Magnetic blood purification based on the use of functionalized and freely diffusing magnetic nanoparticles has demonstrated great potential for the capturing of toxins and pathogens from blood extracorporeally.¹ High surface area available for binding and fast extraction offer significant advantage compared to traditional blood purification techniques, which often suffer from membrane saturation and clotting.² However, the compromise between good dispersibility of the magnetic beads and high bead recovery poses a major challenge.

Here, we report on the synthesis and functionalization of 200 nm superparamagnetic magnetite cluster nanoparticles functionalized with cationic (co)polymer brushes grown using Surface Initiated Atom Transfer Radical Polymerization (ATRP). These nanoparticles form comparatively stable dispersions in physiological fluids (stable for more than 24hrs compared to minutes for the unfunctionalized nanoparticles) and can be fully recovered (>99.9%) in under three minutes. By appropriately selecting co-monomers, the colloidal stability and bead separation times can be further tailored. Introduction of mPEG monomers (1:3) reduces bead recovery times as well as the cytolytic activity of the polycationic brush-functionalized nanoparticles. Following in-depth studies on the colloidal stability as well as bead separability, we then demonstrate the quantitative extraction of free bilirubin from physiological media using cationic polymer brush-functionalized nanoparticles.

Taken together, we present tailorable functionalized magnetic nanoparticle systems that unify colloidal stability with high magnetic recovery rates. The demonstrated bilirubin capturing by the brush-functionalized magnetic nanoparticles has prospective applications in artificial liver support systems.

[1] Inge K. Herrmann, Critical Care, 2015, 19, 239−243.
[2] Stadlbauer Vanessa, Krisper Peter, Beuers Ulrich, et al., ASAIO Journal, 2007, 53, 187-193.