Barrera Gabriele, Allia Paolo, Tiberto Paola
INRiM, Advanced Materials Metrology and Life Sciences, Turin, Italy.
Sci Rep. 2024 May 10;14(1):10704. doi: 10.1038/s41598-024-61580-8.
Driving immobilized, single-domain magnetic nanoparticles at high frequency by square wave fields instead of sinusoidal waveforms leads to qualitative and quantitative improvements in their performance both as point-like heat sources for magnetic hyperthermia and as sensing elements in frequency-resolved techniques such as magnetic particle imaging and magnetic particle spectroscopy. The time evolution and the frequency spectrum of the cyclic magnetization of magnetite nanoparticles with random easy axes are obtained by means of a rate-equation method able to describe time-dependent effects for the particle sizes and frequencies of interest in most applications to biomedicine. In the presence of a high-frequency square-wave field, the rate equations are shown to admit an analytical solution and the periodic magnetization can be therefore described with accuracy, allowing one to single out effects which take place on different timescales. Magnetic hysteresis effects arising from the specific features of the square-wave driving field results in a breakthrough improvement of both the magnetic power released as heat to an environment in magnetic hyperthermia treatments and the magnitude of the third harmonic of the frequency spectrum of the magnetization, which plays a central role in magnetic particle imaging.
通过方波场而非正弦波形以高频驱动固定化的单畴磁性纳米颗粒，在其作为磁热疗的点状热源以及诸如磁粒子成像和磁粒子光谱等频率分辨技术中的传感元件的性能方面，带来了定性和定量的提升。通过一种速率方程方法获得了具有随机易轴的磁铁矿纳米颗粒循环磁化的时间演化和频谱，该方法能够描述在生物医学的大多数应用中所关注的颗粒尺寸和频率的时间相关效应。在高频方波场存在的情况下，速率方程被证明允许有解析解，因此可以精确描述周期性磁化，从而能够挑出在不同时间尺度上发生的效应。由方波驱动场的特定特征引起的磁滞效应导致在磁热疗中作为热量释放到环境中的磁功率以及在磁粒子成像中起核心作用的磁化频谱三次谐波幅度都有突破性的提升。
