Colorimetric detection of heparin with high sensitivity based on the aggregation of gold nanoparticles induced by polymer nanoparticles

Herein, a new colorimetric strategy based on polymer nanoparticles (PNPs) and Au nanoparticles (AuNPs) is developed to detect heparin (Hep). The cationic PNPs can directly induce the aggregation of AuNPs, which are stabilized by negatively charged coating of citrate ions, and hence the absorption peak of AuNPs moves to 675 nm corresponding with a color change from wine red to blue. However, the negatively charged Hep competes with AuNPs and binds to PNPs, hindering the interaction between PNPs and AuNPs. As a result, the absorption band of AuNPs blue shifts and the color turns to red again. The reaction can be completed within 10 min, and the color variation produced by 150 nM of Hep can be distinguished by the naked eye. In addition, this strategy also shows good selectivity and sensitivity, and the linear range of Hep is from 10 to 400 nM with detection limit of 2.5 nM. Finally, this colorimetric assay has been applied to measure Hep in Hep sodium injection and human serum samples with satisfactory recoveries.