Chinese Journal of Magnetic Resonance ›› 2015, Vol. 32 ›› Issue (2): 248-260.doi: 10.11938/cjmr20150208

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Optimizing Magnetic Nanoparticle Hyperthermia Effect in Magnetic Resonance Nanomedicine

WANG Chen-cai,LI Zhao,LIN Yung-ya*   

  1. Department of Chemistry and Biochemistry, University of California, Los Angeles 90095-1569
  • Received:2015-03-22 Revised:2015-05-15 Online:2015-06-05 Published:2015-06-05
  • About author:WANG Chen-cai (1990-), male, born in Jilin, PhD. candidate. His research focuses on MRI. *Corresponding author: LIN Yung-ya, Tel: +1-310 206 2856, E-mail: yylin@chem.ucla.edu.
  • Supported by:

    The Camille and Henry Dreyfus Foundation (TC-05-053), National Science Foundation (DMS-0833863, CHE-1112574, and CHE-1416598), and Hirshberg Foundation for Pancreatic Cancer Research.

Abstract:

Magnetic resonance hyperthermia is a new nano-medical therapy that emerges in recent years. In the presence of external alternating magnetic fields produced by MR instruments, magnetic nanoparticles accumulated at the tumor site can generate heat through Neel relaxation and/or Brownian relaxation. Through magnetic resonance hyperthermia, magnetic nanoparticles can serve as “molecular bullets” to kill cancer cells, leaving surrounding healthy tissues unaffected. Such hyperthermic effects can also be used for thermal activation and control releasing of cancer drugs. One major challenge of magnetic resonance hyperthermia is to optimize the heating efficiency of magnetic nanoparticle suspension. Heating efficiency depends on the size, physical properties, and aggregation state of magnetic nanoparticles. In this study, the thermodynamic behavior of magnetic nanoparticles and the aggregation/disruption of monomers/clusters under different temperatures were studied by 3D Metropolis Monte Carlo method. The relationship between the critical temperature for aggregation/disruption and the frequency of external magnetic field has been established through revised Langevin function.
Simulation results show that the relative content of aggregates in colloidal magnetic nanoparticle suspension decreased with the increase in temperature, and the aggregates disrupted completely into monomers at or above the critical temperature. In addition, increasing the frequency of external alternating magnetic field significantly lowered down the critical temperature, and there existed a critical frequency where the critical temperature stabilized and became unaffected by the frequency. Preheating the suspension under critical frequency will disrupt the aggregates into monomers and thus optimize the heating efficiency of magnetic nanoparticles.

Key words: magnetic resonance nanomedicine, magnetic nanoparticle, magnetic resonance hyperthermia, magnetic fluid aggregation, Monte Carlo simulation, critical frequency

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