Colloidal dispersions of monodisperse magnetite nanoparticles modified with poly(ethylene glycol)

Monodisperse magnetite nanoparticles modified with poly(ethylene glycol) (PEG) were synthesized using a silane functionalized PEG obtained by reacting 3-aminopropyl triethoxysilane with carboxylic acid-methoxy PEG (mPEG–COOH) using amide reactions. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential measurements show the particles are monodisperse (σgv∼0.2σgv∼0.2) and stable in water for pH of 3–9 and ionic strengths, up to 0.3 M NaCl. Thermogravimetric analysis coupled with TEM and DLS indicates formation of a dense graft layer on the particle surface. An analysis of the interparticle interaction energy indicates that the particles are stabilized by strong steric repulsions between PEG chains on their surface.

Graphical abstractMonodisperse magnetic nanoparticles were coated with mPEG–silane molecules. The colloidal stability of these nanoparticles was studied from DLVO theory. Steric repulsion between PEG–silane chains of approaching particles was responsible for nanoparticle stabilization, making these nanoparticles suitable for biological applications.Figure optionsDownload full-size imageDownload as PowerPoint slide