Aggregation-free DNA nanocage/Quantum Dot complexes based on electrostatic adsorption

Fabrication of DNA/Quantum Dot (QD) complexes making use of electrostatic adsorption forces has advantages of the cost-efficiency and simplicity. To obtain aggregation-free complexes, high molecular weight polymers or the purposefully designed ligands are commonly employed as a bridge between DNA and QDs, which limits their applications in practice. In this work, DNA/QDs complexes were obtained using electrostatic adsorption between cysteamine stabilized CdTe QDs and self-assembled DNA nanocages. Zeta potential, dynamic light scattering and gel electrophoresis measurements demonstrated their aggregation-free state, different from the cases where single-stranded and double-stranded DNAs were used. The appearance of aggregation-free complexes in the case of DNA nanocages was ascribed to their 3D rigid structure. Förster resonance energy transfer (FRET) was demonstrated for the complexes of Cy3 labeled DNA nanocages and QDs, pointing out on the close proximity of these building blocks.