Flexible microfluidics-integrated electrochemical system for detection of tumor necrosis factor-alpha under continuous flow of sweat
Moritz Ploner, Bajramshahe Shkodra, Lara Franchin, Antonio Altana, Mattia Petrelli, Martina Aurora Costa Angeli, Giuseppe Ciccone, Tobias Antrack, Lia Vanzetti, Rakesh Rajendran Nair, R. Canteri, Stefano Bonaldo, A. Paccagnella, Hans Kleemann, D. Resnati, Paolo Lugli, Ahmet Erten, Luisa Petti
Abstract
Cytokines play a vital role in immune system signaling, making their detection crucial for continuous health monitoring. Among the various cytokines, tumor necrosis factor-alpha (TNF-α) stands out as a key regulator of the immune response. Notably, TNF-α can be detected in sweat at concentrations as low as pg/mL, with levels strongly correlated with those in blood. Despite its importance, sensitive, wearable, and continuous monitoring of TNF-α in sweat remains limited. To address this gap, this study presents a flexible electrochemical sensor integrated into a microfluidic system for the sensitive and selective detection of TNF-α under continuous sweat flow. First, we present the fabrication of two distinct, miniaturized designs of flexible screen-printed carbon three-electrode platforms, which are subsequently biofunctionalized with gold nanoparticles (AuNPs) coated with TNF-α-specific thiolated aptamers. Next, we compare the two geometrically distinct AuNP-aptamer-functionalized sensors, utilizing experimental and novel simulation-based characterization techniques. Finally, the sensors are integrated into a custom-built microfluidic system enabling the detection of TNF-α ranging from 0.2 to 1000 pg/mL under constant artificial sweat flow conditions, exhibiting high selectivity with negligible responses to non-specific analytes. These findings highlight the feasibility of integrating wearable cytokine sensors for detecting TNF-α under continuous sweat flow conditions, achieving clinically relevant sensitivity within the pg/mL range.