Magneto-fluorescent nanoparticles with high-intensity NIR emission, T₁- and T₂-weighted MR for multimodal specific...

Nanoparticles exhibiting bright near-infrared (NIR) fluorescence, T₁- and T₂-weighted MR were synthesized for specific tumor imaging. Clinically used Fe₃O₄ nanoparticles exhibit an intrinsic dark signal (T₂-weighted MRI), which sometimes misleads clinical diagnosis. Here, for the first time we integrated ultrasmall Fe₃O₄ nanoparticles (2-3 nm) with an NIR emitting semiconducting polymer for both T₁- and T₂-weighted MRI as well as fluorescence imaging of tumors. Bio-functionalized multi-modality fluorescent magnetic nanoparticles (FMNPs) functionalized with folic acid exhibit bright fluorescence and high relaxation (r₁ = 7.008 mM^-1 s^-1, r₂ = 26.788 mM^-1 s^-1, r₂/r₁ = 3.8). These FMNPs have a small average dynamic size of about 20 nm with low aggregation and long circulation time. In vitro studies revealed that FMNPs can serve as an effective fluorescent probe to achieve targeting images of human A549 lung cancer cells without obvious cytotoxicity. In vivo experimental results show that the FMNPs are able to preferentially accumulate in tumor tissues for specific fluorescence imaging, T₁- and T₂-weighted MRI.