Hydrogen peroxide sensor based on horseradish peroxidase immobilized on an electrode modified with DNA-L-cysteine-gold-platinum nanoparticles in polypyrrole film

A third-generation mediator-free hydrogen peroxide biosensor was fabricated by combining electrodeposition and self-assembly techniques. In this strategy, Au-Pt hybrid nanoparticles were electrodeposited on a film of polypyrrole, and L-cysteine was assembled to their surface by exploiting the strong affinity between mercapto groups and nanoparticles. Then, DNA and horseradish peroxidase were respectively self-assembled on the surface of the electrode. The resulting electrode was characterized by impedance spectroscopy, and the electrode surface ( without enzyme) was characterized by scanning electron microscopy. The response of the sensor towards hydrogen peroxide, as investigated by cyclic voltammetry and chronoamperometry, is linear between 4.9 mu M to 4.8 mM, with a detection limit of 1.3 mu M ( at an S/N of 3). The apparent Michaelis-Menten constant (K-M(app)) is 0.69 mM.