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We report on the drop-cast production of glucose biosensors based on the most efficient bioelectrocatalysis by pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ GDH). To orient the enzyme upon immobilization we suggest using poly(Methylene Green) (p(MG)) nanoparticles acting as anchors. Synthesis of polymeric anchors has been carried out in course of Methylene Green electropolymerization, which allowed to tune polymer-to-monomer ratio in the drop-cast mixtures varying the monomer concentration and applying different number of potential sweep cycles. Except for elimination of electrochemical step for the electrode modification, opening the prospects for mass-production, the use of drop-cast enzyme anchors provides advantageous characteristics of the resulting biosensors. Catalytic current of PQQ GDH immobilized over p(MG) nanoparticles obtained in optimal conditions is increased only 2–2.5 times after addition of the freely diffusing mediator. Obviously, the lowest ratio of mediated-to-reagentless current points to the most efficient bioelectrocatalysis. The obtained ratio is 2.5 times lower than that for biosensors based on electropolymerized p(MG) films and practically an order of magnitude lower than that for the best reagentless sensors based on PQQ GDH immobilized over conductive nanomaterials. The achieved most efficient bioelectrocatalysis provides high sensitivity of the elaborated biosensors even at 0.0 V potential, which allows to operate them in power generation mode and control relative sweat glucose variation as a tool for non-invasive diabetes monitoring. [Display omitted] • Drop-cast polyazine anchors for PQQ glucose dehydrogenase were elaborated • The most efficient bioelectrocatalysis by PQQ glucose dehydrogenase was achieved • Power-generating biosensors are applicable for diabetes control by sweat analysis [ABSTRACT FROM AUTHOR]

We report the single‐step fabrication of advanced electrochemical biosensors upon drop‐casting of "artificial peroxidase", that is, oxidase‐containing mixtures. Compared to bienzyme biosensors, we substitute peroxidase with more active and stable nanozymes based on catalytically synthesized Prussian Blue. The electroactivity of nanozymes in the sensing membrane was facilitated with carbon black nanoparticles, which resulted in record sensitivity of the H2O2 transducer exceeding 1.1 A M−1 ⋅ cm−2. Both glucose and lactate oxidases were co‐immobilized with nanozymes in alkoxysilane or perfluorosulfonated ionomer membranes. The proposed drop‐casting approach results in biosensors that are advantageous over those conventionally produced upon layer‐by‐layer immobilization in terms of i) almost an order of magnitude increased sensitivity, ii) unsurpassed biosensor‐to‐transducer sensitivity ratio reaching the value of 0.3, and iii) three times extended operational lifetime. [ABSTRACT FROM AUTHOR]

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 × 100 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. [Display omitted] [ABSTRACT FROM AUTHOR]

In contrast to "self-powered" (bio)sensors aiming to generate maximum energy output, we propose the systems with the lowest potential difference between the working and the counter electrodes, which in galvanic mode would provide achievement of the best analytical performance characteristics. Prussian Blue based (bio)sensors known to operate at 0.00 V versus Ag|AgCl reference, in the short-circuit regime generate the current proportional to analyte concentration. Sensitivity and dynamic range of Prussian Blue based (bio)sensors in power generation mode are, respectively, even slightly higher and wider compared to the same (bio)sensors operated in the conventional three-electrode regime powered by a potentiostat. Selectivity of the (bio)sensors in power generation mode is similarly high relative to both oxygen, allowing H2O2 detection by its reduction, and reductants. Among the most important advantages of the proposed power generation mode is an order of magnitude decreased noise compared to performance in a conventional three-electrode setup powered by a potentiostat. Noiseless performances of Prussian Blue based (bio)sensors would open new horizons for electrochemical analysis. [ABSTRACT FROM AUTHOR]

We report on the novel reagentless and label-free detection principle allowing discrimination of specific binding over non-specific interactions. Unlike majority of impedimetric and conductometric (bio)sensors, which specific and unspecific signals are directed in the same way (resistance increase), making doubtful their real applications, the response of the reported system results in resistance decrease, which is directed oppositely to the background. The mechanism of the resistance decrease is the polyaniline self-doping, i.e. as an alternative to proton doping, an appearance of the negatively charged aromatic ring substituents in polymer chain. Negative charge at boronic ring substituent appears as a result of complex formation with di- and triols, i.e. specific binding. Thermodynamic data on interaction of the electropolymerized aminophenylboronic acids with saccharides and hydroxy acids indicate that the observed resistance decrease is due to polymer interaction with polyols. A possibility to detect microorganisms ( Penicillum chrysogenum) on the basis of interdigitated electrodes modified with boronate substituted polyaniline is also shown. The first reported conductivity increase as a specific signal opens new horizons for reagentless affinity sensors. [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]

Self-powered sensors are among promising candidates for wake-up device elaboration. Generally, such sensors are designed to generate superior energy output to the detriment of analytical performance. Here we report on power output of Prussian Blue (PB) based (bio)sensors retaining advanced analytical performance in power generation mode. The maximum power density is linearly proportional to analyte concentration: the slopes for hydrogen peroxide sensor and glucose biosensor are of 37 mW M−1 cm−2 and 3 mW M−1 cm−2, respectively. The cells consisted of power generating (bio)sensors are able to switch on a light-emitting diode (LED) at threshold concentration of 0.6 mM H 2 O 2 or 8 mM glucose that is suitable for naked-eye semiquantitative analysis. The presented prototype of signaling device is expected to have significant impact on the development of autonomous wake-up sensors for medical, industrial or environmental monitoring. • Prussian Blue (PB) based (bio)sensors power output is a function of analyte content. • The galvanic cells were made of PB based (bio)sensors. • The cells connected to a LED can be utilized as wake-up signaling devices. • Threshold level for sensor-based wake-up device is 0.6 mM of H 2 O 2. • Threshold level for biosensor-based wake-up device is 8 mM of glucose. [ABSTRACT FROM AUTHOR]