Skeletal Editing: Ring Insertion for Direct Access to Heterocycles.

Skeleton editing has rapidly advanced as a synthetic methodology in recent years, significantly streamlining the synthesis process and gaining widespread acceptance in drug synthesis and development. This field encompasses diverse ring reactions, many of which exhibit immense potential in skeleton editing, facilitating the generation of novel ring skeletons. Notably, reactions that involve the cleavage of two distinct rings followed by the reformation of new rings through ring insertion play a pivotal role in the construction of novel ring skeletons. This article aims to compile and systematize this category of reactions, emphasizing the two primary reaction types and offering a thorough exploration of their associated complexities and challenges. Our endeavor is to furnish readers with comprehensive reaction strategies, igniting research interest and injecting fresh impetus into the advancement of this domain.

Synthesis, Structure and Antibacterial Activity of Two Novel Coordination Polymers Based on N,N'-bis(4-carbozvlbenzvl)-4-aminotoluene and Heterocyclic Ligand against S. aureus.

As the use of antibiotics increases, the increasing resistance of bacteria is the main reason for the reduced efficiency of antibacterial drugs, making the research of new antibacterial materials become new hot spot. In this article, two novel coordination polymers (CPs), namely, [Cd2(L)2(bibp)2]n (1) and [Ni(L)(bib)]n (2), where H2L = N,N'-bis(4-carbozvlbenzvl)-4-aminotoluene, bibp = 4,4'-bis(imidazol-1-yl)biphenyl, and bib = 1,3-bis(1-imidazoly)benzene, have been synthesized under solvothermal and hydrothermal condition. Structural clarification was performed through infrared spectrum and single-crystal X-ray diffraction analysis, while thermal analysis and XRD technology were used for the performance assessment of compounds 1 and 2. In addition, antibacterial performance experiments showed that compounds 1 and 2 have certain selectivity in their antibacterial properties and have good antibacterial properties against S. aureus. As the concentration of the compound increases, the inhibitory effect gradually strengthens, and when the concentration of the compound reaches 500 µg/mL and 400 µg/mL, the concentration of the S. aureus solution no longer increases and has been completely inhibited.

Theoretical exploration of the phenolic compounds' inhibition mechanism of heterocyclic aromatic amines in roasted beef patties by density functional theory.

The ability of spices (bay leaf, star anise, and red pepper) and their characteristic phenolic compounds (quercetin, kaempferol, and capsaicin) to inhibit Heterocyclic aromatic amines (HAAs) in roasted beef patties were compared. Density functional theory (DFT) was used to reveal phenolic compounds interacting with HAAs-related intermediates and free radicals to explore possible inhibitory mechanisms for HAAs. 3 % red chili and 0.03 % capsaicin reduced the total HAAs content by 57.09 % and 68.79 %, respectively. DFT demonstrated that this was due to the stronger interaction between capsaicin and the ß-carboline HAAs intermediate (Ebind = -32.95 kcal/mol). The interaction between quercetin and phenylacetaldehyde was found to be the strongest (Ebind = -17.47 kcal/mol). Additionally, DFT indicated that capsaicin reduced the carbonyl content by transferring hydrogen atoms (HAT) to eliminate HO·, HOO·, and carbon-centered alkyl radicals. This study provided a reference for the development of DFT in the control of HAAs.

A Comprehensive Update of Anti-COVID-19 Activity of Heterocyclic Compounds.

The Coronavirus disease 2019 (COVID-19) pandemic is one of the most considerable health problems across the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the major causative agent of COVID-19. The severe symptoms of this deadly disease include shortness of breath, fever, cough, loss of smell, and a broad spectrum of other health issues such as diarrhea, pneumonia, bronchitis, septic shock, and multiple organ failure. Currently, there are no medications available for coronavirus patients, except symptom-relieving drugs. Therefore, SARS-CoV-2 requires the development of effective drugs and specific treatments. Heterocycles are important constituents of more than 85% of the physiologically active pharmaceutical drugs on the market now. Several FDA-approved drugs have been reported including molnupiravir, remdesivir, ritonavir, oseltamivir, favipiravir, chloroquine, and hydroxychloroquine for the cure of COVID-19. In this study, we discuss potent anti-SARS-CoV-2 heterocyclic compounds that have been synthesized over the past few years. These compounds included; indole, piperidine, pyrazine, pyrimidine, pyrrole, piperazine, quinazoline, oxazole, quinoline, isoxazole, thiazole, quinoxaline, pyrazole, azafluorene, imidazole, thiadiazole, triazole, coumarin, chromene, and benzodioxole. Both in vitro and in silico studies were performed to determine the potential of these heterocyclic compounds in the fight against various SARS-CoV-2 proteins.

Applications of Pyrrole and Pyridine-based Heterocycles in Cancer Diagnosis and Treatment.

BACKGROUND: The escalation of cancer worldwide is one of the major causes of economy burden and loss of human resources. According to the American Cancer Society, there will be 1,958,310 new cancer cases and 609,820 projected cancer deaths in 2023 in the United States. It is projected that by 2040, the burden of global cancer is expected to rise to 29.5 million per year, causing a death toll of 16.4 million. The hemostasis regulation by cellular protein synthesis and their targeted degradation is required for normal cell growth. The imbalance in hemostasis causes unbridled growth in cells and results in cancer. The DNA of cells needs to be targeted by chemotherapeutic agents for cancer treatment, but at the same time, their efficacy and toxicity also need to be considered for successful treatment. OBJECTIVE: The objective of this study is to review the published work on pyrrole and pyridine, which have been prominent in the diagnosis and possess anticancer activity, to obtain some novel lead molecules of improved cancer therapeutic. METHODS: A literature search was carried out using different search engines, like Sci-finder, Elsevier, ScienceDirect, RSC etc., for small molecules based on pyrrole and pyridine helpful in diagnosis and inducing apoptosis in cancer cells. The research findings on the application of these compounds from 2018-2023 were reviewed on a variety of cell lines, such as breast cancer, liver cancer, epithelial cancer, etc. Results: In this review, the published small molecules, pyrrole and pyridine and their derivatives, which have roles in the diagnosis and treatment of cancers, were discussed to provide some insight into the structural features responsible for diagnosis and treatment. The analogues with the chromeno-furo-pyridine skeleton showed the highest anticancer activity against breast cancer. The compound 5-amino-N-(1-(pyridin-4- yl)ethylidene)-1H-pyrazole-4-carbohydrazides was highly potent against HEPG2 cancer cell. Redaporfin is used for the treatment of cholangiocarcinoma, biliary tract cancer, cisplatin-resistant head and neck squamous cell carcinoma, and pigmentation melanoma, and it is in clinical trials for phase II. These structural features present a high potential for designing novel anticancer agents for diagnosis and drug development. CONCLUSION: Therefore, the N- and C-substituted pyrrole and pyridine-based novel privileged small Nheterocyclic scaffolds are potential molecules used in the diagnosis and treatment of cancer. This review discusses the reports on the synthesis of such molecules during 2018-2023. The review mainly discusses various diagnostic techniques for cancer, which employ pyrrole and pyridine heterocyclic scaffolds. Furthermore, the anticancer activity of N- and C-substituted pyrrole and pyridine-based scaffolds has been described, which works against different cancer cell lines, such as MCF-7, A549, A2780, HepG2, MDA-MB-231, K562, HT- 29, Caco-2 cells, Hela, Huh-7, WSU-DLCL2, HCT-116, HBL-100, H23, HCC827, SKOV3, etc. This review will help the researchers to obtain a critical insight into the structural aspects of pyrrole and pyridine-based scaffolds useful in cancer diagnosis as well as treatment and design pathways to develop novel drugs in the future.

Evaluation of antimicrobial and non-steroidal anti-inflammatory treatments for BRD on health and welfare in fattening bulls: a cross-sectional study.

Our study aimed to evaluate the effect of different treatments for BRD on health and welfare in fattening bulls. A total of 264 bulls were enrolled. Welfare was assessed on day 2 (T0) and day 15 (T1) after arrival. A decrease in the welfare level was observed from T0 to T1. All bulls were inspected clinically at T0 and T1 revealing an increase of skin lesions and lameness in T1. In both periods, a high incidence of respiratory disease was observed. A prevalence of 79.55% and 95.45% of Mycoplasma bovis using RT-PCR and culture at T0 and T1 respectively was observed. Blood samples were collected for haematology at T0 and T1. At T0, 36 animals were individually treated for BRD with an antimicrobial (IT), 54 received a metaphylactic treatment with tulathromycin (M), 150 received a metaphylactic treatment with tulathromycin plus a second antimicrobial (M + IT) whereas 24 were considered healthy and therefore not treated (NT). Additionally, 128 were treated with a non-steroid anti-inflammatory (NSAID). Neutrophils of M + IT were significantly higher than groups NT and M and the lymphocytes of M + IT were significantly lower than that of IT. White blood cells, neutrophils and N/L ratio of animals treated with an NSAID was significantly higher than that not treated. Lung inspection of 172 bulls at the abattoir indicated that 92.43% presented at least one lung lesion. A statistically significant effect of the NSAID treatment on the lung lesions was observed. Our findings indicate that BRD was a major welfare and health concern and evidence the difficulties of antimicrobial treatment of M. bovis.

Indole as a Versatile Building Block in Cycloaddition Reactions: Synthesis of Diverse Heterocyclic Frameworks.

Indole, a ubiquitous and structurally versatile aromatic compound, has emerged as a key player in the synthesis of diverse heterocyclic frameworks via cycloaddition reactions. These reactions are completely atom-economical and, hence, are considered as green reactions. This review article provides a comprehensive overview of the pivotal role played by indole in the construction of complex and biologically relevant heterocyclic compounds. Here we explore the chemistry of indole-based cycloadditions, highlighting their synthetic utility in accessing a wide array of heterocyclic architectures, including cyclohepta[b]indoles, tetrahydrocarbazoles, tetrahydroindolo[3,2-c]quinoline, and indolines, among others. Additionally, we discuss the mechanistic insights that underpin these transformations, emphasizing the strategic importance of indole as a building block. The content of this article will certainly encourage the readers to explore more work in this area.

Studies on the Thermal Decomposition Course of Nitrogen-Rich Heterocyclic Esters as Potential Drug Candidates and Evaluation of Their Thermal Stability and Properties.

Drug candidates must undergo thermal evaluation as early as possible in the preclinical phase of drug development because undesirable changes in their structure and physicochemical properties may result in decreased pharmacological activity or enhanced toxicity. Hence, the detailed evaluation of nitrogen-rich heterocyclic esters as potential drug candidates, i.e., imidazolidinoannelated triazinylformic acid ethyl esters 1-3 (where R1 = 4-CH3 or 4-OCH3 or 4-Cl, and R2 = -COOC2H5) and imidazolidinoannelated triazinylacetic acid methyl esters 4-6 (where R1 = 4-CH3 or 4-OCH3 or 4-Cl, and R2 = -CH2COOCH3)-in terms of their melting points, melting enthalpy values, thermal stabilities, pyrolysis, and oxidative decomposition course-has been carried out, using the simultaneous thermal analysis methods (TG/DTG/DSC) coupled with spectroscopic techniques (FTIR and QMS). It was found that the melting process (documented as one sharp peak related to the solid-liquid phase transition) of the investigated esters proceeded without their thermal decomposition. It was confirmed that the melting points of the tested compounds increased in relation to R1 and R2 as follows: 2 (R1 = 4-OCH3; R2 = -COOC2H5) < 6 (R1 = 4-Cl; R2 = -CH2COOCH3) < 5 (R1 = 4-OCH3; R2 = -CH2COOCH3) < 3 (R1 = 4-Cl; R2 = -COOC2H5) < 1 (R1 = 4-CH3; R2 = -COOC2H5) < 4 (R1 = 4-CH3; R2 = -CH2COOCH3). All polynitrogenated heterocyclic esters proved to be thermally stable up to 250 °C in inert and oxidising conditions, although 1-3 were characterised by higher thermal stability compared to 4-6. The results confirmed that both the pyrolysis and the oxidative decomposition of heterocyclic ethyl formates/methyl acetates with para-substitutions at the phenyl moiety proceed according to the radical mechanism. In inert conditions, the pyrolysis process of the studied molecules occurred with the homolytic breaking of the C-C, C-N, and C-O bonds. This led to the emission of alcohol (ethanol in the case of 1-3 or methanol in the case of 4-6), NH3, HCN, HNCO, aldehydes, CO2, CH4, HCl, aromatics, and H2O. In turn, in the presence of air, cleavage of the C-C, C-N, and C-O bonds connected with some oxidation and combustion processes took place. This led to the emission of the corresponding alcohol depending on the analysed class of heterocyclic esters, NH3, HCN, HNCO, aldehydes, N2, NO/NO2, CO, CO2, HCl, aromatics, and H2O. Additionally, after some biological tests, it was proven that all nitrogen-rich heterocyclic esters-as potential drug candidates-are safe for erythrocytes, and some of them are able to protect red blood cells from oxidative stress-induced damage.

An all-in-one tetrazine reagent for cysteine-selective labeling and bioorthogonal activable prodrug construction.

The prodrug design strategy offers a potent solution for improving therapeutic index and expanding drug targets. However, current prodrug activation designs are mainly responsive to endogenous stimuli, resulting in unintended drug release and systemic toxicity. In this study, we introduce 3-vinyl-6-oxymethyl-tetrazine (voTz) as an all-in-one reagent for modular preparation of tetrazine-caged prodrugs and chemoselective labeling peptides to produce bioorthogonal activable peptide-prodrug conjugates. These stable prodrugs can selectively bind to target cells, facilitating cellular uptake. Subsequent bioorthogonal cleavage reactions trigger prodrug activation, significantly boosting potency against tumor cells while maintaining exceptional off-target safety for normal cells. In vivo studies demonstrate the therapeutic efficacy and safety of this prodrug design approach. Given the broad applicability of functional groups and labeling versatility with voTz, we foresee that this strategy will offer a versatile solution to enhance the therapeutic range of cytotoxic agents and facilitate the development of bioorthogonal activatable biopharmaceuticals and biomaterials.

Novel Enzyme-Assisted Recycle Amplification Strategy for Tetracycline Detection Based on Oxidized Single-Walled Carbon Nanohorns.

In this study, oxidized single-walled carbon nanohorns (oxSWCNHs) were prepared using nitric acid oxidation and subsequently combined with 3'6-carboxyfluorescein through charge transfer to prepare fluorescent probes. These oxSWCNHs were used to quench fluorogen signals at short distances and dissociate ssDNA using cryonase enzymes. We established a method for rapidly detecting tetracycline (TC) in complex samples based on the amplification of cryonase enzyme signals. After optimizing the experimental conditions, our method showed a detection limit of 5.05 ng/mL, with good specificity. This method was used to determine the TC content in complex samples, yielding a recovery rate of 90.0-103.3%. This result validated the efficacy of our method in detecting TC content within complex samples.

Development of a 99mTc-labeled tetrazine for pretargeted SPECT imaging using an alendronic acid-based bone targeting model.

Pretargeting, which is the separation of target accumulation and the administration of a secondary imaging agent into two sequential steps, offers the potential to improve image contrast and reduce radiation burden for nuclear imaging. In recent years, the tetrazine ligation has emerged as a promising approach to facilitate covalent pretargeted imaging due to its unprecedented kinetics and bioorthogonality. Pretargeted bone imaging with TCO-modified alendronic acid (Aln-TCO) is an attractive model that allows the evaluation of tetrazines in healthy animals without the need for complex disease models or targeting regimens. Recent structure-activity relationship studies of tetrazines evaluated important parameters for the design of potent tetrazine-radiotracers for pretargeted imaging. However, limited information is available for 99mTc-labeled tetrazines. In this study, four tetrazines intended for labeling with fac-[99mTc(OH2)3 (CO)3]+ were synthesized and evaluated using an Aln-TCO mouse model. 3,6-bis(2-pyridyl)-1,2,4,5-Tz without additional linker showed higher pretargeted bone uptake and less background activity compared to the same scaffold with a PEG8 linker or 3-phenyl-1,2,4,5-Tz-based compounds. Additionally, improved bone/blood ratios were observed in pretargeted animals compared to animals receiving directly labeled Aln-TCO. The results of this study implicate 3,6-bis(2-pyridyl)-1,2,4,5-Tz as a promising scaffold for potential 99mTc-labeled tetrazines.

Innovative approaches to Alzheimer's therapy: Harnessing the power of heterocycles, oxidative stress management, and nanomaterial drug delivery system.

Alzheimer's disease (AD) presents a complex pathology involving amyloidogenic proteolysis, neuroinflammation, mitochondrial dysfunction, and cholinergic deficits. Oxidative stress exacerbates AD progression through pathways like macromolecular peroxidation, mitochondrial dysfunction, and metal ion redox potential alteration linked to amyloid-beta (Aß). Despite limited approved medications, heterocyclic compounds have emerged as promising candidates in AD drug discovery. This review highlights recent advancements in synthetic heterocyclic compounds targeting oxidative stress, mitochondrial dysfunction, and neuroinflammation in AD. Additionally, it explores the potential of nanomaterial-based drug delivery systems to overcome challenges in AD treatment. Nanoparticles with heterocyclic scaffolds, like polysorbate 80-coated PLGA and Resveratrol-loaded nano-selenium, show improved brain transport and efficacy. Micellar CAPE and Melatonin-loaded nano-capsules exhibit enhanced antioxidant properties, while a tetra hydroacridine derivative (CHDA) combined with nano-radiogold particles demonstrates promising acetylcholinesterase inhibition without toxicity. This comprehensive review underscores the potential of nanotechnology-driven drug delivery for optimizing the therapeutic outcomes of novel synthetic heterocyclic compounds in AD management. Furthermore, the inclusion of various promising heterocyclic compounds with detailed ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) data provides valuable insights for planning the development of novel drug delivery treatments for AD.

Tetrazole derivatives in the management of neurological disorders: Recent advances on synthesis and pharmacological aspects.

Neurological disorders are the leading cause of a large number of mortalities and morbidities. Nitrogen heterocyclic compounds have been pivotal in exhibiting wide array of therapeutic applications. Among them, tetrazole is a ubiquitous class of organic heterocyclic compounds that have attracted much attention because of its unique structural and chemical properties, and a wide range of pharmacological activities comprising anti-convulsant effect, antibiotic, anti-allergic, anti-hypertensive to name a few. Owing to significant chemical and biological properties, the present review aimed at highlighting the recent advances in tetrazole derivatives with special emphasis on their role in the management of neurological diseases. Besides, in-depth structure-activity relationships, molecular docking studies, and associated modes of action of tetrazole derivatives evident in in vitro, in vivo preclinical, and clinical studies have been discussed.

[Fe(NCMe)6](BF4)2 is a bifunctional catalyst for styrene aziridination by nitrene transfer and heterocycle expansion by subsequent dipolar insertion.

The solvated iron(II) salt [Fe(NCMe)6](BF4)2 (Me = methyl) is shown to be a bifunctional catalyst with respect to aziridination of styrene. The salt serves as an active catalyst for nitrene transfer from PhINTs to styrene to form 2-phenyl-N-tosylaziridine (Ph = phenyl; Ts = tosyl, -S{O}2-p-C6H4Me). The iron(II) salt also acts as a Lewis acid in non-coordinating CH2Cl2 solution, to catalyze heterolytic CN bond cleavage of the aziridine and insertion of dipolarophiles. The 1,3-zwitterionic intermediate is presumably supported by interaction of the metal dication with the anion, and by resonance stabilization of the carbocation. Nucleophilic dipolarophiles then insert to give a five-membered heterocyclic ring. The result is a two-step cycloaddition, formally [2 + 1 + 2], that is typically regiospecific, but not stereospecific. This reaction mechanism was confirmed by conducting a series of one-step, [3 + 2] additions of unsaturated molecules into pre-formed 2-phenyl-N-tosylaziridine, also catalyzed by [Fe(NCMe)6](BF4)2. Relevant substrates include styrenes, carbonyl compounds and alkynes. These yield five-membered heterocylic rings, including pyrrolidines, oxazolidines and dihydropyrroles, respectively. The reaction scope appears limited only by the barrier to formation of the dipolar intermediate, and by the nucleophilicity of the captured dipolarophile. The bifunctionality of an inexpensive, earth-abundant and non-toxic catalyst suggests a general strategy for one-pot construction of heterocyclic rings, as demonstrated specifically for pyrrolidine ring formation.

Al18F-NOTA-Octreotide outperforms 18F-FDG in identifying rare renal metastases from pancreatic neuroendocrine tumor.

We presented a case involving a 56-year-old man who had been experiencing shoulder and back pain for over a year, with extensive bone metastases revealed by a bone scan. To identify the primary source of these issues, the patients underwent a fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scan, which indicated moderate uptake in the right renal soft mass and low uptake in multiple osteolytic lesions. Pathological examination and immunohistochemical staining of the renal mass supported the diagnosis of neuroendocrine tumors. Subsequently, a novel somatostatin receptor imaging agent, Al18F-NOTA-octreotide (18F-OC), was performed to further investigate the source of metastatic lesions and to stage the tumor. The 18F-OC scan revealed a high-uptake lesion in the pancreatic head, as well as additional lymph node and bone metastases lesions. Compared to 18F-FDG, the 18F-OC demonstrated superior imaging capabilities and a significantly higher tumor-to-background ratio in neuroendocrine neoplasms, which contributed to improving the staging and treatment management.

Defective UiO-66/cellulose nanocomposite aerogel for the adsorption of heterocyclic aromatic amines.

Heterocyclic aromatic amines (HAAs), arising as chemical derivatives during the high-temperature culinary treatment of proteinaceous comestibles, exhibit notable carcinogenic potential. In this paper, a composite aerogel (AGD-UiO-66) with high-capacity and fast adsorption of HAAs was made with anchoring defective UiO-66 (D-UiO-66) mediated by lauric acid on the backbone of cellulose nanofibers (CNF). AGD-UiO-66 with hierarchical porosity reduced the mass transfer efficiency for the adsorption of HAAs and achieved high adsorption amount (0.84-1.05 µmol/g) and fast adsorption (15 min). The isothermal adsorption model demonstrated that AGD-UiO-66 belonged to a multilayer adsorption mechanism for HAAs. Furthermore, AGD-UiO-66 was successfully used to adsorb 12 HAAs in different food (roasted beef, roasted pork, roasted salmon and marinade) with high recoveries of 94.65%-104.43%. The intrinsic potential of AGD-UiO-66 demonstrated that it could be widely applicable to the adsorption of HAAs in foods.

TYK2 inhibition with deucravacitinib ameliorates erosive oral lichen planus.

Erosive oral lichen planus (OLP) is a challenging disease. This T cell driven disorder frequently shows a treatment unresponsive course and strongly limits patients' quality of life. The disease lacks FDA or EMA approved drugs for its treatment and the efficacy of the commonly administered treatments (i.e. topical and systemic steroids, steroid sparing agents) is often only partial. Although the etiopathogenesis of the disease still needs to be fully elucidated, recent advances helped to identify interferon-É£ (IFN-É£) as a pivotal cytokine in OLP pathogenesis, thus making the interference with its signalling a therapeutic target. Janus kinase (JAK) inhibitors therefore gained relevance for their inhibitory effect on IFN-É£ signalling. While some drugs such as abrocitinib, upadacitinib, tofacitinib directly interfere with IFN-É£ signalling through blockade of JAK1 and/or JAK2, deucravacitinib, a selective TYK-2 inhibitor indirectly interferes on IFN-É£ activation through interference with interleukin (IL)-12, a potent promotor for Th1/IFN-É£ responses. This mechanism of action makes deucravacitinib a candidate drug for the treatment of OLP. Here we provide initial evidence that deucravacitinib 6 mg daily has a beneficial effect in three patients with oral OLP.

In-situ growth of metal-organic frameworks on cellulose nanofiber aerogels for rapid adsorption of heterocyclic aromatic amines.

Heterocyclic aromatic amines (HAAs) are the main carcinogens produced during thermal processing of protein-rich foods. In this paper, a composite aerogel (TOCNFCa) with a stabilized dual-network structure was prepared via a template for the in-situ synthesis of UiO-66 on cellulose for the adsorption of HAAs in food. The dual-network structure of TOCNFCa provides the composite aerogel with excellent wet strength, maintaining excellent compressive properties. With the in-situ grown UiO-66 content up to 71.89 wt%, the hierarchical porosity endowed TOCNFCa@UiO-66 with the ability to rapidly adsorb HAAs molecules with high capacity (1.44-5.82 µmol/g). Based on excellent thermal stability, adsorption capacity and anti-interference, TOCNFCa@UiO-66 achieved satisfactory recoveries of HAAs in the boiled marinade, which is faster and more economical than the conventional SPE method. Moreover, TOCNFCa@UiO-66 could maintain 84.55 % of the initial adsorption capacity after 5 times of reuse.

Bis-tridentate Iridium(III) Complex with the N-Heterocyclic Carbene Ligand as a Novel Efficient Electrochemiluminescence Emitter for the Sandwich Immunoassay of the HHV-6A Virus.

Human herpesvirus type 6A (HHV-6A) can cause a series of immune and neurological diseases, and the establishment of a sensitive biosensor for the rapid detection of HHV-6A is of great significance for public health and safety. Herein, a bis-tridentate iridium complex (BisLT-Ir-NHC) comprising the N-heterocyclic carbene (NHC) ligand as a novel kind of efficient ECL luminophore has been unprecedently reported. Based on its excellent ECL properties, a new sensitive ECL-based sandwich immunosensor to detect the HHV-6A virus was successfully constructed by encapsulating BisLT-Ir-NHC into silica nanoparticles and embellishing ECL sensing interface with MXene@Au-CS. Notably, the immunosensor illustrated in this work not only had a wide linear range of 102 to 107 cps/µL but also showed outstanding recoveries (98.33-105.11%) in real human serum with an RSD of 0.85-3.56%. Undoubtedly, these results demonstrated the significant potential of the bis-tridentate iridium(III) complex containing an NHC ligand in developing ECL-based sensitive analytical methods for virus detection and exploring novel kinds of efficient iridium-based ECL luminophores in the future.

Heterocyclic fluorescent Schiff base chemosensors for the detection of Fe(III) and Cu(II) ions.

Two new Schiff bases were synthesized from 1-(2,4-dihydroxyphenyl)ethanone and pyridine derivatives. Both compounds were characterized using infrared, UV-Vis., 1H NMR, 13C NMR and mass spectral studies. Density functional theory (DFT) calculations were performed for both the Schiff bases with 6-31G(d, p) as the basis set. Vibrational frequencies calculated using the theoretical method were in good agreement with the experimental values. Both the Schiff bases were highly fluorescent in nature. The cation-recognizing profile of the compounds was investigated in aqueous methanol medium. The Schiff base 4-(1-(pyridin-4-ylimino)ethyl)benzene-1,3-diol (PYEB) was found to interact with Fe(III) and Cu(II) ions, whereas the Schiff base 4,4'-((pyridine-2,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (PDEB) was found to detect Cu(II) ions. The mechanism of recognition was established as combined excited state intramolecular proton transfer (ESIPT)-chelation-enhanced fluorescence (CHEF) effect and chelation-enhanced quenching (CHEQ) process for the detection of Fe(III) and Cu(II) ions, respectively. The stability constant of the metal complexes formed during the sensing process was determined. The limit of detection for Fe(III) and Cu(II) ions with respect to Schiff base PYEB was found to be 1.64 × 10-6 and 2.16 × 10-7 M, respectively. With respect to Schiff base PDEB, the limit of detection for Cu(II) ion was found to be 4.54 × 10-4 M. The Cu(II) ion sensing property of the Schiff base PDEB was applied in bioimaging studies for the detection of HeLa cells.