A functionalization strategy for the dispersion of permanently magnetic barium-hexaferrite nanoplatelets in complex biological media

Abstract

In this paper we present a major advance in the colloidal stabilization of nanoparticles in complex biological media that is one of the ongoing challenges for the usage of nanoparticles in biomedicine. A very common solution is to coat the nanoparticles surfaces with dextran via an electrostatic or coordinative attachment. The dextran molecules can be subsequently crosslinked to form a biocompatible coating. However, these procedures are not suitable for nanoparticles with an extreme tendency for agglomeration that often occurs during the coating steps. The novel functionalisation strategy ensures the colloidal stability of the system in all the steps of the coating process. In addition to this, the robustness of the dextran coating, obtained by the covalent attachment of the dextran molecules via the 3-glycidyloxypropyl-trimethoxysilane linker to the surfaces of the silica-coated nanoparticles, ensures the colloidal stability of nanoparticles in complex biological media. As a case study we selected permanently magnetic barium hexaferrite nanoplatelets that are extremely prone to agglomeration due to the magnetic dipole-dipole interaction and their plate-like shape. At the same time barium hexaferrite nanoplatelets are receiving an increasing attention for its use in biomedical applications. The multistep formation of the coating was followed with transmission electron microscopy, nuclear magnetic resonance and electro-kinetic measurements, while the colloidal stability in different complex biological buffer media was inspected visually and with dynamic laser scattering.