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Simultaneous Measurements of Magnetic Nanoparticle Temperature and Relaxation Time

J Weaver1*, Y Shi2 , (1) Dartmouth-Hitchcock Medical Center, Lebanon, NH, (2) Dartmouth College, Hanover, NH


(Sunday, 7/14/2019) 3:30 PM - 4:00 PM

Room: Exhibit Hall | Forum 8

Purpose: We are using magnetic nanoparticle (NP) methods to explore and characterize the microenvironment in vitro, ex vivo and in vivo. The NP antibody targeting can couple Brownian rotational relaxation to the microenvironment in several ways to make measurements of temperature, viscosity, cell uptake, molecular biomarker concentrations and NP binding with high sensitivity. However, the effects of temperature cannot be isolated from relaxation and the inability to isolate the two, limits the accuracy of the measurements. We are proposing a method of isolating temperature effects from relaxation effects so fever will not be confused with fewer biomarker molecules or with less cell uptake.

Methods: The harmonics of the magnetization generated by magnetic NPs are complex and complicated functions that are most accurately described by stochastic differential equations either in a Langevin form or in an equivalent Fokker–Planck form. Dimensional analysis and the resulting scaling arguments can be used to measure changes in temperature if the amplitude of the applied magnetic field is swept and changes in viscosity if the frequency of the applied magnetic field is swept. In this effort, we show that if both the frequency and the amplitude are swept, both the temperature and the viscosity can be found simultaneously because the NP dynamics are determined by two dimensionless variables. The first is the ratio of the amplitude of the applied field and the temperature. The second is the product of the relaxation time and the frequency of the applied field.

Results: The temperature and relaxation time can be simultaneously measured with 1o K mean error in temperature and 0.01 mPas mean error in viscosity using our current spectrometer.

Conclusion: The temperature and the relaxation time can be measured simultaneously by scaling in both the amplitude and frequency of the applied magnetic field.

Funding Support, Disclosures, and Conflict of Interest: R21EB021456


Not Applicable / None Entered.


Not Applicable / None Entered.

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