“…Besides AuNPs, magnetic nanoparticles have also found application as signal labels in biosensing systems, such as molecular detection and related strategies that rely on ligand-receptor binding. In particular, iron oxide magnetic nanoparticles (NPs), such as magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 ), are particularly appealing due to their magnetic properties, tunable size, biocompatibility, and greater ease of synthesis than other magnetic materials [ 20 , 21 , 22 ]. Indeed, recent studies have shown how to use magnetic nanoparticles to improve the efficiency of the functionalization process [ 23 ], to realize multiplexing immunoassays [ 24 ] and for magnetic detection [ 14 , 25 , 26 ].…”