Antiviral activity of chitosan nanoparticles encapsulating silymarin (Sil-CNPs) against SARS-CoV-2 (in silico and in vitro study).

To develop a specific treatment against COVID-19, we investigated silymarin-chitosan nanoparticles (Sil-CNPs) as an antiviral agent against SARS-CoV-2 using in silico and in vitro approaches. Docking of Sil and CNPs was carried out against SARS-CoV-2 spike protein using AutoDock Vina. CNPs and Sil-CNPs were prepared by the ionic gelation method and characterized by TEM, FT-IR, zeta analysis, and the membrane diffusion method to determine the drug release profile. Cytotoxicity was tested on both Vero and Vero E6 cell lines using the MTT assay. Minimum binding energies with spike protein and ACE2 were -6.6, and -8.0 kcal mol-1 for CNPs, and -8.9, and -9.7 kcal mol-1 for Sil, respectively, compared to -6.6 and -8.4 kcal mol-1 respectively for remdesivir (RMV). CNPs and Sil-CNPs were prepared at sizes of 29 nm and 82 nm. The CC50 was 135, 35, and 110 µg mL-1 for CNPs, Sil, and Sil-CNPs, respectively, on Vero E6. The IC50 was determined at concentrations of 0.9, 12 and 0.8 µg mL-1 in virucidal/replication assays for CNPs, Sil, and Sil-CNPs respectively using crystal violet. These results indicate antiviral activity of Sil-CNPs against SARS-CoV-2.

Inhibition of SARS-CoV-2 spike protein entry using biologically modified polyacrylonitrile nanofibers: in vitro study towards specific antiviral masks.

With the increase of the contagiousness rates of Coronavirus disease (COVID-19), new strategies are needed to halt virus spread. Blocking virus entry by capturing its spike (S) protein is one of the effective approaches that could help in eliminating or reducing transmission rate of viruses. Herein, we aim to develop a nanofiber-based filter for protective face masks, composed of polyacrylonitrile (PAN) nanofibers (NFs)-loaded with Angiotensin Converting Enzyme-2 (ACE-2) for capturing the spike protein of severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) and blocking its entry. Docking simulations were performed to evaluate interactions of PAN with target proteins of both SARS-CoV-2 and Human Adenovirus type 5 (ADV-5) which was used as an in vitro model of human respiratory viruses. Scanning electron microscopy (SEM) and Fourier transformed infrared (FT-IR) spectroscopy was employed to investigate the surface morphology and to analyze the functional groups of the NFs, respectively. The mechanical properties of the electrospun NFs were investigated, according to which the tensile strengths of PAN and modified PAN NFs were 4.9 ± 1.2 GPa and 4.5 GPa. Additionally, elongations at break were 25 ± 2.5% to 24 ± 1.48% for PAN and modified PAN NFs. The tensile strength test showed good mechanical characteristics of the NFs. The ACE-2-loaded NFs were shown to be safe, with promising antiviral activity towards ADV-5. Meanwhile, a binding affinity study between the spike protein and ACE-2 was performed and the dissociation constant (K D) was found to be 1.1 nM. Accordingly, the developed antiviral filters have a potential role to stand as a base for combating various human respiratory viruses.

Zinc Oxide Nanoparticle-Loaded Electrospun Polyvinylidene Fluoride Nanofibers as a Potential Face Protector against Respiratory Viral Infections.

ZnO-NPs loaded polyvinylidene fluoride (PVDF) composite nanofibers were fabricated by electrospinning and optimized using different concentrations (0, 2, and 5 wt %) of ZnO-NPs. Characterization techniques, for example, FTIR, SEM, XRD, and tensile strength analysis were performed to analyze the composite nanofibers. Molecular docking calculations were performed to evaluate the binding affinity of PVDF and ZnO@PVDF against the hexon protein of adenovirus (PDB ID: 6CGV). The cytotoxicity of tested materials was evaluated using MTT assay, and nontoxic doses subjected to antiviral evaluation against human adenovirus type-5 as a human respiratory model were analyzed using quantitative polymerase chain reaction assay. IC50 values were obtained at concentrations of 0, 2, and 5% of ZnO-loaded PVDF; however, no cytotoxic effect was detected for the nanofibers. In 5% ZnO-loaded PVDF nanofibers, both the viral entry and its replication were inhibited in both the adsorption and virucidal antiviral mechanisms, making it a potent antiviral filter/mask. Therefore, ZnO-loaded PVDF nanofiber is a potentially prototyped filter embedded in a commercial face mask for use as an antiviral mask with a pronounced potential to reduce the spreading of infectious respiratory diseases, for example, COVID-19 and its analogues.

Facile deposition of palladium oxide (PdO) nanoparticles on CoNi2S4microstructures towards enhanced oxygen evolution reaction.

Strong demand for renewable energy resources and clean environments have inspired scientists and researchers across the globe to carry out research activities on energy provision, conversion, and storage devices. In this context, development of outperform, stable, and durable electrocatalysts has been identified as one of the major objectives for oxygen evolution reaction (OER). Herein, we offer facile approach for the deposition of few palladium oxide (PdO) nanoparticles on the cobalt-nickel bi-metallic sulphide (CoNi2S4) microstructures represented as PdO@ CoNi2S4using ultraviolet light (UV) reduction method. The morphology, crystalline structure, and chemical composition of the as-prepared PdO@ CoNi2S4composite were probed through scanning electron microscopy, powder x-ray diffraction, high resolution transmission electron microscopy, energy dispersive spectroscopy and x-ray photoelectron spectroscopy techniques. The combined physical characterization results revealed that ultraviolet light (UV) light promoted the facile deposition of PdO nanoparticles of 10 nm size onto the CoNi2S4and the fabricated PdO@ CoNi2S4composite has a remarkable activity towards OER in alkaline media. Significantly, it exhibited a low onset potential of 1.41 V versus reversible hydrogen electrode (RHE) and a low overpotential of 230 mV at 10 mA cm-2. Additionally, the fabricated PdO@ CoNi2S4composite has a marked stability of 45 h. Electrochemical impedance spectroscopy has shown that the PdO@CoNi2S4composite has a low charge transfer resistance of 86.3 Ohms, which favours the OER kinetics. The PdO@ CoNi2S4composite provided the multiple number of active sites, which favoured the enhanced OER activity. Taken together, this new class of material could be utilized in energy conversion and storage as well as sensing applications.

Unveiling the exceptional synergism-induced design of Co-Mg-Al layered triple hydroxides (LTHs) for boosting catalytic activity toward the green synthesis of indol-3-yl derivatives under mild conditions.

The current study provides a novel insight into the role of synergism of the changes in Mg2+/ Al3+ in the best catalytic activity of indol-3-yl derivatives. A series of Co-Mg-Al layered triple hydroxides (LTHs) catalysts were produced by altering the Al3+/Mg2+ ratio with respect to Co2+. The physicochemical properties of LTHs were well characterized by ICP-AES, XRD, FTIR, FE-SEM, BET, Zeta-sizer, and VSM. The results show that the sample CMA4 (Co2+:Mg2+:Al3+ 2:4:4) is an exception to the physicochemical characteristics of the produced Co-Mg-Al LTHs, which is due to the synergism between the changes in Mg2+ and Al3+. To the best of our knowledge, this is the first study to report the synthesis of indol-3-yl derivatives from indole-3-carbaldehyde using Co-Mg-Al LTHs as highly efficient heterogeneous catalysts, which is an extremely appealing path. The selectivity of the synthesis was studied by condensing various nucleophiles through the one-pot method that established superior reactivity under mild conditions. Notably, the results show that the Co-Mg-Al LTHs system exhibited an extraordinarily catalytic activity, with the highest yield (98%) being obtained under the following optimal conditions: the concentration of Co-Mg-Al LTHs = 5 mol%, 30 min., water/ethanol as solvent. Furthermore, the reusable studies exhibited that the catalysts were found to be stable and reusable for up to six cycles without substantial loss of catalytic activity. Finally, a plausible reaction mechanism of the Co-Mg-Al LTHs system for indol-3-yl derivatives was put forward according to our comprehensive analysis. Our work illuminates a cheap and flexible strategy for the synthesis of indol-3-yl derivatives using Co-Mg-Al LTHs.

The new SARS-CoV-2 strain shows a stronger binding affinity to ACE2 due to N501Y mutant.

SARS-CoV-2 is a global challenge due to its ability to spread much faster than the SARS-CoV, which was attributed to the mutations in the receptor binding domain (RBD). These mutations enhanced the electrostatic interactions. Recently, a new strain is reported in the UK that includes a mutation (N501Y) in the RBD, that is possibly increasing the infection rate. Here, using Molecular Dynamics simulations (MD) and Monte Carlo (MC) sampling, we show that the N501 mutation enhanced the electrostatic interactions due to the formation of a strong hydrogen bond between SARS-CoV-2-T500 and ACE2-D355 near the mutation site. In addition, we observed that the electrostatic interactions between the SARS-CoV-2 and ACE2 in the wild type and the mutant are dominated by salt-bridges formed between SARS-CoV-2-K417 and ACE2-D30, SARS-CoV-2-K458, ACE2-E23, and SARS-CoV-2-R403 and ACE2-E37. These interactions contributed more than 40% of the total binding energies.

Silky Co3O4 nanostructures for the selective and sensitive enzyme free sensing of uric acid.

In this study, simple, new and functional silky nanostructures of Co3O4 are prepared by hydrothermal method. These nanostructures are successfully used for the enzyme free sensing of uric acid in 0.1 M phosphate buffer solution of pH 7.3. Physical characterization experiments were carried out to explore the morphology, composition and crystalline phase of the newly prepared Co3O4 nanostructures. Scanning electron microscopy (SEM) shows a silk like morphology and energy dispersive spectroscopy (EDS) revealed the presence of Co and O as the main elements. Powder X-ray diffraction (XRD) demonstrates a cubic crystallography with well resolved diffraction patterns. The electrochemical activity of these silky Co3O4 nanostructures was evaluated by cyclic voltammetry (CV) in a 0.1 M phosphate buffer solution at pH 7.3. The high purity and unique morphology of Co3O4 shows a highly sensitive and selective response towards the non-enzymatic sensing of uric acid. This uric acid sensor exhibits a linear range of 0.5 mM to 3.5 mM uric acid and a 0.1 mM limit of detection. The anti-interference capability of this uric acid sensor was monitored in the presence of common interfering species. Furthermore, electrochemical impedance spectroscopy confirms a low charge transfer resistance value of 5.11 K Ω cm2 for silky Co3O4 nanostructures which significantly supported the CV results. The proposed modified electrode is stable, selective and reproducible which confirms its possible practical use. Silky Co3O4 nanostructures can be of great importance for diverse electrochemical applications due to their excellent electrochemical activity and large surface area.

Development of a specific troponin I detection system with enhanced immune sensitivity using a single monoclonal antibody.

Using an immunoassay in combination with surface plasmon fluorescence spectroscopy (SPFS), we report the rapid detection of troponin I, a valuable biomarker for diagnosis of myocardial infarction. We discuss the implementation of (i) direct, (ii) sandwich, and (iii) competitive assay formats, based on surface plasmon resonance and SPFS. To elucidate the results, we relate the experiments to orientation-dependent interaction of troponin I epitopes with respective immunoglobulin G antibodies. A limit of detection (LoD) of 19 pM, with 45 min readout time, was achieved using single monoclonal antibody that is specific for one epitope. The borderline between normal people and patients is 20 pM to 83 pM cTnI concentration, and upon the outbreak of acute myocardial infraction it can raise to 2 nM and levels at 20 nM for 6-8 days, therefore the achieved LoD covers most of the clinically relevant range. In addition, this system allows for the detection of troponin I using a single specific monoclonal antibody, which is highly beneficial in case of detection in real samples, where the protein has a complex form leading to hidden epitopes, thus paving the way towards a system that can improve early-stage screening of heart attacks.

Comparing the Binding Interactions in the Receptor Binding Domains of SARS-CoV-2 and SARS-CoV.

SARS-CoV-2, since emerging in Wuhan, China, has been a major concern because of its high infection rate and has left more than six million infected people around the world. Many studies endeavored to reveal the structure of the SARS-CoV-2 compared to the SARS-CoV, in order to find solutions to suppress this high infection rate. Some of these studies showed that the mutations in the SARS-CoV spike (S) protein might be responsible for its higher affinity to the ACE2 human cell receptor. In this work, we used molecular dynamics simulations and Monte Carlo sampling to compare the binding affinities of the S proteins of SARS-CoV and SARS-CoV-2 to the ACE2. Our results show that the protein surface of the ACE2 at the receptor binding domain (RBD) exhibits negative electrostatic potential, while a positive potential is observed for the S proteins of SARS-CoV/SARS-CoV-2. In addition, the binding energies at the interface are slightly higher for SARS-CoV-2 because of enhanced electrostatic interactions. The major contributions to the electrostatic binding energies result from the salt bridges forming between R426 and ACE-2-E329 in the case of SARS-CoV and K417 and ACE2-D30 in the SARS-CoV-2. In addition, our results indicate that the enhancement in the binding energy is not due to a single mutant but rather because of the sophisticated structural changes induced by all these mutations together. This finding suggests that it is implausible for the SARS-CoV-2 to be a lab-engineered virus.

Modelling photovoltaic soiling losses through optical characterization.

The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value.

Doing more with less: a method for low total mass, affinity measurement using variable-length nanotethers.

Interactions between biomolecules are an important feature of biological systems and understanding these interactions is a key goal in biochemical studies. Using conventional techniques, such as surface plasmon resonance and isothermal titration calorimetry, the determination of the binding constants requires a significant amount of time and resources to produce and purify sufficient quantities of biomolecules in order to measure the affinity of biological interactions. Using DNA hybridization, we have demonstrated a new technique based on the use of nanotethers and time-resolved Forster resonance energy transfer (FRET) that significantly reduces the amount of material required to carry out quantitative binding assays. Test biomolecules were colocalized and attached to a surface using DNA tethers constructed from overlapping oligonucleotides. The length of the tethers defines the concentration of the tethered biomolecule. Effective end concentrations ranging from 56 nM to 3.8 µM were demonstrated. The use of variable length tethers may have wider applications in the quantitative measurement of affinity binding parameters.

Chemical doping of large-area stacked graphene films for use as transparent, conducting electrodes.

Graphene is considered a leading candidate to replace conventional transparent conducting electrodes because of its high transparency and exceptional transport properties. The effect of chemical p-type doping on graphene stacks was studied in order to reduce the sheet resistance of graphene films to values approaching those of conventional transparent conducting oxides. In this report, we show that large-area, stacked graphene films are effectively p-doped with nitric acid. The doping decreases the sheet resistance by a factor of 3, yielding films comprising eight stacked layers with a sheet resistance of 90 Omega/(square) at a transmittance of 80%. The films were doped either after all of the layers were stacked (last-layer-doped) or after each layer was added (interlayer-doped). A theoretical model that accurately describes the stacked graphene film system as a resistor network was developed. The model defines a characteristic transfer length where all the channels in the graphene films actively contribute to electrical transport. The experimental data shows a linear increase in conductivity with the number of graphene layers, indicating that each layer provides an additional transport channel, in good agreement with the theoretical model.

Comparison of methods for generating planar DNA-modified surfaces for hybridization studies.

The surface conformation and accessibility of oligonucleotides within arrays are two key parameters that affect the utility of immobilized nucleic acids in sensor technologies. In this work, a novel combination of analytical techniques was used to compare two methods for DNA immobilization on glass. The aim of the study was to identify a method that generated a high surface density of hybridization-accessible oligonucleotides in a true planar monolayer. The first method based on direct coupling of silanized DNA to the glass surface showed a high immobilization density of 0.013 molecules/nm2 but low surface accessibility, as shown by the hybridization measurements (< or =15%). The second method, based on the biotin-streptavidin interaction, generated a high immobilization density (0.02 molecules/nm2) and high surface accessibility (90%). Atomic force microscopy and X-ray photoelectron spectroscopy indicated that both methods achieved uniform surfaces. Using the biotin-streptavidin system, the intermolecular distance between the hybridized molecules could be tightly controlled by titrating biotinylated complementary and noncomplementary oligonucleotides.