Reactive oxygen species (ROS) and nicotinamide adenine dinucleotide (NADH) are important intracellular redox-active molecules involved in various pathological processes including inflammation, neurodegenerative diseases, cancer, etc. However, their fast dynamic changes and mutual regulatory kinetic relationship during these biological processes were hard to simultaneously investigate intracellularly at single cells level. 

A dual-channel nanowire electrode integrating two conductive nanowires [1], one functionalized with platinum nanoparticles [2], and the other with conductive polymer [3], was nanofabricated to allow the selective and simultaneous real-time monitoring of intracellular ROS and NADH releases by mitochondria in single living MCF-7 tumoral cells stimulated by resveratrol. The release of ROS was observed to occur a few tenths of a second before that of NADH. Beyond the importance of such an information impossible to acquire by other means, this work established the feasibility of simultaneously monitoring two intracellular species and their kinetics relationships over sub-second time scales. It is expected that this concept will benefit to a deeper understanding of mutual regulatory relationship between crucial intracellular molecular markers during physiological and pathological processes as well as for evaluating medical treatments.

The authors would like to acknowledge support from joint sino-french CNRS IRP NanoBioCatEchem. CA thanks Xiamen University for his Distinguished Visiting Professor position.