Biomod/2014/results

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Results: Building the world´s smallest car


Although there is still a long way to a nanoscale factory with self-assembling nanorobots, our Nanoscooter project reached most of its goals! Eventually, it could be a first step for the realization of an autonomous nanoscale factory.

Coming back to the stopovers assigned, we conclude that our project was successful in almost every aspect:

- DNA origami design and verification:
The success of the design was verified using gel electrophoresis and atomic force microscopy (AFM): After optimization of the folding conditions, we received a very high yield of correctly folded Nanoscooters as can be seen on the AFM images.

Figure 1: 3D Nanosooter Image reconstructed from AFM measurements.

- Pt-particle functionalization and attachment to the Nanoscooter:

The functionalization of the platinum nanoparticles succeeded and was proofed via dynamic light scattering (DLS) where we received an increase in diameter upon incubation with the thiol-modified oligonucleotides. The tethering of the nanoparticles to the DNA origami was verified via gel electrophoresis: The functionalized DNA origami ran slower than the pure Pt-nanoparticles in our agarose gel, a clear difference was visible.





Figure 2: Gel electrophoresis and DLS-results.

- Fluorescence labeling:

The idea of labeling DNA origamis with StreptAvidin coated fluorescent beads was successful: Using rectangular DNA origamis labeled with red fluorophores, we could show efficient labeling with the fluorescent beads in a colocalization experiment using multicolor fluorescence widefield microscopy. Although the labeling principle was shown to be successful, similar colocalization experiments with the Nanoscooter showed that the attachment of fluorescent beads to the Nanoscooter failed. A possible reason might be a steric hinderance:The fluorescent beads have a diameter of about 40 nm; they might be too big to fit into the curved upper part of the origami to bind to the biotin. However, this can easily be solved using longer linkers to the biotin anchors.





Figure 3: Colocalization on rectangular DNA origamis.

- Random movement:

On AFM images random diffusion of rectangular DNA origamis on mica surfaces was successfully visualized! The imaging of ‘floating’ DNA origamis via fluorescence microscopy was nearly impossible on our inverse widefield microscope due to optical abberations caused by the mica surface. Further experiments require a water-dipping objective and an upright microscope to avoid disturbance through the mica surface.





Figure 4: Floating rectangular DNA origamis imaged by AFM (left) and MICA-induced abberations in fluorescence microscopy imaging (right).

- Active movement:

Strong gas development was observed after adding H2O2 to the Nanoscooter functionalized with Pt-nanoparticles, so we are confident that the engine of the Nanoscooter is working as designed. We further showed that incubation with H2O2 does not have an effect on the integrity of DNA origami. For imaging the movement via fluorescence microscopy, again a water-dipping objective and an upright microscope are necessary as gas development make AFM experiments impossible.



Figure 5: Left: Rectangular origamis without H2O2 (a) and after 4 h incubation in H2O2 (b); Right: Emerging oxygen gas of the H2O2 decomposition.


Summing up, we successfully designed a self-assembling Nanoscooter which can move over mica surfaces powered by Pt-nanoparticles catalyzing the decomposition of hydrogen peroxide. The next challenge will be to use more elaborate imaging conditions to visualize this movement in detail.

However, even so far we expect that this Nanoscooter drives us one step further to the realization of nanoscale autonomous factories!

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