The preparation of layer-by-layer (LbL) polymer capsules stabilized by a combination of copper-catalyzed azide-alkyne cycloaddition (CuAAC, "click chemistry") and disulfide cross-linking is reported. The capsules obtained possess gated permeability due to the reversible nature of the disulfide cross-linking. Poly(methacrylic acid) (PMA) was modified with different ratios of alkyne and protected thiol functionalities (PMAAlk,SH). Exploiting hydrogen bonding interactions, multilayered films were prepared by the alternate deposition of PMAAlk,SH (hydrogen bonding donor) and poly(N-vinylpyrrolidone) (PVPON; hydrogen bonding acceptor), yielding stable PMAAlk,SH capsules. Capsule pH responsive behavior and permeability, using a series of different size and labeled dextrans, were investigated in both the "closed" state (disulfide cross-linking intact) and "open" state (free thiol groups). To demonstrate the potential of these gateable systems, post-loading studies with fluorescent 45-base pair (bp) linear double-stranded (ds) DNA were performed. Fluorescence studies revealed the potential of these capsules to reversibly encapsulate cargo: cleavage and reformation of the disulfide groups resulted in reversible permeability to the DNA.
- Disulfide chemistry