A novel turn-on fluorescence sensor based on the Nd (III) complex for the ultrasensitive detection of 6-mercaptopurine.

6-mercaptopurine (6MP) is a chemotherapeuticdrug widely used for treating inflammatory bowel diseases and several cancers. Nevertheless, determining and monitoring its concentration in the human body is highly important because over or under-doses of 6MP can lead to critical health issues. In this paper, we have developed a turn-on fluorescent probe for the determination of the anticancer drug 6-mercaptopurine (6-MP) based on coordination complex [Nd (Anth)3 (H2O)3]. [Nd (Anth)3 (H2O)3] has been synthesized through a simple precipitation process taking the stoichiometric ratio of Nd (III) nitrate hexahydrate and 2-aminobenzoic acid (2-ABA), commonly known as anthranilic acid (Anth). The synthesis and structure have been investigated and validated by different characterizations like UV-visible spectroscopy, FT-IR, HRMS, XPS, and SEM. The synthesized complex displayed excellent fluorescence properties, and the fluorescence intensity was enhanced with the addition of 6MP in the form of a [Fe (6MP)3]2+ mixed complex (Fe-6MP), which is formed by dissolving it in FeCl3. The fabricated sensors displayed the best linear response in a wide range of concentrations from 2.55 µM to 45.51 µM of 6MP. The lower limit of detection (LOD) of the developed sensor was found to be 0.26 µM with a linear correlation coefficient (R2) of 0.99. The synthesized probe gives an acceptable response for the sensing of 6MP in the presence of several interfering agents.

Vemurafenib Inhibits Acute and Chronic Enterovirus Infection by Affecting Cellular Kinase Phosphatidylinositol 4-Kinase Type IIIß.

Enteroviruses are one of the most abundant viruses causing mild to serious acute infections in humans and also contributing to chronic diseases like type 1 diabetes. Presently, there are no approved antiviral drugs against enteroviruses. Here, we studied the potency of vemurafenib, an FDA-approved RAF kinase inhibitor for treating BRAFV600E mutant-related melanoma, as an antiviral against enteroviruses. We showed that vemurafenib prevented enterovirus translation and replication at low micromolar dosage in an RAF/MEK/ERK-independent manner. Vemurafenib was effective against group A, B, and C enteroviruses, as well as rhinovirus, but not parechovirus or more remote viruses such as Semliki Forest virus, adenovirus, and respiratory syncytial virus. The inhibitory effect was related to a cellular phosphatidylinositol 4-kinase type IIIß (PI4KB), which has been shown to be important in the formation of enteroviral replication organelles. Vemurafenib prevented infection efficiently in acute cell models, eradicated infection in a chronic cell model, and lowered virus amounts in pancreas and heart in an acute mouse model. Altogether, instead of acting through the RAF/MEK/ERK pathway, vemurafenib affects the cellular PI4KB and, hence, enterovirus replication, opening new possibilities to evaluate further the potential of vemurafenib as a repurposed drug in clinical care. IMPORTANCE Despite the prevalence and medical threat of enteroviruses, presently, there are no antivirals against them. Here, we show that vemurafenib, an FDA-approved RAF kinase inhibitor for treating BRAFV600E mutant-related melanoma, prevents enterovirus translation and replication. Vemurafenib shows efficacy against group A, B, and C enteroviruses, as well as rhinovirus, but not parechovirus or more remote viruses such as Semliki Forest virus, adenovirus, and respiratory syncytial virus. The inhibitory effect acts through cellular phosphatidylinositol 4-kinase type IIIß (PI4KB), which has been shown to be important in the formation of enteroviral replication organelles. Vemurafenib prevents infection efficiently in acute cell models, eradicates infection in a chronic cell model, and lowers virus amounts in pancreas and heart in an acute mouse model. Our findings open new possibilities to develop drugs against enteroviruses and give hope for repurposing vemurafenib as an antiviral drug against enteroviruses.

Nanomolar inhibition of SARS-CoV-2 infection by an unmodified peptide targeting the prehairpin intermediate of the spike protein.

Variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) challenge currently available coronavirus disease 2019 vaccines and monoclonal antibody therapies through epitope change on the receptor binding domain of the viral spike glycoprotein. Hence, there is a specific urgent need for alternative antivirals that target processes less likely to be affected by mutation, such as the membrane fusion step of viral entry into the host cell. One such antiviral class includes peptide inhibitors, which block formation of the so-called heptad repeat 1 and 2 (HR1HR2) six-helix bundle of the SARS-CoV-2 spike (S) protein and thus interfere with viral membrane fusion. We performed structural studies of the HR1HR2 bundle, revealing an extended, well-folded N-terminal region of HR2 that interacts with the HR1 triple helix. Based on this structure, we designed an extended HR2 peptide that achieves single-digit nanomolar inhibition of SARS-CoV-2 in cell-based and virus-based assays without the need for modifications such as lipidation or chemical stapling. The peptide also strongly inhibits all major SARS-CoV-2 variants to date. This extended peptide is ∼100-fold more potent than all previously published short, unmodified HR2 peptides, and it has a very long inhibition lifetime after washout in virus infection assays, suggesting that it targets a prehairpin intermediate of the SARS-CoV-2 S protein. Together, these results suggest that regions outside the HR2 helical region may offer new opportunities for potent peptide-derived therapeutics for SARS-CoV-2 and its variants, and even more distantly related viruses, and provide further support for the prehairpin intermediate of the S protein.

Synergistic Block of SARS-CoV-2 Infection by Combined Drug Inhibition of the Host Entry Factors PIKfyve Kinase and TMPRSS2 Protease.

Repurposing FDA-approved inhibitors able to prevent infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could provide a rapid path to establish new therapeutic options to mitigate the effects of coronavirus disease 2019 (COVID-19). Proteolytic cleavages of the spike (S) protein of SARS-CoV-2, mediated by the host cell proteases cathepsin and TMPRSS2, alone or in combination, are key early activation steps required for efficient infection. The PIKfyve kinase inhibitor apilimod interferes with late endosomal viral traffic and through an ill-defined mechanism prevents in vitro infection through late endosomes mediated by cathepsin. Similarly, inhibition of TMPRSS2 protease activity by camostat mesylate or nafamostat mesylate prevents infection mediated by the TMPRSS2-dependent and cathepsin-independent pathway. Here, we combined the use of apilimod with camostat mesylate or nafamostat mesylate and found an unexpected ∼5- to 10-fold increase in their effectiveness to prevent SARS-CoV-2 infection in different cell types. Comparable synergism was observed using both a chimeric vesicular stomatitis virus (VSV) containing S of SARS-CoV-2 (VSV-SARS-CoV-2) and SARS-CoV-2. The substantial ∼5-fold or higher decrease of the half-maximal effective concentrations (EC50s) suggests a plausible treatment strategy based on the combined use of these inhibitors. IMPORTANCE Infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the coronavirus disease 2019 (COVID-2019) global pandemic. There are ongoing efforts to uncover effective antiviral agents that could mitigate the severity of the disease by controlling the ensuing viral replication. Promising candidates include small molecules that inhibit the enzymatic activities of host proteins, thus preventing SARS-CoV-2 entry and infection. They include apilimod, an inhibitor of PIKfyve kinase, and camostat mesylate and nafamostat mesylate, inhibitors of TMPRSS2 protease. Our research is significant for having uncovered an unexpected synergism in the effective inhibitory activity of apilimod used together with camostat mesylate or nafamostat mesylate.

A composite prepared from MoS2 quantum dots and silver nanoparticles and stimulated by mercury(II) is a robust oxidase mimetic for use in visual determination of cysteine.

MoS2 quantum dots were hydrothermally synthesized and utilized for the formation and stabilization of a nanocomposite with silver nanoparticles (AgNPs) in a single step. This composite was characterized by transmission electron microscopy and zeta potential measurements. It is found that this nanohybrid can be stimulated by mercury(II) ion and then exhibits excellent oxidase mimicking activity. The oxidase-like activity is demonstrated by the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2 that leads to the formation of a blue product. An assay was developed for determination of cysteine (Cys) at ultra-trace level because Cys inhibits the activity of the nanozyme via interaction with Hg(II). The Cys assay, best performed at a wavelength of 652 nm, works in the 1-100 µM concentration range and has a 0.82 µM detection limit. In addition, a portable Cys test kit is described that was applied to the determination of Cys in serum samples. The resulting colorations were compared with color chat wheel. The method is simple, rapid, cost-effective, and sensitive. Graphical abstractSchematic presentation of oxidase mimetic activity of the Hg@ MoS2-QDs-AgNPs and colorimetric sensing of Cys.