Bovine serum amine oxidase and chromate-modified iron oxide nanoparticles for polyamine biosensing

Surface active maghemite nanoparticles (SAMNs) represent a new class of naked maghemite nanoparticles, characterized by peculiar surface properties. A novel hybrid nanomaterial based on SAMNs was developed by coating nanoparticle surface with bichromate, leading to a SAMN@Cr2O7 core–shell nanoconjugate. Electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry showed lower charge transfer resistances, higher capacitive currents, better electrochemical performances, as well as more reversible electrochemical behavior with respect to bare SAMNs. Bichromate shell enhanced SAMN electrocatalytic proper- ties toward hydrogen peroxide reduction at neutral pH. Furthermore, bovine serum amino oxidase (BSAO) was immobilized on the surface of SAMN@Cr2O7 by self-assembly, leading to a magnetic drivable nanocatalyst for polyamine oxidation (SAMN@Cr2O7-BSAO). The hybrid bio-nanomaterial was kinetically characterized and compared with the native enzyme. Immobilized BSAO showed a catalytic constant of about 10.2 % with respect to the native enzyme, while the Michaelis constant, Km , was about 3.7 times higher upon enzyme immobilization. Correspondingly, the binding process led to a 2.4 fold decrease of BSAO catalytic efficiency, kcat/Km. The immobilized enzyme (SAMN@Cr2O7-BSAO) was exploited, in a simple carbon paste electrode configuration, for the development of a new reagentless electrochemical biosensor for polyamines.