The multidisciplinary nanotechnology research field encompasses the design, synthesis, characterization and handling of particles with a diameter of 1 to 100 nm. These nanoparticles have attracted a lot of interest as specific drug delivery systems to sites of interest, such as the vascular wall, which undergoes pathological changes following the installation of cardiovascular diseases (CVD) [1]. Polyphenols, plant-derived organic compounds, have well documented antiinflammatory activity and are actively investigated currently for their therapeutic potential in the treatment of CVD [2]. The aim of the present study was the synthesis, characterization, as well as testing the cytotoxic effect of polyphenol-loaded magnetic nanoparticles (MNPs) on the human endothelial cell (EC) line EA.hy926. Chitosan-coated MNPs and loaded with polyphenols (caffeic acid, tannic acid and gallic acid) were obtained by the co-precipitation method [3]. These MNPs were physico-chemically characterized by different methods: the structure was determined by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy, the morphology was determined by Scanning Electron Microscopy (SEM) and the hydrodynamic diameter in aqueous solution was measured by Dynamic Light Scattering (DLS). EA.hy926 cells were incubated for 24 hours with different concentrations of MNPs and polyphenol-loaded MNPs, ranging from 10 to 500 μg/ml. The cells exposed to corresponding concentrations of free polyphenols, ranging from 1 to 50 μg/ml were used for comparison. Cell viability was assessed via XTT {2,3-bis (2-methoxy-4nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide} assay. Following the physico-chemical characterization, it was concluded that the primary particles are nanometer-sized (about 3-4 nm) and have a spherical shape, but their morphology changes depending on the therapeutic agent loaded. The hydrodynamic diameter of the MNPs dispersed in water was around 700 nm. In general, the EC viability is not highly affected by the exposure for 24 hours to Fe3O4 MNPs. Only in the case of incubation of EC with caffeic acidloaded MNPs, a gradual, dose-dependent decrease of viability could be observed but this was not greater than 35%, corresponding to the maximum concentration tested (500 μg/ml). In conclusion, chitosan-coated polyphenol-loaded MNPs tested in this study do not significantly induce EC death up to a concentration of 200 μg/ml MNPs and guides to further studies to search for their potential benefits as anti-inflammatory medicines.