Turn-on visible and ratiometric near-infrared fluorescent probes for distinction endogenous esterases and chymotrypsins in live cells

Abstract

Esterase is an enzyme that catalyzes the hydrolysis of esters and is widely used to regulate various metabolic functions of organisms. However, chymotrypsin, which also has hydrolyzed ester bond, may interfere with esterase to play an important role in the organism. A series of visible fluorescent probes based on rhodamine (RHO) act as fluorophore and near-infrared fluorescent probes based on hemicyanine (CY-OH) act as fluorophore with 4-phenylpropionyl chloride (1), n-butyryl chloride (2), 4-bromobutyryl chloride (3) or 2-thiophene acetyl chloride (4) act as detection groups for distinguishing between esterase and chymotrypsin in live cells were designed and synthesis (RHO-n and CY-OH-n (n=1-4)). These probes show good stability and weak red fluorescence. Visible fluorescent probes RHO-n have fluorescence-enhancing (weak red fluorescence to strong red fluorescence) response to esterase in 20 min and chymotrypsin in 140 min (RHO-1); while near-infrared fluorescent probes CY-OH-n have ratiometric fluorescent (red-shift from ∼657 nm to ∼703 nm) response to esterase in 0.83 min and chymotrypsin in 15 min (CY-OH-1). As far as we know, these fluorescent probes are the first to distinguish between esterase and chymotrypsin. Moreover, these eight fluorescent probes have also been applied to live cell imaging and are expected to be further practically applied in clinical medical testing.