Heterogeneous design and mechanical analysis of HELIAS 5-B helium-cooled pebble bed breeding blanket concept

One of the most challenging objectives of the European research concerning nuclear fusion technology, promoted by the EUROfusion consortium, is to bring stellarator-type nuclear fusion devices to maturity. To this purpose, studies on a large HELIcal-axis advanced stellarator (HELIAS), extrapolated from Wendelstein 7-X and based on a 5-fold symmetry (HELIAS 5-B), are currently ongoing. The HELIAS 5-B stellarator reactor will be endowed with a breeding blanket (BB) system to allow for the self-sustainability of the nuclear fusion reaction and make it suitable for electricity generation. In this paper, we present the first ever heterogeneous mechanical design and the preliminary structural assessment of a bean-shaped ring of a HELIAS 5-B BB sector. The proposed mechanical design, which is based on the helium-cooled pebble bed (HCPB) BB concept and developed according to the “sandwich” architecture, foresees an actively cooled segment box connected to a back-supporting structure equipped with manifolds. The internal region (breeding zone) is reinforced by actively cooled steel plates. The proposed heterogeneous design was checked against nominal loads and an in-box loss of coolant accidental scenario, which is a typical design driver for BBs. The assessment has been performed according to the RCC-MRx structural design code. Our results are herewith presented and critically discussed, focusing on the potential follow-up of the HELIAS 5-B HCPB BB design

Inulin-Based Polymeric Micelles Functionalized with Ocular Permeation Enhancers: Improvement of Dexamethasone Permeation/Penetration through Bovine Corneas

Ophthalmic drug delivery is still a challenge due to the protective barriers of the eye. A common strategy to promote drug absorption is the use of ocular permeation enhancers, while an innovative approach is the use of polymeric micelles. In the present work, the two mentioned approaches were coupled by conjugating ocular permeation enhancers (PEG2000, carnitine, creatine, taurine) to an inulin-based co-polymer (INU-EDA-RA) in order to obtain self-assembling biopolymers with permeation enhancer properties for the hydrophobic drug dexamethasone (DEX). Inulin derivatives were properly synthetized, were found to expose about 2% mol/mol of enhancer molecules in the side chain, and resulted able to self-assemble at various concentrations by varying the pH and the ionic strength of the medium. Moreover, the ability of polymeric micelles to load dexamethasone was demonstrated, and size, mucoadhesiveness, and cytocompatibility against HCE cells were evaluated. Furthermore, the efficacy of the permeation enhancer was evaluated by ex vivo permeation studies to determine the performance of the used enhancers, which resulted in PEG2000 > CAR > TAU > CRE, while entrapment ability studies resulted in CAR > TAU > PEG2000 > CRE, both for fluorescent-labelled and DEX-loaded micelles. Finally, an increase in terms of calculated Kp and Ac parameters was demonstrated, compared with the values calculated for DEX suspension

HYALURONIC ACID DERIVATIVE MICELLES AS OCULAR PLATFORMS TO DRUG RELEASE AND CORNEAL PERMEATION

In traditional ocular formulations, only small amount of the administered drug penetrates the cornea to reach the intraocular tissue. One approach to improve the drug ocular bioavailability was to develop colloidal drug delivery systems. Polymeric micelles seem to be very promising for their capacity to dissolve a variety of hydrophobic drugs by enhancing their water solubility and so their bioavailability. They are able to increase ocular drug permeability due to interact with the complex corneal structure. Considering the advantages to use mucoadhesive polymer to increase drug residence time on the ocular surface, the aim of this work was to prepare hyaluronic acid-based micelles as a platform to release corticosteroids on the ocular surface. Three amphiphilic derivatives of hyaluronic acid (HA), bearing different amount of hexadecylamine chains (C16), were synthesised and characterized. These are able to form micelles by using the co-solvent evaporation method. All HAC16 derivatives have shown the ability of durable mucoadhesive interactions and resulted potentially useful for corticosteroids encapsulation. Drug-loaded micelles were prepared and characterized in term of drug loading amount and particle size. Moreover, the in vitro drug release studies from micellar systems were carried out in comparison with the dissolution profile of the free drug suspension. Cytocompatibility studies also were performed with HCEpiC cells. HAC16b (DDC16mol%=12%) micelles are selected as the best nanosystems, and their capacity to improve the drugs permeability across corneal barrier are evaluated. Thus, the ex vivo permeation studies were conducted using bovine corneas and Franz type diffusion cells

Modulation of physical and biological properties of a composite PLLA and polyaspartamide derivative obtained via thermally induced phase separation (TIPS) technique

In the present study, blend of poly l-lactic acid (PLLA) with a graft copolymer based on α,β-poly(N-hydroxyethyl)-dl-aspartamide and PLA named PHEA-PLA, has been used to design porous scaffold by using Thermally Induced Phase Separation (TIPS) technique. Starting from a homogeneous ternary solution of polymers, dioxane and deionised water, PLLA/PHEA-PLA porous foams have been produced by varying the polymers concentration and de-mixing temperature in metastable region. Results have shown that scaffolds prepared with a polymer concentration of 4% and de-mixing temperature of 22.5 °C are the best among those assessed, due to their optimal pore size and interconnection. SEM and DSC analysis have been carried out respectively to study scaffold morphology and the influence of PHEA-PLA on PLLA crystallization, while DMF extraction has been carried out in order to quantify PHEA-PLA into the final scaffolds. To evaluate scaffold biodegradability, a hydrolysis study has been performed until 56 days by incubating systems in a media mimicking physiological environment (pH 7.4). Results obtained have highlighted a progressive increase in weight loss with time in PLLA/PHEA-PLA scaffolds, conceivably due to the presence of PHEA-PLA and polymers interpenetration. Viability and adhesion of bovine chondrocytes seeded on the scaffolds have been studied by MTS test and SEM analysis. From results achieved it appears that the presence of PHEA-PLA increases cells affinity, allowing a faster adhesion and proliferation inside the scaffold

Heterogeneous design and mechanical analysis of HELIAS 5‐B helium‐cooled pebble bed breeding blanket concept

One of the most challenging objectives of the European research concerning nuclear fusion technology, promoted by the EUROfusion consortium, is to bring stellarator-type nuclear fusion devices to maturity. To this purpose, studies on a large HELIcal-axis advanced stellarator (HELIAS), extrapolated from Wendelstein 7-X and based on a 5-fold symmetry (HELIAS 5-B), are currently ongoing. The HELIAS 5-B stellarator reactor will be endowed with a breeding blanket (BB) system to allow for the self-sustainability of the nuclear fusion reaction and make it suitable for electricity generation. In this paper, we present the first ever heterogeneous mechanical design and the preliminary structural assessment of a bean-shaped ring of a HELIAS 5-B BB sector. The proposed mechanical design, which is based on the helium-cooled pebble bed (HCPB) BB concept and developed according to the “sandwich” architecture, foresees an actively cooled segment box connected to a back-supporting structure equipped with manifolds. The internal region (breeding zone) is reinforced by actively cooled steel plates. The proposed heterogeneous design was checked against nominal loads and an in-box loss of coolant accidental scenario, which is a typical design driver for BBs. The assessment has been performed according to the RCC-MRx structural design code. Our results are herewith presented and critically discussed, focusing on the potential follow-up of the HELIAS 5-B HCPB BB design