Synthesis of poly(2-isopropyl-2-oxazoline)-b-poly(2-phenyl-2-oxazoline)-b-poly(2-isopropyl-2-oxazoline) and its self-assembly into polymersomes: Temperature-dependent aqueous solution behavior

Abstract

This study reports on synthesis of poly(2-isopropyl-2-oxazoline)-b-poly(2-phenyl-2-oxazoline)-b-poly(2-isopropyl-2-oxazoline) (PiPOX-b-PPhOX-b-PiPOX) by a three-step sequential monomer addition through cationic ring opening polymerization (CROP). Self-assembly of PiPOX-b-PPhOX-b-PiPOX was triggered through solvent shifting or double emulsion methods, resulting in formation of polymersomes with hydrophilic and temperature-responsive PiPOX inner/outer coronae and hydrophobic PPhOX membrane. Double emulsion method provided smaller polymersomes with greater colloidal stability. Increasing the temperature of the polymersome solution led to formation of polymersome clusters and this transition was found to be irreversible. Glucose oxidase (GOx) encapsulated polymersomes were used as nanoreactors for GOx/horseradish peroxidase (HRP) cascade reactions. The increase in the rate of the enzymatic reaction with increasing temperature was found to be smaller for the encapsulated enzymes compared to free enzymes.