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Background Thrombotic events continue to be a major cause of morbidity and mortality worldwide. Tissue plasminogen activator (tPA) is used for the treatment of acute ischemic stroke and other thrombotic disorders. Use of tPA is limited by its narrow therapeutic time window, hemorrhagic complications, and insufficient delivery to the location of the thrombus. Magnetic nanoparticles (MNPs) have been proposed for targeting tPA delivery. It would be advantageous to develop an improved in vitro model of clot formation, to screen thrombolytic therapies that could be enhanced by addition of MNPs, and to test magnetic drug targeting at human-sized distances. Methods We utilized commercially available blood and endothelial cells to construct 1/8th inch (and larger) biomimetic vascular channels in acrylic trays. MNP clusters were moved at a distance by a rotating permanent magnet and moved along the channels by surface walking. The effect of different transport media on MNP velocity was studied using video photography. MNPs with and without tPA were analyzed to determine their velocities in the channels, and their fibrinolytic effect in wells and the trays. Results MNP clusters could be moved through fluids including blood, at human-sized distances, down straight or branched channels, using the rotating permanent magnet. The greatest MNP velocity was closest to the magnet: 0.76 ± 0.03 cm/sec. In serum, the average MNP velocity was 0.10 ± 0.02 cm/sec. MNPs were found to enhance tPA delivery, and cause fibrinolysis in both static and dynamic studies. Fibrinolysis was observed to occur in 85% of the dynamic MNP + tPA experiments. Conclusion MNPs hold great promise for use in augmenting delivery of tPA for the treatment of stroke and other thrombotic conditions. This model system facilitates side by side comparisons of MNP-facilitated drug delivery, at a human scale.

Iron oxide nanoparticles (IONs) hold promise for enhancing drug delivery for cancer, stroke, and other diseases. Here, we demonstrate the use of a multiple-lane tissue culture tray and rotating permanent magnet to study magnetically induced rotation and translation (MIRT) of magnetic microbeads (MBs). MBs are nanoparticle aggregates with single-crystalline magnetite cores which can be moved by surface traction. The MIRT tray was produced by additive manufacturing (3-D printing) or subtractive manufacturing (milling) of acrylic. The velocity of MBs in the MIRT tray through phosphate-buffered saline, culture media with fetal bovine serum (FBS), and 100 FBS was measured from 7.5 to 30cm above the rotating magnet. A maximum velocity of greater than 5cms occurred at a distance of 22.5cm. Cultured rabbit aortic endothelial cells, grown in lanes of the sterilized MIRT tray, cause some reduction in MB velocity. We conclude that MBs are easily rotated and moved at physiologic distances by the rotating permanent magnet. Thus, MIRT can potentially be used to direct MBs in clinical drug delivery, and the MIRT tray provides a convenient model system for testing variables which can affect ION movement.

Background: Superparamagnetic iron oxide nanoparticles (SPIONs) have been touted as promising vehicles for enhancing drug delivery for cancer, stroke, and other diseases. Unfortunately, successful clinical use has been hampered by the problem of scale, since the attractive force between iron particle and magnet is inversely proportional to at least the fourth power of the intervening distance. Utilization of magnetically-induced rotary traction (MIRT) offers a way to overcome this obstacle. Here, we present initial data from the use of a new two-part system consisting of: 1) a patented rotating magnet, and 2) magnetic microbeads (MBs), which have been optimized for MIRT. Methods: MBs and the rotating magnet were provided by Pulse Therapeutics (St. Louis, MO). MBs consist of single-crystalline magnetite cores (~70 nm), which form aggregates in response to a magnetic field. Here, the field is generated by a neodymium-boron-iron permanent magnet, which is rapidly rotated causing MBs to counter-rotate (like meshed gears) at physiologic distances, and move by means of surface traction. Movement of MBs through PBS, DMEM with 5% serum, and 100% serum was measured 7.5 to 30 cm from the magnet. Suspensions of the particles were imaged at different concentrations by MRI and CT scan. 3 cancer cell lines (U87, E297, LKB1-KO), and normal vascular endothelial cells, were maintained using standard tissue culture technique. For adhesion studies, cells were grown in 6-well plates to confluence, treated with 10 uL MBs for 30 min., washed with PBS, imaged with standard light microscopy, digitized, then analyzed using Image J. Results: In our experiments, MBs moved readily through PBS, DMEM and serum at distances from 7.5 - 30 cm; with a maximum velocity at 22.5 cm (0.45 +/- 0.04 cm/sec, for serum). While MR imaging produced significant artifact as expected, MBs were clearly seen by CT scan. Adhesion of the MBs to the cancer cell lines was markedly higher than to the endothelial cells (10.9-12.0X) and to fixed cells, used as controls. Conclusions: MBs are easily rotated and moved at physiologic distances, even through 100% serum, by means of surface traction, and can be imaged by CT scan. Adhesion of MBs to cancer cells is significantly greater than to endothelial cells. These features show that the Pulse system is an extremely promising one, for use in magnetic drug targeting in the clinical setting. Citation Format: Herbert Engelhard, Zachary Gaertner, Adam Levin, Ankit Mehta, Sean Morris, Michael Sabo, Frances Creighton. Rotating magnetic beads for enhanced drug delivery: characterization of bead velocity, imaging, and adherence to cellular monolayers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3104. doi:10.1158/1538-7445.AM2017-3104