Methylene blue based near-infrared fluorogenic probe for lighting up esterase activity and its application in biological imaging

In this work, a light-up near-infrared (NIR) fluorescence probe based on methylene blue was developed for the determination of esterase. Probe MB-Ace emits a significant NIR fluorescence at 691 nm while incubated with esterase, which facilitates us to accurately detect the activity of esterase in vitro and vivo. MB-Ace showed high sensitivity (with a detection limit of 5.2 ng/mL) and selectivity to esterase under the interference of various biomolecules. The results of biological imaging experiments showed that MB-Ace had cell membrane permeability and could be used to monitor esterase activity in Hep G2 cells. At the same time, MB-Ace also showed excellent imaging ability for esterase activity in a mice model. The above results reflect the application value of MB-Ace in the early diagnosis of liver cancer and image-guided tumor resection.