Browsing by Author "Osorio Roman, Igor O."
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- ItemBiomimetic, Mild Chemical Synthesis of CdTe-GSH Quantum Dots with Improved Biocompatibility(PUBLIC LIBRARY SCIENCE, 2012) Perez Donoso, Jose M.; Monras, Juan P.; Bravo, Denisse; Aguirre, Adam; Quest, Andrew F.; Osorio Roman, Igor O.; Aroca, Ricardo F.; Chasteen, Thomas G.; Vasquez, Claudio C.Multiple applications of nanotechnology, especially those involving highly fluorescent nanoparticles (NPs) or quantum dots (QDs) have stimulated the research to develop simple, rapid and environmentally friendly protocols for synthesizing NPs exhibiting novel properties and increased biocompatibility. In this study, a simple protocol for the chemical synthesis of glutathione (GSH)-capped CdTe QDs (CdTe-GSH) resembling conditions found in biological systems is described. Using only CdCl2, K2TeO3 and GSH, highly fluorescent QDs were obtained under pH, temperature, buffer and oxygen conditions that allow microorganisms growth. These CdTe-GSH NPs displayed similar size, chemical composition, absorbance and fluorescence spectra and quantum yields as QDs synthesized using more complicated and expensive methods. CdTe QDs were not freely incorporated into eukaryotic cells thus favoring their biocompatibility and potential applications in biomedicine. In addition, NPs entry was facilitated by lipofectamine, resulting in intracellular fluorescence and a slight increase in cell death by necrosis. Toxicity of the as prepared CdTe QDs was lower than that observed with QDs produced by other chemical methods, probably as consequence of decreased levels of Cd+2 and higher amounts of GSH. We present here the simplest, fast and economical method for CdTe QDs synthesis described to date. Also, this biomimetic protocol favors NPs biocompatibility and helps to establish the basis for the development of new, "greener" methods to synthesize cadmium-containing QDs.
- ItemEnhanced Glutathione Content Allows the In Vivo Synthesis of Fluorescent CdTe Nanoparticles by Escherichia coli(PUBLIC LIBRARY SCIENCE, 2012) Monras, Juan P.; Diaz, Victor; Bravo, Denisse; Montes, Rebecca A.; Chasteen, Thomas G.; Osorio Roman, Igor O.; Vasquez, Claudio C.; Perez Donoso, Jose M.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 CdCl2 and K2TeO3. 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.
- ItemSurface-Enhanced Spectra on D-Gluconic Acid Coated Silver Nanoparticles(SAGE PUBLICATIONS INC, 2011) Osorio Roman, Igor O.; Ortega Vasquez, Victoria; Vargas C, Victor; Aroca, Ricardo F.Coated silver (Ag) colloids synthesized with D-glucose permit the observation of surface-enhanced fluorescence (SEF) and surface-enhanced resonance Raman scattering (SERRS) of the rhodamine B (RhB) molecule. The organic coating formed during the synthesis of the Ag nanostructures was identified by its surface-enhanced Raman scattering (SERS) spectrum as D-gluconic acid. The RhB molecule is used to exemplify the distance dependence of SEF and SERRS on the coated Ag nanostructures. The fluorescence enhancement factor for RhB on D-gluconic acid coated silver nanoparticles was determined experimentally and estimated using a simple model. Further support for the plasmon enhancement is obtained from the fact that the measured fluorescence lifetime of RhB on the silver coated with D-gluconic acid is shorter than that found on a glass surface. A very modest enhancement factor is obtained, as expected for very short distance between RhB and the metal surface. Given the very thin metal fluorophore separation, estimated from the size of the D-gluconic acid, the energy transfer or fluorescence quenching is still efficient and the SEF enhancement is just overcoming the energy transfer. Therefore, both SEF and SERRS are observed. Notably, the aggregation of coated nanoparticles also increases the enhancement factor for SEF.
- ItemVibrational spectroscopy characterization and anticoagulant activity of a sulfated polysaccharide from sea cucumber Athyonidium chilensis(ELSEVIER SCI LTD, 2012) Matsuhiro, Betty; Osorio Roman, Igor O.; Torres, RodrigoExtraction of Athyonidium chilensis body wall afforded a light brown powder in 4.2% yield which was fractionated by ion-exchange chromatography. The main fraction F1 contained glucuronic acid, galactosamine and fucose in a molar ratio of 1.0:1.1:1.1, and 32.9% of sulfate group. The second derivative FT-IR spectroscopy and Surface-enhanced Raman scattering (SERS) give more information than the normal IR and Raman spectroscopies. The broad band in the normal FT-IR spectrum of F1 at 850.6 cm(-1) assigned to sulfate group was resolved in the second derivative spectrum into three bands at 856.4 cm(-1), 837.4 cm(-1) and 818.6 cm(-1) assigned to sulfate group attached to axial C4 and equatorial C2 and C6, respectively, in glycosidic residues. The most important bands in SERS of F1, but not observed in Raman spectrum are bands at 1648 cm(-1) (nu C=O), 1377 cm(-1) (delta C-H) assigned to methyl group of N-acetyl group, at 1173 cm(-1) and at 956.2 cm(-1) (nu C-O-C) of glycosidic linkage: and bands at 925.5 cm(-1) and 890.4 cm(-1) (delta C-1-H) assigned to a and beta anomeric configurations of glycosidic residues, respectively. By NMR studies, glycosidic linkages and sulfation pattern of F1 was confirmed. Results obtained indicated that fraction F1 is chondroitin 4,6-disulfate substituted at position O-3 of glucuronic acid by partially 2,4-disulfated alpha-fucopyranosyl residues. Moreover, the anticogulant activity, measure in APTT of F1 showed at low concentration, a good correlation with heparin. (C) 2012 Elsevier Ltd. All rights reserved.