Flower-like ZIF-8 enhance the peroxidase-like activity of nanoenzymes at neutral pH for detection of heparin and protamine.

The peroxide-like catalytic activity of gold nanoclusters (Au–NCs) is very low under physiological conditions (pH 7.4), which greatly limits its biological detection applications. A new nanoenzyme platform was constructed by self-assembly of Au–NCs and ZIF-8/CQDs. It was found that heparin can significantly promote the peroxidase-like activity of Au–NCs on the nanoenzyme platform at pH 7.4. In the presence of H 2 O 2 , the catalytic activity of Au–NCs on the nanoenzyme platform for TMB increased nearly 50 times. Based on this phenomenon, a colorimetric method was developed to determine heparin in the range of 0.0185–9.25 U/mL, with a detection limit of 0.0027 U/mL. When protamine is introduced, heparin and protamine take the lead in specific binding due to antagonism, which makes heparin unable to adsorb on the surface of ZIF-8/CQDS, thus inhibiting the enhancement of the catalytic activity of Au–NCs. Based on this phenomenon, a colorimetric method was developed to determine protamine in the range of 0.01–0.5 μg/mL, with a detection limit of 0.003 μg/mL. Therefore, this method provides a new idea for the visual detection of heparin and protamine under physiological conditions. [Display omitted] •A new nanoenzyme platform is constructed by self-assembly of Au–NCs and ZIF-8/CQDs. •ZIF-8/CQDs is used as nanoenzyme platform with the peroxidase-like activity of Au–NCs to detect heparin and protamine. •This enhancement signal change of TMB to oxTMB is used as the basic detection condition for heparin with LOD of 0.01 μM. [ABSTRACT FROM AUTHOR]