First autonomous cargo-sorting DNA nanobot developed.

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

Previous studies show that 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 relatively more complex functions were also more difficult to control, and the complexity of tasks limited to what the robot could perform within 3 to 12 steps.  The current study develops a DNA nanobot that explores a two-dimensional testing which picks up multiple cargos of two types that are initially at unordered locations, and delivers each type to a specified destination until all cargo molecules are sorted into two distinct piles.

The current study utilises 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 which recognizes a specific drop-off point and signal to the hand to release its cargo, fluorescent molecules; each of these components is made of just a few nucleotides within a single strand of DNA.  The group state that fluorescent molecules are used to enable them to confirm that the molecules ended up in their intended locations.

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

The team surmise that they have developed single-stranded DNA nanobots which can walk over the surface of a DNA origami sheet and sort molecular cargoes for delivery.  For the future, the researchers state the hope is that the global medical community could use these principles for exciting applications, such as using a DNA nanobot for synthesizing a therapeutic chemical from its constituent parts in an artificial molecular factory, delivering a drug only when a specific signal is given in bloodstreams or cells, or sorting molecular components in trash for recycling.

Source: Caltech


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