Assembly and functionalization of DNA-polymer microcapsules.

We report the synthesis and characterization of DNA-grafted poly(N-isopropylacrylamide) (PNIPAM) micelles, their assembly into multilayered thin films, and the subsequent generation and poly(ethylene glycol) (PEG) functionalization of DNA-PNIPAM microcapsules. Multilayer films were assembled by sequentially depositing DNA-grafted PNIPAM micelles containing the cDNA sequences polyA(30) or polyT(30) (i.e., PNIPAM-A(30) or PNIPAM-T(30)). DNA-polymer microcapsules were obtained by the alternate deposition of PNIPAM-A(30) and PNIPAM-T(30) onto silica particles, followed by removal of the template core. Upon removal of the silica core particle, shrinkage of between 30 and 50% was observed for the microcapsules. The presence of PNIPAM within the DNA-polymer hybrid film reduces the permeability of the microcapsules to macrosolutes (e.g., dextran) compared with microcapsules made solely of DNA. The hydrophobic core of the DNA-grafted PNIPAM micelles was designed to contain alkyne "click" groups, which were exploited to covalently couple azide-bearing low-fouling PEG to the DNA-PNIPAM microcapsules. The combination of hydrophobic and reactive "click" nanodomains, along with the degradability of DNA, offers a multifunctional and versatile DNA-polymer capsule system that is envisioned to find applications in the controlled delivery of therapeutics.