Search

Gold nanoparticles (AuNPs) have found use in broad range of applications such as in catalysis and nanomedicine. Despite the fact that thiol-based AuNPs have been widely studied, they suffer from relative instability in various conditions, such as high and low temperatures, pH variations, and are prone to oxidation. Over the last decade, N-heterocyclic carbenes (NHCs) have been under spotlight as suitable ligands to stabilize metal nanoparticles and surfaces. Although NHC-functionalized AuNPs have been shown to outperform their thiol-based analogs in terms of stability, their applications in nanomedicine have not been realized. Hybrid nanomaterials, such as AuNPs tagged with [pi]-conjugated molecules with aggregation-induced emission (AIE) property, are promising candidates to develop fluorescent materials for cellular imaging. The combination of NHC-stabilized AuNPs with AIE to form stable, fluorescent hybrid AuNPs is of significant interest to open the door to develop new NHC-based nanomaterials. Herein, we report the synthesis and characterization of water-soluble fluorescent NHC-decorated AuNPs for potential applications in nanomedicine. Their stability in biologically relevant conditions is investigated. Key words: gold nanoparticles, N-heterocyclic carbene, tetraphenylethylene, fluorescent, Introduction Metal nanoparticles, and especially gold nanoparticles (AuNPs), have been at the center of most new technologies since their first discovery. Because of their nanomeric size and hence, their high [...]

Using publicly-available average monthly groundwater level data in 478 sub-basins and 30 basins in Iran, we quantify country-wide groundwater depletion in Iran. Natural and anthropogenic elements affecting the dynamics of groundwater storage are taken into account and quantified during the period of 2002-2015. We estimate that the total groundwater depletion in Iran to be ~ 74 km3 during this period with highly localized and variable rates of change at basin and sub-basin scales. The impact of depletion in Irans groundwater reserves is already manifested by extreme overdrafts in ~ 77% of Irans land area, a growing soil salinity across the entire country, and increasing frequency and extent of land subsidence in Irans planes. While meteorological/hydrological droughts act as triggers and intensify the rate of depletion in country-wide groundwater storage, basin-scale groundwater depletions in Iran are mainly caused by extensive human water withdrawals. We warn that continuation of unsustainable groundwater management in Iran can lead to potentially irreversible impacts on land and environment, threatening countrys water, food, socio-economic security.

The deposition of insoluble proteinaceous aggregates in the form of amyloid fibrils within the extracellular space of tissues is associated with numerous diseases. The development of molecular approaches to arrest amyloid formation and prevent cellular degeneration remains very challenging due to the complexity of the process of protein aggregation, which encompasses an infinite array of conformations and quaternary structures. Polyanionic biopolymers, such as glycosaminoglycans and RNAs, have been shown to modulate the self‐assembly of amyloidogenic polypeptides and to reduce the toxicity induced by the formation of oligomeric and/or pre‐fibrillar proteospecies. This study evaluates the effects of double‐stranded DNA (dsDNA) nanostructures (1D, 2D, and 3D) on amyloid self‐assembly, fibril disaggregation, and the cytotoxicity associated with amyloidogenesis. Using the islet amyloid polypeptide (IAPP) whose pancreatic accumulation is the hallmark of type 2 diabetes, it was observed that dsDNA nanostructures inhibit amyloid formation by inducing the formation of spherical complexes in which the peptide adopts a random coil conformation. Interestingly, the DNA nanostructures showed a persistent ability to disassemble enzymatically and thermodynamically stable amyloid fibrils into nanoscale DNA/IAPP entities that are fully compatible with β‐pancreatic cells and are biodegradable by proteolysis. Notably, dsDNA nanostructures avidly trapped highly toxic soluble oligomeric species in complete cell culture media and converted them into non‐toxic binary complexes. Overall, these results expose the potent modulatory effects of dsDNA on amyloidogenic pathways, and these DNA nanoscaffolds could be used as a source of inspiration for the design of molecules to fight amyloid‐related disorders. [ABSTRACT FROM AUTHOR]

The development of stimuli-responsive materials is of significant interest for many applications including drug delivery, medical imaging, sensors, and microfluidic devices. Among the available stimuli, light is particularly attractive as it can be applied with high spatial and temporal resolution. We describe here the synthesis of amphiphilic triblock copolymers composed of poly(ethylene glycol) and a hydrophobic block containing o-nitrobenzyl esters throughout the backbone using copper-catalyzed azide-alkyne cycloaddition chemistry. These materials were designed to have a high weight fraction of the hydrophobic block to favour nonmicellar aggregates. The self-assembly in water was studied using nanoprecipitation and the resulting assemblies were characterized by dynamic light scattering and transmission electron microscopy. Under optimized conditions, it was possible to prepare polymer vesicles, commonly referred to as polymersomes, with diameters of approximately 100 nm. The degradation of these materials in response to UV light was studied by spectroscopy, light scattering, and electron microscopy, demonstrating that the vesicles were broken down. These results suggest the potential of these materials for applications such as encapsulation and release. Key words: photodegradable, stimuli responsive, vesicles, polymersomes, self-assembly. La mise au point de materiaux reagissant aux stimuli revet un interet considerable pour de nombreuses applications, notamment la liberation de medicaments, l'imagerie medicale, les capteurs et les dispositifs microfluidiques. Parmi les stimuli existants, la lumiere est particulierement interessante, car elle peut faire l'objet d'applications a haute resolution spatiale et temporelle. Dans cet article, nous decrivons la synthese de copolymeres amphiphiles triblocs composes de poly(oxide d'ethylene) et d'une sequence hydrophobe contenant des esters d'ortho-nitrobenzyle disposes sur la chaine principale, par une cycloaddition azoture-alcyne catalysee par le cuivre. Ces materiaux ont ete concus pour qu'une fraction elevee de leur poids soit attribuable aux blocs hydrophobes, de facon a favoriser les agregats non micellaires. L'autoassemblage dans l'eau a ete etudie au moyen de la nanoprecipitation, et les assemblages resultants ont ete caracterises par la diffusion dynamique de la lumiere et la microscopie electronique a transmission. En conditions optimisees, il a ete possible de preparer des vesicules polymeriques, souvent appelees polymersomes, dont le diametre est d'environ 100 nm. La degradation de ces materiaux en reponse a la lumiere ultraviolette a ete etudiee par spectroscopie, diffusion de la lumiere et microscopie electronique qui demontrent la rupture des vesicules. Ces resultats montrent le potentiel de ces materiaux dans des applications telles que l'encapsulation et la liberation de medicaments. [Traduit par la Redaction] Mots-cles : photodegradable, reagissant aux stimuli, vesicules, polymersomes, autoassemblage., Introduction In recent years, there has been significant interest in the development of stimuli-responsive materials for a wide range of applications including drug delivery, medical imaging, sensors, and microfluidics. Materials [...]