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Multifunctional nanoclusters based on Fe3O4 nanoparticles for magnetic resonance imaging (MRI) and drug delivery are reported here. At first, oleic acid (OA)-coated Fe3O4 nanoparticles were prepared. Then block copolymer Pluronic F127 or folic acid (FA) conjugated-Pluronic F127 was used to modify the hydrophobic nanoparticles to become hydrophilic Fe3O4@F127 nanoclusters via facile ultrasonic treatment. During this process, drug molecules can also be introduced into the nanoclusters and therefore the targeted drug delivery system was formed. Next, we verified the feasibility of the nanoclusters as drug delivery vehicles and magnetic contrast agents. The nanoclusters have an average size of 200 nm and remained stable in water for long periods. Folic acid-modified nanoclusters showed an enhanced intracellular uptake into HepG2 cells by using both cellular iron amount analysis and flow cytometry analysis. Besides, Fe3O4@F127@FA nanoclusters showed good compatibility in the tested concentration range and good sensitivity in T2-weighted MRI. The magnetic nanoclusters combined with drug delivery properties have greatly increased the significance in the diagnosis and therapy of diseases, which are suitable for systematical administration of hydrophobic drugs and simultaneously MRI diagnosis.

An ultra-sensitive T2-weighted MR imaging contrast agent was prepared based on Fe3O4 nanoparticles and Gd3+ ions (Fe3O4@Gd). Amino modified Fe3O4 nanoparticles were conjugated to diethylenetriamine pentaacetic acid, and finally coordinated with Gd3+ ions. The nanoparticles had a uniform morphology with a size of 100 nm and a Gd/Fe mass ratio of 1/110. The r2 (transverse relaxivity) of the Fe3O4 nanoparticles increased from 131.89 mM−1 s−1 to 202.06 mM−1 s−1 after coordination with Gd3+ ions. MR measurements showed that the aqueous dispersion of Fe3O4@Gd nanoparticles had an obvious concentration-dependent negative contrast enhancement. Hepatoma cells were selected to test the cytotoxicity and MR imaging effect. The application of Fe3O4@Gd nanoparticles as contrast agents was also exploited in vivo for T2-weighted MR imaging of rat livers. All the results showed the effectiveness of the nanoparticles in MR diagnosis.

The facile fabrication of multifunctional nanocomposites (Fe3O4/HBC@F127) consisting of superparamagnetic Fe3O4 nanoparticles and fluorescent organic hexa-peri-hexabenzocoronene (HBC) molecules incorporated in block copolymer diacylphospholipid–polyethyleneglycol F127 have been demonstrated for dual mode imaging (fluorescent/MR) and drug delivery. The obtained nanocomposites were water-dispersible, stable and biocompatible, as confirmed by dynamic light scattering (DLS) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Relativity measurements showed a T2 relaxivity (r2) of 214.61 mM−1 s−1, which may be used as T2-weighted MR imaging agents. In vitro imaging studies indicated that the nanocomposites had good MR and fluorescence imaging effects with low cytotoxicity. Besides, the developed nanocomposites could also be applied as drug delivery vehicles. Doxorubicin (DOX) loaded Fe3O4/HBC@F127 nanocomposites significantly inhibited the growth of human hepatoma cells (HepG2). These findings suggested that the facile synthesized multifunctional nanocomposites may be used as a platform for dual mode imaging (both MR and fluorescence) and drug delivery.

Micelle-to-vesicle morphological transition has been achieved by light-induced rapid hydrophilic arm detachment from a star polymer. This provides a remote and clean method to control morphology transition of polymeric assemblies.