“Off-on” two-photon indolenine probes for pH bioimaging

Abstract

Fluorescence-based biosensors have become an indispensable tool in modern biology. These molecules can be used to monitor processes inside living cells and in real-time. The control of the pH is crucial in multiple biological process such as proliferation, apoptosis and defense. Therefore, the use of such pH probes are widespread in fluorescence microscopy. Recently, we have described a biosensor with excellent photophysical and suitable two-photon absorption (TPA) properties. This sensor allows the detection of hydroxyl radicals inside lysosomes. Based on this scaffold, we have designed, synthesized and characterized a new TPA fluorescent probe with an “off-on” response to different pH environments. These naphthalene-indolenine derivatives have a high synthetic versatility through affordable and efficient synthesis. The preliminary results suggest that this sensor has promising properties for detecting pH changes inside living cells.