Nanoparticle (NP) assisted magnetic hyperthermia (NMH) is a clinically proven method for cancer treatment. High-Z magnetic NPs could also be a perspective object for combining hyperthermia with tumor radiosensitization. However, this application of NPs is little studied, and it is unclear as to what particle compositions one can rely on. Therefore, the present work focuses on the search of materials that combine alternating magnetic field induced heating and high atomic number related dose enhancement abilities. A theoretical evaluation of 24 promising NP compositions was performed: the values of dose enhancement factor (DEF) were determined for kilovoltage x-ray spectra (30–300 kVp), as well as specific absorption rate (SAR) values were calculated for various combinations of elemental compositions and particle size distributions. For the alternating magnetic fields with amplitude 75–200Oe and frequency 100kHz, the maximum obtained SAR values ranged from 0.35 to 6000Wg−1, while DEF values for studied compounds ranged from 1.07 to 1.59. The increase in the monodispersity of NPs led to a higher SAR, confirming well-known experimental data. The four types of SAR dependences on external magnetic field amplitude and anisotropy constant were found for various particle sizes. The most predictable SAR behavior corresponds to larger NPs (∼70–100 nm). Thus, based on these calculations, the most promising for the combination of NMH with radiotherapy, from a physical point of view, are La0.75Sr0.25MnO3, Gd5Si4, SmCo5, and Fe50Rh50. The greatest dose enhancement is expected for superficial radiotherapy (in the voltage range up to ∼60 kVp).

Nanocomposite capsules containing magnetite nanoparticles (MNPs) are promising multifunctional drug delivery systems for various biomedical applications. The presence of MNPs allows one to visualize these capsules via magnetic resonance imaging (MRI) and optoacoustic (photoacoustic) imaging. Moreover, we can ensure precise navigation and remote release via a magnetic field gradient and alternating magnetic fields, respectively. Magnetic dipole–dipole interaction between single capsules is important when a magnetic field is applied, and it is determined by a magnetic moment of each individual capsule. However, there is a lack of experimental data on the magnetic moment of a single capsule. Physical properties of capsules vary due to the change in the volume fraction of MNPs, as well as the capsule shell architecture. Therefore, two types of submicron capsules with different amounts of MNPs were synthesized. The first type of capsules was prepared by freezing-induced loading and layer-by-layer (LbL) assembly. The amount of MNPs varied by the number of freezing-induced loading cycles: two, four, and six. The second type of capsules is a nanocomposite shell formed using the LbL assembly of the oppositely charged polyelectrolytes and MNPs. Structural properties of both types of submicron capsules and MNPs were studied using transmission electron microscopy. Magnetic moments of nanocomposite shells placed in an external magnetic field were directly measured by optical tweezers and calculated based on vibrating-sample magnetometer measurements of the water suspension of nanocomposite shells. The magnetic moment of an individual shell depends on the amount of MNPs and increases as the number of MNPs per shell grows. Magnetic coupling parameters and the specific absorption rate were calculated. The obtained results can be applied while preparing drug carrier systems sensitive to alternating magnetic fields and navigated by gradient magnetic fields. They can also be taken into account in device development for navigating drug delivery systems and for the treatment based on alternating magnetic field-induced hyperthermia.

Magnetic oxides are promising materials for alternative health diagnoses and treatments. The aim of this work is to understand the dependence of the heating power with the nanoparticle (NP) mean size, for the manganite composition La0.75Sr0.25MnO3 (LSMO)—the one with maximum critical temperature for the whole La/Sr ratio of the series. We have prepared four different samples, each one annealed at different temperatures, in order to produce different mean NP sizes, ranging from 26 nm up to 106 nm. Magnetization measurements revealed a FC-ZFC irreversibility and from the coercive field as function of temperature we determined the blocking temperature. A phase diagram was delivered as a function of the NP mean size and, based on this, the heating mechanism understood. Small NPs (26 nm) is heated up within the paramagnetic range of temperature (T>Tc), and therefore provide low heating efficiency; while bigger NPs are heated up, from room temperature, within the magnetically blocked range of temperature (T<TB), and also provide a small heating efficiency. The main finding of this article is related with the heating process for NPs within the magnetically unblocked range of temperature (Tc>T>TB), for intermediate mean diameter size of 37 nm, with maximum efficiency of heat transfer.

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Hybrid multimodal nanoparticles, applicable simultaneously to the noninvasive imaging and therapeutic treatment, are highly demanded for clinical use. Here, Fe-Au core-satellite nanoparticles prepared by the method of pulsed laser ablation in liquids were evaluated as dual magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents and as sensitizers for laser-induced hyperthermia of cancer cells. The biocompatibility of Fe-Au nanoparticles was improved by coating with polyacrylic acid, which provided excellent colloidal stability of nanoparticles with highly negative ζ-potential in water (−38 ± 7 mV) and retained hydrodynamic size (88 ± 20 nm) in a physiological environment. The ferromagnetic iron cores offered great contrast in MRI images with r2 = 11.8 ± 0.8 mM−1 s−1 (at 1 T), while Au satellites showed X-ray attenuation in CT. The intravenous injection of nanoparticles enabled clear tumor border visualization in mice. Plasmonic peak in the Fe-Au hybrids had a tail in the near-infrared region (NIR), allowing them to cause hyperthermia under 808 nm laser exposure. Under NIR irradiation Fe-Au particles provided 24.1 °C/W heating and an IC50 value below 32 µg/mL for three different cancer cell lines. Taken together, these results show that laser synthesized Fe-Au core-satellite nanoparticles are excellent theranostic agents with multimodal imaging and photothermal capabilities.