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Updated: Oct 21, 2025
Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells
Published on: December 13, 2016
Magnetoferritin enhances T2 contrast in magnetic resonance imaging of macrophages
Ambrish Kumar1, Vikas Nandwana2, Soo-Ryoon Ryoo2
1School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Dr., Block N1.3, Singapore 637457, Singapore; NTU-Northwestern Institute for Nanomedicine, Nanyang Technological University, Singapore 637553.
Imaging of immune cells has wide implications in understanding disease progression and staging. While optical imaging is limited in penetration depth due to light properties, magnetic resonance (MR) imaging provides a more powerful tool for the imaging of deep tissues where immune cells reside. Due to poor MR signal to noise ratio, tracking of such cells typically requires contrast agents. This report presents an in-depth physical characterization and application of archaeal magnetoferritin for MR imaging of macrophages - an important component of the innate immune system that is the first line of defense and first responder in acute inflammation. Magnetoferritin is synthesized by loading iron in apoferritin in anaerobic condition at 65 °C. The loading method results in one order of magnitude enhancement of r1 and r2 relaxivities compared to standard ferritin synthesized by aerobic loading of iron at room temperature. Detailed characterizations of the magnetoferritin revealed a crystalline core structure that is distinct from previously reported ones indicating magnetite form. The magnetite core is more stable in the presence of reducing agents and has higher peroxidase-like activities compared to the core in standard loading. Co-incubation of macrophage cells with magnetoferritin in-vitro shows significantly higher enhancement in T2-MRI contrast of the immune cells compared to standard ferritin.
Imaging of immune cells has wide implications in understanding disease progression and staging. While optical imaging is limited in penetration depth due to light properties, magnetic resonance (MR) imaging provides a more powerful tool for the imaging of deep tissues where immune cells reside. Due to poor MR signal to noise ratio, tracking of such cells typically requires contrast agents. This report presents an in-depth physical characterization and application of archaeal magnetoferritin for MR imaging of macrophages - an important component of the innate immune system that is the first line of defense and first responder in acute inflammation. Magnetoferritin is synthesized by loading iron in apoferritin in anaerobic condition at 65 °C. The loading method results in one order of magnitude enhancement of r1 and r2 relaxivities compared to standard ferritin synthesized by aerobic loading of iron at room temperature. Detailed characterizations of the magnetoferritin revealed a crystalline core structure that is distinct from previously reported ones indicating magnetite form. The magnetite core is more stable in the presence of reducing agents and has higher peroxidase-like activities compared to the core in standard loading. Co-incubation of macrophage cells with magnetoferritin in-vitro shows significantly higher enhancement in T2-MRI contrast of the immune cells compared to standard ferritin.
