Fabrication of Core–Shell γ-Fe2O3@SiO2 Nanoparticles for Plasmid DNA Purification

In this study, one approach for synthesizing γ-Fe2O3@SiO2 nanoparticles using sodium silicate (Na2SiO3) as a precursor is investigated. To prepare activation sites for grafting the SiO2 network onto the magnetic particles, a presurface treatment involving an acid or base is utilized. The effects of pH on the surface charge and thickness of the coating layer on the γ-Fe2O3@SiO2 nanoparticles are analyzed. The optimal pH for achieving the best surface charge properties and dispersibility is identified and used for subsequent experiments. The resulting γ-Fe2O3@SiO2 nanoparticles exhibit improved dispersibility and are evaluated for plasmid deoxyribonucleic acid (DNA) purification. The result shows that their performance is comparable to that of nanoparticles prepared using conventional tetraethyl orthosilicate (TEOS). Residual Na ions on the particle surface can reduce the plasmid DNA purification efficiency. Therefore, additional acid treatment is performed to remove residual Na ions. The correlation between the surface charge and interparticle forces is examined by considering the presence or absence of residual Na ions. The zeta potential and particle size distribution of the γ-Fe2O3@SiO2 nanoparticles increase as the purification efficiency improves. In conclusion, γ-Fe2O3@Na2SiO3 nanoparticles are successfully fabricated by using Na2SiO3 by removing Na ions via an additional acid treatment. This approach is a promising alternative to conventional TEOS-based methods for synthesizing γ-Fe2O3@SiO2 nanoparticles with improved dispersibility and purification efficiency.