A new amperometric H2O2 biosensor based on nanocomposite films of chitosan-MWNTs, hemoglobin, and silver nanoparticles

A new H2O2 biosensor was fabricated on the basis of nanocomposite films of hemoglobin (Hb), silver nanoparticles (AgNPs), and multiwalled carbon nanotubes (MWNTs)-chitosan (Chit) dispersed solution immobilized on glassy carbon electrode (GCE). The immobilized Hb displayed a pair of well-defined and reversible redox peaks with a formal potential (E (theta')) of -22.5 mV in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k (s)) in the Chit-MWNTs film was evaluated as 2.58 s(-1) according to Laviron's equation. The surface concentration (I*) of the electroactive Hb in the Chit-MWNTs film was estimated to be (2.48 +/- 0.25) x 10(-9) mol cm(-2). Meanwhile, the Chit-MWNTs/Hb/AgNPs/GCE demonstrated excellently electrocatalytical ability to H2O2. Its apparent Michaelis-Menten constant (K (M) (app) ) for H2O2 was 0.0032 mM, showing a good affinity. Under optimal conditions, the biosensors could be used for the determination of H2O2 ranging from 6.25 x 10(-6) to 9.30 x 10(-5) mol L-1 with a detection limit of 3.47 x 10(-7) mol L-1 (S/N = 3). Furthermore, the biosensor possessed rapid response to H2O2 and good stability, selectivity, and reproducibility.