The Effect of Polyvinyl Alcohol Addition on the Optical Properties and Oxygen Detection Performance of Titanium Dioxide and Methylene Blue Nanocomposite Colorimetric Indicators

In this study, we investigated the impact of polyvinyl alcohol (PVA) incorporation on the optical properties and oxygen detection performance of a titanium dioxide/methylene blue (TiO2/MB) nanocomposite colorimetric indicator for packaging applications. The nanocomposite was synthesized via mechanical milling of TiO2 nanoparticles with MB and citric acid. PVA, at varying concentrations (0, 3, 9, and 14 wt%), was introduced during the wet milling process to produce a homogeneous composite film. Spin coating was employed to fabricate TiO2/MB nanocomposite films for oxygen detection evaluation. The influence of PVA loading on the films' chemical functionalities and surface morphologies was assessed using Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). The indicator's activation process, involving a color change between bleached and colored states, and its recovery time were monitored via optical imaging and UV-VIS-NIR spectrophotometry. The results revealed that a PVA content of 9 wt% yielded well-defined films with enhanced stability of the TiO2/MB nanocomposite's oxygen detection performance.

Structural and Optical Characterizations of Polymethyl Methacrylate Films with the Incorporation of Ultrafine SiO2/TiO2 Composites Utilized as Self-Cleaning Surfaces

The structural and optical characterizations of nanocomposite films of polymethyl methacrylate (PMMA) and SiO2/TiO2 composites prepared via the spin-coating technique were investigated using different SiO2:TiO2 ratios. The SiO2/TiO2 nanocomposites were synthesized using the sonochemical process with Si:Ti precursor ratios of 1:0.1, 1:0.5, 1:1, 1:2, 1:4, and 0:1. All characterizations of ultrafine SiO2/TiO2 particles were loaded at 1 wt.% in a PMMA matrix for the fabrication of transparent SiO2/TiO2/PMMA composite films. The phase structure and morphology of SiO2/TiO2/PMMA composite films were monitored using X-ray diffraction, optical microscopy, and field-emission scanning electron microscopy. A surface roughness analysis of SiO2/TiO2/PMMA nanocomposite films was conducted using atomic force microscopy. For optical characterization, transmission properties with different incident angles of SiO2/TiO2/PMMA composite films were analyzed with UV-vis spectrophotometry. The water contact angles of SiO2/TiO2/PMMA composite films were analyzed to identify hydrophilic properties on film surfaces. Photocatalytic reactions in SiO2TiO2 composite films under UV irradiation were evaluated using rhodamine B dye degradation. The optimal condition of SiO2/TiO2/PMMA nanocomposite films was obtained at a 1:1 SiO2:TiO2 ratio in self-cleaning applications, resulting from good particle dispersion and the presence of the TiO2 phase in the composite.

Tailoring the Emission Behavior of WO3 Thin Films by Eu3+ Ions for Light-Emitting Applications

The article reports the successful fabrication of Eu³⁺-doped WO₃ thin films via the radio-frequency magnetron sputtering (RFMS) technique. To our knowledge, this is the first study showing the tunable visible emission (blue to bluish red) from a WO₃:Eu³⁺ thin film system using RFMS. X-ray diffractograms revealed that the crystalline nature of these thin films increased upto 3 wt% of the Eu³⁺ concentration. The diffraction peaks in the crystalline films are matched well with the monoclinic crystalline phase of WO₃, but for all the films', micro-Raman spectra detected bands related to WO₃ monoclinic phase. Vibrational and surface studies reveal the amorphous/semi-crystalline behavior of the 10 wt% Eu³⁺-doped sample. Valence state determination shows the trivalent state of Eu ions in doped films. In the 400-900 nm regions, the fabricated thin films show an average optical transparency of ~51-85%. Moreover, the band gap energy gradually reduces from 2.95 to 2.49 eV, with an enhancement of the Eu³⁺-doping content. The doped films, except the one at a higher doping concentration (10 wt%), show unique emissions of Eu³⁺ ions, besides the band edge emission of WO₃. With an enhancement of the Eu³⁺ content, the concentration quenching process of the Eu³⁺ ions' emission intensities is visible. The variation in CIE chromaticity coordinates suggest that the overall emission color can be altered from blue to bluish red by changing the Eu³⁺ ion concentration.

Computational design, synthesis and biological evaluation of PDE5 inhibitors based on N2,N4-diaminoquinazoline and N2,N6-diaminopurine scaffolds

We report the synthesis, and characterization of twenty-nine new inhibitors of PDE5. Structure-based design was employed to modify to our previously reported 2,4-diaminoquinazoline series. Modification include scaffold hopping to 2,6-diaminopurine core as well as incorporation of ionizable groups to improve both activity and solubility. The prospective binding mode of the compounds was determined using 3D ligand-based similarity methods to inhibitors of known binding mode, combined with a PDE5 docking and molecular dynamics based-protocol, each of which pointed to the same binding mode. Chemical modifications were then designed to both increase potency and solubility as well as validate the binding mode prediction. Compounds containing a quinazoline core displayed IC₅₀s ranging from 0.10 to 9.39 µM while those consisting of a purine scaffold ranging from 0.29 to 43.16 µM. We identified 25 with a PDE5 IC₅₀ of 0.15 µM, and much improved solubility (1.77 mg/mL) over the starting lead. Furthermore, it was found that the predicted binding mode was consistent with the observed SAR validating our computationally driven approach.

A novel potent autophagy inhibitor ECDD-S27 targets vacuolar ATPase and inhibits cancer cell survival

Autophagy is a conserved lysosomal-dependent cellular degradation process and its dysregulation has been linked to numerous diseases including neurodegeneration, infectious diseases, and cancer. Modulation of autophagy is therefore considered as an attractive target for disease intervention. We carried out a high-content image analysis screen of natural product-derived compounds to discover novel autophagy modulating molecules. Our screen identified ECDD-S27 as the most effective compound for increasing the number of autophagic vacuoles inside cells. The structure of ECDD-S27 revealed that it is a derivative of cleistanthin A, a natural arylnaphthalene lignan glycoside found in plants. ECDD-S27 increases the number of autophagic vacuoles by inhibiting the autophagic flux and is able to restrict the survival of different cancer cells at low nanomolar concentrations. Molecular docking and SERS analysis showed that ECDD-S27 may potentially target the V-ATPase. Upon treatment of various cancer cells with ECDD-S27, the V-ATPase activity is potently inhibited thereby resulting in the loss of lysosomal acidification. Taken together, these data indicated that ECDD-S27 retards the autophagy pathway by targeting the V-ATPase and inhibits cancer cell survival. The observed antitumor activity without cytotoxicity to normal cells suggests the therapeutic potential warranting further studies on lead optimization of the compound for cancer treatment.

Effects of Seeding Layer Annealing Temperature on Physical and Morphological Structure of Ga/F Co-Doped ZnO Nanostructures

In this work, effects of annealing temperature of seeding layer on structural properties and morphologies of Ga/F co-doped ZnO nanostructures synthesized by hydrothermal process were investigated by varying the annealing temperature of seed layer as 300-500 °C. The ZnO seeding layers were deposited onto cleaned glass substrates by dip-coating technique using zinc acetate dehydrate (CH3COO)2Zn·2H2O as starting coating precursor. The Ga/F co-doped ZnO nanostructures were then grown on these seed layers by conventional hydrothermal process using Zn(NO3)2, NH4F, GaN3O9 and hexamethyltetramine as Zn, F and Ga sources, respectively. Effect of seed layer annealing temperature on morphologies, structural and Photoluminescence properties was investigated by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), and Photoluminescence spectra, respectively. Variation of annealing temperature of seed layers can significantly result to the difference in morphological, structure and shape of the as-synthesized nanostructure products. It is found that the increase in annealing temperature leads to alternation in their shape from vertically-aligned nanosheets to nanorods with their average size ranging from 50 to 200 nm. Furthermore, the luminescence could be ascribed to the different contributions of the defect emissions, such asthe increase in the oxygen vacancy (VO) emissionor the decrease of the Zinc vacancy (Vzn). However, it can be speculated from the photoluminescence that the incorporated Ga and F substitute into ZnO.

Exploring the catalytic mechanism of dihydropteroate synthase: elucidating the differences between the substrate and inhibitor

Dihydropteroate synthase (DHPS) catalyzes the condensation of 6-hydroxymethyl-7,8-dihydropterin pyrophosphate (DHPPP) with p-aminobenzoic acid (pABA) and is a well validated target for anti-malarial and anti-bacterial drugs. However, in recent years its utility as a therapeutic target has diminished considerably due to multiple mutations. As such, considerable structural biology and medicinal chemistry effort has been expended to understand and overcome this issue. To date no detailed computational analysis of the protein mechanism has been made despite the detailed crystal structures and multiple mechanistic proposals being made. In this study the mechanistic proposals for DHPS have been systematically investigated using a hybrid QM/MM method. We aimed to compare the energetics associated with S_N1 and S_N2 processes, whether the S_N1 process involves a carbocation or neutral DHP intermediate, uncover the identity of the general base in the catalytic mechanism, and understand the differences in substrate vs. inhibitor reactivity. Our results suggest a reaction that follows an S_N1 process with the rate determining step being C-O bond breaking to give a carbocation intermediate. Comparative studies on the inhibitor STZ confirm the experimental observations that it is also a DHPS substrate.

Synthesis and Immunological Studies of the Lipomannan Backbone Glycans Found on the Surface of Mycobacterium tuberculosis

Investigations into novel bacterial drug targets and vaccines are necessary to overcome tuberculosis. Lipomannan (LM), found on the surface of Mycobacterium tuberculosis (Mtb), is actively involved in the pathogenesis and survival of Mtb. Here, we report for the first time a rapid synthesis and biological activities of an LM glycan backbone, α(1-6)mannans. The rapid synthesis is achieved via a regio- and stereoselective ring opening polymerization to generate multiple glycosidic bonds in one simple chemical step, allowing us to finish assembling the defined polysaccharides of 5-20 units within days rather than years. Within the same pot, the polymerization is terminated by a thiol-linker to serve as a conjugation point to carrier proteins and surfaces for immunological experiments. The synthetic glycans are found to have adjuvant activities in vivo. The interactions with DC-SIGN demonstrated the significance of α(1-6)mannan motif present in LM structure. Moreover, surface plasmon resonance (SPR) showed that longer chain of synthetic α(1-6)mannans gain better lectin's binding affinity. The chemically defined components of the bacterial envelope serve as important tools to reveal the interactions of Mtb with mammalian hosts and facilitate the determination of the immunologically active molecular components.

Influence of Ethanol as a Co-Solvent in Cyclodextrin Inclusion Complexation: A Molecular Dynamics Study

Molecular dynamics (MD) simulations were used to investigate the dynamics and host-guest interactions of the inclusion complexes between a potent anti-HIV agent, UC781, and three different types of cyclodextrins (CDs) including βCD, 2,6-dimethyl-βCD (MβCD), and 2-hydroxypropyl-βCD (HPβCD) in aqueous solution with ethanol (EtOH) as a co-solvent. The MD simulation results revealed that EtOH as the co-solvent and the type of cyclodextrin affected the inclusion complex formation. From this study, UC781/MβCD provided the most stable inclusion complex. The competition for the cavity of βCD between UC781 and EtOH and the ensuing occupation of βCD cavities by EtOH resulted in a weaker interaction between βCD and UC781. In HPβCD, a supramolecular complex of UC781−HPβCD−EtOH was formed. The EtOH could easily fill the residual void space of the interior of unoccupied HPβCD due to the movement of UC781. In MβCD, the strong hydrogen bond interactions between the UC781 amide group and the secondary hydroxyl groups of MβCD significantly stabilized the inclusion complex in the presence of EtOH.