Aromaticity Engineering of Hybrid Cyanine Dyes for Metabolic Labeling and Bioorthogonal NIR-II Imaging of Gut Microbiota.

In the context of diabetes, host immune dysfunction and microcirculation damage significantly increase the susceptibility to bacterial infection. Therefore, the development of high-performance molecular imaging tools to dynamically track the migration and colonization of bacteria in deep living tissues is crucial to distinguish pathology-associated behavioral changes. In this study, we removed heteroatoms from the classical xanthene structure and effectively integrated the more planar and conjugated aminofluorene with the cyanine dye skeleton, enhancing the molecular aromaticity in the excited state, successfully constructing novel hybrid cyanine dyes IF with NIR-II emission, excellent photostability, and high brightness. Among them, the quantum yield of IFPy is 49 times higher than that of IFQ. Based on this, we developed a new NIR-II bioorthogonal probe to achieve specific imaging of intestinal bacteria and explored the influence of host environment of diabetes on the spatial distribution of intestinal bacteria. This work provides new insights into the design of fluorescent dyes and imaging of gut microbiota.