Gold-embellished mixed-valence manganite as a smart, self-regulating magnetoplasmonic nanomaterial

Abstract

Abstract In the present study, lanthanum-strontium manganite (LSM) particles were embellished with gold nanoparticles to create a magnetoplasmonic composite core-shell material enabling bimodal heating regimens upon exposure to an alternate current (AC) magnetic field and/or near-infrared (NIR) radiation. The composite particles were prepared by combined solid-state synthesis, mechanochemical processing and wet chemistry. The core crystals were round but faceted, often growing into an equilibrium shape conforming to the Wulff construction and the orthorhombic Pbnm crystal symmetry. They were also multi-domain but nanocrystalline, exhibiting superparamagnetic behavior as the result of evening the local anisotropies by the exchange interaction. The deposition of the gold nanoparticles onto the manganite core resulted in the red shift of the localized surface plasmon resonance due to interfacial effects. This deposition also improved the conditions for colloidal stability in water by increasing the surface charge density in the electric double layer surrounding the particles. The hybrid magnetoplasmonic particles were evaluated for their potential for use in cancer ablation therapies by measuring their aqueous heating dynamics in an ultralow AC magnetic field mimicking the magnetic hyperthermia (MH) condition of deep-seated tumors and the NIR light mimicking the photothermal (PT) condition. Aggregation of spherical, 5–10\xa0nm sized gold nanoparticles on the surface of LSM enhanced their NIR light absorption capacity. The heating of the particle suspensions was more intense in the PT mode than in the MH mode, but the latter mode allowed for the display of the smart, thermostatic behavior by the material. Namely, the stoichiometry of the manganite phase, La0·76Sr0·24MnO3, was adjusted to display the Curie temperature at 45.8\xa0°C after decoration with gold and the thermostatic effect at 43–44\xa0°C, with a potential to prevent the overheating of tissues during the MH treatments of cancer. The bimodal heating potential endows the particles with the ability to be used in personalized cancer therapies. These therapies would be able to adjust in situ the ratio between the two heating modes, one more suitable for superficial ablation (PT) and another one for the treatment of deeper tumors (MH).