Magnetic vortex γ-Fe2O3 nanospheres decorated with gold nanoparticles for dual hyperthermia treatment

In this work, multifunctional systems with potential applications for dual control of thermal heat delivery are developed. For this purpose, the nanosystems produced consist of vortex iron oxide nanospheres (VIONS) decorated with different amounts of gold nanoparticles (AuNPs). The VIONS were synthesized using the solvothermal reduction method, resulting in a 204 ± 24 nm diameter and meeting the requirements for biomedical applications. Magnetic measurements revealed that these systems are composed mainly of maghemite (γ-Fe₂O₃), exhibiting relatively low coercivity and moderate saturation magnetization, both of which serve as indicative attributes of an exceptional magnetic vortex state as validated by electron holography microscopy. The decoration with gold NPs was achieved through deposition-precipitation, involving the deposition of gold hydroxide on the surface of the previously amine-modified iron oxide NPs, followed by the concurrent reduction of Au³⁺. Furthermore, the gold NP size modulation was investigated by consecutively adding Au³⁺ to obtain gold NPs that interact with light differently depending on their size. The study provides crucial information that can aid the decoration of magnetic iron oxide nanospheres with AuNPs with tailored magnetic and optical properties; consequently, they may be promising candidates for magnetic and photothermal hyperthermia based on three-dimensional magnetic vortex structures.