Isolation/separation of plasmid DNA using hemoglobin modified magnetic nanocomposites as solid-phase adsorbent

Hemoglobin (Hb) modified magnetic nanocomposites are prepared by immobilization of Hb onto the surface of amino-functionalized Fe3O4@SiO2 magnetic nanoparticles via covalent bonding with glutaraldehyde as cross-linker. The obtained nanocomposites are characterized with FT-IR, SEM, XRD and surface charge analysis. A direct solid-phase extraction procedure for the isolation/separation of plasmid DNA using this nanocomposite as a novel adsorbent is thus developed. Some important experimental parameters governing the sorption efficiency, i.e., the pH of sample solution and the ionic strength, are investigated. The Hb modified magnetic nanocomposites provide a sorption capacity of 27.86 mg g−1 for DNA. By using 2.0 mg of the nanocomposites as sorption medium and a suitable acidity of pH 6.1, a sorption efficiency of 93% is achieved for 25 μg mL−1 of DNA in 1.0 mL of sample solution. Afterwards, the absorbed DNA could be readily recovered by using 1.0 mL of Tris–HCl buffer (pH 8.9, 0.01 mol L−1), giving rise to a recovery of ca. 68.3%. The present solid-phased extraction protocol is applied for the isolation of plasmid DNA from Escherichia coli culture, resulting in comparable yield and purity of plasmid DNA with respect to those obtained by using commercial kits.