The ability to attach different functional moieties to a molecular building block(1,2) could lead to applications in nanoelectronics(3), nanophotonics(4), intelligent sensing(5) and drug delivery(6,7). The building unit needs to be both multivalent and anisotropic, and although many anisotropic building blocks have been created(1,8-12), these have not been universally applicable. Recently, DNA has been used to generate various nanostructures(13-17) or hybrid systems(18-25), and as a generic building block for various applications(26-30). Here, we report the creation of anisotropic, branched and crosslinkable building blocks (ABC monomers) from which multifunctional nanoarchitectures have been assembled. In particular, we demonstrate a target-driven polymerization process in which polymers are generated only in the presence of a specific DNA molecule, leading to highly sensitive pathogen detection. Using this monomer system, we have also designed a biocompatible nanovector that delivers both drugs and tracers simultaneously. Our approach provides a general yet versatile route towards the creation of a range of multifunctional nanoarchitectures.