Highly Sensitive Hydrogen Peroxide Biosensor Based on Tobacco Peroxidase Immobilized on p‐Phenylenediamine Diazonium Cation Grafted Carbon Nanotubes: Preventing Fenton‐like Inactivation at Negative Potential

Abstract

Herein, we present a novel electrode platform for H 2 O 2 detection based on the immobilization of recombinant Tobacco Peroxidase (r-TOP) onto graphite electrodes (G) modified with p-phenylenediamine (p-PD) diazonium cation grafted multiwalled carbon nanotubes (MWCNTs). The employment of both p-phenylenediamine moieties and covalent cross-linking by using glutaraldehyde allowed us to enhance the sensitivity, stability, and selectivity toward H 2 O 2 detection, as well as preventing enzyme inactivation due to the electro-Fenton reaction. This reaction continuously produces hydroxyl radicals, whose high and unselective reactivity is likely to reduce drastically the operating life of the biosensor. The protection against the electro-Fenton reaction is mainly ascribed to a beneficial enzyme immobilization leading to a correct orientation achieved through cross-linking the enzyme in combination with interaction between the uncoupled -NH 2 groups (mainly uncharged at pH 7, considering a pK a of 4.6) available on the electrode surface and the enzyme. In particular, the electrode based on the r-TOP/p-PD/MWCNTs/G platform showed a lower limit of detection of 1.8 μM H 2 O 2 , an extended linear range between 6 and 900 μM H 2 O 2 , as well as a significant increase in sensitivity (63.1 � 0.1 μA mM À 1 cm À 2 ) compared with previous work based on TOP. Finally, the r-TOP/p-PD/MWCNTs/G electrode was tested in several H 2 O 2 spiked food samples as a screening analytical method for the detection of H 2 O 2 .

Intrinsic Multienzyme-like Activities of the Nanoparticles of Mn and Fe Cyano-Bridged Assemblies

“…In addition, as summarized in Table 3, the higher stability of the NCPs and stronger oxidizing properties of hydrogen peroxide in acidic medium are reflected in the higher sensitivity, lower detection limit, and wider working concentration range obtained at pH 3 than 7.4. The LDL H2O2 of the NCPs is comparable with that of the biosensors based on various plant peroxidases [34,63]. It can be concluded that the electrocatalysis of hydrogen peroxide reduction by Mn-PB and PB NCPs is reminiscent of their peroxidase-like catalytic substrate oxidation and the cytotoxicity of iron oxide in terms of the destructive action of the produced hydroxyl radicals.…”

Smartphone-Based Electrochemical Biosensor for On-Site Nutritional Quality Assessment of Coffee Blends

“…On the other hand, the presence of CNTs in DRP-110CNT/ Tv Lac + GA significantly favored the stability of the catalytic activity over time up to 400 mM of catechol, shown in Figure 4 b in grey. The well-known high porosity of CNTs plays a dramatic role in the physical adsorption mechanism and in the immobilization stability [ 42 , 43 , 44 , 45 , 46 ]. However, the catalytic current increased slower than with the DRP-110GNP/ Tv Lac + GA electrode, an index of lower sensitivity.…”

Smartphone-Based Electrochemical Biosensor for On-Site Nutritional Quality Assessment of Coffee Blends

“…On the other hand, the presence of CNTs in DRP-110CNT/TvLac + GA significantly favored the stability of the catalytic activity over time up to 400 mM of catechol, shown in Figure 4b in grey. The well-known high porosity of CNTs plays a dramatic role in the physical adsorption mechanism and in the immobilization stability [42][43][44][45][46]. However, the catalytic current increased slower than with the DRP-110GNP/TvLac + GA electrode, an index of lower sensitivity.…”