Magnetic Nanoparticles Modified with Carbon Nanotubes for Electrocatalytic Magnetoswitchable Biosensing Applications

A novel biosensor based on magnetic nanoparticles (MNPs) functionalized with tyrosinase in an operational synergy with a multiwalled carbon nanotube (MWCNT) network is developed. An on–off external magnetic field is applied to a screen‐printed electrode (SPE), which is used as a transducing platform. This enables an interesting on‐demand biosensing performance. The effect of each component on the response of the developed device is carefully evaluated; particularly interesting results are presented for the contributions of MNPs and carbon nanotubes. A tyrosinase‐based model biosensing approach is used, while a potential of −0.15 V versus Ag/AgCl for the electrochemical reduction of the enzyme products (quinone forms) onto the magnetoswitchable SPE/MNP/Tyr/MWCNT system is applied. The response of the biosensor to catechol is also evaluated; a limit of detection (signal to noise ratio (S/N) = 3) for catechol is found to be around 7.61 μM (S/N = 3) with a relative standard deviation (RSD) of 4.91% (n = 3). The developed device could open the door to a wide range of novel electrocatalytic and bioelectrocatalytic applications of magnetocontrolled redox enzymes. Furthermore, it could be used in miniaturized and portable biosensing systems, such as lab‐on‐a‐chip devices, in medical and environmental applications that have a restricted quantity of sample. Further applications could be envisaged for many other fields, such as external control of catalytic transformations in bioreactors, tailoring of reversible amperometric immunosensors, regeneration of enzyme‐biosensor electrodes, and external triggering of biofuel cells.