Self-assembly of polyamines as a facile approach to fabricate permeability tunable polymeric shells for biomolecular encapsulation

Abstract

In this article, the self-assembly of polyamines as a facile approach to fabricate permeability tunable polymeric shells for encapsulation of relatively low molecular weight (LM w) hydrophilic biomacromolecules (M w ≈ 4000 Da) is presented. The entire process is performed in organic solvents within 2 to 4 h to allow for nearly 100% encapsulation yield. The polymeric shells are fabricated by a two-step process: 1) The self-assembly of polyamines (nonionized poly(allylamine) (niPA) or branched nonionized polyethyleneimine (niPEI)) within porous agarose microbeads via an inwards buildup selfassembly process. 2) Stabilization of assembled polyamines either via covalent (cross-linkers) or ionic bonding (complex with nonionized poly(styrene sulfonic acid) (niPSS)). Stable and distinct polymeric shells are formed in both cases. The shell thickness is demonstrated to be tunable within a range of 1 to 14 μm; and as the inwards buildup self-assembly technique is not a self-limiting process, shells with broader thicknesses can be achieved. Also, it is demonstrated that the polymer density of the shell can be tuned. Depending on the fabrication parameters, the resulting polymeric shells have been demonstrated to have different permeability characteristics for relatively LM W dextran (M W≈4000 Da). For example, niPEI shells are observed to have a higher permeability than niPA shells. Therefore, polymeric capsules can be fabricated via this facile approach for either retention of relatively LM w hydrophilic biomacromolecules or designed to passively or responsively release the biomacromolecule payload. This two-step shell fabrication process represent an alternative and facile approach for the fabrication of self-assembled polymeric shells in the fields of capsule-based reactors/sensors and drugs/gene delivery where relatively LM w macromolecules are concerned. © 2011 American Chemical Society.