Plasma-treated carbon sensor coupled to a microfluidic platform for the determination of levodopa in sweat

Parkinson’s disease (PD) is characterized by the progressive depletion of dopamine (DA), a key neurotransmitter involved in the regulation of voluntary movement. Levodopa (L-DA), the gold-standard treatment for PD, effectively restores DA levels; however, its clinical efficacy is limited by a short half-life and a narrow therapeutic window, often resulting in motor and non-motor fluctuations. Therefore, accurate monitoring of L-DA levels in patients with PD is essential to optimize therapeutic outcomes. Herein, a fully integrated microfluidic platform for the detection of L-DA in sweat based on a plasma-activated carbon sensor is reported. The core of this technology is a single-step oxygen plasma treatment deliberately designed to serve a dual purpose: enabling robust sealing of the PDMS microfluidic layers while simultaneously activating the carbon electrode surface. This strategy yields a substantial enhancement in electrocatalytic performance without the need for complex nanomaterials or biorecognition elements, thereby simplifying fabrication and improving scalability. The resulting plasma-activated sensor exhibits a 22-fold signal amplification compared to untreated electrodes and achieves a limit of detection (LoD) of 4 μM in synthetic human sweat, underscoring its potential for wearable and point-of-care applications.