Polymersome

Polymersomes are synthetic vesicles formed by the self-assembly of amphiphilic block copolymers in water. Like liposomes, they have an aqueous interior and an enclosed lumen, but their membrane is a bilayer of polymer chains rather than a lipid bilayer. The polymer membrane is typically thicker and more robust, producing greater chemical and mechanical stability and slower permeability, which can extend circulation time and enable loading of larger or more diverse cargoes.

Membranes are composed of amphiphilic block copolymers, with a hydrophilic block that interfaces with water and a hydrophobic block that forms the interior of the membrane. By choosing blocks with different molecular weights and chemistries, researchers tune membrane thickness, stiffness, permeability, and responsiveness. Membrane thickness commonly ranges from several nanometers up to tens of nanometers, far exceeding typical lipid bilayers. Hydrophilic payloads reside in the interior aqueous core, while hydrophobic compounds partition within the membrane.

Polymersomes are typically prepared by film hydration, solvent-switch, or microfluidic methods and characterized by dynamic light scattering, electron microscopy, or cryo-EM. Many polymersomes are engineered to be stimuli-responsive, releasing their cargo in response to changes in pH, redox potential, temperature, or enzymatic activity. Functionalization with targeting ligands or stealth polymers (e.g., PEG) can improve biodistribution and reduce clearance.

Applications include drug delivery, diagnostics and imaging, catalysis, and as nanoreactors or artificial cell models. Common polymer systems include PEG-b-PLA, PEG-b-PCL, and PEG-b-PLGA, among others. While polymersomes offer advantages in stability and tunability, challenges remain for large-scale production, reproducibility, and biocompatibility, requiring careful design and testing for biomedical use.