Quasi-amorphous and Hierarchical Fe2O3 Supraparticles: Active T1-Weighted Magnetic Resonance Imaging in Vivo and Renal Clearance.

The exploration of magnetic resonance imaging (MRI) agents possessing excellent performances and high biosafety is of great importance for both fundamental science research and biomedical applications. In this study, we present that monodisperse Fe2O3 supraparticles (SPs) can act as T1-weighted MRI agents, which not only possess a distinct off-on MRI switch in the tumor microenvironment but also are readily excreted from living bodies due to its quasi-amorphous structure and hierarchical topology design. First, the Fe2O3 SPs have a surface-to-volume ratio obviously smaller than that of their building blocks by means of self-assembly processes, which, on the one hand, causes a rather low r1 relaxivity (0.19 mM-1 s-1) and, on the other hand, can effectively prevent their aggregation after intravenous injection. Second, the Fe2O3 SPs have a dramatic disassembly/degradation-induced active T1-weighted signal readout (more than 6 times the r1 value enhancement and about 20 times the r2/r1 ratio decrease) in the tumor microenvironment, resulting in a high signal-to-noise ratio for imaging performances. Therefore, they possess excellent in vivo imaging capacity, even with a tumor size as small as 5 mm3. Third, the disassembled/decomposed behaviors of the Fe2O3 SPs facilitate their timely clearance/excretion from living bodies. In particular, they exhibit distinct renal clearance behavior without any kidney damage with the right dosage. Fourth, the favorable biodegradability of the as-prepared Fe2O3 SPs can further relieve the concerns about the unclear biological effects, particularly on nanomaterials, in general.

Ratiometric sensing of metabolites using dual-emitting ZnS:Mn2+ quantum dots as sole luminophore via surface chemistry design.

We herein present an effective and versatile platform for ratiometric sensing of metabolites using intrinsically dual-emitting ZnS:Mn2+ quantum dots (QDs) as sole reporter. To avoid notoriously non-specific interactions, a special triple-layer "filter screen" around the inorganic QD core is rationally constructed, which is made of oleic acid, cetyltrimethyl ammonium bromide and bio-enzymes. In the presence of the analytes, the in-situ enzymatic H2O2 molecules diffuse and pass through the "filter screen" along the molecule interspace, which then reacts with the inorganic core and leads to more dramatically quenching of the Mn2+ emission. The ratiometric signal readout is so distinct that can be observed by naked eyes (from orange to violet). In contrast, various coexisting bio-molecules, due to larger size, are well prevented from penetrating the filter screen by steric hindrance effect. So, various potential interfering substances do not disturb the assay. Under optimal conditions, five kinds of the corresponding substrates, namely glucose, cholesterol, lactate, xanthine and uric acid are well quantified by the emission intensity ratio of I470/I615, and the linear ranges are 0.1-200µM, 0.1-200µM, 1-200µM, 1-200µM and 1-200µM, respectively. The detection limits can even reach quasi-picomole levels. Because of favorable analytical performances (excellent selectivity, appropriate sensitivity and broad linear range), the proposed system can direct assay the analytes in blood without any sample pre-treatment.

Beyond "turn-on" readout: from zero background to signal amplification by combination of magnetic separation and plasmon enhanced fluorescence.

By magnetic separation and subsequent plasmon enhanced fluorescence, an assay platform with a signal output from completely "zero" background to fluorescence amplification is achieved, using quantum dots as reporters. So, it well breaks through the conventional "turn-on" strategy in both lower and upper limits. The sensitivity for hyaluronidase sensing is enhanced 10(4)-10(6) times as compared with previous fluorescence methods.

Correction: Beyond "turn-on" readout: from zero background to signal amplification by combination of magnetic separation and plasmon enhanced fluorescence.

Correction for 'Beyond "turn-on" readout: from zero background to signal amplification by combination of magnetic separation and plasmon enhanced fluorescence' by Suqin Gong and Yunsheng Xia, Chem. Commun., 2016, 52, 9660-9663.