Introduction:
One of the most interesting objects from the point of view of application in biomedicine is hybrid structures based on magnetic nanoparticles (NPs) and noble metal NPs, which make it possible to simultaneously introduce two types of ligands onto the surface of NPs. This type of dumbbell-shaped NP opens up the possibility of their functionalization for further use in photodynamic cancer therapy (PDT) and fluorescence diagnostics (FD) (a combination of a photosensitizer (PS) for therapy and a fluorophore (FP) for platform detection). The aim of this work was to synthesize and study Fe3O4-Au NPs with a "dumbbell" structure as a bifunctional platform for the treatment of oncological diseases. As a result of the decomposition of iron pentacarbonyl in diphenyl ethers in the presence of hydrogen tetrachlorurates, hybrid NPs of magnetite and gold were synthesized with Fe3O4 size 10.8 ± 1.5 nm and Au 4.4 ± 0.8 nm (according to TEM data) stabilized with oleic acid. According to the results of X-ray phase analysis, the synthesized NPs have a spinel-type crystal structure with a lattice period of 0.8387 nm. According to the results of measuring the magnetic properties, the NPs had a saturation magnetization of 62 Am² kg (Fe3O4)^–1 and a coercive force of 13 Oe. The NPs were modified with 3,4-dihydroxyphenylacetic acid (DOPAC) for subsequent coating with a stabilizing polyethylene glycol (PEG) by the carbodiimide method. Since it is necessary to combine two different substances (PS and FP) in one system, Fe3O4-Au NPs (stabilized) were used as a “link”. Modification of NPs with DOPAC and PEG followed by activation of EDC/NHS makes it possible to efficiently attach a PS to the magnetic surface of NPs in a two-phase system (water–DMSO). The hydrodynamic size of the Fe₃O₄-Au/DOPAC/PEG/PS/FP system was 35.99 nm (dynamic light scattering method). When studying the optical properties of the synthesized platform Fe₃O₄-Au/PS/FP, the emission and absorption peaks of PS and FP were identical to the peaks of PS and FP in solution. The use of a disulfide derivative of FP makes it possible to provide covalent conjugation with the gold surface. In addition, NMR and IR analyzes confirmed the structure of the system. It was shown that the systems Fe3O4-Au/PS and Fe3O4-Au/FP could be internalized by CT26 colon cancer cells with the preservation of optical properties. In the future, it is planned to calculate the physicochemical parameters of the synthesized system for optimization and implementation of the final platform in vivo.

Acknowledgement:
This work was supported in part by the State Registration Theme AAAA-A21-121011290089-4 and 121041500039-8. The equipment was purchased within the framework of the Development Program of the Lomonosov Moscow State University. Abstract was not submitted elsewhere and published here firstly.

Conflicts of Interest:
The authors declare that they have no conflict of interest in the publication of this article. The authors have no conflicts of interest to report in this work.