DNA-Powered Nanotrain Builds Its Own Tracks
Thanks to GE's Deltavision OMX Blaze microscope (crowned the "OMG" microscope by one researcher), scientists are now able to spy diseases in action down to the molecular and cellular level. It can zero in on bacterial cell division; watch cancer cells respond to chemotherapy; and observe viruses such as HIV move from cell to cell. We'll take a look at fascinating images from the OMG in the coming slides. Shown here: an epithelial cell in metaphase, with microtubules marked in red and DNA in blue.
In this human cervical cancer cell, DNA is stained blue and the microtubules green. The small red dot is the pericentrin centrosome protein.
It's fireworks in both directions for this mitotic spindle in a cell, with its tubulin stained green.
Human keratinocyte cells are stained blue for DNA and green for keratin-14.
This pebbled stripe of red is actually GE's "OMG" microscope revealing the sound-detecting sensory cells of the inner ear.
Green-stained microtubules highlight this cervical cancer cell. (DNA is shown in blue.)
This HIV tissue segment shows CD4+ cells stained in red, stoma in green and nuclei in blue.
The images produced by the OMG are "showstoppers," according to NIH director Dr. Francis Collins. These cells are no exception.
Molecule-sized shuttles that build their own micro-tracks then use those pathways to deliver compounds from one location to another, says the University of Oxford research team that created the nano-vehicles.
Such networks could carry medicine to precise locations of disease or they could be used to transport molecular materials to places in the body where new structures need to be built.
The team used kinesins, which are “motor” proteins that can carry other molecules and assemble them, like a train car carrying a crane and supply of rails to build tracks. Physics graduate student Adam Wollman and his team put two kinesins together, called assemblers. The proteins built “tracks” out of artificial, non-living DNA. The tracks were arranged in a pattern like a wagon wheel with spokes.
The scientists then used kinesin molecules as “shuttles,” which worked like boxcars to deliver a fluorescent green dye. Adding adenosine triphosphate (ATP), which cells use to transport energy, made the kinesins carrying the dye spread out along the hub and spokes.
After the kinesin “boxcars” had settled in place, the scientists added ATP again. This time the kinesins carried the dye to the central hub of the wheel.
To reverse the process, the team added a signaling molecule, which told the kinesins to take the dye out of the central hub and release it, allowing it to disperse. Another set of signal molecules told the kinesin assemblers to break up their track network when their job was done. The whole process is seen in this video.
The inspiration came from fish. Some fish species have cells called melanophores. Melanophores have the same “track” system, a hub-and-spoke configuration connecting skin cells. When the fish wants to change its color — say in response to a threat — motor proteins carry pigment to the central point, the hub, which might be in a single skin cell. Since the pigment is now gone from the rest of the cells surrounding that hub, the skin is transparent and the fish looks lighter.
This experiment involved dye, but the same thing could be applied to a lot of other molecules. It’s also a good proof-of-concept for using DNA as a building block and assembler for molecule-sized machines.