Sensitive and continuous in situ electrochemical monitoring of multiple neurochemicals using an ultra-soft carbon nanotube fiber sensor

Neurochemicals, such as dopamine (DA), ascorbic acid (AA), and uric acid (UA) serve as critical modulators of neural circuit dynamics in both the central and peripheral nervous systems, and their real-time, in situ monitoring is essential for elucidating neural function and facilitating early diagnosis of neurological disorders. However, conventional in vivo monitoring remains limited by the mechanical mismatch between rigid electrodes and soft neural tissue, as well as the electrochemical detection sensitivity of the electrodes. In this study, we develop a sensitive and multifunctional electrochemical sensing platform based on ultra-soft carbon nanotube fiber electrodes (CNTFEs), which integrate microelectrode with programmable pulsed voltammetric detection for the multiplexed sensing of DA, UA, and AA. Systematic electrochemical evaluations demonstrated that CNTFEs exhibit significantly enhanced sensitivity, compared with conventional gold fiber microelectrodes, with sensitivity improvements of 141-fold for DA detection, 146-fold for UA detection, and 44-fold for AA detection under DPV. In vivo validation via implantation of CNTFEs in the rat striatum demonstrated the sensor's capability for real-time, in-situ detection of externally supplemented DA and AA in brain model. These findings highlight the potential of ultra-soft CNTFE-based sensors for minimally invasive neurochemical monitoring, providing potential opportunity for development of implantable biosensing technologies toward personalized diagnostics in neurological disorders.