Currently, there are multiple approaches to targeted therapies being researched that involve the use of magnetic micro/nanoparticles. Their high biocompatibility as a result of magnetite’s composition and the ability to position the magnetite in biocompatible polymer coatings such as PLA and PLGA makes them a potential resource for cancer treatment and gene delivery. Magnetic targeting utilizes an external magnetic field in combination with MNPs to allow delivery of particles to the desired target area and fixation to a local site while the medication is released and acts locally. This technique allows for decreased dosage of chemical therapies that may otherwise cause deleterious systemic effects. While much work has been completed on functionalizing MNPs and targeting them in vitro, there is minimal work that examines how these MNPs can move through soft tissues to treat disease.

Our work uses an alternating magnetic field, applied perpendicularly to a static magnetic gradient to increase magnetic nanoparticle motion through a simulated soft tissue. In order to increase magnetic susceptibility highly superparamagnetic nanoparticles were synthesized with magnetite concentrations of up to 70% (w/w). We found that magnetic nanoparticle uptake is a force dependent process and that an increase in MNP magnetite concentration not only leads to an increase in magnetic force applied to the cell but also increases MNP uptake. Using this process we were able to load bovine aortic endothelial cells with up to 15% of their cell volume without any deleterious effects to the cytoskeletal or mitochondrial function. As a result of the minimal toxic effects, we tested the ability to manipulate the movement of loaded cells and showed that under the influence of a magnetic gradient from a permanent magnet there was significant increase in MNP loaded cell migration through a collagen coated transwell membrane in comparison to control cells. The loaded cells offer less toxic magnetically targeted vectors with a much higher magnetic susceptibility in comparison to MNPs alone. Further research is needed to determine if the “shaking” effect exhibited in the MNP viscous fluid study would work with MNP loaded endothelial cells.

This thesis analyzes magnetic nanoparticle synthesis with varying magnetite incorporation and how these differences affect magnetic nanoparticle motion with and without an alternating magnetic field. Through this research it has been found that we can load magnetite crystals into polymer nanoparticles up to 70% w/w without affecting the structural integrity of the particle. As a result, the particles synthesized were on average 250 nm in diameter and were significantly more responsive to external magnetic fields in comparison to standard commercially available nanoparticles that are approximately 30-40% w/w. The increase in magnetic responsiveness yields an increase in magnetic nanoparticle velocity through a viscous fluid, under the influence of a magnetic field provided by a neodymium magnet. The velocity in which particles moved increased linearly with respect to the amount of magnetite incorporated into the particle. The addition of the alternating current field that was applied perpendicular to the line of movement allowed the leading edge of the MNP group to move a 10 mm distance more quickly than the static only group. Additionally, the MNPs exposed to the alternating current field, also had an increase in the percentage of particles that made it the entire 10 mm length.

The increase in magnetic responsiveness was also examined when loading MNPs into bovine aortic endothelial cells (BAEC). It was found that an increase in magnetite concentration led to an increase in magnetic nanoparticle uptake into BAEC. This effect was determined to be a function of the magnetic force applied to nanoparticles since MNP uptake was minimal without the influence of a magnetic field.

Lastly, these highly loaded magnetic cells were used in two dimensional and three dimensional migration assays to determine if the MNP loadings had any positive or negative effects on migratory function. In two-dimensional studies, it was determined that highly loaded BAEC were not inhibited from migrating. In fact, 10% and 70% MNP loaded cells experienced migration rates that were significantly higher than that of the control, while 30% MNP loaded cells exhibited a higher migration rate that was not statistically significant. This implied that the functionality of the cytoskeleton for its role of migration was not impaired by the presence of the MNPS. The addition of a magnetic field, resulting from a neodymium magnet was added to 3-D migration in order to determine if MNP loaded BAEC would migrate through a Boyden chamber more quickly than non-loaded BAEC. It was found that the 70% MNP loaded BAEC were able to migrate across the membrane at speeds equal to that of control cells that were encouraged to migrate through the membrane with the assistance of FBS gradients. This study showed successful implementation of MNP loaded cell movement manipulation through a membrane.

The overall study has shown that increased magnetite concentration in polymer MNPs yields higher MNP uptake into endothelial cells. The increased MNP concentration in the cytoskeleton of the endothelial cells allows for an increase in magnetic responsiveness. The increase in MNP concentration shows minimal cellular function impairment. The ability to load these cells and manipulate them through the body with minimal deleterious effects to their functionality makes them excellent candidates as vehicles for gene, drug or cellular deliveries