Antioxidant Sensors Based on Iron Diethylenetriaminepentaacetic Acid, Hematin, and Hemoglobin Modified TiO2 Nanoparticle Printed Electrodes

Determination of the total antioxidant capacity of the Chinese tea based on a novel "peroxidase/zirconium phosphonate"composite electrochemical sensor

In this work, a novel zirconium phosphonate (ZrPR1R2) was prepared by decorating both the aminoethoxy- group (R1) and the carboxypropyl- group (R2) on the zirconium phosphate layers in order to manipulate further the immobilization of the peroxidase (POD), and an antioxidant biosensor with higher sensitivity was constructed by dropping the POD/ZrPR1R2 composite onto the glassy carbon electrode surface. The activity of the POD/ZrPR1R2 composite was detected by Uv-vis spectra. The direct electrochemical behavior, the electrocatalytic response to dissolved oxygen and hydrogen peroxide, as well as the ability to detect total antioxidant capacity in tea sample were investigated by the methods of cyclic voltammetry. The results indicated that the immobilization of POD in ZrPR1R2 nanosheets matrix enhanced the enzymatic activity, and achieved the fast and direct electron transfer between POD and glassy carbon electrode. Moreover, the POD/ZrPR1R2 composite modified electrode show the electrocatalytic response to hydrogen peroxide in the linear range of 8.8×10-8 to 8.8×10-7 mol L-1, with the detection limit of 3.3×10-8 mol L-1. Attributing to the sensitive response to dissolved oxygen, the total antioxidant capacity can be detected directly in the real tea water by this POD/ZrPR1R2 composite modified electrode.

The Antioxidant Effect of the Metal and Metal-Oxide Nanoparticles

Inorganic nanoparticles, such as CeO₃, TiO₂ and Fe₃O₄ could be served as a platform for their excellent performance in antioxidant effect. They may offer the feasibility to be further developed for their smaller and controllable sizes, flexibility to be modified, relative low toxicity as well as ease of preparation. In this work, the recent progress of these nanoparticles were illustrated, and the antioxidant mechanism of the inorganic nanoparticles were introduced, which mainly included antioxidant enzyme-mimetic activity and antioxidant ROS/RNS scavenging activity. The antioxidant effects and the applications of several nanoparticles, such as CeO₃, Fe₃O₄, TiO₂ and Se, are summarized in this paper. The potential toxicity of these nanoparticles both in vitro and in vivo was well studied for the further applications. Future directions of how to utilize these inorganic nanoparticles to be further applied in some fields, such as medicine, cosmetic and functional food additives were also investigated in this paper.

Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)

In this study, an electrochemical biosensor based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE) was developed and employed for antioxidant screening and antioxidant capacity evaluation. The oxidation peak current of guanine was improved and nearly tripled after modifications of chitosan and MoS2 nanosheet. The immobilized guanine could be damaged by hydroxyl radicals generated in Fenton solution. However, in the presence of antioxidants, the guanine was protected and the oxidation peak current of guanine increased. This process mimics the mechanism of antioxidant protection in human body. The factors affecting preparation of sensor and detection of antioxidant capacity were optimized. At the optimum conditions, the guanine/CS/MoS2/GCE showed wide linear range, low detection limit, satisfactory reproducibility and stability for detection. Ascorbic acid was used as a model antioxidant to evaluate the antioxidant capacity. A good linearity was observed with a correlation coefficient of 0.9959 in the concentrations between 0.5 and 4.0 mg L-1. The antioxidant capacities of three flavonoids were also tested and the rank of antioxidant capacities was ascorbic acid (51.84%), quercetin (45.82%), fisetin (34.39%) and catechin (16.99%). Due to the rapid measurement and low cost, this sensor could provide an available sensing platform for antioxidant screening and evaluation.

A biomimetic enzyme modified electrode for H2O2 highly sensitive detection

An efficient catalyst based on artificial bionic peroxidase was synthesized for electrocatalysis. A poly(ethyleneimine)/Au nanoparticle composite (PEI-AuNP) was prepared and it was then linked to hemin via a coupling reaction between carboxyl groups in hemin and amino groups in PEI without the activation of a carboxyl group by carbodiimide. Fourier transform infrared (FTIR) spectroscopy verified the formation of amido bonds within the structure. The presence of AuNPs contributed greatly in establishing the amido bonds within the composite. Transmission electron microscopy (TEM) and UV-visible spectroscopy were also used to characterize the PEI-AuNP-hemin catalyst. PEI-AuNP-hemin exhibited intrinsic peroxidase-like catalytic activities. The PEI-AuNP-hemin deposited on a glass carbon electrode had strong sensing for H2O2 with a well-defined linear relationship between the amperometric response and H2O2 concentration in the range from 1 μM to 0.25 mM. The detection limit was 0.247 nM with a high sensitivity of 0.347 mA mM(-1) cm(-2). The peroxidase-like catalytic activity of PEI-AuNP-hemin is discussed in relation to its microstructure. The study suggests that PEI-AuNP-hemin may have promising application prospects in biocatalysis and bioelectronics.

Photoelectrochemical device based on Mo-doped BiVO4 enables smart analysis of the global antioxidant capacity in food

For a healthy diet, which is an extension of a high quality lifestyle, tremendous attention has been focused on using antioxidant capacity indicators for food inspections and health guides. Although photoelectrochemical transducers have broadened our horizons for global antioxidant activity analysis, a growing body of foods and beverages needs to be quantified in the visible region and the necessary photoelectrochemical instrumentalization is still in its infancy. Generally, BiVO4 is considered as an ideal starting material for antioxidant surveillance under visible light irradiation. However, it is subjected to unsatisfied charge collection and utilization in practical applications. Herein, we studied the effects of successive molybdenum substitution of vanadium on the photocatalytic behavior of BiMo x V(1-x)O4 under visible light illumination. A superior photocurrent density was obtained for BiMo0.015V0.985O4 due to the flower-like architecture and favorable crystalline form. At the same time, this superhybrid BiMo0.015V0.985O4 composite successfully acted as a sensing unit in a photoelectrochemical platform for antioxidant capacity evaluation in foodstuffs. The related mechanism was further unearthed and discussed in-depth. Such a straightforward yet cogent principle was also applied to our integrated device for the "smart" analysis of the global antioxidant capacity, whereby collected data can be treated as a nutritive value index for routine quality control in the food industry. On the basis of this achievement, it is anticipated that mobile app-based quantitative antioxidant capacity detection will soon be realized.

Combination of hematin and PEDOT via 1-pyrenebutanoic acid: a new platform for direct electrochemistry of hematin and biosensing applications

In this work, we prepare a novel platform based on poly(3,4-ethylenedioxythiophene) (PEDOT) and 1-pyrenebutanoic acid (PBA). PEDOT is a conductive material of heteroatom doping, which can connect with PBA through π–π stacking.