Synergetic Enhancement of Fluorescence and Magnetic Resonance Signals Assisted by Albumin Cage

Bimodal fluorescence and magnetic resonance imaging (FLI/MRI) is important for early diagnosis of malignant tumors. Yet, facile and opportune strategies to synergistically enhance fluorescence intensity and magnetic resonance (MR) contrast effect have been rarely reported. Here, a facile albumin cage (AC) strategy is provided to synergistically enhance the fluorescence intensity by aggregation-induced emission (AIE) and MR contrast with prolonged rotational correlation time (τR) of Gd(III) chelates and diffusion correlation time (τD) of surrounding water molecules. The amphiphilic bimodal FLI/MRI probe of NGd, could be facilely loaded into ACs to generate supramolecular structure of NGd-albumin cages (NGd-ACs), which show excellent biocompatibility and biosafety, and exhibit superior fluorescence quantum yield and r1 over NGd with 6- and 8-fold enhancement, respectively. Moreover, compared with clinical MRI contrast agent of Gd-DOTA, r1 of NGd-AC shows 17-fold enhancement. As a result, NGd-ACs successfully elicit high-performance bimodal FLI/MRI in vitro and brighter MR signals are observed in liver and tumor after intravenous injection of NGd-ACs with a dosage of 6 μmol Gd(III)/kg body weight. This strategy is generic and feasible, and successfully realizes a “1+1>2” effect for dual-modal FLI/MRI.