In
order to reduce medical facility overload due to the rise of
the elderly population, modern lifestyle diseases, or pandemics, the
medical industry is currently developing point-of-care and home medical
device systems. Diabetes is an incurable and lifetime disease, accountable
for a significant mortality and socio-economic public health burden.
Thus, tight glucose control in diabetic patients, which can prevent
the onset of its late complications, is of enormous importance. Despite
recent advances, the current best achievable management of glucose
control is still inadequate, due to several key limitations in the
system components, mainly related to the reliability of sensing components,
both temporally and chemically, and the integration of sensing and
delivery components in a single wearable platform, which is yet to
be achieved. Thus, advanced closed-loop artificial pancreas systems
able to modulate insulin delivery according to the measured sensor
glucose levels, independently of patient supervision, represent a
key requirement of development efforts. Here, we demonstrate a minimally
invasive, transdermal, multiplex, and versatile continuous metabolites
monitoring system in the subcutaneous interstitial fluid space based
on a chemically modified SiNW-FET nanosensor array on microneedle
elements. Using this technology, ISF-borne metabolites require no
extraction and are measured directly and continuously by the nanosensors.
Due to their chemical sensing mechanism, the nanosensor response is
only influenced by the specific metabolite of interest, and no response
is observed in the presence of potential exogenous and endogenous
interferents known to seriously affect the response of current electrochemical
glucose detection approaches. The 2D architecture of this platform,
using a single SOI substrate as a top-down multipurpose material,
resulted in a standard fabricated chip with 3D functionality. After
proving the ability of the system to act as a selective multimetabolites
sensor, we have implemented our platform to reach our main goal for
in vivo
continuous glucose monitoring of healthy human subjects.
Furthermore, minor adjustments to the fabrication technique allow
the on-chip integration of microinjection needle elements, which can
ideally be used as a drug delivery system. Preliminary experiments
on a mice animal model successfully demonstrated the single-chip capability
to both monitor glucose levels as well as deliver insulin. By that,
we hope to provide in the future a cost-effective and reliable wearable
personalized clinical tool for patients and a strong tool for research,
which will be able to perform direct monitoring of clinical biomarkers
in the ISF as well as synchronized transdermal drug delivery by this
single-chip multifunctional platform.