We next investigated if the hairpins in the 258HP origami could be loaded with a TFO by incubating the raw folding mixtures with progressively increasing concentrations of an unmodified 13-nt TFO. Loading and AGE analysis were performed at pH 4.8 to drive the formation of C + -GC Hoogsteen bonds in the TFO-hairpin complexes (Fig ). Significant upward shifts in mobility for the origami and for the free HP staples were observed at [TFO]=10 μM and [TFO]=100 μM, indicating TFO binding (compare lanes 1, 3 and 4), whilst no significant shift was observed at the lower [TFO] = 1 μM (lane 2). We then repeated the AGE experiment using a dual-labelled TFO carrying psoralen at its 5′ end and a C6-NH2 group at its 3′ end (pso-TFO-C6-NH2) (Fig ). We again observed upward shifts in the mobility of the nanostructure and free HP-staples at the same concentrations seen with the unmodified TFO (compare lanes 5, 7, and 8). The shift of the origami by TFO-C6-NH2 was more pronounced compared to the effect of unmodified TFO on account of the higher molecular mass and charge of the 5′ and 3′ modifications on TFO. These results indicate that HP-bearing origami are targetable with both unmodified and modified TFOs.