Visualizing Semipermeability of Cell Membrane by a pH-responsive Ratiometric AIEgen

In clinical chemotherapy, some basic drugs cannot enter the hydrophobic cell membrane because of ionization in acidic tumor microenvironment, a phenomenon known as ion trapping. In this study, we developed a method to visualize this ion trapping phenomenon by utilizing a pH-responsive ratiometric AIEgen, dihydro berberine (dhBBR). By observing the intracellular fluorescence of dhBBR, we found that non-ionized dhBBR can enter cells easier than ionized forms, which is in accordance with the concept of ion trapping. In addition, dhBBR shows superior anti-photobleaching ability than Curcumin thanks to its AIE property. These results suggest that dhBBR can serve as a bioprobe for ion trapping.