Scientists from Penn State University have just taken us a major step closer to a Fantastic Voyage future. For the first time ever, researchers have controlled the movements of living cells by inserting tiny synthetic motors directly inside them.
Top gif: A spinning assembly chain of rotating HeLa cells shown at 500X magnification. Credit: Mallouk Lab, Penn State University.
Medical nanotechnology is a kind of holy grail for futurists. Once realized, these molecular machines will revolutionize medical science and the human condition itself. Nanobots will be able to perform medical diagnoses internally, eliminate toxins and disease, produce medicines directly inside our bodies, and supplement existing biophysical processes such as respiration and immunity. More short-term, controllable cells could be used to cruise around the body, communicating with each other and performing various kinds of diagnoses and therapy.
But to get there, we're going to have to figure out how to work at these insanely small scales. Quite obviously, the ability to design, manipulate, and control objects that measure only a few molecules across poses tremendous challenges. It'll likely be several more decades before we're able to achieve many of these capabilities.
Every once in a while, however, we're reminded that we're getting there. Case in point, this remarkable new Penn State study.
A Vivid Demonstration
A team of chemists and engineers accomplished the feat by inserting tiny synthetic motors inside living cells, moving them around with ultrasonic waves and steering them magnetically. Clearly, it's not as elegant as the self-propelled, self-guided nanobots envisaged by futurists and scifi, but it's an important first step. These same basic principles could conceivably be refined and upgraded.
This video, taken ynder 1000X magnification, shows very active gold nanorods internalized inside HeLa cells in an acoustic field. Credit: Mallouk Lab, Penn State University.
As for the nanomotors themselves, they're rocket-shaped particles that move inside the cells, spinning and battering against the cell membrane. Remarkably, the live cells exhibited internal mechanical responses that the scientists had never seen before.
The interaction between gold nanorods and HeLa cells in acoustic fields showing strong attachment (shown at real speed under 500X magnification). Credit: Mallouk Lab, Penn State University.
"This research is a vivid demonstration that it may be possible to use synthetic nanomotors to study cell biology in new ways," noted study co-author Tom Mallouk in a Penn State statement. "We might be able to use nanomotors to treat cancer and other diseases by mechanically manipulating cells from the inside. Nanomotors could perform intracellular surgery and deliver drugs noninvasively to living tissues."
Sound and Magnets
This is the first time nanomotors have been studied in vivo, and not within laboratory apparatus. First generation motors, which first made an appearance 10 years ago, utilized toxic fuels and could not move within biological fluid. But the use of ultrasonic waves as a power source — oscillating sound pressure waves with frequencies greater than the upper limit of human hearing — solved these problems. The researchers used HeLa cells during their experiments, an immortal line of human cervical cancer cells. After ingesting the nanomotors, they moved around the cell tissue, powered by the ultrasonic waves.
Optical microscope image of a HeLa cell containing several gold-ruthenium nanomotors. Arrows indicate the trajectories of the nanomotors, and the solid white line shows propulsion. Near the center of the image, a spindle of several nanomotors is spinning. Inset: Electron micrograph of a gold-ruthenium nanomotor. The scattering of sound waves from the two ends results in propulsion. Photo and caption credit: Mallouk lab, Penn State University.
At low power, the nanomotors exerted very little influence on the cells. But at high power, the nanomotors went into action, moving around and bumping into organelles (structures within a cell that performs specific functions). The pulses controlled whether the tiny motors spun around or incremented forward. The nanomotors could be controlled to completely wipe out the cells' internal mechanisms, or even puncture the membrane.
The researchers were able to control the motors even further by steering them with magnetic forces. The principle is similar to the one developed by Oliver Schmidt and his team at the Institute for Integrative Nanoscience who successfully created remote control sperm.
Interestingly, the researchers discovered that the nanomotors can move autonomously — an ability that could be important for the development of future applications.
"Autonomous motion might help nanomotors selectively destroy the cells that engulf them," Mallouk said. "If you want these motors to seek out and destroy cancer cells, for example, it's better to have them move independently. You don't want a whole mass of them going in one direction."
Read the entire study: Wei Wang, Sixing Li, Lamar Mair, Suzanne Ahmed, Tony Jun Huang, Thomas E. Mallouk. Acoustic Propulsion of Nanorod Motors Inside Living Cells. Angewandte Chemie International Edition, 2014.
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