A Nanostructure Based Electrochemical Sensor for Square Wave Voltammetric Determination ofL-Cysteine in the Presence of High Concentration of Folic Acid

Copper-Catalyzed Domino-Double Annulation of o-Aminobenzamides with 2-Iodoisothiocyanates for the Synthesis of 12H-Benzo[4,5]thiazolo[2,3-b]quinazolin-12-ones

A facile and efficient copper-catalyzed domino-double annulation strategy was developed from easily accessible o-aminobenzamides and 2-iodoisothiocyanates, which affords a direct pathway for the synthesis of tetracyclic fused 12H-benzo[4,5]thiazolo[2,3-b]quinazolin-12-ones in moderate to good yields without the addition of ligands, bases, and external oxidants. The reaction involves a C-N bond cleavage and the formation of a C-N/C-S bond in one step with the advantages of using an inexpensive copper catalyst and easy operation. Mechanistic studies suggest that this transformation proceeds via intermolecular condensation of o-aminobenzamides with 2-iodoisothiocyanates, followed by an intramolecular Ullmann-type cross-coupling cyclization reaction.

Bioinspired thiazolo-[2,3-b] quinazolin-6-one derivatives as potent anti-cancer agents targeting EGFR: their biological evaluations and in silico assessment

Cancer is a challenging and second most deadly disease. The epidermal growth factor receptors (EGFRs) dimerize upon ligand bindings to the extracellular domain that intiates the downstream signaling cascades and activates intracellular kinase domain. Thus, activation of autophosphrylation through kinase domain results in metastasis, cell proliferation, and angiogenesis. In this study, we unravel the binding mechanism of newly synthesized thiazolo-[2,3-b] quinazolin-6-one and evaluate their anti-cancer activity against ovary and prostate carcinoma cell lines (OVCAR-3 and PC-3). Synthesized molecules exhibited promising anti-cancer activity against OVCAR-3 and PC-3 carcinoma cell lines with inhibitory concentrations ranging from 13.4 ± 0.43 to 23.6 ± 1.22 μM and 7.5 ± 0.62 to 67.5 ± 1.24 μM, respectively. These compounds induced apoptosis and resulted in cell cycle arrest at G1 and G2/M transition phases. Next, the nude mice models were taken to investigate the toxicity of the 4bi compound, and in vivo investigations revealed no effects upon examined organs (liver and kidney) treated at different concentrations. Moreover, the combined in silico approaches, molecular docking, molecular dynamics simulations, and MM/PBSA methods were performed to assess the binding affinity and stability of bioinspired synthesized congeners with the epidermal growth factor receptor tyrosine kinase (EGFR-TK). The free binding energy (ΔG_bind) of the 4bi molecule was found comparable to Erlotinib drug. The test molecule could be competent for further usage to determine its efficicacy in cancer therapeutics.

Electrochemical Amino Acid Sensing: A Review on Challenges and Achievements

The rapid growth of research in electrochemistry in the last decade has resulted in a significant advancement in exploiting electrochemical strategies for assessing biological substances. Among these, amino acids are of utmost interest due to their key role in human health. Indeed, an unbalanced amino acid level is the origin of several metabolic and genetic diseases, which has led to a great need for effective and reliable evaluation methods. This review is an effort to summarize and present both challenges and achievements in electrochemical amino acid sensing from the last decade (from 2010 onwards) to show where limitations and advantages stem from. In this review, we place special emphasis on five well-known electroactive amino acids, namely cysteine, tyrosine, tryptophan, methionine and histidine. The recent research and achievements in this area and significant performance metrics of the proposed electrochemical sensors, including the limit of detection, sensitivity, stability, linear dynamic range(s) and applicability in real sample analysis, are summarized and presented in separate sections. More than 400 recent scientific studies were included in this review to portray a rich set of ideas and exemplify the capabilities of the electrochemical strategies to detect these essential biomolecules at trace and even ultra-trace levels. Finally, we discuss, in the last section, the remaining issues and the opportunities to push the boundaries of our knowledge in amino acid electrochemistry even further.

A new class of fluorogenic thiazolo[2,3-b]quinazolinone receptor: selective detection towards mercury and hydrogen bisulfate ions in aqueous medium

A series of fluorophoric and structurally diverse thiazoloquinazoline derivatives were synthesized in a one-pot multicomponent cascade reaction using a microwave irradiation technique. The unique structural arrangement of the synthesized compounds encouraged us to design a new type of bioactive molecular receptor. This receptor interacts with HSO₄⁻ in 1 : 1 and Hg²⁺ in 1 : 2 binding stoichiometric ratios resulting in a change in fluorescence as well as absorption spectra in aqueous medium. The ion bonded receptor complex possibly enhances the fluorescence signal of the receptor via H-bonded complex formation with HSO₄⁻ ions and co-ordinate complex formation with Hg²⁺ ions.

Fluorophoric thiazoloquinazoline derivatives were synthesized under microwave assisted one-pot three-component cascade reaction. Owing to their unique structural arrangement, a new bioactive molecular receptor was developed for HSO⁴⁻ and Hg²⁺ ions.

Prediction and Understanding: Quantum Chemical Framework of Transition Metals Enclosed in a B12N12 Inorganic Nanocluster for Adsorption and Removal of DDT from the Environment

Emission of harmful pollutants from different sources into the environment is a major problem nowadays. Organochlorine pesticides such as DDT (C₁₄H₉Cl₅) are toxic, bio-accumulative, and regularly seen in water bodies, air, biota, and sediments. Various systems can be considered for minimizing the DDT (dichloro-diphenyl-trichloroethane) pollution. However, due to simplicity and acceptability, the adsorption method is the most popular method. Adsorption is gradually employed for the removal of both organic and inorganic pollutants found in soil and water. Thus, in this regard, efforts are being made to design inorganic nanoclusters (B₁₂N₁₂) encapsulated with late transition metals (Zn, Cu, Ni, Co, and Fe) for effective adsorption of DDT. In this context, detailed thermodynamics and quantum chemical study of all the designed systems have been carried out with the aid of density functional theory. The adsorption energy of DDT on metals cocooned in a nanocluster is found to be higher, and better adsorption energy values as compared to that of the pristine B₁₂N₁₂-DDT nanocluster have been reported. Further, analysis of the dipole moment, frontier molecular orbitals, molecular electrostatic potential plots, energy band gap, Q_NBO, and Fermi level suggested that the late-transition-metal-encapsulated inorganic B₁₂N₁₂ nanoclusters are efficient candidates for effective DDT adsorption. Lastly, the study of global descriptors of reactivity confirmed that the designed quantum mechanical systems are quite stable in nature with a good electrophilic index. Therefore, the recommendation has been made for these novel kinds of systems to deal with the development of DDT sensors.

Designing of Inorganic Al12N12 Nanocluster with Fe, Co, Ni, Cu and Zn Metals for Efficient Hydrogen Storage Materials

Hydrogen is considered as one of the attractive environmentally friendly materials with zero carbon emission. Hydrogen storage is still challenging for its use in various energy applications. That’s why hydrogen gained more and more attention to become a major fuel of today’s energy consumption. Therefore, nowadays, hydrogen storage materials are under extensive research. Herein, efforts are being devoted to design efficient systems which could be used for future hydrogen storage purposes. To this end, we have employed density functional theory (DFT) to optimize the geometries of the designed inorganic Al[Formula: see text]N[Formula: see text] nanoclusters with transition metals (Fe, Co, Ni, Cu and Zn). Various positions of metal encapsulated Al[Formula: see text]N[Formula: see text] are examined for efficient hydrogen adsorption. After adsorption of H2 on late transition metals encapsulated Al[Formula: see text]N[Formula: see text] nanocluster, different geometric parameters like frontier molecular orbitals, adsorption energies and nature bonding orbitals have been performed for exploring the potential of metal encapsulated for hydrogen adsorption. Moreover, molecular electrostatic potential (MEP) analysis was also performed in order to explore the different charge separation upon H2 adsorption on metals encapsulated Al[Formula: see text]N[Formula: see text] nanoclusters. Also, global indices of reactivity like ionization potential, electron affinity, electrophilic index, chemical softness and chemical hardness were also examined by using DFT. The adsorption energy results suggested encapsulation of late transition metals in Al[Formula: see text]N[Formula: see text] nanocage efficiently enhancing the adsorption capability of Al[Formula: see text]N[Formula: see text] for hydrogen adsorption. Results of all analysis suggested that our designed systems are efficient candidates for hydrogen adsorption. Thus, we recommended a novel kind of systems for hydrogen storage materials.

Two-dimensional FeP@C nanosheets as a robust oxidase mimic for fluorescence detection of cysteine and Cu2

In the past few years, the development of novel nanozymes with excellent performance has attracted increasing attention in biosensing. However, most of those nanozymes were found to possess peroxidase activity with the prerequisite of the presence of H2O2. In contrast, oxidase mimics can catalyze the oxidation of substrates without H2O2, delivering a higher signal-to-noise ratio than that of peroxidase mimics in practical applications. Herein, for the first time, two-dimensional (2D) nanosheets composed of iron phosphide embedded in a carbon matrix (FeP@C nanosheets) were found to demonstrate a robust oxidase-like property, different from those previously reported peroxidase mimics based on transition metal phosphides (TMPs). Based on this intriguing observation, the fluorescent substrate Amplex Red (AR) of peroxidase can be effectively oxidized by FeP@C nanosheets in the absence of H2O2. Benefiting from the oxidase-like enzymatic activity of the FeP@C nanosheets, a novel fluorescence sensing platform was developed for the detection of cysteine (Cys) and Cu2+. The outstanding performance of the 2D FeP@C nanosheets endows the proposed platform with superior sensitivity and selectivity compared to many previously reported approaches. Besides, the inherent features of simplicity, being label free, and low cost also allow this methodology to stand out among many other strategies, revealing its huge potential in practical analysis and detection applications.

Recent developments in voltammetric and amperometric sensors for cysteine detection

This review article aims to provide an overview of the recent advances in the voltammetric and amperometric sensing of cysteine (Cys). The introduction summarizes the important role of Cys as an essential amino acid, techniques for its sensing, and the utilization of electrochemical methods and chemically modified electrodes for its determination. The main section covers voltammetric and amperometric sensing of Cys based on glassy carbon electrodes, screen printed electrodes, and carbon paste electrodes, modified with various electrocatalytic materials. The conclusion section discusses the current challenges of Cys determination and the future perspectives.

Efficient Cu Decorated Inorganic B12P12 Nanoclusters for Sensing Toxic COCl2 Gas: A Detailed DFT Study

Gas sensing materials have been widely explored recently owing to their versatile environmental and agriculture monitoring applications. Phosgene (COCl2) is a toxic and harmful gas, therefore, a reliable and sensitive technique is required for monitoring its quantity in the atmosphere. In this study, pure as well as copper decorated B[Formula: see text]P[Formula: see text](Cu-BP) nanoclusters were analyzed using DFT method to investigate their specific potential for phosgene gas adsorption. Cu interaction resulted in three optimized geometries S1, S2 and S3 with interaction energies of [Formula: see text]234.52[Formula: see text]kJ/mol, [Formula: see text]214.59[Formula: see text]kJ/mol and [Formula: see text]266.45[Formula: see text]kJ/mol, respectively. In all these three cases, the COCl2 prefers to interact at the top of the cage. The phosgene molecule (COCl2) interacts with bare nanocage at a distance of 3.22[Formula: see text]Å with interaction energy of [Formula: see text]6.22[Formula: see text]kJ/mol, while the observed interaction energies of phosgene at Cu decorated B[Formula: see text]P[Formula: see text] are [Formula: see text]76.90[Formula: see text]kJ/mol, [Formula: see text]119.03[Formula: see text]kJ/mol and [Formula: see text]29.60[Formula: see text]kJ/mol, respectively. To observe the variations in electronic structure, fermi level, molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs), natural bonding orbital ([Formula: see text]), softness, hardness, chemical potential and electrophilicity are calculated before and after phosgene adsorption. Energy gap reduce significantly after phosgene adsorption from 2.31[Formula: see text]eV, 2.05[Formula: see text]eV and 2.46[Formula: see text]eV to 1.54[Formula: see text]eV, 1.57[Formula: see text]eV and 2.45[Formula: see text]eV, respectively. Results of all analysis suggested that decoration of Cu significantly enhanced the adsorption power of B[Formula: see text]P[Formula: see text] nan-cluster for COCl2 molecule. Therefore, the Cu-decorated B[Formula: see text]P[Formula: see text] nanocages are considered as potential candidates for application in COCl2 sensors.

Ultra-Thin SnS2-Pt Nanocatalyst for Efficient Hydrogen Evolution Reaction

Transition-metal dichalcogenides (TMDs) materials have attracted much attention for hydrogen evolution reaction (HER) as a new catalyst, but they still have challenges in poor stability and high reaction over-potential. In this study, ultra-thin SnS₂ nanocatalysts were synthesized by simple hydrothermal method, and low load of Pt was added to form stable SnS₂-Pt-3 (the content of platinum is 0.5 wt %). The synergistic effect between ultra-thin SnS₂ rich in active sites and individual dispersed Pt nanoclusters can significantly reduce the reaction barrier and further accelerate HER reaction kinetics. Hence, SnS₂-Pt-3 exhibits a low overpotential of 210 mV at the current density of 10 mA cm⁻². It is worth noting that SnS₂-Pt-3 has a small Tafel slope (126 mV dec⁻¹) in 0.5 M H₂SO₄, as well as stability. This work provides a new option for the application of TMDs materials in efficient hydrogen evolution reaction. Moreover, this method can be easily extended to other catalysts with desired two-dimensional materials.

Amperometric galectin-3 immunosensor-based gold nanoparticle-functionalized graphitic carbon nitride nanosheets and core-shell Ti-MOF@COFs composites

Antigen galectin-3 (GL-3), a member of β-galactoside proteins indicates cardiac fibrosis and is a significant biomarker for monitoring heart failure risk and death risk. In this study, a novel sensitive amperometric method for antigen GL-3 detection is developed based on gold nanoparticle-functionalized graphitic carbon nitride nanosheets (g-C₃N₄@Au NPs) as the sensor platform and Ti-based metal organic framework (Ti-MOF, NH₂-MIL-125)@covalent organic frameworks (COFs) composite for the signal amplification. The Ti-MOF@COF composite not only facilitates the penetration of antibody proteins into pore channels, but also the highly stable antigen-antibody interactions. The prepared sensor platform and signal amplification material are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) method, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The amperometric technique is utilized to achieve antigen GL-3 detection in plasma samples. The immunosensor demonstrates a wide linearity range (0.0001-20.0 ng mL^-1) and a low detection limit (0.025 pg mL^-1). Finally, the prepared immunosensor shows high stability and selectivity under optimum conditions.

Tandem Copper-Catalyzed Regioselective N-Arylation-Aza-Michael Addition: Synthesis of Tetracyclic 5H-Benzothiazolo[3,2-a]quinazoline Derivatives

A copper-catalyzed tandem process integrating regioselective N-arylation, followed by aza-Michael addition, is disclosed using 2-aminobenzothiazoles and ortho-halo cinnamic acid congeners. This process generated diverse tetracyclic 5H-benzothiazolo[3,2-a]quinazoline derivatives in moderate to good yields. The present tandem reaction appears to proceed through concomitant ring opening of 2-aminobenzothiazole and S-arylation to give the ortho-cyanamide-substituted diaryl thioether intermediate. The thus generated intermediate likely undergoes an unprecedented Truce-Smiles-type rearrangement involving S- to N-aryl migration, followed by reformation of the thiazole ring and intramolecular aza-Michael addition to furnish the title products.

The construction of fluorophoric thiazolo-[2,3-b]quinazolinone derivatives: a multicomponent domino synthetic approach

Acid-mediated one-pot domino reactions of substituted 2-amino thiazoles, substituted benzaldehydes and cyclic diketones have been developed for the synthesis of novel and architecturally unique thiazolo[2,3-b]quinazolinone derivatives under microwave irradiation. In this protocol, a series of thiazolo[2,3-b]quinazolinone derivatives have been synthesized and the excellent fluorescence behaviors of some of the molecules have been reported based on the incorporation of different electron-donating and electron-withdrawing substituents on the aryl moieties of the target molecules.

A library of unique fluorophoric thiazolo[2,3-b]quinazolinones were synthesized under acid catalyzed one pot microwave irradiation technique.

Simultaneous electrochemical determination of dopamine and epinephrine using gold nanocrystals capped with graphene quantum dots in a silica network

Gold nanocrystals (AuNCs) were synthesized by economical and green strategy in aqueous medium by using N[3(trimethoxysilyl)propyl]ethylenediamine (TMSPED) as both a reducing and stabilizing mediator to avoid the aggregation of gold nanocrystals. Then, the AuNCs were capped with graphene quantum dots (GQDs) using an ultrasonic method. The resulting nanocomposites of GQD-TMSPED-AuNCs were characterized by X-ray photoelectron, X-ray diffraction, Raman, UV-vis and FT-IR spectroscopies. The size and shape of the nanocomposites were confirmed by using transmission electron microscopy and atomic force microscopy. The GQD-TMSPED-AuNCs placed on a glassy carbon electrode enable simultaneous determination of dopamine (DA) and epinephrine (EP) with peak potentials at 0.21 and 0.30 V (vs. Ag/AgCl). The response is linear in the 5 nM - 2.1 μM (DA) and 10 nM - 4.0 μM (EP) concentration ranges, with detection limits of 5 and 10 nM, respectively. The sensor shows good selectivity toward DP and EP in the presence of other molecules, facilitating its rapid detection in practical applications. Graphical abstract Schematic representation of gold nanocrystals capped with graphene quantum dots in the modified electrodes for simultaneous detection of dopamine and epinephrine.

Metal-based Nanoparticles as Conductive Mediators in Electrochemical Sensors: A Mini Review

Background:

Modified electrodes are a new approach to improving the characteristics of the electrochemical sensors. The high conductivity and low charge transfer resistance are the major properties of new mediators for improving electrochemical sensors. Metal-based nanoparticles showed good electrical conductivity and can be selected as the suitbale mediator for modified electrodes.

Objective:

Recently, metal-based nanoparticles, such as Au nanoparticle, TiO2 nanoparticle, Fe3O4 nanoparticle and etc. were suggested as the suitable mediator for modification of solid electrodes. The high surface area and low charge transfer resistance of metal-based nanoparticles, suggested the exceptional intermediate in the electrochemical sensors. Here, we tried to consider these exceptional effects through reviewing some of the recently published works.

High ozone chemisorption by using metal–cluster complexes: a DFT study on the nickel-decorated B12P12 nanoclusters

In the present study, by using first-principle study within the density functional theory (DFT), we investigated the ozone (O3) chemisorption on the surface of pristine and nickel-decorated B12P12 nanoclusters. The important emphasis of this study is to follow changes in the electronic structures of the aforementioned nanoclusters upon adsorption of the O3 molecule. Although we found strong chemisorption of O3 on a pristine nanocluster (–282.7 kJ/mol), significant increases in adsorption were found by modifying the nanocluster’s surface. Firstly, we found there are three possible sites on the surface of the nanocluster for nickel (Ni) decoration. For each Ni-decorated nanocluster, we searched its potential for adsorption of O3 by using quantum chemical calculations. Depending on the location of decorated Ni, we found considerable increased values of O3 adsorption energy (–340.8, –376.8, and –382.4 kJ/mol). We carried out calculations by taking into account the values of adsorption energy, bond distance, dipole moment study, charge analysis, frontier orbital analysis, and density of states of all relaxed systems.

A concise construction of 12H-benzo[4,5]thiazolo[2,3-b]quinazolin-12-ones via an unusual TBHP/Na2CO3 promoted cascade oxidative cyclization and interrupted Dimroth rearrangement

An interrupted Dimroth rearrangement was merged into the oxidative cyclization between isatins and 2-haloaryl isothiocyanates, giving 12H-benzo[4,5]thiazolo[2,3-b]quinazolin-12-one derivatives.