DNA nanotechnology in the undergraduate laboratory: Toehold-less strand displacement in switchback DNA

Dynamic DNA nanostructures that reconfigure into different shapes are used in several applications in biosensing, drug delivery and data storage. One of the ways to produce such structural transformations is by a process called strand displacement. This laboratory experiment demonstrates a strand displacement reaction in a two-stranded DNA nanostructure called switchback DNA by the addition of a third strand. In this process, the difference in the affinity between the component DNA strands is used to convert switchback DNA into conventional duplex DNA. Students are introduced to the concept through gel electrophoresis and quantitative analysis of DNA nanostructure reconfiguration. The experiment presented here follows a series of DNA nanotechnology-based exercises in an undergraduate setting and is tailored for adaptation in a chemistry, biology, or biochemistry laboratory with minimal costs.