RESUMO
The vast application of fluorescent semiconductor nanoparticles (NPs) or quantum dots (QDs) has prompted the development of new, cheap and safer methods that allow generating QDs with improved biocompatibility. In this context, green or biological QDs production represents a still unexplored area. This work reports the intracellular CdTe QDs biosynthesis in bacteria. Escherichia coli overexpressing the gshA gene, involved in glutathione (GSH) biosynthesis, was used to produce CdTe QDs. Cells exhibited higher reduced thiols, GSH and Cd/Te contents that allow generating fluorescent intracellular NP-like structures when exposed to CdCl(2) and K(2)TeO(3). Fluorescence microscopy revealed that QDs-producing cells accumulate defined structures of various colors, suggesting the production of differently-sized NPs. Purified fluorescent NPs exhibited structural and spectroscopic properties characteristic of CdTe QDs, as size and absorption/emission spectra. Elemental analysis confirmed that biosynthesized QDs were formed by Cd and Te with Cd/Te ratios expected for CdTe QDs. Finally, fluorescent properties of QDs-producing cells, such as color and intensity, were improved by temperature control and the use of reducing buffers.
Assuntos
Compostos de Cádmio/metabolismo , Escherichia coli/metabolismo , Glutationa/metabolismo , Nanopartículas/química , Telúrio/metabolismo , Citratos/farmacologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Genes Bacterianos/genética , Microscopia de Fluorescência , Nanopartículas/ultraestrutura , Tamanho da Partícula , Pontos Quânticos , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Difração de Raios XRESUMO
A fast, simple, and reliable chemical method for tellurite quantification is described. The procedure is based on the NaBH(4)-mediated reduction of TeO(3)(2-) followed by the spectrophotometric determination of elemental tellurium in solution. The method is highly reproducible, is stable at different pH values, and exhibits linearity over a broad range of tellurite concentrations.