(649e) Optimized High-Energy Dissipating Nanoparticles for Magnetic Hyperthermia in Ovarian Cancer Cells

Authors: 
Merida, F., University of Puerto Rico, Mayagüez Campus
Chiu-Lam, A., University of Florida
Bohorquez, A. C., University of Florida
Maldonado-Camargo, L., University of Florida
Mendez, J., University of Puerto Rico, Mayagüez Campus
Torres-Lugo, M., University of Puerto Rico, Mayagüez Campus
Rinaldi, C., University of Florida

Magnetic Fluid Hyperthermia (MFH) uses heat generated by magnetic nanoparticles exposed to alternating magnetic fields to cause a temperature increase in tumors to the hyperthermia range, inducing programmed cancer cell death. The development of nanoparticle synthesis strategies that maximize the rate of energy dissipation are required to reduce the amount of nanoparticles needed at the target tissue though enhanced particle uptake into cancer cells is also a requirement. To date, the aqueous co-precipitation synthesis method has only been reported to yield sufficiently high specific absorption rates (SAR) after laborious size selective fractionation. This work reports high-energy dissipating nanoparticles obtained through optimized synthesis and peptization methods. The internalization patterns of these particles in three ovarian cancer cell lines and preliminary magnetic hyperthermia results are also presented in this work. Nanoparticles were synthesized using the aqueous co-precipitation of Fe2+ and Fe3+ inorganic salts at 80-90°C and 0.08-1.0M (Fe2+ + Fe3+). Peptization was carried out using tetramethylammonium hydroxide under low and high-energy sonication. Characterization of particles included transmission electron microscopy, dynamic light scattering, UV-Vis spectroscopy, equilibrium and dynamic magnetic measurements, and evaluation of energy dissipation rates in alternating magnetic fields. Oleic acid was adsorbed onto the surface of particles at 80°C and then ligand exchanged with PEG-Silane for 72 hours at room temperature. PEG-coated particles were washed and air-dried, and the iron oxide percentage was determined by thermo-gravimetric analysis. Nanoparticle internalization was carried out using A2780 IP-1, HeyA8 and SKOV3 SC2 ovarian cancer cell adhered to the bottom of 6-well plates, at iron oxide concentration of 0.6 mg/mL and exposure times up to 3 hours. Cells were manually counted and the iron uptake was quantified by UV-Vis spectroscopy. Cells were exposed to magnetic hyperthermia (Hf = 4.90 x 103 A·m-1·s-1) for 30 minutes at 43°C and 45°C, incubated for 48 hours at 37°C, and assayed with CellTiter Blue® for cell viability. Confocal microscopy of Alexa® 488 labeled particles was employed to investigate internalization patterns. SAR values up to 1,048 W/gFe (liquid) and 719 W/gFe (solid) were obtained under optimal conditions. High energy ultrasound applied during peptization improved particle dispersion, increasing the energy dissipation rates. Iron uptake up to 3.4 ρg/cell was quantified after 3-hours exposure, and this internalization was cell dependent. Cell viabilities of 15-40% were obtained after MFH at 43°C, whereas only 3% viability was observed at 45°C. Nanoparticle internalization in SKOV3 cells was successfully visualized through confocal microscopy, showing accumulation of particles inside the cells. We concluded that synthesis optimization yielded high energy dissipation rates, using a simple, cost-effective and scalable method. Nanoparticles were internalized in ovarian cancer cells and they were observed in the cell’s cytoplasm as small clusters most likely inside lysosomes. Cell viability reduction occurred after MFH treatment for 30 minutes. Experiments are underway to increase the in vitro nanoparticle internalization using various methods.