ACS Nano, 2009, 3 (1), pp 234–240

Assembly and Functionalization of DNA−Polymer Microcapsules

Francesca Cavalieri†‡, Almar Postma†, Lillian Lee†and Frank Caruso†*

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 polyA₃₀ or polyT₃₀ (i.e., PNIPAM-A₃₀ or PNIPAM-T₃₀). DNA−polymer microcapsules were obtained by the alternate deposition of PNIPAM-A₃₀ and PNIPAM-T₃₀ 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.