Tuning the Effective Interactions between Spherical Double-Stranded DNA Brushes

We present an experimental investigation of the mechanisms that can be used to control blunt-end induced effective attractions between densely packed spherical double-stranded DNA (dsDNA) brushes. Using microscopy and particle tracking, we determine the effects of varying the parameters controlling the brush and dsDNA fragment conformation, in particular functionality, salinity, and dsDNA fragment length. The analysis of the structure and dynamics of increasingly concentrated dispersions reveals that a decrease in functionality or an increase in salt content leads to a progressive reduction of the effective attractions. For the functionality, this can be associated with the reduction of the surface density of blunt-end, while for the salinity, this can be associated with DNA backfolding. We, therefore, reveal means of controlling blunt-end-induced interactions that could be used to guide colloidal self-assembly based on DNA base stacking, a parallel platform to base pairing.