Background: Magnetic fluid heating has great potential in the fields of thermal medicine and cryopreservation. However, variations among experimental parameters, analysis methods and experimental uncertainty make quantitative comparisons of results among laboratories difficult. Herein, we focus on the impact of calculating the specific absorption rate (SAR) using Time-Rise and Box-Lucas fitting. Time-Rise assumes adiabatic conditions, which is experimentally unachievable, but can be reasonably assumed (quasi-adiabatic) only for specific and limited evaluation times when heat loss is negligible compared to measured heating rate. Box-Lucas, on the other hand, accounts for heat losses but requires longer heating. Methods: Through retrospective analysis of data obtained from two laboratories, we demonstrate measurement time is a critical parameter to consider when calculating SAR. Volumetric SAR were calculated using the two methods and compared across multiple iron-oxide nanoparticles. Results: We observed the lowest volumetric SAR variation from both fitting methods between 1–10 W/mL, indicating an ideal SAR range for heating measurements. Furthermore, our analysis demonstrates that poorly chosen fitting method can generate reproducible but inaccurate SAR. Conclusion: We provide recommendations to select measurement time for data analysis with either Modified Time-Rise or Box-Lucas method, and suggestions to enhance experimental precision and accuracy when conducting heating experiments.
Bibliographical noteFunding Information:
R.I. is an inventor on nanoparticle patents, and all patents are assigned to either The Johns Hopkins University or Aduro BioTech, Inc. R.I. consults for Imagion Biosystems, a company developing imaging with magnetic iron oxide nanoparticles. R.I received partial funding from the National Cancer Institute (5R01CA194574-02 and 5R01CA247290). J.C.B. is an inventor on several patents that use iron oxide and gold nanoparticles to heat biomaterials for regenerative medicine purposes. These patents are assigned to the University of Minnesota. H.R., A.S. and J.C.B. received partial funding from NIH R01 HL135046 & R01 DK117425 which are related to iron oxide nanoparticle rewarming of vitrified biomaterials. J.C.B. was also supported by the Bakken Chair for Engineering in Medicine at the University of Minnesota. All other authors report no conflicts of interest. The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official view of the Johns Hopkins University, University of Minnesota, NIH, or other funding agencies.
- Magnetic iron oxide nanoparticles
- data analysis
- magnetic fluid hyperthermia
- specific absorption rate calculation