Robots are an important type of molecular machine capable of automatically carrying out complex nanomechanical tasks. DNA molecules are excellent materials for building molecular robots as their geometric, thermodynamic, and kinetic properties are well understood and highly programmable.  However, the development of DNA nanobots has been limited to simple functions.  Now, a study from researchers at Caltech develops a DNA robot capable of performing a nanomechanical task substantially more extensively than previous models.  The team states they have successfully developed a simple algorithm and three modular building blocks to enable a DNA nanobot to perform autonomous cargo sorting.  The study is published in the journal Science.

Previous studies show most DNA nanobots were designed to perform a single function, namely walking in a controlled direction. A few demonstrations included a second function combined with walking, such as picking up nanoparticles or choosing a path at a junction.  However, these more complex functions were also more difficult to control, with the complexity of tasks limited to what the robot could perform within 3 to 12 steps.  The current study develops a DNA nanobot with the capacity to retrieve two different cargos from unordered locations and sort them into two piles.

The current study utilizes three basic building blocks to assemble a DNA robot, a ‘leg’ with two ‘feet’ for walking, an ‘arm’ and ‘hand’ for picking up cargo, and a segment to recognize a specific drop-off point and signal to the hand to release its cargo of fluorescent molecules.  Each of these components is made up of just a few nucleotides within a single strand of DNA.  The group states fluorescent molecules are used to enable them to confirm the molecules ended up in their intended locations.

Results show the nanobot could explore a molecular surface, pick up two different fluorescent molecules, and then distribute them to two distinct regions on the surface.  Data findings show the nanobot successfully sorted 3 pink and three yellow molecules scattered on the surface into their correct places in 24 hours.  They state adding more nanobots to the surface shortened the time it took to complete the task.

The team surmises they have developed single-stranded DNA nanobots capable of walking over the surface of a DNA origami sheet and sorting molecular cargoes for delivery.  For the future, the researchers state their technology could be used for synthesizing therapeutic chemicals, targeted drug delivery, or sorting molecular components for recycling.

Source: Caltech

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