Controlled aggregation of amphiphilic aggregation-induced emission polycation and superparamagnetic iron oxide nanoparticles as fluorescence/magnetic resonance imaging probes

Fluorescence/magnetic resonance (MR) dual-mode imaging, which combines the excellent single-cell sensitivity of fluorescence imaging and the high spatial resolution of MR imaging, has been applied to different biomedical applications. However, the aggregation-caused quenching characteristic of most fluorescence molecules often put limits in their applications. Herein, a fluorescence/MR dual-mode imaging probe [polyethylene glycol-polyethylenimine-tetraphenylethene (PEG-PEI-TPE)/superparamagnetic iron oxide (SPIO)] with aggregation-induced emission characteristic is prepared by coupling poly(acrylic acid)-coated SPIO with PEG-PEI-TPE. The fluorescence intensity and lifetime of PEG-PEI-TPE/SPIO is higher than PEG-PEI-TPE especially at lower polymer concentrations (≤0.2 mg mL −1 ). Moreover, the fluorescence intensity of PEG-PEI-TPE/SPIO gradually increased along with the decline of the pH from 9.0 to 4.0, which is beneficial for studying intracellular organelles. The T 2 relaxivity of PEG-PEI-TPE/SPIO is 212.3 Fe m M −1 s −1 under a 3.0 T MR scanner. Cell labeling experiment shows that PEG-PEI-TPE/SPIO can effectively label RAW 264.7 and Hela cells, and labeled cells are visible under both fluorescence and clinical MR examinations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48760.