Real-time picomolar dopamine biosensing in vitro and in vivo enabled by synergistic Fe-Ni nanoalloy electron transport on N-doped carbon nanotubes

Neurotransmitters are essential chemical messengers enabling proper nervous system function, with dopamine (DA) playing a central role in regulating cognition, emotion, and motor control. Abnormal DA levels are implicated in numerous disorders, underscoring the need for highly sensitive and selective detection strategies in fundamental research and clinical diagnostics. The development of high-performance catalysts is key to enhancing the sensitivity of electrochemical sensors, yet achieving ultra-low detection limits and high specificity for DA remains challenging. Herein, we synthesized a promising alloy catalyst by embedding Fe/Ni alloy nanoparticles onto nitrogen-doped, highly graphitized carbon nanotubes (Fe/Ni/N-CNT) using a one-pot method. The strong synergistic interaction between Fe and Ni atoms improved catalytic activity toward DA oxidation, while N-CNT provided effective conductive support for electron transfer. The Fe/Ni/N-CNT-based DA biosensor exhibited an ultra-low detection limit of 0.5 pM and outstanding anti-interference capability. Its practical applicability was validated across various biological models, including pheochromocytoma (PC12) cells, wound tissues, brain implants, and normal human serum samples. Computational analyses confirmed that the synergistic electron transport between Fe and Ni atoms significantly enhanced catalytic performance. This study demonstrates the rational design and synthesis of heteroatom-doped carbon materials that support the controlled growth of transition metal alloys. The Fe/Ni/N-CNT-based sensing platform offers a promising, low-cost approach for ultrasensitive detection of DA and early-stage clinical diagnostics in biomedical applications.