Spatial Analysis of Reactive Oxygen Species in a 3D Cell Model Using a Sensitive Nanocavity Electrode.

The analysis of biomolecules in a 3D cell model is crucial for the collection of spatial information close to the actual organ. In this work, a highly sensitive platinized open carbon nanocavity electrode is fabricated to investigate reactive oxygen species (ROS) in three regions (proliferating zone, quiescent zone, and necrotic core) of a 3D CT26 cell model. The presence of a nanocavity permits more frequent collisions of ROS on the Pt surface, accelerating electron transfer, and thus pushes the detection limit down to 1 nM. This improved detection sensitivity guarantees the spatial investigation of the ROS distribution in a 3D cell sphere, including a high concentration in the outer proliferating layer even without any external stimulus, a low concentration in the quiescent layer, and almost no ROS at the center. The observation of ROS in the cell sphere without the stimulus reveals the presence of oxygen stress in the 3D cancer cell model, which is obviously different from the previous observation in living cultured 2D cells. This discovery provides direct evidence about the discrepancy about the metabolism in 2D and 3D cells, which could also direct a new study in cell electroanalysis to achieve more actual molecular information in life study.