Monodisperse magnetic nanoparticles prepared from block copolymer template (Vol. 48, No. 5-6)

SEM images of superparamagnetic nanoparticles made from self-assembled block copolymer template (a) on Si substrate, (b) after their release in solution

Magnetic nanoparticles are playing an increasing role in biomedical applications, both for diagnosis (e.g. contrast agent in MRI (Magnetic resonance imaging) or for MPI (magnetic particles imaging)) and for therapy thanks to their ability to exert forces and torques on biological species allowing for instance cancer cells destruction or oriented growth of biological tissue.

In order to fabricate magnetic nanoparticles with high monodispersity, required in particular in biomedical imaging, we have developed a new preparation method based on the use of self-assembled block copolymer template.

Such techniques have already been explored for the preparation of patterned media for ultra-high density magnetic recording. However, our requirements substantially differ from those for storage media. A sacrificial layer has to be introduced between the substrate and the diblock copolymer to allow the release of the nanoparticles in solution. For that purpose, an optimized germanium oxide layer was used. The obtained superparamagnetic particles do not agglomerate in solution. They can be made of biocompatible material (magnetite) and exhibit very narrow size dispersion (≈7%). They can be good contrast agents for medical imaging.

M. Morcrette, G. Ortiz, S. Tallegas, H. Joisten, R. Tiron, T. Baron, Y. Hou, S. Lequien, A. Bsiesy and B. Dieny, Fabrication of monodisperse magnetic nanoparticles released in solution using a block copolymer template, J. Phys. D: Appl. Phys. 50, 295001 (2017)