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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]

We report on the simultaneous monitoring of sweat lactate concentration and sweat secretion rate. For this aim lactate oxidase-Prussian Blue enzyme-nanozyme type lactate biosensors were elaborated. The use of siloxane-perfluorosulfonated ionomer composite membrane for enzyme-nanozyme immobilization results in the biosensor displaying flux independence in the whole range of physiological sweat secretion rates (0.025–2 μl cm-2 min-1). On the contrary, current response of the biosensor based on solely siloxane membranes becomes saturated at physiological sweat lactate concentration, depending mostly on the flow rate. Accordingly, for simultaneous monitoring of sweat lactate concentration and its secretion rate both flow-through biosensors were integrated with high-accuracy wearable electronic devices allowing real-time remote monitoring. As found, during exhaustive physical exercise sweat secretion rate and lactate content are independent of each other, thus, confirming that this excretory liquid is suitable for non-invasive diagnostics. [Display omitted] • Flow-independent enzyme-nanozyme lactate biosensors elaborated. • Wearable high-accuracy device for real-time remote metabolite monitoring designed. • The independence of sweat secretion rate and lactate content shown. [ABSTRACT FROM AUTHOR]

Simple drop-casting of the catalytically synthesized Prussian Blue nanoparticles with subsequent annealing results in modified electrodes with high electrochemical and electrocatalytic activity. The electroactive fraction of the deposited Prussian Blue being independent of the surface concentration, is decreased with an increase of the nanoparticles size reaching its lower saturation at approximately 25%. Sensitivity of the corresonding hydrogen peroxide sensor is increased linearly with the amount of Prussian Blue reaching its upper saturation together with formation of continuative film, indicating most probably, a nanoparticles monolayer. Due to their performance characteristics the Prussian Blue nanozymes modified electrodes would be highly attractive for corresponding sensors and biosensors. [ABSTRACT FROM AUTHOR]

In contrast to bienzyme biosensors, we propose the nanozyme-enzyme based ones substituting the enzyme peroxidase with the more active and stable nanoparticles "artificial peroxidase". The use of catalytically synthesized Prussian Blue based nanozymes simplifies assembling of hydrogen peroxide transducer providing its higher sensitivity. For immobilization of lactate oxidase the composite alkoxysilane – perfluorosulfonated ionomer (PFSI) membranes are proposed achieving the significantly improved operating stability. The resulting nanozyme-enzyme lactate biosensor displays twice higher sensitivity (>0.2 A M−1 cm−2) compared to the Prussian Blue film based one. Nanozymes "artificial peroxidase" are expected to find wide use in elaboration of oxidase based biosensors. Image 1 • The biosensor based on nanozyme substituting enzyme peroxidase. • Novel immobilization protocol for lactate oxidase providing its higher stability. • The nanozyme-enzyme lactate biosensor with twice higher sensitivity. [ABSTRACT FROM AUTHOR]