Corrosion study of iron‐cobalt alloys for MRI‐based propulsion embedded in untethered microdevices operating in the vascular network

Abstract

Our group have shown in an experiment performed in the carotid artery of a living swine that magnetic gradients generated by a clinical magnetic resonance imaging (MRI) system could propel and navigate untethered medical microdevices and micronanorobots in the human vasculature. The main problem with these devices is that the metal necessary for magnetic propulsion may corrode and induce cytotoxic effects. The challenge, then, is to find an alloy with low corrosion yet providing an adequate magnetization level for propulsion in often stringent physiological conditions. Because of their high magnetization, we studied the corrosion behavior of two iron-cobalt alloys, Permendur (49% Fe, 49% Co, 2% V) and Vacoflux 17 (81% Fe, 17% Co, 2% Cr), in physiological solution by potentiodynamic polarization assay, surface analysis, and corrosion electrolyte analysis. Both alloys exhibited low corrosion parameters such as a corrosion potential (E corr ) of 20.57 V/SCE and E corr of 20.42 V/SCE for Vacoflux 17. The surface of Permendur samples was homogenously degraded. Vacoflux 17 surface was impaired by cracks and crevices. Both alloys had a stoichiometric dissolution in the electrolyte, and they released enough cobalt to induce cytotoxic effects. This study concluded that Fe-Co alloys could be used preferably in medical microdevices if they were coated so as not to come in contact with physiological solutions. '

Iron Oxide Nanoparticles for Magnetically-Guided and Magnetically-Responsive Drug Delivery

“…Furthermore, progress is being made in improving the delivery of magnetic forces via magnetic needles, meshes and bandages, as well as through new methods for creating “stealth” delivery vehicles that use magnetic particles incorporated in macrophages or stem cells. One of these improvements is the approach referred to as magnetic resonance navigation (MRN), which has been proposed to steer and track in real time endovascular magnetic carriers in deep tissues to target areas of interest [ 35 , 36 , 37 , 38 ] and to restrain the systemic carrier distribution. MRN is achieved with a clinical MRI scanner upgraded with an insert of steering coils [ 38 , 39 ].…”

“…The scanner allows tracking the carrier during MRN along a pre-planned trajectory. The magnetic field (1.5 T or higher) of the system enables M s of ferromagnetic materials throughout the body [ 35 , 37 ]. Hence, the problem of a weaker magnetic field in deep tissues observed with an external magnet can be overcome.…”

Advances in Applied Biotechnology

“…A possible solution to this problem may be obtained by a new approach referred to as magnetic resonance navigation (MRN). This has been proposed to steer and track in real time endovascular magnetic carriers in deep tissues to target areas of interest (Pouponneau et al, 2010), and restrain the systemic carrier distribution. MRN is achieved with a clinical magnetic resonance imaging (MRI) scanner upgraded with an insert of steering coils.…”

Lighting up Micro-/Nanorobots with Fluorescence

“…One of the greatest challenges for MNRs in biomedical applications is their real-time imaging and tracking, in particular, those in vivo applications. To overcome this challenge, a variety of imaging technologies have been explored, including fluorescence imaging (FI), , magnetic resonance imaging (MRI), ultrasonic imaging (USI), computed tomography (CT), and photoacoustic (PA) imaging . Among them, FI of MNRs are usually achieved by functionalizing them with fluorescent substances, which not only endows MNRs with high spatiotemporal trackability but also may gift them with environmental sensitivity and chemo-/photon-induced therapy in complex biological environments .…”