“An industrial assembly line includes a factory, workers, and a conveyor system,” said NYU Chemistry Professor Nadrian Seeman, the study’s senior author. “We have emulated each of those features using DNA components.” The assembly line relies on three DNA-based components.
ABSTRACT – Our ability to synthesize nanometre-scale chemical species, such as nanoparticles with desired shapes and compositions, offers the exciting prospect of generating new functional materials and devices by combining them in a controlled fashion into larger structures. Self-assembly can achieve this task efficiently, but may be subject to thermodynamic and kinetic limitations: reactants, intermediates and products may collide with each other throughout the assembly time course to produce non-target species instead of target species. An alternative approach to nanoscale assembly uses information-containing molecules such as DNA to control interactions and thereby minimize unwanted cross-talk between different components. In principle, this method should allow the stepwise and programmed construction of target products by linking individually selected nanoscale components—much as an automobile is built on an assembly line. Here we demonstrate that a nanoscale assembly line can be realized by the judicious combination of three known DNA-based modules: a DNA origami tile that provides a framework and track for the assembly process, cassettes containing three independently controlled two-state DNA machines that serve as programmable cargo-donating devices and are attached in series to the tile, and a DNA walker that can move on the track from device to device and collect cargo. As the walker traverses the pathway prescribed by the origami tile track, it sequentially encounters the three DNA devices, each of which can be independently switched between an ‘ON’ state, allowing its cargo to be transferred to the walker, and an ‘OFF’ state, in which no transfer occurs. We use three different types of gold nanoparticle species as cargo and show that the experimental system does indeed allow the controlled fabrication of the eight different products that can be obtained with three two-state devices.
The DNA origami shape is a composition that uses a few hundred short DNA strands to direct a very long DNA strand to form structures to any desired shape. These shapes are approximately 100 x 100 nanometers in area, and about 2 nm thick (a nanometer is one billionth of a meter). DNA origami serves as the assembly line’s framework and also houses its track.
The three DNA machines, or cassettes, that serve as programmable cargo-donating devices. The cargo species the researchers used are gold nanoparticles, which measure 5 to 10 nanometers in diameter. Changing the cassette’s control sequences allows the researchers to enable or prevent the donation of the cargoes to the growing construct.