Large-Scale Plasmonic nanoCones Array For Spectroscopy Detection

Advanced optical materials or interfaces are gaining attention for diagnostic applications. However, the achievement of large device interface as well as facile surface functionalization largely impairs their wide use. The present work is aimed to address different innovative aspects related to the fabrication of large-area 3D plasmonic arrays, their direct and easy functionalization with capture elements, and their spectroscopic verifications through enhanced Raman and enhanced fluorescence techniques. In detail, we have investigated the effect of a Au-based nanoCone array, fabricated by means of direct nanoimprint technique over large area (mm²), on protein capturing and on the enhancement in optical signal. A selective functionalization of gold surfaces was proposed by using a peptide (AuPi3) previously selected by phage display. In this regard, two different sequences, labeled with fluorescein and biotin, were chemisorbed on metallic surfaces. The presence of Au nanoCones array consents an enhancement in electric field on the apex of cone, enabling the detection of molecules. We have witnessed around 12-fold increase in fluorescence intensity and SERS enhancement factor around 1.75 × 10⁵ with respect to the flat gold surface. Furthermore, a sharp decrease in fluorescence lifetime over nanoCones confirms the increase in radiative emission (i.e., an increase in photonics density at the apex of cones)

A Hybrid Plasmonic−Photonic Nanodevice for Label-Free Detection of a Few Molecules

Noble metal nanowaveguides supporting plasmon polariton modes are able to localize the optical fields at nanometer level for high sensitivity biochemical sensing devices. Here we report on the design and fabrication of a novel photonic−plasmonic device which demonstrates label-free detection capabilities on single inorganic nanoparticles and on monolayers of organic compounds. In any case, we determine the Raman scattering signal enhancement and the device detection limits that reach a number of molecules between 10 and 250. The device can be straightforwardly integrated in a scanning probe apparatus with the possibility to match topographic and label-free spectroscopic information in a wide range of geometries

3D Hollow Nanostructures as Building Blocks for Multifunctional Plasmonics

We present an advanced and robust technology to realize 3D hollow plasmonic nanostructures which are tunable in size, shape, and layout. The presented architectures offer new and unconventional properties such as the realization of 3D plasmonic hollow nanocavities with high electric field confinement and enhancement, finely structured extinction profiles, and broad band optical absorption. The 3D nature of the devices can overcome intrinsic difficulties related to conventional architectures in a wide range of multidisciplinary applications

Dark to Bright Mode Conversion on Dipolar Nanoantennas: A Symmetry-Breaking Approach

The excitation of plasmonic dark modes via a radiative channel is a phenomenon strongly hindered in the subwavelength regime. Recently, for achieving this purpose it has been proposed to exploit near-field interactions between radiating (bright) modes and lossless dark modes. However, this approach unveils challenging difficulties related to the excitation of dark modes through the near-field coupling with a bright mode. Here, it is experimentally and numerically shown how symmetry breaking applied to a nanoantenna dimer can conversely induce the excitation of plasmonic resonances, which play a key role for the dark modes’ activation in more complex nanoassemblies. On the basis of this study, a T-shaped nanoantenna trimer has been introduced as an elemental unit for the energy transfer between bright and dark modes in plasmonic nanostructures. Finally, we implemented an analytical perturbative model to further investigate the plasmonic hybridization of subwavelength systems

Superhydrophobic Surfaces as Smart Platforms for the Analysis of Diluted Biological Solutions

The aim of this paper is to expound on the rational design, fabrication and development of superhydrophobic surfaces (SHSs) for the manipulation and analysis of diluted biological solutions. SHSs typically feature a periodic array or pattern of micropillars; here, those pillars were modified to incorporate on the head, at the smallest scales, silver nanoparticles aggregates. These metal nanoclusters guarantee superior optical properties and especially SERS (surface enhanced Raman scattering) effects, whereby a molecule, adsorbed on the surface, would reveal an increased spectroscopy signal. On account of their two scale-hybrid nature, these systems are capable of multiple functions which are (i) to concentrate a solution, (ii) to vehicle the analytes of interest to the active areas of the substrate and, therefore, (iii) to measure the analytes with exceptional sensitivity and very low detection limits. Forasmuch, combining different technologies, these devices would augment the performance of conventional SERS substrates and would offer the possibility of revealing a single molecule. In this work, similar SHSs were used to detect Rhodamine molecules in the fairly low atto molar range. The major application of this novel family of devices would be the early detection of tumors or other important pathologies, with incredible advances in medicine

Detection of single amino acid mutation in human breast cancer by disordered plasmonic self-similar chain

Control of the architecture and electromagnetic behavior of nanostructures offers the possibility of designing and fabricating sensors that, owing to their intrinsic behavior, provide solutions to new problems in various fields. We show detection of peptides in multicomponent mixtures derived from human samples for early diagnosis of breast cancer. The architecture of sensors is based on a matrix array where pixels constitute a plasmonic device showing a strong electric field enhancement localized in an area of a few square nanometers. The method allows detection of single point mutations in peptides composing the BRCA1 protein. The sensitivity demonstrated falls in the picomolar (10-12 M) range. The success of this approach is a result of accurate design and fabrication control. The residual roughness introduced by fabrication was taken into account in optical modeling and was a further contributing factor in plasmon localization, increasing the sensitivity and selectivity of the sensors. This methodology developed for breast cancer detection can be considered a general strategy that is applicable to various pathologies and other chemical analytical cases where complex mixtures have to be resolved in their constitutive components

Median Fluorescence Intensity (MFI) of MHC-I, before and after mechanical stress.

<p>Panel A shows the decrease of the MHC class I molecules expression on cancer cells (5 melanoma and one lymphoblastoid cell lines) after mechanical stress treatment by means of the micropump (upper part) and the shock waves (lower part) compared with untreated cells. Panel B reports the effect of mechanical stress on some healthy cells (fibroblasts and macrophages) of the MHC class I with the two mentioned treatments. The related isotopic control MFI gave the same overlap signal for all cell lines used, therefore have been omitted. Panel C represents the statistical values of fold decrease of the MHC-I performed on melanoma cells (n = 4 separate experiment with micropump and n = 4 separate experiment with shock waves; p<0.05) and IM9 cells (n = 10 separate experiment with shock waves; p<0.0001). The fold decrease of MHC-I was derived from the Median Fluorescence Intensity (MFI) of MHC-I molecules before and after treatment of Melanoma and IM9 cell lines. The panel D shows the statistical values obtained from different experiment (n = 3) for each type of healthy cells. The fibroblasts and the PBLs were stressed with the micropump while, the macrophages and dendritic cells were treated with shock waves. The value reported in panel D is not statistically significant.</p

Western Blotting of MHC class I expression on the supernatants of treated samples: Tumor (A) and healthy cells (B) were analysed before and after mechanical stress by shock waves.

<p>MHC-I has molecular weight of 45 kDa. (C) Membrane incubated with Ponceau S red staining solution, as loading controls.</p

Fold increase of MHC-I mRNA from cancer and healthy cells after mechanical stress: Relative expression level of the MHC class I molecule was measured by qPCR on cells before and after applying micropump mechanical stress.

<p>Expression changes were related to unstressed samples. The results shown are the average of duplicates from 2 independent experiments. Error bars indicate standard deviations.</p

Principal component analysis.

<p>PCA analysis on control and stress cells for various cell lines; Mel 42a, Mel 59c, Mel 103b and 293T. a) PC1 vs. PC2, b) PC2 vs. PC3 and c) PC1 vs. PC3.</p