Nitric oxide-dependent pigment migration induced by ultraviolet radiation in retinal pigment cells of the crab Neohelice granulata

The purpose of this study was to verify the occurrence of pigment dispersion in retinal pigment cells exposed to UVA and UVB radiation, and to investigate the possible participation of a nitric oxide (NO) pathway. Retinal pigment cells from Neohelice granulata were obtained by cellular dissociation. Cells were analyzed for 30 min in the dark (control) and then exposed to 1.1 and 3.3 J cm⁻² UVA, 0.07 and 0.9 J cm⁻² UVB, 20 n m β-PDH (pigment dispersing hormone) or 10 μ m SIN-1 (NO donor). Histological analyses were performed to verify the UV effect in vivo . Cultured cells were exposed to 250 μ m L-NAME (NO synthase blocker) and afterwards were treated with UVA, UVB or β-PDH. The retinal cells in culture displayed significant pigment dispersion in response to UVA, UVB and β-PDH. The same responses to UVA and UVB were observed in vivo . SIN-1 did not induce pigment dispersion in the cell cultures. l-NAME significantly decreased the pigment dispersion induced by UVA and UVB but not by β-PDH. All retinal cells showed an immunopositive reaction against neuronal nitric oxide synthases. Therefore, UVA and UVB radiation are capable of inducing pigment dispersion in retinal pigment cells of Neohelice granulata and this dispersion may be nitric oxide synthase dependent.     

Retinyl palmitate polymeric nanocapsules as carriers of bioactives

Nanocapsules containing poly(d,l-lactide) shell and retinyl palmitate core have been prepared by the pre-formed polymer interfacial deposition method. Dynamic light scattering measurements yielded an average hydrodynamic diameter of ～220nm and a polydispersity index of ～0.12. Small-angle neutron scattering experiments revealed the presence of two populations of nanocapsules of core diameters ～192 and 65nm. Freeze fracture transmission electron microscopy showed a polydisperse population of nanocapsules (NC), with a poly(d,l-lactide) shell thickness between 11 and 3nm. For comparison purposes, nanoemulsions (NE, no polymer) and nanospheres (NS, polymer matrix) were also prepared. Each type of nanoparticles exhibited a different morphology (when examined by electron microscopy), in particular NC showed deformability by capillary adhesion. All three types of nanoparticles successfully encapsulated the poorly water-soluble molecules baicalein and benzophenone-3. The thermal behavior of the various nanoparticles was different to a physical mixture of its individual components. Cytotoxicity and phototoxicity assays, performed in human keratinocytes (HaCaT) and murine fibroblasts (BALB/c 3T3), showed that the NC were only cytotoxic at high concentrations. In vitro release studies of benzophenone-3, by the dialysis bag method using NC and NS, showed a sustained release; however, permeation studies using plastic surgery human abdominal skin in Franz diffusion cells showed that a higher amount of benzophenone-3 from NC penetrated into the skin, most probably due to the deformable nature of these nanoparticles.     

Decay rates for the magneto-micropolar system in $$\varvec{L^2(}\pmb {\mathbb {R}}^{\varvec{n)}}$$

In this paper, the large time decay of the magneto-micropolar fluid equations on \(\mathbb {R}^n\) (\( n=2,3\)) is studied. We show, for Leray global solutions, that \( \Vert ({\varvec{u}},{\varvec{w}},{\varvec{b}})(\cdot ,t) \Vert _{{L^2(\mathbb {R}^n)}} \rightarrow 0 \) as \(t \rightarrow \infty \) with arbitrary initial data in \( L^2(\mathbb {R}^n)\). When the vortex viscosity is present, we obtain a (faster) decay for the micro-rotational field: \( \Vert {\varvec{w}}(\cdot ,t) \Vert _{{L^2(\mathbb {R}^n)}} = o(t^{-1/2})\). Some related results are also included.     

New Approach to Determine the Phase Transition Temperature,Cloud Point,of Thermoresponsive Polymers

In this study, a novel method to determine the cloud point temperature variation in aqueous solutions of thermoresponsive homo- and copolymers was developed. Poly(N-vinylcaprolactam) (PVCL) and triblock copolymers of poly(t-butyl acrylate-co-acrylic acid)-b-poly(N-vinylcaprolactam)-b-(t-butyl acrylate-co-acrylic acid) (P[(tBA-co-AA)-b-PVCL-b-P(tBA-co-AA)] were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and used as models. The incorporation of AA units (hydrophilic segments) into the polymeric chain of PVCL influenced the phase transition, increasing the cloud point temperature of the final copolymer. The cloud point temperatures of the PVCL and the triblock copolymer P(tBA-co-AA)-b-PVCL-b-P(tBA-co-AA) were determined by measuring the transmittance of aqueous solutions of the polymers in a Turbiscan Lab instrument in the range of 29 to 40 C. This is the first study in which Turbiscan Lab is used to determine the cloud point temperature.     

Photostability and skin penetration of different E-resveratrol-loaded supramolecular structures

It is desirable and challenging to prevent E-resveratrol (E-RSV) from photoisomerizing to its Z-configuration to preserve its biological and pharmacological activities. The aim of this research was to evaluate the photostability of E-RSV-loaded supramolecular structures and the skin penetration profile of chemically and physically stable nanoestructured formulations. Different supramolecular structures were developed to act as carriers for E-RSV, that is, liposomes, polymeric lipid-core nanocapsules and nanospheres and solid lipid nanoparticles. The degrees of photostability of these formulations were compared with that of an ethanolic solution of E-RSV. The skin penetration profiles of the stable formulations were obtained using vertical diffusion cells (protected from light and under UVA radiation) with porcine skin as the membrane, followed by tape stripping and separation of the viable epidermis and dermis in a heated water bath. Photoisomerization was significantly delayed by the association of resveratrol with the nanocarriers independently of the supramolecular structure. Liposomes were the particles capable of maintaining E-RSV concentration for the longest time. On the other hand, E-RSV-loaded liposomes reduced in size showing low physical stability under UVA radiation. In the dark, the skin penetration profiles were very similar, but under UVA radiation the E-RSV-loaded nanocarriers showed increasing amounts in the total epidermis.     

Controlling the size of poly(hydroxybutyrate-co-hydroxyvalerate) nanoparticles prepared by emulsification–diffusion technique using ethanol as surface agent

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) nanospheres and oily nanocapsules were prepared by emulsification–diffusion technique. Controlled particle sizes were obtained employing binary mixtures of solvents (chloroform:ethanol) in the organic phase. Ethanol was chosen because of its dipole–dipole interaction with chloroform and its hydrogen bond with water. The smallest particles (from 253 to 493 nm) were obtained using a mixture of solvents composed of 70% ethanol and 30% chloroform (v/v) in the organic phase, while the largest particles (from 896 to 1568 nm) were obtained using chloroform exclusively. Independently of the organic phase composition, the nanoparticles showed unimodal distributions. Optical microscopy showed that the size of the primary emulsion droplets of the nanosphere formulations decreased with increasing ethanol concentrations in the organic phase. A simple empirical equation was developed correlating the nanoparticle diameters with the surface tension gradient coefficient multiplied by the ethanol molar concentration in the organic phase. The strategy showed that the control of the nanoparticle diameters, using emulsification–diffusion technique, could be achieved by adjusting the surface tension of the organic phase.     

Polyethylene/graphite nanocomposites obtained by in situ polymerization

The synthesis of polyethylene/graphite nanocomposites by in situ polymerization was achieved using the catalytic system Cp₂ZrCl₂ (bis(cyclopentadienyl)zirconium(IV) dichloride)/methylaluminoxane (MAO). Graphite with nano dimensions, previously treated with MAO, was added into the reactor as filler at percentages of 1, 2, and 5% (w/w). XRD analysis showed that the chemical and thermal treatments employed preserve the structure of the graphite sheets. The formation of graphite nanosheets and nanocomposites was confirmed by TEM and AFM. TEM micrographics showed that the polyethylene grew between the graphene nanosheets, giving intercalated and exfoliated graphite nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 692–698, 2010     

Reapplication improves the amount of sunscreen, not its regularity, under real life conditions

The sun protection factor (SPF) of sunscreens is determined using samples applied with a thickness of 2 mg cm(-2). Sunscreen users, however, typically apply sunscreen nonuniformly and in smaller amounts. The objective of our study was to verify whether sunscreen reapplication increases the amount and regularity of the product on the skin. Volunteers were asked to apply an SPF 6 sunscreen on their forearms and reapply it 30 min later on one forearm. Tape-strips were used to collect five samples from two different sites on each forearm. The concentration of benzophenone-3 in the samples was measured and the total amount of sunscreen was estimated using high-performance liquid chromatography. The median amount of sunscreen film was 0.43 mg cm(-2) (0.17-1.07) after one application and 0.95 mg cm(-2) (0.18-1.91) after two applications (P = 0.002). No significant difference was found in the film uniformity. Though sunscreen reapplication increases the amount of product on the skin, levels are still lower than the recommended amount, confirming that the protection level is less than the product-stated SPF. Our results are the first in the literature to support the recommendation for reapplying sunscreens. Based on our results, we recommend that sunscreens be labeled using qualitative measures.     

Polymeric nanocapsules ultra stable in complex biological media

Non-specific protein adsorption from complex biological media, especially from blood plasma, is an urgent challenge for the application of nanoparticles as delivery systems, diagnostics, and other biomedical application. Nanocapsules (NC) prepared from FDA-approved degradable poly(ɛ-caprolactone) shell and Mygliol 812^® oil in the core were coated with mono-methoxy terminated oligo(ethylene glycol) methacrylate (poly(MeOEGMA)) polymer brush layers with a well-controlled thickness at the nanometer scale up to 350 nm using surface initiated atom transfer radical polymerization in water or phosphate buffered saline. Incubation of uncoated NC with human serum albumin solution, fetal bovine serum, or human blood plasma resulted in fast aggregation observed by dynamic light scattering as an increase in diameter of particles present in the solutions. Conversely, these biological fluids affected only marginally the size distribution of the NC coated with a 60 nm thick poly(MeOEGMA) layer. The high suspension stability of the coated NC in complex biological fluids was related to the suppressed deposition of proteins from these fluids observed by surface plasmon resonance (SPR) on analogous poly(MeOEGMA) layer prepared on flat surfaces of SPR chips.