BIOCOMPATIBLE IRON OXIDE NANOPARTICLES OBTAINED VIA THE NON-AQUEOUS SYNTHESIS IN HYDROPHILIC SOLVENTS FOR HIGH GRADIENT MAGNETIC PROTEIN PURIFICATIONS

Magnetic nanoparticles have a broad field of applications including biomedicine, magnetocaloric refrigeration, magnetic sealing and magnetic storage. For all applications it is of crucial importance that the characteristics such as the physical properties, morphology, composition and surface structure of the particles are well defined and controllable.
The non-aqueous sol-gel method is a bottom-up synthesis which allows synthesizing particles with the desired properties. Particles with tunable size and high crystallinity can be obtained employing mild conditions and using environmental friendly high-boiling solvents. Whereas the use of hydrophobic solvents such as benzyl alcohol is well established, we show that by using hydrophilic solvents like triethylen glycol (TEG), water-compatible nanoparticles with high stability against agglomeration can be directly achieved.
We characterized the physical and chemical properties of the particles such as their size and morphology but also magnetic properties throughout the synthesis process in order to gain knowledge about the parameters which have to be tuned to obtain particles with the optimum properties for applications such as high gradient magnetic protein purification.

Figure 1 Iron oxide nanoparticles after 24h of synthesis in TEG.

We found that depending on the solvent used for the synthesis, the surface of the nanoparticles strongly differs, and a further functionalization can be applied to adjust and optimize the surface chemistry. The physical properties can be accustomed by terminating the synthesis after certain periods, thus being able to tune e.g. the anisotropy energy and blocking temperature of the particles.
In a second step the acquired particles were functionalized with a priorly coupled ligand to achieve a specific binding between a desired protein and the particles, as well as their stabilization in aqueous and biologic media. This system showed great potential as a highly specific magnetic purification system while time and labor could be minimized compared to a traditional chromatographic approach.
Publications:
Functionalization of magnetic nanoparticles with high-binding capacity for affinity separation of therapeutic proteins, I.-C. Masthoff, F. David, C. Wittmann, G. Garnweitner, Journal of Nanoparticle Research, 2013, 16, 1-10.
Formation of magnetic nanoparticles studied during the initial synthesis stage, M. Kraken, I.-C. Masthoff, A. Borchers, F.J. Litterst, G. Garnweitner, Hyperfine Interact 2013, 1-7.