Design and evaluation of dual-functional aptamer-peptide conjugates as a platform for targeted cancer therapy.

AS1411 is a G-rich DNA aptamer that exhibits intrinsic antitumor activity through selective binding to nucleolin, a protein overexpressed in many cancers. Beyond its cytotoxic effects, AS1411 can also serve as an effective targeting ligand for the delivery of therapeutics with poor cellular uptake, including peptide-based drugs. One such candidate is the pro-apoptotic peptide KLA, which selectively disrupts mitochondrial membranes and induces apoptosis upon internalization. In this study, AS1411-KLA conjugates were designed and synthesized using strain-promoted azide-alkyne cycloaddition chemistry, incorporating protease-cleavable peptide linkers to enable intracellular release of both the aptamer and peptide as independent active units. Circular dichroism analysis showed that, in all constructs, the AS1411 domain preserved the characteristic G-quadruplex structural features, while surface plasmon resonance experiments revealed that all conjugates retained nucleolin binding. The biological activity of the conjugates was evaluated in MCF-7 breast cancer cells and in non-tumorigenic MCF-10A cells, and compared with that of the individual aptamer and peptide. One conjugate displayed an enhanced antiproliferative effect compared to the unconjugated components, underscoring the therapeutic potential of this modular design. Overall, this work demonstrates the potential of aptamer-peptide conjugates as a promising strategy for next-generation targeted cancer therapeutics, combining targeted delivery with synergistic therapeutic effects.