Figure 1.

DNA origami nanocapsule design and function. (A) A hinged DNA origami nanocapsule with a HRP payload can be reversibly opened and closed with the help of eight programmable pH-responsive latches. At high pH, the latches are open (a hairpin (orange) and a ssDNA (green) detached) and the capsule halves can move freely, whereas at low pH, the latches form a triplex DNA thus closing the capsule. (B) A schematic figure series depicts the full cycle of capsule function. The open capsule can be loaded with a cargo (yellow sphere with an attachment strand) via hybridization of the anchoring and attachment strands. The loaded cargo can be encapsulated by lowering pH and further displayed by increasing pH. The dynamics of the opening and closing can be followed by FRET analysis when the capsule is equipped by a FRET pair (green and red dyes). (C) TEM images reveal open nanocapsules with a variety of opening angles from completely open to barely ajar structures. Insets show representative structures with corresponding opening angles depicted at the bottom with the same color codes. The monomer capsule yield after folding is 79 ± 2%. (D) Closed nanocapsules under TEM. Insets show zoomed-in representative structures. Scale bars in subfigures C and D are 50 nm. The width of each inset is 60 nm.