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In Situ Measurement of Magnetization Relaxation of Internalized Nanoparticles in Live Cells.

Soukup, Dalibor; Moise, Sandhya; Céspedes, Eva; Dobson, Jon; Telling, Neil D.


Dalibor Soukup

Sandhya Moise

Eva Céspedes

Jon Dobson


Magnetization relaxation mechanisms strongly influence how magnetic nanoparticles respond to high-frequency fields in applications such as magnetic hyperthermia. The dominant mechanism depends on the mobility of the particles, which will be affected in turn by their microenvironment. In this study AC susceptometry was used to follow the in situ magnetic response of model systems of blocked and superparamagnetic nanoparticles, following their cellular internalization and subsequent release by freeze-thaw lysis. The AC susceptibility signal from internalized particles in live cells showed only Néel relaxation, consistent with measurements of immobilized nanoparticle suspensions. However, Brownian relaxation was restored after cell lysis, indicating that the immobilization effect was reversible and that nanoparticle integrity was maintained in the cells. The results presented demonstrate that cellular internalization can disable Brownian relaxation, which has significant implications for designing suitable nanoparticles for intracellular hyperthermia applications. Further to this, the results highlight the possibility that particles could be released in reusable form from degrading cells following hyperthermia treatment, and subsequently reabsorbed by viable cells.


Soukup, D., Moise, S., Céspedes, E., Dobson, J., & Telling, N. D. (2015). In Situ Measurement of Magnetization Relaxation of Internalized Nanoparticles in Live Cells. ACS nano, 9(1), 231-240.

Journal Article Type Article
Acceptance Date Jan 6, 2015
Publication Date Jan 9, 2015
Journal ACS Nano
Print ISSN 1936-0851
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 9
Issue 1
Pages 231-240
Keywords AC susceptibility; hyperthermia; magnetic nanoparticles; magnetization relaxation; cellular internalization
Publisher URL