Search

To regulate nanostructure synthesis is of crucial importance for developing various applications, including catalysis, bioanalysis, and optical devices. Herein, the morphology and peroxidase (POD)-mimicking activity of peptide-templated copper nanoassemblies (Cu NAs) are regulable with peptide types. The Cu NAs templated with peptide containing single cysteine are uniform nanoclusters with strong POD-like activity. However, the Cu NAs templated with peptide containing two cysteines are fusiform-like with very weak POD-like activity. Unexpectedly, the POD-like activity of Cu NAs templated with peptide containing two cysteines with lysine between the cysteines is significantly enhanced when trypsin is incubated, which is unchanged for the Cu NAs templated with peptide containing two cysteines without lysine between the cysteines. The remarkably enhanced POD-mimicking activity originates from trypsin specifically shearing the peptide bond on the lysine, thereby allowing the aggregated Cu NAs to unravel into individual nanoclusters. Therefore, a robust colorimetric sensing platform was constructed for sensitive and selective detection of trypsin, which showed a linear concentration range of 3-1000 nM and a detection limit of 0.82 nM (S/N = 3). More interestingly, featured by trypsin inhibitor restraining trypsin activity, it enabled us to screen trypsin inhibitors as well. Subsequently, the developed assay was applied to detect trypsin in serum samples with good accuracy and reproducibility. Thus, this strategy shows great potential application in the clinic for diagnosis of trypsin-indicating diseases as well as the screening of trypsin inhibitor-based anti-cancer drugs.

A simple colorimetric sensing strategy for Hg 2+ ions was developed using silver/copper nanoclusters (Ag/Cu NCs) with excellent selectivity and sensitivity. Bimetallic Ag/Cu NCs were synthesized by using glutathione (GSH) as a template and sodium borohydride as a reducing agent. It was found that the peroxidase-like activity of Ag/Cu NCs was significantly enhanced in the presence of Hg 2+ . Therefore, a colorimetric method based on catalysis was developed to detect Hg 2+ with a linear concentration range of 0.1-700 nM and a detection limit of 0.05 nM (S/N = 3). The common species have no effect on Hg 2+ ion detection. Furthermore, this method is applicable to accurately detect Hg 2+ in real aqueous samples and is reproducible. Therefore, owing to the merits of sensitivity, selectivity, rapid response and visual read-out, it can be promising in the development of a portable Hg 2+ analyzer for on-site detection.

Gold nanoplates (AuNPTs) exhibit outstanding photothermal conversion efficiency (68.5%) and peroxidase-like activity. The combination of the very low H2O2 concentration (0.1 mM) and the low AuNPT dosage (50 μg mL-1) with 808 nm laser irradiation (1 W cm-2, 3 min) shows excellent synergistic antibacterial ability and healing of MRSA-infected wounds in vivo.

A fluorimetric analytical method using test strips has been fabricated for detecting Hg 2+ ions in blood by using copper nanoclusters (Cu NCs) prepared via a biomineralization route. Unexpectedly, the as-prepared Cu NCs displayed greatly amplified red fluorescence once dispersed in DMSO, the intensity of which decreased specifically in the presence of Hg 2+ . Moreover, the resultant Cu NCs were deposited onto test strips to be further fast dried on superhydrophobic substrates in vacuum. The test strip-based fluorimetry can allow for the direct analysis of Hg 2+ in blood in the linear concentration range of 0.10-1000 nM. Importantly, this solvent-enhanced fluorescence protocol for different metal probes such as Cu NCs promises extensive analysis applications for designing numerous fluorimetric platforms such as test strips.

Nanozymes are artificial enzymes, which can substitute traditional biological enzymes for multifield applications. However, to date, it remains challenging to search novel mimic enzymes or multienzyme mimics. Herein, a facile and green method for preparing monodisperse, homogeneous copper nanoclusters (Cu NCs) with smaller size was developed, which used cysteamine as a template and hydrazine hydrate as a reductant to reduce Cu 2+ . The as-prepared Cu NCs exhibited excellent tetraenzyme-like activities, including peroxidase (POD)-, catalase (CAT)-, superoxide dismutase (SOD)-, and ascorbic acid oxidase (AAO)-mimic activities. The mechanisms, kinetics, and catalytic performances of Cu NCs were systematically studied. Moreover, based on the POD-like activity of Cu NCs, sensitive and simple colorimetric sensing glutathione (GSH) was explored, with the low limit of detection of 0.89 μM GSH ( S / N = 3). Additionally, a novel fluorimetric ascorbic acid (AA) sensor was developed with the linear range of 0.5-30 μM and limit of detection (LOD) of 0.144 μM, on the basis of the principle that AA is oxidized to dehydroascorbic acid (DHAA) specifically catalyzed by the AAO-like activity of Cu NCs, while DHAA can further react with o -phenylenediamine (OPDA) to generate a highly fluorescent quinoxaline (DFQ) derivative. The as-proposed colorimetric GSH sensor and the fluorimetric AA sensor were capable of detecting GSH and AA, respectively, in real samples accurately and reproducibly. Thus, the Cu NCs-based multienzyme mimic is a promising candidate for biocatalysis and biosensing.

Silver nanoclusters (AgNCs) were first coated with bovine serum albumin (BSA) and then encapsulated into porous metal-organic frameworks of ZIF-8 by the protein-mediated biomineralization process. Unexpectedly, the fluorescence intensities of the yielded AgNCs-BSA@ZIF-8 nanocomposites were discovered to be continuously enhanced during each of the BSA coating and ZIF-8 encapsulation steps. Compared to common AgNCs, greatly improved photostability and storage stability of AgNCs could also be expected. More importantly, having benefited from the ZIF-8 shells, the prepared nanocomposites could possess the specific accumulation and sensitive response to Cu 2+ ions, resulting in the rational quenching of their fluorescence intensities. Moreover, AgNCs-BSA@ZIF-8 nanocomposites were coated onto the hydrophobic arraying slides toward a microdots array-based fluorimetric method for the fast and sensitive evaluation of Cu 2+ ions. It was discovered that the developed fluorimetric strategy could ensure the high-throughput analysis of Cu 2+ ions in wide pH range, and especially some harsh and high-salt media. It can allow for the detection of Cu 2+ ions in blood with the concentrations ranging from 4.0 × 10 -4 to 160 μM, thus serving as a new copper detection candidate to be widely applied in clinical test, food safety, and environmental monitoring fields.

Alcohol solvents especially isopropanol were demonstrated for the first time to endow silver nanoclusters (AgNCs) in water with dramatically enhanced red fluorescence. More importantly, the specific iodide recognition capability of the AgNCs could thus be obtained towards a highly selective fluorimetric assay for detecting iodide ions in urine.