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Large-scale hierarchical macroscopic moire gratings resembling the surface structure of Peruvian lily flower petals are fabricated on azobenzene molecular glass thin films using a Lloyd’s mirror interferometer. It is shown that nanostructured linear and crossed moire gratings can be made with pitch values reaching a few millimeters. Also, using atomic force microscopy, scanning electron microscopy, optical microscopy, and surface profilometry techniques, it is shown that the obtained moire gratings have two-fold or three-fold hierarchical structures fabricated using a simple all optical technique.

Optofluidic sensors based on periodic arrays of subwavelength apertures that support surface plasmon resonance can be employed as both optical sensors and nanofluidic structures. In flow-through operation, the nanoapertures experience pressure differences across the substrate in which they are fabricated, which imposes the risk for structural failure. This work presents an investigation of the deflection and structural stability of nanohole array-based optofluidic sensors operating in flow-through mode. The analysis was approached using experiments, simulations via finite element method, and established theoretical models. The results depict that certain areas of the sensor deflect under pressure, with some regions suffering high mechanical stress. The offset in the deflection values between theoretical models and actual experimental values is overturned when only the effective area of the substrate, of 450 &micro, m, is considered. Experimental, theoretical, and simulation results suggest that the periodic nanostructures can safely operate under trans-membrane pressures of up to 20 psi, which induce deflections of up to ~20 &mu, m.

Nanostructures consisting of crossed surface relief gratings (CSRGs) support surface plasmon resonances (SPRs) that are compatible with biosensing applications [1], [2]. At normal incidence, surface plasmons are excited between a metal and a dielectric at a light wavelength ( $\lambda_{\text{SPR}}$ ) given by $\lambda_{SPR}=n\Lambda[\sqrt{\varepsilon_{m}/(n^{2}+\varepsilon_{m})}]$ , where $n$ is the index of refraction of the dielectric, and $\varepsilon_{m}$ is the real part of the permittivity of the metal and $\Lambda$ is the grating pitch. When placed between crossed linear polarizers, CSRGs allow for plasmonic energy exchange between the two superimposed gratings that eliminate any incident polychromatic light, except for the narrow SPR bandwidth where polarization conversion occurs. The result is an effective transmission of the SPR signal with a high signal-to-noise ratio. The single pitch of CSRGs, however, limit their operation to a specific plasmonic resonance wavelength. Here, we present a plasmonic sensor based on variable-pitch CSRG that allows plasmonic resonances at different wavelength bandwidth depending on the illuminated region. The variable-pitch CSRGs (VP-CSRGs) are fabricated on azobenzene-functionalized films through a simple two-step procedure. Fig. 1a presents an actual AFM image of the surface of a nanofabricated VP-CSRGs. The plasmonic response of the VP-CSRG sensor was evaluated using Finite-Difference Time-Domain (FDTD) simulations to show the e-field intensity distribution on the gold-coated VP-CSRG surface. Electric field enhancement and distribution, due to the plasmonic conversion, was assessed through the change of the RI of the dielectric medium in contact with the metallic crossed gratings, and through the spectral diversity of the light source to excite the surface plasmons. For the simulations, the surface of the CSRGs with pitches of 520, 540 and 560 nm were modeled using the function, $f(x, y)=G(\cos[(2\pi/p)x]+\cos[(2\ \pi/p)y])$ , where $G$ is the amplitude and $p$ the period of the structure (Fig. 1a). The simulations were used to obtain the e-field intensity distribution, normalized with respect to the incident plane wave. Periodic boundary conditions in both $x$ and $y$ directions and a perfectly matched layer (PML) in the $z$ direction were used for the analysis region. A uniform mesh size of 3 nm was used for the envelope of the nanostructure, comprising the azobenzene layer, the gold film and the dielectric medium, in all the directional axes. A plane wave, polarized along the $y$ -axis and orthogonal to the $x-y$ plane, was employed to induce a SPR in the structure. Fig. 1b demonstrates the plasmonic excitation in the $x$ -direction, when using p-polarized light and the absence of plasmonic excitation in the $y$ -direction. However, when s-polarized light is used, the nanostructures are excited in the $y$ -direction. These results present an evidence on the unique plasmonic energy transfer between the crossed gratings that has been hypothesised before [1]. Experimentally, these results can be used to confirm that the transmitted light acquired in a collinear setup using VP-CSRGs between two orthogonal polarizers corresponds, only, to the plasmonic signature of the nanostructure.

Two-dimensional chirped-pitch crossed surface relief gratings (CP-CSRGs) were fabricated on azobenzene-functionalized thin films using a simple two-step procedure. The resulting gratings had a constant pitch in one direction and a varying (chirped) pitch in the orthogonal direction. They were coated with silver and tested for their ability to change the polarization of surface plasmon resonance (SPR) signals, when placed between crossed polarizers. It was observed that several different bandwidths of SPR wavelengths are excitable using a single device, making CP-CSRGs suitable as next generation SPR-based sensors. The SPR wavelengths shifted as much as 10.5 nm/mm along the chirped grating, and a maximum sensitivity of 778.6 nm/RIU was obtained when detecting the refractive index change of various concentrations of aqueous sucrose solutions.

The pharmacological manipulation of Liver X Receptors (LXRs) has been an attractive therapeutic strategy for atherosclerosis treatment as they control reverse cholesterol transport and inflammatory response. In this study, we present the development and efficacy of nanoparticles (NPs) incorporating the synthetic LXR agonist GW3965 (GW) in targeting atherosclerotic lesions. Collagen IV (Col IV) targeting ligands were employed to functionalize the NPs to improve targeting to the atherosclerotic plaque, and formulation parameters such as the length of the polyethylene glycol (PEG) coating molecules were systematically optimized. In vitro studies indicated that the GW-encapsulated NPs upregulated the LXR target genes and downregulated pro-inflammatory mediator in macrophages. The Col IV-targeted NPs encapsulating GW (Col IV-GW-NPs) successfully reached atherosclerotic lesions when administered for 5 weeks to mice with preexisting lesions, substantially reducing macrophage content (~30%) compared to the PBS group, which was with greater efficacy vs. non-targeting NPs encapsulating GW (GW-NPs) (~18%). In addition, mice administered the Col IV-GW-NPs did not demonstrate increased hepatic lipid biosynthesis or hyperlipidemia during the treatment period, unlike mice injected with the free GW. These findings suggest a new form of LXR-based therapeutics capable of enhanced delivery of the LXR agonist to atherosclerotic lesions without altering hepatic lipid metabolism.