Controlled synthesis of monodisperse iron oxide (IO) nanostructures with diverse morphology remains a major challenge. In this work, IO nanostructures with various shapes and surface structures were synthesized by thermal decomposition of iron oleate (FeOL) in the presence of sodium oleate (NaOL). In a mild condition using 1octadecene (ODE) as solvent, NaOL may preferentially bind to Fe 3 O 4 {111} facets and lead to the formation of Fe 3 O 4 {111} facet exposed IO plates, truncated octahedrons, and tetrahedrons. While in a high-boiling temperature tri-noctylamine (TOA) solvent, we obtained Fe 3 O 4 {100} facet exposed IO cubes, concaves, multibranches, and assembled structures by varying the molar ratios of NaOL/FeOL. Moreover, we demonstrated that IO nanoparticles (NPs) with metalexposed surface structures have enhanced T 1 relaxation time shortening effects to protons, and IO NPs with anisotropic shapes are superior in protons T 2 relaxation shortening due to the larger effective radii compared to that of spherical IO NPs. This study can provide rational design considerations for the syntheses and applications of IO nanostructures for a broad community of material research fields.

Magnetic resonance angiography using gadolinium-based molecular contrast agents suffers from short diagnostic window, relatively low resolution and risk of toxicity. Taking into account the chemical exchange between metal centers and surrounding protons, magnetic nanoparticles with suitable surface and interfacial features may serve as alternative T1 contrast agents. Herein, we report the engineering on surface structure of iron oxide nanoplates to boost T1 contrast ability through synergistic effects between exposed metal-rich Fe3O4(100) facets and embedded Gd2O3 clusters. The nanoplates show prominent T1 contrast in a wide range of magnetic fields with an ultrahigh r1 value up to 61.5 mM(-1) s(-1). Moreover, engineering on nanobio interface through zwitterionic molecules adjusts the in vivo behaviors of nanoplates for highly efficient magnetic resonance angiography with steady-state acquisition window, superhigh resolution in vascular details, and low toxicity. This study provides a powerful tool for sophisticated design of MRI contrast agents for diverse use in bioimaging applications.

Delivery of arsenic trioxide (ATO), a clinical anticancer drug, has drawn much attention to improve its pharmacokinetics and bioavailability for efficient cancer therapy. Real-time and in situ monitoring of ATO behaviors in vivo is highly desirable for efficient tumor treatment. Herein, we report an ATO-based multifunctional drug delivery system that efficiently delivers ATO to treat tumors and allows real-time monitoring of ATO release by activatable T1 imaging. We loaded water-insoluble manganese arsenite complexes, the ATO prodrug, into hollow silica nanoparticles to form a pH-sensitive multifunctional drug delivery system. Acidic stimuli triggered the simultaneous release of manganese ions and ATO, which dramatically increased the T1 signal (bright signal) and enabled real-time visualization and monitoring of ATO release and delivery. Moreover, this smart multifunctional drug delivery system significantly improved ATO efficacy and strongly inhibited the growth of solid tumors without adverse side effects. This strategy has great potential for real-time monitoring of theranostic drug delivery in cancer diagnosis and therapy.

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Fluorinated ion liquids (ILs) act as a new type of fluorine agents to build a fluorinated ionic liquid-based activatable 19 F MRI platform (FILAMP). Upon biological stimulation, the coating polymer dissolves or degrades to release the payload, which rapidly enhances the 19 F signals. This ''turn-on'' response is verified by successful detection of biological targets in vitro and in vivo. In summary, FILAMP can serve as a type of activatable 19 F probes for diagnosis and monitoring of biological and pathological processes.