Thermal stability of the immobilization process of horseradish peroxidase in electrospun polymeric nanofibers

The horseradish peroxidase enzyme (type VI 250 U mg^?1) was encapsulated in polymeric nanofibers using the electrospinning technique and successfully immobilized by the exposure to glutaraldehyde (GA) vapor in order to create covalent bonds between the polyivinilalcohol (PVA) polymeric chains and the enzyme molecules. The morphology of the nanofibers was analyzed by scanning electron microscopy (SEM) showing a diameter in the range of 100–200 nm. The presence of the enzyme in the electrospun nanofibers was confirmed by infrared spectroscopy (FTIR). The optimum crosslinking time was 1 h of exposure to GA vapor. The maximum percentage of the retained protein and the enzyme activity was obtained using the lowest initial enzyme concentration. The enzyme activity of the sample was retained after four reuse cycles. Differential scanning calorimetry (DSC) was used to study the thermal stability of the samples. The thermal study of the immobilized HRP enzyme provide for the first time additional information regarding the interaction of the HRP enzyme molecules with the PVA chains of the nanofiber matrix, as well as the effect of the crosslinking time in the glass transition temperature and the heat of fusion of the samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44811.     

Phytosterol Esterification is Markedly Decreased in Preterm Infants Receiving Routine Parenteral Nutrition

Several studies reported the association between total plasma phytosterol concentrations and the parenteral nutrition‐associated cholestasis (PNAC). To date, no data are available on phytosterol esterification in animals and in humans during parenteral nutrition (PN). We measured free and esterified sterols (cholesterol, campesterol, stigmasterol, and sitosterol) plasma concentrations during PN in 16 preterm infants (500–1249 g of birth weight; Preterm‐PN), in 11 term infants (Term‐PN) and in 12 adults (Adult‐PN). Gas chromatography–mass spectrometry was used for measurements. Plasma concentrations of free cholesterol (Free‐CHO), free phytosterols (Free‐PHY) and esterified phytosterols (Ester‐PHY) were not different among the three PN groups. Esterified cholesterol (Ester‐CHO) was statistically lower in Preterm‐PN than Adult‐PN. Preterm‐PN had significantly higher Free‐CHO/Ester‐CHO and Free‐PHY/Ester‐PHY ratios than Adult‐PN (Free‐CHO/Ester‐CHO: 1.1 ± 0.7 vs. 0.6 ± 0.2; Free‐PHY/Ester‐PHY: 4.1 ± 2.6 vs. 1.3 ± 0.8; *P < 0.05). Free‐CHO/Ester‐CHO and Free‐PHY/Ester‐PHY ratios of Term‐PN (Free‐CHO/Ester‐CHO: 1.1 ± 0.4; Free‐PHY/Ester‐PHY: 2.9 ± 1.7) were not different from either Preterm‐PN or from Adult‐PN. Plasma Free‐CHO/Ester‐CHO and Free‐PHY/Ester‐PHY were unchanged after 24 h on fat‐free PN both in Preterm‐PN and in Adult‐PN. Free‐PHY/Ester‐PHY did not correlate with phytosterol intake in Preterm‐PN. Free‐PHY/Ester‐PHY of Preterm‐PN was positively correlated with the Free‐CHO/Ester‐CHO and negatively correlated with gestational age and birth weight. In conclusion, PHY were esterified to a lesser extent than CHO in all study groups; the esterification was markedly decreased in Preterm‐PN compared to Adult‐PN. The clinical consequences of these findings warrant further investigations.     

Far-infrared laser measurement of the refractive index of polypropylene

The refractive index of polypropylene in the far infrared (FIR) is measured by means of a suitably modified laser of a FIR spectrometer. When thin polypropylene films of 12.7-microm nominal thickness are introduced in the optical cavity of a laser at the Brewster angle, the radiation ceases because of the change in the optical path of the laser beam. This change is measured from the displacement of one of the laser mirrors, which is necessary to restore the laser resonance. The refractive index of polypropylene is deduced from this measurement and from the film thickness, as obtained from an independent measurement based in pycnometry. The value obtained for the refractive index is 1.492(15) for the wavelengths between 118.834 and 251.140 microm, for a polypropylene film of 12.71(2)-microm thickness and 0.9049(7) g/cm3 density.     

A 3D Real‐Scale,Biomimetic, and Biohybrid Model of the Blood‐Brain Barrier Fabricated through Two‐Photon Lithography

The investigation of the crossing of exogenous substances through the blood‐brain barrier (BBB) is object of intensive research in biomedicine, and one of the main obstacles for reliable in vitro evaluations is represented by the difficulties at the base of developing realistic models of the barrier, which could resemble as most accurately as possible the in vivo environment. Here, for the first time, a 1:1 scale, biomimetic, and biohybrid BBB model is proposed. Microtubes inspired to the brain capillaries were fabricated through two‐photon lithography and used as scaffolds for the co‐culturing of endothelial‐like bEnd.3 and U87 glioblastoma cells. The constructs show the maturation of tight junctions, good performances in terms of hindering dextran diffusion through the barrier, and a satisfactory trans‐endothelial electrical resistance. Moreover, a mathematical model is developed, which assists in both the design of the 3D microfluidic chip and its characterization. Overall, these results show the effective formation of a bioinspired cellular barrier based on microtubes reproducing brain microcapillaries to scale. This system will be exploited as a realistic in vitro model for the investigation of BBB crossing of nanomaterials and drugs, envisaging therapeutic and diagnostic applications for several brain pathologies, including brain cancer.     

Arteriovenous fistula: end‐to‐end or end‐to side anastomosis?

The purpose of the present study was to compare the end‐to‐end (ETEa) with the end‐to‐side (ETSa) anastomosis in patients starting hemodialysis by means of radio‐cephalic artero‐venous fistulae (AVF). In our experience, we compared the results, as early failure (EF), late thrombosis (LT), stenosis, steal syndrome, and primary patency (PP), in 2 groups of hemodialysis incident patients that had been placed an AVF by means of ETEa or ETSa. The observation period lasted 24 months for each of the 2 types of AVF, starting from October 2005 to September 2007 for ETEa and from October 2007 to September 2009 for ETSa. One hundred forty patients were included in the present study. We have consecutively performed 99 AVF interventions at the wrist or at the third distal of the forearm, in 70 patients by means of ETEa and 82 AVF interventions in the same anatomical places in 70 patients by means of ETSa. The patients with ETEa had a mean age of 64.4 ± 14.6 years, males were 65.8% and the age dialysis at the end of observation was 10.4 ± 5.7 months. Those with ETSa had a mean age of 65.9 ± 15.5 years and the males were 62.9%, the age dialysis at the end of observation was 9.2 ± 5.5 months. The surgical team was composed by the same nephrologists. The statistical study was performed by means of the χ chi‐square and Fisher's exact test. We have observed more late thrombosis (10% vs. 4.1%) and stenosis (21.4% vs. 2.7%) in ETEa than in ETSa. The number of early thrombosis was similar in the 2 types of anastomosis. The primary patency 1‐year rate was better though not significantly in the ETS (80% vs. 85.7%) In our experience the ETSa provides, overall better results, both regarding the complications and primary survival than ETEa. For the benefits that seem to come from it, we believe, that a broad ETSa in the distal native AVF is preferable to the ETEa.     

Novel inhibitors of alpha 4 beta 1 integrin receptor interactions through library synthesis and screening

A library of 2302 small molecule beta-turn mimetics was screened for inhibition of the alpha 4 beta 1 integrin-CS1 splice variant binding interaction. Preliminary data revealed several active ligands, and validation with purified material culminated in the identification of some of the first small molecule ligands (1, IC50 = 5 microM, and 2, IC50 = 8 microM) to be reported for this class of integrins.     

Composition and functional analysis of the Saccharomyces cerevisiae trehalose synthase complex

In the yeast Saccharomyces cerevisiae, trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP), which convert glucose 6-phosphate plus UDP-glucose to trehalose, are part of the trehalose synthase complex. In addition to the TPS1 (previously also called GGS1, CIF1, BYP1, FDP1, GLC6, and TSS1) and TPS2 (also described as HOG2 and PFK3) gene products, this complex also contains a regulatory subunit encoded by TSL1. We have constructed a set of isogenic strains carrying all possible combinations of deletions of these three genes and of TPS3, a homologue of TSL1 identified by systematic sequencing. Deletion of TPS1 totally abolished TPS activity and measurable trehalose, whereas deletion of any of the other genes in most cases reduced both. Similarly, deletion of TPS2 completely abolished TPP activity, and deletion of any of the other genes resulted in a reduction of this activity. Therefore, it appears that all subunits are required for optimal enzymatic activity. Since we observed measurable trehalose in strains lacking all but the TPS1 gene, some phosphatase activity in addition to Tps2 can hydrolyze trehalose 6-phosphate. Deletion of TPS3, in particular in a tsl1Delta background, reduced both TPS and TPP activities and trehalose content. Deletion of TPS2, TSL1, or TPS3 and, in particular, of TSL1 plus TPS3 destabilized the trehalose synthase complex. We conclude that Tps3 is a fourth subunit of the complex with functions partially redundant to those of Tsl1. Among the four genes studied, TPS1 is necessary and sufficient for growth on glucose and fructose. Even when overproduced, none of the other subunits could take over this function of Tps1 despite the homology shared by all four proteins. A portion of Tps1 appears to occur in a form not bound by the complex. Whereas TPS activity in the complex is inhibited by Pi, Pi stimulates the monomeric form of Tps1. We discuss the possible role of differentially regulated Tps1 in a complex-bound or monomeric form in light of the requirement of Tps1 for trehalose production and for growth on glucose and fructose.     

An algorithm for the structural analysis of state space: synthesis of nonlinear observers

The problem addressed is the linearization of multi‐input multi‐output (MIMO) nonlinear systems by a generalized state coordinates transformation and generalized input–output injection, in order to design an observer. This observer will have linear error dynamics. The goal is to bring together two observers design approaches: a structural one and a numerical one. Necessary and sufficient conditions for the existence of a linearizing generalized state transformation are obtained by an algebraic way and without computing the input–output differential equations. The main result tests integrability conditions of differential one‐forms derived from the state space representation and is applicable to a large subclass of nonlinear systems. Copyright © 2001 John Wiley & Sons, Ltd.     

Load Testing of a Closed-Ended Pipe Pile Driven in Multilayered Soil

Piles are often driven in multilayered soil profiles. The accurate prediction of the ultimate bearing capacity of piles driven in mixed soil is more challenging than that of piles driven in either clay or sand because the mechanical behavior of these soils is better known. In order to study the behavior of closed-ended pipe piles driven into multilayered soil profiles, fully instrumented static and dynamic axial load tests were performed on three piles. One of these piles was tested dynamically and statically. A second pile served as reaction pile in the static load test and was tested dynamically. A third pile was tested dynamically. The base of each pile was embedded slightly in a very dense nonplastic silt layer overlying a clay layer. In this paper, results of these pile load tests are presented, and the lessons learned from the interpretation of the test data are discussed. A comparison is made of the ultimate base and limit shaft resistances measured in the pile load tests with corresponding values predicted from in situ test-based and soil property-based design methods.