In the present work we have developed and characterized anovel functionalized core–shell magnetic nanoparticle(Fe3O4@pDA). The present approach is an easy method tomodify nanoparticles. The reactive quinones at the surface ofthe Fe3O4@pDA offer a great opportunity to anchor biologicallyactive macromolecules such as antibodies and enzymes. In thisway, HRP was used as a proof-of-concept for further modica-tions (Fe3O4@pDA/HRP). Finally, the newly prepared enzymaticnanoconjugates were employed to construct a second-genera-tion biosensor (GCE/Fe3O4@pDA/HRP) for H2O2 sensing.Experimental variables were optimized in order to improve thebiosensor response. All the results discussed above demon-strated that the new H2O2 biosensor based on the use ofFe3O4@pDA/HRP compares advantageously (in terms of sensi-tivity, reproducibility and simplicity of the fabrication process)with other biosensor designs