Multifunctional Fe3O4 @ Au core/shell nanostars: a unique platform for multimode imaging and photothermal therapy of tumors.

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 co-existence 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.