Antibacterial Activities of Graphene Oxide-Molybdenum Disulfide Nanocomposite Films

Antibacterial [2-(Methacryloyloxy) ethyl] Trimethylammonium Chloride Functionalized Reduced Graphene Oxide/Poly(ethylene-co-vinyl alcohol) Multilayer Barrier Film for Food Packaging

The objective of present work was to construct antibacterial [2-(methacryloyloxy) ethyl] trimethylammonium chloride functionalized reduced graphene oxide/poly(ethylene-co-vinyl alcohol) (MTAC-rGO/EVOH) multilayer barrier films by using layer-by-layer assembly under a parallel electric field. Besides barrier and mechanical properties, the antibacterial activities of the film and cytotoxicity of MTAC-rGO nanosheets were extensively investigated. The functionalization of rGO was achieved by grafting MTAC onto a graphene framework through C (sp³)-C bonds. The assembly of MTAC-rGO on the EVOH matrix not only significantly improved film mechanical strength, but also endowed the targeting film with outstanding moisture barrier even under a relative humidity of 99% (e.g., 0.019 g m^-2 s^-1 atm^-1 for (MTAC-rGO/EVOH)₂₀) besides good oxygen barrier (e.g., 0.07 cm³ m^-2 d^-1 atm^-1 for (MTAC-rGO/EVOH)₂₀). Among the testing films, MTAC-rGO/EVOH film had the best antibacterial activity, and the activity against S. aureus was better than E. coli. Meanwhile, the cytotoxicity of MTAC-rGO nanosheets was very low. Results suggest that MTAC-rGO/EVOH film may have great potential in food active packaging.

Atomic scale study for the structural transformation of single layered MoS2

The structural transformation of single and few layered molybdenum disulfide (MoS₂) from 2H to 1T phase was studied at the atomic scale.

Study of Graphene Oxide Structural Features for Catalytic, Antibacterial, Gas Sensing, and Metals Decontamination Environmental Applications

This study represents a comprehensive review about the structural features of graphene oxide (GO) and its significance in environmental applications. Two dimensional (2D) GO is tremendously focused in advanced carbon-based nanomaterials for environmental applications due to its tunable physicochemical characteristics. Herein, we report foundational structural models of GO and explore the chemical bonding of oxygen moieties, with graphite basal plane using various characterization tools. Moreover, the impact of these oxygen moieties and the morphology of GO for environmental applications such as removal of metal ions and catalytic, antibacterial, and gas sensing abilities have here been critically reviewed for the first time. Environmental applications of GO are highly significant because, in the recent era, the fast progress of industries, even in the countryside, results in air and water pollution. GO has been widely investigated by researchers to eradicate such environmental issues and for potential industrial and clinical applications due to its 2D structural features, large surface area, presence of oxygen moieties, nonconductive nature, intense mechanical strength, excellent water dispersibility, and tunable optoelectronic properties. Thence, particular emphasis is directed toward the modification of GO by varying the number of its oxygen functional groups and by coupling it with other exotic nanomaterials to induce unique properties in GO for potential environmental remediation purposes.

Redox-active nanomaterials for nanomedicine applications

Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials.

Polymer Nanosheets from Supramolecular Assemblies of Conjugated Linoleic Acid-High Surface Area Adsorbents from Renewable Materials

We present a strategy for robustly cross-linking self-assembled lamellar mesophases made from plant-derived materials to generate polymer nanosheets decorated with a high density of functional groups. We formulate a supramoleclar complex by hydrogen-bonding conjugated linoleic acid moieties to a structure-directing tribasic aromatic core. The resulting constructs self-assemble into a thermotropic lamellar mesophase. Photo-cross-linking the mesophase with the aid of an acrylate cross-linker yields a polymeric material with high-fidelity retention of the lamellar mesophase structure. Transmission electron microscopy images demonstrate the preservation of the large area, highly ordered layered nanostructures in the polymer. Subsequent extraction of the tribasic core and neutralization of the carboxyl groups by NaOH result in exfoliation of polymer nanosheets with a uniform thickness of ∼3 nm. The nanosheets have a large specific area of ∼800 m²/g, are decorated by negatively charged carboxylate groups at a density of 4 nm^-2, and exhibit the ability to readily adsorb positively charged colloidal particles. The strategy as presented combines supramolecular self-assembly with the use of renewable or sustainably derived materials in a scalable manner. The resulting nanosheets have potential for use as adsorbents and, with further development, rheology modifiers.

Identification of non-activated lymphocytes using three-dimensional refractive index tomography and machine learning

Identification of lymphocyte cell types are crucial for understanding their pathophysiological roles in human diseases. Current methods for discriminating lymphocyte cell types primarily rely on labelling techniques with magnetic beads or fluorescence agents, which take time and have costs for sample preparation and may also have a potential risk of altering cellular functions. Here, we present the identification of non-activated lymphocyte cell types at the single-cell level using refractive index (RI) tomography and machine learning. From the measurements of three-dimensional RI maps of individual lymphocytes, the morphological and biochemical properties of the cells are quantitatively retrieved. To construct cell type classification models, various statistical classification algorithms are compared, and the k-NN (k = 4) algorithm was selected. The algorithm combines multiple quantitative characteristics of the lymphocyte to construct the cell type classifiers. After optimizing the feature sets via cross-validation, the trained classifiers enable identification of three lymphocyte cell types (B, CD4+ T, and CD8+ T cells) with high sensitivity and specificity. The present method, which combines RI tomography and machine learning for the first time to our knowledge, could be a versatile tool for investigating the pathophysiological roles of lymphocytes in various diseases including cancers, autoimmune diseases, and virus infections.

Membrane destruction-mediated antibacterial activity of tungsten disulfide (WS2)

Tungsten disulfide (WS₂) demonstrates clear antibacterial activity through inducing mechanical damage to the bacteria membrane integrity.