Nanoaggregate formation of poly(ethylene oxide)-b-polymethacrylate copolymer induced by cationic anesthetics binding

Abstract.

We prepared nanoaggregates of poly(ethylene oxide)-b-polymethacrylate (PEO-b-PMA) in which the PMA block was electrically neutralized with cationic anesthetics. The anesthetics employed are dibucaine, tetracaine, and procaine. They self-assembled to form micelle-like nanoaggregates comprised of core of neutralized polyions surrounded by the PEO corona. The formation of the nanoaggregates is confirmed by dynamic light scattering, scanning electron microscopy, turbidimetry, and fluorescence spectroscopy. It was found that the properties of the aggregates strongly depend on the hydrophobicity of the anesthetics and that hydrophobic interaction as well as electrostatic interaction plays an important role in binding between the PMA block and the anesthetics. The aggregate induced by dibucaine has a highly viscous interior, whereas that induced by tetracaine has a fluid interior due to its less hydrophobic effect. Procaine did not give the aggregates probably due to its low hydrophobicity. The significance of these new types of nanoaggregates is that they can incorporate ionic drugs into their cores in aqueous solutions, in considerable contrast to conventional polymer micelles in which only hydrophobic species can be incorporated into the core. The potential applications of the present systems include a carrier for ionic drugs.