Programmable DNA Nanoparticle Formation

Equimolar mixtures of the as-prepared SMDH₄ and its complementary partner were added into 0.5 mL Eppendorf tubes. Enough Tris·HCl buffer solution (20 mM Tris·HCl with appropriate concentrations of NaCl; pH = 7.4) was then added to make solutions with the desired total concentration of DNA (2, 5, 10, 15, and 100 μM). The resulting solutions were heated to 90 °C in a Thermomixer R 5355 instrument without shaking and kept there for 10 min to remove all initial DNA interactions. The power to the heating block was then turned off to allow the solution to slowly cool to room temperature over 3 h (for a typical cooling profile of this equipment, please see Figure S16 in the SI of the reported publication).^{18 (link)} The resulting nucleic acid-based polymeric particles were analyzed by DLS and STEM (See SI, Section S3). For other programmable cooling profiles used in the cooling-rate study, a MJ Mini Gradient Thermal Cycler (Bio-Rad Laboratories, Inc., Hercules, CA) was utilized.