A long-wavelength tetraphenylethylene-derived fluorescent probe for sensitive detection of heparin and protamine

Heparin and protamine are vital biomacromolecules extensively used in clinical settings, necessitating precise monitoring of their concentrations. In this study, a novel positively charged fluorescent probe was developed, derived from an aggregation-induced emission (AIE) luminogen, tetraphenylethylene (TPE), for the detection of heparin and protamine. The probe was designed by modifying TPE with a 4-methyl-1-(3-(trimethylammonio)propyl)pyridin-1-ium bromide moiety, which imparts enhanced water solubility and long-wavelength emission. The probe (TPE-PY-N) binds electrostatically to heparin, inducing a significant "turn-on" fluorescence response. It exhibits high selectivity and sensitivity, with a limit of detection (LOD) of 10.7 ng/mL for heparin in buffer solution. Subsequently, the addition of protamine displaces the probe molecules, leading to a "turn-off" emission. The probe's high selectivity and sensitivity position it as a promising tool for sensing heparin and protamine in buffer and highly diluted serum.