Modulating the Bond Strength of DNA–Nanoparticle Superlattices

A method is introduced for modulating the bond strength in DNA-programmable nanoparticle (NP) superlattice crystals. This method utilizes noncovalent interactions between a family of [Ru(dipyrido[2,3-a:3',2'-c]phenazine)(N-N)2](2+)-based small molecule intercalators and DNA duplexes to postsynthetically modify DNA-NP superlattices. This dramatically increases the strength of the DNA bonds that hold the nanoparticles together, thereby making the superlattices more resistant to thermal degradation. In this work, we systematically investigate the relationship between the structure of the intercalator and its binding affinity for DNA duplexes and determine how this translates to the increased thermal stability of the intercalated superlattices. We find that intercalator charge and steric profile serve as handles that give us a wide range of tunability and control over DNA-NP bond strength, with the resulting crystal lattices retaining their structure at temperatures more than 50 °C above what nonintercalated structures can withstand. This allows us to subject DNA-NP superlattice crystals to conditions under which they would normally melt, enabling the construction of a core-shell (gold NP-quantum dot NP) superlattice crystal.