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Artificial micro-/nanomotors that harvest environmental energy to move require energy surroundings; thus, their motion generally occurs in fuel solutions or under the real-time stimuli of external energy sources. Herein, inspired by vehicles, a refillable fuel-loading micromotor is proposed based on a 2 μm hemispherical multimetallic shell using catalase or platinum on its concave surface as the engine and the bowl structure as the fuel tank. H

Electrocheluminescence analysis amplified by coreaction accelerators has experienced breakthrough in ultrasensitive detection of biomarkers. Herein, a highly efficient coreaction accelerator, two-dimensional layered MoSe

Simple but robust testing assays are essential for screening and diagnosis of individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in COVID-19 pandemic. Here, we described a chemiluminescent imaging assay (CLIA) for sensitive and convenient detection of SARS-CoV-2 nucleocapsid protein (NP) by a target-induced enzyme activity regulation (T-EAR) strategy. The T-EAR used a pair of antibody-DNA probes to recognize SARS-CoV-2 NP and proximity-induce rolling circle amplification for mass-production of pyrophosphate to coordinate with Cu

Sensitive detection of the SARS-CoV-2 protein remains a great research interest in clinical screening and diagnosis owing to the coronavirus epidemic. Here, an ultrasensitive chemiluminescence (CL) imaging strategy was developed through proximity hybridization to trigger the formation of a rolling circle-amplified G-quadruplex/hemin DNAzyme for the detection of the SARS-CoV-2 protein. The target protein was first recognized by a pair of DNA-antibody conjugates, Ab-1 and Ab-2, to form a proximity-ligated complex, Ab-1/SARS-CoV-2/Ab-2, which contained a DNA sequence complemental to block DNA and thus induced a strand displacement reaction to release the primer from a block/primer complex. The released primer then triggered a rolling circle amplification to form abundant DNAzyme units in the presence of hemin, which produced a strong chemiluminescent signal for the detection of the target protein by catalyzing the oxidation of luminol by hydrogen peroxide. The proposed assay showed a detectable concentration range over 5 orders of magnitude with the detection limit down to 6.46 fg/mL. The excellent selectivity, simple procedure, acceptable accuracy, and intrinsic high throughput of the imaging technique for analysis of serum samples demonstrated the potential applicability of the proposed detection method in clinical screening and diagnosis.

The mass-production capability of hybridoma technology is bottlenecked by the routine screening procedure which is time-consuming and laborious as the requirement of clonal expansion. Here, we describe a 1-day chemiluminescent screening protocol for specific hybridoma cells on conventional 96-well plate via a proximity-rolling circle activated enzymatic switch (P-RCAES) strategy. The P-RCAES uses a pair of antigen-DNA probes to recognize secreted specific antibody and proximity-induce rolling circle amplification for mass-production of pyrophosphate to activate Cu(II) inhibited horseradish peroxidase and generate a strong chemiluminescent signal. The P-RCAES based homogeneous chemiluminescent assay can detect antibody down to 18 fM, and enables the screening of specific hybridoma cells secreting PCSK9 antibody at single-cell level without tedious cloning process. The proposed fast screening protocol has good expansibility without need of sophisticated instruments, and provides a screening method for greatly improving the efficiency of hybridoma technology.

The quantitative detection of single cell secretions is always limited by their accurate collection and the heterogeneity of different cells. In this work, a confined electrochemiluminescence (ECL) imaging microarray (CEIM) chip was designed to capture single or a few cells in each cylindrical microwell for high-throughput quantitation of cell-secreted dopamine (DA). The ITO surface at the bottom of microwells was functionalized with the film of DA aptamer modified coreactant-embedded polymer dots (Pdots), which endowed the chip with the abilities to both in situ recognize the target DA secreted from the cells and emit the ECL signal for responding the secreted target without need of any additional coreactant. At the applied potential of +1.4 V, the Pdots in the film emitted strong ECL signal, which could be quenched by the electrochemical oxidation product of DA in individual microwell for sensitive detection of single cell-released DA. The practicability of the proposed CEIM chip along with the ECL imaging and biosensing strategy was demonstrated by evaluating the amounts of single cell-released DA in different microwells under hypoxia stimulation. This protocol revealed the heterogeneity of cell secretion, and could be extended for quantitation of other secretions from different kinds of single cells.

Luminescent materials with aggregation-induced emission (AIE) have been widely used in chemosensors and biosensors based on signal change induced by physical aggregation of AIEgens. In this work, a novel coordinate bonding-induced emission (BIE) phenomenon of gold-glutathione complex was proposed and identified, and this specific coordinate BIE was further utilized to develop signal-enhanced methods for quantification of aluminum species including aluminum cation and polyoxocation AlO4Al12(OH)24(H2O)127+. Gold-glutathione (Au-GSH) complex has shown significant aggregation-induced emission characteristic, and it can sensitively respond to multiple external stimuli such as solvent polarity and pH via an emission-enhancing fashion. It is found that the introduction of aluminum cation to Au-GSH complex is able to more greatly enhance the luminescence through a coordinate bonding-induced emission process, and this BIE behavior is attributed to strong force induced by coordination reaction between glutathione ligands and aluminum cation. In comparison with AIE process, coordinate BIE process was shown to be a more efficient way to enhance the emission. This BIE property of Au-GSH complex was employed to measure aluminum cation and polyoxocation Al13 with good selectivity. This work provides a new coordinate bonding-induced emission phenomenon, and gives a demonstration of designing chemosensors for metal cations based on coordinate BIE process.

Copper nanoclusters have shown tremendous application perspective because of their outstanding luminescence properties, inherent biocompatibility, and easy accessibility; however, low emission brightness and poor resistance to ambient oxygen greatly limit their wide applications in long-term sensing and bioimaging. Herein, we develop an effective and general approach to enhancing the luminescence and stability of copper nanoclusters through in situ generation of a silica shell and further propose a versatile surface functionalization method to achieve functional copper nanoclusters via the formation of a second layer of a silica shell. The use of thiol-containing trialkoxysilane facilitates in situ generation of a silica shell on the surface of copper nanoclusters, and the existence of the first layer of a silica shell substantially improves the emission efficacy of copper nanoclusters. The introduction of a second layer of a silica shell not only greatly enhances the brightness and stability of copper na...

Most optical sensors for molecular oxygen were developed based on the quenching effect of the luminescence of oxygen-sensitive probes; however, the signal turn-off mode of these probes is undesirable to quantify and visualize molecular oxygen. Herein, we report a novel luminescence turn-on detection strategy for molecular oxygen via the specific oxygen-triggered bonding-induced emission of thiol-functionalized gold nanoclusters. Thiol-functionalized gold nanoclusters were prepared by a facile one-step synthesis, and as-prepared gold nanoclusters possess significant aggregation-induced emission (AIE) property. It is the first time to discover the oxygen-triggered bonding-induced emission (BIE) behavior of gold nanoclusters, which results in disulfide-linked covalent bonding assemblies with intensely red luminescence. This specific redox-triggered BIE is capable of quantitatively detecting dissolved oxygen in aqueous solution in a light-up manner, and trace amount of dissolved oxygen at ppb level is achieved based on this detection method. A facile and convenient test strip for oxygen detection was also developed to monitor molecular oxygen in a gas matrix. Covalent bonding-induced emission is proven to be a more efficient way to attain high brightness of AIEgens than a physical aggregation-induced emission process, and provides a more convenient and desirable detection method for molecular oxygen than the previous sensors.

A fluorometric biosensor has been developed to sensitively detect α-glucosidase activity and screen α-glucosidase inhibitors based on carbon quantum dots nanoprobe through supramolecular self-assembly. β-Cyclodextrin was covalently bonded to the surface of carbon quantum dots to prepare β-CD-CQDs nanoprobe. The presence of 4-nitrophenol drives self-assembly between β-CD-CQDs nanoprobe and 4-nitrophenol through host-guest recognition. This supramolecular assembly exhibits non-fluorescent nature, which results in strong quenching of the fluorescence of β-CD-CQDs nanoprobe. When 4-nitrophenyl-α- d -glucopyranoside was chosen as the substrate, it would be readily hydrolyzed to 4-nitrophenol in the presence of α-glucosidase. The linear correlation of quenched fluorescence to α-glucosidase level can be used to establish quantitative detection of α-glucosidase activity. The detection limit of this method can be lowered as 0.6 U/L, and possesses excellent sensitivity and selectivity. The function of this method to screen inhibitor of α-glucosidase was also assessed using acarbose as the example, and positive results supported its feasibility to screen potential inhibitors of α-glucosidase. This work proposes a new signal transduction mechanism through supramolecular assembly, and provides a sensitive detection method for α-glucosidase activity.

A novel bonding-induced emission (BIE) phenomenon of silyl-protected copper nanoclusters was observed and identified, and a new detection method for trace water in organic solvents was established based on a water-triggered BIE process. This assay employs simple and commercially available reagents and is capable of determining trace water at the ppm level.

Dynamic covalent B–O bonds are introduced to the design of a reversible fluorescence nanoswitch in response to the external stimulus of pH. This nanoswitch is based on a phenylboronic acid functionalized carbon quantum dot (PBA–CQD) nanoprobe, and constructed with reference to the two facts that the PBA–CQD probe can bind to p-nitrophenol to form a non-fluorescent conjugate via B–O bonds, and that the making and breaking of the B–O bonds between them can be controlled by pH changes. Excellent reversibility of this nanoswitch is illustrated by switching of the pH from 4 to 8. The reaction between the PBA–CQD nanoprobe and the p-nitrophenol resulting in switching off the fluorescence is further utilized to design a general detection strategy for enzyme activity when substrates that can generate p-nitrophenol through enzymatic reactions are chosen. The feasibility of the detection strategy is qualitatively assessed using α-glucosidase and β-galactosidase, and its practicability to quantitatively monitor enzyme activity is also demonstrated by taking α-glucosidase as an example. The detection limit of this method can be as low as 0.33 U L−1, which is much lower than those reported previously and is sufficiently low to be capable of α-glucosidase level detection in practical human samples. This study demonstrates excellent usability of dynamic covalent B–O bonds in the design of reversible switches and in the general detection of enzyme activity, and provides a sensitive, real-time assay for α-glucosidase based on carbon quantum dots.

A convenient, fluorescent dual-channel chemosensor on the basis of bis(3-pyridylmethyl)amine-functionalized carbon quantum dots (BPMA-CQDs) nanoprobe was constructed, and it can discriminatively detect glutathione from its analogues cysteine and homocysteine based on two distinctive strategies. Two distinct fluorescence responses of BPMA-CQDs probe to Cu(II) and Ag(I) were identified and further employed to achieve selective detection of Cu(II) and Ag(I) respectively. Based on the BPMA-CQDs/Cu(II) conjugate, discriminative detection of GSH was achieved in terms of correlation between the amounts of GSH and fluorescence recovery. The addition of GSH into BPMA-CQDs/Cu(II) system induces the reduction of Cu(II) to Cu(I), which could efficiently block PET process resulting in the following fluorescence recovery. Based on the BPMA-CQDs/Ag(I) conjugate, GSH assay could also be established on the basis of fluorescence response to GSH. The introduction of GSH into the preceding system triggers the competitive coordination to Ag(I) between BPMA and GSH, and silver ions are finally taken away by GSH from the probe, where the fluorescence is restored to its original weak state. Both of the detection strategies can achieve discriminative detection of GSH from Cys and Hcy. The assays showed good stability and repeatability, and covered a broad linear range of up to 13.3μM with a lowest detection limit of 42.0nM. Moreover, both of them were utilized to monitor GSH level in live cells.

A reversible luminescence nanoswitch through competitive hydrophobic interaction among copper nanoclusters, p-nitrophenol and α-cyclodextrin is established, and a reliable real-time luminescent assay for acid phosphatase (ACP) activity is developed on the basis of this luminescence nanoswitch. Stable and intensely luminescent copper nanoclusters (CuNCs) were synthesized via a green one-pot approach. The hydrophobic nature of CuNCs aggregate surface is identified, and further used to drive the adsorption of p-nitrophenol on the surface of CuNCs aggregate due to their hydrophobic interaction. This close contact switches off the luminescence of CuNCs aggregate through static quenching mechanism. However, the introduction of α-cyclodextrin switches on the luminescence since stronger host-guest interaction between α-cyclodextrin and p-nitrophenol causes the removal of p-nitrophenol from the surface of CuNCs. This nanoswitch in response to external stimulus p-nitrophenol or α-cyclodextrin can be run in a reversible way. Luminescence quenching by p-nitrophenol is further utilized to develop ACP assay using p-nitrophenyl phosphate ester as the substrate. Quantitative measurement of ACP level with a low detection limit of 1.3 U/L was achieved based on this specific detection strategy. This work reports a luminescence nanoswitch mediated by hydrophobic interaction, and provides a sensitive detection method for ACP level which is capable for practical detection in human serum and seminal plasma.

A convenient, reliable and highly sensitive assay for alkaline phosphatase (ALP) activity in the real-time manner is developed based on β-cyclodextrin-modified carbon quantum dots (β-CD-CQDs) nanoprobe through specific host-guest recognition. Carbon quantum dots were first functionalized with 3-aminophenyl boronic acid to produce boronic acid-functionalized CQDs, and then further modified with hydropropyl β-cyclodextrins (β-CD) through B-O bonds to form β-CD-CQDs nanoprobe. p-Nitrophenol phosphate disodium salt is used as the substrate of ALP, and can hydrolyze to p-nitrophenol under the catalysis of ALP. The resulting p-nitrophenol can enter the cavity of β-CD moiety in the nanoprobe due to their specific host-guest recognition, where photoinduced electron transfer process between p-nitrophenol and CQDs takes place to efficiently quench the fluorescence of the probe. The correlation between quenched fluorescence and ALP level can be used to establish quantitative evaluation of ALP activity in a broad range from 3.4 to 100.0U/L with the detection limit of 0.9U/L. This assay shows a high sensitivity to ALP even in the presence of a very high concentration of glucose. This study demonstrates a good electron donor/acceptor pair, which can be used to design general detection strategy through PET process, and also broadens the application of host-guest recognition for enzymes detection in clinical practice.

Brightly luminescent copper nanoclusters (CuNCs) were prepared via a facile one-step synthesis in organic phase, and a novel luminescent nanoswitch on the basis of CuNCs through alternation of the physical states between aggregation and dispersion in response to specific external stimuli was designed. Two states including aggregation state and disaggregation state corresponding to fluorescence on and off signaling can be readily switched in a reversible way based on the aggregation-induced emission and disaggregation-induced quenching mechanism, respectively. This reversible nanoswitch can be controlled by the external stimulus water or N,N'-dicyclohexylcarbodiimide (DCC). The bright luminescence due to aggregation of CuNCs in organic solvents can be effectively quenched by the introduction of a small amount of water, where a disaggregation-induced quenching takes place. This specific behavior is capable to quantify an ultralow level (ppm) of water in aprotic solvents. The excellent reversibility of the nanoswitch enables one to monitor water content in a continuous and recyclable way.

Thiolated copper nanoclusters (CuNCs) with aggregation-induced emission characteristic are becoming a novel luminescent material, but it is still a challenging task to retain its bright luminescence in a neutral solution. In this work, we report a new copper nanocluster with aggregation-induced emission (AIE) enhancement property using a hydrophobic molecule as the protecting ligand, and brightly luminescent AIE particles of copper nanocluster were prepared via hydrophobic interaction. These CuNCs AIE particles possess uniform rod-like shapes, with sizes in hundreds of nanometer, and an intense luminescence; more importantly, its luminescence remains stable in neutral and alkaline solutions. It is found that 4-nitrophenol is able to effectively quench the luminescence of CuNC AIE particles through strong hydrophobic interaction and electron transfer between them. This strong quenching effect was adopted to develop a luminescent assay for β-galactosidase at physiological condition. This work presents a demonstration of preparing CuNC AIE particles with bright luminescence at neutral condition and gives an example of the use of AIE particles in monitoring the enzyme activity.

This research investigates the brace-to-gusset connection designs to allow the braces buckle in the plane (IP) of the frame. In order to study the performance of the IP buckling brace connections with different design details, five 3,026 mm–long A36 H 175 × 175 × 7.5 × 11 mm braces were tested using cyclically increasing axial displacements. All specimens failed at an average axial strain less than 0.025 due to the brace fracture at the mid-length where severe local buckling had occurred. Pseudo-dynamic tests on a three-story special concentrically braced frame (SCBF) using the proposed brace end connection details for six A36 H 150 × 150 × 7 × 10 mm braces were conducted using the PGA = 597 cm/s2 LA03 record to confirm with the component tests. The knife plates and IP buckling braces sustained a peak 0.049 rad interstory drift under the design base earthquake without fracture. The highly nonlinear responses were satisfactorily predicted by OpenSees. Recommendations on the seismic design of the IP buckling brace connections are provided.

Due to the vital role of tyrosinase in melanin biosynthesis and its function as an important biomarker for melanoma cancer, highly sensitive detection of its activity using biocompatible materials is in urgent demand. Herein we report a convenient and highly sensitive fluorometric biosensor for tyrosinase activity detection based on biocompatible dopamine-functionalized Au/Ag nanoclusters (Dopa-Au/Ag NCs). Dopamine with redox property was covalently linked to Au/Ag NCs surface and formed a Dopa-Au/Ag NCs bioconjugate with strong blue fluorescence. Dopamine is readily oxidized by molecular oxygen under the catalysis of tyrosinase. After dopamine is transformed to o-dopaquinone, an intraparticle photoinduced election transfer (PET) process occurs between Au/Ag NCs and o-dopaquinone moiety, leading to the fluorescence quenching of the Dopa-Au/Ag NCs bioconjugate. Thus, this biosensor was utilized for sensitive and selective detection of tyrosinase in terms of the relationship between fluorescence quenching efficiency and tyrosinase activity. This study discovers that Au/Ag NCs and dopaquinone can serve as a good electron acceptor and donor pair which results in an efficient intraparticle photoinduced electron transfer process, and also provides another alternative way for tyrosinase activity monitoring.

Oxymatrine is one of the alkaloids extracted from the Chinese herb Sophora japonica (Sophora flavescens Ait.) with anti-inflammatory, immune reaction inhibiting, antiviral, and hepatocyte and antihepatic fibrosis protective activities. However, the effect of oxymatrine on heart failure is not yet known. In this study, the effect of oxymatrine on heart failure was investigated using a Sprague-Dawley rat model of chronic heart failure. Morphological findings showed that in the group treated with 50 and 100 mg/kg of oxymatrine; intermyofibrillar lysis disappeared, myofilaments were orderly, closely and evenly arranged; and mitochondria contained tightly packed cristae compared with the heart failure group. We investigated the cytosolic Ca2+ transients and sarcoplasmic reticulum (SR) Ca2+ content, and assessed the expression of ryanodine receptor (RyR2), SR-Ca2+ ATPase (SERCA2a), and L-type Ca2+ channel (dihydropyridine receptor, DHPR). We found that the cytosolic Ca2+ transients were markedly increased in amplitude in the medium- (ΔF/F 0 = 26.22 ± 2.01) and high-dose groups (ΔF/F 0 = 29.49 ± 1.17) compared to the heart failure group (ΔF/F 0 = 12.12 ± 1.35, P

Indoor air quality (IAQ) has been a matter of public concern in Hong Kong. Recently, the Hong Kong Government has recognized the potential risk and problems related to indoor air pollution, and it is striving to establish IAQ objectives for different types of indoor environments. This study attempts to provide more information about the present IAQ of local resident flats. Air pollutants measured in this study included carbon dioxide (CO2), respirable suspended particulate matter (PM10), formaldehyde (HCHO), volatile organic compounds (VOCs) and airborne bacteria. The results of this study indicate that the 8-h average concentrations of CO2 and PM10 in the domestic kitchens investigated were 14% and 67% higher than those measured in the living rooms. The indoor air pollution caused by PM10 was more serious in domestic kitchens than in living rooms as almost all of the kitchens investigated had higher indoor levels of PM10. The majority of the domestic living rooms and kitchens studied had average concentrations of airborne bacteria higher than 500 CFU/m3. The mean total bacteria count recorded in kitchens was greater than that obtained in living rooms by 23%. In homes where occupants smoke, the negative impact of benzene, toluene and m,p-xylene on the IAQ was greatly enhanced. The use of liquefied petroleum gas (LPG) stove has more significant impact on indoor VOCs than the use of cooking stoves with natural gas as cooking fuel.

Forty elemental concentrations in different size particles were measured at a roadside site and a suburban site of Hong Kong using a ten-stage MOUDI impactor (Mode 110). Some elements (Cr, Fe, Co, Cu, As and Ba) have clear spatial variability, with ∼100% higher concentrations in roadside atmosphere than in suburban atmosphere, showing obviously vehicle-related sources for those elements. However, it is contrary for three typical sea salt elements (Na, Cl and Br), showing more than 100% higher concentrations in suburban environment than in roadside environment, which is due to the influence of marine aerosols. The size distributions of elements are generally similar between roadside and suburban site. The elements Na, Mg, Al, Si, Cl, Ca, Ti, Mn and Fe mainly present in coarse mode (10 µm > diameter > 1 µm). The mass concentrations of K, V and Ni are distributed in both fine (diameter > 1 µm) and coarse mode. The size distributions of S, Pb, As, Se, Zn, Cu, Cd and Ba show a single peak at around 1 µm or less. The contributions of mineral dust to Total Suspended Particles (TSP) are similar for the traffic and suburban site, ∼13.8% and ∼14.2%, respectively. Sea salts account for ∼1.6% of TSP for the traffic site, and ∼6.0% for the suburban site.