Polymerosomes

Polymerosomes are vesicular structures formed by the self-assembly of amphiphilic block copolymers in water, yielding a closed bilayer membrane that encloses an aqueous core. They are the polymeric analogs of liposomes and belong to the broader class of polymersomes. The membrane is typically thicker and more robust than lipid bilayers, resulting in enhanced stability, reduced permeability, and often longer circulation times in vivo.

Membranes are composed of amphiphilic block copolymers, such as poly(ethylene glycol)-block-poly(caprolactone), poly(ethylene oxide)-block-poly(butadiene), or poly(lactic acid)-block-poly(ethylene glycol). The hydrophobic block forms the interior membrane; the hydrophilic block faces the aqueous surroundings. By selecting polymer chemistry and block lengths, researchers tune mechanical properties, membrane thickness, permeability, and loading capacity.

Polymerosomes form by self-assembly driven by solvent exchange, nanoprecipitation, or film hydration, often followed by size control via extrusion or sonication. Hydrophilic cargo (drugs, genes) can be encapsulated within the aqueous core; hydrophobic cargo can partition into the membrane. They are compatible with various encapsulation strategies and can accommodate large loading and sustained release profiles.

Applications include drug delivery, imaging, and theranostics; prolonged circulation, reduced burst release, and controlled release can be achieved with stimuli-responsive polymers that respond to pH, redox potential, temperature, or enzymes. Surface modification with PEG or targeting ligands enables stealth properties and active targeting, improving biodistribution and uptake in specific tissues.

Compared with liposomes, polymerosomes offer higher mechanical stability and design versatility, but may pose challenges in biocompatibility, potential polymer toxicity, and more complex synthesis and scaling.