(716h) Exploiting Tunable Association/Dissociation Transitions for Rational Control of DNA-Mediated Particle Assembly

Development of strategies for DNA-mediated synthetic nanomaterials production has aimed to exploit highly specific and reversible properties of DNA hybridization as a novel method to program complexity of and control over self-assembling materials spanning nanometer to micrometer scales.  DNA hybridization is thermally reversible, and thus the base-pair design of hybridizing “sticky ends” attached to particles, and the control of other influential factors are critical for tuning the melting transitions that affect assembly within these systems.   Here, we report the effect of PEO99-PPO65-PEO99 block copolymer (Pluronics F127), a common additive employed for nanoparticle dispersion, on the melting transition of micron-sized colloids mediated with complementary single-stranded DNA “sticky ends” as a function of the F127 concentration and temperature. Through quantification of the melting transition by cyclic heating and cooling between fully associated and fully dissociated state, we find that the melting temperature increases as a function of F127 concentration.  Furthermore, the melting profile of DNA-coated colloids shows significant increases in the width of the association/dissociation transition.  Diffusion measurements have been carried out as a function of F127 concentration, and provide insight into the kinetics of the association/dissociation transitions observed.  These results suggest that the melting transition for DNA-mediated assembly is sensitive to commonly used additives in laboratory buffers, such as Pluronics F127, and that these common solution components may be exploited as a facile and independent handle for tuning the melting temperature, the breadth of the transition, and, ultimately, the assembly and crystallization within these systems.