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 mM(-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. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48760.