The authors wish to thank S. Douglas for extremely valuable discussions and advice, and all the members of the Bachelet lab for helpful discussions and work. This work is supported by grants from the Faculty of Life Sciences and Institute of Nanotechnology &#38; Advanced Materials at Bar-Ilan University.

1. Preparation of Staples Pool Mixture
<ol>
	<li>Order lyophilized DNA nanorobot staples on 96-well plates as listed in Table 1 (see Materials) and normalize to 10 nmol. For a detailed description of the design and architecture of the DNA nanorobot see Ben-Ishay et al.14 and Douglas et al.15).</li>
	<li>Reconstitute each staple well with DNase/RNase-free ultrapure to a concentration of 100 &#181;M. For staples normalized to 10 nmol, reconstitute with 100 &#181;l of ultrapure water.</li>
	<li>Pool together 20 &#181;l of each staple using a multichannel pipettor and a sterile 55 ml solution basin. 
	Note: Since the nanorobot shape is comprised of 254 staple strands (including Core, Edges, Handles and Guides sequences, Table 1), the concentration of each of the staples in the staples pool is 394 nM. Removing staples from the staple pool, or adding some at different volumes, may reduce the yield considerably, or otherwise result in unfolded aggregates.</li>
</ol>
2. Preparation of Fabrication Reaction Mixture
<ol>
	<li>For a standard reaction mixture use 40 &#181;l of M13mp18 viral genome circular single strand DNA, corresponding to 4 pmol of scaffold DNA (100 nM stock solution, see Materials). Final concentration of scaffold in the fabrication mixture is 20 nM, final volume 200 &#181;l.
	<ol>
		<li>Adjust the amount of scaffold DNA according to specific needs; however, keep the final concentration of scaffold DNA in the reaction mixture at a constant 20 nM.</li>
	</ol>
	</li>
	<li>Add staples to reach a scaffold to staples ratio of 1 to 10, respectively. For a 20 nM scaffold DNA concentration, each of the 254 staples&#8217; final concentration is 200 nM. For a 200 &#181;l final reaction volume add 102 &#181;l of the staples pool mixture (section 1.2).
	<ol>
		<li>Add specific Gate sequences separately to the folding reaction mixture at this time. These oligos are ordered separately and require HPLC purification. Ensure that Gate oligos are present in a 1:10 scaffold to Gate sequence ratio, i.e. 200 nM of each oligo for a 20 nM scaffold concentration. For a 200 &#181;l folding reaction volume, add 0.4 &#181;l for each of the four Gate oligo at a 100 &#181;M stock concentration.</li>
	</ol>
	</li>
	<li>Add 10x TAE stock buffer to reach a final concentration of 1x TAE (40 mM Tris-Acetate, 1 mM EDTA). For a 200 &#181;l folding reaction volume, add 20 &#181;l of 10x TAE.</li>
	<li>Add 1 M MgCl2 to a final concentration of 10 mM. For a 200 &#181;l folding reaction volume, add 2 &#181;l of 1 M MgCl2.</li>
	<li>Add 36 &#181;l of DNase/RNase free ultrapure water to a reach a final volume of 200 &#181;l.</li>
	<li>Vortex and aliquot 100 &#181;l samples into PCR vials. 
	Note: Consult thermal cycler specification regarding the maximum reaction volumes to be used. Reducing the volume to meet these limits will not reduce the yields obtained. Reaction volumes above the maximum specified will jeopardize the yields.</li>
</ol>
3. Temperature Annealing Ramp of Fabrication Reaction
<ol>
	<li>Program thermal cycler as followed:
	<ol>
		<li>Ramp 85 &#176;C to 60 &#176;C at a rate of 5 min/&#176;C.</li>
		<li>Ramp 60 &#176;C to 4 &#176;C at a rate of 75 min/&#176;C.</li>
		<li>Hold at 4 &#176;C indefinitely.</li>
	</ol>
	</li>
	<li>After fabrication has ended store samples at -20 &#176;C.</li>
</ol>
4. Removal of Excess Staples
<ol>
	<li>Add 100 &#181;l of folding reaction mixture to a 0.5 ml centrifugal&#160;filter&#160;with a MWCO&#160;of 100 kDa. Save a 10 &#181;l sample of nanorobots pre-purification for later analysis.</li>
	<li>Centrifuge for 10 min at 9,600 x g.</li>
	<li>Add 400 &#181;l of folding buffer (1x TAE, 10 mM MgCl2).</li>
	<li>Repeat steps 4.2 and 4.3 twice more.</li>
	<li>Centrifuge for 5 min at 9,600 x g.</li>
	<li>Recover the concentrate by placing the filter upside down in a clean microcentrifuge tube and spin for 1 min at 9,600 x g. Final volumes may vary depending on the initial volume of fabrication reaction mixture that was put into the filter. Typically a 25-60 &#181;l final volume of concentrated nanorobot sample is obtained.</li>
	<li>Measure concentration of DNA in the samples via spectrophotometer at 260 nm. Use molecular weight of 5.3 &#181;g/pmol when calculating molar concentrations of nanorobot samples. 
	Note: The molar extinction coefficient for dsDNA, 50 &#181;g/OD260, is sufficient for most applications. 48 &#181;g/OD260 takes into account the poly thymine ssDNA stretches at the Edges staples.</li>
</ol>
5. Agarose Gel Electrophoresis Analysis of Folded Nanorobots
<ol>
	<li>Preparation of 0.5x TBE (45 mM Tris-Borate, 1 mM EDTA), 2% agarose gel supplemented with 10 mM MgCl2 (adapted from Ernesto Castro et al.21):
	<ol>
		<li>Prepare 0.5x TBE buffer by diluting 6.25 ml of 10x TBE stock buffer in 118.75 ml of ddH2O.</li>
		<li>Dissolve 2.5 g of agarose in 125 ml of 0.5x TBE buffer.</li>
		<li>Boil in microwave until the agarose is completely dissolved.</li>
		<li>Add 1.25 ml of 1 M MgCl2 to final concentration of 10 mM.</li>
		<li>Add 7 &#181;l of 10 mg/ml ethidium bromide.</li>
		<li>Wait for solution to slightly cool and fill the gel tray before the agarose gel solidifies. Install desired comb immediately.</li>
		<li>Prepare 1 L 0.5x TBE running buffer by adding 50 ml of 10x TBE stock buffer and 10 ml of 1 M MgCl2 to 940 ml of ddH2O.</li>
		<li>Once gel is solid add running buffer to the electrophoresis device and put device in an ice bath.</li>
	</ol>
	</li>
	<li>Load 1 &#181;g total DNA of the nanorobots pre-purification (step 3.2), and post purification (step 4.7), alongside a scaffold DNA sample and a 1 kb DNA marker, onto the gel. An example is given in Figure 2. Actual volumes of samples depend on the concentrations obtained after purification. Each samples is loaded with loading buffer at a 1:6 final volume ratio.</li>
	<li>Set power source to 80 V and run gel for 3 hr. Run the gel in a bath filled with ice and water. Nanorobots will unfold and appear as a smear if the agarose gel heats up during electrophoresis. During electrophoresis add additional ice to keep device from heating.</li>
	<li>View gel on a UV table (Figure 2).</li>
</ol>
6. Negative Stain of Nanorobot with Uranyl-formate

<ol>
	<li>Preparation of 2% uranyl-formate stock solution (adapted from Castro et al.23):
	<ol>
		<li>Weigh 100 mg of uranyl-formate powder into a 15 ml tube.</li>
		<li>Boil DNase/RNase free ultrapure water for 3 min to de-oxygenate.</li>
		<li>Add 5 ml of deoxygenated hot water (~60 &#176;C) into the 15 ml tube containing the uranyl-formate powder (from previous step). Tightly close lid, wrap in aluminum foil and vortex rigorously for 10 min (fasten tube to a vortex). Solution should appear turbid with a yellow color.</li>
		<li>Filter solution through a 0.2 &#181;m syringe &#64257;lter. Solution should become clear.</li>
		<li>Aliquot 200 &#181;l of the solution into microcentrifuge tubes.</li>
		<li>Centrifuge at max speed for 5 min in a table top centrifuge to pool samples at the bottom of the tube.</li>
	</ol>
	</li>
	<li>Loading of sample to grid and negative staining:
	<ol>
		<li>Defrost a 200 &#181;l aliquot of 2% uranyl-formate solution (prepared in section 6.1). Add 10 &#181;l of 0.5 M NaOH solution and vortex rigorously for 3 min. Centrifuge at max speed for 5 minutes using a table top centrifuge.</li>
		<li>Meanwhile, glow-discharge grid using room air at 0.2 mbar and 25 mA for 30 sec.</li>
		<li>Add 15 &#181;l of 2 nM nanorobot sample after purification (section 4.7) onto topside of grid (held with forceps) and let absorb for 1 min. Use &#64257;lter paper to drain the excess liquid by placing the grid on top of the filter paper. Do not touch the grid surface.</li>
		<li>Add 10 &#181;l of the 2% uranyl-formate (from step 6.2.1) onto the topside of grid (held with forceps).</li>
		<li>Quickly use &#64257;lter paper to drain the excess liquid by placing the grid on top of the filter paper. Do not touch the grid surface.</li>
		<li>Repeat steps 6.2.4 and 6.2.5.</li>
		<li>Add 10 &#181;l of the 2% uranyl-formate (from step 6.2.1) onto the topside of grid (held with forceps). Let staining solution absorb for 30 sec.</li>
		<li>Use &#64257;lter paper to drain the excess liquid by placing the grid on top of the filter paper. Do not touch the grid surface.</li>
		<li>Let the grid dry completely for at least 30 min, face up on a filter paper, before injecting into the TEM.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Watson, J. D., Crick, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetical+implications+of+the+structure+of+deoxyribonucleic+acid.">Genetical implications of the structure of deoxyribonucleic acid.</a> Nature. 171, 964-967 (1953).</li><li>Kosuri, S., Church, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-Scale+de+novo.+DNA+synthesis:+technologies+and+applications.">Large-Scale de novo. DNA synthesis: technologies and applications.</a> Nature Meth. 11 (5), 499-507 (2014).</li><li>Pinheiro, A. V., Han, D., Shih, W. M., Yan, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+and+opportunities+for+structural+DNA+nanotechnology.">Challenges and opportunities for structural DNA nanotechnology.</a> Nature Nanotech. 6 (12), 763-772 (2011).</li><li>Seeman, N. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nucleic+acid+junctions+and+lattices.">Nucleic acid junctions and lattices.</a> J Theor Biol. 99 (2), 237-247 (1982).</li><li>Chen, J. H., Seeman, N. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+from+DNA+of+a+molecule+with+the+connectivity+of+a+cube.">Synthesis from DNA of a molecule with the connectivity of a cube.</a> Nature. 350 (6319), 631-633 (1991).</li><li>Wei, B., Dai, M., Yin, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complex+shapes+self-assembled+from+single-stranded+DNA+tiles.">Complex shapes self-assembled from single-stranded DNA tiles.</a> Nature. 485 (7400), 623-626 (2012).</li><li>He, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hierarchical+self-assembly+of+DNA+into+symmetric+supramolecular+polyhedra.">Hierarchical self-assembly of DNA into symmetric supramolecular polyhedra.</a> Nature. 452 (7184), 198-201 (2008).</li><li>Yin, P., Hariadi, R. F., Sahu, S., Choi, H. M. T., Park, S. H., Labean, T. H., Reif, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programming+DNA+tube+circumferences.">Programming DNA tube circumferences.</a> Science. 321 (5890), 824-826 (2008).</li><li>Rothemund, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Folding+DNA+to+create+nanoscale+shapes+and+patterns.">Folding DNA to create nanoscale shapes and patterns.</a> Nature. 440 (7082), 297-302 (2006).</li><li>Dietz, H., Douglas, S. M., Shih, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Folding+DNA+into+twisted+and+curved+nanoscale+shapes.">Folding DNA into twisted and curved nanoscale shapes.</a> Science. 325 (5941), 725-730 (2009).</li><li>Douglas, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembly+of+DNA+into+nanoscale+three-dimensional+shapes.">Self-assembly of DNA into nanoscale three-dimensional shapes.</a> Nature. 459 (7245), 414-418 (2009).</li><li>Zhang, F., Nangreave, J., Liu, Y., Yan, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+DNA+nanotechnology:+state+of+the+art+and+future+perspective.">Structural DNA nanotechnology: state of the art and future perspective.</a> J Am Chem Soc. 136 (32), 11198-11211 (2014).</li><li>Douglas, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prototyping+of+3D+DNA-origami+shapes+with+caDNAno.">Prototyping of 3D DNA-origami shapes with caDNAno.</a> Nucleic Acids Res. 37 (15), 5001-5006 (2009).</li><li>Ben-Ishay, E., Abu-Horowitz, A., Bachelet, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Designing+a+bio-responsive+robot+from+DNA+origami.">Designing a bio-responsive robot from DNA origami.</a> J Vis Exp. (77), e50268 (2013).</li><li>Douglas, S. M., Bachelet, I., Church, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+logic-gated+nanorobot+for+targeted+transport+of+molecular+payloads.">A logic-gated nanorobot for targeted transport of molecular payloads.</a> Science. 335 (6070), 831-834 (2012).</li><li>Tan, W., Donovan, M. J., Jiang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aptamers+from+cell-based+selection+for+bioanalytical+applications.">Aptamers from cell-based selection for bioanalytical applications.</a> Chem Rev. 113 (4), 2842-2862 (2013).</li><li>Xiang, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nucleic+Acid+Aptamer-Guided+Cancer+Therapeutics+and+Diagnostics:+The+Next+Generation+of+Cancer+Medicine.">Nucleic Acid Aptamer-Guided Cancer Therapeutics and Diagnostics: The Next Generation of Cancer Medicine.</a> Theranostics. 5 (1), 23-42 (2015).</li><li>Zhang, D. Y., Seelig, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+DNA+nanotechnology+using+strand-displacement+reactions.">Dynamic DNA nanotechnology using strand-displacement reactions.</a> Nat Chem. 3 (2), 103-113 (2011).</li><li>Tang, Z., Parekh, P., Turner, P., Moyer, R. W., Tan, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generating+aptamers+for+recognition+of+virus-infected+cells.">Generating aptamers for recognition of virus-infected cells.</a> Clin Chem. 55 (4), 813-822 (2009).</li><li>Sefah, K., Shangguan, D., Xiong, X., O'Donoghue, M. B., Tan, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+DNA+aptamers+using+Cell-SELEX.">Development of DNA aptamers using Cell-SELEX.</a> Nature Prot. 5 (6), 1169-1185 (2010).</li><li>McKeague, M., DeRosa, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+and+Opportunities+for+Small+Molecule+Aptamer+Development.">Challenges and Opportunities for Small Molecule Aptamer Development.</a> J Nucleic Acids. 2012, (2012).</li><li>Amir, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Universal+computing+by+DNA+origami+robots+in+a+living+animal.">Universal computing by DNA origami robots in a living animal.</a> Nature Nanotech. 9 (5), 353-357 (2014).</li><li>Castro, C. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+primer+to+scaffolded+DNA+origami.">A primer to scaffolded DNA origami.</a> Nature Meth. 8 (3), 221-229 (2011).</li><li>Sobczak, J. P., Martin, T. G., Gerling, T., Dietz, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+folding+of+DNA+into+nanoscale+shapes+at+constant+temperature.">Rapid folding of DNA into nanoscale shapes at constant temperature.</a> Science. 338 (6113), 1458-1461 (2012).</li><li>Stahl, E., Martin, T. G., Praetorius, F., Dietz, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+and+scalable+preparation+of+pure+and+dense+DNA+origami+solutions.">Facile and scalable preparation of pure and dense DNA origami solutions.</a> Angew Chem Int Ed Engl. 53 (47), 12735-12740 (2014).</li><li>Lin, C., Perrault, S. D., Kwak, M., Graf, F., Shih, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+of+DNA-origami+nanostructures+by+rate-zonal+centrifugation.">Purification of DNA-origami nanostructures by rate-zonal centrifugation.</a> Nucleic Acids Res. 41 (2), (2012).</li><li>Bai, X. C., Martin, T. G., Scheres, S. H., Dietz, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryo-EM+structure+of+a+3D+DNA-origami+object.">Cryo-EM structure of a 3D DNA-origami object.</a> Proc Natl Acad Sci U S A. 109 (49), 20012-20017 (2012).</li></ol>

The authors have nothing to disclose.

We described the fabrication, purification, and visualization of the DNA nanorobot. Following fabrication of the hexagonal chassis of the device, the function of the nanorobot is programmed with the simple introduction of specific cargo and sensing strands to the robot which readily find their designated position due to hydrogen-bonding complementarity with available single-strand docking sites14,15,22.
The fabrication protocol described uses a slow annealing ramp, which is generally used in our lab to fold a wide range of origami shapes. If production time becomes a key factor other protocols, such as the rapid folding protocol described by Sobczak et al.24 can be used. This protocol is reported to achieve origami folding in high yields, however it requires calibration for each origami shape.
Spin filtration is used to purify the robots from excess staples. When loading the spin column with samples or buffer, care should be taken not to damage the membrane with the pipette tip. The membrane can potentially rupture resulting in dramatically reduced yields. It is advisable to not discard the flow-through until the nanorobots are visualized by AGE.
For certain application a higher purification rate is desired; this can be achieved by repeating the filtration using the original spin column. For even higher purity, a new spin column can be used, however this will have a dramatic negative effect on the yield rates. Other methods for purifying DNA origami structures were tested, such as excision from agarose gel subsequent to electrophoresis and dialysis of excess staples. These methods resulted in either poor yield or poor purification rates compared with the described protocol. Other methods, such as PEG-based purification25 and rate-zonal ultracentrifugation26 were not tested. These methods are reported to achieve high purification rates, however they either result in poor yields (rate-zonal ultracentrifugation) or require precipitation (PEG-based) which can potentially harm the hollow nanorobot shape.
Nanorobots are fabricated with Guide staples which lock the shape in the closed position in order to increase fabrication yeilds15. It is important to remove these staples by adding Guide Removal staples for nanorobots to effectively open in response to the designed stimuli (PDGF in the described protocol). Guide staples are designed with a toehold single strand region for the docking of Guide Removal staples which release the Guide staples through a process of strand displacement18.These staples should be added at a 10:1 molar ratio at the end of the purification of excess staples&#8217; stage (step 4.7) and incubated for 2 hr at room temperature on an end over end shaker.
Visualization by TEM was described, including uranyl-formate 2% negative staining. Compared with uranyl-acetate, uranyl-formate produces finer grain structures which allow for better resolution of DNA origami designs. Care should be taken as uranyl-formate will solidify if aliquots are frozen for long periods of time. It is advisable to use a freshly prepared 2% uranyl-formate solution for staining. Better resolutions are achievable with the use of Cryo-TEM27.
The basic architectural design and fabrication protocol of the DNA nanorobot are ultimately uniform and straightforward. However, a wide range of flexibility is offered in the form of specific cargo mixtures and sensing strands. Moreover, in a single population many subtypes can be introduced and their relative stoichiometry programmed and optimized to fit specific needs. Even greater fine tuning of the specific kinetics at each rate-limiting step is achievable with increasing/reducing the length of double strand hybridization or the introduction of mismatches at specific key positions. This high degree of flexibility with ease of construction allows for the engineering of nanoscale devices capable of performing highly varied complex tasks in a biological relevant milieu.

The uses for nucleic acids nanotechnology are astounding. The tractability of the Watson-Crick base pairing as well as the ease and relative low-cost of large-scale synthesis of custom-made oligos2 has generated an explosion of applications3 and research in the field of DNA nanotechnology. Structural DNA nanotechnology, based on the immobile Seeman junction4,5 as a fundamental building block makes use of DNA as a self-assembling elementary unit for the construction of arbitrary shapes6-8.
The recent development of the scaffolded DNA origami9 technique allows for the construction of complex 2D/3D nano-architectures10-12 with sub-nanometer precision and is an efficient route for building new functional objects with increasing complexity and astonishing diversity. The construction process is based upon a long scaffold single stranded DNA, usually derived from a viral genome, which can be folded through the hybridization of hundreds of short single strand DNA oligos termed staples. The high structural resolution obtained by this technique is the direct result of the natural dimensions of the DNA double helix, while the reproducibility of fabrication is the result of tailoring the short single-strand staple sequences to facilitate the maximum hydrogen-bonding complementarity achievable. With the use of a slow temperature annealing ramp the designed lowest-energy, thermodynamically preferred nanostructure is reached in high yields and fidelity. The easy implementation of junction design rules in a computer code enabled the development of CAD tools, such as caDNAno13, that extremely simplify the task of designing large, complex structures containing hundreds of connected junctions.
Previously we described the design of a DNA nanorobot with the aid of the caDNAno tool14,15. Here we depict the fabrication and visualization, via transmission electron microscopy (TEM), of the nanorobot, a 3D hollow hexagonal nanodevice, with dimensions of 35 x 35 x 50 nm3, designed to undergo a major conformational change in response to a predetermined stimuli and present specific cargo, such as proteins or nucleic acid oligos, sequestered inside. While 12 loading stations are available inside the hollow chassis, the actual number of bound cargo differs with cargo size. Cargo molecules range from small DNA molecules to enzymes, antibodies and 5-10 nm gold nanoparticles. Cargocan either be uniform or heterogeneous, such that each nanorobot contains a mixture of different molecules. Sensing is achieved via two double helical locking gates design to sense proteins, nucleic acids or other chemicals, based either on aptasensor16,17 or DNA strand displacement18 technologies. Recent developments in aptamer selection protocols19-21 enable the design of nanorobots responding to an ever increasing range of molecules and cell types.
Earlier work showed a nanorobot carrying a specific antibody, which upon binding to its antigen can relay either an inhibitory or a prolific signal to the inside of specific cell types in a mixed cell population15. An exciting feature of these nanodevices is their ability to perform even more complex tasks and logic control with the introduction of different nanorobot subtypes in a single population. Recently we demonstrated specific subtypes of nanorobots performing as either positive or negative regulators, controlling an effector population containing an active cargo molecule22.
The protocol presented here describes the fabrication, purification and imaging of a nanorobot gated with aptamer sensor sequences which bind selectively to PDGF to facilitate the opening of the nanorobot15,22. The fabrication process described is similar to the nanorobot fabrication process initially depicted by Douglas et al.15 with changes aimed at reducing overall process duration, while increasing the yield and purification rates.

<table><tbody><tr><td>DNase/RNase free distilled water</td><td>Gibco</td><td>10977</td><td></td></tr><tr><td>M13mp18 ssDNA scaffold</td><td>NEB</td><td>N4040S</td><td></td></tr><tr><td>10x TAE</td><td>Gibco</td><td>15558-042</td><td></td></tr><tr><td>1 M MgCl&lt;sub&gt;2&lt;/sub&gt;</td><td>Ambion</td><td>AM9530G</td><td></td></tr><tr><td>Amicon Ultra 0.5 ml centrifugal filter 100K MWCO</td><td>Amicon</td><td>UFC510024</td><td></td></tr><tr><td>Agarose</td><td>Promega</td><td>V3125</td><td></td></tr><tr><td>TBE buffer</td><td>Promega</td><td>V4251</td><td></td></tr><tr><td>Ethidium bromide 10&amp;nbsp;mg/ml solution</td><td>Sigma Aldrich</td><td>E1510</td><td></td></tr><tr><td>1 kb DNA marker</td><td>NEB</td><td>N3232S</td><td></td></tr><tr><td>Loading Dye</td><td>NEB</td><td>B7021S</td><td></td></tr><tr><td>uranyl formate</td><td>polysciences</td><td>24762</td><td></td></tr><tr><td>carbon-coated TEM grids&amp;nbsp;</td><td>Science services</td><td>EFCF400-Cu-50</td><td></td></tr><tr><td>Thermal Cycler c1000 Touch</td><td>Bio-Rad</td><td></td><td></td></tr><tr><td>Glow Discharge K100X</td><td>Emitech</td><td></td><td></td></tr><tr><td>UV table Gel Doc EZ Imager</td><td>Bio-Rad</td><td></td><td></td></tr><tr><td>NanoDrop 2000c</td><td>Thermo Scientific</td><td></td><td></td></tr><tr><td>TEM FEI-G12</td><td>Tecnai</td><td></td><td></td></tr></tbody></table>

folding and characterization of a bio-responsive robot from dna origami

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both stimuli and cargo can be tailored according to specific needs. Here we describe the DNA nanorobot fabrication protocol, with the use of the DNA origami technique. The procedure initiates by mixing short single-strand DNA staples into a stock mixture which is then added to a long, circular, single-strand DNA scaffold in presence of a folding buffer. A standard thermo cycler is programmed to gradually lower the mixing reaction temperature to facilitate the staples-to-scaffold annealing, which is the guiding force behind the folding of the nanorobot. Once the 60 hr folding reaction is complete, excess staples are discarded using a centrifugal filter, followed by visualization via agarose-gel electrophoresis (AGE). Finally, successful fabrication of the nanorobot is verified by transmission electron microscopy (TEM), with the use of uranyl-formate as negative stain.

Watch this Scientific Journal Video about Folding and Characterization of a Bio-responsive Robot from DNA Origami at JoVE.com

Składanie i charakterystyka bioreagującego robota z Origami DNA | Chemia | Wideo

Folding and Characterization of a Bio-responsive Robot from DNA Origami

DNA origami is a powerful method for fabricating precise nanoscale objects by programming the self-assembly of DNA molecules. Here we describe a protocol for the folding of a bio-responsive robot from DNA origami, its purification and negative staining for transmission electron microscopic imaging (TEM).

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both ...

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14.4K Views.  Bar-Ilan University. DNA origami is a powerful method for fabricating precise nanoscale objects by programming the self-assembly of DNA molecules. Here we describe a protocol for the folding of a bio-responsive robot from DNA origami, its purification and negative staining for transmission electron microscopic imaging (TEM). 

Video: Folding and Characterization of a Bio-responsive Robot from DNA Origami

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this article, we describe detailed protocols on how to fabricate sophisticated 2D shapes through the self-assembly of uniquely addressable single-stranded DNA tiles which act as molecular pixels on a molecular canvas. Each single-stranded tile (SST) is a 42-nucleotide DNA strand composed of four concatenated modular domains which bind to four neighbors during self-assembly. The molecular canvas is a rectangle structure self-assembled from SSTs. A prescribed complex 2D shape is formed by selecting the constituent molecular pixels (SSTs) from a 310-pixel molecular canvas and then subjecting the corresponding strands to one-pot annealing. Due to the modular nature of the SST approach we demonstrate the scalability, versatility and robustness of this method. Compared with alternative methods, the SST method enables a wider selection of information polymers and sequences through the use of de novo designed and synthesized short DNA strands.

DNA tiling is an effective approach to make programmable nanostructures. We describe the protocols to construct complex two-dimensional shapes by the self-assembly of single-stranded DNA tiles.

Current methods in DNA nano-architecture have successfully engineered a variety of 2D and 3D structures using principles of self-assembly. In this ...

Preparation of Mica and Silicon Substrates for DNA Origami Analysis and Experimentation

The designed nature and controlled, one-pot synthesis of DNA origami provides exciting opportunities in many fields, particularly nanoelectronics. Many of these applications require interaction with and adhesion of DNA nanostructures to a substrate. Due to its atomically flat and easily cleaned nature, mica has been the substrate of choice for DNA origami experiments. However, the practical applications of mica are relatively limited compared to those of semiconductor substrates. For this reason, a straightforward, stable, and repeatable process for DNA origami adhesion on derivatized silicon oxide is presented here. To promote the adhesion of DNA nanostructures to silicon oxide surface, a self-assembled monolayer of 3-aminopropyltriethoxysilane (APTES) is deposited from an aqueous solution that is compatible with many photoresists. The substrate must be cleaned of all organic and metal contaminants using Radio Corporation of America (RCA) cleaning processes and the native oxide layer must be etched to ensure a flat, functionalizable surface. Cleanrooms are equipped with facilities for silicon cleaning, however many components of DNA origami buffers and solutions are often not allowed in them due to contamination concerns. This manuscript describes the set-up and protocol for in-lab, small-scale silicon cleaning for researchers who do not have access to a cleanroom or would like to incorporate processes that could cause contamination of a cleanroom CMOS clean bench. Additionally, variables for regulating coverage are discussed and how to recognize and avoid common sample preparation problems is described.

Reproducible cleaning processes for substrates used in DNA origami research are described, including bench-top RCA cleaning and derivatization of silicon oxide. Protocols for surface preparation, DNA origami deposition, drying parameters, and simple experimental set-ups are illustrated.

The designed nature and controlled, one-pot synthesis of DNA origami provides exciting opportunities in many fields, particularly nanoelectronics. Many of ...

Designing a Bio-responsive Robot from DNA Origami

Nucleic acids are astonishingly versatile. In addition to their natural role as storage medium for biological information1, they can be utilized in parallel computing2,3 , recognize and bind molecular or cellular targets4,5 , catalyze chemical reactions6,7 , and generate calculated responses in a biological system8,9. Importantly, nucleic acids can be programmed to self-assemble into 2D and 3D structures10-12, enabling the integration of all these remarkable features in a single robot linking the sensing of biological cues to a preset response in order to exert a desired effect.
Creating shapes from nucleic acids was first proposed by Seeman13, and several variations on this theme have since been realized using various techniques11,12,14,15 . However, the most significant is perhaps the one proposed by Rothemund, termed scaffolded DNA origami16. In this technique, the folding of a long (&gt;7,000 bases) single-stranded DNA 'scaffold' is directed to a desired shape by hundreds of short complementary strands termed 'staples'. Folding is carried out by temperature annealing ramp. This technique was successfully demonstrated in the creation of a diverse array of 2D shapes with remarkable precision and robustness. DNA origami was later extended to 3D as well17,18 .
 
The current paper will focus on the caDNAno 2.0 software19 developed by Douglas and colleagues. caDNAno is a robust, user-friendly CAD tool enabling the design of 2D and 3D DNA origami shapes with versatile features. The design process relies on a systematic and accurate abstraction scheme for DNA structures, making it relatively straightforward and efficient.
In this paper we demonstrate the design of a DNA origami nanorobot that has been recently described20. This robot is 'robotic' in the sense that it links sensing to actuation, in order to perform a task. We explain how various sensing schemes can be integrated into the structure, and how this can be relayed to a desired effect. Finally we use Cando21 to simulate the mechanical properties of the designed shape. The concept we discuss can be adapted to multiple tasks and settings.

DNA origami is a powerful method for fabricating precise nanoscale objects by programming the self-assembly of DNA molecules. Here, we describe how DNA origami can be utilized to design a robotic robot capable of sensing biological cues and responding by shape shifting, subsequently relayed to a desired effect.

Nucleic acids are astonishingly versatile. In addition to their natural role as storage medium for biological information1, they can be utilized in ...

Bioengineering

Production of Dynein and Kinesin Motor Ensembles on DNA Origami Nanostructures for Single Molecule Observation

Cytoskeletal motors are responsible for a wide variety of functions in eukaryotic cells, including mitosis, cargo transport, cellular motility, and others. Many of these functions require motors to operate in ensembles. Despite a wealth of knowledge about the mechanisms of individual cytoskeletal motors, comparatively less is known about the mechanisms and emergent behaviors of motor ensembles, examples of which include changes to ensemble processivity and velocity with changing motor number, location, and configuration. Structural DNA nanotechnology, and the specific technique of DNA origami, enables the molecular construction of well-defined architectures of motor ensembles. The shape of cargo structures as well as the type, number and placement of motors on the structure can all be controlled. Here, we provide detailed protocols for producing these ensembles and observing them using total internal reflection fluorescence microscopy. Although these techniques have been specifically applied for cytoskeletal motors, the methods are generalizable to other proteins that assemble in complexes to accomplish their tasks. Overall, the DNA origami method for creating well-defined ensembles of motor proteins provides a powerful tool for dissecting the mechanisms that lead to emergent motile behavior.

The goal of this protocol is to form ensembles of molecular motors on DNA origami nanostructures and observe the ensemble motility using total internal reflection fluorescence microscopy.

Cytoskeletal motors are responsible for a wide variety of functions in eukaryotic cells, including mitosis, cargo transport, cellular motility, and ...

Biochemistry

Gene-therapy Inspired Polycation Coating for Protection of DNA Origami Nanostructures

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in physiological fluids induce denaturation and degradation of self-assembled DNA nanostructures. In non-viral gene delivery, enzymatic degradation of DNA is overcome by the encapsulation of the negatively charged DNA in a cationic shell. Herein, inspired by gene delivery advancements, a simple, one-step and robust methodology is presented for the stabilization of DNA origami nanostructures by coating them with chitosan and linear polyethyleneimine. The polycation coating efficiently protects DNA origami nanostructures in Mg-depleted and nuclease-rich media. This method also preserves the full addressability of enzyme- and aptamer-based functionalization of DNA nanostructures.

Here, a protocol for the protection of DNA origami nanostructures in Mg-depleted and nuclease-rich media using natural cationic polysaccharide chitosan and synthetic linear polyethyleneimine (LPEI) coatings is presented.

DNA origami nanostructures hold an immense potential to be used for biological and medical applications. However, low-salt conditions and nucleases in ...

Assembly of Gold Nanorods into Chiral Plasmonic Metamolecules Using DNA Origami Templates

The inherent addressability of DNA origami structures makes them ideal templates for the arrangement of metal nanoparticles into complex plasmonic nanostructures. The high spatial precision of a DNA origami-templated assembly allows controlling the coupling between plasmonic resonances of individual particles and enables tailoring optical properties of the constructed nanostructures. Recently, chiral plasmonic systems attracted a lot of attention due to the strong correlation between the spatial configuration of plasmonic assemblies and their optical responses (e.g., circular dichroism [CD]). In this protocol, we describe the whole workflow for the generation of DNA origami-based chiral assemblies of gold nanorods (AuNRs). The protocol includes a detailed description of the design principles and experimental procedures for the fabrication of DNA origami templates, the synthesis of AuNRs, and the assembly of origami-AuNR structures. In addition, the characterization of structures using transmission electron microscopy (TEM) and CD spectroscopy is included. The described protocol is not limited to chiral configurations and can be adapted for the construction of various plasmonic architectures.

We describe the detailed protocol for the DNA origami-based assembly of gold nanorods into chiral plasmonic metamolecules with strong chiroptical responses. The protocol is not limited to chiral configurations and can be easily adapted for the fabrication of various plasmonic architectures.

The inherent addressability of DNA origami structures makes them ideal templates for the arrangement of metal nanoparticles into complex plasmonic ...

DNA Origami-Mediated Substrate Nanopatterning of Inorganic Structures for Sensing Applications

Structural DNA nanotechnology provides a viable route for building from the bottom-up using DNA as construction material. The most common DNA nanofabrication technique is called DNA origami, and it allows high-throughput synthesis of accurate and highly versatile structures with nanometer-level precision. Here, it is shown how the spatial information of DNA origami can be transferred to metallic nanostructures by combining the bottom-up DNA origami with the conventionally used top-down lithography approaches. This allows fabrication of billions of tiny nanostructures in one step onto selected substrates. The method is demonstrated using bowtie DNA origami to create metallic bowtie-shaped antenna structures on silicon nitride or sapphire substrates. The method relies on the selective growth of a silicon oxide layer on top of the origami deposition substrate, thus resulting in a patterning mask for following lithographic steps. These nanostructure-equipped surfaces can be further used as molecular sensors (e.g., surface-enhanced Raman spectroscopy (SERS)) and in various other optical applications at the visible wavelength range owing to the small feature sizes (sub-10 nm). The technique can be extended to other materials through methodological modifications; therefore, the resulting optically active surfaces may find use in development of metamaterials and metasurfaces.

Here, we describe a protocol to create discrete and accurate inorganic nanostructures on substrates using DNA origami shapes as guiding templates. The method is demonstrated by creating plasmonic gold bowtie-shaped antennas on a transparent substrate (sapphire).

Structural DNA nanotechnology provides a viable route for building from the bottom-up using DNA as construction material. The most common DNA ...

Automated Robotic Liquid Handling Assembly of Modular DNA Devices

Recent advances in modular DNA assembly techniques have enabled synthetic biologists to test significantly more of the available &#34;design space&#34; represented by &#34;devices&#34; created as combinations of individual genetic components. However, manual assembly of such large numbers of devices is time-intensive, error-prone, and costly. The increasing sophistication and scale of synthetic biology research necessitates an efficient, reproducible way to accommodate large-scale, complex, and high throughput device construction.
Here, a DNA assembly protocol using the Type-IIS restriction endonuclease based Modular Cloning (MoClo) technique is automated on two liquid-handling robotic platforms. Automated liquid-handling robots require careful, often times tedious optimization of pipetting parameters for liquids of different viscosities (e.g. enzymes, DNA, water, buffers), as well as explicit programming to ensure correct aspiration and dispensing of DNA parts and reagents. This makes manual script writing for complex assemblies just as problematic as manual DNA assembly, and necessitates a software tool that can automate script generation. To this end, we have developed a web-based software tool, http://mocloassembly.com, for generating combinatorial DNA device libraries from basic DNA parts uploaded as Genbank files. We provide access to the tool, and an export file from our liquid handler software which includes optimized liquid classes, labware parameters, and deck layout. All DNA parts used are available through Addgene, and their digital maps can be accessed via the Boston University BDC ICE Registry. Together, these elements provide a foundation for other organizations to automate modular cloning experiments and similar protocols.
The automated DNA assembly workflow presented here enables the repeatable, automated, high-throughput production of DNA devices, and reduces the risk of human error arising from repetitive manual pipetting. Sequencing data show the automated DNA assembly reactions generated from this workflow are ~95% correct and require as little as 4% as much hands-on time, compared to manual reaction preparation.

Here, an automated workflow to perform modular DNA &#34;device&#34; assembly using a modular cloning DNA assembly method on liquid-handling robots is presented. The protocol uses an intuitive software tool for generating liquid handler picklists for combinatorial DNA device library generation, which we demonstrate using two liquid handling platforms.

Recent advances in modular DNA assembly techniques have enabled synthetic biologists to test significantly more of the available &#34;design space&#34; ...

Design and Synthesis of a Reconfigurable DNA Accordion Rack

DNA nanostructure-based mechanical systems or DNA nanomachines, which produce complex nanoscale motion in 2D and 3D in the nanometer to &#229;ngstr&#246;m resolution, show great potential in various fields of nanotechnology such as the molecular reactors, drug delivery, and nanoplasmonic systems. The reconfigurable DNA accordion rack, which can collectively manipulate a 2D or 3D nanoscale network of elements, in multiple stages in response to the DNA inputs, is described. The platform has potential to increase the number of elements that DNA nanomachines can control from a few elements to a network scale with multiple stages of reconfiguration.
In this protocol, we describe the entire experimental process of the reconfigurable DNA accordion rack of 6 by 6 meshes. The protocol includes a design rule and simulation procedure of the structures and a wet-lab experiment for synthesis and reconfiguration. In addition, analysis of the structure using TEM (transmission electron microscopy) and FRET (fluorescence resonance energy transfer) is included in the protocol. The novel design and simulation methods covered in this protocol will assist researchers to use the DNA accordion rack for further applications.

We describe the detailed protocol for design, simulation, wet-lab experiments, and analysis for a reconfigurable DNA accordion rack of 6 by 6 meshes.

DNA nanostructure-based mechanical systems or DNA nanomachines, which produce complex nanoscale motion in 2D and 3D in the nanometer to &#229;ngstr&#246;m ...