Sorting catalytically active polymersome nanoreactors by flow cytometry

Abstract

Flow cytometry is a powerful technique for high-throughput,

fluorescence-activated screening and sorting of cells (FACS).

This methodology has been extended by Griffiths to the

screening of water-in-oil microdroplets filled with an in vitro

protein expression system.[1–6] The catalytic gene product was

detected by the transformation of a co-encapsulated profluorescent

substrate into a fluorescent product. Here we

report a strategy that involves a versatile one-step preparation

procedure of enzyme filled porous and stable polymeric

capsules (polymersomes). Since the pores of the capsules are

small enough to keep enzymes in, whereas these are

sufficiently large to allow (profluorescent) substrates to enter,

enzyme activity screening can be performed by the build-up of

fluorescence, followed by FACS. To prevent the substrate

from diffusing out of the capsules, a trapping agent was added

inside the capsule. With this technology we were able to

separate enzymatically active polymersomes from non-filled

or non-active polymersomes.