Lipid-Encapsulated Fe₃O₄ Nanoparticles for Multimodal Magnetic Resonance/Fluorescence Imaging

Magnetic resonance imaging (MRI) and fluorescence imaging (FI) are widely used in disease detection, diagnosis, and image-guided therapy. Dual-modality MRI/FI probes can provide a unified imaging platform for examining diseases at different spatial scales and resolutions. Here, we show that a library of MRI/FI nanoprobes can be generated through three orthogonal assembly processes: encapsulation of magnetic nanoparticles (MNP) in phospholipids and phospholipid-PEG copolymers, physical adsorption of dialkylcarbocyanine dyes, and surface bioconjugation of targeting ligands. The three molecular assembly processes can be independently optimized, facilitating the fine-tuning of individual components of the nanoprobes. In particular, the DiI/DiR/MNP nanoprobes provide stable and high signal contrast in MRI full body scan, in vivo/ex vivo near-infrared fluorescence imaging, and fluorescence microscopy, demonstrating the potential applications of the nanoprobes in coherent tumor diagnostic imaging, intraoperative imaging, and tumor biopsy. Our approach provides a general lipid-based nanofabrication strategy for the rational design of multimodal imaging probes.