Spectroscopic behavior and intracellular application of a highly sensitive UV-fluorescence double ratio probe based on water-soluble indole for detection acid pH

Acidic pH is an important physiological parameter in environment and biological systems. Thus, designing a probe ( Hcy-F ) with good characters to monitor acidic pH is really important. Herein, a small molecular water-soluble probe is designed based on indole with high selectivity and sensitivity for detection the acidic pH in aqueous solution and living cells. When pH variation of aqueous is detected by probe, an obvious ratiometric and good linear response behavior are found in UV–vis absorption spectrum (R 2  = 0.9973, A 434 nm / A 371 nm  = 6.9929–4.2231 pH) and fluorescence emission spectrum (R 2  = 0.9987, I 571 nm / I 514 nm  = 7.2935–2.981 pH), which further proved the feasibility of Hcy-F to monitor the change of acidic pH in aqueous, respectively. Furthermore, Hcy-F is successfully applied for monitoring pH variation in living cells in dual channels (green and red) with higher cell survival rate, indicating the probe has great potential for pH imaging in biological applications .