Magnetic nanoparticles such as magnetite (Fe3O4) or cobalt ferrite (CoFe2O4) were synthesized in presence of oleic acid by the thermodecomposition method. These nanoparticles were modified with silane-functional molecules to graft acrylate (CH2=C(CH3)-C(=O)-O) end groups onto the nanoparticles surface. Functionalization of these modified nanoparticles with N-isopropyl acrylamide monomers such as NIPAM and NIPMAM were carried out by free radical polymerization using an azo-initiator such as AIBN and a methyl bis-acrylamide (MBA) crosslinking agent. The hydrodynamic size of these functionalized nanoparticles was studied as function of temperature. Measurements of the specific absorption rate (SAR) of magnetic nanoparticles coated with thermo-responsive polymeric shells were performed in presence of a magnetic field to determine their potential therapeutic applications. Fluorescent magnetic nanoparticles were also synthesized by the incorporation of a fluorescent modified acrylamide monomer (FMA). The temperature of the medium surrounding a collection of nanoparticles was determined by monitoring fluorescence changes in the FMA monomer resulting from the decrease in polarity of the NIPAM/NIPMAM copolymer chain with increasing temperature.