Abstract
Bacterial extracellular polysaccharides (EPS) has a good heavy metal ion adsorption function and can be used in sewage treatment of heavy metal pollution. In this work, we develop a new, label-free, turn-on fluorescent sensor for detecting EPS adsorbed Hg2+. This approach is based on the conformational switch from G-quadruplex complex induced by fluorogenic dye Thioflavin T (ThT) to Hg2+ mediated T–Hg–T double-stranded DNA formation. By this method, Hg2+ in aqueous solution can be detected by fluorescence spectroscopy in the range of 5–1200 nM. The entire reaction and analysis of Hg2+ was performed in 10 min under optimal experimental conditions (1.4 μM ThT, 0.35 μM TBA, 1.2 μM Hg2+ and 10 min incubation time at 25℃, pH7.5). Then, we have utilized this facile approach to detect the adsorption properties of different EPS on Hg2+ with fluorescence spectrometry. These EPS were produced by the fermentation of Pseudoalteromonas sp. BAY, Bacillus sp. RS1, Mesonia sp. Hua40 and Bacillus sp3. SL7 respectively. The Hg2+ adsorption capacity of EPS is between 80.1 mg/g to 169.6 mg/g. Among them, the extracellular polysaccharides of Mesonia sp. Hua40 have the strongest Hg2+ adsorption capacity, about 169.6 mg/g. This method provides an effective detection technique to analyze Hg2+ adsorption capacity of EPS.
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