RESUMO
This contribution describes a novel method for the detection of trace amounts of trinitrotoluene (TNT) using a cluster of hexamolybdenum with general formula [Mo6Cl14]2-. The molybdenum cluster was characterized by UV-visible, FT-IR, and fluorescence techniques, and the synthesis was efficient and reproducible. The evaluation of the molybdenum cluster by TNT detection was perfomed by fluoresecent measurements, and the results were interpreted by the Stern-Volmer equation, obtaining K SV values of 2.9 × 105 and 1.6 × 104 M-1 in different concentration ranges. Further, the results suggest that at TNT concentrations higher than 4 × 10-5 mM (0.01 mg L-1) it is possible to measure the quenching of the cluster fluorescence. The DFT calculations indicate that the contribution of the TNT in the active lowest unoccupied molecular orbitals that are involved in the higher intensity transitions in the complex cluster-TNT are significant. This situation differs from all the luminescent [M6X8L6]2- clusters (M = Mo; X = facial bridging ligand, and L = labile axial ligands), where most of the closely spaced excited states are located in the {M6X8} q+ core. Thus, the TNT switches off the cluster luminescence. The approach using a [Mo6Cl14]2--based fluorescence sensor has the potential to be a sensing technology for the detection of nitroaromatic explosives.
RESUMO
In this study we evaluated if zebrafish larvae can be colonized by human gut microorganisms. We tested two strategies: (1) through transplantation of a human fecal microbiota and (2) by successively transplanting aerotolerant anaerobic microorganisms, similar to the colonization in the human intestine during early life. We used conventionally raised zebrafish larvae harboring their own aerobic microbiota to improve the colonization of anaerobic microorganisms. The results showed with the fecal transplant, that some members of the human gut microbiota were transferred to larvae. Bacillus, Roseburia, Prevotella, Oscillospira, one unclassified genus of the family Ruminococcaceae and Enterobacteriaceae were detected in 3 days post fertilization (dpf) larvae; however only Bacillus persisted to 7 dpf. Successive inoculation of Lactobacillus, Bifidobacterium and Clostridioides did not improve their colonization, compared to individual inoculation of each bacterial species. Interestingly, the sporulating bacteria Bacillus clausii and Clostridioides difficile were the most persistent microorganisms. Their endospores persisted at least 5 days after inoculating 3 dpf larvae. However, when 5 dpf larvae were inoculated, the proportion of vegetative cells in larvae increased, revealing proliferation of the inoculated bacteria and better colonization of the host. In conclusion, these results suggest that it is feasible to colonize zebrafish larvae with some human bacteria, such as C. difficile and Bacillus and open an interesting area to study interactions between these microorganisms and the host.
