Hyperbolic Meta-Antennas Enable Full Control of Scattering and Absorption of Light

We introduce a novel concept of hybrid metal-dielectric meta-antenna supporting type II hyperbolic dispersion, which enables full control of absorption and scattering of light in the visible/near-infrared spectral range. This ability lies in the different nature of the localized hyperbolic Bloch-like modes excited within the meta-antenna. The experimental evidence is corroborated by a comprehensive theoretical study. In particular, we demonstrate that two main modes, one radiative and one non-radiative, can be excited by direct coupling with the free-space radiation. We show that the scattering is the dominating electromagnetic decay channel, when an electric dipolar mode is induced in the system, whereas a strong absorption process occurs when a magnetic dipole is excited. Also, by varying the geometry of the system, the relative ratio of scattering and absorption, as well as their relative enhancement and/or quenching, can be tuned at will over a broad spectral range, thus enabling full control of the two channels. Importantly, both radiative and nonradiative modes supported by our architecture can be excited directly with far-field radiation. This is observed to occur even when the radiative channels (scattering) are almost totally suppressed, thereby making the proposed architecture suitable for practical applications. Finally, the hyperbolic meta-antennas possess both angular and polarization independent structural integrity, unlocking promising applications as hybrid meta-surfaces or as solvable nanostructures

Fabrication and Optical Characterization of Hyperbolic Nanoparticles on a Transparent Substrate

We report on the fabrication and optical characterization of hyperbolic nanoparticles on a transparent substrate. These nanoparticles enable a separation of ohmic and radiative channels in the visible and near-infrared frequency ranges. The presented architecture opens the pathway towards novel routes to exploit the light to energy conversion channels beyond what is offered by current plasmon-based nanostructures, possibly enabling applications spanning from thermal emission manipulation, theragnostic nano-devices, optical trapping and nano-manipulation, non-linear optical properties, plasmonenhanced molecular spectroscopy, photovoltaics and solar-water treatments, as well as heat-assisted ultra-dense and ultrafast magnetic recording

Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications

In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Principal Component Analysis (PCA) and X-ray Photoelectron Spectroscopy (XPS) have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP). The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules. Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.JRC.I.4-Nanobioscience

A proteomic approach to investigate the modification in the proteome of the cytoplasmatic compartment of Balb/3T3 cells after exposure to gold nanoparticles (AuNPs)

Nanoparticles are widely used in consumer products. However, information about the exposure of the consumer to nanoparticles and their potential health effects is very limited. Nanoparticles may move inside the human body in different manners (via inhalation, ingestion or skin contact), cross the cell membranes and accumulate for long periods of time. Emerging approaches in the area of exposure to nanomaterials and assessment of human health effects combine the use of in vitro cell systems and advanced analytical techniques to study the perturbation of the proteome. The appropriate use of these approaches has the potential to provide information on the possible de-regulation of essential physiological cellular processes. In the present study, we investigated the modification in the proteome of the cytoplasmatic compartment of the Balb/3T3 mouse fibroblast cell line after exposure to 5 and 15 nm gold nanoparticles (AuNPs) for 72 h. Protein separation by two-dimensional gel electrophoresis (2DE) followed by protein identification high-resolution mass spectrometry (MS) allowed us to study the differentially expressed proteome in order to explore underlying cellular mechanisms. Differentially expressed proteins were found to cover a range of functions including stress response, cell metabolism, cell growth and cytoskeleton organization. Remarkably, even small differences in particle size (10 nm) seemed to differently affect biological mechanisms. These findings consolidate existing knowledge and permit to get more insight to the cell mechanisms affected by AuNPs exposure. Our activities in the area of exposure to nanomaterials and potential health effects for the consumer are essential to support EU policy implementation.JRC.I.1-Chemical Assessment and Testin

Interactions of Serum Derived Proteins with Sub-Micrometer Structured Surfaces

Protein surface-interactions are of particular importance in the field of nanosensors and nanotoxicology. The ability to position and keep orientation and activity of proteins on nanostructures is essential for the proper function of nanosensors. It is also well known that proteins adsorbed on surfaces of nanoparticles will mediate their adsorption and uptake by the cells. Furthermore, conformational changes of the proteins, and thus the modification of their biological functions, will depend on the radius of curvature of the surface: this aspect is therefore of particular importance on nanomaterials or nanostructures. In both cases, methods for studying and controlling the adsorption of proteins on surfaces at the nanoscale are needed. This report presents the development and optimization of two nanofabrication methods combining plasma polymerization and electron beam lithography techniques for producing chemical patterns at nanoscale. Patterned surfaces produced with both fabrication processes exhibit high binding capacity as tested by Surface Plasmon Resonance with model proteins. Furthermore, we show that adsorption on the nanopatterns is similar to that observed on a flat surface with a direct proportionality to the active area. This work shows the suitability of the chemical patterning techniques and their high potential applicability for protein surface interactions study and miniaturized biosensing device development.JRC.I.4-Nanobioscience

A proteomic approach to investigate AuNPs effects in Balb/3T3 cells

Although gold nanoparticles (AuNPs) are currently used in several industrial products and biomedical applications, information about their biological effects is very limited. Thus, it is becoming crucial to assess their safety and adequately investigate the complexity of cell-nanoparticles interactions. In this work, the Balb/3T3 mouse fibroblast cell line was selected as an in vitro model to study AuNPs effects. Alteration of cellular processes and biochemical pathways caused by AuNPs exposure was investigated by analysing the differentially expressed proteome. The strength of this investigation resides in combining the high-resolving power of fluorescence two-dimensional differential gel electrophoresis with protein identification by high-resolution mass spectrometry. Of interest was the difference observed in the protein pattern expression of cells exposed to 5 and 15 nm AuNPs. From 2D gel-based proteomic data, it was found that 88 and 83 proteins were de-regulated after exposure to 5 and 15 nm AuNPs, respectively. Analysis of the proteome revealed that AuNPs triggers several pathways related to cellular growth and proliferation, cell morphology, cell cycle regulation, cellular function and maintenance, oxidative stress, inflammatory response.JRC.I.4-Nanobioscience

Complex Loop Dynamics Underpin Activity, Specificity and Evolvability in the (βα)8 Barrel Enzymes of Histidine and Tryptophan Biosynthesis

Enzymes are conformationally dynamic, and their dynamical properties play an important role in regulating their specificity and evolvability. In this context, substantial attention has been paid to the role of ligand-gated conformational changes in enzyme catalysis; however, such studies have focused on tremendously proficient enzymes such as triosephosphate isomerase and orotidine 5’-monophosphate decarboxylase, where the rapid (μs timescale) motion of a single loop dominates the transition between catalytically inactive and active conformations. In contrast, the (βα)8-barrels of tryptophan and histidine biosynthesis, such as the specialist isomerase enzymes HisA and TrpF, and the bifunctional isomerase PriA, are decorated by multiple long loops that undergo conformational transitions on the ms (or slower) timescale. Studying the interdependent motions of multiple slow loops, and their role in catalysis, poses a significant computational challenge. This work combines conventional and enhanced molecular dynamics simulations with empirical valence bond simulations to provide rich detail of the conformational behavior of the catalytic loops in HisA, PriA and TrpF, and the role of their plasticity in facilitating bifunctionality in PriA and evolved HisA variants. In addition, we demonstrate that, similar to other enzymes activated by ligand-gated conformational changes, loops 3 and 4 of HisA and PriA act as gripper loops, facilitating the isomerization of the large bulky substrate ProFAR, albeit now on much slower timescales. This hints at convergent evolution on these different (βα)8-barrel scaffolds. Finally, our work highlights the potential of engineering loop dynamics as a powerful tool to artificially manipulate the diverse catalytic repertoire of TIM-barrel proteins