Sensitive Detection of MMP9 Enzymatic Activities in Single Cell-Encapsulated Microdroplets as an Assay of Cancer Cell Invasiveness

Matrix metalloproteinases (MMPs) are typically up-regulated in cancer cells, and play a critical role in assisting metastasis by the breakdown of the extracellular matrix. Here we report an effective strategy for cell invasiveness assay by integrating MMP9 functional activity analysis with single cell-encapsulated microdroplets. A flow focusing capillary microfluidic device has been assembled using “off-the-shelf” fluidic components for high-throughput generation of microdroplets. Tumor cells, MMP9 specific peptides, and other cofactors can be loaded into the device and encapsulated into individual droplets as dynamic microreactors for proteolytic cleavage of the substrate. This design allows for rapid and robust detection of MMP9 enzymatic activities by fluorescent signals in a few minutes. It represents the first demonstration of quantifying MMP9 enzymatic activities at the single cell level with a high throughput performance. This new technique promises functional evaluation of cancer cell invasiveness for important diagnostic or prognostic applications