It is widely known that the ability to attach different functional moieties to a molecular building block can lead to applications in fields such as nanoelectronics, nanophotonics, intelligent sensing and drug delivery. The building unit needs to be both multivalent and anisotropic, and although many anisotropic building blocks have been created these have not been universally successful in achieving their end application.

A group of scientists from the US [Lee J. B. et al., doi: 10.1038/NNANO.2009.93] have successfully created anisotropic, branched and crosslinkable building blocks (ABC monomers) from which multifunctional nanoarchitectures have been assembled. They demonstrated successfully that a target-driven polymerization process in which polymers are generated only in the presence of a specific DNA molecule can lead to highly sensitive pathogen detection. Using this particular monomer system, they also designed a biocompatible nanovector that delivers both drugs and tracers simultaneously. Their approach provides a general and versatile route towards the creation of a range of multifunctional nanoarchitectures.

Lee and his group have developed a modular (‘plug-and-play’) approach to constructing a multifunctional nanoarchitecture from an ABC monomer building block. To create the ABC monomer, branched Y-shaped DNA (Y-DNA) conjugated with different moieties acted as the modular donor and X-shaped DNA (X-DNA) was used as the core acceptor molecule. The monomers were characterized using gel electrophoresis, which revealed that the fluorescence colours of the ABC monomers corresponded to the various combinations of donor Y-DNAs. To synthesize multifunctional nanoarchitectures from an ABC monomer we designed each ABC monomer to have two quantum dots with three different colour configurations being able to link several hundred quantum dots together and thus effectively amplify signals from a single targetbinding event, each target-driven polymer also contains a unique fluorescence code with a specific ratio of green and red; this feature makes it possible to detect multiple targets simultaneously.

In addition to detecting pathogen DNA, the ABC polymeric spheres can also serve as multi-drug delivery vectors due to their built-in multivalency and anisotropicity.

The built-in DNA scaffolds also provide an interface for nucleic acid-based drugs. The built-in ‘plug-and-play’ feature coupled with its ‘mix-and-match’ flexibility makes the ABC monomers a versatile platform.

Any other functional groups, both organic and inorganic, that can be conjugated with DNA (or RNA) can be incorporated into the final nanoarchitectures. Lee et al anticipate that these ABC monomers will lead to many possibilities for creating more novel nanostructures and nanomaterials with multiple functionalities.