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- Material de Construção do Ninho da Vespa Asiática - Um contributoPublication . Sedira, Naim; Gomes, Ana; Nepomuceno, Miguel; Paiva, Anabela; Bentes, I.; Pinto, Jorge Tiago Queirós da Silva; Pereira, SandraMuitos trabalhos de investigação têm vindo a ser desenvolvidos no sentido de encontrar novas soluções para os diversos contextos da ciência através da bio-inspiração. Este trabalho está centrado no estudo do ninho da vespa asiática e, em particular, no estudo do seu material de construção. Esta construção natural é complexa em todas a vertentes. A sua complexidade arquitetónica, estrutural, material, funcional, entre outros aspetos técnicos, são fatores que despertam a curiosidade, esta construção pode ainda apresentar dimensões relativamente grandes. Ela é construída e usada aproximadamente meio ano e não volta a ser reutilizada. Este é outro aspeto técnico que motiva um estudo tendo em conta a escassez de habitação a nível mundial. O material de construção também é interessante e inovador. Neste ponto, tentou-se compreender a constituição deste material através da realização de ensaios MEV-EDS de amostras do material do ninho retiradas em diferentes zonas. Amostras de folhas de árvore foram analisadas para serem usadas como referência. As imagens de MEV mostram que o ninho da vespa asiática é feito de fibras vegetais e pedaços de madeira mastigadas, com sulcos e poros para manipulação, troca de gases e regulação de temperatura e humidade. A análise EDS do material do ninho de vespas asiáticas indica origem vegetal, com elementos como carbono (C) e oxigénio (O) formando 82,31%, e magnésio (Mg), potássio (K), cálcio (Ca) e ferro (Fe) constituindo 9,43%. Alumínio (Al) e silício (Si) representam 7,41%. A saliva das vespas é crucial para a construção. Importa acrescentar que este material é utilizado na construção da fachada do ninho, a qual, apesar de estar diretamente exposta às intempéries, proporciona uma durabilidade adequada. O interior do ninho da vespa asiática também garante o conforto necessário para a reprodução destes insetos. Este trabalho tem como principal objetivo partilhar com a comunidade cientifica alguns dos resultados alcançados por esta equipa de investigação neste contexto.
- Optimização da Técnica de Preparação de Amostras de Betões Refractários Auto-Escoantes de Alumina Sem Cimento Para Observação MicroscópicaPublication . Silva, Abílio P.; Gomes, Ana; Segadães, Ana Maria; Devezas, TessalenoA preparação de amostras para a observação de superfícies em microscopia requer um procedimento de corte, rectificação e polimento rigoroso que obedeça a requisitos sistemáticos de avaliação da qualidade superficial. Neste trabalho, um novo material constituído por 100% de alumina, mas de ingredientes (matriz e agregado) com características distintas obrigou, à implementação de uma nova receita de polimento e de realce dos contrastes entre os elementos estruturais presentes. Assim, apresenta-se um procedimento optimizado para a preparação das amostras de betões refractários auto-escoantes de alumina sem cimento para análise da microestrutura em microscópio metalográfico em complementaridade com o microscópio electrónico de varrimento.
- Layer-by-Layer deposition of bioactive polyelectrolytes with incorporation of antimicrobial agents as a new strategy to develop bioactive textilesPublication . Gomes, Ana Paula de Ascensão Rosa; Gouveia, Isabel Cristina Aguiar de Sousa e Silva; Mano, João Filipe Colardelle da Luz; Queiroz, João António de Sampaio RodriguesPolyelectrolyte multilayer coatings have become a new and general way to functionalize a variety of materials. Particularly, the Layer-by-Layer (LbL) method is a technique developed for the coating of solid surfaces. The LbL technique presents a unique mean to construct surface coatings that can conform to a variety of biomaterial surfaces and serve as matrices enabling controlled delivery of bioactive molecules from surface. As the deposition process is achieved in aqueous medium, incorporation of active agents is possible since the coatings obtained by LbL are less densely packed and this is advantageous for diffusion through the coating. The coating is constructed by the alternate adsorption of oppositely charged polyelectrolytes at the surface of the material, easily obtained when it is dipped in polyelectrolyte solutions. A deposition cycle creates a layer, and these cycles can be repeated as often as needed. This study aims to obtain novel bioactive textiles with potential application as wound-dressings. The biopolymers chosen for the functionalization of cotton (substrate), were chitosan (CH) and alginate (ALG). The multilayer coating of cotton with CH and ALG is constructed by the adsorption of CH and ALG with opposite charge on the surface of cotton substrates. The successive deposition of multilayers of CH and ALG was analyzed by three different techniques. Contact angle between a water droplet and the surface of the sample, cationic dye staining method and analysis by ATR-FTIR (Fourier Transform Infrared spectroscopy with Attenuated Total Reflection). These techniques showed that there was alternating deposition between CH and ALG and the presence of electrostatic bonds between the layers. In order to evaluate the antibacterial activity of the functionalized cotton, the Japanese standard JIS L 1902:2002 for the halo method (qualitative assay), and the absorption method (quantitative test) were assessed. These tests revealed an antibacterial effect on the functionalized cotton for both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Klebsiella pneumoniae). In addition a method was optimized for incorporating L-cysteine (L-cys) between the layers of CH and ALG deposited on cotton samples by the LbL, in order to obtain a better antimicrobial effect. Several strategies were used and the best results were obtained by the method where the ALG turns into a gel in the presence of calcium, since L-cys can be incorporated directly between the layers of CH and ALG without any covalent bond. Thus, the bioactive L-cys agent was immobilized without losing its bioactive characteristics. These new samples were analyzed for the antibacterial activity against Staphylococcus aureus and Klebsiella pneumoniae according with the previously used standard, and the results showed an increase in the antibacterial effect due to the presence of L-cys. This new coating method has the great advantage to able to select other types of bioactive agents without needing further optimization. In this way, L-Cys was replaced by antimicrobial peptides (AMPs). The reason for the use of AMPs is related with the continuous use of antibiotics which resulted in multiresistant bacterial strains all over the world. Consequently, there is an urgent need to search for alternatives for antibiotics. The AMPs are the new generation of antimicrobials. Four AMPs of different features were used. The depth in which each AMPs is incorporated between the layers was determined by energy dispersive analysis of X-rays (Energy Dispersive X-ray EDS). Results showed, that all AMPs used have a higher antimicrobial effect when compared with previous samples (with and without L-Cys) for both microorganisms and are non-cytotoxic to normal human dermal fibroblasts at the tested Concentrations. This confirms that this new functionalization approach of cotton coated with layers of CH and ALG by the LbL technique with incorporated AMPs leads to good antibacterial and cytotoxicity results, which make them suitable to be used as wound dressings.
- Layer-by-Layer Deposition of Antibacterial Polyelectrolytes on Cotton FibresPublication . Gomes, Ana; Mano, João F.; Queiroz, João; Gouveia, Isabel C.The introduction of molecules with biological properties on textile materials is essential for a number of biotechnological applications. With the purpose of testing new processes applied to textiles, in this study, we present the first results on the feasibility of using the Layerby-Layer (LbL) deposition process in natural fibers such as cotton, with natural polyelectrolytes like chitosan (CH) and alginic acid sodium salt (ALG), the durability of CH/ALG multilayer on cotton were evaluated. The increase of negative charges to the substrate cotton was made with NaBr and TEMPO, to ensure the success of the process of LbL. Three characterization methods to assess electrostatic LbL deposition were performed: the contact angle between a liquid (water) and the sample surface, in order to characterize the wettability of the samples with the different layers of CH and ALG; dyeing of the CH/ALG assembled cotton fabric with cationic methylene blue that shows regular changes in terms of color depth (K/S value), which indicate that the surface were alternately deposited with CH and ALG layers and, finally, the analysis by infrared spectroscopy using Fourier Transform with Attenuated Total Reflection (ATR-FTIR), to assess the changes in the interaction between CH and ALG deposited on cotton samples.
- New garment proposal for prevention of spreading Gram-negative bacteria resistant to carbapenem antibiotic class under hospital settingsPublication . Nogueira, Frederico; Gomes, Ana; Gouveia, Isabel C.Sensitive skin diseases, including atopic dermatitis, skin inflammation and bedsores, leave patients vulnerable under hospital setting. It is important for the development of a hospital gown with ‘‘soft hand’’ properties and at the same time as a protector against nosocomial infections. Klebsiella pneumoniae has developed resistance to antibiotics in the carbapenem antibiotic class, known as carbapenem-resistant K. pneumoniae (CRKP). CRKP is resistant to nearly all antibiotics and can kill up to 50% of infected patients. This work consisted in the development of a washable recycled silk fibroin-based gown covalently linked with an amino acid L-Cysteine(L-Cys), focused on prevention of K. pneumoniae establishment, proliferation and spreading to community, for use under hospital settings. With the growing problem of resistance to antibiotics and few new therapies on the horizon, gowns adsorbed with L-Cys show to function as a barrier to the establishment and proliferation of microorganisms, providing user protection from infectious disease. This gown was knitted at a rectilinear needle loom with a Jersey knit structure. Then it was cross-linked with L-Cys, subjected to laundry, and subsequently characterized by energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, contact angle, free energy of adhesion, scanning electron microscopy and transmission electron microscopy. Results presented a bactericidal effect against K. pneumoniae of 94.92% after three rinses and 88.88% after five washing cycles, with the few adhered bacteria with an altered and compromised morphology.
- Investigating the Architecture and Characteristics of Asian Hornet Nests: A Biomimetics Examination of Structure and MaterialsPublication . Sedira, Naim; Pinto, Jorge; Ginja, Mário; Gomes, Ana; Nepomuceno, Miguel C. S.; Pereira, SandraThis study investigates the internal architecture of Asian hornet nests (AHNs) using advanced imaging techniques, such as CT scanning and X-ray radiography, to understand their construction and function. The primary objective and significance of this study centre on drawing inspiration from the creative way Asian hornets construct their nests, with a particular focus on the architecture, design, functionality, and building materials of these nests. The architectural principles governing the construction of these nests, such as the arrangement of hexagonal cells, pedicels for load bearing, and adhesive materials, serve as a source of inspiration for innovative and sustainable design practices. The pedicels in Asian hornet nests play a crucial role in transferring load and ensuring stability. Additionally, AHNs’ adhesion to tree branches is essential for preventing collapse, and the pedicels provide necessary structural support. The knowledge gained from studying AHNs’ internal architecture could be applied directly to the architecture and civil engineering fields to improve structure stability and durability. The microstructure analysis of the paper-like material that hornets produce to build their nests indicates a complex and heterogeneous structure, composed of various plant fragments and fibres. This unique composition creates intricate grooves and pores, which are essential for regulating temperature and humidity levels within the outer envelope of the nest. The study of Asian hornet nests’ internal structure demonstrated that nature’s engineering principles inspire the design of durable and resilient structures in the construction industry. Civil engineers can incorporate similar principles into their designs to enhance the structural integrity and performance of buildings, bridges, and other infrastructure.
- Layer-by-layer deposition of antimicrobial polymers on cellulosic fibers: a new strategy to develop bioactive textilesPublication . Gomes, Ana; Mano, João F.; Queiroz, João; Gouveia, Isabel C.In recent years, there has been an increase of infectious diseases caused by different microorganisms and the development of antibiotic resistance. In this way, the search for new and efficient antibacterial materials is imperative. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan (CH) and alginates (ALG). In this study, a simple technique of Layer by Layer (LbL) of applying polycation CH and polyanion ALG was used to prepare CH/ALG multilayers on cotton samples via the electrostatic assembly with success. The CH/ALG cotton samples (functionalized) were investigated for their antibacterial properties towards Staphylococcus aureus and Klebsiella pneumonia using the international standard method JIS L 1902:2002. The antibacterial activity of the functionalized samples was tested in terms of bacteriostatic and bactericidal activity, and results showed that the samples exhibited a bacteriostatic effect on the two bacteria tested, as expected. In addition, samples with five layers (CH/ALG/CH/ALG/CH) were more effective in inhibiting bacterial growth. This new coating for cellulosic fibers is a new strategy and may open new avenues for the development of antimicrobial polymers with potential application in health-care field.
- Microstructural properties of Asian hornet nest paper-like materials: Preliminary step towards biomimicry materials for civil engineering applicationsPublication . Sedira, Naim; Pinto, Jorge; Gomes, Ana; Nepomuceno, Miguel; Pereira, SandraThis paper presents a comprehensive examination of the microstructure and mineralogy of the paper-like material found in Asian hornet nests (referred to as AHN P-LM) and the nearby tree leaves, utilising scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The analysis conducted through SEM-EDS demonstrates that AHN P-LM is primarily composed of plant fragments, with slight traces of inorganic substances (such as CaOx). The thread-like morphologies observed in the SEM analysis, which are linked to the secretion of hornets, warrant attention due to their significance in understanding the microstructure of AHN P-LM. The presence of nitrogen (N) in the EDS analysis of AHN P-LM, in contrast to its absence in analysed leaves, strongly implies that the nitrogen originates from hornet saliva. Additionally, SEM-EDS analysis revealed the impact of chemical composition variations on colour differences within AHN P-LM. Furthermore, X-ray diffraction analysis on ash samples from AHN P-LM confirmed the presence of minerals such as quartz, lime, phlogopite, and microcline. These findings about mineral composition align closely with results obtained from SEM-EDS analyses, presenting various aspects related to understanding the structure and compositional makeup of AHN P-LM. Biomimicry principles can be applied to draw inspiration from the AHN P-LM for replication in the civil engineering field, facilitating innovative solutions. Understanding hornet behaviour and nest material composition is essential. Future outlook includes utilising these materials in wood construction, 3D printing for structural components, shelters, infrastructure repair, green building, and architectural innovation.
- Incorporation of antimicrobial peptides on functionalized cotton gauzes for medical applicationsPublication . Gomes, Ana; Mano, João F.; Queiroz, João; Gouveia, Isabel C.A large group of low molecular weight natural compounds that exhibit antimicrobial activity has been isolated from animals and plants during the past two decades. Among them, peptides are the most widespread resulting in a new generation of antimicrobial agents with higher specific activity. In the present study we have developed a new strategy to obtain antimicrobial wound-dressings based on the incorporation of antimicrobial peptides into polyelectrolyte multilayer films built by the alternate deposition of polycation (chitosan) and polyanion (alginic acid sodium salt) over cotton gauzes. Energy dispersive X ray microanalysis technique was used to determine if antimicrobial peptides penetrated within the films. FTIR analysis was performed to assess the chemical linkages, and antimicrobial assays were performed with two strains: Staphylococcus aureus (Gram-positive bacterium) and Klebsiella pneumonia (Gram-negative bacterium). Results showed that all antimicrobial peptides used in this work have provided a higher antimicrobial effect (in the range of 4 log-6 log reduction) for both microorganisms, in comparison with the controls, and are non-cytotoxic to normal human dermal fibroblasts at the concentrations tested.