Search results for " PVA"
showing 10 items of 15 documents
GEL DOSIMETERS FOR RADIOTHERAPY APPLICATIONS: RESULTS OF A “RESEARCH PROJECT OF NATIONAL INTEREST” (PRIN)
2016
Introduction: Gel dosimeters for three-dimensional mapping of radiotherapy doses were introduced at Yale University in the mid-1980’s. Soon after, research and development in this field also started in Italy. Early work was done at the Istituto Superiore di Sanità and at the Universities of Pisa and Milan. Several institutes now collaborate on this topic with the goal of developing new formulations of hydrogel matrices with improved characteristics of stability, sensitivity and spatial resolution compared to those of earlier Fricke-gel and polymer-gel systems. Materials and methods: Contrary to earlier gels based on natural gelling agents, such as porcine skin gelatin and/or agarose, which …
Diffusion and sensitivity characteristics of a chemically cross-linked PVA-Fricke gel dosimeter
2016
Introduction: Current radiotherapy techniques implement treatment plans based on volumetric distributions of dose with complex shapes and sharp gradients. The agreement between these plans and the dose that is truly delivered is very challenging to verify. Thus, there is the need for a dosimetric system that is truly three dimensional, sensitive to radiation in each point and tissue equivalent. In this framework, great interest is encountered by radio-chromic gel dosimeters. In order to address the limitations of gels based on natural matrices, some investigators have proposed dosimeters based on poly vinyl alcohol (PVA) made by freezing-thawing cycles. Even though these gels have a low dif…
PVA-GTA Fricke gel dosimeters exposed to clinical photons beams: Nuclear Magnetic Resonance Relaxometry and Imaging
2016
Fricke Gel (FXGs) dosimetric system is based on the radiation induced oxidation of ferrous to ferric ions. The application of Fricke gels for ionizing radiation dosimetry is continuously increasing worldwide due to their many favorable properties. However, one of their shortcomings is that ferrous and ferric ions diffuse in the gel matrix. To maintain the spatial integrity of the dose distribution, Fricke gels must be undergoing measurement within a few hours of their irradiation, so that ferric ions remain close to their point of production. Thus, the spatial integrity of the dose distribution in the Fricke gel is maintained (Schreiner, 2015). The gel matrix also contributes to the oxidati…
Living on the edge: assessing the extinction risk of critically endangered Bonelli’s eagle in Italy
2012
Background: The population of Bonelli’s eagle (Aquila fasciata) has declined drastically throughout its European range due to habitat degradation and unnatural elevated mortality. There are less than 1500 breeding pairs accounted for in Europe, and the species is currently catalogued as Critically Endangered in Italy, where the 22 territories of Sicily, represent nearly 95% of the entire Italian population. However, despite national and European conservation concerns, the species currently lacks a specific conservation plan, and no previous attempts to estimate the risk of extinction have been made. Methodology/Principal Findings: We incorporated the most updated demographic information ava…
Effect of alkyl derivatization of gellan gum during the fabrication of electrospun membranes
2021
Electrospun nanofibers based on polysaccharides represent a consolidated approach in Tissue Engineering and Regenerative Medicine (TERM) and nanomedicine as a drug delivery system (DDS). In this work, two chemical derivatives of a low molecular weight gellan gum (96.7 kDa) with aliphatic pendant tails were processed by electrospinning technique into non-woven nanofibrous mats. In order to generate spinnable blends, it was necessary to associate poly vinyl alcohol (PVA). The relationships between the physicochemical properties and the processability via electrospinning technique of gellan gum alkyl derivatives (GG-C8 and GG-C12 having a degree of alkyl chain derivatization of 17 mol % and 1…
Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging
2017
Abstract This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which …
Poly(vinyl alcohol)/κ-Carrageenan-based hydrogels enriched with the adhesive mussel protein Pvfp5β as 3D cell culture scaffold for tissue engineering…
2021
Many marine organisms such as sandcastle worms, barnacles and mussels, produce natural adhesives to attach to wet surfaces in aqueous tidal environments. In mussels, the adhesion is possible through the secretion of a protein-based water-resistant glue, composed of a mixture of proteins called mussel adhesive proteins (MAPs) or mussel foot proteins (mfps), that allow anchoring to almost any kind of surface in wet conditions [1]. The proteins confined to adhesive plaques are mfp-2, -3, -4, -5, and -6. All these proteins contain an atypically high concentration of the catecholic amino acid 3,4- dihydroxy-l-phenylalanine (DOPA), obtained by the post-translational enzymatic hydroxylation of tyr…
k-Carrageenan and PVA blends as 3D printing bioinks for cartilage reconstruction scaffolding
2021
Miscele di k-carragenina e PVA come bio-inchiostri per stampa 3D di scaffold per la ricostruzione della cartilagine
2021
Introduzione La k-carragenina (kC) è un poligalattano solfato ottenuto da alghe rosse con un contenuto di estere-solfato dal 25 al 30% e una peso molecolare medio ben superiore a 100 kDa. È formato da unità alternate di D-galattosio e 3,6-anidro-galattosio (3,6-AG) unite da legami α-1,3 e β-1,4-glicosidici. [1] Il kC assomiglia ai glicosaminoglicani (GAG) che sono i costituenti centrali dei tessuti connettivi, può essere quindi studiato per produrre scaffold per l'ingegneria tissutale. Il kC è solubile in acqua a temperature superiori a 60 °C e può formare gel stabili raffreddandosi. Le reti di kC sono forti, fragili e l'assenza di porosità interconnesse può limitare la colonizzazione dell'…