Fuente: Wired Science
Expuesto el: lunes, 27 de febrero de 2012 22:41
Autor: Dave Mosher
Asunto: Video: First Nanorockets Might Shuttle Drugs, Robo-Surgeons
| In the movie Fantastic Voyage, a crack surgical team is miniaturized inside a ship. Their mission: to destroy a blood clot in the brain of a Soviet-era informant. Given the relatively vast distances covered inside the body, however, movie makers probably should have equipped the team's vessel with rocket motors instead of wimpy propellers. Engineers have now designed nanorockets that would've fit the bill. The bowl-shaped structures self-assemble, are about four times larger than an HIV virus and autonomously zoom toward sources of fuel like bacterial cells scuttle toward food. "It's like a little rocket or jet engine. We used platinum nanoparticles as motors and hydrogen peroxide as fuel in this proof-of-concept, but you could use something else to guide directionality," said chemist and nanotechnologist Daniela Wilson of Radboud University in the Netherlands and co-author of a study published online Feb. 26 in Nature Chemistry. Equipped with a different kind of catalytic core and outer shell, the devices might deliver drugs or — in the distant future — help autonomous, nano-sized robotic surgeons surf the bloodstream. "Nano jet engines seeking out disease and administering drugs only to sick cells may seem like science fiction, but today we are a step closer to making this science fact," Wilson wrote to Wired. While both medical researchers and nanotechnologists like Wilson envision machines so tiny they can operate inside the human body, many fundamental challenges must first be met. The devices need to steer in an environment where the vibration of molecules can send them off-course and play nicely with the human body. Since any built-in fuel supply would soon run out, they also need to find fresh fuel on the fly. Other researchers have engineered microscopic wires, spheres and carbon nanotubes that act like jet engines and can move toward a fuel source. However, Wilson said all of these are too big or impractical. 'It's an exciting step toward the dream of the Fantastic Voyage.' "Great efforts have been made to copy or mimic biological motor systems, to chemically build molecular motors which took years of hard synthetic work," but these could barely be controlled even in laboratory settings, Wilson wrote to Wired. "Why not let the motor build itself?" Wilson, along with colleagues Roeland Nolte and Jan van Hest, used a polymer that automatically scaffolds itself into orbs about 350 nanometers wide. (An HIV virus, by comparison, is about 90 nanometers wide). Such orbs remain pliable until the organic solvent in which they're made is removed. Then they solidify like plastic beads. Similar structures, technically described as vesicles, are already used to deliver enclosed drugs. "Now, we can place a motor in these vesicles and let them go," said Wilson. To create bowl shapes ready to trap a fuel source, the researchers pinned the orbs against a membrane before draining the solvent. Left behind were orbs dimpled into bowls. These could capture platinum particles. When placed in water with a drop of hydrogen peroxide, platinum in the bowls broke down the hydrogen peroxide, emitting a stream of oxygen bubbles. Because the reaction only took place in the presence of hydrogen peroxide, the system automatically selected for vessels that rocketed towards their fuel source. Nanoengineer Joseph Wang of the University of California, San Diego said the engines are the smallest he's ever heard of. "That's the major advance here, and it's an exciting step toward the dream of the Fantastic Voyage," Wang said. But the motors aren't ready for prime-time yet. Although they are smaller than previous engines, they're also slower. Hydrogen peroxide fuel is also toxic to most living tissues. It's not a dooming setback, says Wang, as all nano-sized motors have their hurdles to overcome. "We have to get rid of the hydrogen peroxide fuel and find a way to operate in blood, in typical physiological conditions," Wang said. "This is a very impressive contribution, especially the sub-micrometer size, but it's still a long way to practical biomedical applications."
Video: ICMS Animation Studio/Daniela Wilson, Jan van Hest and Roeland Nolte (TU/e) Image: Top row: An illustration of how the nanorockets were made. Middle and bottom rows: Electron microscope images of nanorockets with various sizes of platinum nanoparticles trapped inside. (Daniela Wilson et al./Nature Chemistry) Citation: "Autonomous movement of platinum-loaded stomatocytes." By Daniela A. Wilson, Roeland J. M. Nolte and Jan C. M. van Hest. Nature Chemistry, published online Feb. 26, 2012. DOI:10.1038/nchem.1281 |
