Exposure to Oxidized Multi-Walled CNTs Can Lead to Oxidative Stress in the Asian Freshwater Clam Corbicula fluminea (Müller, 1774).

The increasing attention that carbon-based nanomaterials have attracted due to their distinctive properties makes them one of the most widely used nanomaterials for industrial purposes. However, their toxicity and environmental effects must be carefully studied, particularly regarding aquatic biota. The implications of these carbon-based nanomaterials on aquatic ecosystems, due to their potential entry or accidental release during manufacturing and treatment processes, need to be studied because their impacts upon living organisms are not fully understood. In this research work, the toxicity of oxidized multi-walled carbon nanotubes (Ox-MWCNTs) was measured using the freshwater bivalve (Corbicula fluminea) after exposure to different concentrations (0, 0.1, 0.2, and 0.5 mg·L-1 Ox-MWCNTs) for 14 days. The oxidized multi-walled carbon nanotubes were analyzed (pH, Raman microscopy, high-resolution electron microscopy, and dynamic light scattering), showing their properties and behavior (size, aggregation state, and structure) in water media. The antioxidant defenses in the organism's digestive gland and gills were evaluated through measuring oxidative stress enzymes (glutathione-S-transferase, catalase, and superoxide dismutase), lipid peroxidation, and total ubiquitin. The results showed a concentration-dependent response of antioxidant enzymes (CAT and GST) in both tissues (gills and digestive glands) for all exposure periods in bivalves exposed to the different concentrations of oxidized multi-walled carbon nanotubes. Lipid peroxidation (MDA content) showed a variable response with the increase in oxidized multi-walled carbon nanotubes in the gills after 7 and 14 exposure days. Overall, after 14 days, there was an increase in total Ub compared to controls. Overall, the oxidative stress observed after the exposure of Corbicula fluminea to oxidized multi-walled carbon nanotubes indicates that the discharge of these nanomaterials into aquatic ecosystems can affect the biota as well as potentially accumulate in the trophic chain, and may even put human health at risk if they ingest contaminated animals.

Nanostructured Heterogeneous Catalysts for Bioorthogonal Reactions.

Bioorthogonal chemistry has inspired a new subarea of chemistry providing a powerful tool to perform novel biocompatible chemospecific reactions in living systems. Following the premise that they do not interfere with biological functions, bioorthogonal reactions are increasingly applied in biomedical research, particularly with respect to genetic encoding systems, fluorogenic reactions for bioimaging, and cancer therapy. This Minireview compiles recent advances in the use of heterogeneous catalysts for bioorthogonal reactions. The synthetic strategies of Pd-, Au-, and Cu-based materials, their applicability in the activation of caged fluorophores and prodrugs, and the possibilities of using external stimuli to release therapeutic substances at a specific location in a diseased tissue are discussed. Finally, we highlight frontiers in the field, identifying challenges, and propose directions for future development in this emerging field.

SERS optical accumulators as unified nanoplatforms for tear sampling and sensing in soft contact lenses.

Tear analysis has become an invaluable asset in clinical research in order to identify and quantify novel biomarkers for a wide array of conditions. The present work is intended to take this area of study one step further by implementing an innovative sensing platform through which exploration of low-molecular-weight compounds is conducted outperforming traditional analytical technologies. With this aim, carefully engineered plasmonic nanoassemblies have been synergistically combined with molecular-sieving materials giving rise to size-selective samplers with SERS detection capabilities. These architectures have been then integrated onto hydrogel-based contact lenses and tested in simulated tear fluids in order to evidence their operational features. Through this approach, a prolonged analyte accumulation can be realized, thus providing a competitive advantage in those scenarios where concentration of biomarkers is typically low or minimum sample volumes are not met. Additionally, quenching of metabolic flux and analyte extraction protocols can be circumvented, hence preventing the intrinsic physical and chemical interferences stemming from these procedures. The obtained results render these sensing platforms as promising medical devices, and constitute a great opportunity in order to expand the clinical toolkit in tear analysis.

Remote Activation of Hollow Nanoreactors for Heterogeneous Photocatalysis in Biorelevant Media.

Major current challenges in nano-biotechnology and nano-biomedicine include the implementation of predesigned chemical reactions in biological environments. In this context, heterogeneous catalysis is emerging as a promising approach to extend the richness of organic chemistry onto the complex environments inherent to living systems. Herein we report the design and synthesis of hybrid heterogeneous catalysts capable of being remotely activated by near-infrared (NIR) light for the performance of selective photocatalytic chemical transformations in biological media. This strategy is based on the synergistic integration of Au and TiO2 nanoparticles within mesoporous hollow silica capsules, thus permitting an efficient hot-electron injection from the metal to the semiconductor within the interior of the capsule that leads to a confined production of reactive oxygen species. These hybrid materials can also work as smart NIR-responsive nanoreactors inside living mammalian cells, a cutting-edge advance toward the development of photoresponsive theranostic platforms.

Boosting the analytical properties of gold nanostars by single particle confinement into yolk porous silica shells.

Herein we illustrate an effective protocol to boost the optical enhancing properties of gold nanostars. By coating single nanostars with a mesoporous silica layer of the appropriate size (yolk capsules), to localize them under optical microscopy, it is possible to enumerate single particles and design SERS quantitative methods with minute amounts of metallic particles.

Spontaneous Formation of Cold-Welded Plasmonic Nanoassemblies with Refracted Shapes for Intense Raman Scattering.

Nanostructures with concave shapes made from continuous segments of plasmonic metals are known to dramatically enhance Raman scattering. Their synthesis in solutions is hindered, however, by their thermodynamic instability due to large surface area and high curvature of refracted geometries with nanoscale dimensions. Herein, we show that nanostructures with concave geometries can spontaneously form via self-organization of gold nanoparticles (NPs) at the air-water interface. The weakly bound surface ligands on the particle surface make possible their spontaneous accumulation and self-assembly at the air-water interface, forming monoparticulate films. Upon heating to 80 °C, the NPs further assemble into concave nanostructures where NPs are cold-welded to each other. Furthermore, the nanoassemblies effectively adsorb molecular analytes during their migration from the bulk solution to the surface where they can be probed by laser spectroscopies. We demonstrate that these films with local concentration of analytes increased by orders of magnitude and favorable plasmonic shapes can be exploited for surface-enhanced Raman scattering for high-sensitivity analysis of aliphatic molecules.