Antibacterial modification of nylon-6 nanofibers: structure,properties and antibacterial activity.

Antibacterial nylon 6 (PA6) nanofibers have been prepared in one-step procedure using Nanospider technology. Chlorhexidine (CHX), 1-dodecyltrimethylamonium bromide (DTAB) and benzyltrimethylamonium bromide (BTAB) have been used as antibacterial agents. Samples were characterized by a series of analytical and testing methods to investigate the surface chemistry, zeta potential, structure, morphology, phase composition, mechanical properties and antibacterial activity. Experimental characterization has been combined with molecular modeling to analyze the interaction of nanofibers with modifying molecules for better understanding the effect of nanofibers modification on their properties. Antibacterial modification of PA6 led to significant changes of zeta potential (from -31 mV for PA 6 up to -49 mV for PA6/BTAB), changes in phase composition (decrease of alpha phase content and increase of gamma phase content for PA6/BTAB and PA6/CHX) and to significant increase of fiber diameter for PA6/BTAB. Antibacterial modification resulted in the straightening of nanofibers and to higher permeability of nanofiber textile for all investigated samples. Tensile tests showed the the increase of Young modulus for all the investigated samples. All the modified samples: PA6/DTAB, PA6/BTAB and PA6/CHX exhibit good antibacterial activity.     

Design and Synthesis of Galactosylated Bifurcated Ligands with Nanomolar Affinity for Lectin LecA from Pseudomonas aeruginosa

Lectin A (LecA) from Pseudomonas aeruginosa is an established virulence factor. Glycoclusters that target LecA and are able to compete with human glycoconjugates present on epithelial cells are promising candidates to treat P. aeruginosa infection. A family of 32 glycodendrimers of generation 0 and 1 based on a bifurcated bis‐galactoside motif have been designed to interact with LecA. The influences both of the central multivalent core and of the aglycon of these glycodendrimers on their affinity toward LecA have been evaluated by use of a microarray technique, both qualitatively for rapid screening of the binding properties and also quantitatively (K_d). This has led to high‐affinity LecA ligands with K_d values in the low nanomolar range (K_d=22 nm for the best one).     

A study of the properties of compacts from silicified microcrystalline celluloses

The paper deals with a study of tensile strength and disintegration time of compacts made from silicified microcrystalline celluloses, Prosolv SMCC 90, and Prosolv HD 90, in dependence on compression force, addition of two types of lubricants, and two active ingredients. The lubricants were magnesium stearate and sodium stearyl fumarate in a concentration of 0.5%, the active ingredients being ascorbic acid and acetylsalicylic acid in a concentration of 50%.

Prosolv SMCC 90 proved to be better compatible than Prosolv HD 90; the compacts were of higher strength, which was markedly increased with increasing compression force. Prosolv HD 90 was more sensitive to additions of lubricants, and a greater decrease in strength was recorded due to the influence of sodium stearyl fumarate. The effect of lubricants on the strength of compacts in the presence of active ingredients was not identical. The disintegration time of compacts from Prosolv HD 90 without as well as with lubricants was shorter than from Prosolv SMCC 90 and was increasing with increasing compression force. Disintegration time was increased with added lubricants, and it was markedly shortened by addition of active ingredients. Compacts containing ascorbic acid possessed a shorter disintegration time than those containing acetylsalicylic acid, and it was not markedly influenced by the presence of lubricants.     

Hydrogel–elastomer composite biomaterials: 1. Preparation of interpenetrating polymer networks and in vitro characterization of swelling stability and mechanical properties

We prepared interpenetrating polymer networks (IPNs) composed of a gelatin hydrogel and a HydroThane^TM elastomer to combine the advantages of both polymers into one biomaterial. Fourier transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC) confirmed the co-existence of the two polymers in the IPNs. Optical light microscopy confirmed hydrogel domains were interspaced into an elastomer network. Hydration and stability studies in aqueous solution showed that, although the IPN biomaterials exhibited stable swelling for more than 30 days, approximately 10% and 50% loss of the hydrogel component were confirmed at room temperature and 37 °C, respectively, using gel permeation chromatography (GPC). The swelling study in the serum-containing medium indicated the biomaterials maintained their swelling stability for different periods, depending on the extent of gelatin methacrylation, photoinitiator concentration and incubation temperature. Lastly, the biomaterials exhibited higher failure stress and lower failure strain in a dry state than in a swollen state, and showed limited changes in both stress and strain at room temperature and at 37 °C, in contrast with a decrease at 50 °C. No significant effects of gelatin methacrylation on mechanical properties were noticed. The preparation and characterization methods were well established and formed the basis of further developing the biomaterials.     

Plant Chemical Defense Induced by a Seed-Eating Pollinator Mutualist

Plant-seed parasite pollination mutualisms involve a specific pollinator whose larvae develop by consuming a fraction of the host plant seeds. These mutualisms are stable only if the plant can control seed destruction by the larvae. Here, we studied the chemical response of the European globeflower Trollius europaeus to infestation by an increasing number of Chiastocheta fly larvae. We used liquid chromatographic analysis to compare the content of phenolic compounds in unparasitized and parasitized fruits collected in two natural populations of the French Alps, and mass spectrometry and nuclear magnetic resonance to elucidate the structure of adonivernith, a C-glycosyl-flavone. This compound is present in many of the organs of T. europaeus, but not found in other Trollius species. Furthermore, it is overproduced in the carpel walls of parasitized fruits, and this induced response to infestation by fly larvae is density-dependent (increases with larval number), and site-dependent (more pronounced in the high-altitude site). Mechanical damage did not induce adonivernith production. This tissue-specific and density-dependent response of T. europaeus to infestation by Chiastocheta larvae might be an efficient regulation mechanism of seed-predator mutualist population growth if it decreases survival or growth of the larvae.     

Bleeding and Thrombosis: Insights into Pathophysiology of Bothrops Venom-Related Hemostasis Disorders

Toxins from Bothrops venoms targeting hemostasis are responsible for a broad range of clinical and biological syndromes including local and systemic bleeding, incoagulability, thrombotic microangiopathy and macrothrombosis. Beyond hemostais disorders, toxins are also involved in the pathogenesis of edema and in most complications such as hypovolemia, cardiovascular collapse, acute kidney injury, myonecrosis, compartmental syndrome and superinfection. These toxins can be classified as enzymatic proteins (snake venom metalloproteinases, snake venom serine proteases, phospholipases A₂ and L-amino acid oxidases) and non-enzymatic proteins (desintegrins and C-type lectin proteins). Bleeding is due to a multifocal toxicity targeting vessels, platelets and coagulation factors. Vessel damage due to the degradation of basement membrane and the subsequent disruption of endothelial cell integrity under hydrostatic pressure and tangential shear stress is primarily responsible for bleeding. Hemorrhage is promoted by thrombocytopenia, platelet hypoaggregation, consumption coagulopathy and fibrin(ogen)olysis. Onset of thrombotic microangiopathy is probably due to the switch of endothelium to a prothrombotic phenotype with overexpression of tissue factor and other pro-aggregating biomarkers in association with activation of platelets and coagulation. Thrombosis involving large-caliber vessels in B. lanceolatus envenomation remains a unique entity, which exact pathophysiology remains poorly understood.     

Failure of Diphtheria Toxin Model to Induce Parkinson-Like Behavior in Mice

Rodent models of Parkinson’s disease are based on transgenic expression of mutant synuclein, deletion of PD genes, injections of MPTP or rotenone, or seeding of synuclein fibrils. The models show histopathologic features of PD such as Lewi bodies but mostly only subtle in vivo manifestations or systemic toxicity. The models only partly mimic a predominant loss of dopaminergic neurons in the substantia nigra. We therefore generated mice that express the transgenic diphtheria toxin receptor (DTR) specifically in DA neurons by crossing DAT-Cre mice with Rosa26 loxP-STOP-loxP DTR mice. After defining a well-tolerated DTx dose, DAT-DTR and DTR-flfl controls were subjected to non-toxic DTx treatment (5 × 100 pg/g) and subsequent histology and behavioral tests. DAT protein levels were reduced in the midbrain, and tyrosine hydroxylase-positive neurons were reduced in the substantia nigra, whereas the pan-neuronal marker NeuN was not affected. Despite the promising histologic results, there was no difference in motor function tests or open field behavior. These are tests in which double mutant Pink1^−/−SNCA^A53T Parkinson mice show behavioral abnormalities. Higher doses of DTx were toxic in both groups. The data suggest that DTx treatment in mice with Cre/loxP-driven DAT-DTR expression leads to partial ablation of DA-neurons but without PD-reminiscent behavioral correlates.     

Method for numerical integration of rapidly oscillating functions in diffraction theory

The quadrature of general, highly oscillatory integrals is a relatively complicated computational problem that occurs in a wide range of practical applications, e.g. in physics, chemistry, and image analysis. It is often necessary to use a high number of nodal points with classical quadrature formulas in order to achieve a required accuracy of numerical integration of rapidly oscillating functions. However, an increase in integration points leads to a larger computational time. Our work describes and analyses a method for numerical integration of rapidly oscillating functions, which enables to obtain the required accuracy with a smaller number of nodal points than classical integration rules and with a relatively simple integration formula. The proposed method is generally suitable for integration of rapidly oscillating functions in various applications. The method is demonstrated in examples of calculation of the diffraction integral in optics, where the integrand is often a rapidly oscillatory function. The results can be readily adapted to similar problems from other fields. Copyright © 2009 John Wiley & Sons, Ltd.