DNA aptamers represent a way to target
cancer cells at a molecular level and continue to be developed with a view to improve treatment and imaging in
cancer medicine. AT11-L0, derived from the DNA sequence AT11, forms a single major parallel G-quadruplex (G4) conformation and exhibits an anti-proliferative activity similar to that of AT11 and
AS1411 aptamers. On the other side,
acridine orange derivatives represent a valuable class of G4
ligands. Herein, we evaluate AT11-L0 G4 as a supramolecular carrier for the delivery of
acridine ligands C3, C5 and C8 to HeLa
cancer cells. The CD titrations suggest no changes in the chiroptical signal upon addition of an excess of
ligands maintaining the parallel G4 topology and C8 stabilizes the structure for more than 20 °C. All the
ligands exhibit high affinity (micromolar range) towards AT11-L0 G4, and the respective complexes against
nucleolin (nanomolar range) suggesting that the
ligands do not negatively affect the recognition of the
nucleolin by AT11-L0 G4. NMR studies showed that AT11-L0 forms a G4 containing four G-tetrad layers.
Ligand C8 binds AT11-L0 G4 through π-π stacking of the
acridine moiety onto the top-tetrad with the involvement of additional interactions with the
ligand's side chain and
iodobenzene ring. In vitro, the complexes lowered the
ligand's cytotoxicity towards non-malignant cells but have a weak inhibitory effect in HeLa
cancer cells, except for the AT11-L0-C5 complex. All complexes are efficiently internalized into
nucleolin-positive HeLa cells. Overall, these results suggest that AT11-L0 can act as an aptamer by targeting
nucleolin and a delivery system of cytotoxic
ligands for
cervical cancer.