Fig. 4

Assembly/disassembly of antibody-controlled DNA nanostructures. We have employed here tiles modified to include a single-stranded overhang, or toehold (black domain on the 5′ end of the yellow strand)^18,19 which will be exposed on the external surface of the nanotube. An invader strand can thus bind to the toehold and displace one of the inter-tile bonds, causing the nanotubes to disassemble. a We have re-engineered two orthogonal antibody-controlled DNA circuits that respond to the presence of two different antibodies (anti-DNP and anti-Dig) and release two different outputs (a deprotector strand, to trigger self-assembly and an invader strand, to trigger disassembly). b Fluorescence confocal microscopy images of nanotubes in the absence of both antibodies (left), after addition of anti-DNP antibody (300 nM) (center) and after the addition of anti-Dig antibody (300 nM) (right). c Histograms of nanotube length (mean length) measured from fluorescence microscopy images. In this panel the bars corresponding to mean length = 0 where no nanotubes are observed are shown as white bars for a matter of clarity. The experiments shown in this figure were performed in 1 × TAE, 12.5 mM MgCl₂ at pH 8.0, 25 °C. Nanotubes self-assembly was carried out in the presence of both the anti-DNP and anti-Dig DNA circuits (target duplex, 220 nM and equimolar concentration of the antigen-conjugated input-strands, 440 nM) and at a fixed concentration of the inactive tile (200 nM). The experimental values represent averages of three separate measurements and the error bars reflect the standard deviations. Scale bars for all microscope images, 5 µm.