Institute of Nanostructures, Nanomodelling and Nanofabrication

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Publications

Novel Hydrogel Membranes Based on the Bacterial Polysaccharide FucoPol: Design, Characterization and Biological Properties

Publication . Araújo, Diana; Martins, Matilde; Concórdio-Reis, Patrícia; Roma-Rodrigues, Catarina; Morais, Maria; Delgado Alves, Vitor; Fernandes, Alexandra; Freitas, Filomena

FucoPol, a fucose-rich polyanionic polysaccharide, was used for the first time for the preparation of hydrogel membranes (HMs) using Fe3+ as a crosslinking agent. This study evaluated the impact of Fe3+ and FucoPol concentrations on the HMs’ strength. The results show that, above 1.5 g/L, Fe3+ concentration had a limited influence on the HMs’ strength, and varying the FucoPol concentration had a more significant effect. Three different FucoPol concentrations (1.0, 1.75 and 2.5 wt.%) were combined with Fe3+ (1.5 g/L), resulting in HMs with a water content above 97 wt.% and an Fe3+ content up to 0.16 wt.%. HMs with lower FucoPol content exhibited a denser porous microstructure as the polymer concentration increased. Moreover, the low polymer content HM presented the highest swelling ratio (22.3 1.8 g/g) and a lower hardness value (32.4 5.8 kPa). However, improved mechanical properties (221.9 10.2 kPa) along with a decrease in the swelling ratio (11.9 1.6 g/g) were obtained for HMs with a higher polymer content. Furthermore, all HMs were non-cytotoxic and revealed anti-inflammatory activity. The incorporation of FucoPol as a structuring agent and bioactive ingredient in the development of HMs opens up new possibilities for its use in tissue engineering, drug delivery and wound care management.

2023-07Journal article

Open access

Impact of indigenous non-Saccharomyces yeasts isolated from Madeira Island vineyards on the formation of ethyl carbamate in the aging of fortified wines

Publication . Leça, João Micael; Pereira, Vanda; Miranda, Andreia; Vilchez, José Luís; Malfeito-Ferreira, Manuel

The impact of selected non-Saccharomyces yeasts on the occurrence of ethyl carbamate (EC) was evaluated. Hanseniaspora uvarum, Starmerella bacillaris, Pichia terricola, Pichia fermentans and Pichia kluyveri isolated from Madeira Island vineyards were inoculated in Tinta Negra musts. Urea, citrulline (Cit) and arginine (Arg) were quantified when the density of musts attained the levels to obtain sweet (1052 5 g/L) and dry (1022 4 g/L) Madeira wines. The urea concentration varied between 1.3 and 5.3 mg/L, Cit from 10.6 to 15.1 mg/L and Arg between 687 and 959 mg/L. P. terricola and S. bacillaris generated lower levels of urea (<2.5 mg/L), Cit (<11.0 mg/L) and Arg (<845.6 mg/L). The five resulting fortified wines, individually fermented by the selected non-Saccharomyces yeast, were exposed to laboratory-accelerated aging at 70 C for 1 month. From the studied yeasts, P. terricola and S. bacillaris revealed a lower potential to form EC (<100 g/L); therefore, both yeasts can be a useful tool for its mitigation in wines

2021Journal article

Open access

Characterisation of Films Based on Exopolysaccharides from Alteromonas Strains Isolated from French Polynesia Marine Environments

Publication . Concórdio-Reis, Patrícia; Pereira, João R.; Delgado Alves, Vitor; Nabais, Ana R.; Neves, Luísa A.; Marques, Ana C.; Fortunato, Elvira; Moppert, Xavier; Guezennec, Jean; Reis, Maria A.M.; Freitas, Filomena

This work assessed the film-forming capacity of exopolysaccharides (EPS) produced by six Alteromonas strains recently isolated from different marine environments in French Polynesia atolls. The films were transparent and resulted in small colour alterations when applied over a coloured surface (ΔEab below 12.6 in the five different colours tested). Moreover, scanning electron microscopy showed that the EPS films were dense and compact, with a smooth surface. High water vapour permeabilities were observed (2.7–6.1 × 10−11 mol m−1 s−1 Pa−1), which are characteristic of hydrophilic polysaccharide films. The films were also characterised in terms of barrier properties to oxygen and carbon dioxide. Interestingly, different behaviours in terms of their mechanical properties under tensile tests were observed: three of the EPS films were ductile with high elongation at break (ε) (35.6–47.0%), low tensile strength at break (Ꞇ) (4.55–11.7 MPa) and low Young’s modulus (εm) (10–93 MPa), whereas the other three were stiffer and more resistant with a higher Ꞇ (16.6–23.6 MPa), lower ε (2.80–5.58%), and higher εm (597–1100 MPa). These properties demonstrate the potential of Alteromonas sp. EPS films to be applied in different areas such as biomedicine, pharmaceuticals, or food packaging

2022Journal article

Open access

Chalcolithic copper production and use in the western end of the Iberian Peninsula: the testimony of Castro de Chibanes (Portugal)

Publication . Valério, Pedro; Soares, Joaquina; Alves, Luís C.; Silva, Rui J.C.; Araújo, Maria de Fátima; Silva, Carlos Tavres da

Recent archaeological excavations identified a prehistoric occupation at Castro de Chibanes (Setúbal Peninsula, Portugal) displaying ceramic crucibles and metal artefacts in stratigraphic levels assigned to 2500–1900 cal BC. Apart from basic tools such as flat axes and awls, the collection includes ceramic crucibles, with emphasis to an uncommon example with a pouring lip and four feet. The studied set was completed with metal prills and artefacts from neighbouring Chalcolithic settlements of Rotura and Pedrão. The studied collection was characterised by chemical and microstructural techniques (p-EDXRF, micro-PIXE, optical microscopy and SEM-EDS). Overall, the results point to a local production of copper with variable arsenic contents, agreeing with the composition of artefacts (Cu with 0.14 to 4.4 wt% As), whose post-casting manufacture included hammering and annealing (recrystallized grains and annealing twins), although with incipient conditions that prevented a full compositional homogenisation. These results were compared with the Chalcolithic metallurgy of southwestern Iberian Peninsula, allowing to integrate the Setúbal Peninsula region into a wider context of metal production and use during the 3rd millennium BC. Finally, a supposed Bell Beaker “tanged dagger” was found to be composed by a leaded bronze alloy with a worked microstructure exhibiting Cu-Fe sulphides with high Se contents. The contradiction between analytical features and ancient chronology led to a revision of the typology and chronology of this bronze, showing the importance of the integration of analytical and archaeological research.

2023Journal article

Restricted access