A supramolecular host–guest complex for heparin binding and sensing†
Heparin is an anionic polysaccharide widely used in clinics as an anticoagulant. However, heparin usage requires an antidote and sensors for safe operation during and after surgeries. In this study, a host–guest complex capable of selective heparin binding and sensing is presented. Heparin binding affinity was studied in solution with a variety of polycationic macrocyclic hosts, a pillararene and multiple resorcinarenes, by dynamic light scattering, dye displacement assay, isothermal titration calorimetry, and anti-Xa assay. The measurements reveal the significant importance of multivalency in electrostatic host–heparin binding in competitive, application-relevant media. Additionally, to monitor the heparin concentration, a host–guest indicator displacement assay was performed by following the free and bound state of the methyl orange dye in UV-Vis spectroscopic experiments. Furthermore, this colorimetric sensing based on the tertiary host–guest–heparin supramolecular assembly was utilized in the construction of a calibration curve in a range of blood plasma concentrations.