Fig. 4.

A safer T1 MRI contrast in a compact plasmonic nanoparticle with enhanced fluorescence was synthesized by a multilayer core-shell nanostructure, and known as nanomatryoshka (NM). Each NM consisted of an Au core, an Au shell and silica spacing layer encapsulated magnetic metal and fluorescent dye. This form protected fluorescent dye and reduced the metal release. Fe (III)-NM exhibited a 2× greater relaxivity than current MRI contrast agent (Gd-DOTA), and the photostability of fluorescent dye significantly increased (23×). Lower panel evaluated MRI and fluorescence imaging of FeCy7-NM in vivo. (A) Untreated in MRI, (B) Treated in MRI, red circle is nanoparticle and blue circle is saline, (C) Fluorescence imaging after injection. This nanoparticle can enable not only powerful tissue visualization with MRI but also fluorescence-based nanoparticle tracking. Reprinted with permission.⁶⁶ Copyright 2018. American Chemical Society.