A simple and rapid synthetic strategy for fabricating carboxy-functionalized iron oxide colloidal particles displaying reversible magnetic behavior is reported. The method is based on the pyrolysis of aerosols generated from ethanol/water solutions containing iron inorganic salts and mono- or polysaccharides. Essential to the success of the method are the use of hybrid (organo-inorganic) aerosols and the temperature of pyrolysis. The resulting material could be used in advanced biotechnological applications such as the magnetically assisted chemical separation of biocompounds.