Artificial muscles are a step closer to reality, with the creation of a dynamic 'goo' made of DNA that responds to stimuli mechanically, much like a real cell.
It can generate forces independently, leading to changes in elasticity or shape, when fed ATP molecules for energy. At just 10 microns in width, the gel is roughly the size of a eukaryotic cell - the type of cell of which humans are made.
It contains within it stiff DNA nanotubes linked together by longer, flexible DNA strands that serve as the substrate for molecular motors.
"DNA gives you a lot more design control," says UC Santa Barbara scientist Deborah Fygenson. "This system is exciting because we can build nano-scale filaments to specifications."
Using a bacterial motor protein called FtsK50C, the team can make the gel react in the same way cytoskeletons react to the motor protein myosin - by contracting and stiffening.
The protein binds to predetermined surfaces on the long linking filaments, and reels them in, shortening them and bringing the stiffer nanotubes closer together. The end result is that the gel quantitatively shows similar active fluctuations and mechanics to cells.
"This new material could provide a means for controllably testing active gel mechanics in a way that will tell us more about how the cytoskeleton works," says Omar Saleh.
Like a cell, which consumes adenosine triphosphate (ATP) for energy, the DNA gel's movement also runs on ATP, allowing for faster, stronger mechanics than other smart gels based on synthetic polymers.
The project has potential applications for a variety of fields, says the team,including smart materials, artificial muscle, cytoskeletal mechanics and research into nonequilibrium physics, as well as DNA nanotechnology.
The team's now looking to refine their technique and enable distinct movements, such as twisting and crawling, or using other motor proteins that would allow the gel to mimic other cell behaviors, such as shape-shifting and dividing.