Visualizing semipermeability of the cell membrane using a pH-responsive ratiometric AIEgen

In clinical chemotherapy, some basic drugs cannot enter the hydrophobic cell membrane because of ionization in the 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 (<b>dhBBR</b>). By observing the intracellular fluorescence of <b>dhBBR</b>, we found that non-ionized <b>dhBBR</b> can enter cells more easily than ionized forms, which is in accordance with the concept of ion trapping. In addition, <b>dhBBR</b> shows superior anti-photobleaching ability to <i>Curcumin</i> thanks to its AIE properties. These results suggest that <b>dhBBR</b> can serve as a bioprobe for ion trapping.