Synthesis and DNA Directed Assembly of Asymmetric Patchy Silica Microparticles

We report the synthesis of asymmetric patchy silica microparticles exhibiting two surface areas of different sizes and coated with distinct DNA strands, as well as the coassembly of these particles with polystyrene microspheres into raspberry-like and multimer-like clusters. The multistage synthesis method is based on the fabrication of silica/polystyrene monopods by dispersion polymerization followed by the selective dissolution of the physically entangled polystyrene chains forming the pod. The polystyrene remaining chains at the silica surface, forming a thin polymeric layer, were selectively functionalized with DNA single strands (ssDNA) through the entrapment of an azidated polystyrene-<i>block</i>-poly(ethylene oxide) copolymer followed by a strain promoted alkyne azide cycloaddition (SPAAC) reaction. The later was also used to graft different ssDNA onto the silica side of the patchy particles, which had been prefunctionalized with azide groups via the grafting of an organosilane derivative. Confocal microscopy was exploited to evidence the patchy character of the particles. Finally, these asymmetric patchy particles were used to form colloidal clusters by coassembling them with polystyrene spheres coated with complementary ssDNA, exploiting the selectivity and the specificity of DNA hybridization.