Research On Antioxidant Biosensors

Oxidation in vivo or in the diet has aroused widespread concern.Oxidative metabolism is of great importance for the survival of cell. But also has its negative side, side effect is it can led to oxidant caused by free radicals or other reactive oxidant species, which produced during the metabolism process. More and more evidence can prove that, these species are able to form a control mechanism in a variety of organisms. The destructive power of excess radicals usually exceed protection mechanisms(such as superoxide dismutase, catalase, peroxidase, etc.) and will prevent self-healing capabilities of cell through oxidant membrane or damage DNA, eventually lead to cell damage or death (eg apoptosis).However, the mechanism of the reactive oxygen species has not yet been solved. The oxidation reaction is one of the factors, which causing food spoilage(such as changes in the nutritional value, color, odor, texture, as well as food safety). It is estimated that, there are about half of the fruits and vegetables spoiled due to expired harvest time. Thus,it is very necessary to establish a good defense mechanism and an efficient method to detect it. The main works are as follows:1. Antioxidant Sensors Based on Iron Diethylenetriaminepentaacetic Acid, Hematin, and Hemoglobin Modified TiO2 Nanoparticle Printed ElectrodesAntioxidant amperometric sensors based on iron-containing complexes and protein modified electrodes were developed. Indium tin oxide glass was printed with TiO₂ nanoparticles, onto which iron-containing compounds and protein were adsorbed. When applied with negative potentials, the dissolved oxygen is reduced to H₂O₂ at the electrode surface, and the H₂O₂ generated in situ oxidizes Fe^II to Fe^III, and then electrochemical reduction of Fe^III therefore gives rise to a catalytic current. In the presence of antioxidants, H₂O₂ was scavenged, the catalytic current was reduced, and the decreased current signal was proportional to the quantity of existing antioxidants. A kinetic model was proposed to quantify the H₂O₂ scavenging capacities of the antioxidants. With the use of the sensor developed here, antioxidant measurements can be done quite simply: put the sensor into the sample solutions (in aerobic atmosphere), perform a cathodic polarization scan, and then read the antioxidant activity values. The present work can be complementary to the previous studies of antioxidant sensor techniques based on OH radicals and superoxide ions scavenging methods, but the sensor developed here is much easier to fabricate and use.2. How far can hydroxl radical translate on DNA helix?Based on the principles of DNA charge transfer, we made a kind of electrode that can be regulated by the magnetic field, which was denoted as ds-DNA-Fe₃O₄@TiO₂. First prepare SH-DNA modified electrode, then prepare target DNA (with amino on the terminal)solution ,and carry on amino-carboxyl complex reaction. In order to remove DNA which is non-specific adsorpted on the electrode surface ,put the SH-DNA modified electrode in to MCH solution for a period of time. When perform hybridization reaction, add intercalator AQMS or MB, then test with OSW voltammograms. Put the electrode under Uv illumination, OH radicals produced during this process will damage DNA. In order to study the transmission distance of hydroxyl radical on DNA , we add a magnet to adjust the level of DNA damage.