Sensitive Detection of Single-Cell Secreted H2O2 by Integrating a Microfluidic Droplet Sensor and Au Nanoclusters.

As an important signaling molecule, hydrogen peroxide (H2O2) secreted externally by the cells influences cell migration, immunity generation, and cellular communications. Herein, we have developed a microfluidic approach with droplets in combination with Au nanoclusters for the sensitive detection of H2O2 secreted by a single cell. Isolated in the ultrasmall volume (4.2 nL) of a microdroplet, single-cell secreted H2O2 can initiate dramatic fluorescence changes of horseradish peroxidase-Au nanoclusters. We have demonstrated an ultrahigh sensitivity (200-400 attomole H2O2 directly measured from a single cell) with good specificity. It offers a useful research tool to study the cell-to-cell differences of H2O2 secretion at the single-cell level.