Amperometric Flow-Injection Analysis of Phenols Induced by Reactive Oxygen Species Generated under Daylight Irradiation of Titania Impregnated with Horseradish Peroxidase

Abstract

Titanium dioxide (TiO2) is a unique material for biosensing applications due to its capability of hosting enzymes. For the first time, we show that TiO2 can accumulate reactive oxygen species (ROS) under daylight irradiation and can support the catalytic cycle of horseradish peroxidase (HRP) without the need of H2O2 to be present in the solution. Phenolic compounds, such as hydroquinone (HQ) and 4-aminophenol (4-AP), were detected amperometrically in flow-injection analysis (FIA) mode via the use of an electrode modified with TiO2 impregnated with HRP. In contrast to the conventional detection scheme, no H2O2 was added to the analyte solution. Basically, the inherited ability of TiO2 to generate reactive oxygen species is used as a strategy to avoid adding H2O2 in the solution during the detection of phenolic compounds. Electron paramagnetic resonance (EPR) spectroscopy indicates the presence of ROS on titania which, in interaction with HRP, initiate the electrocatalysis toward phenolic compounds. The amperometric response to 4-AP was linear in the concentration range between 0.05 and 2 μM. The sensitivity was 0.51 A M–1 cm–2, and the limit of detection (LOD) 26 nM. The proposed sensor design opens new opportunities for the detection of phenolic traces by HRP-based electrochemical biosensors, yet in a more straightforward and sensitive way following green chemistry principles of avoiding the use of reactive and harmful chemical, such as H2O2.

Universal Platform for Ratiometric Sensing Based on Catalytically Induced Inner-Filter Effect by Cu2+

“…The collection of UV absorption curves (Figure S1) confirmed that the catalytical oxidation of OPD to DAP with a typical absorption peak at 417 nm induced the emission not from the generation of the Cu­(OPD) 2 2+ complexes, which exhibited an absorption peak at 438 nm . The emission from DAP based on the catalytical oxidation in the presence of Cu 2+ was similar to that using horseradish peroxidase or enzyme mimics . Furthermore, the emission was dependent on the concentration of Cu 2+ (Figure A).…”

“…26 The emission from DAP based on the catalytical oxidation in the presence of Cu 2+ was similar to that using horseradish peroxidase or enzyme mimics. 27 Furthermore, the emission was dependent on the concentration of Cu 2+ (Figure 1A). Then, PTA-NH 2 as the donor was introduced to the above OPD-Cu 2+ system.…”

Horseradish peroxidase-triggered direct in situ fluorescent immunoassay platform for sensing cardiac troponin I and SARS-CoV-2 nucleocapsid protein in serum

“…The amino group was an electron-donating group when located in ortho and counter position. It attached to the benzene ring with an unshared electron pair led to p-π hyper conjugation on the benzene ring and increased the density of the electron cloud on the aromatic ring ( Maity et al, 2020 ; Rahemi et al, 2020 ). Thus, this could help to explain why MPD and PEI did not produce fluorescence.…”

Flow-based System: A Highly Efficient Tool Speeds Up Data Production and Improves Analytical Performance

“…The applications can be seen for organic analytes such as organophosphate insecticides, 173 ascorbic acid, 2,3-dihydroxybenzoic acid and pyrocatechol 174 and phenol. 175 Applications of inorganic analyte detected by amperometric flow-based system are chlorine, 176 heavy metals (Pb(II), Cd(II) and Cu(II)), 177 manganese 178 and arsenic. 179 Potentiometric detection can be observed for ion-selective sensors.…”