Nano-sized propellers could revolutionize medicine

Nano-sized devices and robots that could be deployed inside the body to deliver medicine or clear out cholesterol would make medical treatment faster and more effective. The challenge is to deliver the devices to the right spot in the body. That would require a nano-sized propulsion system — and now that’s in the realm of the possible.

Researchers from the Technion and from two German institutions have come up with a nano-sized propeller that could, when attached to a device, make its way through the viscous materials that make up the human body, like blood and fat.

The propeller is made up of a silica and nickel filament that is only 70 nanometers in diameter, and 400 nanometers long — smaller not only than any previously made propeller, but smaller than any swimming organism currently known to science. The propeller, developed by Technion researchers along with scientists from the Max Planck Institute for Intelligent Systems, and the Institute for Physical Chemistry at the University of Stuttgart, Germany, worked well in water. Then the team enhanced it to work in thicker environments. The team published a paper about their efforts in ACS Nano, a publication dedicated to nano-tech developments.

The project is in the research stage, and it will probably take years before it’s available for general use.

To improve their device, the team used hyaluronan, a material that occurs throughout the human body, including the synovial fluids in joints and the vitreous humor in eyeballs. Hyaluronan gel contains a mesh of long proteins called polymers, with openings small enough to accommodate nano-sized objects. The scientists were able to control the motion of the propellers using a relatively weak rotating magnetic field to control movement. The nano-propellers were able to go where no propeller had gone before — able even to permeate the interiors of cells.

Scientists had not expected to be able to control the propeller, said the Technion’s Alex Leshanksy, a co-author of the study. Because the propellers are so small – nearly molecule sized. They expected them to be easily diffused into the bloodstream, as molecules would be. But because the nano-propellers are the same size as the mesh in the gel, they “actually display significantly enhanced propulsion velocities, exceeding the highest speeds measured in glycerin as compared with larger micro-propellers, which show very low or negligible propulsion,” said Leshanksy.

“If you compare the diameter of the nano-propellers with a human blood cell, then the (propellers) are 100 times smaller,” said Peer Fischer, a member of the research team and head of the Micro, Nano, and Molecular Systems Lab at the Max Planck Institute for Intelligent Systems. “They are so small, in fact, that their motion can be affected by the motion of nearby molecules, known as Brownian motion. One can now think about targeted applications, for instance in the eye, where they may be moved to a precise location on the retina,” Fischer added. “Scientists could also attach ‘active molecules’ to the tips of the propellers, or use the propellers to deliver tiny doses of radiation. The applications seem wide, varied, and exciting.”