A fully integrated non-invasive flexible biosensor based on vertically grown gold nanowire forests for continuous wireless monitoring of dopamine.

Dopamine (DA) is a phenolic neurotransmitter secreted in the central nervous system, plays vital physiological functions in humans. Given that abnormal DA release is associated with neurological diseases and depression, real-time monitoring of DA levels is essential for elucidating its significance under different physiological conditions. We developed a novel portable and wearable electrochemical biosensor based on vertical gold nanowires (v-AuNWs) electrode for the continuous monitoring of DA in human sweat. The v-AuNWs biosensor exhibited high sensitivity, flexibility and specificity toward DA, with a linear detection range of 2 nM to 1 μM and a limit of detection (LOD) of 2.73 ± 0.47 nM in artificial sweat. Notably, v-AuNWs modified electrode demonstrated promising biocompatibility with PC12 cells. When PC12 cells were stimulated with ghrelin, an increased electrochemical response corresponding to DA redox was observed, indicating DA secretion from PC12 cells. In practical applications, the fully integrated Ecoflex-v-AuNWs biosensor was attached to the skin of human volunteers for real-time wireless monitoring of DA in sweat. The results revealed that volunteer sweat DA concentrations increased under different physiological conditions to reach 8.88 ± 2.63 nM after foot soak, 18.03 ± 1.40 nM during running and 36.67 ± 3.90 nM during running after milk tea consumption, respectively. These results indicates that running is correlated with elevated DA levels, which may be associated with positive emotion regulation. This epidermal biosensor provided a feasible, non-invasive approach for the monitoring of DA in clinical neurological health assessment.