Synthesis of Biomimetic Melanin-Like Multifunctional Nanoparticles for pH Responsive Magnetic Resonance Imaging and Photothermal Therapy.

The design and development of multifunctional nanoparticles have attracted great interest in biomedical research. This study aims to prepare pH-responsive melanin-like nanoparticles for T1-weighted magnetic resonance imaging (MRI) and photothermal therapy. The new multifunctional nanoparticles (amino-Fe-PDANPs) are synthesized by copolymerization of dopamine and its derivative amino-N-[2-(diethylamino) ethyl]-3,4-dihydroxy-benzenepropanamide (N-Dopa) at room temperature. The size of nanoparticles can be controlled by NaOH concentration. The incorporation of N-Dopa is characterized by NMR and FT-IR. From transmission electron microscopy (TEM), the nanoparticles exhibit excellent dispersion stability in water and are spherical in shape. The MRI measurement has demonstrated that amino-Fe-PDANPs have a significant signal enhancement in responding to the acidic solution. Confirmed by the photothermal study, the nanoparticles exhibit a high photothermal conversion efficiency. The melanin-like multifunctional nanoparticles integrate both diagnosis and therapeutic functionalities, indicating the potential for theranostic application.