# Leaky by Design: Unlocking Polymersome Permeability Using Moderately Hydrophobic Polymer Blocks

## TL;DR

This paper shows that certain polymer vesicles can naturally allow small molecules to pass through, making them useful for enzyme reactions without added components.

## Contribution

The study introduces polymersomes with inherent permeability due to moderately hydrophobic polymer blocks, eliminating the need for artificial transport systems.

## Key findings

- Polymer vesicles with poly(butylene oxide) show intrinsic permeability to small molecules.
- Enzymes like horseradish peroxidase can be encapsulated and remain functional within the vesicles.
- The vesicles allow passage of enzyme substrates and products, enabling catalytic reactions.

## Abstract

Polymersome nanoreactors,
vesicular assemblies formed
from amphiphilic
block copolymers, provide a versatile platform for compartmentalized
catalysis and the construction of biomimetic systems. While extensive
efforts have focused on the encapsulation of enzymes within such constructs,
reports of vesicles displaying intrinsic membrane permeability remain
unusual. Typically, selective transport across polymersome membranes
requires the incorporation of channel proteins or other porogenic
components. Conversely, we herein demonstrate that polymer vesicles
comprising poly­(butylene oxide) as the hydrophobic segment exhibit
inherent permeability to small molecules without the need for artificial
machineries, possibly governed by moderate hydrophobicity of this
polymer and consequently hydration of the membrane. Synthesis and
detailed characterization of diblock and triblock copolymers containing
poly­(butylene oxide) and poly­(glycidol), respectively, as hydrophobic
and hydrophilic blocks are first demonstrated; the self-assembly of
the chains into polymer vesicles and their inherent permeability to
disparate small molecules are subsequently highlighted. Notably, we
further reveal that such vesicles can be conveniently loaded with
a model enzyme (horseradish peroxidase), which remains entrapped in
the aqueous lumen. Using a well-established colorimetric assay, we
show that the vesicles are also permeable to small-enzyme substrates
and products, and therefore, the reported strategy can be applied
to a wide range of enzymes and functional proteins for the design
of simple permeable nanoreactors for enzyme-mediated catalysis.