Design and Physicochemical Characterization of a Multifunctional Maisine-Based Microemulsion Incorporating Doxorubicin@Mn-Doped Magnetite Nanoparticles for MRI, Hyperthermia, and Drug Delivery

Multifunctional nanocarriers capable of integrating imaging, magnetic functionality, and controlled drug delivery represent an important research topic in cancer nanomedicine. Herein, Mn-doped (Fe3O4) magnetite nanoparticles (MNPs) were engineered and incorporated into a Maisine CC-based oil-in-water microemulsion (ME) to obtain a multifunctional nanoplatform for magnetic resonance imaging (MRI), hyperthermia, and controlled drug release. A series of Mn-doped MNPs (1–10% Mn:Fe3O4) was synthesized by coprecipitation. X-ray diffraction confirmed the preservation of the cubic spinel upon Mn incorporation. The Mn incorporation resulted in MNPs made of crystallites (~9–12 nm) whose magnetic properties were improved. Also, 10% Mn led to a very good magnetic heating efficiency under alternating magnetic fields with a specific absorption rate of ~111 W·g−1. The obtained MNPs proved to be T2-weighted MRI contrast agents, with an increase in the r2 values up to ~844 mM−1·s−1 after incorporation into ME. The optimized composition of Mn10% was subsequently loaded with doxorubicin (DOX) and integrated into ME. Drug-release studies revealed a biphasic profile, characterized by an initial burst phase followed by sustained release up to 48 h. These findings demonstrate that dopant-engineered MNPs combined with a ME carrier can provide a versatile platform for integrating magnetic hyperthermia potential, T2-weighted MRI contrast enhancement, and controlled chemotherapeutic delivery within a single nanostructured system.