Additive Manufacturing of Iron and Iron-Alloy Lattices for Magnetic Nanoparticle Capture

Magnetic nanoparticles are of widespread interest for medical therapies ranging from internal thermal treatments to vector agents for genetic modification to MRI contrast agents.¹ One of the standout applications for magnetic nanoparticles in medical therapies involves the capture of small molecule chemotherapeutics, particularly doxorubicin, via surface functionalization. While rapid capture of doxorubicin by functionalized nanoparticles has been demonstrated <i>in vitro</i>, sequestration of the nanoparticles, especially <i>in vivo</i>, has proven a more complicated task.² Sequestration of nanoparticles in a biological flow such as that found in a blood vessel will require a device that can maximize capture while minimizing flow disruptions and pressure drop across the device. Device designs consisting of solid cylindrical magnets mounted on catheters inevitably obstruct and disrupt the flow as it passes through the blood vessel. Synthesizing microarchitected magnets could allow for favorable flow properties while also allowing for magnetic nanoparticle sequestration; such architected magnetic materials are underexplored in the literature.^3,4 Traditional subtractive methods of manufacturing often obstruct these explorations due to difficulties in attaining desired feature resolutions as well as rapid modification of alloy composition; on the other hand, additive manufacturing allows for flexibility in design and composition. Hydrogel infusion additive manufacturing (HIAM) is capable of synthesizing architected metal lattices. We demonstrate HIAM derived magnetic monolithic microarchitected lattices composed of iron, iron-nickel, and copper-iron-nickel alloys in the shape of a twisted honeycomb prism with a major face diameter of 3-4 mm and a beam thickness of 40-50 um optimized to minimize <i>in vivo</i> flow disruption.^4,5 We perform multiphysics simulations of the process of magnetite nanoparticle capture and compare the resulting capture efficiency to <i>in vitro</i> magnetite nanoparticle capture experiments that demonstrated a preliminary capture efficiency of 10-20%. In addition, we apply vibrating sample magnetometry (VSM) to demonstrate coercivities in the range of 10-100 Oe and remnant magnetizations of 100 Gauss in the synthesized lattices. Powder X-ray diffraction (pXRD) shows a bulk metallic phase with body-centered cubic symmetry for the iron lattice and face-centered cubic symmetry for the iron-nickel and copper-nickel-iron lattices; internal microstructures are characterized by electron backscattered diffraction (EBSD). Finally, we determine the final phase composition via energy dispersive X-ray spectroscopy (EDS).<br/> <br/>[1] Guo, T.; Lin, M.; Huang, J.; Zhou, C.; Tian, W.; Yu, H.; Jiang, X.; Ye, J.; Shi, Y.; Xiao, Y.; Bian, X. <i>J. Nanomater</i>. <b>2018:</b>7805147.<br/>[2] Blumenfeld, C.M.; Schulz, M.D.; Aboian, M.S.; Wilson, M.W.; Moore, T.; Hetts, S.W.; Grubbs, R.H.. <i>Nat. Comm. </i><b>2018</b>;9(1):2870.<br/>[3] Maani, N.; Diorio, T.C.; Hetts, S.W.; Rayz, V.L. <i>Biomech. Model. Mechanobiol</i>. <b>2020</b>;19(5):1865-1877.<br/>[4] Hoo, Wonseok, et al. Submitted.<br/>[5] Saccone, M.; Gallivan, R.A.; Narita, K.; Yee, D.W.; Greer, J.R. <i>Nature</i>. <b>2022</b>;612:685-690.