Discipline: Technology and Engineering
Subcategory: Biomedical Engineering
Jorge L. Castro-Torres - University of Puerto Rico, Mayagüez
Co-Author(s): Eduardo J. Juan, Madeline Torres-Lugo, Janet Méndez, and Fernando Mérida, University of Puerto Rico, Mayagüez, PR
Magnetic fluid hyperthermia (MFH) is a non-invasive cancer treatment in which magnetic nanoparticles are administered to cancerous tissues to raise the temperature of the affected region above a certain threshold
(43-47°C), to induce programmed cell death. To this day, there has been difficulty in the real time observation of cellular behavior during hyperthermia. The systems to generate alternating magnetic fields used for in vitro and in vivo experiments are physically too large to adapt to a confocal microscope to observe in real-time. More importantly, the magnetic field generated by the devices interferes, electromagnetically, with the optical instrument used to visualize the process. Therefore, the focus of this research lies in the design of a miniature device capable of generating a magnetic field intensity strong enough to actuate on the sample, but small enough to allow the visualization of molecular-level events during imaging. Performing live cell imaging during MFH will help in the elucidation of what exactly happens at the cellular level in real-time. For the design, Litz wire was used to wound a 15 mm diameter miniature multilayer “pancake” coil that generated the magnetic field. Litz wire is a special type of stranded wire that minimizes the skin and proximity phenomena, which are normally present in conductors. Due to the resistive losses of the coil, a 32 x 32 x 25 mm cooling chamber was designed and connected to a peristaltic pump to circulate water through it. The magnetic field intensity generated by the inductor was characterized using a custom-made magnetic field probe. To demonstrate the efficacy of the device, three negative controls were utilized: cells, without nanoparticles, exposed to an alternating magnetic field; cells with nanoparticles at 37°C, and cells incubated at 37°C. The cancer cells were stained using Live-Dead Cell Staining Kit® and observed through a confocal microscope to measure cell viability. A maximum magnetic field intensity of 8.7 kA/m at 293 kHz was achieved with our device. Higher field intensities could be achieved, however the temperature raise of the coil is a large constraint since the water flow is not enough to regulate the temperature at stronger fields. Results show that samples were not damaged by exposing them to an alternating magnetic field without nanoparticles nor by leaving them incubating at 37°C, indicating that the magnetic field alone cannot induce hyperthermia on the cells, and the later condition did not kill them. We have successfully designed a device adaptable to a confocal microscope and capable of generating a magnetic field that will not affect the image acquisition in real-time of hyperthermia molecular events. Future research lies in the use of the designed instrument on other cancer cell lines, as they don’t behave equally under the same conditions, and possibly, on animal models to compare results.
Funder Acknowledgement(s): This research was supported by the Nanotechnology Center for Biomedical, Environmental & Sustainability Applications (CREST Phase II - NSF grant 1345156).
Faculty Advisor: Eduardo J. Juan, firstname.lastname@example.org
Role: I did the design and characterization of the coil, which involved calculating the necessary electrical component values for the circuit that was used to generate the magnetic field of specific intensity and frequency. The coil was wound by me and the magnetic field was characterized with a custom-made magnetic field probe that I constructed. Also, I designed the cooling chamber that was adapted to a peristaltic pump to regulate the coil's temperature. In summary, I designed and constructed the device to carry out the experiments.