Positive-Charge-Based\nSmall Molecule Dyes for Gut\nMicrobiota Fluorescent Imaging

As one of the research hotspots in recent years, gut\nmicrobiota\nhave been proven to be closely related to host metabolism, nutrient\nabsorption, and immune regulation. However, there are still many urgent\nissues in the research of gut microbiota, such as the localization\nand tracking of gut microbiota. In this research, two new fluorescent\nprobes, EF and 6F, were developed by optimizing the structure of the\npositron salt small molecule probe F16. <i>In vitro</i> labeling\nexperiments showed that EF and 6F can quickly label Gram-positive\nbacteria, <i>Staphylococcus aureus</i> and <i>Lactobacillus\nreuteri</i>, as well as Gram-negative bacteria, <i>Escherichia\ncoli</i> and <i>Salmonella pullorum</i>. Meanwhile,\nEF and 6F have little bacterial toxicity and are used at a maximum\nconcentration of 200 μM. Compared with EF, 6F has better hydrophilicity\nand stronger fluorescence characteristics in aqueous solutions, making\nit more suitable for imaging within gut microbiota populations. The\nresults of <i>in vivo</i> imaging experiments indicate that\nEF and 6F can label and image the intestinal microbiota colonized\nby the mouse intestinal mucosal epithelium without causing any damage\nto intestinal tissue. Compared with commercially available MitoTracker\ndyes and fluorescein 5-isothiocyanate (FITC) dyes, EF and 6F exhibit\nbetter biocompatibility. Therefore, the compounds EF and 6F synthesized\nin this study are novel small molecule probes suitable for imaging\ngut microbiota, providing a better probe selection for exploring complex\ngut microbiota.