Fabrication of tunable microreactor with enzyme modified magnetic nanoparticles for microfluidic electrochemical detection of glucose.

A microfluidic device was designed for amperometric determination of glucose by packing enzyme modified magnetic nanoparticles (MNPs) in its microchannel as an enzyme microreactor. Glucose oxidase was covalently attached to the surface of MNPs and localized in the microchannel by the help of an external magnetic field, leading to a tunable packing length. By changing the length of microreactor from 3 to 10mm, the performance for glucose detection was optimized. The optimal linear range to glucose was from 25 μM to 15 mM with a detection limit of 11 μM at a length of 6mm. The inter- and intra-day precisions for determination of 1.0mM glucose were 0.8% and 1.7%, respectively, and the device-to-device reproducibility was 95.6%. The enzyme reactor remained its 81% activity after three-week storage. Due to the advantages of the device and fracture sampling technique, serum samples could be directly sampled through the fracture to achieve baseline separation from ascorbic acid, and proteins in the samples did not interfere with the detection. This work provided a promising way for pretreatment-free determination of glucose with low cost and excellent performance.