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

Here, a new nanoenzyme of Fe 3 O 4 nanoparticles (NPs) magnetic molecularly imprinted polymers (MMIPs) was prepared by polymerizing dopamine on the Fe 3 O 4 NPs surface in the presence of templated thionine (Thi) for the first time. The results showed that uniform spherical and core-shell structured Fe 3 O 4 NPs MMIPs which were about 600   nm in diameter were successfully formed and the imprinting sites improved the selectivity of Fe 3 O 4 NPs MMIPs greatly. The as-prepared Fe 3 O 4 NPs MMIPs could catalyze the reduction of Thi selectively, which could be enhanced by H 2 O 2 owing to the peroxidase-like activity of Fe 3 O 4 NPs. Accordingly, a highly selective and sensitive H 2 O 2 electrochemical biosensor was proposed based on the Fe 3 O 4 NPs MMIPs-modified glassy carbon electrode. The electrochemical biosensor based on the Fe 3 O 4 NPs 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 H 2 O 2 , the proposed electrochemical H 2 O 2 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 Fe 3 O 4 NPs MMIPs should be a promising nanoenzyme for electrochemical biosensors.