OPTICAL SENSORS FOR TOTAL

ANTIOXIDANT CAPACITY MEASUREMENT

Mustafa Bener, Reşat Apak

Department of Chemistry, Faculty of Engineering, IstanbulUniversity,

Avcilar 34320, Istanbul, Turkey

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Oxidative stress occurs when the balance between reactive oxygen/nitrogen species (ROS/RNS) and antioxidant protection systems of the organism turns towards reactive species. Under oxidative stress conditions, reactive species attack various biological macromolecules (enzymes, proteins, DNA, etc.) and cause many serious complications such as cancer, Alzheimer and cardiovascular diseases. Antioxidant compounds are natural combat agents against oxidative stress−originated diseases. Because of known health beneficial effects of food antioxidants, selective and sensitive assays for rapid sensing of antioxidants have gained importance. Compared to classical instrumental methods, optical sensors offer a number of advantages in many applications, such as speed, affordability, field use, simplicity of measurement and handling of results. Optical sensors can evaluate analytical information with the use of optical transduction techniques (absorbance, reflectance, etc.).Generally, optical sensors are formed by immobilizing various reagents (usually named as “ligand” for a specific Lewis acid analyte such as a metal ion) onto appropriate membranes. In optical sensing, covalent bonding, electrostatic interaction with resin, incorporation into PVC (polyvinyl chloride) membranes and capture by Nafion films are usually used to fix the reagent in an attached state. Our research group developed versatile optical sensors having a linear response over a wide concentration range of various antioxidant compounds [1-3]. The reagents we immobilized on suitable films usually operated by the principle of electron transfer toward antioxidant analytes, and the resulting reduced species on the membranes generally showed a different color than of the parent reagents. These sensors can be used for simple quantitative assessment of antioxidant capacity of complex matrices such as food extracts even with a simple colorimeter or visual detection depending on a color-comparison scale. These optical sensors may also show a potential for testing various degradations during shelf-life, where antioxidants protect food and other matrices.

KEYWORDS: Oxidative stress, Antioxidants, Optical sensors, Total antioxidant capacity

REFERENCES:

1. M. Bener, M. Ozyurek, K. Guclu, R. Apak, Anal. Chem. (2010) 82 4252-8.

2. M. Bener, M. Özyürek, K. Güçlü, R. Apak,J. Agric. Food Chem. (2013) 61 8381-8388.

3. M. Bener, R. Apak, Sens. Actuator B-Chem.(2017) 247 155-62.