Dual-factor Synergistically Activated ESIPT-based Probe: Differential Fluorescence Signals to Simultaneously Detect α-Naphthyl Acetate and Acid α-Naphthyl Acetate Esterase.

α-Naphthyl acetate esterase () and acid α-naphthyl acetate esterase (), a class of special esterases, are important for lymphocyte typing and immunocompetence-monitoring. As such, the simultaneous detection of and has become a target to effectively improve the accuracy in lymphocyte typing. Therefore, we developed a dual-factor synergistically activated ESIPT-based probe () to detect and sensitively, rapidly, and simultaneously in a differential manner. exhibits differential fluorescence signal outputs toward small changes of and activities. displays a weak fluorescence signal at 392 nm over a pH range from 6.0 to 7.4. However, when it interacts with (0-25 U) at pH = 7.4, the fluorescence intensity at 392 nm enhanced linearly within 60 s (F/F0 = 0.042 C + 1.1, = 0.99). Furthermore, emits ratiometric fluorescence signals (F/F) for (0-25 U) at pH = 6.0 within 2.0 min, exhibiting a good linear relationship (F/F = 0.83C - 1.75, = 0.99). The differential fluorescence signals can be used to simultaneously detect the activities of and in solutions and complex living organisms. More importantly, based on the differential fluorescence signals toward and , T lymphocytes and B lymphocytes could be successfully typed and differentiated among nontyped lymphocytes, facilitating the real-time evaluation of their immune functions using flow cytometry. Hence, could be used for the ultrasensitive detection of the enzyme activities of and , the real-time precise typing of lymphocytes, and the monitoring of immunocompetence.