https://www.um.edu.mt/library/oar/handle/123456789/907 2026-04-11T05:29:04Z https://www.um.edu.mt/library/oar/handle/123456789/143309 Title: Storage stability and antioxidant activity of astaxanthin and beta-carotene as affected by the architecture of O/W emulsions of milk proteins Authors: Habtegebriel, Haileeyesus; Tazart, Zakaria; Farrugia, Claude; Valdramidis, Vasilis Abstract: Astaxanthin and β-carotene are among the potential anti-oxidant carotenoids with strong health promoting features. However, their sensitivity to light, heat and mechanical forces limit their application in food processing and storage conditions. The design of food matrix system, such as emulsions, that could prevent them from exposure to environmental factors will be utmost importance to slow down their degradation. In this study, O/W emulsion systems containing sunflower oil were prepared by applying ultrasound treatment and using different stabilizers (i.e. whey protein isolate (WPI) and sodium caseinate; NaCAS), co-surfactants (pectin and lecithin) while their performance against physical and chemical stability were investigated. The WPI– lecithin system produced emulsion droplets with Average diameter in the range of 560–2900 nm with a zeta-potential in the range of (−31) – (−34) mV, whereas the NaCAS – lecithin systems produced emulsion droplets with average diameter in the range of 230–240 nm and zeta potential of (−44) – (−48) mV. These values have a direct effect on the physical stability and chemical stability of the carotenoids in the emulsions. Astaxanthin was found to be more sensitive than β-carotene to ultrasound processing conditions. The designed emulsion systems slowed down the degradation of the carotenoids and maintained their DPPH scavenging properties during storage with astaxanthin loaded emulsions exhibiting better DPPH activity than β-carotene loaded emulsions. 2024-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/140715 Title: N-unsubstituted dihydropyridines and pyridones via multicomponent synthesis under a bio-derived heterogeneous catalyst Authors: Bosica, Giovanna; Abdilla, Roderick Abstract: In our exploration of metal-free and cost-effective heterogeneous catalysts for MCRs, we identified a novel system: piperazine immobilized within an agar matrix, functioning as a recyclable and reusable catalyst. This system efficiently facilitates the synthesis of dihydropyridines (DHPs) via one-pot condensation of dimedone, aldehydes, ammonium acetate, and various active methylene compounds—specifically malononitrile, acetophenone, or Meldrum's acid. A broad range of products was obtained, underscoring the versatility of the methodology. Notably, our prior investigations demonstrated this catalyst's efficacy in synthesizing N-aryl-substituted DHPs, affirming its general applicability. Additionally, fluorescence and UV absorption studies, along with in-depth characterization using 2D NMR spectroscopy, were conducted to confirm the structure and peak assignments of the synthesized products. 2025-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/140251 Title: Naphthalimide–organometallic hybrids as multi-targeted anticancer and luminescent cellular imaging agents Authors: Magri, David C.; Johnson, Alex D. Abstract: 1,8-Naphthalimides with an organometallic moiety with anticancer and luminescence or photoactive properties are reviewed. Primarily highlighted are 1,8-naphthalimide complexes with iron, platinum, and ruthenium, while honourable mentions are given to iridium, rhenium and rhodium complexes. The cytotoxicity, mechanism of action and cell selectivity of the compounds are discussed alongside their photophysical properties for monitoring interactions with biomolecules, most notably DNA, by absorption, fluorescence and dichroism spectroscopy. The luminescence properties provide additional insight regarding the cellular uptake and location of the intelligent agents within both cancer and healthy cells. The versatility of this emerging hybrid class of molecules earmarks them as multi-functional therapeutic and cellular imaging agents. The review concludes with suggestions for designing more effective multi-targeting cytotoxic agents with improved biocompatibility and imaging in hopes of enhancing their clinical potential. 2025-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/138311 Title: On the behavior of auxetic inserts : a numerical analysis to derive design guidelines Authors: Di Brizzi, Diego; Graziosi, Serena; Bondin, William; Grima, Joseph N.; Airoldi, Alessandro Abstract: Auxetics are a class of materials and metamaterials with a negative Poisson’s ratio (ν) and have gained tremendous popularity over the last three decades. Many studies have focused on characterizing designs that allow obtaining a negative ν. However, some open issues remain concerning understanding the auxetic behavior in operational conditions. Studies have been centered on analyzing the response of specific auxetic topologies instead of treating auxeticity as a property to be analyzed in a well-defined structural context. This study aims to contribute to the investigation of auxetic materials with a structural application, focusing on maximizing performance. The field of application of auxetics for designing inserts was selected and a model of a nail-cavity system was created to determine the effects of different design choices on the system behavior by exploring relationships between selected parameters and the auxetic insert behavior. The exploration combines finite element modeling analyses with their surrogate models generated by supervised learning algorithms. This approach allows for exploring the system’s behavior in detail, thus demonstrating the potential effectiveness of auxetics when used for such applications. A list of design guidelines is elaborated to support the exploitation of auxetics in nail-cavity systems. 2024-01-01T00:00:00Z