Carbon-Dot-Based Probe Designed to Detect Intracellular pH in Fungal Cells for Building Its Relationship with Intracellular Polysaccharide

It is difficult to quantitatively explain the effects of intracellular conditions on bioreactions in cells because direct measurements in cells are not easily achieved. In this work, a relationship between the biosynthesis of intracellular polysaccharide and intracellular pH inside fungal cells was established by quantitatively determining them using proper methods, respectively. A fluorescent ratiometric pH probe was designed and synthesized for the detection of intracellular pH by conjugating a pH-sensitive moiety and pH-insensitive carbon dots (CDs) into one system. The intracellular pH values and intracellular polysaccharide contents inside the mycelia of Pholiota adipose fungus incubated under different conditions were individually analyzed by the ratiometric pH probe and a phenol-sulfuric acid method. Thereafter, a relationship was established using the content of polysaccharide in mycelia as ordinates and intracellular pH values as abscissa. As can be seen from the relationship, intracellular pH in the range 7.10–7.25 inside Pholiota adipose mycelia is the most suitable condition for the biosynthesis of intracellular polysaccharide.