Spatial Visualization of Secreted Lysyl Oxidase Activity from Single Living Cells via Label-Free Electrochemiluminescence Microscopy

Spatially resolved analysis of secreted enzyme activity at the single-cell level is critical for understanding extracellular matrix (ECM) remodeling in cancer. This study introduces a label-free electrochemiluminescence (ECL) microscopy method that visualizes lysyl oxidase (LOX) activity secreted by individual tumor cells with subcellular resolution. The approach integrates ECM-localized enzymatic reactions with ECL signal amplification, where LOX-generated hydrogen peroxide enhances luminol-based ECL without external labels. The resulting ΔECL signal directly maps enzyme activity and its spatial heterogeneity across the pericellular region. This platform enables real-time monitoring of LOX inhibition dynamics, phenotypic classification of LOX activity within a breast cancer cell population, and visualization of asymmetric LOX secretion patterns that guide tumor cell migration. These capabilities offer mechanistic insights into ECM-driven tumor invasion and highlight the utility of ECL imaging for high-content single-cell analysis.