Ionic liquid functionalized metal-organic framework nanowires for sensitive and real-time electrochemical monitoring of nitric oxide released from living cells.

Sensitive, selective, and real-time detection of nitric oxide (NO) is still challenging due to its rapid diffusion, short half-life, and low concentration in living systems. Herein, we synthesized well-defined ultralong metal-organic framework nanowires (MOFNWs) that were further uniformly covered with gold nanoparticle (AuNPs) and ionic liquids (ILs) and applied these NWs to detect and monitor NO released from living cells. In this system, ILs and AuNPs act as excellent catalysts for electrochemical oxidation of NO. By taking advantage of the synergetic effect between ILs, AuNPs and MOFNWs, the composite (IL@Au@MOFNWs) sensor probe displays excellent electrocatalytic activity toward NO oxidation with a detection limit as low as 2.28 nM for NO detection. The high levels of selectivity and sensitivity to NO in complex biological environments can be attributed to the exposed Ni active sites, high ion-electron transport rates of NWs, and the high conductivity of ILs and AuNPs. Furthermore, the IL@Au@MOFNWs offer a biocompatible sensing interface enabling rapid real-time monitoring of NO released from living cells by drug stimulation. Collectively, these results demonstrate that functionalized ultralong MOFNWs exhibit a remarkable ability to quantify NO levels in cells and could therefore provide new potential of this sensor in electrochemical detection of living bodies.