RESUMEN
Magnetomotive (MM) ultrasound (US) imaging is the identification of tissue in which magnetic nanoparticle tracers are present by detecting a magnetically induced motion. Although the nanoparticles have a magnetization that depends nonlinearly on the external magnetic field, this has often been neglected, and the presence of resulting higher harmonics in the detected motion has not been reported yet. Here, the magnetization of nanoparticles in gelatin was modeled according to the Langevin theory of superparamagnetism. This nonlinear relationship has a fundamental effect on the resulting force and motion. However, the magnetic field must contain regions with a strong magnetic gradient and a low absolute magnetic field to allow the significant generation of higher harmonics in the force. To validate the model, an MM setup that has a constant magnetic gradient on one axis superimposed by a homogeneous time-varying magnetic field was used. After the magnetic characterization of the nanoparticles and calculations of the expected displacement in the setup, experiments were conducted. A laser Doppler vibrometer was used to quantify the small displacements at higher harmonics. The experimental results followed theoretical predictions. Deviations between model and experiment were attributed to a simplified mechanical modeling and temperature rise during measurements. It is concluded that in MM techniques, the nonlinear magnetization of nanoparticles must generally be considered to reconstruct quantitative parameters, to achieve optimum matching of fields and particles, or to exploit nanoparticle magnetization for tissue characterization. In addition, with the presented experimental setup, the magnetization properties of nanoparticles can be determined by MM techniques alone.
RESUMEN
Magnetic hyperthermia is a technique that describes the heating of material through an external magnetic field. Classic hyperthermia is a medical condition where the human body overheats, being usually triggered by a heat stroke, which can lead to severe damage to organs and tissue due to the denaturation of cells. In modern medicine, hyperthermia can be deliberately induced to specified parts of the body to destroy malignant cells. Magnetic hyperthermia describes the way that this overheating is induced and it has the inherent advantage of being a minimal invasive method when compared to traditional surgery methods. This work presents a particle system that offers huge potential for hyperthermia treatments, given its good loss value, i.e., the particles dissipate a lot of heat to their surroundings when treated with an ac magnetic field. The measurements were performed in a low-cost custom hyperthermia setup. Additional toxicity assessments on Jurkat cells show a very low short-term toxicity on the particles and a moderate low toxicity after two days due to the prevalent health concerns towards nanoparticles in organisms.
RESUMEN
BACKGROUND: Magnetic drug targeting (MDT) is an effective alternative for common drug applications, which reduces the systemic drug load and maximizes the effect of, eg, chemotherapeutics at the site of interest. After the conjugation of a magnetic carrier to a chemotherapeutic agent, the intra-arterial injection into a tumor-afferent artery in the presence of an external magnetic field ensures the accumulation of the drug within the tumor tissue. MATERIALS AND METHODS: In this study, we used superparamagnetic iron oxide nanoparticles (SPIONs) coated with lauric acid and human serum albumin as carriers for paclitaxel (SPIONLA-HSA-Ptx). To investigate whether this particle system is suitable for a potential treatment of cancer, we investigated its physicochemical properties by dynamic light scattering, ζ potential measurements, isoelectric point titration, infrared spectroscopy, drug release quantification, and magnetic susceptibility measurements. The cytotoxic effects were evaluated using extensive toxicological methods using flow cytometry, IncuCyte® live-cell imaging, and growth experiments on different human breast cancer cell lines in two- and three-dimensional cell cultures. CONCLUSION: The data showed that next to their high magnetization capability, SPIONLA-HSA-Ptx have similar cytostatic effects on human breast cancer cells as pure paclitaxel, suggesting their usage for future MDT-based cancer therapy.
