A simple bacteria-mediated staining strategy: Ultrafast and high-resolution live-cell imaging with wash-free carbon dots.

Nucleus labeling is significant to dynamic monitor many physiological and pathophysiological processes. In the current work, a nuclear-targeted carbon dots (named as mf-CDs) was synthesized from m-phenylenediamine and folic acid through the hydrothermal method. The prepared mf-CDs were water-soluble and could specifically "light up" the nucleus whether it's normal cells or cancer cells. Remarkably, this staining process is both ultrafast and wash-free. The universality of mf-CDs was demonstrated through successful imaging across diverse cell systems. Including bacterial species such as Escherichia coli and Nitrogen fixing bacteria, fungi like Rhizoctonia solani and Saccharomyces cerevisiae, as well as plant cells from onion epidermis. Notably, excellent nuclear specificity was observed in Saccharomyces cerevisiae and onion epidermal cells. More interestingly, the Escherichia coli or Saccharomyces cerevisiae preloaded with low concentration (3.0 μg/mL) of mf-CDs effectively stained live HepG2 cells, high-resolution images fluorescence image was obtained within 4 min. Revealing that mf-CDs could ultrafast label the living cells under extremely low concentration conditions. To the best of our knowledge, this novel bacteria-mediated staining process has not been previously reported. The current work advances ultralow-concentration CDs bioimaging and pioneers microbial-mediated cellular analysis, offering new tools to study nanoparticle-cell interactions.