This
current Review focuses on recent contributions of wearable
and biodegradable sensors dedicated to health and environmental applications.
Recent examples reported in the literature are presented and critically
discussed in order to diagnose diseases and their response to treatment
with a focus on cancer and Parkinson’s disease. Advances in
devices for body temperature, humidity (skin hydration), human physiological
signals, and metal detection in body fluids are demonstrated concerning
simple and portable platforms. Studies performed outside the controlled
laboratory environment can rapidly help in point-of-care analyses
or self-examination by the patients. Environmental approaches are
also outlined, aiming at gas detection, metal sensing, and environment
humidity, including different substrates showing not only flexible
and biodegradable sensors but also wireless detection and data communication.
The discussed examples for health and environmental analyses have
successfully demonstrated the considerable potential of wearable devices
for real-time and on-site applications, highlighting the self-monitoring
capacity. Future investigations should consider the device’s
operational simplicity with a more straightforward interpretation
of results to make them affordable for the market. The huge potential
of wearable and biodegradable devices enables them as emerging and
powerful platforms for replacing current gold standard methods for
rapid health screening and environmental monitoring in the near future.
The next trend in the technological field of the development and application
of new biodegradable materials to wearable devices should focus on
studies involving the stability, toxicity, and biocompatibility of
the final devices.
β-Hydroxybutyrate (HB) is one of the main physiological
ketone
bodies that play key roles in human health and wellness. Besides their
important role in diabetes ketoacidosis, ketone bodies are currently
receiving tremendous attention for personal nutrition in connection
to the growing popularity of oral ketone supplements. Accordingly,
there are urgent needs for developing a rapid, simple, and low-cost
device for frequent onsite measurements of β-hydroxybutyrate
(HB), one of the main physiological ketone bodies. However, real-time
profiling of dynamically changing HB concentrations is challenging
and still limited to laboratory settings or to painful and invasive
measurements (e.g., a commercial blood ketone meter). Herein, we address
the critical need for pain-free frequent HB measurements in decentralized
settings and report on a reliable noninvasive, simple, and rapid touch-based
sweat HB testing and on its ability to track dynamic HB changes in
secreted fingertip sweat, following the intake of commercial ketone
supplements. The new touch-based HB detection method relies on an
instantaneous collection of the fingertip sweat at rest on a porous
poly(vinyl alcohol) (PVA) hydrogel that transports the sweat to a
biocatalytic layer, composed of the β-hydroxybutyrate dehydrogenase
(HBD) enzyme and its nicotinamide adenine dinucleotide (NAD+) cofactor, covering the modified screen-printed carbon working electrode.
As a result, the sweat HB can be measured rapidly by the mediated
oxidation reaction of the nicotinamide adenine dinucleotide (NADH)
product. A personalized HB dose–response relationship is demonstrated
within a group of healthy human subjects taking commercial ketone
supplements, along with a correlation between the sweat and capillary
blood HB levels. Furthermore, a dual disposable biosensing device,
consisting of neighboring ketone and glucose enzyme electrodes on
a single-strip substrate, has been developed toward the simultaneous
touch-based detection of dynamically changing sweat HB and glucose
levels, following the intake of ketone and glucose drinks.
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