lead to liver damage and hepatotoxicity. In this study, the approach of enhanced electrochemical detection of APAP by nanostructured biomass carbon/silver was developed. Porous biomass carbon derived from Elaeagnus Angustifolia gum was prepared by pyrolysis with co-doping of electron-rich elements of nitrogen, sulfur, and phosphorus. The electrodeposition of silver onto a glassy carbon electrode modified with porous carbon could enhance the sensing signal towards APAP. Two linear ranges from 61 nM to 500 µM were achieved with a limit of detection of 33 nM. The developed GCE sensor has good anti-interference, stability, reproducibility, and human urine sample analysis performance. The silver-enhanced biomass carbon GCE sensor extends the application of biomass carbon, and its facile preparation approach could be used in constructing disposable sensing chips in the future.

Juvenile hormone receptor Methoprene tolerant: Functions and applications.

During the past 15years, after confirming Methoprene tolerant (Met) as a juvenile hormone (JH) receptor, tremendous progress has been made in understanding the function of Met in supporting JH signal transduction. Met role in JH regulation of development, including metamorphosis, reproduction, diapause, cast differentiation, behavior, im`munity, sleep and epigenetic modifications, have been elucidated. Met's Heterodimeric partners involved in performing some of these functions were discovered. The availability of JH response elements (JHRE) and JH receptor allowed the development of screening assays in cell lines and yeast. These screening assays facilitated the identification of new chemicals that function as JH agonists and antagonists. These new chemicals and others that will likely be discovered in the near future by using JH receptor and JHRE will lead to highly effective species-specific environmentally friendly insecticides for controlling pests and disease vectors.

K-Mer-Based Genome Size Estimation in Theory and Practice.

Recent advances in sequencing technologies have made genome sequencing of non-model organisms with very large and complex genomes possible. The data can be used to estimate diverse genome characteristics, including genome size, repeat content, and levels of heterozygosity. K-mer analysis is a powerful biocomputational approach with a wide range of applications, including estimation of genome sizes. However, interpretation of the results is not always straightforward. Here, I review k-mer-based genome size estimation, focusing specifically on k-mer theory and peak calling in k-mer frequency histograms. I highlight common pitfalls in data analysis and result interpretation, and provide a comprehensive overview on current methods and programs developed to conduct these analyses.

An Adaptive Early Stopping Technique for DenseNet169-Based Knee Osteoarthritis Detection Model.

Knee osteoarthritis (OA) detection is an important area of research in health informatics that aims to improve the accuracy of diagnosing this debilitating condition. In this paper, we investigate the ability of DenseNet169, a deep convolutional neural network architecture, for knee osteoarthritis detection using X-ray images. We focus on the use of the DenseNet169 architecture and propose an adaptive early stopping technique that utilizes gradual cross-entropy loss estimation. The proposed approach allows for the efficient selection of the optimal number of training epochs, thus preventing overfitting. To achieve the goal of this study, the adaptive early stopping mechanism that observes the validation accuracy as a threshold was designed. Then, the gradual cross-entropy (GCE) loss estimation technique was developed and integrated to the epoch training mechanism. Both adaptive early stopping and GCE were incorporated into the DenseNet169 for the OA detection model. The performance of the model was measured using several metrics including accuracy, precision, and recall. The obtained results were compared with those obtained from the existing works. The comparison shows that the proposed model outperformed the existing solutions in terms of accuracy, precision, recall, and loss performance, which indicates that the adaptive early stopping coupled with GCE improved the ability of DenseNet169 to accurately detect knee OA.

Sensitive detection of noradrenaline in human whole blood based on Au nanoparticles embedded vertically-ordered silica nanochannels modified pre-activated glassy carbon electrodes.

Sensitive determination of noradrenaline (NE), the pain-related neurotransmitters and hormone, in complex whole blood is of great significance. In this work, an electrochemical sensor was simply constructed on the pre-activated glassy carbon electrode (p-GCE) modified with vertically-ordered silica nanochannels thin film bearing amine groups (NH2-VMSF) and in-situ deposited Au nanoparticles (AuNPs). The simple and green electrochemical polarization was employed to pre-activate GCE to realize the stable binding of NH2-VMSF on the surface of electrode without the use of any adhesive layer. NH2-VMSF was conveniently and rapidly grown on p-GCE by electrochemically assisted self-assembly (EASA). With amine group as the anchor sites, AuNPs were in-situ electrochemically deposited on the nanochannels to improve the electrochemical signals of NE. Owing to signal amplification from gold nanoparticles, the fabricated AuNPs@NH2-VMSF/p-GCE sensor can achieve electrochemical detection of NE ranged from 50 nM to 2 µM and from 2 µM to 50 µM with a low limit of detection (LOD) of 10 nM. The constructed sensor exhibited high selectivity and can be easily regenerated and reused. Owing to the anti-fouling ability of nanochannel array, direct electroanalysis of NE in human whole blood was also realized.

A deep eutectic solvent-assisted electrochemical synthesis of TGA capped CdSe@Cu2Se core-shell quantum dots on the graphene-modified electrode as a catalytic platform for the determination of pyrazinamide.

A two-step and fast electrochemical approach for the synthesis of CdSe@ Cu2Se core-shell quantum dots is applied in the mixture of ethylene glycol-based deep eutectic solvent and 5% water as a green media to modify the graphene film-coated glassy carbon electrode for fabricating a sensitive surface. The quantum dots particles were systematically characterized by Energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, UV-visible and Fluorescence emission spectroscopy, transmission electron microscopy (TEM) and cyclic voltammetry (CV) techniques. The results show the existence of a second-order chemical reaction after occurring the electron transfer reaction for pyrazinamide. The CdSe@Cu2Se modified graphene-coated glassy carbon electrode was successfully used for the determination of pyrazinamide by differential pulse voltammetry method under the optimized conditions (pH = 2) in the range of 0.4-10 µM with a corresponding detection limit of 0.37 µM. The proposed modified sensor demonstrated high selectivity, reproducibility, stability in the pharmaceutical tablets, urine, and human blood serum and high recoveries in the range of 97.9-101.9% were obtained.