pH-sensitive carbon dots for the visualization of regulation of intracellular pH inside living pathogenic fungal cells

In this paper, the pH-sensitive carbon dots were synthesized by simple one-pot hydrothermal treatment of threonine. The fluorescence of the as-synthesized carbon dots was featured by pH dependence, with the intensity decreasing as pH increases. The carbon dots can be readily internalized into plant pathogenic fungal cells for imaging with dose dependence. Moreover, intracellular pH regulation, a kind of physiological functions of living fungal cells, was visually expressed as the variation of fluorescence intensity of the internalized carbon dots. A transient reduction of the intracellular pH tightly regulated by living fungal cells under basic external condition can be presented as a gradual increase in fluorescence intensity of the carbon dots. On the contrary, the fluorescence of the carbon dots distributed in apple tissue infected by the fungal cells was soon quenched by the basic buffer because there was no intracellular pH regulation in the dead cells.