Preservation of DNA in nuclease-rich samples using magnetic ionic liquids

Abstract

Nucleic acids are important diagnostic molecules for a variety of applications, but are exceedingly sensitive to enzymatic degradation by nucleases. Very recently, hydrophobic magnetic ionic liquids (MILs) have shown considerable promise in the area of DNA extraction. Here, we show that MILs can also serve as DNA preservation media in nuclease-rich environments. DNA samples treated with deoxyribonuclease I (DNase I) were found to retain their molecular weight for up to 72 h at room temperature within the benzyltrioctylammonium bromotrichloroferrate(III) ([N_888Bn⁺][FeCl₃Br⁻]) and trihexyl(tetradecyl)phosphonium tetrachloroferrate(III) ([P₆₆₆₁₄⁺][FeCl₄⁻]) MILs, whereas DNA in aqueous samples suffered complete enzymatic degradation under similar conditions. Using a single drop extraction (SDE) technique, DNase I was found to partition between aqueous solution and MIL with a smaller amount of the enzyme extracted by the [N_888Bn⁺][FeCl₃Br⁻] MIL relative to the [P₆₆₆₁₄⁺][FeCl₄⁻] MIL. Plasmid DNA (pDNA) exhibited structural stability for up to 1 week in the [N_888Bn⁺][FeCl₃Br⁻] and [P₆₆₆₁₄⁺][FeCl₄⁻] MILs, even when treated with 20 U of DNase I. pDNA stored within the MIL solvent under these conditions was successfully amplified by polymerase chain reaction (PCR), whereas pDNA in aqueous solutions of DNase I yielded no detectable amplicon. Furthermore, pDNA stored within the trihexyl(tetradecyl)phosphonium tetrachloromanganate(II) ([P₆₆₆₁₄⁺]₂[MnCl₄²⁻]) MIL was capable of conveying antibiotic resistance to competent E. coli following 24 h incubation with DNase I at room temperature, demonstrating that the biological activity of pDNA was preserved.