Characterization of EpCAM Apt-DOX conjugates. (A) Schematic illustration of the hybrid RNA-DNA EpCAM aptamer. (B) AFM analysis of intercalation between the aptamer and DOX. Based on cross section analysis, the size of aptamers were around 1.3 nm, while the conjugated structure has size of around 2.5 nm. (C) The fluorescence quenching of 10 μM DOX after 30 min incubation with an increasing molar ratio of aptamer-to-DOX (0.001, 0.002, 0.004, 0.006, 0.1, 0.6 and 1). (D) Time-dependent release of DOX from aptamer conjugates at pH 7.4 in vitro. The “Free DOX” sample was used to demonstrate the ability of the DOX dissociated from the aptamer can cross the membrane of the dialysis device. (E) pH-dependent release of DOX from aptamer conjugates at pH of 5.0, 7.4 and 8.0. Data shown are means ± SEM (n=3).