Fe3O4@SiO2-Re-PEG nanoparticles as magneto-optical dual probes and new PDT agents

The use of nanoparticles (NPs) in biomedicine has attracted much attention in the past decades, for their remarkable potential in the resolution of many long-standing problems. Preferential accumulation in solid tumors can be observed for NPs in a size range of 10-100 nm, for the so called EPR (Enhanced Permeability and Retention) effect, which can be further enhanced if the surface is functionalized with “stealth” molecules or polymers able to make the NPs undetectable by the reticulo-endothelial system (RES). Furthermore NPs, thanks to their large surface area, can be loaded with huge amounts of small molecules, integrating different diagnostic and therapeutic functionalities in a single nanosized system. In this work we have prepared a dual probe nanocomposite, constituted by an iron oxide magnetic core and a compact silica shell functionalized with a luminescent complex, [Re(phen)(CO)3(py-upts)]OTf (py-upts = 1-(pyridin-4-yl)-3-(3-(triethoxysilyl)propyl)urea) and coated by a polyethyleneglycol (PEG) layer. The photophysical and relaxivity properties of the Fe3O4@SiO2-Re-PEG nanocomposites have been measured, to check the possible mutual interference between the magnetic core and the luminescent shell. Primary cell penetration tests have already been conducted in order to investigate the ability of NPs to pass the cell membrane, by means of two photon emission (TPE) confocal microscopy. We also investigated the ability of the nanocomposites to act as sensitizers for photodynamic therapy (PDT), producing cytotoxic singlet oxygen upon irradiation, both in cuvette and in vitro on A549 cells.