DNA-based biosensor for the electrocatalytic determination of antioxidant capacity in beverages

Abstract

A B S T R A C TReactive oxygen species (ROS) are produced as a consequence of normal aerobic metabolism and are able to induce DNA oxidative damage. At the cellular level, the evaluation of the protective effect of antioxidants can be achieved by examining the integrity of the DNA nucleobases using electrochemical techniques. Herein, the use of an adenine-rich oligonucleotide (dA21 ) adsorbed on carbon paste electrodes for the assessment of the antioxidant capacity is proposed. The method was based on the partial damage of a DNA layer adsorbed on the electrode surface by OH• radicals generated by Fenton reaction and the subsequent electrochemical oxidation of the intact adenine bases to generate an oxidation product that was able to catalyze the oxidation of NADH. The presence of antioxidant compounds scavenged hydroxyl radicals leaving more adenines unoxidized, and thus, increasing the electrocatalytic current of NADH measured by differential pulse voltammetry (DPV). Using ascorbic acid (AA) as a model antioxidant species, the detection of as low as 50 nM of AA in aqueous solution was possible. The protection efficiency was evaluated for several antioxidant compounds. The biosensor was applied to the determination of the total antioxidant capacity (TAC) in beverages.

Electrocatalytic evaluation of DNA damage by superoxide radical for antioxidant capacity assessment

“…The fact that the O ÅÀ 2 attack on DNA led to the generation of this adsorbed compound is remarkable because the oxidation of adenine bases through OH Å radicals generated by Fenton-type reaction was recently demonstrated not to occur via the formation of the diimine species, at least, at levels detectable by CV [29]. Given that both radical attacks led to different products, the reported primary OH Å radical promoter role of O ÅÀ 2 remains uncertain.…”

“…2, curve a). Given that the oxidation peak of the uncatalyzed oxidation of NADH at a bare unmodified CPE is 0.70 V [29], a decreased of more than 550 mV is achieved. A low potential is advantageous for analytical purposes because of the diminution of potential oxidizable interferent compounds present in real food samples.…”

“…From our previous work on antioxidant activity against OH Å on DNA-CPE, it can be concluded that AA seemed to be less efficient as a scavenger of superoxide radical than hydroxyl radicals. In fact, the minimum AA concentration able to show a protective action is more than two order of magnitude lower in the case of OH Å [29].…”

“…100 potential scans were performed between À0.2 and +1.4 V at 500 mV s À1 to ensure a complete oxidation [29].…”

“…Other authors have also used AA in order to study its protective effect on DNA (adsorbed at an electrode surface) against free radicals. However, all these reports only described the scavenging role of AA towards hydroxyl radicals [29,36,37].…”