Nanoscale Heat Transfer from Magnetic Nanoparticles and Ferritin in an Alternating Magnetic Field
Recent suggestions of nanoscale heat confinement on the surface of synthetic and biogenic magnetic nanoparticles during heating by radio frequency-alternating magnetic fields have generated intense interest because of the potential utility of this phenomenon for noninvasive control of biomolecular and cellular function. However, such confinement would represent a significant departure from the classical heat transfer theory. Here, we report an experimental investigation of nanoscale heat confinement on the surface of several types of iron oxide nanoparticles commonly used in biological research, using an all-optical method devoid of the potential artifacts present in previous studies. By simultaneously measuring the fluorescence of distinct thermochromic dyes attached to the particle surface or dissolved in the surrounding fluid during radio frequency magnetic stimulation, we found no measurable difference between the nanoparticle surface temperature and that of the surrounding fluid for three distinct nanoparticle types. Furthermore, the metalloprotein ferritin produced no temperature increase on the protein surface nor in the surrounding fluid. Experiments mimicking the designs of previous studies revealed potential sources of the artifacts. These findings inform the use of magnetic nanoparticle hyperthermia in engineered cellular and molecular systems.
© 2020 Biophysical Society. Received 11 November 2019, Accepted 21 January 2020, Available online 1 February 2020. The authors thank Polina Anikeeva, Arnd Pralle, Michael Christiansen, George Varnavides, Pradeep Ramesh, and Markus Meister for helpful discussions and Yuxing Yao for assistance with electron microscopy. This research was supported by the Burroughs Wellcome Career Award at the Scientific Interface, the Packard Fellowship in Science and Engineering, the Rosen Center for Bioengineering, and the Center for Environmental Microbial Interactions at Caltech. Author Contributions: H.C.D. and M.G.S. conceived the study. H.C.D. constructed the experimental apparatus, prepared the reagents, acquired the data, and analyzed the data. H.P. assisted in apparatus construction and data acquisition. S.K., J.-H.L., T.-H.S., and J.C. synthesized and functionalized magnetic nanoparticles. H.C.D. and M.G.S. wrote the manuscript with input from all other authors. M.G.S. supervised the research.
Supplemental Material - 1-s2.0-S0006349520301016-mmc1.pdf