Rapid colorimetric detection of the anticoagulant heparin based on an etching mechanism using I- responsive Cu-Au NPs

Heparin, as a glycosaminoglycan with multiple physiological functions, performs important roles in clinical practice. The core function of heparin is its anticoagulant effect, which is commonly used to prevent and treat thrombotic diseases. However, when the heparin content in human blood exceeds the standard, it can result in thrombocytopenia, thereby posing threat to human health. Therefore, rapid, sensitive and accurate detection of heparin is of great practical importance in assessing the anticoagulant effect, prevention of thrombophilia, guidance on personalized medication, and avoiding side effects caused by excessive use. A new colorimetric sensor for detecting the anticoagulant heparin is introduced in this work. The sensor is low cost, fast, and simple. In the absence of heparin, protamine protects copper‑gold nanoparticles from the etching of iodide ions through electrostatic interaction, and the solution's color and spectral properties remain essentially the same as those of pure copper‑gold nanoparticles. When heparin is present, due to the strong electrostatic adsorption between heparin and protamine, protamine preferentially binds heparin and forms a complex. Cu-Au NPs are not protected and are etched into spherical Au NPs by iodide ions. The solution's color shifted from dark gray and purple to pink, thus colorimetric detection of heparin is realized rapidly based on the etching mechanism. The detection time is 15 min, and the detection limit is as low as 1 ng/mL. Compared with HPLC detection method, the colorimetric detection of heparin in serum samples has the recovery rate of 98.8–108.8 %, which has good prospects for application.