A polyadenosine-coralyne complex as a novel fluorescent probe for the sensitive and selective detection of heparin in plasma

This study presents the development of a simple, label-free, sensitive, and selective detection system for heparin based on the use of a complex of 20-repeat adenosine (A(20)) and coralyne. Coralyne emits relatively weak fluorescence in an aqueous solution. In the presence of A(20), coralyne molecules complexed with A(20) through A(2)-coralyne-A(2) coordination. An increase in the fluorescence of coralyne was observed because coralyne remained separate from water in the hydrophobic environment of the folded A(20). The presence of heparin and the formation of the coralyne-heparin complex caused coralyne to be removed from the A(20)-corlayne complex. Because heparin promoted coralyne dimerization, the fluorescence of coralyne decreased as a function of the concentration of added heparin. This detection method is effective because the electrostatic attraction between heparin and coralyne is substantially stronger than the coordination between A(20) and coralyne in a 4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid (HEPES) buffer at pH 7.0. Under optimal conditions (5 mu M coralyne, 1 mu M poly A(20), and 10 mM HEPES), this probe exhibited high selectivity ( > 90-fold) toward heparin over hyaluronic acid and chondroitin sulfate. The probe's detection limit for heparin was determined to be 4 nM (75 ng/mL) at a signal-to-noise ratio of 3. This study validates the practicality of using the A(20)-corlayne complex to determine the concentration of heparin in plasma. (c) 2014 Elsevier B.V. All rights reserved.