Synthesis and surface functionalization of Fe₃O₄-SiO₂ core-shell nanoparticles with 3-glycidoxypropyltrimethoxysilane and 1,1′-carbonyldiimidazole for bio-applications

In our research, we have presented the controlled synthesis of Fe₃O₄ nanoparticles (NPs) with a size of about 10 nm coated with SiO₂ shells for bio-applications. On this basis, the controlled synthesis of Fe₃O₄-SiO₂ core-shell nanoparticles and their surface functionalization with 3-glycidoxypropyltrimethoxysilane (GPS) and 1,1′-carbonyldiimidazole (CDI) has been presented with a facile synthetic process. The as-prepared Fe₃O₄-SiO₂-GPS-CDI core-multishell NPs can bind proteins. Therefore, recombinant protein A/G (pA/G) was efficiently coupled onto the surface of NPs via CDI groups, creating a complete coverage. Antibodies (αT IgG) were also conjugated on Fe₃O₄-SiO₂-GPS-CDI-pA/G, i.e. 9 mg αT antibodies per 1 g NPs. After the surface functionalization of the magnetic nanoparticles, their superparamagnetism was reduced by a factor of about threefold in Fe₃O₄-SiO₂, and fivefold in Fe₃O₄-SiO₂-GPS-CDI-pA/G in comparison with that of the naked Fe₃O₄ NPs. The NPs conjugated with αT IgG could bind and remove 1 × 10⁵ cells per 0.25 mg NPs in vitro. Finally, the new models of surface functionalization of magnetic nanoparticles have been proposed for promising bioconjugations in our further research.