Preparation of a magnetofluorescent nano-thermometer and its targeted temperature sensing applications in living cells.

A magnetic fluorescent nano-thermometer is presented. To fabricate the nano-thermometer, magnetic nanoparticles (Fe3O4) were first encapsulated with a silica layer. Then a poly (N-isopropylacrylamide) (pNIPAM) copolymer shell with Rhodamine B isothiocyanate (RhBITC) embedded inside was further coated, which was denoted as the pNIPAM-co-RhBITC shell. Finally, gold nanoparticles were introduced onto the copolymer shell by in-situ growth method and the nano-thermometer (denoted as Fe3O4@SiO2@(pNIPAM-co-RhBITC)/Au) was obtained. The nano-thermometer shows dual responses to both magnetism and temperature. Specifically, the fluorescence intensity of the nano-thermometer decreases as the temperature increases, which makes the nano-thermometer suitable for intracellular temperature sensing. Using this nano-thermometer, temperature changes in live HeLa cells can be successfully detected. Moreover, due to the Fe3O4 component, magnetic field guided targeting can be realized, thus targeted temperature sensing can be achieved for living cells. Cellular temperature changes can be easily detected using the proposed nano-thermometer in the range of 26°C to 41°C with a sensitivity of -4.84%°C(-1).