Science 351, 841–845 (2016)

The design of a nanoparticle is dictated by its application and, for biomedical uses, the different stimuli inside the body that the nanoparticle encounters. Although current nanoparticle designs are relatively sophisticated they still cannot meet such demanding requirements. Inspired by the responsive nature of proteins, Warren Chan and colleagues at the University of Toronto and the University of Tokyo have now developed a dynamic nanostructure that can change its fluorescent and cell uptake properties by transforming its shape.

The researchers used DNA to assemble large, medium and small nanoparticles into 'core–satellite' structures that can change shape in response to specific DNA sequences. Each nanoparticle contains one DNA strand for assembly and another for shape change. Initially, small and medium particles are attached to the large particle through linker DNA strands. To change shape, an attaching DNA strand is added to anchor the small nanoparticle to the medium one. Addition of a detaching DNA strand dislocates the linker strands and transforms the entire assembly, with the medium nanoparticle becoming the new core surrounded by small satellite particles. Each step of the shape change takes 10 min and is reversible with an efficiency of 89%. When the large particle is functionalized with folic acid — a targeting ligand for the folate receptor on many cancer cells — the shape change can mask and unmask the folic acid. The unmasked assembly showed higher uptake by cancer cells, suggesting that the presentation of targeting ligands (and consequently cell uptake properties) can be controlled by changing the shape of the nanoassemblies.