RESUMO
PURPOSE: To evaluate selective apoptosis of Y79 retinoblastoma versus ARPE-19 retinal pigment epithelial cells by using different doses of dextran-coated iron oxide nanoparticles (DCIONs) in a magnetic hyperthermia paradigm. METHODS: Y79 and ARPE-19 cells were exposed to different concentrations of DCIONs, namely, 0.25, 0.5, 0.75, and 1 mg/ml. After 2 hours of incubation, cells were exposed to a magnetic field with a frequency of 250 kHz and an amplitude of 4 kA/m for 30 minutes to raise the cellular temperature between 42 and 46°C. Y79 and ARPE-19 cells incubated with DCION without magnetic field exposure were used as controls. Cell viability and apoptosis were assessed at 4, 24, and 72 hours after hyperthermia treatment. RESULTS: At 4 hours following magnetic hyperthermia, cell death for Y79 cells was 1%, 8%, 17%, and 17% for 0.25, 0.5, 0.75 and 1 mg/ml of DCION, respectively. Cell death increased to 47%, 59%, 70%, and 75% at 24 hours and 16%, 45%, 50%, and 56% at 72 hours for 0.25, 0.5, 0.75, and 1 mg/ml of DCIONs, respectively. Magnetic hyperthermia did not have any significant toxic effects on ARPE-19 cells at all DCION concentrations, and minimal baseline cytotoxicity of DCIONs on Y79 and ARPE-19 cells was observed without magnetic field activation. Gene expression profiling showed that genes involved in FAS and tumor necrosis factor alpha signaling pathways were activated in Y79 cells following hyperthermia. Caspase 3/7 activity in Y79 cells increased following treatment, consistent with the activation of caspase-mediated apoptosis and loss of cell viability by magnetic hyperthermia. CONCLUSION: Magnetic hyperthermia using DCIONs selectively kills Y79 cells at 0.5 mg/ml or higher concentrations via the activation of apoptotic pathways. TRANSLATIONAL RELEVANCE: Magnetic hyperthermia using DCIONs might play a role in targeted management of retinoblastoma.
RESUMO
We report an experimental investigation of time dependent anisotropic light scattering by an aqueous suspension of tetramethyl ammonium hydroxide coated Fe3O4 nanoparticles (approximately 6 nm) under the ON-OFF transient of an external dc magnetic field. The study employs the synchronized recording and measurement of the two magnetic-field-induced light-scattering patterns produced by two identical orthogonal He-Ne laser beams passing through the ferrofluid sample and propagating parallel and perpendicular to the applied field, respectively. From these patterns, we extract the time dependence of the induced optical anisotropy, which provides a measure of the characteristic time scale and kinematic response for field-induced structure formation in the sample. We propose that the time evolution of the scattering patterns, which is very fast at short times and significantly slower at long times, can be explained using a model based on a two-stage chain formation and coarsening processes.
