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<h1> Team Nanoscooter Braunschweig </h1>

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<p align="justify" style="line-height:2em"><font size="3pt"> <font size="+2pt"><u>Pt-Particle Functionalization</u></font> <br><br>

The gear of the Nanoscooter is realized by the catalytic mechanism of decomposition of hydrogen peroxide. As catalyst platinum nanoparticles are used, which are attached to the back of the Nanoscooter. To attach the nanoparticles to the Nanoscooter DNA hybridization is used: The Nanoscooter features 12 DNA capturing strands in the back and the nanoparticles are functionalized with the complementary sequence. This can be accomplished by using DNA strands with a thiol-group at the 5’-end – the thiol reacts with the nanoparticle surface and a covalent bond is created.<br> <br> The decomposition of hydrogen peroxide is based on a catalytic mechanism: Platinum decreases the activation energy of the decomposition of hydrogen peroxide, so that it easily can be cleaved into oxygen and water. The emerging oxygen gas induces a repulsion so that the Nanoscooter can deliberately drive over the surface.<br><br><br>

<font size="+1pt">Functionalization of platinum nanoparticles<br> <font size="3pt">A glass and a magnetic stir bar were washed with ethanol and MilliQ-water and dried afterwards. Then 1.8 mL MilliQ-water were mixed with 200 µL of 5 nm platinum nanoparticle solution (1 mg/mL). After that 100 µL thiol functionalized oligonucleotides (100 µM, 15T) were added and stirred overnight at room temperature. <br><br> The next day, 20 µL Tween20 (10 %) were added and stirred for 15 min. 20 µL Phosphate buffer (4:5 mixture of P8709 and P8584) were pipetted to the mixture and stirred for 15 min. After this step the sodium chloride concentration was increased in several steps up to a final concentration of 700 mM. The mixture was incubated overnight.<br><br> The liquid was filtered with an Amicon Ultra 30K Filter (4 krcf, 20°C, 3 min). The residue was removed and the filter refilled with 100 mM NaCl in PBS-buffer. The suspension was centrifuged for 15 min at 5 krcf and 20°C. This procedure was repeated two more times. Then the filter was flipped. To get the nanoparticles out of the filter it was centrifuged for 5 min at 5 krcf and 20°C.<sup>[1]</sup> <br><br>

The diameter of the platinum nanoparticles is analyzed by dynamic light scattering (DLS) with Malvern Zetasizer. The diameter of the non functionalized nanoparticles amounts 5.00 nm ± 0.70 nm, while the diameter of the functionalized nanoparticles is 13.61 nm ± 1.09 nm (Figure 1). </font> </font></p><br><br> <div align="center"><img src="" width="75%" height="75%" ><br></div><br><i><font size="3 "><div align="center">Figure 1: Diameters of the functionalized and non functionalized platinum nanoparticles.</font></i></div><br> <p align="justify" style="line-height:1.5em">We therefore conclude that our Pt-nanoparticles are successfully functionalized with DNA and now ready for attachment to the DNA origami Nanoscooter!<br><br>

For a list of used buffers see <a href="">here</a>. <hr style="background-color:#be1e3c;"> <table> <tr><td><font size="2pt"><p align="justify"> [1]<br><br></font></td> <td><font size="2pt">R. Polsky, R. Gill, L. Kaganovsky, I. Willner: <i>Nucleic Acid-Functionalized Pt Nanoparticles: Catalytic Labels for the Amplified Electrochemical Detection of Biomolecules</i>, Anal. Chem.,<b> 2006</b>, <i>78</i>, 2268-2271.</font></td></tr></table>

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