Inspired by nature, artificial microtubules can work against a current to transport tiny cargoes

Like a microscopic bucket brigade, an artificial microtubule can rapidly transport tiny particles along magnetic stepping stones, delivering them to a precise location even when operating against a strong current. The technology, developed by a team from the University of Pennsylvania and ETH Zürich, may one day facilitate the delivery of targeted therapies through the bloodstream to treat blocked vessels or cancerous tumors.

Researchers have explored the potential of microrobots to "swim" in the bloodstream as a way of directing drugs to the exact location where they are needed. The drawback of this approach is that freely swimming microrobots struggle to make headway against the complex fluid flows that exist inside the human body.

"As a result, you often see dispersion of the particles that you would like to deliver," says Arnold Mathijssen, a corresponding author on the work and an assistant professor in Penn's Department of Physics & Astronomy. "Really what you would like to achieve is to have the largest concentration of the therapeutic at one site and not have it disperse anywhere else, as that could result in toxicity."

Catheters and microneedles have until now been the techniques of choice to complete these directed interventions. Yet catheters can only be miniaturized so far before they lack the pumping force necessary to transport microscopic cargo. Similarly, even microneedles are still too large to reach the narrowest blood vessels.

To overcome these obstacles, Mathijssen and colleagues looked to biology for inspiration. "When you look in nature, inside cells there is a beautiful solution," Mathijssen says. "Microtubules, which are part of the cytoskeleton, use molecular motors to transport vesicles to different locations in the cell.

Image source: Arnold Mathijssen/Nature Machine Intelligence.