Abstract
Multi-analyte sensing using exclusively laser-induced graphene (LIG)-based planar electrode systems was developed for sweat analysis. LIG provides 3D structures of graphene, can be manufactured easier than any other carbon electrode also on large scale, and in form of electrodes: hence, it is predestinated for affordable, wearable point-of-care sensors. Here, it is demonstrated that LIG facilitates all three electrochemical sensing strategies (voltammetry, potentiometry, impedance) in a multi-analyte system for sweat analysis. A potentiometric potassium-ion-selective electrode in combination with an electrodeposited Ag/AgCl reference electrode (RE) enabled the detection of potassium ions in the entire physiologically relevant range (1 to 500 mM) with a fast response time, unaffected by the presence of main interfering ions and sweat-collecting materials. A kidney-shaped interdigitated LIG electrode enabled the determination of the overall electrolyte concentration by electrochemical impedance spectroscopy at a fixed frequency. Enzyme-based strategies with amperometric detection share a common RE and were realized with Prussian blue as electron mediator and biocompatible chitosan for enzyme immobilization and protection of the electrode. Using glucose and lactate oxidases, lower limits of detection of 13.7 ± 0.5 μM for glucose and 28 ± 3 μM for lactate were obtained, respectively. The sensor showed a good performance at different pH, with sweat-collecting tissues, on a model skin system and furthermore in synthetic sweat as well as in artificial tear fluid. Response time for each analytical cycle totals 75 s, and hence allows a quasi-continuous and simultaneous monitoring of all analytes. This multi-analyte all-LIG system is therefore a practical, versatile, and most simple strategy for point-of-care applications and has the potential to outcompete standard screen-printed electrodes.Graphical abstract
Highlights
IntroductionThe pursuit of developing bio- and chemosensors has long been driven by the realization that these sensors have a powerful potential to address the analytical challenges of onsite, rapid, accurate, simple, and inexpensive detection
Published in the topical collection 2D Nanomaterials for Electroanalysis with guest editor Sabine Szunerits.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.The pursuit of developing bio- and chemosensors has long been driven by the realization that these sensors have a powerful potential to address the analytical challenges of onsite, rapid, accurate, simple, and inexpensive detection
The key was to demonstrate that an all-laser-induced graphene (LIG) concept is possible for all three electroanalytical detection strategies and that those can be combined for multi-analyte detection
Summary
The pursuit of developing bio- and chemosensors has long been driven by the realization that these sensors have a powerful potential to address the analytical challenges of onsite, rapid, accurate, simple, and inexpensive detection. Advancements in biorecognition elements, in coating chemistries, and signal amplification new sensor designs keep proving exactly this potential. A quite current trend in onsite diagnostics seeks to develop wearable sensors for clinical diagnostics and for monitoring of fitness or health state [1]. The miniaturization of electronic components and development of new materials are key to advance wearable sensing technology further, as can be evidenced by products ranging from smart watches and wristbands which monitor heartbeat or body temperature through adhesive stickers and screen-printed tattoos to smart textiles and contact lenses which are capable of collecting more information than physical vital signs [2]
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