In-gel study of the effect of magnetic nanoparticles immobilization on their heating efficiency for application in Magnetic Fluid Hyperthermia

• Published in: Journal of magnetism and magnetic materials 2019-02, Vol.471, p.504-512
• Main Authors: Avolio, Matteo, Guerrini, Andrea, Brero, Francesca, Innocenti, Claudia, Sangregorio, Claudio, Cobianchi, Marco, Mariani, Manuel, Orsini, Francesco, Arosio, Paolo, Lascialfari, Alessandro
• Format: Article
• Language: English
• Subjects: Adsorption; Brownian motion; Fluid dynamics; Gels; Hyperthermia; Magnetic fields; Magnetic Fluid Hyperthermia; Magnetic fluids; Magnetic nanoparticles; Nanoparticles; Relaxation times; Specific Absorption Rate; Stress relaxation; Superparamagnetism
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2018.09.111

•The hyperthermic efficiency SAR(H, f) of magnetite nanoparticles (MNP) is presented.•Three samples in water and agar gel with mean core diameters d = 10, 14, 18 nm.•10 nm sample: the effect of the Brownian motion suppression in gel is negligible.•14 and 18 nm samples: a significant decrease of the SAR in gel is observed.•Results warn about using MNP water solutions to predict heating efficiency in vivo. Recent studies on magnetic nanoparticles (MNPs) used for Magnetic Fluid Hyperthermia treatments have shown that Brownian rotation is suppressed when they are confined within a cell. To investigate this effect we conducted a systematic study of the Specific Absorption Rate (SAR) of colloidal suspensions of MNPs in water and gels at different agarose concentration. SAR measurements were conducted by varying the frequency (f = 110–990 kHz) and amplitude (up to 17 kA/m) of the applied alternating magnetic field (AMF). MNP samples with different diameter (d = 10, 14, and 18 nm) were used. Our results show that Néel relaxation dominates SAR with negligible contribution from Brownian motion for smaller MNPs (d = 10 nm). For the largest MNPs (d = 18 nm) we observed a more significant SAR decrease in gel suspensions as compared to those in solution. In particular, when applying AMFs as the ones used in a clinical setting (16.2 kA/m at f = 110 kHz), we measured SAR value of 67 W/g in solution and 25 W/g in gel. This experimental finding demonstrates that investigation of MNPs properties should be conducted in media with viscosity similar to the one found in mammalian tissues.