Ratiometric Detection of Nanomolar Concentrations of Heparin in Serum and Plasma Samples Using a Fluorescent Chemosensor Based on Peptides

A peptidyl fluorescent chemosensor for heparin was synthesized by conjugating a pyrene fluorophore with the heparin-binding peptide. The fluorescent chemosensor (<b>Py12</b>; pyrene-RKRLQVQLSIRT) showed a highly sensitive ratiometric response to nanomolar concentrations of heparin in aqueous solutions at physiological pH by increasing excimer emission intensity at 500 nm with a concomitant decrease in monomer emission intensity at 400 nm. <b>Py12</b> showed a sensitive ratiometric response to heparin over a wide pH range (1.5 ≤ pH ≤ 11.5) and exhibited high selectivity for heparin compared to other biological competitors, such as hyaluronic acid and chondroitin sulfate. <b>Py12</b> sensitively and ratiometrically detected nanomolar concentrations of heparin in biologically relevant samples containing human serum and human plasma, respectively. The detection limit of <b>Py12</b> was 34 pM (<i>R</i>² = 0.997) for heparin in an aqueous buffer solutions containing 5% human serum and 33 pM (<i>R</i>² = 0.994) for heparin in aqueous buffer solutions containing 5% human plasma. <b>Py12</b> had sufficient sensitivity and selectivity for ratiometrically detecting a nanomolar concentration of heparin, indicating that the peptide-base chemosensor provides a potential tool for monitoring heparin levels in clinical plasma samples