Near-infrared-II fluorescent quantum dots for in vivo tracking of colonization dynamics of transplanted gut microbiota.

Faecal microbiota transplantation (FMT) represents a critical therapeutic strategy for diseases associated with gut microbiota dysbiosis, but effective real-time monitoring methods for the dynamic behaviour of transplanted microbiota in the recipient gut are lacking. This study constructed a bacterial labelling probe based on near-infrared-II (NIR-II) fluorescent quantum dots (QDs). Using Ag2Te QDs as the fluorescent core, a PLGA-PEG coating was applied to improve their water dispersibility and biocompatibility, while heparin functionalization endowed them with bacterial labelling capabilities. This probe exhibits excellent in vivo and in vitro biosafety and stable NIR-II fluorescence performance, enabling efficient fluorescent labelling of bacteria within the transplanted microbiota. Based on NIR-II in vivo fluorescence imaging technology, real-time dynamic monitoring of FMT transplanted microbiota in the mouse intestine was achieved, and it was revealed that it has a long-term retention characteristic only in the intestine of CDI mice. This study establishes an NIR-II fluorescence imaging strategy for dynamic tracking of the transplanted microbiota during FMT, with potential for investigating its in vivo dynamics.