A visualized colorimetric detection strategy for heparin in serum using a metal-free polymer nanozyme

A metal-free polymer nanozyme has been developed for the first time simply via the one-pot covalent reaction of hyperbranched polyethyleneimine (PEI) and redox dihydroxybenzaldehyde (DHB). The yielded PEI-DHB nanoparticles could display the peroxidase-like catalysis activity, so as to act as the metal-free nanozyme in catalyzing the chromogenic reactions of 3,3',5,5'-tetramethylbenzidine and H2O2. More interestingly, the catalysis activity of the polymer nanozymes could be specifically inhibited by heparin oppositely charged. A facile visualized colorimetric method was thereby developed for sensing heparin through combining the specific catalysis and electrostatic attraction of PEI-DHB nanozyme. It was found that the developed colorimetric method can enable the detection of heparin in serum over the linear concentration range of 0.050-1.0 mu M, promising the wide applications for the detection of heparin in the clinical laboratory for the disease diagnostics and pharmacological monitoring. More importantly, such a green synthesis method may be tailored for fabricating various metal-free polymer nanozymes for the wide catalysis applications.