DNA Loading and Release Using Custom-Tailored Poly(l-lysine) Surfaces

This Article describes the generation and study of surfaces modified with custom-crafted poly(l-lysine) (PLL) coatings for use in the loading and delivery of single-stranded DNA (ssDNA). The experimental strategy utilizes bidentate dithiol adsorbates to generate stably bound azide-terminated self-assembled monolayers (SAMs) on gold possessing an oligo(ethylene glycol) (OEG) spacer. Consequent to the molecular assembly on gold, the azide termini are covalently attached to a maleimide linker moiety via a copper-catalyzed azide-alkyne "click" reaction. Functionalization with maleimide provides a platform for the subsequent attachment of cysteine-terminated poly(l-lysine) (PLL), thus forming a suitable surface for the loading of ssDNA via electrostatic interactions. In efforts to maximize DNA loading, we generate SAMs containing mixtures of short and long PLL segments and explore the DNA-loading capability of the various PLL SAMs. We then use thermal increases to trigger the release of the ssDNA from the surface. By examining the loading and release of ssDNA using these new two-dimensional systems, we gain preliminary insight into the potential efficacy of this approach when using three-dimensional gold nanostructure systems in future gene-delivery and biosensing applications.