Revealing membrane permeability of polymersomes through fluorescence enhancement

In this work, permeability of polymersomes was quantified by fluorescence enhancement. The polymersomes were prepared from poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL), and an acid-sensitive hydrophobic dye borondipyrromethene (BODIPY) was encapsulated into the membrane of polymersomes. H⁺ from trifluoroacetic acid (TFA) would diffuse into the membrane of polymersomes to enhance the fluorescence of BODIPY. Intensity of the enhanced fluorescence could be used for quantifying the H⁺ permeability of polymersomes. In addition, poly(ε-caprolactone) (PCL) was used to control the permeability ability of the membrane. Such quantitative information on the molecular diffusion of polymersomes is of fundamental importance to many of their potential applications, e.g., nanoreactors and drug delivery.