A near-infrared lysosomal pH probe based on rhodamine derivative

Abstract A near-infrared fluorescent probe (NRL) for lysosomal pH was presented by integrating 4-(2-aminoethyl)morpholine moiety, a lysosome-targetable group, into the rhodamine derivative. The addition of H+ led to significant fluorescence intensity increase at 739 nm, thus enabling it to monitor pH changes at weakly acidic pH. NRL showed negligible response to common species and short response time. Furthermore, the probe was successfully applied in living cells, and the results indicated that the probe could target lysosomes and detect lysosomal pH. We believe that NRL had great potential as a practical tool for lysosomal pH biology.