Experimental evaluation of kinetics and biochemical characteristics of MnO2 nanoparticles as high throughput peroxidase-mimetic nanomaterials

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Despite the well-known concepts on the intrinsic peroxidase-like activity of MnO2 nanoparticles, up to date, their biochemical and kinetics characteristics were not investigated, especially, the current information about their performances toward n-electron oxidation of 3, 3′-diaminobezedine for producing indamine polymers is on limitation. Therefore, herein, the MnO2 nanoparticles were synthesized by a simple low-cost co-precipitation method and then characterized by XRD, SEM, and DLS analysis. Besides, their peroxidase-like activity was evaluated upon standard peroxidase enzyme assay, revealing high intrinsic peroxidase-like activity for the as-mentioned MnO2 nanozymes. Considering their high intrinsic peroxidase-like activity, their optimal biochemical characteristics were quantified by probing the progress of -electron irreversible oxidation of 3, 3′-diaminobezedine in the presence of MnO2 nanozymes as peroxidase mimics. The maximal activity of the as-mentioned MnO2 nanoparticles with high intrinsic peroxidase-like activity was observed when the pH and temperature of the reaction media were fixed over 3.0–6.0 and 23℃–25℃, in order, revealing very high pH and thermal stability of the as-prepared nanoparticles. The salt stability of these nanoparticles was also checked using NaCl as model salt, revealing that the nanozymatic activity was stable over a salt concentration as high as 3–7 M. In addition, the affinity constant (Km) and maximum velocity of the nanozyme-catalyzed oxidation of 3, 3′-diaminobezedine were found to be 1.6 mM and 47 nM sec−1, in turn.