Correction to “Two-Dimensional Bi₂WO₆ Nanosheets as a Robust Catalyst toward Photocyclization”

Correction to “Two-Dimensional Bi₂WO₆ Nanosheets as a Robust Catalyst toward Photocyclization

Two-Dimensional Bi₂WO₆ Nanosheets as a Robust Catalyst toward Photocyclization

The present work describes the improved photocatalytic activity of cetyl trimethylammonium bromide (CTAB)-assisted Bi₂WO₆ (CBTH) toward the synthesis of bioactive benzazoles. X-ray diffraction analysis of CBTH suggests that crystal growth has occurred along the (200) plane, whereas field-emission scanning electron microscopy images confirm two-dimensional rose bud morphology and high-resolution transmission electron microscopy analysis suggests the formation of thin nanosheets possessing an orthorhombic structure. Temperature-programmed desorption of ammonia and Py-IR measurements indicate substantial acidity with the generation of Brønsted acid sites on the surface of CBTH. Raman spectra of CBTH also corroborate these observations with the formation of defects within [Bi₂O₂]²⁺ layers, resulting in decreased thickness and shapes of nanoplates. These beneficial properties are explored toward the photochemical synthesis of benzazoles using a 35 W tungsten lamp and a CBTH photocatalyst, resulting in better yields at lesser exposure time. It is observed that the catalytic activity is retained up to five consecutive cycles with marginal decrease in % yield. Such a feature can be ascribed to the photostability of the photocatalyst even after continuous exposure to light, implying that the surface active sites remained unaltered as evident from the X-ray photoelectron spectroscopy analysis of pre- and post-characterization of CBTH. Moreover, decrease in the surface hydroxyl groups after five catalytic cycles also accounts for the generation of enhanced Brønsted sites owing to the presence of Bi–O on the surface of CBTH. It exhibits better catalytic activity as compared to other photocatalysts employed for the synthesis of benzazoles. Thus, CBTH serves as a robust photocatalyst for the facile synthesis of these heterocycles in a sustainable manner

Reductive Cyclization of Levulinic Acid to γ‑Valerolactone over Non-Noble Bimetallic Nanocomposite

Bimetallic nanoparticles have diverse applications in catalytic processes owing to the differences in individual properties that contribute to their increased catalytic activity. To further improve the efficiency, they are dispersed in an inert support that enhances the catalytic activity toward organic transformations. In this study, we report simple, facile, and cost-effective chemical route for the fabrication of nanocomposites with Fe–Ni bimetallic nanoparticles supported on montmorillonite (MMT) possessing variation in the Fe and Ni content. These composites are characterized with X-ray diffraction, transmission electron microscopy surface area, and NH₃-TPD. Fe–Ni bimetallic nanoparticles are well-dispersed within MMT structure having particle sizes of about 30–40 nm. Among various compositions of Fe–Ni/MMT catalysts, composite with 25% Fe and 25% Ni exhibits >99% LA conversion with 98% selectivity to GVL within 1 h. IPA is found to be better solvent for levulinic acid (LA) to γ-valerolactone (GVL) conversion, while substantial leaching of iron takes place when water is used as a solvent. It is observed that bimetallic sites are responsible for reduction of LA, while strong acidic sites of MMT are favoring subsequent cyclization to GVL. XPS analysis of fresh and reused Fe–Ni/MMT composites suggest that the catalyst surface does not undergo any chemical change during successive cycles, and the catalytic activity is retained up to six cycles. The plausible mechanism for LA to GVL conversion involves reductive cyclization processes through formation of levulinate ester that undergoes lactonization due to synergism in bimetallic nanoparticles and MMT clay

Synthesis, Characterization and In Vitro Study of Biocompatible Cinnamaldehyde Functionalized Magnetite Nanoparticles (CPGF Nps) For Hyperthermia and Drug Delivery Applications in Breast Cancer

<div><p>Cinnamaldehyde, the bioactive component of the spice cinnamon, and its derivatives have been shown to possess anti-cancer activity against various cancer cell lines. However, its hydrophobic nature invites attention for efficient drug delivery systems that would enhance the bioavailability of cinnamaldehyde without affecting its bioactivity. Here, we report the synthesis of stable aqueous suspension of cinnamaldehyde tagged Fe₃O₄ nanoparticles capped with glycine and pluronic polymer (CPGF NPs) for their potential application in drug delivery and hyperthermia in breast cancer. The monodispersed superparamagnetic NPs had an average particulate size of ∼20 nm. TGA data revealed the drug payload of ∼18%. Compared to the free cinnamaldehyde, CPGF NPs reduced the viability of breast cancer cell lines, MCF7 and MDAMB231, at lower doses of cinnamaldehyde suggesting its increased bioavailability and in turn its therapeutic efficacy in the cells. Interestingly, the NPs were non-toxic to the non-cancerous HEK293 and MCF10A cell lines compared to the free cinnamaldehyde. The novelty of CPGF nanoparticulate system was that it could induce cytotoxicity in both ER/PR positive/Her2 negative (MCF7) and ER/PR negative/Her2 negative (MDAMB231) breast cancer cells, the latter being insensitive to most of the chemotherapeutic drugs. The NPs decreased the growth of the breast cancer cells in a dose-dependent manner and altered their migration through reduction in MMP-2 expression. CPGF NPs also decreased the expression of VEGF, an important oncomarker of tumor angiogenesis. They induced apoptosis in breast cancer cells through loss of mitochondrial membrane potential and activation of caspase-3. Interestingly, upon exposure to the radiofrequency waves, the NPs heated up to 41.6°C within 1 min, suggesting their promise as a magnetic hyperthermia agent. All these findings indicate that CPGF NPs prove to be potential nano-chemotherapeutic agents in breast cancer.</p></div

Response of CPGF NPs to the radiofrequency waves for hyperthermia application.

<p>CPGF NPs exhibit hyperthermia potential. Response of Fe₃O₄ (F), Glycine (G), Pluronic (P), Cinnamaldehyde (C) and CPGF NPs to the radiofrequency waves have been depicted. The NPs showed a significant rise in the temperature to 41.6°C within a time span of 1 min.</p

Schematic illustration of synthesis of CPGF NPs and their release in breast cancer cell.

<p>Schematic illustration of synthesis of CPGF NPs and their release in breast cancer cell.</p

Physical characterization of CPGF NPs.

<p>(<b>A</b>) XRD patterns of F, GF, PGF and CPGF NPs. (<b>B</b>) TEM image with SAED of CPGF NPs. (<b>C</b>) FTIR patterns of F, GF, PGF and CPGF NPs.</p

Cinnamaldehyde loading and release profiles along with magnetic behavior of CPGF NPs.

<p>(<b>A</b>) Thermogravimetric analysis of F, GF, PGF and CPGF NPs. (<b>B</b>) Release profile of cinnamaldehyde from CPGF NPs at different pH values at different time points. (<b>C</b>) Inset shows uniform suspension of CPGF NPs (i) and (ii) response of the NPs to the externally placed magnet. VSM data shows the magnetic behavior of all the NPs.</p

Molecular mechanism underlying anticancer activity of CPGF NPs.

<p>CPGF NPs decreased migration and expression of tumor marker proteins in breast cancer cells. (<b>A</b>) The NPs reduced migration of MDAMB231 and MCF7 cells. The upper panel of each figure shows the wound made at 0 h and the lower panel shows the migration of cells after 18 h. (<b>B</b>) Graphical representation of wound closure in MDAMB231 and MCF7 at 18 h after CPGF NPs treatment. Values are represented as mean±SD of three independent experiments at p<0.01 for MDAMB231 and p<0.0005 for MCF7, indicating statistically significant differences compared to the untreated control cells. (<b>C</b>) Gelatin zymography shows downregulation of MMP-2 expression in MDAMB231 and MCF7 after treatment with CPGF NPs with their corresponding densitometric analysis. The values are represented as mean±SD of three independent experiments at p<0.001, indicating statistically significant differences compared to the untreated control cells. (<b>D</b>) Western blot analysis shows decrease in VEGF expression in MDAMB231 and MCF7 with their corresponding densitometric analysis. Values are represented as mean±SD of three independent experiments with p<0.0001, indicating statistically significant differences compared to the untreated control cells.</p

Cytotoxicity analysis of CPGF NPs and cinnamaldehyde.

<p>The breast cancer (MDAMB231 and MCF7) and non-cancerous (MCF10A and HEK293) cells were treated with different concentrations of (<b>A</b>) CPGF NPs and (<b>B</b>) cinnamaldehyde for 24 h and anlayzed for viability by MTT assay. Lower panel of X-axis in (<b>A</b>) refers to amount of cinnamaldehyde (µM) present in the corresponding concentrations of CPGF NPs (µg/ml) (as calculated from TGA data). All the data are presented as mean±SD of five independent experiments at p<0.0001, indicating statistically significant differences compared to the control untreated group.</p