title: Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation.
abstract: BACKGROUND
  Magnetic nanoparticles (NPs) represent a tool for use in magnetic resonance imaging (MRI)-guided thermoablation of tumors using an external high-frequency (HF) magnetic field. To avoid local overheating, perovskite NPs with a lower Curie temperature (T c) were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis.
  
  
  METHODS
  Perovskite NPs (T c =66°C-74°C) were characterized and tested both in vitro and in vivo. In vitro, the cells suspended with NPs were exposed to a HF magnetic field together with control samples. In vivo, a NP suspension was injected into a induced tumor in rats. Distribution was checked by MRI and the rats were exposed to a HF field together with control animals. Apoptosis in the tissue was evaluated.
  
  
  CONCLUSIONS
  In vitro, the high concentration of suspended NPs caused an increase of the temperature in the cell sample, leading to cell death. In vivo, MRI confirmed distribution of the NPs in the tumor. The temperature in the tumor with injected NPs did not increase substantially in comparison with animals without particles during HF exposure. We proved that the deposited power from the NPs is too small and that thermoregulation of the animal is sufficient to conduct the heat away. Histology did not detect substantially higher apoptosis in NP-treated animals after ablation.
  
  
  CONCLUSIONS
  Magnetic particles with low T c can be tracked in vivo by MRI and heated by a HF field. The particles are capable of inducing cell apoptosis in suspensions in vitro at high concentrations only. However, their effect in the case of extracellular deposition in vivo is questionable due to low deposited power and active thermoregulation of the tissue.
authors.affiliation: MR-Unit, Radiodiagnostic and Interventional Radiology Department, Institute for Clinical and Experimental Medicine, Prague.
authors.forename: Vít
authors.initials: V
authors.lastname: Herynek
authors.affiliation: Department of Neuroscience, Institute of Experimental Medicine.
authors.forename: Karolína
authors.initials: K
authors.lastname: Turnovcová
authors.affiliation: Department of Magnetics and Superconductors, Institute of Physics, Czech Academy of Sciences, Prague.
authors.forename: Pavel
authors.initials: P
authors.lastname: Veverka
authors.affiliation: Department of Inorganic Technology, Faculty of Chemical Technology, University of Pardubice; SYNPO, akciová společnost, Pardubice.
authors.forename: Tereza
authors.initials: T
authors.lastname: Dědourková
authors.affiliation: Department of Analytical Chemistry, Institute of Chemical Technology.
authors.forename: Pavel
authors.initials: P
authors.lastname: Žvátora
authors.affiliation: Department of Neuroscience, Institute of Experimental Medicine.
authors.forename: Pavla
authors.initials: P
authors.lastname: Jendelová
authors.affiliation: MR-Unit, Radiodiagnostic and Interventional Radiology Department, Institute for Clinical and Experimental Medicine, Prague.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gálisová
authors.affiliation: Diabetes Center, Institute for Clinical and Experimental Medicine, Prague, Czech Republic.
authors.forename: Lucie
authors.initials: L
authors.lastname: Kosinová
authors.affiliation: Department of Neuroscience, Institute of Experimental Medicine.
authors.forename: Klára
authors.initials: K
authors.lastname: Jiráková
authors.affiliation: Department of Neuroscience, Institute of Experimental Medicine.
authors.forename: Eva
authors.initials: E
authors.lastname: Syková
mesh_terms: D055011:Ablation Techniques / Q000295:instrumentation / Q000379:methods*; D000818:Animals; D017610:Calcium Compounds / Q000737:chemistry; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000737:chemistry / Q000493:pharmacokinetics; D006979:Hyperthermia, Induced / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D059346:Magnets; D053758:Nanoparticles / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D017208:Rats, Wistar; D012822:Silicon Dioxide / Q000737:chemistry; D013535:Suspensions; D013696:Temperature; D014025:Titanium / Q000737:chemistry; D023041:Xenograft Model Antitumor Assays
chemical_list: D017610:Calcium Compounds; D003287:Contrast Media; D010087:Oxides; D013535:Suspensions; C059910:perovskite; D012822:Silicon Dioxide; D014025:Titanium
keywords: MRI; high-frequency magnetic field; hyperthermia; perovskite nanoparticles; tumor ablation