One-pot synthesis and biological assessment of fluorescent magnetite clusters coated with polydopamine and -analogues

In this work, a series of magnetite clusters has been synthesized in a one-pot solvothermal polyol reaction using as coating agent dopamine, 3,4-dihydroxybenzylamine, 2-aminomethyl-3-(3,4-dihydroxyphenyl)propionamide and 3,4-dihydroxybenzylidenehydrazine. Under the reaction conditions, these coating agents polymerize to give coatings of polydopamine (PDA) and PDA analogues. Polydopamine has recently become well-known as a polymer due to its superior coating ability as well as easy functionalization and biocompatibility. The newly synthesized magnetite clusters have been characterized by Fourier transform infrared spectroscopy (FTIR), transmission/scanning electron microscopy (TEM/SEM) as well as energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), thermogravimetric/differential thermal analysis (TGA/DTA), ultraviolet/visible spectroscopy (UVVIS), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and zeta-potential. The clusters were tested in vitro on normal human endothelial (HUVEC) and dermal fibroblastic as well as melanoma (A375) cells, and it was found that, besides being biocompatible, they were internalized and showed fluorescence depending on the combination of magnetite clusters and cell type. This gives them potential applications as theranostics, for simultaneous fluorescent/MRI bioimaging and/or hyperthermia treatments.