Quanyuan Zhang

Self-assembled magnetic luminescent hybrid micelles containing rare earth Eu for dual-modality MR and optical imaging

In this study, we report new water-soluble multifunctional nanomaterials based on amphiphilic poly(HFMA-co-Eu(AA)3Phen)-g-PEG copolymers and oleic acid modified Fe3O4 nanoparticles. The nanoparticles can self-assemble to form magnetic and luminescent hybrid micelles and show a spherical morphology, paramagnetic properties with a maximum saturation magnetization of 7.05 emu g-1, and a high transverse relaxivity of 340 mM-1 s-1. According to in vivo magnetic resonance imaging (MRI) experiments, excellent contrast of the liver and spleen was achieved after injection of the hybrid micelles. Fluorescence spectra show characteristic emission peaks from the rare earth Eu at 616 nm and vivid red fluorescence can be observed by 2-photon confocal laser scanning microscopy (CLSM). In vivo optical imaging demonstrates the unique fluorescent characteristics of the magnetic and luminescent hybrid micelles in the liver and spleen and the excellent multifunctional properties suggest the possibility of clinical use as nanocarriers in magnetic resonance imaging and optical imaging.

Emulsifier-free emulsion polymerized poly(MMA-HEMA-Eu(AA)3Phen)/Fe3O4 magnetic fluorescent bifunctional nanospheres for magnetic resonance and optical imaging

Integration of biocompatibility with superparamagnetic Fe3O4 nanoparticles and luminescence rare earth complexes Eu(AA)3Phen was carried out to form bifunctional nanospheres for using in bioimaging applications. The nanospheres Poly(MMA-HEMA-Eu(AA)3Phen)/Fe3O4 exhibit magnetic and fluorescent properties that are favorable for the use in drug delivery, magnetic separation and MR imaging for biomedical research. The TEM and SEM studies reveal that the bifunctional nanospheres have core-shell structure, in a spherical shape with a size ranging from 140 nm to 180 nm. In MRI experiments, a clear negative contrast enhancement in T2 images and the r2 reaches 568.82 (mmol·L-1)-1·s-1. In vivo magnetic and fluorescence resonance imaging results suggest the nanospheres are able to preferentially accumulate in liver and spleen tissues to allow dual-modal detection of cancer cells in a living body.

In situ solution polymerization for preparation of MDI-modified graphene/hyperbranched poly(ether imide) nanocomposites and their properties

Firstly, fully exfoliated graphene oxide (GO) colloidal dispersion in N-methyl-2-pyrrolidone (NMP) with high concentration is obtained by a solvent-exchange method and further used to prepare superior GO-MDI with free isocyanato groups by chemical modification. Then, the yielded GO-MDI is employed to prepare two kinds of MDI-modified graphene/hyperbranched poly(ether imide) (GE-MDI/HBPEI) nanocomposites via in situ random solution co-polycondensation or crosslinking reaction, followed by synchronous thermal imidization and reduction. The chemical modification of GO endows GO-MDI with good solubility in organic solvents to prepare GE-MDI/HBPEI nanocomposites with high filler content. GO-MDI is further used as a multi-functional co-monomer or crosslinker to be introduced into the HBPEI backbone with full compatibility of the guest and host at the molecular level. Finally, the performance tests show that the heat resistance, thermal stability, mechanical strength and modulus, and gas barrier properties of the obtained two kinds of nanocomposites are significantly improved or enhanced compared with pure HBPEI, and the impacts become more and more significant with the increase of GO-MDI content, but their mechanical toughness show trends of increase at first then decrease with the increase of GO-MDI content. Comparisons also show that at the same GO-MDI content, the heat resistance, thermal stability, mechanical strength and modulus of the nanocomposites obtained by in situ random solution co-polycondensation are all superior to those obtained by in situ random solution crosslinking reaction, except the mechanical toughness and gas barrier properties of the former are less than the latter. This effective approach provides a possibility for enriching and developing high performance PEI-based composites with various forms of GE for advanced engineering or functional materials.

Magnetic, fluorescent, and thermo-responsive poly(MMA-NIPAM-Tb(AA)3Phen)/Fe3O4 multifunctional nanospheres prepared by emulsifier-free emulsion polymerization

Magnetic, luminescent, and thermoresponsive multifunctional nanospheres composed of modified Fe3O4 nanoparticles as the core and rare earth complex Tb(AA)3Phen as the shell are synthesized by emulsifier-free emulsion polymerization. The core–shell spherical structure has a size between 140 and 220 nm and exhibits strong green fluorescence of the rare earth complex Tb(AA)3Phen. In the R2 relaxivity and in vivo MRI studies, the R2 relaxivity of the nanospheres is 562.56 mM–1 s–1 and enhanced T2-weighted images are observed from the nanospheres in the liver and spleen after injection as a contrast agent. The excellent superparamagnetic, thermosensitive, and fluorescent properties render the nanospheres useful in biomedical engineering and optical imaging.

Supermolecular theranostic capsules for pH-sensitive magnetic resonance imaging and multi-responsive drug delivery

Magnetite (Fe3O4) microcapsules prepared by layer-by-layer self-assembly are investigated as multi-functional magnetic resonance imaging contrast agents and drug carriers. They are produced by host-guest interactions and Coulombic force from different supramolecular polymers. Drug molecules are released controllably from the microcapsules by non-invasive ultra-violet light induced photo-isomerization of the azobenzene molecule and pH sensitive Schiffs base. In addition, by encapsulation of the superparamagnetic iron oxide nanoparticles (SPION) in the nearby layers, magnetic field targeting and MRI contrast are achieved. Under tumor-like acidic conditions (pH = 5.6), the r2 relaxivity of the microcapsules is 126 mM-1 s-1 which is 37% higher than that in a neutral environment (92 mM-1 s-1). As a result of the low pH enhanced MRI contrast agent, the tumor structure can be observed clearly in vivo confirming the high efficacy as a negative MRI agent in T2-weighted imaging. The materials as combined carriers have great potential in clinical applications as drug delivery agents and contrast agents in MRI.