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Photonic band gap and bactericide performance of amorphous sol-gel titania
Publication . Gonçalves, M. Clara; Pereira, José Carlos; Matos, Joana C.; Vasconcelos, Helena Cristina; CeFITec – Centro de Física e Investigação Tecnológica; MDPI - Multidisciplinary Digital Publishing Institute
In addition to its traditional application in white pigments, nanocrystalline titania (TiO 2 ) has optoelectronic and photocatalytic properties (strongly dependent on crystallinity, particle size, and surface structure) that grant this naturally occurring oxide new technological applications. Sol-gel is one of the most widely used methods to synthesize TiO 2 films and NPs, but the products obtained (mostly oxy-hydrated amorphous phases) require severe heat-treatments to promote crystallization, in which control over size and shape is difficult to achieve. In this work, we obtained new photocatalytic materials based on amorphous titania and measured their electronic band gap. Two case studies are reported that show the enormous potential of amorphous titania as bactericide or photocatalyst. In the first, amorphous sol-gel TiO 2 thin films doped with N (TiO 2−x N x , x = 0.75) were designed to exhibit a photonic band gap in the visible region. The identification of Ti-O-N and N-Ti-O bindings was achieved by XPS. The photonic band gaps were found to be 3.18 eV for a-TiO 2 and 2.99 eV for N-doped a-TiO 2 . In the second study, amorphous titania and amine-functionalized amorphous titania nanoparticles were synthetized using a novel base-catalysed sol-gel methodology. All the synthesized amorphous TiO 2 nanoparticles exhibit bactericide performance (E. coli, ASTME 2149-13).
Unveiling the mechanism of action of 7α-acetoxy-6β-hydroxyroyleanone on an mrsa/visa strain: Membrane and cell wall interactions
Publication . Pereira, Filipe; Figueiredo, Teresa A.; de Almeida, Rodrigo F. M.; Antunes, Catarina A. C.; Garcia, Catarina; Reis, Catarina P.; Ascensão, Lia; Sobral, Rita G.; Rijo, Patricia; UCIBIO - Applied Molecular Biosciences Unit; DCV - Departamento de Ciências da Vida; MDPI - Multidisciplinary Digital Publishing Institute
The number of cases of failure in the treatment of infections associated with resistant bacteria is on the rise, due to the decreasing efficacy of current antibiotics. Notably, 7α-Acetoxy-6β-hydroxyroyleanone (AHR), a diterpene isolated from different Plectranthus species, showed antibacterial activity, namely against Methicillin-resistant Staphylococcus aureus (MRSA) strains. The high antibacterial activity and low cytotoxicity render this natural compound an interesting alternative against resistant bacteria. The aim of this study is to understand the mechanism of action of AHR on MRSA, using the MRSA/Vancomycin-intermediate S. aureus (VISA) strain CIP 106760, and to study the AHR effect on lipid bilayers and on the cell wall. Although AHR interacted with lipid bilayers, it did not have a significant effect on membrane passive permeability. Alternatively, bacteria treated with this royleanone displayed cell wall disruption, without revealing cell lysis. In conclusion, the results gathered so far point to a yet undescribed mode of action that needs further investigation.
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Fundação para a Ciência e a Tecnologia
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5876
Número da atribuição
UID/AMB/50017/2013