Engineering a cell-surface aptamer circuit for targeted and amplified photodynamic cancer therapy.

Photodynamic therapy is one of the most promising and noninvasive methods for clinical treatment of different malignant diseases. Here, we present a novel strategy of designing an aptamer-based DNA nanocircuit capable of selective recognition of cancer cells, controllable activation of photosensitizers, and amplification of photodynamic therapeutic effect. The aptamers can selectively recognize target cancer cells and bind to the specific proteins on cell membranes. Then the overhanging catalyst sequence on the aptamer can trigger a toehold-mediated catalytic strand displacement to activate the photosensitizer and achieve amplified therapeutic effect. The specific binding-induced activation allows the DNA circuit to distinguish diseased cells from healthy cells, reducing damage to nearby healthy cells. Moreover, the catalytic amplification reaction will only take place close to the target cancer cells, resulting in a high local concentration of singlet oxygen to selectively kill the target cells. The principle employed in this study demonstrated the feasibility of assembling a DNA circuit on cell membranes and could further broaden the utility of DNA circuits for applications in biology, biotechnology, and biomedicine.