Scheme 2.

The proposed mechanism of cellular uptake of DNA-Au NPs. In serum containing media, DNA-Au NPs are coated with proteins which reduce nanoparticle interactions with scavenger receptors. Cellular uptake is mediated by the displacement of serum proteins by these receptors. In the absence of serum proteins, these interactions are more easily facilitated, resulting in greater uptake as a result of high DNA density. If the binding to scavenger receptors is inhibited by addition of competitive ligands, then the cellular uptake of nanoparticles is also reduced.