Synthesis, Surface Modification, and Biolabeling with Aptamer of Fe3O4@SiO2 Magnetic Nanoparticles

Fe3O4 nanoparticles are of great interest for researchers because of their unique physical and chemical properties, especially excellent magnetic responsivity with an external magnetic field, and they have enormous potential applications in various fields, such as fast magnetic separation, magnetic resonance imaging (MRI), biolabeling, clinical detection and diagnosis, and targeted drug delivery. But, bare Fe3O4 MNPs are subjected to oxidation and agglomeration when dispersed in solvents. Therefore, suitable surface-modification is extremely important for Fe3O4 MNPs to improve their stability, biocompatibility, and functionality. In this study, Fe3O4 MNPs were synthesized via a soft template method, and then were coated with silica by our modified Stober approach, which improved the dispersity of Fe3O4@SiO2 nanoparticles. Subsequently, the obtained Fe3O4@SiO2 nanoparticles were modified with amino group and carboxyl group. With the help of zeta potential analysis and surface elemental analysis, it was shown that all kinds of modification of Fe3O4 MNPs, including silica-coating, amino-modification and carboxyl-modification, were successful. Furthermore, the amino-modified aptamer was successfully immobilized on the surface of carboxyl activated Fe3O4@SiO2 nanoparticles.