We herein report the development of multifunctional folic acid (FA)-targeted Fe3O4 @ Au nanostars
(NSs) for targeted multi-mode magnetic resonance (MR)/computed tomography (CT)/photoacoustic
(PA) imaging and photothermal therapy (PTT) of tumors. In this present work, citric acid-stabilized
Fe3O4/Ag composite nanoparticles prepared by a mild reduction route were utilized as seeds and
exposed to the Au growth solution to induce the formation of Fe3O4 @ Au core/shell NSs. Followed
by successive decoration of thiolated polyethyleneimine (PEI-SH), FA via a polyethylene glycol
spacer, and acetylation of the residual PEI amines, multifunctional Fe3O4 @ Au NSs were formed. The
designed multifunctional NSs possess excellent colloidal stability, good cytocompatibility in a given
concentration range, and specific recognition to cancer cells overexpressing FA receptors. Due to coexistence
of Fe3O4 core and star-shaped Au shell, the NSs can be used for MR and CT imaging of tumors,
respectively. Likewise, the near infrared plasmonic absorption feature also enables the NSs to be used
for PA imaging and PTT of tumors. Our study clearly demonstrates a unique theranostic nanoplatform
that can be used for high performance multi-mode imaging-guided PTT of tumors, which may be
extendable for theranostics of different diseases in translational medicine.