A novel nanoenzyme based on Fe3O4 nanoparticles@thionine-imprinted polydopamine for electrochemical biosensing

Here, a new nanoenzyme of Fe3O4 nanoparticles (NPs) magnetic molecularly imprinted polymers (MMIPs) was prepared by polymerizing dopamine on the Fe3O4NPs surface in the presence of templated thionine (Thi) for the first time. The results showed that uniform spherical and core-shell structured Fe3O4NPs MMIPs which were about 600 nm in diameter were successfully formed and the imprinting sites improved the selectivity of Fe3O4NPs MMIPs greatly. The as-prepared Fe3O4NPs MMIPs could catalyze the reduction of Thi selectively, which could be enhanced by H2O2 owing to the peroxidase-like activity of Fe3O4NPs. Accordingly, a highly selective and sensitive H2O2 electrochemical biosensor was proposed based on the Fe3O4NPs MMIPs-modified glassy carbon electrode. The electrochemical biosensor based on the Fe3O4NPs MMIPs nanoenzyme exhibited low detection limit of 1.58 nM and high selectivity. Since acetylthiocholine chloride (AChl) could be hydrolyzed into choline with the help of acetylcholinesterase (AChE) and simultaneously the choline oxidase (ChOx) could reduce choline into betaine accompanied by the production of H2O2, the proposed electrochemical H2O2 biosensor could be further used to detect AChl, AChE and ChOx. The results also exhibited wide linear range (2.85–160 μM for AChl, 0.53–20000 ng mL−1 for AChE and 22.76–400 ng mL−1 for ChOx), low detection limit (0.86 μM for AChl, 0.16 ng mL−1 for AChE and 6.83 ng mL−1 for ChOx) and high selectivity. Therefore, the Fe3O4NPs MMIPs should be a promising nanoenzyme for electrochemical biosensors.