A colorimetric and fluorometric based dual readout approach for effective heparin sensing

Devising fluorescence-based turn-on probes for the specific and sensitive detection of Heparin is of utmost clinical importance. In this contribution, we have identified a molecular rotor based asymmetric cyanine probe, thiazole orange (TO), which enables an efficient colorimetric and fluorimetric detection of Heparin. TO undergoes the formation of emissive H-aggregates upon interaction with Heparin that display an impressive emission enhancement of ~22 fold together with drastic changes in the absorption spectra that yields a prominent colour change in the solution from orange to yellow. These seldom reported emissive H-aggregates of TO, serve as an efficient platform for Heparin detection with a LOD of 19 nM, fluorometrically and 34 nM, colorimetrically. The TO-Heparin complex is also accompanied by a large change in the excited-state lifetime. The TO-Heparin complex has been further utilized for the detection of Protamine, which is the only medically affirmed antitoxin of Heparin. Overall, our sensing system offers several advantages, such as, simple, dual read-out, economic and specific detection of Heparin with longer excitation and emission wavelength, rapid naked eye detection and utilizes an in-expensive commercially available fluoprophore, TO. Most importantly, our sensing system also displays a good performance in the biologically complex human serum matrix.