铁氧体纳米颗粒在射频场中的加热行为及机制的研究

Heat generated by hysteresis loss in radio-frequency (RF) field for magnetic nanoparticles (MNPs) has the potential to be a powerful, non-invasive technique for biomedical applications. In order to minimize the potential side effects arising in magnetic hyperthermia, MNPs should be applied at a low dose as possible, while this dosage can still maintain a sufficient heating source. To satisfy the latter, magnetic NPs with higher energy transfer efficiency are mostly preferred. Therefore, to develop new NPs with sufficient heating ability is of great challenge. This project put forwards to design M1-xNxFe2O4（M, N=Co, Mn, Zn）multi-component MNPs. Heating capacity dependence of size, morphology and anisotropy will be studied systematically; the effect of orientation of MNPs on heat capacity will be investigated. These studies help to understand the mechanism of heating generation in RF field and finally find out the physical origin of heating generation. Another scientific question is whether there is a significant temperature gradient at the nanoscale. We propose to encapsulate dye molecules at precisely controlled nanometer distances to the NP surface, so that local temperature and gradient can be measured in real time. The heat transport across the NP, surfactants and solvent will be studied. At last, we will develop a novel MNPs with high heating efficiency exposed in RF field, which can be used for hyperthermia and targeted drug delivery area.

磁性纳米颗粒(MNPs)在交变磁场中因能量损耗而致的热效应在生物医学领域有着重要的应用价值。由于目前毒副作用的不确定性，临床治疗中要求MNPs在射频场中具有高的产热效率，从而尽可能减少其用量。提高MNPs在射频场中的产热效率一直是国际上具有挑战性的课题。本项目提出构建M1-xNxFe2O4（M, N=Co, Mn, Zn）多元纳米颗粒，通过研究MNPs的成分、尺寸、形貌对其在交变磁场中的磁化行为及产热能力的影响规律，以及当布朗弛豫被阻止后磁性纳米颗粒的取向度对其在交变磁场中产热行为的影响规律，阐明MNPs在射频场中的产热机制，揭示影响磁性纳米颗粒在交变磁场中产热行为的物理根源；同时，本项目还将研究MNPs纳米尺度上温度梯度的分布规律及局域加热机制。通过以上研究，本项目将为制备单分散、具有高产热效率的磁性纳米颗粒提供理论指导，发展可用于磁热疗及可控性药物释放的新型磁性材料。

本项目在铁氧体纳米颗粒的基础上通过添加Co、Mn、Zn元素对纳米颗粒的饱和磁矩和磁各向异性进行调控，Co0.03Mn0.27Fe2.7O4/SiO2的纳米复合颗粒在交变磁场（f = 380 kHz, H = 33 kA/m）中的产热效率3417 W/gmetal，接近理论计算值。发展了生物相容性比Fe3O4优异的Zn0.3Fe2.7O4/SiO2磁性纳米颗粒，该纳米颗粒在生物安全极限之内表现出优异的磁热性能。利用临床医用骨水泥或甘油为介质，研究了布朗驰豫以及磁性纳米颗粒取向度对其在交变磁场下的产热行为的影响规律。在纳米颗粒表面包覆一层SiO2，将荧光染料插入SiO2壳层的不同厚度处，制备了具有磁光二重性的纳米复合颗粒。本项目的研究为用于磁热疗的纳米颗粒的成分设计提供了理论指导，发展了生物相容性好并具有高产热效率的磁性纳米颗粒，将磁性纳米颗粒的磁热疗在临床肿瘤治疗和诊断中的应用向前推进了一步。