Surface EngineeringMagnetic Nanoparticles with Redoxand Biological Properties

Magnetic nanoparticles (MNPs) are recognized as valuable tools for derived electrochemical biosensors and offer immense potential for the efficient diagnosis and detection of disease biomarkers. Herein, a new step-by-step approach for the development of multifunctional MNPs that exhibit both redox and biological properties is described. First, chemical cross-linking was employed to label these MNPs with redox dyes (ferrocene, anthraquinone, or methylene blue). Bovine serum albumin (BSA) was then applied as the terminal protective layer. Next, click chemistry was employed to engineer immunoglobulin G (IgG) onto the surface of these redox MNPs (IgG number of 35 ± 8 per MNP), providing multifunctionality. Before and after surface engineering, these MNPs exhibited high-quality size distributions, as characterized by differential centrifugal sedimentation (DCS). Square-wave voltammetry was used to reveal the presence of 21.8 ± 1.3 ferrocene molecules on each anti-CD63-based redox MNP, and the anti-CD63 antibodies still maintained their bioactivity toward the CD63 antigen. These multifunctional MNPs could be promising tools for advancing the development of MNP-assisted electrochemical biosensors and meeting the needs of single-nanoparticle electrochemistry.