title: Controlling interlayer diffusion to achieve sustained, multiagent delivery from layer-by-layer thin films.
abstract: We present the fabrication of conformal, hydrolytically degradable thin films capable of administering sustained, multiagent release profiles. Films are constructed one molecular layer at a time by using the layer-by-layer, directed-deposition technique; the subsequent hydrolytic surface erosion of these systems results in the release of incorporated materials in a sequence that reflects their relative positions in the film. The position of each species is determined by its ability to diffuse throughout the film architecture, and, as such, the major focus of this work is to define strategies that physically block interlayer diffusion during assembly to create multicomponent, stratified films. By using a series of radiolabeled polyelectrolytes as experimental probes, we show that covalently crosslinked barriers can effectively block interlayer diffusion, leading to compartmentalized structures, although even very large numbers of ionically crosslinked (degradable or nondegradable) barrier layers cannot block interlayer diffusion. By using these principles, we designed degradable films capable of extended release as well as both parallel and serial multiagent release. The ability to fabricate multicomponent thin films with nanoscale resolution may lead to a host of new materials and applications.
authors.affiliation: *Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 66-546, Cambridge, MA 02139; and.
authors.forename: Kris C
authors.initials: KC
authors.lastname: Wood
authors.affiliation: *Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 66-546, Cambridge, MA 02139; and.
authors.forename: Helen F
authors.initials: HF
authors.lastname: Chuang
authors.affiliation: *Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 66-546, Cambridge, MA 02139; and.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Batten
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin, 1415 Engineering Drive, Madison, WI 53706.
authors.forename: David M
authors.initials: DM
authors.lastname: Lynn
authors.affiliation: *Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 66-546, Cambridge, MA 02139; and hammond@mit.edu.
authors.forename: Paula T
authors.initials: PT
authors.lastname: Hammond