A carregar...
Projeto de investigação
Sem título
Financiador
Autores
Publicações
Combination of chemotherapy and Au-nanoparticle photothermy in the visible light to tackle doxorubicin resistance in cancer cells
Publication . Pedrosa, Pedro; Mendes, Rita; Cabral, Rita; Martins, Luísa M. D. R. S.; Baptista, Pedro V.; Fernandes, Alexandra R.; DCV - Departamento de Ciências da Vida; UCIBIO - Applied Molecular Biosciences Unit; Nature Publishing Group
Despite great advances in the fight against cancer, traditional chemotherapy has been hindered by the dose dependent adverse side effects that reduce the usable doses for effective therapy. This has been associated to drug resistance in tumor cells that often cause relapse and therapy failure. These drawbacks have been tackled by combining different therapeutic regiments that prevent drug resistance while decreasing the chemotherapy dose required for efficacious ablation of cancer. In fact, new metallic compounds have been in a continuous development to extend the existing chemotherapy arsenal for these combined regimens. Here, we demonstrate that combination of a metallic compound (TS265), previously characterized by our group, with photothermy circumvents cells resistant to Doxorubicin (DOX). We first engendered a colorectal carcinoma cell line (HCT116) highly resistant to DOX, whose viability was diminished after administration of TS265. Cancer cell death was potentiated by challenging these cells with 14 nm spherical gold nanoparticles followed by laser irradiation at 532 nm. The combination of TS265 with photothermy lead to 65% cell death of the DOX resistant cells without impacting healthy cells. These results support the use of combined chemotherapy and photothermy in the visible spectrum as an efficient tool for drug resistant tumors.
Effect of film thickness in gelatin hybrid gels for artificial olfaction
Publication . Esteves, Carina; Santos, Gonçalo M. C.; Alves, Cláudia; Palma, Susana I. C. J.; Porteira, Ana R.; Filho, João; Costa, Henrique M. A.; Alves, Vitor D.; Morais Faustino, Bruno M.; Ferreira, Isabel; Gamboa, Hugo; Roque, Ana C. A.; UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; LIBPhys-UNL; DF – Departamento de Física; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Elsevier BV
Artificial olfaction is a fast-growing field aiming to mimic natural olfactory systems. Olfactory systems rely on a first step of molecular recognition in which volatile organic compounds (VOCs) bind to an array of specialized olfactory proteins. This results in electrical signals transduced to the brain where pattern recognition is performed. An efficient approach in artificial olfaction combines gas-sensitive materials with dedicated signal processing and classification tools. In this work, films of gelatin hybrid gels with a single composition that change their optical properties upon binding to VOCs were studied as gas-sensing materials in a custom-built electronic nose. The effect of films thickness was studied by acquiring signals from gelatin hybrid gel films with thicknesses between 15 and 90 μm when exposed to 11 distinct VOCs. Several features were extracted from the signals obtained and then used to implement a dedicated automatic classifier based on support vector machines for data processing. As an optical signature could be associated to each VOC, the developed algorithms classified 11 distinct VOCs with high accuracy and precision (higher than 98%), in particular when using optical signals from a single film composition with 30 μm thickness. This shows an unprecedented example of soft matter in artificial olfaction, in which a single gelatin hybrid gel, and not an array of sensing materials, can provide enough information to accurately classify VOCs with small structural and functional differences.
LIVING CAPACITORS: FUNCTIONAL CHARACTERIZATION OF A NOVEL CYTOCHROME ACTING AS A NANOWIRE
Publication . Fernandes, Ana Paula Nascimento; Salgueiro, Carlos; Paquete, Catarina
In an Era where environmental issues are a growing concern, microorganisms that have remarkable features, such as extracellular electron transfer (EET) ability, present major opportunities in diverse biotechnological fields. Geobacter bacteria have shown an extraordinary respiratory flexibility, with its dissimilatory metal reduction ability and EET to electrode surfaces, and numerous c-type cytochromes were pointed as key players. However, the understanding of the mechanisms involved and hence, the advances in practical applications, are still in its early days and it is crucial to move further and unveil not only the components involved, but also their roles and partners in electron transfer.
The dodecaheme GSU1996, composed of four similar triheme domains (A–D), was proposed to work as a natural nanowire, owing to its linear structure and large number of hemes. In this work, the in vitro functional characterization of the GSU1996 was attempted, in a modular characterization based strategy. Here, the triheme domains C and D assisted in the characterization of the C-terminal end of GSU1996, the hexaheme fragment CD. The first step encompassed the assignment of the heme groups signals in the nuclear magnetic resonance spectra of the triheme domains and of the hexaheme fragment, which is the protein with the highest number of hemes assigned to date. The second step comprised the determination of the microscopic thermodynamic parameters of fragment CD. This provided mechanistic information on the dominant microstates and included the determination of the reduction potentials of the hemes, redox interactions between hemes and ionizable centers and among neighboring hemes. The third and final step consisted in the determination of the microscopic kinetic parameters of fragment CD. This unveiled details about the reactivity of the heme groups and included the calculation of the reference rate constants for each heme in the reduction/oxidation process. All combined, the data revealed that a heme located at the end of the C-terminal edge of GSU1996 shows the necessary skills to accept electrons from redox partners.
In vitro interaction studies performed between GSU1996 and the periplasmic cytochrome PpcA and its homologues (PpcC–E), revealed that it is possible that GSU1996 and PpcA may be redox partners in G. sulfurreducens, as they form a transient redox complex that involves the C-terminal fragment of GSU1996.
Work has also been started to disclose other electron transfer components of G. sulfurreducens, namely, the outer membrane tetraheme cytochrome OmcE; the hexaheme OmcS and the nanowire cytochrome GSU2210. New constructs and expression systems were tested, based in the pBAD vector, albeit none of the attempts have been successful.
Although in vitro studies provide information and allow the evaluation of the functional properties of these proteins, in vivo studies are essential to assess the actual roles and interacting partners in the cells. Therefore, a novel approach was also tested towards the in vivo labeling of c-type cytochromes, based in the attachment of a tetracysteine tag that is fluorescent upon binding with commercially available biarsenical dyes. However, no expression of the model tagged protein was accomplished.
Fungal biodeterioration of paper: development of safer and accessible conservation treatments
Publication . Sequeira, Sílvia Oliveira; Dinis, Maria Filomena; Cabrita, Eurico; Phillips, Allan
Great part of the History of mankind is registered in the form of documents or works of art on paper support. Paper can be deteriorated due to physical, chemical and biological agents. Within microorganisms, fungi are the major paper biodeteriogens. Throughout history, several toxic methods have been used to prevent and stop fungal deterioration on paper based materials. More recently, a growing concern about environmental and health issues has led to the research on new antifungal alternatives, with lower toxicity. However, the existent antifungal methods and compounds still have drawbacks in terms of efficacy, health hazards, damaging effects on paper, or lack of thorough testing. In this context, the present thesis focused on testing and developing accessible antifungal treatments with low toxicity, which could prevent the long term paper deterioration.
The selection of antifungal compounds was made taking into account the results from a literature review on antifungals used on paper conservation, a survey to paper conservators, and a review of antifungals used in cosmetics and pharmaceutical industries, having as a basic premise their low toxicity. Aspergillus niger, Chaetomium globosum, Cladosporium cladosporioides, Penicillium chrysogenum and Penicillium corylophilum were selected as test fungal species. Fungal growth on paper was evaluated by measuring colonization areas and biomass dry weight determination.
A formulation containing parabens and calcium propionate (PBs+CP) presented the best antifungal activity on paper samples, followed by a formulation containing clotrimazole and calcium hydroxide nanoparticles (CLT+NPs), and ultimately 70% ethanol (70%EtOH).
Before application on cultural heritage materials, conservation treatments have to be thoroughly tested to assess if they can cause any damage on the treated materials in the short and long term. The effects of the tested formulations on paper were evaluated in terms of pH, colourimetry, folding endurance and molecular alterations, using moist heat artificial ageing. Besides plain paper, paper previously biodeteriorated by A. niger was tested in order to evaluate the potential of each compound to prevent further deterioration caused by fungal metabolites. The obtained results on biodeteriorated samples illustrate how tremendously damaging the products excreted by fungi can be in the long term. PBs+CP formulation was the only one capable of preventing long term acidification, loss of folding endurance, and discoloration caused by fungal metabolites, but on the other hand, on plain samples, this formulation caused paper discoloration. CLT+NPs formulation significantly prevented the acidification and loss of folding endurance, although causing a minor discoloration on paper at a long term. 70%EtOH had a mild positive impact in the chemical stabilization of paper and did not cause any paper discoloration.
The information provided in this thesis contributes to a deeper understanding on safer options for preventing and treating paper deterioration by fungi and opens the way for further research in this challenging field of heritage conservation.
Interaction of caffeic acid with SDS micellar aggregates
Publication . Cid, Antonio; Moldes, Oscar A.; Mejuto, Juan C.; Simal-Gandara, Jesus; UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; LAQV@REQUIMTE; MDPI - Multidisciplinary Digital Publishing Institute
Micellar systems consisting of a surfactant and an additive such as an organic salt or an acid usually self-organize as a series of worm-like micelles that ultimately form a micellar network. The nature of the additive influences micellar structure and properties such as aggregate lifetime. For ionic surfactants such as sodium dodecyl sulfate (SDS), CMC decreases with increasing temperature to a minimum in the low-temperature region beyond which it exhibits the opposite trend. The presence of additives in a surfactant micellar system also modifies monomer interactions in aggregates, thereby altering CMC and conductance. Because the standard deviation of β was always lower than 10%, its slight decrease with increasing temperature was not significant. However, the absolute value of Gibbs free enthalpy, a thermodynamic potential that can be used to calculate the maximum of reversible work, increased with increasing temperature and caffeic acid concentration. Micellization in the presence of caffeic acid was an endothermic process, which was entropically controlled. The enthalpy and enthropy positive values resulted from melting of “icebergs” or “flickering clusters” around the surfactant, leading to increased packing of hydrocarbon chains within the micellar core in a non-random manner. This can be possibly explained by caffeic acid governing the 3D matrix structure of water around the micellar aggregates. The fact that both enthalpy and entropy were positive testifies to the importance of hydrophobic interactions as a major driving force for micellization. Micellar systems allow the service life of some products to be extended without the need to increase the amounts of post-harvest storage preservatives used. If a surfactant is not an allowed ingredient or food additive, carefully washing it off before the product is consumed can avoid any associated risks. In this work, we examined the influence of temperature and SDS concentration on the properties of SDS–caffeic acid micellar systems. Micellar properties can be modified with various additives to develop new uses for micelles. This allows smaller amounts of additives to be used without detracting from their benefits.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
5876
Número da atribuição
UID/Multi/04378/2013