Browsing by Author "Silva, Sandra"
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- Activated carbons: efficient materials for the removal of multi- resistant bacteriaPublication . Silva, Sandra; Jordao, Luisa; Duarte, Aida; Carvalho, Ana PaulaThe rapid emergence of multi-resistant bacteria is occurring worldwide being hospital effluent a major source of these microorganisms. To remove these bacteria possible strategies are those involving activated carbon that due to their tunable properties can be suitable adsorbents for different types of microorganisms, for example Gram + or Gram – bacteria. The objective of this study was to test an activated carbon (AC) commercialized for water treatment purpose to reduce the content of bacteria commonly detected in hospital wastewater. The assays were made using the carbon in two different granulometries against multi-resistant strains: Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. The adsorption tests were performed following a procedure adapted from Naka et al. [1]. In any case in parallel with the adsorption assays, the growth of the bacteria was also assessed.The results displayed at Figure 1 show that carbon AC allows a continue decrease of bacteria amount in the liquid media, despite the continuous increase of bacteria demonstrated by the blank experiment. The images displayed in Figure 2 (b) and (c) show the cells adherent to carbon, after 90 minutes of contact. These preliminary results allow us to conclude that activated carbon can be used to increase the removal efficiency of multi-resistant bacteria present in hospital wastewater. Acknowledgments The financial support of FCT to CQB (PEst-OE/QUI/UI0612/2013) is acknowledged. [1] K. Naka, S.T. Watarai, K. Inoue, Y. Kodama, K. Oguma, T.Yasuda, H.J. Kodama, 2001, Veter. Med. Science., 63, 281-285.
- Ginkgo biloba L. Leaf Extract Protects HepG2 Cells Against Paraquat-Induced Oxidative DNA DamagePublication . Silva, Amélia; Silva, Sandra; Soares, Jorge; Martins-Gomes, Carlos; Teixeira, João Paulo; Leal, Fernanda; Gaivão, IsabelGinkgo biloba L. leaf extracts and herbal infusions are used worldwide due to the health benefits that are attributed to its use, including anti-neoplastic, anti-aging, neuro-protection, antioxidant and others. The aim of this study was to evaluate the effect of an aqueous Ginkgo biloba extract on HepG2 cell viability, genotoxicity and DNA protection against paraquat-induced oxidative damage. Exposure to paraquat (PQ), over 24 h incubation at 1.0 and 1.5 µM, did not significantly reduce cell viability but induced concentration and time-dependent oxidative DNA damage. Ginkgo biloba leaf extract produced dose-dependent cytotoxicity (IC50 = 540.8 ± 40.5 µg/mL at 24 h exposure), and short incubations (1 h) produced basal and oxidative DNA damage (>750 and 1500 µg/mL, respectively). However, lower concentrations (e.g., 75 µg/mL) of Ginkgo biloba leaf extract were not cytotoxic and reduced basal DNA damage, indicating a protective effect at incubations up to 4 h. On the other hand, longer incubations (24 h) induced oxidative DNA damage. Co-incubation of HepG2 cells for 4 h, with G. biloba leaf extract (75 µg/mL) and PQ (1.0 or 1.5 µM) significantly reduced PQ-induced oxidative DNA damage. In conclusion, the consumption of Ginkgo biloba leaf extract for long periods at high doses/concentrations is potentially toxic; however, low doses protect the cells against basal oxidative damage and against environmentally derived toxicants that induce oxidative DNA damage.