The influence of physicochemical parameters of nanoparticles on the effectiveness of magnetic hyperthermia
This paper systematizes data on the influence of the physicochemical parameters (size, shape, and composition) of magnetic nanoparticles on the characteristics of magnetic hyperthermia (specific absorption coefficient). This data is used to develop an optimization strategy within the strict biomedical limitations of the amplitude and frequency of an alternating magnetic field. An analysis of current literature data is conducted, including fundamental works on the theory of linear response and dynamic hysteresis, as well as the results of experimental studies of collective effects in colloidal systems. Energy dissipation mechanisms (Néel and Brown relaxation, hysteresis losses) are considered depending on the size, shape, composition, and concentration of magnetic nanoparticles. Particular attention is paid to the influence of interparticle dipole-dipole interactions and aggregation on magnetic anisotropy. It has been demonstrated that the clinical application of hyperthermia is limited by the Brezwich–Atkinson criterion (Hf < 4.85 ∙ 108 A/(m ∙ s)), which excludes nonspecific tissue heating by eddy currents. Under conditions of fixed field parameters (H ≈ 10…20 kA/m), maximum heat generation is achieved not by increasing the generator power, but by optimizing the nanoparticles, namely, by fine-tuning the coercive force Hc of the particles. It has been established that the optimal specific absorption coefficient is achieved by matching Hc with the available field amplitude H, which requires a transition from superparamagnetic regimes to controlled hysteresis in single-domain particles. A nonmonotonic dependence of the specific absorption coefficient on concentration was revealed due to the competition between the increase in the anisotropy value in aggregates and the suppression of Brownian relaxation. An algorithm for combined optimization of nanoparticles has been developed, taking into account the synergy between size, shape, composition, and degree of aggregation. It has been demonstrated that increased heating efficiency within a safe «biomedical window» is possible through the use of particles with controlled anisotropy, which ensures the opening of the hysteresis loop at low field amplitudes, opening the way for lower therapeutic doses of nanomaterials and minimizing side effects.
Authors: N. A. Lisaevich, A. S. Dmitrieva, V. A. Ryzhov, Yu. V. Bogachev, A. V. Nikitina, Ya. Yu. Marchenko
Direction: Physics
Keywords: magnetic hyperthermia, specific absorption coefficient (SAR), magnetic nanoparticles, biomedical limitations, the Brezwich–Atkinson criterion, magnetic anisotropy, aggregation, hysteresis losses
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