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This report outlines a highly sensitive and facile electrochemiluminescence (ECL) sensing platform based on a novel high-quantum-yield Au-nanocluster (AuNC) probe for glutathione (GSH) detection. Owing to the prominent quenching effect of GSH on the ECL of the AuNCs, the proposed ECL nanosensor showed a wide response to GSH in the ranges of 1.0 × 10 -9 –1.0 × 10 -5 M and 1.0 × 10 -5 –1.0 × 10 -1 M and a low detection limit of 3.2 × 10 -10 M. In addition, the proposed system exhibited good selectivity for GSH in the presence of other chemical/biological interferences. Moreover, since no further functionalization of AuNC-based sensor interface was necessary, together with the stability, high sensitivity and selectivity of the proposed nanosensor, this convenient approach was able to successfully detect GSH in both of human urine samples and blood samples with excellent recoveries, which indicated its promising application under physiological conditions. Of significant importance is that this study not only helps in gaining a better understanding of the applicability of the ECL properties of AuNCs, but also provides a new avenue for the design and development of ECL sensors based on the novel high-quantum-yield AuNC-based probe and other functional-metal-based NC probes. [ABSTRACT FROM AUTHOR]

Herein, we reported for the first time a facile synthetic process of gold nanoclusters (AuNCs) by using N-acetyl-l-cysteine both as a reducing agent and as a protection ligand. Based on the pH stimuli-responsive properties of the as-prepared AuNCs, we constructed a pH-sensing platform for the detection of urea, urease, and urease inhibitors. [ABSTRACT FROM AUTHOR]

Highlights: [•] The multi-functional Au–PDA–THi–GO NCs were prepared by in situ chemical polymerization. [•] The bioinspired surface was further used for label-free electrochemical immunosensor. [•] The Au–PDA–THi–GO NCs prevented the leakage of mediator and afforded high biomolecular loadings. [•] This method is highly recommended as a new biosensing platform for biomolecule immobilization. [ABSTRACT FROM AUTHOR]

Water-soluble and non-aggregating gold nanoclusters (AuNCs) were obtained by modification of the AuNCs with dithiothreitol (DTT) and then coating them with carboxylated chitosan. This process remarkably enhances the dispersibility of DTT-coated AuNCs in water. The resulting AuNCs, on photoexcitation at 285 nm, display strong red emission with a maximum at 650 nm and a 23% quantum yield. Fluorescence is strongly and selectively suppressed in the presence of 6-mercaptopurine (6-MP). Photoluminescence drops linearly in the 0.1-100 μM 6-MP concentration range, and the detection limit of this assay is 0.1 μM. Other features of the modified AuNCs include a decay time of 8.56 μs, a 365 nm Stokes shift, good colloidal stability, ease of chemical modification, and low toxicity. Conceivably, these NCs may find a range of applications in biological imaging and optical sensing.Highly fluorescent and water-soluble gold nanoclusters (AuNCs) were obtained by modification of the AuNCs with dithiothreitol (DTT) and then coating them with carboxylated chitosan (CC). The resulting CC/DTT-AuNCs were used for sensitive and selective detection of 6-mercaptopurine. [ABSTRACT FROM AUTHOR]

This paper reports a new and facile method for the synthesis of water-soluble thiolate-protected AuNCs via protein-ligand interaction. Using 3-mercaptopropionic acid (MPA) as a model ligand and bovine serum albumin (BSA) as a model protein, water-soluble AuNCs (BSA/MPA-AuNCs) with intense orange-yellow fluorescent emission (quantum yield=16%) are obtained. Results show that AuNCs produced with this method have hydrophobic interactions with BSA. The synthetic strategy is then successfully extended to produce water-soluble AuNCs protected by other thiolates. Moreover, a sensitive and eco-friendly sensing system is established for detection of the activity of inorganic pyrophosphatase (PPase), which relies on the selective coordination of Fe 3+ with BSA/MPA-AuNCs, the higher affinity between pyrophosphate (PPi) and Fe 3+ , and the hydrolysis of PPi by PPase. A good linearity between the fluorescence intensity and PPase activity within the range from 0.1 to 3 U/L is found, with a detection limit down to 0.07 U/L. Additionally, the fluorescent assay developed here is utilized to assay the PPase activity in real biological samples and as well as to evaluate PPase inhibitor, illustrating the great potential for biological analysis. [ABSTRACT FROM AUTHOR]

A novel myoglobin–gold nanoparticles–polydopamine–graphene (MGPG) polymeric bionanocomposite was applied for studying the immobilization and direct electrochemistry of redox protein. The MGPG bionanocomposite was synthesized by an efficient one-pot green polymerization approach. The direct electrochemistry studies of the MGPG bionanocomposite modified electrode demonstrated that the immobilized myoglobin (Mb) retained its bioactivity and exhibited strongly enhanced direct electrochemical redox activity. This is mainly attributed to the proper orientation of the immobilized Mb due to in-situ oxidative polymerization process, the large specific surface area of the nanocomposite, and the good conductivity of the graphene-Au nanoparticles complex. Hence, the present polymeric bionanocomposite displayed good electrocatalytic activity to the reduction of H 2 O 2 . The proposed method is highly recommended as a novel biosensing platform for biomolecules immobilization, which can further expand the applications of biosensing and biocatalysis, such as construction of third-generation biosensors and the detection of H 2 O 2 released by cells. [ABSTRACT FROM AUTHOR]

• Cyst-GNPs are used as colorimetric probes for the detection of Sc3+. • PLP is adopted as an effective aggregation promoter of Cyst-GNPs. • Sc3+ ions effectively compete with Cyst-GNPs to bind PLP. • Negligible interfere from other ions is observed in this assay. The design and development of colorimetric sensors for recognition of rare-earth Sc3+ ions are very challenging and most of the reported methods are limited by poor sensitivity and serious interference. Herein, we unveiled a new colorimetric strategy for the sensitive and selective detection of Sc3+ based on the surface plasmon resonance properties of gold nanoparticles (GNPs). The key aspect of the proposed protocol is the selection of pyridoxal phosphate (PLP), an important biomolecule involved in many biological processes, both as an effective aggregation promoter of GNPs stabilized by cysteamine (Cyst-GNPs) and a strong chelator for the selective complexation of Sc3+. PLP can covalently bind to the Cyst-GNPs through the formation of a Schiff base, which neutralizes the positive surface charges, weakens the electrostatic repulsion force among the nanoparticles, thereby triggering the agglomeration of Cyst-GNPs. Owing to the intensive Lewis acid-base interactions, the introduced Sc3+ ions effectively compete with Cyst-GNPs to bind PLP, and the Cyst-GNPs tend to be dispersed in this case. A linear response from 0.1 to 3 μM is achieved for Sc3+, and a detection limit down to 0.02 μM is obtained. Negligible interfere from other ions is observed in this assay under identical experimental conditions. [ABSTRACT FROM AUTHOR]

• CC/DTT-AuNCs are used as fluorescent probes for the detection of DOX. • PET is identified to play a dominant role for the PL quenching mechanism. • Other anthraquinone structures devoid of –NH 2 groups exhibit no quenching effect. • This method is used to successfully measure DOX in human serum samples. Doxorubicin (DOX), an anthraquinone-based anticancer drug, is effective for the treatment of a variety of human tumors. However, due to its narrow therapeutic window, serum levels need to be closely monitored. Herein, we report the development of a novel fluorescence probe based on gold nanoclusters co-modified with dithiothreitol (DTT) and carboxylated chitosan (CC) (CC/DTT-AuNCs) for the determination of DOX. The emission from the CC/DTT-AuNCs is significantly suppressed by DOX. The fluorescence-quenching mechanism involving DOX was systematically explored, and photoinduced electron transfer was identified to play a dominant role. DOX readily binds to the CC/DTT-AuNC surface through electrostatic attraction, after which it accepts the electron from the photoexcited CC/DTT-AuNC and quenches its fluorescence. We found that other anthraquinone structures (e.g., alizarin and emodin) devoid of –NH 2 groups exhibited almost no CC/DTT-AuNCs fluorescence-quenching effect due to weak electrostatic interactions between these anthraquinones and the NCs. A linear relationship between photoluminescence suppression and the concentration of DOX was observed in the 0.05–2 μM range under the optimal experimental conditions, with a detection limit as low as 5 nM. This new sensing approach was also used to successfully measure DOX in human serum samples with satisfactory results obtained. [ABSTRACT FROM AUTHOR]