Examinando por Autor "Ulloa, G."

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    Biological phosphorylated molecules participate in the biomimetic and biological synthesis of cadmium sulphide quantum dots by promoting H2S release from cellular thiols
    (Royal Society of Chemistry, 2017-08) Venegas, F.A.; Saona, L.A.; Monrás, J.P.; Órdenes-Aenishanslins, N.; Giordana, M.F.; Ulloa, G.; Collao, B.; Bravo, D.; Pérez-Donoso, J.M.
    Developing methods with a low environmental impact for nanoparticle synthesis remains one of the greatest challenges in nanotechnology. In this context, biomimetic and biological methods have emerged as green chemistry alternatives, and also contribute to our understanding of how nanomaterials interact with cellular molecules. Here, we report a phosphate-dependent biomimetic method to synthesize of cadmium sulphide (CdS) QDs at low temperatures, physiological pH and aerobic conditions, using CdCl2 and thiols (l-cysteine, glutathione or mercaptosuccinic acid). Inorganic phosphate (Pi) and cellular phosphorylated intermediates such as adenosine monophosphate, glucose-6-phosphate, glycerol-2-phosphate and fructose-1,6-biphosphate, can trigger CdS QDs synthesis. The produced QDs are cubic phase nanocrystals with a tunable fluorescence (450-700 nm), small size (4-12 nm), and are composed of thiols and Pi. In CdS synthesis, the importance of the phosphate is related to its capacity to release H2S from thiols, a phenomenon associated with its base-properties. Based on the biomimetic method, we developed a Pi-based procedure to synthesize CdS QDs in Escherichia coli. As in the biomimetic procedure, Pi favors QDs-biosynthesis not only by mediating biological generation of H2S, but also by improving Cd2+ cellular uptake. A role for phosphates in the cellular interaction and green synthesis of metal QDs is discussed.
  • Miniatura
    Ítem
    Phosphate favors the biosynthesis of CdS quantum dots in Acidithiobacillus thiooxidans ATCC 19703 by improving metal uptake and tolerance
    (Frontiers Media, 2018-02) Ulloa, G.; Quezada, C.P.; Araneda, M.; Escobar, B.; Fuentes, E.; Alvarez, S.A.; Castro, M.; Bruna, N.; Espinoza-González, R.; Bravo, D.; Pérez-Donoso, J.M.
    Recently, we reported the production of Cadmium sulfide (CdS) fluorescent semiconductor nanoparticles (quantum dots, QDs) by acidophilic bacteria of the Acidithiobacillus genus. Here, we report that the addition of inorganic phosphate to Acidithiobacillus thiooxidans ATCC 19703 cultures favors the biosynthesis of CdS QDs at acidic conditions (pH 3.5). The effect of pH, phosphate and cadmium concentrations on QDs biosynthesis was studied by using Response Surface Methodology (RSM), a multivariate technique for analytical optimization scarcely used in microbiological studies to date. To address how phosphate affects intracellular biosynthesis of CdS QDs, the effect of inorganic phosphate on bacterial cadmium-uptake was evaluated. By measuring intracellular levels of cadmium we determined that phosphate influences the capacity of cells to incorporate this metal. A relation between cadmium tolerance and phosphate concentrations was also determined, suggesting that phosphate participates in the adaptation of bacteria to toxic levels of this metal. In addition, QDs-biosynthesis was also favored by the degradation of intracellular polyphosphates. Altogether, our results indicate that phosphate contributes to A. thiooxidans CdS QDs biosynthesis by influencing cadmium uptake and cadmium tolerance. These QDs may also be acting as a nucleation point for QDs formation at acidic pH. This is the first study reporting the effect of phosphates on QDs biosynthesis and describes a new cadmium-response pathway present in A. thiooxidans and most probably in other bacterial species.