DNA-Coated Microspheres and Their Colloidal Superstructures

Reversible and specific interaction between single-stranded DNA on colloidal particles have opened up a new path way of building up colloidal superstructures. DNA-coated microspheres can be bound with other particles with complementary DNA brushes below the melting temperature and can be unbound above the melting temperature. However, due to their random Brownian motion, the particles form random (or glassy) structures in most cases or small crystals when cooling is extremely slow. Therefore, toward programmed colloidal superstructures of DNA-coated microspheres, they should reconfigure their kinetically trapped random structure to equilibrium crystalline structures. While nanoparticles can be rearranged into a crystalline structure by a simple conformational change of relatively long DNA brush, microspheres with short DNA brushes cannot be rearranged only by a conformational change of brush. Instead, sub-diffusion of bound DNA-coated microspheres is necessary which can be possible only with uniform DNA coating with high areal density on microspheres. In this article, we have reviewed methods for the synthesis of high-density DNA-coated microspheres and their assembly into crystalline structures. We also discuss future research direction of DNA-coated microspheres.