Enzyme-filled stable polymeric capsules (polymersomes) that are permeable to low-molecular-weight (pro-fluorescent) substrates can be sorted based on the activity of encapsulated enzymes using flow cytometry (see image). Enzymatic activity is screened by the build-up of fluorescent product that is prevented from leaking out by co-encapsulation of a trapping agent.
Nallani, M., Woestenenk, R., de Hoog, H-P., van Dongen, S. F. M., Boezeman, J., Cornelissen, J. J. L. M., ... van Hest, J. C. M. (2009). Sorting catalytically active polymersomes by flow cytometry. Small, 5(10), 1138-1143. https://doi.org/10.1002/smll.200801204