Effect of oxygen contamination on densification of Fe(Se,Te)

Abstract The optimization of sintering behaviour of iron chalcogenides superconducting materials is mandatory to enhance their critical current density, in order to pursuit their application in the production of superconducting wires. In this context it has been investigated here the effect of oxygen contamination on the material densification, considering the issues related to industrial oxygen-free isolated production lines. Our results show that the densification process is negatively affected by oxygen contamination. However, despite the difference in density, all sintered samples are characterized by similar structural and morphological features, and show comparable electrical and magnetic properties, with low critical current densities (Jc<103 A/cm2). These results suggest that densification is not the key limiting factor in these conditions, and that grain boundary or misorientation factors may play a greater role in limiting the performance of sintered iron chalcogenides superconductors

Nanostructured biocompatible systems for target drug delivery

In this research, we have developed surfactant-assisted methods to produce polymeric, ceramic and composite nanoparticles. We have shown that, depending on water/oil/surfactant composition and the homogenization system, the particle size is greatly affected. Polymeric particles prepared by cross-linking of the albumin (BSA) or polyallylamine (PALA) with glutaraldehyde have considerable interest for their use as a delivery vehicle for various pharmaceutical agents and as models to develop innovative nanocomposites. MnFe2O4 magnetic nanoparticles have been synthesized by using reverse-micelles as nanoreactors. The coprecipitation of Mn2+ and Fe3+ ions in alkaline solution produced a hydroxide precursor which is been transformed in manganese ferrite by calcination. The superparamagnetic behaviour of sample calcined at 600°C certainly demonstrated that obtained MnFe2O4 is a nanocrystalline system and that each crystallite exists as a single magnetic domain. The magnetic nanoparticles were entrapped in albumin cross-linked with glutaraldehyde. The composite nanoparticles consist of superparamagnetic nanoparticles distributed in a polymeric network that provides functional groups for further derivatization. In order to demonstrate drug loading and release efficacy of the developed carriers, a model drug was entrapped or adsorbed on the materials. Results from antibiotic entrapment evidenced that the antibiotic delivery is restricted by the limited ability of the drug to diffuse out of particle. Adsorbed drug is resulted active against Gram-positive bacteria (S. epidermidis) for ~8 days when adsorbed on the polymeric nanoparticles and for ~ 2 days in the composite nanoparticles case. The interaction of produced materials with cells was studied using an in vitro assay. The materials did not affect the cell morphology. Nevertheless, the materials can not easily characterized in vitro for their expected in vivo behaviour since it must be said that the in vitro characterization of biomaterials is not sufficient to predict their real in vivo behaviour and their biocompatibility. It is well known that several physico-chemical and biological factors can affect their interactions with the body elements, and that they must be evaluated under specific physiological and pathologic conditions

Antimicrobial polyurethanes containing an association of antibiotics

In this work, surface minimizing the risk of device-associated infections, through antibiotic adsorption on suitably modified biocompatible polymeric materials were developed. To improve the resistance of the device to microbial infections, a combination of two antibiotics, cefamandole nafate (CEF) and a rifampin (RIF), having different action mechanisms, were adsorbed on functionalized polyurethane films. Antibiotic release increased by adding, as pore formers, polyethylenglycol (PEG) of a different molecular weight

Rilascio di una combinazione di antibiotici da matrici poliuretaniche per prevenire la formazione di biofilm microbici e contrastare l’insorgenza di antibiotico-resistenza.

Una combinazione di antibiotici è stata adsorbita su matrici poliuretaniche per contrastare la formazione di biofilm microbici che sono gli agenti causanti le infezioni correlate a dispositivi medici. Lo scopo del lavoro è stato quello di studiare la cinetica di rilascio dei farmaci come pure di valutare l'attività antibatterica nel tempo del sistema sviluppato. Gli antibiotici scelti per l'adsorbimento possedevano meccanismi di azione diversi al fine di controllare lo sviluppo dell'insorgenza di microrganismi antibiotico-resistenti

Lipase Immobilization on Differently Functionalized Vinyl-Based Amphiphilic Polymers: Influence of Phase Segregation on the Enzyme Hydrolytic Activity

Microbial lipase from Candida rugosa was immobilized by physical adsorption onto an ethylene vinyl alcohol polymer (EVAL) functionalized with acyl chlorides. To evaluate the influence of the reagent chain-length on the amount and activity of immobilized lipase, three differently long aliphatic fatty acids were employed (C8, C12, C18), obtaining EVAL functionalization degrees ranging from 5% to 65%. The enzyme polymer affinity increased with both the length of the alkyl chain and the matrix hydrophobicity. In particular, the esterified polymers showed a tendency to give segregated hydrophilic and hydrophobic domains. It was observed the formation of an enzyme multilayer at both low and high protein concentrations. Desorption experiments showed that Candida rugosa lipase may be adsorbed in a closed form on the polymer hydrophilic domains and in an open, active structure on the hydrophobic ones. The best results were found for the EVAL-C18 13% matrix that showed hyperactivation with both the soluble and unsoluble substrate after enzyme desorption. In addition, this supported biocatalyst retained its activity for repetitive cycles

Chemical functionalization of vinyl polymers to obtain heparin-like materials

Vinyl polymers were chemically modified by introduction of carboxylic and sulfonate groups to obtain heparin-like materials with improved haemocompatibility. The functionalised polymers were physico-chemical characterised and preliminary biological tests proved the more importance of strongly acidic groups on the materials anticoagulant properties

Biomateriali a rilascio di agenti antimicrobici per lo sviluppo di dispositivi medici anti-biofilm.

I notevoli progressi in campo medico concretizzati negli ultimi decenni sono in parte da attribuire al crescente sviluppo di nuovi materiali sintetici, idonei per la realizzazione di dispositivi medici impiantabili. Al loro impiego è, tuttavia, associata una grave complicanza clinica: l’instaurarsi di processi infettivi. Tra le diverse specie microbiche responsabili, le più comuni sono batteri gram positivi (stafilococchi), e lieviti (candide). Al fine di sviluppare biomateriali polimerici capaci di inibire la colonizzazione da specie microbica e la conseguente formazione di biofilm sono state messe appunto diverse strategie. L’adsorbimento sulle matrici polimeriche di una o più specie antimicrobiche (cefamandole nafate, rifampicina, amoxicillina e vancomicina) o di specie antifungine (fluconazolo) è stato uno degli approcci di maggior successo, da noi perseguiti. Metodo alternativo è stato, invece, la modifica superficiale della matrice polimerica stessa, mediante salificazione di gruppi funzionali specifici con metalli pesanti dalle note proprietà antibatteriche, come l’Ag. Il successivo adsorbimento sulla matrice così modificata, dell’antibiotico ciprofloxacina, ha permesso di ottenere un biomateriale antibiofilm la cui attività non è limitata dal potenziale sviluppo di antibiotico resistenza