Self-Assembled Functional Nanostructure of Plasmid
DNA with Ionic Liquid [Bmim][PF<sub>6</sub>]: Enhanced Efficiency
in Bacterial Gene Transformation
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Abstract
The
electrostatic interaction between the negatively charged phosphate
groups of plasmid DNA and the cationic part of hydrophobic ionic liquid
1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF<sub>6</sub>]), initiates spontaneous self-assembly to form the functional nanostructures
made up of DNA and ionic liquid (IL). These functional nanostructures
were demonstrated as promising synthetic nonviral vectors for the
efficient bacterial pGFP gene transformation in cells. In particular,
the functional nanostructures that were made up of 1 μL of IL
([Bmim][PF<sub>6</sub>]) and 1 μg of plasmid DNA can increase
the transformation efficiency by 300–400% in microbial systems,
without showing any toxicity for <i>E. coli</i> DH5α
cells. <sup>31</sup>P nuclear magnetic resonance (NMR), Fourier transform
infrared (FTIR) spectroscopy, and X-ray photoelectron (XPS) spectroscopic
analysis revealed that the electrostatic interaction between negatively
charged phosphate oxygen and cationic Bmim<sup>+</sup> tends to initiate
the self-assembly process. Thermogravimetric analysis of the DNA-IL
functional nanostructures showed that these nanostructures consist
of ∼16 wt % ionic liquid, which is considered to provide the
stability to the plasmid DNA that eventually enhanced the transformation
efficiency