BastosLab Publications
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PLOS ONE: Beetroot-Pigment-Derived Colorimetric Sensor for Detection of Calcium Dipicolinate in Bacterial Spores

PLOS ONE: Beetroot-Pigment-Derived Colorimetric Sensor for Detection of Calcium Dipicolinate in Bacterial Spores | BastosLab Publications | Scoop.it

In this proof-of-concept study, we describe the use of the main red beet pigment betanin for the quantification of calcium dipicolinate in bacterial spores, including Bacillus anthracis. In the presence of europium(III) ions, betanin is converted to a water-soluble, non-luminescent orange 1:1 complex with a stability constant of 1.4×10^5 L mol^–1. The addition of calcium dipicolinate, largely found in bacterial spores, changes the color of the aqueous solution of [Eu(Bn)+] from orange to magenta. The limit of detection (LOD) of calcium dipicolinate is around 2.0×10^–6 mol L^–1 and the LOD determined for both spores, B. cereus and B. anthracis, is (1.1±0.3)×10^6 spores mL^–1. This simple, green, fast and low cost colorimetric assay was selective for calcium dipicolinate when compared to several analogous compounds. The importance of this work relies on the potential use of betalains, raw natural pigments, as colorimetric sensors for biological applications.

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Food Chemistry (2012): A comparative study of the purification of betanin

Food Chemistry (2012): A comparative study of the purification of betanin | BastosLab Publications | Scoop.it

Betanin is a natural pigment with antioxidant properties used as a food colourant. This work describes the spectrophotometric and chromatographic quantification of betanin (2S/15S) and its epimer isobetanin (2S/15R) in fresh beetroot juice, food-grade beetroot powder and betanin standard diluted in dextrin. Absorption spectra of all three samples were deconvoluted using a mixed three-function model. Food-grade beetroot powder has the largest amount of violet-red impurities, probably formed during processing. The purification of betanin from these complex matrices was carried out by seven different methods. Ion exchange chromatography was the most efficient method for the purification of betanin from all samples; however, fractions contain high amounts of salt. Reversed-phase HPLC as well as reversed-phase column chromatography also produced good results at a much faster rate. The longer retention time of isobetanin when compared to betanin in reversed-phase conditions has been investigated by means of quantum-mechanical methods.

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EJOC (2012): Hydroxythiazole-Based Fluorescent Probes for Fluoride Ion Detection

EJOC (2012): Hydroxythiazole-Based Fluorescent Probes for Fluoride Ion Detection | BastosLab Publications | Scoop.it

This work describes the synthesis of five O-silyloxy-1,3-thiazoles and their use as fast-response “turn-on” probes for fluoride ion detection in polar aprotic solvents and in aqueous cetyltrimethylammonium bromide micellar medium. The fluoride-triggered deprotection of these silyl ethers results in ca. 180-nm shifts in the fluorescence emission wavelengths. All compounds are suitable for the detection of fluoride ions with a detection limit in DMSO of
10–7 mol L–1; derivatives containing a 2-pyridyl moiety in the thiazole system are more efficient than those with a 3- or 4-pyridyl moiety. Typical anionic interferents, such as acetate or chloride, are not detected by O-silyloxy-1,3-thiazoles, making these compounds very specific for fluoride.

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PLoS One (2013): A Nature-Inspired Betalainic Probe for Live-Cell Imaging of Plasmodium-Infected Erythrocytes

PLoS One (2013): A Nature-Inspired Betalainic Probe for Live-Cell Imaging of Plasmodium-Infected Erythrocytes | BastosLab Publications | Scoop.it

A model betalainic dye was semisynthesized from betanin, the magenta pigment of the red beet, and was effective for live-cell imaging of Plasmodium-infected red blood cells. This water-soluble fluorescent probe is photostable, excitable in the visible region and cell membrane-permeable, and its photophysical properties are not notably pH-sensitive. Fluorescence imaging microscopy of erythrocytes infected with Plasmodium falciparum, a causative agent of malaria in humans, showed that only the parasite was stained. Z-stacking analysis suggested that the probe accumulates proximal to the nucleus of the parasite. Indicaxanthin, one of the natural fluorescent betalains found in the petals of certain flowers, did not stain the parasite or the red blood cell.

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