Production of M13 bacteriophage single-stranded DNA was according to Douglas et al.’s methods36. Briefly, JM109 E. coli were cultured in 2 × YT medium (5 mM MgCl2) and placed in a shaker at 37 °C. When the optical density (OD 600) reached 0.5, M13 phages (p7249) were mixed with the bacteria, and then cultured for 5 h. The culture was collected and centrifuged at 6000 × g for 30 min to remove the bacteria pellets. NaCl (30 g/l) and PEG (40 g/l) were added to the supernatant (containing phages), and the mixture was incubated on ice for 1 h. The phage pellet was collected after 30 min centrifugation at 10,000 × g, and suspended in Tris-HCl (10 mM, pH 8.5). The phage solution was incubated with NaOH (0.2 M) and SDS (1%) at 25 °C for 3 min. After the addition of potassium acetate (3 M, pH 5.5), the solution was incubated on ice for 10 min and centrifuged (12,000 × g, 30 min). The ssDNA (7249 nt) containing supernatant was collected and precipitated in ethanol (70%) on ice for 2 h. After centrifuging at 12,000 × g for 30 min, the DNA pellet was collected and washed in ethanol (70%) and then resuspended in Tris-HCl (10 mM, pH 8.5). The concentrations of ssDNA were determined by UV–Vis spectrometry (UV-2450, Shimadzu, UVProbe 2.61 software).

Rectangular shaped DNA origami structures were assembled according to Rothemund’s methods19 with several modifications. The positions and sequences of the staple/functional strands are shown in different colors in Supplementary Figs. (17, 14) and Supplementary Table 2. A molar ratio of 1:5:5 among the long viral ssDNA M13mp18 (20 nM), the short staple strands (100 nM) and the capture strands (100 nM) was used. DNA origami was annealed and assembled in TAE-Mg2+ buffer (Tris, 40 mM; Acetic acid, 20 mM; EDTA, 2 mM; and Magnesium acetate, 12.5 mM; pH 8.0) in an Eppendorf thermocycler (Eppendorf China) by slowly cooling from 95 °C to 25 °C at a rate of 10 min/°C. The resulting rectangular DNA origami structures were separated from excess staple strands using Amicon Ultra-0.5 ml 100 kD centrifugal filters (Millipore). The purified origami solution was collected and characterized using 1% agarose gel electrophoresis and atomic force microscopy (AFM).

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