DNA Probing of Peroxidase‐Mimetic Activities of Selected Manganese‐Based Nanozymes and Measurement of Antioxidant Activity for DNA Protection

Abstract Three different Mn‐based peroxidase‐mimetic nanoparticles (NPs) were synthesized as nanozymes: (i) manganese (II)‐ferrite (MnFe 2 O 4 ) fabricated by co‐precipitating MnCl 2 .4H 2 O and FeCl 3 .6H 2 O; (ii) MnO 2 synthesized from precipitation of MnSO 4 in basic medium; (iii) manganese oxide obtained by reducing KMnO 4 with tris(2‐hydroxyethyl) amine, all characterized using STEM, EDXS, FTIR and XPS techniques. These NPs acted as peroxidases, revealed by using a DNA probe, on which the damage generated by peroxidase mimetic NPs was monitored spectrophotometrically by CUPRAC and 3,3′,5,5′‐tetramethylbenzidine (TMB) methods. Results were confirmed by RP‐HPLC and voltammetry, the latter involving an AuNPs‐modified glassy carbon electrode (GCE), multi‐walled carbon nanotubes (MWCNT) and Nafion combination. Colorimetric assay with CUPRAC rather than TMB better agreed with chromatographic/voltammetric findings in detecting both peroxidase activity and DNA hazard. Mn(III)‐containing manganese oxide from permanganate reduction had stronger peroxidase activity. The proposed method demonstrated protective effects of antioxidants (morin, catechin and quercetin) against oxidative DNA damage for the first time.