Scheme 1. Two Approaches to the Synthesis of RNA–SNAs, Which Consist of a NP Core, Duplexed siRNA (Thiolated Sense RNA Shown in Blue and Complementary Anti-Sense (AS) RNA Shown in Green), and a PEG-Thiol Passivating Molecule.

(A) In the backfill method of synthesis, RNA is first adsorbed on the AuNP surface, and PEG is added subsequently. (B) Alternatively, RNA and PEG may be co-adsorbed to the AuNP.