Multimodal Magnetic Heating and Stimulation of Tissue


  • Minimally invasive in vivo control of biological stimuli by magnetic nanoparticles (MNPs)
  • In vivo magnetothermal control of neural activity in a mammalian system

Problem Addressed

Currently, stimulation of deep brain structures to ameliorate treatment-resistant symptoms of psychiatric and neurological disorders can only be achieved through permanently implanted electrodes.  Acoustic, electromagnetic induction, or optical signals have also been explored in the field of neuromodulation, but they are largely absorbed and scattered by surrounding tissues, causing substantial signal attenuation.  In contrast, low-radiofrequency alternating magnetic fields (AMF) offer a convenient form of non-invasive stimulus that can reach deep into the body, even into deep brain regions, due to the weak magnetic properties and low electrical conductivity of tissue. 


Magnetic nanoparticles (MNPs) with different coercivities can be heated selectively by varying the frequency and amplitude of an external alternating magnetic field (AMF).  This invention employs a mix of single domain MNPs and varying AMF parameters to generate local heat dissipation through magnetic hysteresis losses, which can then non-invasively activate distinct biological processes or cell types.  This multimodal magnetic stimulation allows selective heating of subpopulations of the MNPs occupying the same spatial region even when they are exposed to the same magnetic field.  Disclosed within the invention is a strategy to align the MNP magnetic moments to their easy axes (preferred magnetic directions), improving magnetic field-to-heat energy conversion, which will allow focusing MNPs to the specific volume of the body as well as limiting the volume affected by this multimodal magnetic stimulation.  The MNPs can be selectively affixed to target cells via surface functionalization and biochemical targeting. 


  • Virtually no interaction of the MNPs with biological tissues except when heated.  The MNPs also tend to remain where they’re placed, allowing for long-term treatment without the need for further invasive procedures
  • Weak interaction of AMFs with non-magnetic, non/weakly conductive materials (plastics, non-magnetic insulating ceramics, biological matters)
  • The possibility for precise targeting assisted by magnetic field
  • Adjustable heating rates by scaling up the frequencies in the method described herein