Theranostic strategies are advancing personalized medicine, with particularly impactful applications in cancer treatment. Among these, magnetic hyperthermia (MH) stands out, employing high-frequency magnetic field (MF) and magnetic nanoparticles (MNPs) to selectively target and heat cancerous cells. Real-time temperature monitoring and MNP localization, however, remain significant challenges in clinical translation. Previous studies have shown that magnetomotive ultrasound (MMUS) effectively addresses these challenges. Developing an automated and synchronized transition between MMUS and MH within an integrated platform is, however, challenging due to incompatible frequency requirements, with MH operating in the 0.1–1 MHz range and MMUS requiring lower frequency MF below 100 Hz. This study aimed to develop an automated platform enabling interleaved MF applications using a single excitation coil for both MH and MMUS. We propose using a high-frequency ferrite transformer to couple both generators for automated electronic switching. The platform used a multipurpose air-core inductor capable of producing MF pulses up to 205 kA/m (with currents reaching 2.16 kA) for MMUS, interleaved with MH stimulation at 170 kHz and 28 kA/m. The MH framework induced an $8~^{\circ }$ C temperature increase in 1 cm3 ferrofluid samples at an MF strength of 15 kA/m. Preliminary phantom experiments demonstrated the system’s capability to localize MNPs noninvasively, monitor thermal variations up to $1~^{\circ }$ C, and visualize tissue property changes during MH, showcasing promising integration of MMUS and MH.

Background/Objectives: Magnetic nanoparticles (MNPs) have gained attention in theranostics for their ability to combine diagnostic imaging and therapeutic capabilities in a single platform, enhancing targeted treatment and monitoring. Surface coatings are essential for stabilizing MNPs, improving biocompatibility, and preventing oxidation that could compromise their functionality. Natural rubber latex (NRL) offers a promising coating alternative due to its biocompatibility and stability-enhancing properties. While NRL-coated MNPs have shown potential in applications such as magnetic resonance imaging, their effectiveness in theranostics, particularly magnetic hyperthermia (MH) and photoacoustic imaging (PAI), remains underexplored. Methods: In this study, iron oxide nanoparticles were synthesized via coprecipitation, using NRL as the coating agent. The samples were labeled by NRL amount used during synthesis: NRL-100 for 100 μL and NRL-400 for 400 μL. Results: Characterization results showed that NRL-100 and NRL-400 samples exhibited improved stability with zeta potentials of −27 mV and −30 mV, respectively and higher saturation magnetization values of 79 emu/g and 88 emu/g of Fe₃O₄. Building on these findings, we evaluated the performance of these nanoparticles in biomedical applications, including magnetomotive ultrasound (MMUS), PAI, and MH. NRL-100 and NRL-400 samples showed greater displacements and higher contrast in MMUS than uncoated samples (5, 8, and 9 µm) at 0.5 wt%. In addition, NRL-coated samples demonstrated an improved signal-to-noise ratio (SNR) in PAI. SNR values were 24.72 (0.51), 31.44 (0.44), and 33.81 (0.46) dB for the phantoms containing uncoated MNPs, NRL-100, and NRL-400, respectively. Calorimetric measurements for MH confirmed the potential of NRL-coated MNPs as efficient heat-generating agents, showing values of 43 and 40 W/g for NRL-100 and NRL-400, respectively. Conclusions: Overall, NRL-coated MNPs showed great promise as contrast agents in MMUS and PAI imaging, as well as in MH applications.

We report an experimental investigation on the dependence of the specific loss power with the equilibrium magnetic susceptibility in Zn-substituted Co ferrite nanoparticles. Specifically, we scrutinize the structural, magnetic and thermal properties of ZnxCo1-xFe2O4 nanoparticles with x = 0.0, 0.2, 0.5, 0.8 and 1.0, and verify the influence of the substitution of cobalt by zinc in the structure of the ferrite. From magnetic hyperthermia experiments, we disclose the existence of an optimal zinc content in the structure of the ferrite promoting the highest heating, thus maximizing the specific loss power. The question then arises here is why ZnxCo1-xFe2O4 nanoparticles with x=0.8 maximizes the specific loss power in such Zn-substituted Co ferrite. From the linear fit of the magnetization at low fields, we estimate the equilibrium magnetic susceptibility and observe its highest value for the very same Zn content. Hence, we demonstrate that the specific loss power for superparamagnetic nanoparticles at the linear magnetization regime directly relies on the magnetic susceptibility at low fields. Our results confirm the importance of equilibrium susceptibility as a key parameter for optimizing magnetic hyperthermia and specific loss power.

The tumor microenvironment, characterized by higher acidity, hypoxia, and dense cellular structures, plays a pivotal role in cancer progression, therapeutic resistance, and treatment response. Nanoparticle-based contrast agents enable the precise delineation of solid regions within heterogeneous tumors through advanced molecular imaging techniques. Since 1956, ultrasound (US) medical imaging has provided essential anatomical and functional insights about internal organs. More recently, magnetomotive ultrasound (MMUS) has emerged as a promising imaging modality, using a modulated magnetic field to exert force on superparamagnetic iron oxide nanoparticles (SPIONs), inducing motion in the surrounding tissues through mechanical coupling. In parallel, magnetic hyperthermia (MH), which employs localized heating by alternating magnetic fields, has demonstrated significant potential in selectively destroying cancer cells while sparing healthy tissues. This review summarizes the current state of IONP-based contrast agents, with particular emphasis on their use in MH for cancer treatment, as well as their potential in multimodal imaging, including MMUS, and photoacoustic (PA) imaging. The advantages and limitations of IONPs in tumor detection and characterization are discussed, examining the development of surface-functionalized MNPs, and analyzing how material properties and environmental factors affect their diagnostic and therapeutical performance. Finally, strategies for combining MMUS and PA modalities for pre-clinical cancer imaging are proposed.