Plasmid DNA was purified using core-shell γ-Fe2O3@SiO2
nanoparticles synthesized by a common sol-gel method utilizing tetraethylorthosilicate (TEOS) as a silica precursor. The dispersibility and TEOS binding affinity of γ-Fe2O3 nanoparticles were enhanced by acid/base treatment due to the formation of additional surface hydroxyl groups prior to SiO2 deposition. Since SiO2 was coated under basic conditions in the presence of ammonia as a catalyst, base-treated γ-Fe2O3 nanoparticles were more suited for this modification due to exhibiting a larger zeta potential and a lower saturation magnetization loss. The performance of the synthesized γ-Fe2O3@SiO2
nanoparticles with a 15-nm-thick SiO2 layer in the purification of plasmid DNA was compared to that of commercial Fe3O4-based magnetic beads. The used DNA samples exhibited similar purities, and all samples had similar theoretical plasmid DNA binding capacities. However, γ-Fe2O3@SiO2
nanoparticles exhibited a faster separation speed and a larger saturation magnetization of 100 emu/g compared to that of commercial Fe3O4-based magnetic beads (75 emu/g).