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Carbon dots have promising prospects for analytical and monitoring purposes, but are greatly hindered by the aggregation-induced luminescence quenching owing to the π–π interaction or the non-radiation-excited radical complex formation. Herein hydrothermally prepared orange-yellow fluorescent carbon dots (O-CDs) show an aggregation-induced fluorescence enhancement (AIFE) with Cu2+ owing to the complexation of Cu(II) and the O-CDs. Cu2+ was then sensitively and selectively detected in the linear range from 0.02 to 30 μM with the detection limit of 14 nM, making the detection of Cu2+ in fresh water and E. coli lysate successful, showing that the as-prepared O-CDs could be well applied to the environmental monitoring of heavy metals. [ABSTRACT FROM AUTHOR]

Qualitative and quantitative determination of lysozyme concentrations in urine and serum with high selectivity and sensitivity is important for diagnosing the progression of several diseases. In this report, we devised an improved method for specifically detecting lysozyme by combining magnetic nanoparticles (for separation and enrichment), an aptamer (for selective binding of lysozyme) and strongly scattering silver nanoparticles (AgNPs, for detection by light scattering, but also providing another level of selectivity due to their electrostatic binding with lysozyme). In this system, 0.4–30 nM lysozyme could be simply detected owing to the decreased light scattering of AgNPs in solution after magnetic separation, with a detection limit of 100 pM. In addition, lysozyme was also able to be semi-quantified by using the dark-field light scattering images of AgNPs after enrichment by the MNP–apt–lysozyme complex. Moreover, this design shows great promise for the robust and reliable detection of lysozyme in real samples, with a recovery rate ranging from 98.6% to 101.3% in human serum samples. Therefore, this assay provided robust measurements with good specificity, sensitivity, and tolerance of changes in the sample matrix. We expect that this MNP-based aptasensor may find utility in the accurate diagnosis of lysozyme-related diseases. [ABSTRACT FROM AUTHOR]

A one-step synthesis of water soluble and pH-responsive trypsin-stabilized fluorescent copper nanoclusters (CuNCs) was reported without using additional protective or reducing agents, and the as-prepared CuNCs exhibited highly stable properties including oxidation resistance, thermal stability and photostability. [ABSTRACT FROM AUTHOR]

A new spectrofluorometric method for cellular prion protein (PrPC) was developed based on the regulation of N,N′-bis[3,3′-(dimethylamino)propylamine]-3,4,9,10-perylenetetracarboxylic diimide (DAPER) fluorescence. As a perylene derivative, DAPER emits strong fluorescence in the form of free monomer in aqueous medium, but not in the form of aggregates. In this contribution, we found that the aptamer of PrPC could induce the aggregation of DAPER, and the bright fluorescence of DAPER was completely quenched. The quenched fluorescence, however, was recovered if PrPC was further added, which was ascribed to the specific binding of PrPC to its aptamer and the releasing of free DAPER monomers. This signalling mechanism makes it possible to detect PrPC by fluorescence spectroscopy. The assay allows the selective determination of PrPC in aqueous solution with high sensitivity and exhibits a good linear range from 0.4 to 1.6 nmol L−1. Moreover, this probe can be applied to monitor the level of PrPC in human urine samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The very simple and general spectrofluorometry of cellular prion protein (PrP(C)) is reported in this contribution based on the on-off noncovalent interaction of fluorescent dye-labelled PrP(C) DNA aptamers with multi-walled carbon nanotubes (MWCNTs). Due to the π-π stacking interaction between the DNA bases of the aptamer and the carbon nanotubes, the fluorescent dye and the MWCNTs are brought into close proximity, which leads to fluorescence quenching with a ratio of up to 87%. However, further addition of PrP(C), which disturbs the π-π interaction owing to the strong and specific binding of the aptamer to PrP(C), driving the aptamer away from the surface of the MWCNTs, restored the quenched fluorescence. This recovered fluorescence intensity was found to be in linear proportion to the PrP(C) concentration in the range of 8.2 to 81.7 nM, which builds the basis of the spectrofluorometry of the cellular prion protein.