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

In this study, one approach for synthesizing γ-Fe 2 O 3 @SiO 2 nanoparticles using sodium silicate (Na 2 SiO 3 ) as a precursor is investigated. To prepare activation sites for grafting the SiO 2 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-Fe 2 O 3 @SiO 2 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-Fe 2 O 3 @SiO 2 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-Fe 2 O 3 @SiO 2 nanoparticles increase as the purification efficiency improves. In conclusion, γ-Fe 2 O 3 @Na 2 SiO 3 nanoparticles are successfully fabricated by using Na 2 SiO 3 by removing Na ions via an additional acid treatment. This approach is a promising alternative to conventional TEOS-based methods for synthesizing γ-Fe 2 O 3 @SiO 2 nanoparticles with improved dispersibility and purification efficiency.