γFe 2 O 3 -based nanoparticles were synthesized by laser pyrolysis using various optimized Fe(CO) 5 , O 2 and C 2 H 4 flow ratios in the reactive mixture, and different laser power values. Depending on particular conditions, two different iron oxide-based nanoparticles (MNPs) were synthesized, with a hydrophilic or hydrophobic behavior, both presenting a high magnetization saturation (around 70 emu/g). TEM, EDX, XRD and magnetic analyses were performed for a comprehensive characterization. The raw powders were successfully dispersed in aqueous media using l -DOPA as stabilizing agent. Dispersed samples, with or without stabilization agents, have been tested and DLS measurements proved their good stability, with the hydrodynamic diameter varying between 70 and 150 nm when the stabilizing agent was used. Thermal conductivity and viscosity tests on l -DOPA-functionalized MNPs suspensions reveal the increasing (up to 40%) of their thermal conductivity, accompanied by a viscosity increase of only 5%, validating them as thermal transfer fluids. Water-based nanoparticle dispersions and also those stabilized with l -DOPA proved a good biocompatibility, as demonstrated by a preliminary in vitro study on mouse primary leukocytes and human breast carcinoma cell line MCF-7; although ingested by the investigated cells, MNPs do not decrease cellular viability and proliferation.