Well-defined and stable nanomicelles self-assembled from brush cyclic and tadpole copolymer amphiphiles: a versatile smart carrier platform

Abstract

This study reports the first well-defined and stable nanomicelles (20−30 nm in diameter) self-assembled from amphiphilic brush (comb-like) cyclic and tadpole-shaped copolymers composed of hydrophobic n-decyl and hydrophilic 2-(2-methoxyethoxy)ethoxy)ethyl bristle blocks based on a poly(glycidyl ether) backbone. The micelle formation behaviour and structural details were investigated by synchrotron X-ray scattering analysis in a rigorous and complementary manner. The amphiphilic brush cyclic topology facilitates more compact and stable aggregation behaviour in the micelle core and a more densely packed corona, which prevents intermicellar aggregation. The presence of a hydrophobic component with brush cyclic topology inside the core is identified as the primary micelle stabilizing factor, enabling stable core aggregation and sharper core-corona interface formation. The presence of a hydrophilic brush cyclic component in the corona is determined as the secondary micelle stabilizing factor, helping nullify the corona penetration by polymer chains from other micelles and ultimately prevent the intermicellar aggregation-mediated collapse of the micellar structure. Overall, the brush cyclic topology was confirmed to be beneficial for forming highly stable nanomicelles with an extremely narrow (pseudo-monodisperse) size distribution compared with conventional linear topology and tadpole topologies. All the results of this study provide a unique opportunity for designing advanced functional high-performance amphiphilic materials for nanomicelles that are unattainable by other conventional methods and broadening their applications in various fields, including drug delivery, biomedical imaging, foods, cosmetics, smart coatings, photonics and molecular electronics. Choosing surfactants in brush cyclic and tadpole topologies makes it easier to control the size of micelles for smart delivery. Micelles form through the self-assembly of amphiphilic chains into tiny spheroids. They are promising carriers for nanomedicine because they can encapsulate and keep pharmaceuticals safe until reaching their destination. Moonhor Ree from POSTECH in Korea and colleagues now report a reliable method for producing micelles that are 20 to 30 nanometers wide – an ideal size for entry into cancerous tissue. Using synchrotron X-rays, the team showed that water-repelling bristle units on a poly(glycidyl ether)-based micelle encouraged unusually dense packing due to their bristle structures, while hydrophilic bristle units sealed the micelle's surface from any gaps. Optimizing brush block copolymer amphiphile as a cyclic and tadpole topology gave micelles with particularly narrow size distributions. Well-defined and stable nanomicelles (20−30 nm in diameter) were demonstrated for the first time by the self-assembly of amphiphilic brush (comb-like) cyclic and tadpole-shaped copolymers based on a poly(glycidyl ether) backbone. In particular, the brush cyclic topology formed the most compact and most stable nanomicelles with an extremely narrow (pseudo-monodisperse) size distribution, which are unattainable by other conventional means. This study provides a unique opportunity for designing advanced functional high-performance amphiphile materials for micelles and facilitating their applications in various fields.