Light Self-Trapping in Polymeric Media based on Polymethylmethacrylate with Distributed Phenanthrenequinone Molecules

Among the optical effects that are intensively investigated in recent decades is the phenomenon of self-action of light beams in nonlinear optical media, which is characterized by a refractive index depending on the intensity of the light wave (e.g. self-trapping and self-focusing of optical beams, self-phase modulation of optical pulses etc.). The interaction of the light with a nonlinear material allows to realize the direct optical conversion of images and to control the space-time light structure. The formations of localized spatial structures, so-called optical solitons, which are solutions of the nonlinear differential equations describing such phenomena, are the focus of scientific and practical interest [1-6]. The reason for these intensive studies of solitons is the possibility of their use in modern communication systems, like high-speed systems of fiber-optical information transfer, including self-trapping structure formation due to nonlinear optical effects, creation of waveguiding optical elements with tunable characteristics etc. Owing to diffraction, a collimated beam of light with a diameter d usually spreads with an angle of λ / d. However, already almost 50 years ago it was found that this spreading could be avoided in a nonlinear optical medium, which possesses an intensity-dependent index of refraction that increases with light intensity [7-9]. As a result, the beam forms a dielectric waveguide for itself with solitons as self-trapping solutions. These optical spatial solitons correspond to self-directed beams, which are limited in the across-track direction orthogonal to the direction of propagation [1]. Thereby the natural diffraction divergence of the propagating beam is compensated by the refraction of light when the refractive index is higher in the central part of the beam than at its periphery. The effect of the suppression of the diffraction by the local variation of the refractive index occurs therefore as a result of the exceptional properties of nonlinear media (i.e. the nonlinear increase of the refractive index in a region with higher intensity), leading to the spatial self-focusing of the beam. There is a dynamic balancing between diffraction of the beam and self-focusing due to the nonlinearity of the medium. Since the light wave is captured in an area with higher refractive index, such an area represents a waveguide or self-written channel, thus forming a Chapter 1. Introduction 2 spatial soliton structure. If several of such light channels are formed in parallel, an interaction between them can happen [6]. In other words, solitons propagate and interact with each another while displaying properties that are associated with real particles (quasi-particles)

Cardiac multiscale bioimaging: from nano- through micro- to mesoscales.

Cardiac multiscale bioimaging is an emerging field that aims to provide a comprehensive understanding of the heart and its functions at various levels, from the molecular to the entire organ. It combines both physiologically and clinically relevant dimensions: from nano- and micrometer resolution imaging based on vibrational spectroscopy and high-resolution microscopy to assess molecular processes in cardiac cells and myocardial tissue, to mesoscale structural investigations to improve the understanding of cardiac (patho)physiology. Tailored super-resolution deep microscopy with advanced proteomic methods and hands-on experience are thus strategically combined to improve the quality of cardiovascular research and support future medical decision-making by gaining additional biomolecular information for translational and diagnostic applications

Optical, electrical and chemical properties of PEO:I2 complex composite films

Synthesized PEO:I2 complex composite films with different I2 concentrations were deposited onto fused silica substrates using a dip-coating method. Incorporation of PEO films with I2 increases the electrical conductivity of the composite, reaching a maximum of 46 mS/cm for 7 wt% I2. The optical and optoelectronic properties of the complex composite films were studied using the transmittance and reflectance spectra in the UV-Vis region. The transmittance of PEO decreases with increasing I2 content. From this study, the optical bandgap energy decreases from 4.42 to 3.28 eV as I2 content increases from 0 to 7 wt%. In addition, the refractive index for PEO films are in the range of 1.66 and 2.00.1H NMR spectra of pure PEO film shows two major peaks at 3.224 ppm and 1.038 ppm, with different widths assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase, respectively. By adding I2 to the PEO, both peaks (amorphous and crystal) are shifted to lower NMR frequencies indicating that I2 is acting as a Lewis acid, and PEO is acting as Lewis base. Hence, molecular iodine reacts favorably with PEO molecules through a charge transfer mechanism, and the formation of triiodide (I3-), the iodite (IO2-) anion, I 2· · · PEO and I2+···PEO complexes. PEO:I2 complex composite films are expected to be suitable for optical, electrical, and optoelectronic applications

Linear and Non-Linear Optical Imaging of Cancer Cells with Silicon Nanoparticles

New approaches for visualisation of silicon nanoparticles (SiNPs) in cancer cells are realised by means of the linear and nonlinear optics in vitro. Aqueous colloidal solutions of SiNPs with sizes of about 10–40 nm obtained by ultrasound grinding of silicon nanowires were introduced into breast cancer cells (MCF-7 cell line). Further, the time-varying nanoparticles enclosed in cell structures were visualised by high-resolution structured illumination microscopy (HR-SIM) and micro-Raman spectroscopy. Additionally, the nonlinear optical methods of two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS) with infrared laser excitation were applied to study the localisation of SiNPs in cells. Advantages of the nonlinear methods, such as rapid imaging, which prevents cells from overheating and larger penetration depth compared to the single-photon excited HR-SIM, are discussed. The obtained results reveal new perspectives of the multimodal visualisation and precise detection of the uptake of biodegradable non-toxic SiNPs by cancer cells and they are discussed in view of future applications for the optical diagnostics of cancer tumours

Iron-induced complement dysregulation in the retinal pigment epithelium: implications for age-related macular degeneration

Age-related macular degeneration (AMD), typically manifesting as a loss of central vision in elderly persons, is a leading cause of blindness in highly developed nations. AMD is a multifactorial disease associated with aging, oxidative stress, complement dysregulation, dsRNA toxicity, among many other possible factors. The formation of extracellular deposits, termed drusen, below the retinal pigment epithelial (RPE) cell layer in the outer retina is a pathognomonic hallmark of AMD. The composition of drusen is complex, but identified elements include iron, complement components, and amyloid protein derivatives. This suggests that iron may be involved in the pathophysiology of AMD. Further support for this hypothesis comes from mice lacking ferroxidases Ceruloplasmin (Cp) and Hephaestin (Heph), which have a primary genetic defect in iron homeostasis. These mice develop some AMD-like morphological features and a telling molecular feature: activated complement component 3 (C3) fragment deposition at the basolateral aspect of the RPE (the location of drusen in AMD). In our studies, we investigated the molecular mechanisms by which C3 is up-regulated by iron in RPE cells. ERK1/2, SMAD3, and CCAAT/enhancer-binding protein-δ (C/EBP-δ) are part of a non-canonical TGF-β signaling pathway that is responsible for iron-induced C3 expression. Pharmacologic inhibition of either ERK1/2 or SMAD3 phosphorylation decreased iron-induced C3 expression levels. Knockdown of SMAD3 blocked the iron-induced up-regulation and nuclear accumulation of C/EBP-δ, a transcription factor known to promote C3 expression by binding to the basic leucine zipper (bZIP1) domain of the gene promoter. We show herein that mutation of this domain reduced iron-induced C3 promoter activity. The molecular events in the iron-C3 pathway represent therapeutic targets for AMD. To better understand the relative contribution of systemic iron and local dysregulation of iron homeostasis to RPE iron accumulation, we used Bmp6 KO mice and WT mice and found that retinal hepcidin levels are not changed, but in fact may be slightly greater in KO compared to WT mice. As such, systemic iron overload by genetic KO or intravenous supplementation in WT mice resulted in increased RPE labile iron and oxidative stress, suggesting that systemic iron overload may lead to retinal iron overload despite the presence of an intact blood retinal barrier. Systemic iron status appears to be a leading determinant of retinal iron status

Highly concentrated phenanthrenequinone– polymethylmethacrylate composite for thick reflection holograms recording at 532 nm

The formation of stable phase reflection holograms in highly-concentrated phenanthrenequinone - polymethylmethacrylate (PQ-PMMA) layers with a thickness of about 100 μm at 532 nm recording wavelength has been investigated. In spite of the low absorbance of the photosensitive material at the long wave edge of the absorption spectrum, a refractive index modulation of 4.2·10−4 close to the practically reachable limit was achieved during the optical recording. Quantitative investigation of thermal and light treatment of the recorded holograms has demonstrated a tenfold increase of the diffraction efficiency (up to 60%) without disturbing the angular selectivity profile

Highly concentrated phenanthrenequinone – polymethylmethacrylate composite for thick reflection holograms recording at 532 nm

The formation of stable phase reflection holograms in highly-concentrated phenanthrenequinone - polymethylmethacrylate (PQ-PMMA) layers with a thickness of about 100 µm at 532 nm recording wavelength has been investigated. In spite of the low absorbance of the photosensitive material at the long wave edge of the absorption spectrum, a refractive index modulation of 4.2·10−4 close to the practically reachable limit was achieved during the optical recording. Quantitative investigation of thermal and light treatment of the recorded holograms has demonstrated a tenfold increase of the diffraction efficiency (up to 60%) without disturbing the angular selectivity profile

Optical Sectioning and High Resolution in Single-Slice Structured Illumination Microscopy by Thick Slice Blind-SIM Reconstruction.

The microscope image of a thick fluorescent sample taken at a given focal plane is plagued by out-of-focus fluorescence and diffraction limited resolution. In this work, we show that a single slice of Structured Illumination Microscopy (two or three beam SIM) data can be processed to provide an image exhibiting tight sectioning and high transverse resolution. Our reconstruction algorithm is adapted from the blind-SIM technique which requires very little knowledge of the illumination patterns. It is thus able to deal with illumination distortions induced by the sample or illumination optics. We named this new algorithm thick slice blind-SIM because it models a three-dimensional sample even though only a single two-dimensional plane of focus was measured

Linear and Non-Linear Optical Imaging of Cancer Cells with Silicon Nanoparticles

New approaches for visualisation of silicon nanoparticles (SiNPs) in cancer cells are realised by means of the linear and nonlinear optics in vitro. Aqueous colloidal solutions of SiNPs with sizes of about 10–40 nm obtained by ultrasound grinding of silicon nanowires were introduced into breast cancer cells (MCF-7 cell line). Further, the time-varying nanoparticles enclosed in cell structures were visualised by high-resolution structured illumination microscopy (HR-SIM) and micro-Raman spectroscopy. Additionally, the nonlinear optical methods of two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS) with infrared laser excitation were applied to study the localisation of SiNPs in cells. Advantages of the nonlinear methods, such as rapid imaging, which prevents cells from overheating and larger penetration depth compared to the single-photon excited HR-SIM, are discussed. The obtained results reveal new perspectives of the multimodal visualisation and precise detection of the uptake of biodegradable non-toxic SiNPs by cancer cells and they are discussed in view of future applications for the optical diagnostics of cancer tumours

Results of 3D simulation with <i><b>thick slice</b></i> reconstruction.

<p>a) Resolution test target placed in the focal plane of our simulated sample. 800nm out-of-focus was a <i>π</i>/2-rotated version of the same structure. b) 2D WF deconvolution. c) Focal slice of 3D WF deconvolution of the entire WF image stack. d)One of the 9 simulated SIM images. Here we simulate a two-beam SIM. e) 2D blind reconstruction of (d) containing out-of-focus light. f) <i>Thick slice</i> blind-SIM result, showing optical sectioning and high resolution. g-i) Simulation as in a-f) but with a distorted illumination pattern as depicted in g) (zoom). h)Reconstructed illumination function. i) <i>Thick slice</i> blind-SIM reconstruction of the object described in (a) but illuminated with the distorted pattern(g). Scale bar: 2.5 <i>μ</i>m.</p