Ultrabright adenosine monophosphate (AMP) capped gold nanoclusters (AuNCs@AMP) were used as a novel fluorescent probe to detect lactate dehydrogenase (LDH), an important biomarker of common injuries and diseases. The fluorescence emission of AuNCs@AMP is quenched linearly in the presence of a wide concentration range of LDH (50–1000 nM), covering the range for clinical diagnosis. Particularly, the detection is very sensitive with an extremely low detection limit of 0.2 nM (26 pg μL−1, 0.8 U L−1), being more sensitive than the previously reported ones. However, the proposed probe does not response to other commercially available proteins with different isoelectric points, which shows a high selectivity toward LDH. In addition, the response mechanism is also investigated in detail, where the quenching response is attributed to the binding of AuNCs to the free thiol groups at the LDH surface. Therefore, the present study supplies a cost-effective, fast and easily performed approach to detect LDH with high selectivity and sensitivity, which has potential use in clinical diagnosis in future.

Innovative nanomaterials offer significant potential for diagnosis of severe diseases of the developing world such as malaria. Small sized silver nanoclusters have shown promise for diagnostics due to their intense fluorescence emission and photo-stabilities. Here, double-stranded DNA-scaffolded silver nanoclusters (AgNCs-dsDNA) were prepared to detect the established malaria biomarker, Plasmodium falciparum lactate dehydrogenase (PfLDH). Significant luminescence enhancement over a wide concentration range of PfLDH was demonstrated. In addition, a low limit of detection at 0.20 nM (7.4 pg μL−1) was achieved for PfLDH in buffer solution, sensitive enough for practical use correlating with the clinical level of PfLDH in plasma from malaria-infected patients. Unique specificity was observed towards Plasmodium falciparum over Plasmodium vivax and human lactate dehydrogenase, as well as other non-specific proteins, by combining the use of AgNCs-dsDNA with a DNA aptamer against PfLDH. Moreover, the intrinsic mechanism was revealed in detail for the two-step luminescence response. The combination of DNA-scaffolded silver nanoclusters coupled to a selective single-stranded DNA aptamer allows for a highly specific and sensitive detection of PfLDH with significant promise for malaria diagnosis in future.

The aggregation-induced emission (AIE) phenomenon of the metal nanoclusters (NCs) has been discovered quite recently, which is considered to be creative to improve the optical properties of NCs upon ligand aggregation. In the present study, we report an AIE system for double-stranded DNA-templated silver nanoclusters (AgNCs-dsDNA) by using bovine serum albumin (BSA) in solution, which induce a moderate emission enhancement of AgNCs (5-fold) and a blue-shift through a loosen interaction. In addition, significant luminescence enhancement (30-fold) is further stimulated by the addition of digestive enzyme to the system by altering the surface structure of the aggregated particles. The processes are observed directly through transmission electron microscopy (TEM), where the dispersed AgNCs spheres are aggregated in a large incompact sheet-like film by BSA; while further trypsin addition lead them into larger particles (>50 nm) with higher density. And the intrinsic mechanism is explained well by UV–vis absorption and time-resolved luminescence spectra. The observed luminescence enhancement in step-II is attributed to the AIE through stronger interaction between the hydrolysates of BSA and the ligand dsDNA. Therefore, the optical properties of AgNCs-dsDNA are regulated well by the addition of BSA and trypsin in different amounts, which relates directly to the degree of aggregation and can be extended to other metal nanoclusters by employing the pairs of protein and related enzyme.An aggregation-induced emission (AIE) system has been constructed by using double-stranded DNA-templated silver nanoclusters (AgNCs-dsDNA), BSA and trypsin, which induced the emission of AgNCs enhanced significantly in two steps with different aggregation patterns.Download high-res image (204KB)Download full-size image

Functional DNA cannot pass through plasma membrane of living cells by itself. An efficient non-viral DNA carrier with low cytotoxicity and simple preparation procedure is in high demand. Herein, we describe that protein–gold hybrid nanocubes (PGHNs) could intrinsically recognize DNAs, and transform them into nanoflower-like structures. These supramolecular complexes can be internalized by living yeast cells and allow the coding information of the gene to be transmitted into proteins. PGHN–DNA can be a good model to study DNA–carrier interactions as well as a new carrier for gene delivery research.

Herein, a rapid and effective hydrothermal synthesis method was employed for the preparation of Au and Ag bimetallic nanoclusters protected by adenosine monophosphate (Au–AgNCs@AMP); the Au–AgNCs@AMP show large Stokes shift (∼200 nm) and strong luminescence emission with a high quantum yield (QY = 8.46%). Moreover, to the best of our knowledge, it is for the first time that the hydrothermal synthesis method has been employed to prepare bimetal nanoclusters protected by small molecules, which is a simple, easy-to-operate, one-pot, and time saving method. Through employing gold nanoclusters as seed and monitoring the preparation process, it can be understood that Au–AgNCs@AMP are formed with a core–shell structure, where gold atoms serve as the core and silver atoms are distributed on the surface as a shell. In addition, the Au–AgNCs@AMP show an obvious color change and turned from colorless to orange accompanied by a slight luminescence quenching upon exposure to sunlight; moreover, a new absorption peak appears between 400 and 500 nm, which gradually increases with the exposure time, and the mean particle size of the products also increases from 2.25 to 10.0 nm. The intrinsic mechanism of the novel photosensitivity has been attributed to the hydroxyl groups on the sugar ring of AMP that react with silver ions on the surface of the bimetal nanoclusters and induce an increase in the particle size. Herein, we have presented a new and feasible synthesis method for small molecule-protected bimetal nanoclusters to improve their luminescence properties.

Polyoxometalates (POMs) represent a type of typical polyanionic nanoclusters that can be utilized as inorganic bioactive materials; however, the detailed interactions of them with many target biomolecules such as peptides and proteins were not well clarified due to the complexity of the binding process. In the present study, the binding-induced physiochemical phenomena of a highly charged Eu-containing polyoxometalate, K13[Eu(SiW9Mo2O39)2] (EuSiWMo), with a model protein, bovine serum albumin (BSA), was identified upon the examination of luminescence of both the components during the titration. The large emission enhancement and subsequent quenching of the EuSiWMo were found in close relation to the amount of added BSA. Being different from the known binding type of less charged POMs, a distinct two-step binding process was concluded, and the possible mechanism was proposed through the analysis on the time-resolved fluorescence spectra, isothermal titration calorimetry (ITC), transmission electron microscope (TEM), and two-dimensional correlation spectroscopy (2D COS). The present results directed a new understanding for the charge numbers and existing state of POMs affecting the interaction with proteins, which is important to exploit the biological functionalities of POMs in related systems and the development of POMs as potential inorganic drugs.

•This paper provides the first hydrothermal synthesis of platinum nanoclusters.•The prepared polyethylenimine-protected platinum nanoclusters possess high quantum yield of 28%.•A new method to detect trace amount of metronidazole in urine is proposed.A novel one-step hydrothermal synthesis of highly fluorescent platinum nanoclusters protected by polyethylenimine (Pt-NCs@PEI) is described. The products are characterized well by UV–vis absorption, fluorescence spectra, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) imaging. The Pt-NCs@PEI possess high quantum yield at 28%, which is the relatively high one among the reported Pt-NCs; especially, the synthesis is in one-step and the reaction time is much shorter (<1 h) than the related methods. In addition, the Pt-NCs@PEI have large Stocks-shift (∼150 nm), high tolerability to the extreme pH and high ionic strengths, and excellent photo-stability under UV–vis irradiation, lay the foundation for the practical bio-applications. Finally, the obtained Pt-NCs@PEI are used to determine trace amount of metronidazole (MTZ) in buffer solution in showing a linear response over a concentration range of 0.25–300 μM and a low detection limit of 0.1 μM. Furthermore, the related investigation on response mechanism will be helpful to design and synthesize new metal nanoclusters as fluorescent probe to detect the trace amount of harmful medicine residuum as nitroimidazoles in human body.