Visualizing Single-Cell Secretion with Electrochemiluminescence Imaging

Secretory proteins encode cellular states not only through their abundance but also through their intracellular transport before being released. However, visualizing protein secretion behavior with molecular specificity and a low background remains challenging. Here, we report VEGF-responsive electrochemiluminescence (ECL) nanoemitters that enable spatiotemporal mapping of intracellular protein distribution at different stages of the secretion process by integrating a metal-organic framework (MOF) confining Ru(bpy)32+ with DNA tetrahedral gates (DTGs) programmed with aptamers. The MOF core provides bright, stable, and electrically addressable ECL emission, whereas the discrete DTGs regulate coreactant accessibility and prevent premature emission until VEGF recognition triggers gate displacement and restores ECL activity, converting intracellular molecular recognition events to quantitative optical signals. This architecture enables rapid, concentration-dependent, and selective activation, allowing high contrast discrimination of VEGF-rich tumor cells from epithelial cells. Under DFO stimulation, single-cell ECL imaging revealed heterogeneous VEGF upregulation and mapped its progressive redistribution from the perinuclear region to the cell periphery during secretion. This gated ECL platform enables quantitative spatiotemporal visualization of protein secretion behavior beyond the static molecular localization.