Highlights on the Binding of Cobalta-Bis-(Dicarbollide) with Glucose Units

Metalla-bis-dicarbollides, such as the cobalta-bis-dicarbollide (COSAN) anion [Co(C₂B₉H₁₁)₂]⁻, have attracted much attention in biology but a deep understanding of their interactions with cell components is still missing. For this purpose, we studied the interactions of COSAN with the glucose moiety, which is ubiquitous at biological interfaces. Octyl-glucopyranoside surfactant (C8G1) was chosen as a model as it self-assembles in water and creates a hydrated glucose-covered interface. At low COSAN content and below the critical micellar concentration (CMC) of C8G1, COSAN binds to C8G1 monomers through the hydrophobic effect. Above the CMC of C8G1, COSAN adsorbs onto C8G1 micelles through the superchaotropic effect. At high COSAN concentrations, COSAN disrupts C8G1 micelles and the assemblies become similar to COSAN micelles but with a small amount of solubilized C8G1. Therefore, COSAN binds in a versatile way to C8G1 through either the hydrophobic or superchaotropic effect depending on their relative concentrations.     

A family of fluorenyl dendrons for porphyrin dendrimers synthesis

A series of dendrons bearing various number of fluorenyl donor groups have been synthesized. First, the reference compound 2-(bromomethyl)-9H-fluorene (8) with one fluorenyl unit, then dendron 10, with two fluorenyl arms, and finally new generation dendrons, 11 and 12, bearing four peripheral fluorenyl arms were synthesized and characterized. A series of different generations of porphyrin dendrimers, obtained from these dendrons are also presented. Preliminary results on higher generation dendrimers are reported as well. Under mild basic conditions, surprisingly, a new compound 1 incorporating a fluorenyl unit in the cycle and three pendant fluorenyl arms was obtained by an intramolecular reaction of brominated tetrapod dendron 12.     

Three-dimensional visualization of stratified turbulent wakes at varying Reynolds number

Journal of Visualization - We present a series of three-dimensional visualizations of numerically simulated turbulent wakes in a stably stratified fluid with a focus on the effects of the wake...     

Amphiphilic calixarenes: Probing monolayer stability by selective modification of the hydrophobic-hydrophilic balance

Abstract

The synthesis of calix[4]arenes permuting 1 or 4 C12 acyl chains at the upper rim and 1 or 4 methylene ethyl ester groups at the lower rim is described. The Langmuir compression isotherms of the compounds show that in the case of 1 acyl + 1 ester, there is probably orientation parallel to the air-water interface. For the other systems, orientation is orthogonal to the interface, and for the 4 +4 compound a pseudo collapse with reorientation of the hydrophilic ester groups is observed.     

A New Class of Fully Discrete Sparse Fourier Transforms: Faster Stable Implementations with Guarantees

Journal of Fourier Analysis and Applications - In this paper we consider sparse Fourier transform (SFT) algorithms for approximately computing the best s-term approximation of the discrete Fourier...     

Low thrombogenicity coating of nonwoven PET fiber structures for vascular grafts

Vascular PET grafts (Dacron) have shown good performance in large vessels (≥6 mm) applications. To address the urgent unmet need for small‐diameter (2–6 mm) vascular grafts, proprietary high‐compliance nonwoven PET fiber structures were modified with various PEG concentrations using PVA as a cross‐linking agent, to fabricate non‐thrombogenic mechanically compliant vascular grafts. The blood compatibility assays measured through platelet adhesion (SEM and mepacrine dye) and platelet activation (morphological changes, P‐selectin secretion, and TXB2 production) demonstrate that functionalization using a 10% PEG solution was sufficient to significantly reduce platelet adhesion/activation close to optimal literature‐reported levels observed on carbon‐coated ePTFE.

     

Synthesis of platinum complexes of fluorenyl-substituted porphyrins used as phosphorescent dyes for solution-processed organic light-emitting devices

Platinum(II) complexes of symmetrical meso-substituted A₄-porphyrins bearing four fluorene donor moieties 5,10,15,20-tetra(4-(2 methyloxyfluorenyl)phenyl)porphyrin, referred to as TOFP, or eight fluorene arms, 5,10,15,20-octa(3,5-(2 methyloxyfluorenyl)phenyl)porphyrin, OOFP, were synthesised and characterised. The photophysical properties of the new compounds are reported and compared to those of PtTPP and PtTFP {TPP=tetraphenylporphyrin and TFP=tetra(2-fluorenyl)porphyrin}. The luminescence quantum yields of PtTOFP and PtOOFP are 11% and 4.2%, respectively, compared to 4.6% for the reference PtTPP and only 2.0% for the previously studied compound PtTFP. The electronic and optoelectronic behaviour of solution-processed organic light-emitting devices (OLEDs) are reported that incorporate these platinum porphyrins as phosphorescent dyes doped into different layers of a polyvinylcarbazole (PVK) host.     

Nanocoatings onto arteries via layer-by-layer deposition: toward the in vivo repair of damaged blood vessels

The deposition of polysaccharide-based self-assembled nanocoatings onto damaged arteries is described as a means not only to protect a damaged artery against thrombogenesis, but also to control the healing processes by incorporating biologically active components within the multilayer. As shown by confocal microscopy, the polysaccharide multilayer was retained on the artery in physiological condition and prevented platelet adhesion. Diffusion of the polysaccharides within the artery was also observed and may be used to efficiently target the vascular wall. The NO-precursor l-arginine was used a drug model and incorporated within the self-assembled layers.     

Quantifying blood platelet morphological changes by dissipation factor monitoring in multilayer shells

The ability of electrostatically driven layer-by-layer (LbL) assembly to adapt to the morphological features of a template was explored. Subtle cytoskeletal changes in blood platelets became traceable through energy dissipation monitoring in multilayered shells using microgravimetric measurements. This LbL coating was sequentially deposited on protein-modified chips onto which platelets were adhered. In addition to consequently improving the signal sensitivity, the LbL shell acted in synergy with the cell, allowing the determination and quantification of cytoskeletal changes induced by the specific cell adhesion to the protein-modified chip surface used with a quartz crystal microbalance with dissipation. The difference in cell morphology, as a result of the optimization of specific interactions between the protein layer and cell membrane integrins induced viscoelastic changes in the polyelectrolyte shell, thereby providing quantitative data on platelet conformational changes upon their adhesion to protein-modified chip surface.     

Biomimetic hemocompatible coatings through immobilization of hyaluronan derivatives on metal surfaces

Biomimetic coatings offer exciting options to modulate the biocompatibility of biomaterials. The challenge is to create surfaces that undergo specific interactions with cells without promoting nonspecific fouling. This work reports an innovative approach toward biomimetic surfaces based on the covalent immobilization of a carboxylate terminated PEGylated hyaluronan (HA-PEG) onto plasma functionalized NiTi alloy surfaces. The metal substrates were aminated via two different plasma functionalization processes. Hyaluronan, a natural glycosaminoglycan and the major constituent of the extracellular matrix, was grafted to the substrates by reaction of the surface amines with the carboxylic acid terminated PEG spacer using carbodiimide chemistry. The surface modification was monitored at each step by X-ray photoelectron spectroscopy (XPS). HA-immobilized surfaces displayed increased hydrophilicity and reduced fouling, compared to bare surfaces, when exposed to human platelets (PLT) in an in vitro assay with radiolabeled platelets (204.1 +/- 123.8 x 10 (3) PLT/cm (2) vs 538.5 +/- 100.5 x 10 (3) PLT/cm (2) for bare metal, p < 0.05). Using a robust plasma patterning technique, microstructured hyaluronan surfaces were successfully created as demonstrated by XPS chemical imaging. The bioactive surfaces described present unique features, which result from the synergy between the intrinsic biological properties of hyaluronan and the chemical composition and morphology of the polymer layer immobilized on a metal surface.