A high-performance wearable microneedle sensor based on a carboxylated carbon nanotube-carbon nanotube composite electrode for the simultaneous detection of uric acid and dopamine

Uric acid (UA) and dopamine (DA) are crucial biomarkers in the human body. However, there is limited research on detecting UA or DA in subcutaneous interstitial fluid (SISF), and no studies on their simultaneous detection in SISF. Here, we developed an electrochemical microneedle sensor based on the carboxylated carbon nanotubes/ multiwalled carbon nanotubes (CCNT/CNT) composite electrode for the simultaneous detection of UA and DA. Highly carboxylated CCNT was prepared and mixed with CNT and organosilicon-modified acrylic resin to form the CCNT/CNT composite. The carboxyl functional groups of CCNT enhance the electrode's adsorption of UA and DA, while CNT improves electron conduction. The sensor achieves a wide linear detection range for UA (5-600 mu M) with high sensitivity (7.13 mu A mu M-1 cm(-2)) and linearity (R2 = 0.994), as well as a wide linear range for DA (2-200 mu M) with high sensitivity (13.31 mu A mu M-1 cm(-2)) and linearity (R-2 = 0.994). The sensor achieved simultaneous detection of DA and UA in artificial interstitial fluid (ISF), with sensitivity and linearity remaining nearly unchanged compared to that in PBS, and is not affected by high levels of ascorbic acid (AA). Finally, the sensor successfully detected changes in UA levels in ISF of subjects before and after alcohol consumption in vivo, demonstrating its practical application capabilities. This study presents a practical strategy for detecting human biomarkers characterized by low cost, easy fabrication and excellent performance of electrode materials, and a well-designed microneedle sensor preparation scheme, making it highly promising for further research extension.