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Mountain Research Center
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Bioactive and Phenolic Profiles in Pinus pinaster Bark: A Comparative Study of Microwave and Ultrasound Extraction Methods
Publication . Barros, Diana; Alonso-Esteban, José Ignacio; Finimundy, Tiane C.; Pereira, Carla; Vaz, Josiana A.; Pereira-Pinto, Ricardo; Fernandes, Élia; Pires, Preciosa; Santos, Joana; Barros, Lillian; Vaz-Velho, Manuela
This study conducted a comprehensive comparison of two green extraction methods, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE), for recovering bioactive phenolic compounds from Pinus pinaster bark. The goal was to valorize timber industry waste and enhance the value of by-products through the development of eco-friendly processes to extract phenolic compounds from Pinus pinaster Aiton subsp. atlantica in northwest Portugal. MAE achieved significantly higher extraction yields than UAE (11.13 vs. 3.47 g extract/100 g bark) and superior total phenolic content (833 vs. 514 mg GAE/g). MAE extracts also exhibited enhanced antioxidant activity in most assays tested (DPPH, ABTS, ORAC, and OxHLIA), while both extracts effectively inhibited lipid peroxidation (TBARS) and showed activity against Gram-positive bacteria. Phenolic profile analysis revealed that MAE recovered a substantially higher amount of total phenolic compounds (230.0 mg/g) compared to UAE (86.95 mg/g), with procyanidins identified as the predominant compounds. The greater recovery of this complex procyanidin mixture by MAE is strongly associated with the enhanced bioactivities observed. Overall, this study confirms MAE as a highly efficient and sustainable technology for transforming pine bark waste into valuable antioxidant and antimicrobial extracts with potential applications in the food and pharmaceutical industries.
Chitosan-xanthan gum-based hydrogels loaded with essential oil distillation by-products of Aloysia citrodora Paláu for antimicrobial systems
Publication . Almeida, Heloísa H.S.; Santamaria-Echart, Arantzazu; Amaral, Joana S.; Aquino, Leandro Lima ; Rodrigues, Alírio E.; Barreiro, Filomena
Hydrogels, 3D hydrophilic networks formed by oppositely charged biopolymers like chitosan and xanthan gum, offer a safe, non-toxic, and biocompatible option for delivery applications. Essential oil (EO) by-products, such as hydrosols and wastewater, are sources of antioxidant and antimicrobial compounds, but their high dilution can limit direct applications. In this context, this work focused on the development of hydrogels via electrostatic complexation incorporating hydrosol and wastewater by-products from the steam distillation of Aloysia citrodora Palau, using a two-stage approach: (a) initial loading during hydrogel formation and (b) subsequent reloading of the hydrogels to further enhance the concentration of bioactive compounds. The effect of pH (4, 7, and 11) on polymer complexation was evaluated, as it influences polymer-polymer and polymer-bioactive compound interactions by modifying the protonation and deprotonation states of their functional groups. This effect was evident in swelling, release kinetics, morphology, and rheological properties. Fourier-transform infrared (FTIR) analysis confirmed the successful formation of the polymer complex. Neutral pH hydrogels showed the highest hydrosol entrapment (70.3%) and were selected as the most promising systems. Biological characterisation showed that the reloading process enhanced bioactivity. Wastewater-load-reload improved antioxidant capacity, driven by the high phenolic content. Moreover, hydrosol-loaded-reload systems exhibited antimicrobial activity, with bactericidal effects against Staphylococcus aureus and Escherichia coli, outperforming both unloaded and loaded systems. These findings highlight the potential of loading and reloading steps to valorise EO by-products, producing sustainable, functional hydrogels with high bioactivity, suitable for food, pharmaceutical, medical, and biotechnological applications.
Tunable physicochemical properties of PDMS@nanoparticle composites: modifications, mechanisms, and emerging applications
Publication . Cardoso, B.D.; Nobrega, Glauco; Afonso, Inês Santos ; Souza, Andrews; Neves, Lucas B.; Faria, C.L.; Díaz de Tuesta, Jose Luis; Ribeiro, J.E.; Lima, Rui A.
Polydimethylsiloxane@nanoparticles (PDMS@NPs) composites represent a versatile class of advanced elastomers whose physicochemical behavior can be finely tuned through nanoscale interfacial design and nanofiller morphology. Owing to their inherent flexibility, transparency, and chemical stability, PDMS based systems have emerged as model platforms for developing multifunctional materials with optimized mechanical, thermal, electrical, optical, acoustic and wetting properties. This review systematically elucidates the structure property relationships in PDMS@NPs composites and the interaction mechanisms between NPs and polymer chains that enable tunable control over bulk and interfacial behavior, with particular emphasis on how NPs dimensionality and aspect ratio (0D, 1D, and 2D fillers) regulate stress transfer, transport pathways, and functional interconnectivity within the matrix. Three main NP incorporation strategies, (namely, physical mixing of presynthesized NPs, in situ synthesis on cured PDMS, and in situ formation within uncured matrices) are critically compared in terms of interfacial coupling, dispersion stability, and processing scalability. Particular attention is given to how interfacial engineering, nanofiller morphology, and hierarchical architecture govern stress transfer, phonon transport, charge percolation, and optical or surface responses. In addition, a property design prospective is presented that links interphase design and nanofiller morphology to mechanical, thermal, electrical, optical, acoustic and wetting-controlled surface properties. This review further critically examines the limiting factors that reduce the applicability of PDMS@NPs composites, including performance degradation, interface instability, and limited recyclability, as well as long-term stability under mechanical, thermal, optical, and environmental conditions. Emerging directions such as green filler synthesis, recyclable PDMS matrices, dynamic and hi-erarchical interphases, and predictive modeling of morphology-dependent dynamic interfaces are outlined. Overall, this review provides a comprehensive and critical perspective on PDMS@NPs composites as a next generation of soft, functional, and sustainable elastomeric materials, opening new avenues for advances in flexible electronics, soft robotics, biomedical devices, and adaptive coatings.
Estudio clínico-epidemiológico de la población de Bragança con sospecha de alergia al polen y a la espora fúngica Alternaria alternata
Publication . Ferrage, Erica Vanessa Reis; Fraga, José; Feliciano, Manuel; Sánchez-Reyes, Estefanía
La exposición al polen y a las esporas fúngicas constituye un factor ambiental crítico en la fisiopatología de las enfermedades respiratorias alérgicas, cuya prevalencia ha ido aumentando en entornos urbanos, caracterizados por condiciones ecológicas favorables. En este contexto, el presente estudio tuvo como objetivo caracterizar, desde el punto de vista clínico y epidemiológico, a la población de Bragança con sospecha de alergia al polen y a Alternaria alternata. Se trata de un estudio observacional, descriptivo, transversal y retrospectivo, basado en el análisis de 100 historias clínicas, con datos obtenidos mediante cuestionarios estructurados y pruebas cutáneas por punción (prick-test) con trece extractos alergénicos: doce polínicos y uno específico de Alternaria alternata. La muestra estuvo compuesta mayoritariamente por individuos de género femenino (53 %), con edad media de 23,9 ± 15,3 años, predominando residentes en zonas urbanas (86 %). El 42 % tenía animales de compañía, el 37 % presentaba exposición al tabaco y el 19 % vivía en viviendas con moqueta. Los síntomas más frecuentes fueron rinitis alérgica (99 %), rinoconjuntivitis (97 %), eccema (45 %) y sibilancias (44 %). Se observó polisensibilización en el 97 % de los participantes, con sensibilizaciones dirigidas a mezclas de gramíneas silvestres (96 %), gramíneas cultivadas (82 %), Olea europaea L. (80 %), mezclas de hierbas (78 %), Plantago lanceolata L. (75 %) y Alternaria alternata (Fr.) Keissl. (8 %). Estas evidencias permiten concluir un patrón de sensibilización compatible con alergias respiratorias en la población de Bragança.
Experimental and dynamic modeling study of CO2/N2 separation on ion-exchanged binder-free LTA zeolites for post-combustion carbon capture
Publication . Karimi, Mohsen; Aly, Ezzeldin; Rodrigues, Alírio E.; Freitas, Francisco A. Da Silva; Silva, José A.C.
Ion-exchange modification of commercial binder-free zeolites offers a promising strategy to improve adsorption-based CO2 capture from post-combustion flue gases. In this study, the CO2/ N-2 separation performance of ion-exchanged binder-free Linde-Type A (LTA) zeolites-namely 4 A, 5 A, Sr(40)A, and Sr(80)A-was systematically evaluated under post-combustion capture (PCC) conditions. Adsorption isotherms were measured over the temperature range of 306-344 K and pressures up to 350 kPa. The CO2 uptake followed the order: 5 A > Sr(40)A > Sr(80)A > 4 A, with 5 A achieving the highest loading of 5.58 mol center dot kg(-1) at 120 kPa and 306 K, compared to 4.47 mol center dot kg(-1) for Sr(40)A, 4.45 mol center dot kg(-1) for Sr(80)A, and 3.73 mol center dot kg(-1) for 4 A. The presence of divalent cations (Ca2+ and Sr2+) strengthened the electrostatic interactions, thereby enhancing CO2 affinity relative to the Na-exchanged 4 A. Binary CO2/N-2 breakthrough experiments demonstrated that Sr(80)A exhibited the highest selectivity (75 at 10 kPa and 306 K), followed by 5 A (60), 4 A (51), and Sr(40)A (47). Which the developed mathematical model accurately captured the breakthrough behavior and dynamic performance of the fixed-bed system. Finally, a Response Surface Methodology (RSM) was applied to the statistical analysis of selectivity of different studied zeolites and getting the optimum operating conditions.
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Fundação para a Ciência e a Tecnologia
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CIMO
Número da atribuição
UID/00690/2025