Coupling of atoms is the basis of chemistry, yielding the beauty and richness of molecules. We utilize semiconductor nanocrystals as artificial atoms to form nanocrystal molecules that are ...structurally and electronically coupled. CdSe/CdS core/shell nanocrystals are linked to form dimers which are then fused via constrained oriented attachment. The possible nanocrystal facets in which such fusion takes place are analyzed with atomic resolution revealing the distribution of possible crystal fusion scenarios. Coherent coupling and wave-function hybridization are manifested by a redshift of the band gap, in agreement with quantum mechanical simulations. Single nanoparticle spectroscopy unravels the attributes of coupled nanocrystal dimers related to the unique combination of quantum mechanical tunneling and energy transfer mechanisms. This sets the stage for nanocrystal chemistry to yield a diverse selection of coupled nanocrystal molecules constructed from controlled core/shell nanocrystal building blocks. These are of direct relevance for numerous applications in displays, sensing, biological tagging and emerging quantum technologies.
Semiconductor heterostructure nanocrystals, especially with core/shell architectures, are important for numerous applications. Here we show that by decreasing the shell growth rate the morphology of ...ZnS shells on ZnSe quantum rods can be tuned from flat to islands-like, which decreases the interfacial strain energy. Further reduced growth speed, approaching the thermodynamic limit, leads to coherent shell growth forming unique helical-shell morphology. This reveals a template-free mechanism for induced chirality at the nanoscale. The helical morphology minimizes the sum of the strain and surface energy and maintains band gap emission due to its coherent core/shell interface without traps, unlike the other morphologies. Reaching the thermodynamic controlled growth regime for colloidal semiconductor core/shell nanocrystals thus offers morphologies with clear impact on their applicative potential.
We report the development of a semiconductor nanorod-carbon nanotube based platform for wire-free, light induced retina stimulation. A plasma polymerized acrylic acid midlayer was used to achieve ...covalent conjugation of semiconductor nanorods directly onto neuro-adhesive, three-dimensional carbon nanotube surfaces. Photocurrent, photovoltage, and fluorescence lifetime measurements validate efficient charge transfer between the nanorods and the carbon nanotube films. Successful stimulation of a light-insensitive chick retina suggests the potential use of this novel platform in future artificial retina applications.
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IJS, KILJ, NUK, PNG, UL, UM
Quantum dots (QDs), semiconductor nanocrystals, are fluorescent nanoparticles of growing interest as an imaging tool of a diseased tissue. However, a major concern is their biocompatibility, ...cytotoxicity, and fluorescence instability in biological milieu, impeding their use in biomedical applications, in general, and for inflammation imaging, in particular. In addition, for an efficient fluorescent signal at the desired tissue, and avoiding systemic biodistribution and possible toxicity, targeting is desired. We hypothesized that phagocytic cells of the innate immunity system (mainly circulating monocytes) can be exploited as transporters of specially designed liposomes containing QDs to the inflamed tissue. We developed a liposomal delivery system of QDs (LipQDs) characterized with high encapsulation yield, enhanced optical properties including far-red emission wavelength and fluorescent stability, high quantum yield, and protracted fluorescent decay lifetime. Treatment with LipQDs, rather than free QDs, exhibited high accumulation and retention following intravenous administration in carotid-injured rats (an inflammatory model). QD–monocyte colocalization was detected in the inflamed arterial segment only following treatment with LipQDs. No cytotoxicity was observed following LipQD treatment in cell cultures, and changes in liver enzymes and gross histopathological changes were not detected in mice and rats, respectively. Our results suggest that the LipQD formulation could be a promising strategy for imaging inflammation.
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Singlet oxygen (1O2) generated upon photostimulation of photosensitizer molecules is a highly reactive specie which is utilized in photodynamic therapy. Recent studies have shown that semiconductor ...nanoparticles can be used as donors in fluorescence resonance energy transfer (FRET) process to excite attached photosensitizer molecules. In these studies, their unique properties, such as low nanoscale size, long-term photostability, wide broad absorbance band, large absorption cross section, and narrow and tunable emission bands were used to provide advantages over the traditional methods to produce singlet oxygen. Previous studies that achieved this goal, however, showed some limitations, such as low FRET efficiency, poor colloidal stability, nonspecific interactions, and/or complex preparation procedure. In this work, we developed and characterized a novel system of semiconductor quantum rods (QRs) and the photosensitizer meso-tetra(hydroxyphenyl) chlorin (mTHPC), as a model system that produces singlet oxygen without these limitations. A simple two-step preparation method is shown; Hydrophobic CdSe/CdS QRs are solubilized in aqueous solutions by encapsulation with lecithin and PEGylated phospholipid (PEG–PL) of two lipid lengths: PEG350 or PEG2000. Then, the hydrophobic photosensitizer mTHPC, was intercalated into the new amphiphilic PEG–PL coating of the QR, providing a strong attachment to the nanoparticle without covalent linkage. These PEGylated QR (eQR)–mTHPC nanocomposites show efficient FRET processes upon light stimulation of the QR component which results in efficient production of singlet oxygen. The results demonstrate the potential for future use of this concept in photodynamic therapy schemes.
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Semiconductor‐metal hybrid nanoparticles (HNPs) are promising photocatalysts for redox reactions, including water reduction for hydrogen generation and reactive oxygen species (ROS) formation. Herein ...we study the effect of the metal co‐catalyst type on the light‐induced ROS formation using a combination of spectrophotometric and fluorescence assays, as well as electron paramagnetic resonance spectroscopy. We find that although Pt tips are more efficient for H2 generation, hydrogen peroxide and hydroxyl radicals are formed more effectively by Au tipped HNPs. These variations are attributed to the different surface reactivity and selectivity related to the metal tip composition. The obtained understanding contributes to the optimal design of these hybrid nanosystems as photocatalysts in various ROS‐driven applications such as photopolymerization, and environmental and biomedical scenarios.
Just the tip of the iceberg: The metal tip effect on the light‐induced redox reactions by semiconductor‐metal hybrid nanoparticles was investigated. It is demonstrated that hydrogen peroxide and hydroxyl radicals are formed more effectively by Au tipped HNPs, whereas Pt tips are more efficient for H2 generation. These variations are attributed to the specificity of the metal surface reactivity.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Significance Increased heart rate predicts all-cause mortality; however, the major causes for elevated basal heart rate values and annual changes in them have not been systematically studied, ...possibly because of the high individual variability involved. Our study addressed the question, “which physiological and psychological parameters determine basal pulse and its annual changes?,” in a cohort of 17,380 apparently healthy volunteers. This is, to the best of our knowledge, the first statistics-based search for the major interactions between physiological and psychological determinants of basal pulse and annual pulse changes; it indicates, perhaps not surprisingly, that consistent exposure to terror threats ignites fear-induced exacerbation of preexisting neuro-immune risks of all-cause mortality and proposes a set of risk-predicting parameters that may have translational value.
Recent international terror outbreaks notably involve long-term mental health risks to the exposed population, but whether physical health risks are also anticipated has remained unknown. Here, we report fear of terror-induced annual increases in resting heart rate (pulse), a notable risk factor of all-cause mortality. Partial least squares analysis based on 325 measured parameters successfully predicted annual pulse increases, inverse to the expected age-related pulse decline, in approximately 4.1% of a cohort of 17,380 apparently healthy active Israeli adults. Nonbiased hierarchical regression analysis among 27 of those parameters identified pertinent fear of terror combined with the inflammatory biomarker C-reactive protein as prominent coregulators of the observed annual pulse increases. In comparison, basal pulse primarily depended on general physiological parameters and reduced cholinergic control over anxiety and inflammation, together indicating that consistent exposure to terror threats ignites fear-induced exacerbation of preexisting neuro-immune risks of all-cause mortality.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Selective serotonin reuptake inhibitors (SSRIs) show anti-inflammatory effects, suggesting a possible interaction with both Toll-like-receptor 4 (TLR4) responses and cholinergic signaling through as ...yet unclear molecular mechanism(s). Our results of structural modeling support the concept that the antidepressant fluoxetine physically interacts with the TLR4–myeloid differentiation factor-2 complex at the same site as bacterial lipopolysaccharide (LPS). We also demonstrate reduced LPS-induced pro-inflammatory interleukin-6 and tumor necrosis factor alpha in human peripheral blood mononuclear cells preincubated with fluoxetine. Furthermore, we show that fluoxetine intercepts the LPS-induced decreases in intracellular acetylcholinesterase (AChE-S) and that AChE-S interacts with the nuclear factor kappa B (NFκB)-activating intracellular receptor for activated C kinase 1 (RACK1). This interaction may prevent NFκB activation by residual RACK1 and its interacting protein kinase PKCβII. Our findings attribute the anti-inflammatory properties of SSRI to surface membrane interference with leukocyte TLR4 activation accompanied by intracellular limitation of pathogen-inducible changes in AChE-S, RACK1, and PKCβII.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Hybrid semiconductor–metal nanoparticles (HNPs) manifest unique combined and often synergetic properties stemming from the materials combination. These structures exhibit spatial charge separation ...across the semiconductor–metal junction upon light absorption, enabling their use as photocatalysts. So far, the main impetus of photocatalysis research in HNPs addresses their functionality in solar fuel generation. Recently, it was discovered that HNPs are functional in efficient photocatalytic generation of reactive oxygen species (ROS). This has opened the path for their implementation in diverse biomedical and industrial applications where high spatially temporally resolved ROS formation is essential. Here, the latest studies on the synergistic characteristics of HNPs are summarized, including their optical, electrical, and chemical properties and their photocatalytic function in the field of solar fuel generation is briefly discussed. Recent studies are then focused concerning photocatalytic ROS formation with HNPs under aerobic conditions. The emergent applications of this capacity are then highlighted, including light‐induced modulation of enzymatic activity, photodynamic therapy, antifouling, wound healing, and as novel photoinitiators for 3D‐printing. The superb photophysical and photocatalytic properties of HNPs offer already clear advantages for their utility in scenarios requiring on‐demand light‐induced radical formation and the full potential of HNPs in this context is yet to be revealed.
Hybrid semiconductor–metal nanoparticles are promising photocatalysts. Recent research on photocatalytic functionality in anaerobic and aerobic conditions toward water splitting and reactive oxygen species formation by these hybrid nanoparticles is highlighted. Novel applications that emerge from the photocatalytic radical formation capacity are described, including in areas of biomedicine and 3D‐printing.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Semiconductor–metal hybrid nanoparticles manifest efficient light-induced spatial charge separation at the semiconductor–metal interface, as demonstrated by their use for hydrogen generation via ...water splitting. Here, we pioneer a study of their functionality as efficient photocatalysts for the formation of reactive oxygen species. We observed enhanced photocatalytic activity forming hydrogen peroxide, superoxide, and hydroxyl radicals upon light excitation, which was significantly larger than that of the semiconductor nanocrystals, attributed to the charge separation and the catalytic function of the metal tip. We used this photocatalytic functionality for modulating the enzymatic activity of horseradish peroxidase as a model system, demonstrating the potential use of hybrid nanoparticles as active agents for controlling biological processes through illumination. The capability to produce reactive oxygen species by illumination on-demand enhances the available peroxidase-based tools for research and opens the path for studying biological processes at high spatiotemporal resolution, laying the foundation for developing novel therapeutic approaches.
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