Researchers from Emory University have developed a nano-robot based on rolling DNA that moves faster than any previously designed DNA motors. The technique, based on DNA-coated spheres that bind to an RNA layer, could find applications in disease diagnostics. The findings were published in Nature Nanotechnology,
There are many examples of natural nano-robots in the cells, with different roles like muscle contraction or cargo transport. Many of these nano-motors consume ATP for reversible binding of two-legged proteins to microtubule tracks. Inspired by nature, researchers have tried to design artificial nano-robots, made of DNA and powered by RNA, that walk with two legs. However, they are really unstable due to Brownian motion, which affects nanoscale objects. Some designs incorporated two or four extra legs to increase stability, but at the price of dramatically slowing down the robot.
Ribonuclease H powers the nano-robot movement
Khalid Salaita thought of a different approach: instead of a walking robot, he designed a DNA robot that rolls. His team used 1 um glass beads with hundreds of DNA strands attached to its surface. The balls with legs were placed on an surface coated with RNA strands complementary to the DNA legs, and ribonuclease H, an enzyme that degrades the RNA in DNA/RNA duplexes, was added. The DNA strands are attracted to the RNA and, as soon as they hybridize, the RNA is destroyed by the enzyme, freeing the ball to keep advancing by means of new DNA-RNA contacts. The rolling motion and the fast RNA catalysis provide stability and speed at levels unseen before in a synthetic nano-motor. The rolling robot is only 10 times slower than myosin.
The new robot can detect a DNA mutation by measuring the speed with which it moves: if the strand is mutated, the hybrid won’t be properly formed and the enzyme reaction will be noticeably slower. Other prospective uses include heavy metal detection in water, drug delivery or cell repair.
This is a low-cost method that can be applied by low-budget labs or in field work.
Source: Emory University