A novel peptide-based AIE probe for highly selective and ultrasensitive detection of heparin and its applications

Heparin is a highly sulfated linear glycosaminoglycan with anticoagulant properties, and its excessive use may lead to many diseases. Therefore, developing sensitive detection techniques for precise detection of heparin is of utmost importance. Herein, we reported a novel peptide-based fluorescent probe (TPE-GRGRG) based on tetraphenylethylene (TPE)-labeled pentapeptide (Gly-Arg-Gly-Arg-Gly-NH₂) for the highly selective and outstanding sensitive detection of heparin. TPE-GRGRG exhibited a large Stokes shift (132 nm) and typical aggregation-induced emission (AIE) characteristics in DMSO/H₂O binary mixtures. TPE-GRGRG demonstrated a significant enhancement of fluorescence intensity in the presence of heparin with a response time of under 30 s and the limit of detection (LOD) as low as 0.30 nM. A series of characterizations revealed that TPE-GRGRG and heparin formed nanoaggregates via electrostatic interactions, including fluorescence spectroscopy, UV-Vis, FTIR, CD, zeta potential, DLS measurements and fluorescence lifetime analyses, which in turn restricted the intramolecular rotation and triggered the fluorescence enhancement. TPE-GRGRG enabled heparin detection over a wide pH range and exhibited good biocompatibility, and was successfully applied to image heparin in living cells and zebrafish larvae. Furthermore, this study established detection platforms based on swab tests for visual qualitative analysis and smartphone RGB analysis, thereby achieving portable and visual heparin monitoring with the LOD of 0.93 μM. Finally, heparin detection was achieved in 0.1% fetal bovine serum with the LOD of 1.46 nM. TPE-GRGRG offers a reliable strategy for point-of-care testing of heparin, holding potential application value in clinical diagnosis and biosensing.