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We propose pulse power generation (PPG) amperometry as an advanced readout realized for Prussian blue (PB)-based (bio)sensors. In contrast to the conventional power generation mode, when the current response is generated upon continuous short-circuiting, the suggested pulse regime is fulfilled by periodic opening and shorting of the circuit. Despite PB being electroactive, the pulse readout is advantageous over conventional steady-state power generation, providing up to a 15-fold increased signal-to-background ratio as well as dramatically improved sensitivity exceeding 10 A·M -1 ·cm -2 for H 2 O 2 sensors and 3.9 A·M -1 ·cm -2 for glucose biosensors. Such analytical performance characteristics are, most probably, achieved due to the enrichment of the diffusion layer by analyte mass transfer from the bulk upon opening of the circuit. Due to an improved sensitivity-to-background ratio, reduced flow-rate dependence, and enhanced operational stability, the regime allows reliable monitoring of blood glucose variations through sweat analysis with the on-skin device.

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Despite non-invasive instant monitoring of sweat metabolites is becoming a general trend in early diagnostics and screening, the reliability and accuracy of the on-skin electrochemical biosensors in real-life scenarios still remain questionable. As a rule, mass transport effects in scantily excreted liquids are ignored, when considering the design of such wearable setups. Here we provide a comprehensive investigation of the disruption factors for commonly used Prussian Blue based (bio)sensors under different hydrodynamic conditions (2 × 10 -5 - 5 × 10 0  mm s -1 electrolyte velocity). A huge effect of flow on the (bio)sensors response has been revealed and explained with transport limitations for both analyte influx and reaction product outflux. It suggests no need for improving the sensor sensitivity, while minimizing analyte consumption and enhancing product withdrawal. Some strategies concerning measurement schemes and sensor design ensuring reliable sweat analysis have been discussed and illustrated for lactate and glucose on-skin monitoring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Catalytic current of pyrroloquinoline quinone (PQQ)-glucose dehydrogenase (PQQ-GDH) immobilized over electropolymerized methylene green (MG) is increased only five times after the addition of the freely diffusing mediator. This value, being an efficiency criterion for bioelectrocatalysis, is several (three to six) times lower than that for the best reagentless glucose electrodes reported for this enzyme. Thermodynamics of the polyMG|PQQ-GDH electrode is determined by the enzyme-catalyzed reaction pointing to the direct bioelectrocatalysis. PQQ-GDH immobilized over polyMG displays the current plateau region from 0.0 to 0.2 V in the presence of glucose; at 0.00 V, being the optimal potential for biosensing applications, the catalytic current of the polyMG|PQQ-GDH electrode is 700-fold higher than that for the enzyme on a blank electrode. Successful glucose detection in human sweat by means of the corresponding enzyme electrode confirms that the reported bioelectrocatalytic system is attractive for advanced biosensors, as well as for biofuel cells.

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)