Effect of Nonionic Surfactant on Association/Dissociation Transition of DNA-Functionalized Colloids

We report the effect of nonionic surfactants (Pluronics F127 and F88) on the melting transition of micron-sized colloids confined in two dimensions, mediated by complementary single-stranded DNA as a function of the surfactant concentration. Micron-sized silica particles were functionalized with single-stranded DNA using cyanuric chloride chemistry. The existence of covalently linked DNA on particles was confirmed by fluorescence spectroscopy. The nonionic surfactant not only plays a significant role in stabilization of particles, with minimization of nonspecific binding, but also impacts the melting temperature, which increases as a function of the nonionic surfactant concentration. These results suggest that the melting transition for DNA-mediated assembly is sensitive to commonly used additives in laboratory buffers, and that these common solution components may be exploited as a facile and independent handle for tuning the melting temperature and, thus, the assembly and possibly crystallization within these systems.