Influence of Magnesium Ions on the Preparation and Storage of DNA Tetrahedrons in Micromolar Ranges

The DNA tetrahedron (Td), as one of the novel DNA-based nanoscale biomaterials, has been extensively studied because of its excellent biocompatibility and increased possibilities for decorating precisely. Although the use of Td in laboratories is well established, knowledge surrounding the factors influencing its preparation and storage is lacking. In this research, we investigated the role of the magnesium ions, which greatly affect the structure and stability of DNA. We assembled 1, 2, 5, 10 and 20 μM Td in buffers containing different Mg(2+) concentrations, demonstrating that 2 and 5 mM Mg(2+) is optimal in these conditions, and that yields decrease dramatically once the DNA concentration reaches 20 μM or the Mg(2+) concentration is lower than 0.5 mM. We also verified that the Td structure is retained better through freeze-thawing than lyophilization. Furthermore, a lower initial Mg(2+) (≤2 mM) benefited the maintenance of Td structure in the process of lyophilization. Hence, our research sheds light on the influence of Mg(2+) in the process of preparing and storing Td, and also provides some enlightenment on improving yields of other DNA nanostructures.