Browsing by Author "Guedes, Rita"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Antimicrobial Ceramic Filters for Water Bio-DecontaminationPublication . Ferreira, Olga; Rijo, Patricia; Gomes, João; Santos, Ricardo; Monteiro, Sílvia; Guedes, Rita; Serralheiro, Maria Luísa; Gomes, Marisa; Gomes, Luciana C.; Mergulhão, Filipe J.; Silva, Elisabete R.Bio-contamination of water through biofouling, which involves the natural colonization of submerged surfaces by waterborne organisms, is a global socio-economic concern, allied to premature materials bio-corrosion and high human health risks. Most effective strategies release toxic and persistent disinfectant compounds into the aquatic medium, causing environmental problems and leading to more stringent legislation regarding their use. To minimize these side effects, a newly non-biocide-release coating strategy suitable for several polymeric matrices, namely polydimethylsiloxane and polyurethane (PU)-based coatings, was used to generate antimicrobial ceramic filters for water bio-decontamination. The best results, in terms of antimicrobial activity and biocide release, showed an expressed delay and a decrease of up to 66% in the population of methicillin-resistant Staphylococcus aureus bacteria on ceramic filters coated with polyurethane (PU)-based coatings containing grafted Econea biocide, and no evidence of biocide release after being submerged for 45 days in water. Biocidal PU-based surfaces were also less prone to Enterococcus faecalis biofilm formation under flow conditions with an average reduction of 60% after 48 h compared to a pristine PU-based surface. Biocidal coated filters show to be a potential eco-friendly alternative for minimizing the environmental risks associated with biofouling formation in water-based industrial systems.
- Complexation and full characterization of the tretinoin and dimethyl-βeta-cyclodextrin complexPublication . Ascenso, Andreia; Guedes, Rita; Bernardino, Raul; Diogo, Herminio; Carvalho, Filomena A.; Santos, Nuno C.; Silva, Aida M.; Marques, HelenaAbstract. The aim of this work is to prepare tretinoin/dimethyl-beta-cyclodextrin complexes and fully characterize them through various analytical techniques. According to the phase solubility studies performed, the equilibrium for maximum complexation is reached in about 8 days presenting an AL-type diagram (soluble complexes) corresponding mainly to 1:1 stoichiometry (Ks=13,600 M−1), although the possibility of the presence of 1:2 complexes was mathematically proven. Differential scanning calorimetry, X-ray diffraction and all the other analytical techniques have proven the presence of true complex formation in all the preparation methods tested. H-NMR and FTIR spectra allowed the selection of the best complexation method. The comparison between Raman spectra revealed that the more relevant feature is the band at 1,573 cm−1, which corresponds to the entire delocalization of the superconjugated system, and after inclusion is observed as a positive frequency shift. Based on these results and the data obtained by molecular modelling calculations, it is proposed that the structure of the drug included into the cyclodextrin corresponds to the side chain including the functional group COOH. The complex was also analysed by atomic force microscopy to determine its size distribution which was heterogeneous and polymodal. However, it could be observed that they all have the same phase constitution.
- Formulation of a tretinoin dimethyl-beta-cyclodextrin gel for topical administrationPublication . Ascenso, Andreia PH; Guedes, Rita; Raul, Bernardino; Rodrigues, Tiago; Marques, Helena
- Macrocyclic copper(II) complexesPublication . Fernandes, Ana S.; Gaspar, Jorge; Cabral, M. Fatima; Caneiras, Catia; Guedes, Rita; Rueff, Jose; Castro, Matilde; Costa, Judite; Oliveira, Nuno G.Synthetic superoxide dismutase mimetics have emerged as a potential novel class of drugs for the treatment of oxidative stress related diseases. Among these agents, metal complexes with macrocyclic ligands constitute an important group. In this work we synthesized five macrocyclic copper(II) complexes and evaluated their ability to scavenge the superoxide anions generated by the xanthine-xanthine oxidase system. Two different endpoints were used, the nitro blue tetrazolium (NBT) reduction assay (colorimetric method) and the dihydroethidium (DHE) oxidation assay (fluorimetric method). IC50 values in the low micromolar range were found in four out of five macrocyclic complexes studied, demonstrating their effective ability to scavenge the superoxide anion. The IC50 values obtained with the NBT assay for the macrocyclic copper(II) complexes, were consistently higher, approximately threefold, than those obtained with the DHE assay. Spectroscopic and electrochemical studies were performed in order to correlate the structural features of the complexes with their superoxide scavenger activity. Cytotoxicity assays were also performed using the MTT method in V79 mammalian cells and we found that the complexes, in the range of concentrations tested in the superoxide scavenging assays were not considerably toxic. In summary, some of the presented macrocyclic copper(II) complexes, specially those with a high stability constant and low IC50 appear to be promising superoxide scavenger agents, and should be considered for further biological assays. (c) 2007 Elsevier Inc. All rights reserved.