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The pathway from the advanced electrocatalyst to nanozymes defeating natural enzyme is reviewed. Prussian blue, being the most advantageous electrocatalyst for hydrogen peroxide reduction, is obviously the best candidate for mimicking peroxidase activity. Indeed, catalytically synthesized Prussian blue nanoparticles are characterized by the catalytic rate constants, which are significantly (up to 4 orders of magnitude) higher than for enzyme peroxidase. Displaying in addition the enzymatic specificity in terms of an absence of oxidase-like activity, catalytically synthesized Prussian blue nanoparticles can be referred to as nanozymes. The latter provide the most versatile method for surface covering with the electrocatalyst, allowing to modify non-traditional materials like boron-doped diamond. For stabilization, Prussian blue core can be covered with nickel hexacyanoferrate shell; the resulting core–shell nanozymes still defeat natural enzyme in terms of activity. Discovering the catalytic pathway of nanozymes "artificial peroxidase" action, we have found the novel advantage of nanozymes over the corresponding biological catalysts: their dramatically (100 times) improved bimolecular rate constants. [ABSTRACT FROM AUTHOR]

We report on fully electrochemical flow-through synthesis of Prussian Blue based nanozymes defeating peroxidase in terms of more than 200 times higher catalytic rate constant (kcatapp = 6 x 104 s-1). Being reagentless, reproducible, simple and scalable, the proposed approach blazes new trails for the electrosynthesis of functional conductive and electroactive nanomaterials. [ABSTRACT FROM AUTHOR]

We propose catalytically synthesized nanozymes based on Prussian Blue (PB) and azidomethyl-substituted poly (3,4-ethylenedioxythiophene) (azidomethyl-PEDOT) as novel electrocatalytic labels for DNA/RNA sensors. Catalytic approach allowed to synthesize highly redox and electrocatalytically active Prussian Blue nanoparticles functionalized with azide groups that enable 'click' conjugation with alkyne-modified oligonucleotides. Both competitive and sandwich-type schemes were realized. As the sensor response the direct (mediator-free) electrocatalytic current of H 2 O 2 reduction can be measured, which is proportional to the concentration of the hybridized labeled sequences. The current of H 2 O 2 electrocatalytic reduction is only 3–8 times increased in the presence of the freely diffusing mediator catechol, which indicates high efficiency of direct electrocatalysis with the elaborated labels. Electrocatalytic amplification of the signal allows robust detection of (63–70)-base target sequences with concentrations below 0.2 nM in blood serum within an hour. We believe, the use of advanced Prussian Blue based electrocatalytic labels sets new avenues for point-of-care DNA/RNA sensing. [Display omitted] • Catalytically synthesized functionalized nanozymes possess high catalytic activity. • Nanozyme functionalization with azide groups enables 'click' conjugation. • Efficient direct electrocatalysis with the labels provides mediator-free operation. • Electrocatalytic signal amplification allows detecting down to 0.01 nM of DNA. [ABSTRACT FROM AUTHOR]

• Prussian Blue based nanozymes catalyze reduction of organic peroxides. • Nanozymes are significantly more active than horseradish peroxidase. • Selectivity of nanozymes to H 2 O 2 is higher as compared to peroxidase. Prussian Blue based nanozymes are able to catalyze reduction of organic peroxides similarly to the enzyme peroxidase. For the whole range of peroxides under study the catalytic rate constant for 3,3′,5,5′-tetramethylbenzidine in case of nanozymes is significantly higher as compared to horseradish peroxidase. Moreover, the selectivity of nanozymes towards hydrogen peroxide relatively organic peroxides reduction is higher than that for the enzyme, which can be explained in terms of different ability of peroxides to penetrate to the bulk of catalytically synthesized Prussian Blue nanoparticles. On the contrary, selectivity of Prussian Blue film modified electrodes is much lower and even negligible among hydrogen, urea and methyl ethyl ketone peroxides. An ability to tune the selectivity would allow individual detection of peroxides in their complex mixtures with Prussian Blue nanostructures. [ABSTRACT FROM AUTHOR]