Examinando por Autor "Gallardo, C."

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    Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories
    (BIOMED CENTRAL, 2016) Plaza, D. O.; Gallardo, C.; Straub, Y. D.; Bravo, D.; Pérez‑Donoso, J. M.
    Background: Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria. Results: In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles. Conclusions: Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.
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    Ítem
    Eugenol and its Synthetic Analogues Inhibit Cell Growth of Human Cancer Cells (Part I)
    (Sociedad Brasilera de Química, 2008) Carrasco, H.; Espinoza, L.; Cardile, V.; Gallardo, C.; Cardona, W.; Lombardo, L.; Catálan, K.; Cuellar, M.; Russo, A.
    Eugenol (4-allyl-2-methoxyphenol) (1) has been reported to possess antioxidant and anticancer properties. In an attempt to enhance intrinsic activity of this natural compound, some derivatives were synthesized. Eugenol was extracted from cloves oil and further, the eugenol analogues (2-6) were obtained through acetylation and nitration reactions. Eugenol (1) and its analogues (2-6) were examined by in vitro model of cancer using two human cancer cell lines: DU-145 (androgen-insensitive prostate cancer cells) and KB (oral squamous carcinoma cells). Cell viability, by tetrazolium salts assay, was measured. Lactic dehydrogenase (LDH) release was also investigated to evaluate the presence of cell toxicity as a result of cell disruption, subsequent to membrane rupture. In the examined cancer cells, all compounds showed cell-growth inhibition activity. The obtained results demonstrate that the compounds 5-allyl-3-nitrobenzene-1,2-diol (3) and 4-allyl-2-methoxy-5-nitrophenyl acetate (5) were significantly (p < 0,001) more active than eugenol, with IC50 values in DU-145 cells of 19.02 x 10-6 and 21.5 × 10-6 mol L-1, respectively, and in KB cells of 18.11 × 10-6 and 21.26 × 10-6 mol L-1, respectively, suggesting that the presence of nitro and hydroxyl groups could be important in the activity of these compounds. In addition, our results seem to indicate that apoptotic cell demise appears to be induced in KB and DU-145 cells. In fact, in our experimental conditions, no statistically significant increase in LDH release was observed in cancer cells treated with eugenol and its analogues.