pH-dependent assembly of DNA-gold nanoparticles based on the i-motif

Oligonucleotides containing stretches of 2 '-deoxycytidine residues were immobilized on 15 nm gold nanoparticles. Under acidic pH conditions a reversible supramolecular assembly is formed, induced by the formation of the tetrameric i-motif structure. The replacement of 2 '-deoxycytidine by 5-propynyl-2 '-deoxycytidine (dC*) leads to novel i-motif structures. Oligonucleotides incorporating multiple residues of dC* were immobilized on 15 nm gold nanoparticles and are able to aggregate into i-motif structures even at non-optimal pH values.