One of the most interesting objects from the point of view of application in biomedicine is hybrid structures based on magnetic nanoparticles (NPs) and NPs of noble metals (including gold), which make it possible to simultaneously introduce two types of ligands onto the surface of NPs for their further use for photodynamic cancer therapy (PDT) [a combination of a photosensitizer (PS) for therapy and a fluorophore (FP) for platform detection]. Synthesis of the system is a promising direction and is of interest to scientists.
In connection with the above, the aim of this work was the synthesis and study of Fe₃O₄-Au NPs with the ‘dumbbell’ structure as a bifunctional platform for PDT of oncological diseases using fluorescent diagnostics.
As a result of the decomposition of iron pentacarbonyl in diphenyl ethers in the presence of hydrogen tetrachlorourates, hybrid magnetite-gold NPs with Fe₃O₄ size of 10.8 ± 1.5 nm and Au 4.4 ± 0.8 nm (according to transmission electron microscopy) stabilized with oleic acid were synthesized. According to the results of x-ray phase analysis, the synthesized nanoparticles have a ‘spinel’ type crystal structure with a lattice period of 0.8387 nm (an intermediate value between magnetite and maghemite). 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. Further, the NPs were modified with 3,4-dihydroxyphenylacetic acid (DOPAC) for further coating with a stabilizing polyethylene glycol (PEG) using the carbodiimide method.
For further grafting of chromophores, a series of PS based on bacteriochlorin and FP based on cyanine were studied for use as components of a bifunctional platform for PDT. Since two different colored substances (PS and FP) must be combined in one system, the synthesized Fe₃O₄-Au NPs with the ‘dumbbell’ structure (stabilized) were used as a ‘link’. The FRET pair FP/PS (PS/Cy5) was selected and the optical properties were studied. Modification of NPs with DOPAC and PEG followed by activation by EDC/NHS (carbodiimide method) makes it possible to effectively attach a PS to the magnetic surface of NPs in a two-phase system (water–DMSO). In the future, it is planned to ‘cross-link’ the fluorophore (Cy5) onto the gold surface, study the optical properties of the final platform Fe₃O₄-Au/PS/FP, and calculate the physicochemical parameters of the synthesized system to optimize the system and conduct therapy in vitro and in vivo.