Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells

Abstract

Many important biomedical applications, such as cell imaging and remote manipulation, can be achieved by labeling cells with superparamagnetic iron oxide nanoparticles (SPIONs). Achieving sufficient cellular uptake of SPIONs is a challenge that has traditionally been met by exposing cells to elevated concentrations of SPIONs or by prolonging exposure times (up to 72 hr). However, these strategies are likely to mediate toxicity. Here, we present the synthesis of the protein-based SPION magnetoferritin as well as a facile surface functionalization protocol that enables rapid cell magnetization using low exposure concentrations. The SPION core of magnetoferritin consists of cobalt-doped iron oxide with an average particle diameter of 8.2 nm mineralized inside the cavity of horse spleen apo-ferritin. Chemical cationization of magnetoferritin produced a novel, highly membrane-active SPION that magnetized human mesenchymal stem cells (hMSCs) using incubation times as short as one minute and iron concentrations as lows as 0.2 mM.

Assembling Living Building Blocks to Engineer Complex Tissues

“…[220,221] Labelling protocols have been developed that can deliver large quantities of SPIONs to cells, with good biocompatibility profile. [222] However, given the microscale dimensions of cells and cellularized biomaterials, relatively large magnetic fields must be used to exert forces capable of moving the living building blocks against competing forces. Early work on magnetic cell assembly was performed by Ito et al, who used external magnetic fields to assemble sheets of magnetized keratinocytes on nonadherent culture surfaces.…”