Current technology for blood glucose level monitoring is mainly based on the invasive finger‐prick extraction of a small drop of blood using a lancet and measured via a handheld glucometer, which is not conducive to continuous measurements. Interstitial fluid (ISF) is gaining attention as an alternative biofluid. Its biochemical composition is very similar to that of blood and it can be monitored in a continuous manner via minimally invasive methods that cause no pain and minimize any risk of infection. Herein, a microneedle array (MNA) based transdermal sensing system for the pain free monitoring of ISF glucose is presented. High‐density silicon microneedles (≈9500 microneedles cm−2) are used to prepare a three‐electrode patch for the electrochemical monitoring of glucose. The MNA glucose patch shows very good selectivity when tested in artificial ISF, with a sensitivity of 0.1622 µA mm−1 cm−2 and a detection limit of 0.66 mm. In vivo application of the microneedle array in mice shows that the ISF glucose concentrations obtained with the MNA sensor gave very good correlation with the blood glucose levels determined with a commercial glucometer. This microneedle‐based sensing system hence provides an alternative transdermal diagnostic tool to the invasive existing techniques.

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Parkinson’s disease (PD) is a progressive neurodegenerative disorder involving dopaminergic neurons from the substantia nigra. The loss of dopaminergic neurons results in decreased dopamine (DA) release in the striatum and thus impaired motor functions. DA is one of the key neurotransmitters monitored for the diagnosis and during the progression and treatment of PD. Therefore, sensitive and selective DA detection methods are of high clinical relevance. In this study, a new microfluidic device utilized for electrochemical DA detection is reported. The microfluidic sensing device operates in the range of 0.1–1000 nM DA requiring only ∼2.4 μL sample volume, which corresponds to detectable 240 amol of DA. Using this sensor, we were able to monitor the changes in DA levels in cerebrospinal fluid and plasma of a mouse model of PD and following the treatment of drug l-3,4-dihydroxyphenylalanine.