title: Formation of polymeric toroidal-spiral particles.
abstract: Compared to spherical matrices, particles with well-defined internal structure provide large surface to volume ratio and predictable release kinetics for the encapsulated payloads. We describe self-assembly of polymeric particles, whereby competitive kinetics of viscous sedimentation, diffusion, and cross-linking yield a controllable toroidal-spiral (T-S) structure. Precursor polymeric droplets are splashed through the surface of a less dense, miscible solution, after which viscous forces entrain the surrounding bulk solution into the sedimenting polymer drop to form T-S channels. The intricate structure forms because low interfacial tension between the two miscible solutions is dominated by viscous forces. The biocompatible polymer, poly(ethylene glycol) diacrylate (PEG-DA), is used to demonstrate the solidification of the T-S shapes at various configurational stages by UV-triggered cross-linking. The dimensions of the channels are controlled by Weber number during impact on the surface, and Reynolds number and viscosity ratio during subsequent sedimentation. We anticipate applications of the T-S particle in drug delivery, wherein diffusion through these T-S channels and the polymer matrix would offer parallel release pathways for molecules of different sizes. Polyphosphate, as a model macromolecule, is entrained in T-S particles during their formation. The in vitro release kinetics of polyphosphate from the T-S particles with various channel length and width is reported. In addition, self-assembly of T-S particles occurs in a single step under benign conditions for delicate macromolecules, and appears conducive to scaleup.
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States.
authors.forename: Vishal
authors.initials: V
authors.lastname: Sharma
authors.forename: Magdalena
authors.initials: M
authors.lastname: Szymusiak
authors.forename: Hao
authors.initials: H
authors.lastname: Shen
authors.forename: Ludwig C
authors.initials: LC
authors.lastname: Nitsche
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D007700:Kinetics; D011108:Polymers / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D011108:Polymers