Fluorescent probes sensitive to microenvironment have always been fascinating due to their tremendous advantages in tracking changes in the pathophysiological microenvironment and potential application in the early diagnosis of related diseases. In this study, a fluorescent luminogen, triphenylamine-thiophene-rhodanine (TPA-TRDN), with high sensitivity to changes in polarity and viscosity was designed and could be applied to detecting human serum albumin (HSA) in actual urine, as well as lipid droplets (LDs) in cells and in vivo with turn-on red emission. TPA-TRDN could selectively detect HSA with fast response (10 min), superior sensitivity (LOD 0.34 μg/mL, about 60-fold fluorescence enhancement), and wide detection range (0.00-0.30 mg/mL). The detection mechanism was demonstrated: TPA-TRDN encountered the hydrophobic IB domain of HSA, leading to the inhibition of the twisted intramolecular charge transfer (TICT) phenomenon and intramolecular rotation. Moreover, TPA-TRDN demonstrated satisfactory ability to identify cancer cells and noncancer cells by microenvironment-guided specific LD bioimaging. This evidence indicated that TPA-TRDN has promising application in the microenvironment-related biomedical field and clinical diagnosis.
Keywords: cell imaging; human serum albumin; in vivo imaging; lipid droplets; microenvironment-sensitive probe; twisted intramolecular charge transfer.