Abstract
We describe an electrochemical device for the simultaneous monitoring of glucose and lactate in sweat, based on enzymatic sensors exploiting capillary flow to induce continuous, stable sensing. The enzymes, namely glucose oxidase and lactate oxidase, were anchored to a graphene oxide and chitosan composite (GO-Ch) of original synthesis, to achieve stable deposition of the bioreceptors on the electrochemical platform. We tested both biosensors on a realistic device architecture: they were embedded in a nitrocellulose strip, to exploit capillary force to induce a continuous flux of sweat on the sensor platform, ensuring the constant renewal of sample. We could achieve good sensitivity at potentials close to zero by using Prussian Blue as redox mediator, thus avoiding interference from other chemical species present in the complex matrix. The sensing signal was stable and linear over two hours in a concentration range of glucose and lactate between the limit of quantification (32 and 68 nM, respectively) and the upper limit of linearity (3.8 and 50.0 mM, respectively). The device is simple, robust, stable, and can be easily worn without the direct contact of the active part with the skin, making it suitable for simultaneous monitoring of glucose and lactate in human sweat.
Highlights
Wearable biosensors are receiving increasing attention from scien tific and medical communities since they constitute non-invasive and cheap devices to monitor, by remote, parameters of primary importance for human health or fitness goals: different physical and chemical sensors can be employed, allowing personalized analyses or training programmes
If on the one hand they allow an easy detection of these chemical parameters, a still open problem is how to achieve a continuous flow of sweat on the sensor platform in order to induce a punctual definition of the physiological status of the person under monitoring; only a few devices proposed so far, include a capillary fluidic system, which can collect higher and more homoge neous amounts of sweat to correctly wet all the electrodes, indepen dently of the individual perspiration rate [9,10]
We propose an enzymatic biosensor based on graphene oxide and chitosan composite (GO-Ch) and electrodeposited Prussian blue (PB) for the simultaneous detection of glucose and lactate directly in a continuous flow of a complex matrix resembling human sweat
Summary
Wearable biosensors are receiving increasing attention from scien tific and medical communities since they constitute non-invasive and cheap devices to monitor, by remote, parameters of primary importance for human health or fitness goals: different physical and chemical sensors can be employed, allowing personalized analyses or training programmes. If on the one hand they allow an easy detection of these chemical parameters, a still open problem is how to achieve a continuous flow of sweat on the sensor platform in order to induce a punctual definition of the physiological status of the person under monitoring; only a few devices proposed so far, include a capillary fluidic system, which can collect higher and more homoge neous amounts of sweat to correctly wet all the electrodes, indepen dently of the individual perspiration rate [9,10]. We propose an enzymatic biosensor based on GO-Ch and electrodeposited PB for the simultaneous detection of glucose and lactate directly in a continuous flow of a complex matrix resembling human sweat. To achieve a truly wearable biosensor without any complicated external device, a driving force to ensure the continuity of sweat transport is required: as a proof of concept for the realization of instrumental working conditions very close to the actual application, the device was integrated in capillary flow system activated by a nitrocellulose strip to achieve the collection and delivery of sweat on the sensor platform
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