A novel aqueous biphasic system formed by deep eutectic solvent and ionic liquid for DNA partitioning.

In this work, aqueous biphasic systems (ABSs) composed of ionic liquids (ILs) and deep eutectic solvents (DESs) were developed and utilized to efficiently extract DNA for the first time. Four kinds of ILs/DESs were mainly constituted by betaine/carboxylic acid and betaine/carbohydrates respectively. While another DES ([TBAB][PPG400]) was formed by polypropylene glycol 400 (PPG 400) and tetrabutylammonium bromide (TBAB). The phase-formation ability of the studied ABSs was evaluated by using [TBAB][PPG400]/(ILs/DESs) and [TBAB][PPG400]/inorganic salts. The results revealed that the phase forming ability of ABSs involved with the size of anion alky chain of ILs, the viscosity, the density and the hydrophilicity of DESs, ionic radius and ionic valence of inorganic salts. Then the system comprising [TBAB][PPG400]/IL was selected to ascertain the optimum extraction conditions for the extraction of DNA by the influence factor experiments. Meanwhile the maximum extraction efficiency could be attained 99.60%. Mixed sample experiments were implemented to separate DNA/cytochrome C (Cyt-c) and DNA/bovine hemoglobin (BHb), where the DNA mainly partitioned to IL-rich bottom phase. It turned out that the relationship between the isoelectric point of analytes and the pH of the system played an important role in the separation process. The result also showed that the studied system can be applied to selectively separate mixtures of nucleic acids and proteins in a single-step. Moreover, the developed system was successfully applied to the extraction of DNA from bovine whole blood with satisfactory result. Finally, the extraction mechanisms associated with the separation process were explored by FT-IR spectra, circular dichroism spectra (CD), dynamic light scattering (DLS), transmission electron microscopy (TEM). Overall, the novel systems have been proven to be a remarkable performance in the separation of DNA, which is expected to be widely used and provide further possibilities in separation fields.