'Transformer' style molecular machines made of DNA hold promise in world of biomedicine

Ohio State University engineers have used a combination of natural and synthetic DNA to build flexible shape-changing machines like 'Transformers' that can perform tasks repeatedly.

In a process known as "DNA origami" where long strands of DNA are coaxed to fold into different shapes, and secured in parts using "staples" made from shorter DNA strands, the team built stable structures whose motion could be controlled.

The nano machines can perform basic tasks like carrying a small amount of medicine inside a container-like DNA structure and opening the container to release it.

"I'm pretty excited by this idea," project leader Carlos Castro, assistant professor of mechanical and aerospace engineering said. "I do think we can ultimately build something like a Transformer system, though maybe not quite like in the movies. I think of it more as a nano-machine that can detect signals such as the binding of a biomolecule, process information based on those signals, and then respond accordingly—maybe by generating a force or changing shape."

While bio-nanotechnology has been trying to reproduce the molecular functions synthetically, the present work aims at using the biological system for macroscopic machine design.

In their approach for designing and controlling the machines' motion, the team had to use a combination of rigid and flexible parts and then 'tune' the components to repeat movements.

They made flexible parts from single-stranded DNA and stiffer parts from double-stranded DNA.

The next step involved "tuning" the DNA structures so that the machines' movements are reversible and repeatable.

Stiff DNA "planks" with flexible staples along one edge helped create a simple hinge, while a system that moved a piston inside a cylinder was made using five planks, three hinges and two tubes of different diameters—all from pieces of double and single-stranded DNA.

Tests under an electron microscope confirmed that all parts were working and that researchers could control the motion with the addition of chemical cues to which the DNA strands reacted differently by sticking or unsticking together.

The next step is to scale up production of the machines for further development.

The paper was published in the Proceedings of the National Academy of Sciences.