Rotational Doppler shift of the phase-conjugated photon

The rotational Doppler shift of a photon with orbital angular momentum $\pm \ell \hbar$ is shown to be an even multiple of the angular frequency $\Omega$ of the reference frame rotation when photon is reflected from the phase-conjugating mirror. We consider the one-arm phase-conjugating interferometer which contains $N$ Dove prisms or other angular momentum altering elements rotating in opposite directions. When such interferometer is placed in the rotating vehicle the $\delta \omega=4 (N+1/2) \ell \cdot \Omega$ rotational Doppler shift appears and rotation of the helical interference pattern with angular frequency $\delta \omega /{2 \ell}$ occurs. The accumulation of angular Doppler shift via successive passage through the $N$ image-inverting prisms is due to the phase conjugation, for conventional parabolic retroreflector the accumulation is absent. The features of such a vortex phase conjugating interferometry at the single photon level are discussed.Comment: 6 pages, 3 figures, submitted to referred journa

Nanostructured polymeric coatings based on chitosan and dopamine-modified hyaluronic acid for biomedical applications

In a marine environment, specific proteins are secreted by mussels and used as a bioglue to stick to a surface. These mussel proteins present an unusual amino acid 3,4-dihydroxyphenylalanine (known as DOPA). The outstanding adhesive properties of these materials in the sea harsh conditions have been attributed to the presence of the catechol groups present in DOPA. Inspired by the structure and composition of these adhesive proteins, we used dopamine-modified hyaluronic acid (HA-DN) prepared by carbodiimide chemistry to form thin and surface-adherent dopamine films. This conjugate was characterized by distinct techniques, such as nuclear magnetic resonance and ultraviolet spectrophotometry. Multilayer films were developed based on chitosan and HA-DN to form polymeric coatings using the layer-by-layer methodology. The nanostructured films formation was monitored by quartz crystal microbalance. The film surface was characterized by atomic force microscopy and scanning electron microscopy. Water contact angle measurements were also conducted. The adhesion properties were analyzed showing that the nanostructured films with dopamine promote an improved adhesion. In vitro tests showed an enhanced cell adhesion, proliferation and viability for the biomimetic films with catechol groups, demonstrating their potential to be used in distinct biomedical applications.The authors want to acknowledge the COST Action TD0906 - Biological adhesives: from biology to biomimetics. The authors also acknowledge the financial support from the Fundacao para a Ciencia e para a Tecnologia through the Ph.D. grants with the references SFRH/BD/73119/2010 and SFRH/BD/69529/2010. G. G. Ferrer acknowledges the support of the Spanish Ministry of Science and Innovation for the mobility grant JC2008-00135. G. Botelho acknowledges the NMR portuguese network (PTNMR, Bruker Avance III 400-Univ. Minho)

Applications and Emerging Trends of Hyaluronic Acid in Tissue Engineering, as a Dermal Filler, and in Osteoarthritis Treatment

Hyaluronic acid (HA) is a naturally occurring biodegradable polymer with a variety of applications in medicine including scaffolding for tissue engineering, dermatological fillers, and viscosupplementation for osteoarthritis treatment. HA is available in most connective tissues in body fluids such as synovial fluid and the vitreous humor of the eye. HA is responsible for several structural properties of tissues as a component of extracellular matrix (ECM) and is involved in cellular signaling. Degradation of HA is a step-wise process that can occur via enzymatic or non-enzymatic reactions. A reduction in HA mass or molecular weight via degradation or slowing of synthesis affects physical and chemical properties such as tissue volume, viscosity, and elasticity. This review addresses the distribution, turnover, and tissue-specific properties of HA. This information is used as context for considering recent products and strategies for modifying the viscoelastic properties of HA in tissue engineering, as a dermal filler, and in osteoarthritis treatment

Interactions between metal oxides and biomolecules: from fundamental understanding to applications

Metallo-oxide (MO) based bioinorganic nanocomposites promise unique structures, physico-chemical properties and novel bio-chemical functionalities and within the last decade, investment in research on materials such as ZnO, TiO2, SiO2 and GeO2 has significantly increased. Besides traditional approaches, the synthesis, shaping, structural patterning and post-processing chemical functionalization of the materials surface is inspired by strategies which mimic processes in nature. Would such materials deliver new technologies? Answering this question requires the merging of historical knowledge and current research from different fields of science. Practically, we need an effective defragmentation of the research area. From our perspective, the superficial accounting of material properties, chemistry of the surfaces and the behaviour of biomolecules next to such surfaces is a problem. This is particularly of concern when we wish to bridge between technologies in vitro and biotechnologies in vivo. Further, besides the potential practical technological efficiency and advantages such materials might exhibit, we have to consider the wider long-term implications of material stability and toxicity. In this contribution we present a critical review of recent advances in the chemistry and engineering of MO based biocomposites highlighting the role of interactions at the interface and the techniques by which these can be studied. At the end of the article we outline the challenges which hamper progress in research and extrapolate to developing and promising directions including additive manufacturing and synthetic biology that could benefit from molecular level understanding of interactions occurring between inanimate (abiotic) and living (biotic) materials

Transactivation from Gal4-VP16 transgenic insertions for tissue-specific cell labeling and ablation in zebrafish

Prior studies with transgenic zebrafish confirmed the functionality of the transcription factor Ga14 to drive expression of other genes under the regulation of upstream activator sequences (UAS). However, widespread application of this powerful binary system has been limited, in part, by relatively inefficient techniques for establishing transgenic zebrafish and by the inadequacy of Ga14 to effect high levels of expression from UAS-regulated genes. We have used the Tol2 transposition system to distribute a self-reporting gene/enhancer trap vector efficiently throughout the zebrafish genome. The vector uses the potent, hybrid transcription factor Gal4-VP16 to activate expression from a UAS:eGFP reporter cassette. In a pilot screen, stable transgenic lines were established that express eGFP in reproducible patterns encompassing a wide variety of tissues, including the brain, spinal cord, retina, notochord, cranial skeleton and muscle, and can transactivate other UAS-regulated genes. We demonstrate the utility of this approach to track Gal4-VP16 expressing migratory cells in UAS.-Kaede transgenic fish, and to induce tissue-specific cell death using a bacterial nitroreductase gene under UAS control. The Tol2-mediated gene/enhancer trapping system together with UAS transgenic lines provides valuable tools for regulated gene expression and for targeted labeling and ablation of specific cell types and tissues during early zebrafish development. (c) 2007 Elsevier Inc. All rights reserved