Preparation of superparamagnetic gold nanocomposites with different diameters and their imaging and therapy applications

Superparamagnetic gold nanocomposites (SGNs), which have great potential in magnetic resonance imaging (MRI) and photothermal therapy (PT) on cancer, have been successfully synthesized via the in-situ reduction and the following seed-mediated growth route. It is found that the dimension of SGNs could be facilely tuned by changing the encapsulation amount of Fe₃O₄/tetrahydrofuran solution, and SGNs with diameters of 100, 150 and 200 nm were thus obtained. The as-synthesized SGNs present regularly spherical morphology, narrow size distributions and monodispersity in aqueous solutions. It is revealed that SGNs modified with SH-PEG are capable for simultaneous MRI and photothermal therapy. Especially, SGNs with average diameter of 150 nm exhibit the strongest absorption capacity and highest photothermal conversion efficiency with 808 nm laser. The temperatures in vitro and in vivo were increased by 37℃ and 25℃, respectively. Therefore, it is hopeful that tumor can be imaged well and killed efficiently under laser irradiation after intratumoral injection of such a kind of nanocomposites.