V. Marrocco

Photonic Crystal Sensors

The paper deals with the possibility of using photonic crystals for sensing purpose. The optical properties of photonic crystals allow to realize sensing devices characterized by a high degree of compactness and a good resolution of the quantity to detect. A particular attention is devoted to force/pressure sensors and the design of a PhC microcavity pressure sensor is reported

PKC Theta Ablation Improves Healing in a Mouse Model of Muscular Dystrophy

Inflammation is a key pathological characteristic of dystrophic muscle lesion formation, limiting muscle regeneration and resulting in fibrotic and fatty tissue replacement of muscle, which exacerbates the wasting process in dystrophic muscles. Limiting immune response is thus one of the therapeutic options to improve healing, as well as to improve the efficacy of gene- or cell-mediated strategies to restore dystrophin expression. Protein kinase C θ (PKCθ) is a member of the PKCs family highly expressed in both immune cells and skeletal muscle; given its crucial role in adaptive, but also innate, immunity, it is being proposed as a valuable pharmacological target for immune disorders. In our study we asked whether targeting PKCθ could represent a valuable approach to efficiently prevent inflammatory response and disease progression in a mouse model of muscular dystrophy. We generated the bi-genetic mouse model mdx/θ−/−, where PKCθ expression is lacking in mdx mice, the mouse model of Duchenne muscular dystrophy. We found that muscle wasting in mdx/θ−/− mice was greatly prevented, while muscle regeneration, maintenance and performance was significantly improved, as compared to mdx mice. This phenotype was associated to reduction in inflammatory infiltrate, pro-inflammatory gene expression and pro-fibrotic markers activity, as compared to mdx mice. Moreover, BM transplantation experiments demonstrated that the phenotype observed was primarily dependent on lack of PKCθ expression in hematopoietic cells. These results demonstrate a hitherto unrecognized role of immune-cell intrinsic PKCθ activity in the development of DMD. Although the immune cell population(s) involved remain unidentified, our findings reveal that PKCθ can be proposed as a new pharmacological target to counteract the disease, as well as to improve the efficacy of gene- or cell- therapy approaches.

Intracellular signaling in ER stress-induced autophagy in skeletal muscle cells

Skeletal muscle remodeling in response to muscle disuse and unloading is known to be associated with so‐called ER stress, which, in turn, activates autophagy and contributes to muscle atrophy. Different molecules are involved in ER stress‐induced autophagy, among which PKCθ has recently been described. In this study, we dissected both in vitro and in vivo ER stress‐induced autophagy pathways in muscle. Using C2C12 muscle cells in culture, we demonstrated that PKC activation induced autophagy in the absence of ER stress. We further demonstrated that PKCθ was strongly activated in cultured myoblasts and myotubes during ER stress induced by different stimuli, such as TG or TN treatment, and that it localized into Lc3‐positive autophagic dots upon TG treatment. Neither Akt dephosphorylation nor Foxo or GSK3β activation was observed in these conditions. Moreover, PKCθ inhibition in myoblasts and myotubes prevented ER stress‐induced Lc3 activation and autophagic dot formation, but not ER stress. In vivo, lack of PKCθ prevented both food deprivation‐ and immobilization‐induced autophagy and muscle atrophy, irrespective of Akt pathway inhibition. Taken together, these results demonstrate that PKCθ functions as an ER stress sensor in skeletal muscle, required for ER‐stress‐dependent autophagy activation, and can be proposed as a novel molecular target to maintain muscle homeostasis in response to external stimuli, such as disuse and unloading, still allowing intracellular clearance.—Madaro, L., Marrocco, V., Carnio, S., Sandri, M., Bouché, M. Intracellular signaling in ER stress‐induced autophagy in skeletal muscle cells. FASEB J. 27, 1990–2000 (2013). www.fasebj.org

PKCθ signaling is required for myoblast fusion by regulating the expression of caveolin-3 and β1D integrin upstream focal adhesion kinase

Using both in vivo and in vitro protein kinase C (PKC) θ mutant models, we found that PKCθ, the PKC isoform predominantly expressed in skeletal muscle, is required for myoblast fusion and myofiber growth, by regulating focal adhesion kinase activity and, in turn, the expression of the pro-fusion genes caveolin-3 and β1D-integrin.

Experimental demonstration of a novel bio‑sensing platform via plasmonic band gap formation in gold nano‑patch arrays

In this paper we discuss the possibility of implementing a novel bio-sensing platform based on the observation of the shift of the leaky surface plasmon mode that occurs at the edge of the plasmonic band gap of metal gratings, when an analyte is deposited on top of the metallic structure. We report numerical calculations, fabrication and experimental measurements to prove the sensing capability of a two-dimensional array of gold nano-patches in the detection of a small quantity of Isopropyl Alcohol (IPA) deposited on top of sensor surface. The calculated sensitivity of our device approaches a value of 1000 nm/RIU with a corresponding Figure of Merit (FOM) of 222 RIU(-1). The presence of IPA can also be visually estimated by observing a color variation in the diffracted field. We show that color brightness and intensity variations can be ascribed to a change in the aperture size, keeping the periodicity constant, and to different types of analyte deposited on the sample, respectively. Moreover, we demonstrate that unavoidable fabrication imperfections revealed by the presence of rounded corners and surface roughness do not significantly affect device performance.

Plasmonic bandgap formation in two-dimensional periodic arrangements of gold patches with subwavelength gaps

We report on the formation of plasmonic bandgaps in two-dimensional periodic arrangements of gold patches. Orthogonal arrays of subwavelength slits with different periodicities have been studied by means of a three-dimensional finite-difference time-domain (FDTD) code, changing incident polarization and geometrical parameters. Spectral response of gold patches having different a form factor and surrounded by different media have been also investigated and compared in order to give a full description of bandgap shifts paving the way for the design of polarization-sensitive devices.

Photonic Crystal Drop Filter Exploiting Resonant Cavity Configuration

Band dropping devices are widely used in WDM application. In this paper the design of a two-dimensional photonic crystal drop filter is proposed. Different from the configuration reported in literature which are realized by means of a photonic bandgap waveguide and one or more resonant cavities, able to select a signal at desired frequency, the proposed drop filters exploits a novel system of point defects. The design is based on the accurate analysis of higher order resonant modes supported by the system and their parities. The temporal and spectral behavior of the device is studied using plane wave expansion (PWE) and FDTD methods.

RESONANCE WAVELENGTH DEPENDENCE AND MODE FORMATION IN GOLD NANOROD OPTICAL ANTENNAS WITH FINITE THICKNESS

In this paper we analyze the dependence of the resonance wavelength and mode formation of an optical gold nanorod antenna on its geometrical parameters in the wavelength range 500{1400nm. In particular, we prove that nanoantennas difier from RF counterparts, since the minima and maxima, i.e., nodes and anti-nodes, of the resonant modes do not go to zero and show very intense peak at the corners due to non-negligible thickness. Moreover, FDTD simulations reveal that the usually considered linear relation between the resonant wavelength and the nanorod length has to be modifled when the nanorod thickness is taken into account.

Active InGaAsP/InP Photonic Bandgap Waveguides for Wavelength-Selective Switching

An active optical switch based on the InGaAsP/InP photonic bandgap (PBG) buried waveguide is proposed. The device, which is made of a periodic grating patterned on a buried waveguide, exploits the localization of states in the PBG induced by the presence of an active defect. The wavelength of the localized state can be shifted by properly choosing the defect length and the injected current density in order to achieve a wavelength-selective switching behavior. Proprietary codes based on the bidirectional beam propagation method and the method of lines (BBPM-MoL) were used for the simulations of the optical device taking into account the rate equations to model the interaction between the optical signal and the active medium. Design curves are provided and parameterized to give general design rules. From the numerical analysis, the proposed device exhibits good theoretical performances in terms of crosstalk (CT <;-20 dB), modulation depth (MD >;0.9), response time (in the subnanosecond range), and maximum size (<;170 μm).

Efficient plasmonic nanostructures for thin film solar cells

Recent scientific publications have highlighted the possibility of enhancing solar conversion efficiency in thin film solar cells using surface plasmon (SP) waves and resonances. One main strategy is to deposit layers of metal nanoparticles on the top of a thin film silicon solar cell which can increase light absorption and consequently the energy conversion in the frequency range where the silicon intrinsic absorptance is low. In this paper, we investigate the effects produced on the light absorption and scattering by silver nanoparticles, arranged in a periodic pattern, placed on the top of amorphous silicon (α-Si) thin layer. We propose different geometry of metal objects, quantifying the scattering (back and forward) determined by the nanoparticles in dependence of their shapes and Si thickness. The analysis reveals that the thickness of the substrate has huge influence on the scattering, in particular on the back one, when the nanoparticles have corners, whereas it seems less dramatic when rounded profiles are considered (nanospheres).