tr. Fax: +90 212 4737180.Nanoparticle (NP)-based analytical methods have displayed a rapid development at the interface of analytical chemistry, food chemistry, biochemistry, and nanotechnology, together with their related industries. For the design of novel antioxidant assays, NPs can be used as colorimetric or electrochemical probes, components in chemical and biological detectors, and radical generation systems. Most applications of NPs used as probes for food chemicals and biochemicals are associated with the use of Au, Ag, magnetite (Fe 3 O 4 ) or titania (TiO 2 ) nanoparticles and quantum dots. Chemical reduction-based nanotechnological colorimetric assays of antioxidant capacity make use of the formation or enlargement of noble metal nanoparticles (AuNPs, AgNPs, etc.) upon reaction of Au(III) or Ag(I) salts with antioxidant compounds acting as chemical reductants.In this chapter, NP-based methods for the measurement of total antioxidant capacity involving chemical reduction together with the methods for the detection of reactive oxygen and nitrogen species (ROS/RNS) and determination of their scavenging activity have been reviewed. Within this scope, spectroscopic methods associated with electron transfer and noble metal nanoparticles as well as electroanalytical biosensor-originated antioxidant activity/capacity methods
Excessive amounts of reactive oxygen species (ROS), unless counterbalanced by antioxidants, can cause cellular damage under oxidative stress conditions; therefore, antioxidative defenses against ROS must be measured. With the development of nanotechnology, nanoparticles have found numerous applications in science, health, and industries. Magnetite nanoparticles (Fe3O4:MNPs) have attracted attention because of their peroxidase-like activity. In this study, hydroxyl radicals (•OH) generated by MNPs-catalyzed degradation of H2O2 converted the N,N-dimethyl-p-phenylenediamine (DMPD) probe into its colored DMPD•+ radical cation, which gave an absorbance maximum at λ = 553 nm. In the presence of antioxidants, •OH was partly scavenged by antioxidants and produced less DMPD•+, causing a decrease in the 553 nm-absorbance. Antioxidant concentrations were calculated with the aid of absorbance differences between the reference and sample solutions. The linear working ranges and trolox equivalent antioxidant capacity coefficients of different classes of antioxidants were determined by applying the developed method. In addition, binary and ternary mixtures of antioxidants were tested to observe the additivity of absorbances of mixture constituents. The method was applied to real samples such as orange juice and green tea. Student t-test, F tests, and the Spearman’s rank correlation coefficient were used for statistical comparisons.
A novel electrochemical method of determination for nitroguanidine (NG) was developed by modifying glassy carbon electrode surface with a mixture of well-dispersed multi-walled carbon nanotubes (MWCNTs) and polyvinylpyrrolidone (PVP) used...
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