Synthesis of 2H-imidazoles via copper-catalyzed homo/cross-coupling of oxime acetates.

A facile and practical protocol to construct 2H-imidazoles by applying an oxime acetate block as the sole component via oxidative homo/cross-coupling catalyzed by Cu(I) was developed. This strategy provides a straightforward method to produce a series of substituted 2H-imidazoles in moderate to excellent yields. The transformation process is straightforward to operate and is considered as a readily available catalytic system exhibiting good substrate compatibility, eliminating the necessity for pre-functionalization of azides or the use of additives.

A novel "mix-response" biosensor for colorimetric and photothermal dual-mode detection of sulfide ions in food based on silver-doping Prussian blue nanoparticle.

Effective identification of sulfur ions (S2-) in foodstuff is crucial for food safety and human health, but it remains challenging. Traditional single-mode colorimetric sensing methods are simple and sensitive, but are prone to interference from colored substances which can lead to false positives or negatives results. Herein, we develop a novel "mix-response" biosensor for colorimetric and photothermal dual-mode detection of S2- with good simplicity, sensitivity and portability. In this biosensor, silver-doping Prussian blue nanoparticle (SPB NPs) was used as signal output component, which not only exhibits blue color characteristics, but also has photothermal conversion properties activated by near-infrared (NIR) laser. Upon increasing the S2- concentration, the prepared SPB NPs undergo etching, leading to the formation of new silver sulfide precipitation (Ag2S), along with different colorimetric and photothermal response signals. For the portable visualization of S2-, the color information was recorded by a smartphone in combination with RGB (red channel) analysis and the evolution of the photothermal signal was documented by a thermal imager. The introduction of smartphone and handheld thermal imager in this "mix-response" biosensor makes it suitable for on-site quantitative detection of S2- without sophisticated instrument. Moreover, the development of this "mix-response" biosensor does not need the use of recognition probes (e.g. aptamers and reaction intermediates), thereby simplifying the construct procedures of sensing strategies and improving the economic efficiency of detection. More importantly, the photothermal response signals can overcome the interference of colored substances in foods, thereby reducing the false positives or negatives of the detection results.

Photodriven Radical Perfluoroalkylation-Thiolation of Unactivated Alkenes Enabled by Electron Donor-Acceptor Complex.

A clean and direct three-component radical 1,2-difunctionalization of various alkenes with perfluoroalkyl iodides and thiosulfonates enabled by the electron donor-acceptor complex has been developed under light illumination at room temperature. The approach offers a convenient and environmentally friendly route for the simultaneous incorporation of Csp3-Rf and Csp3-S bonds, affording valuable polyfunctionalized alkane derivatives containing fluorine and sulfur in satisfactory yields. Consequently, this methodology holds significant value and practicality in the field of organic synthesis.

A dual-mode ratiometric probe using europium-doped cyclen-functional carbon dots for fluorescent and point-of-care detection of tetracycline.

The overuse of tetracycline (TC) has led to the accumulation of antibiotic residues in drinking water and animal products, which can consequently lead to bacteria resistance and chronic disease in humans. Urgently addressing the need for a rapid, user-friendly, and point-of-care test for TC detection. In this work, we use cyclen and citric acid to synthesise carbon dots (CDs) with a unique ring-shaped structure on their surface and combine them with europium (Eu3+) to form an Eu-CDs fluorescent probe. In the presence of TC in aqueous systems, the Eu-CDs probe emits two distinctive fluorescent signals: the stable blue emission from cyclen-modified CDs and the red emission from Eu3+,showing a proportional increase with TC concentration. The developed Eu-CDs probe demonstrates accurate and selective detection capabilities for TC class antibiotics among various interfering factors. The Eu-CDs probe exhibits excellent linearity within the concentration range of 0.04-2.4 µM and achieves an impressive detection limit of 2.7 nM. Moreover, point-of-care Eu-CDs test strips are designed, allowing convenient on-site TC analysis through the detection of a colour change from blue to red under a portable UV light. The results highlight the effectiveness of the proposed dual-mode ratiometric fluorescent Eu-CDs probe and test strips, offering a practical point-of-care testing strategy for real-world TC detection applications.

Metal-free synthesis of 1,3-dichloro-1,5-diarylpentan-5-ones via cascade oxidative radical addition of styrenes with CHCl3.

A novel and efficient metal-free cascade oxidative radical addition of styrenes is developed for the construction of 1,3-dichloro-1,5-diarylpentan-5-ones. This protocol presents a practical one-pot procedure that delivers highly functionalized 1,3-dichloro-1,5-diarylpentan-5-ones in moderate-to-good yields with a broad substrate scope under mild conditions.

Refinery wastewater treatment via a multistage enhanced biochemical process.

Petroleum refinery wastewater (PRWW) that contains recalcitrant components as the major portion of constituents is difficult to treat by conventional biological processes. An effective and economical biological treatment process was established to treat industrial PRWW with an influent COD of over 2500 mg L-1 in this research. This process is mainly composed of internal circulation biological aerated filter (ICBAF), hydrolysis acidfication (HA), two anaerobic-aerobic (A/O) units, a membrane biological reactor (MBR), and ozone-activated carbon (O3-AC) units. The results showed that, overall, this system removed over 94% of the COD, BOD5, ammonia nitrogen (NH4+-N) and phosphorus in the influent, with the ICBAF unit accounting for 54.6% of COD removal and 83.6% of BOD5 removal, and the two A/O units accounting for 33.3% of COD removal and 9.4% of BOD5 removal. The degradation processes of eight organic pollutants and their removal via treatment were also analyzed. Furthermore, 26 bacteria were identified in this system, with Proteobacteria and Acidobacteria being the most dominant. Ultimately, the treatment process exhibited good performance in degrading complex organic pollutants in the PRWW.

The palladium-catalyzed direct C3-cyanation of indoles using acetonitrile as the cyanide source.

The ligand-free palladium-catalyzed C3-cyanation of indoles via direct C-H functionalization was achieved. This protocol, utilizing CH3CN as a green and readily available cyanide source, produced the desired products in moderate to good yields through transition-metal-catalyzed C-CN bond cleavage.

Weak coordinated nitrogen functionality enabled regioselective C-H alkynylation via Pd(II)/mono-N-protected amino acid catalysis.

The exploration of weak coordinated amine derivative enabled regioselective C-H functionalization remains challenging due to the elusive achievement of reactivity and selectivity simultaneously. Herein, regioselective C-H alkynylation of various readily transformable nitrogen functionalities was developed with great efficiency, with the assistance of the mono-N-protected amino acid (MPAA) ligand via Pd(ii) catalysis proceeding via 5, 6 and 7-membered palladacycle intermediates.

A study on the treatment efficiency of internal circulation biological aerated filters for refinery wastewater and the transformation of main organic pollutants.

In this study, an internal circulation biological aerated filter (ICBAF) reactor was applied to pretreat refinery wastewater containing large amounts of organic pollutants. According to the composition change of inlet-and-outlet water, the main organic pollutants, including micromolecular organic-acids, aldehydes, ketones, phenols, and so forth, degraded well in ICBAF unit. The concentration of organic acids, alcohols, and esters changed from 648 to 90 mg/L, 130 to 90 mg/L, and 158 to 228 mg/L, respectively. The average removal efficiencies of chemical oxygen demand (COD) and biological oxygen demand (BOD5) reached 54.62% and 83.64%, respectively. It was clear that the concentration of effluent organic acids in the ICBAF unit decreased significantly. The degradation process of organic acids, alcohols, and esters (among others) and the degradation pathway of organic acids were also discussed. Straight chain organic acids and naphthenic acids were degraded by α-oxidation, ß-oxidation, α- and ß-combined oxidation, or aromatization. The study demonstrates the potential of the ICBAF as an alternative for the high-efficiency pretreatment of refinery wastewater.

Analysis of glycan expression on cell surfaces by using a glassy carbon electrode modified with MnO2 nanosheets and DNA-generated electrochemical current.

Electrochemical assay for analysis of cell surface glycan expression is reported. Mannose on human breast cancer cells (type MCF-7) is selected as the glycan model. Gold nanoparticles are modified with binding aptamer for MCF-7 cells and act as electrochemical probe. The analysis of cell surface glycan expression follows a traditional sandwich protocol. Concanavalin A that can specifically recognize mannose is immobilized onto MnO2 nanosheets modified electrode for the capture of MCF-7 cells. Then, the modified gold nanoparticles are immobilized onto the electrode via the binding between MCF-7 cell and aptamer on the gold nanoparticles. The aptamer on the gold nanoparticles reacts with molybdate. More specifically, the reaction of the phosphate backbone of aptamer with molybdate results in the formation of a redox-active molybdophosphate precipitate and generates an electrochemical current. The current intensity at 0.20 V (vs. Ag/AgCl) is recorded to test the linear range of the assay. The assay shows an obvious response to MCF-7 cells with a wide linear range from 1.0 × 103 to 1.0 × 106 cells mL-1 and a limit of detection down to 300 cells mL-1. The assay can be used to selectively monitor the change of mannose expression on cell surfaces upon the treatment with the N-glycan inhibitor. Graphical abstractSchematic of an electrochemical assay for analysis of cell surface glycan expression of MCF-7 cancer cells.

Lipid-oligonucleotide conjugates for bioapplications.

Lipid-oligonucleotide conjugates (LONs) are powerful molecular-engineering materials for various applications ranging from biosensors to biomedicine. Their unique amphiphilic structures enable the self-assembly and the conveyance of information with high fidelity. In particular, LONs present remarkable potential in measuring cellular mechanical forces and monitoring cell behaviors. LONs are also essential sensing tools for intracellular imaging and have been employed in developing cell-surface-anchored DNA nanostructures for biomimetic-engineering studies. When incorporating therapeutic oligonucleotides or small-molecule drugs, LONs hold promise for targeted therapy. Moreover, LONs mediate the controllable assembly and fusion of vesicles based on DNA-strand displacements, contributing to nanoreactor construction and macromolecule delivery. In this review, we will summarize the general synthesis strategies of LONs, provide some characterization analysis and emphasize recent advances in bioanalytical and biomedical applications. We will also consider the relevant challenges and suggest future directions for building better functional LONs in nanotechnology and materials-science applications.

Enhanced photocatalytic performance of magnetic multi-walled carbon nanotubes/cerium dioxide nanocomposite.

An easily separated photocatalyst, magnetic multi-walled carbon nanotubes/cerium dioxide (MMWCNTs-CeO2) nanocomposite, has been successfully prepared by hydrothermal synthesis and subsequent loading of magnetic nanoparticles. The synthesized nanocomposite was characterized by scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, and vibrating sample magnetometer. The characterization results indicated the successful synthesis of MMWCNTs-CeO2 nanocomposite. Photocatalytic degradation experiments were conducted to evaluate photocatalytic properties of MMWCNTs-CeO2 by using methylene blue (MB) as a model pollutant. After a light irradiation of two hours, relatively high degradation efficiency (97.5%) of MB was achieved by using MMWCNTs-CeO2 nanocomposite as photocatalyst in the presence of H2O2. The incorporation of magnetic nanoparticles could not only facilitate the separation of photocatalyst from the solution after treatment, but also enhance the photocatalytic degradation efficiency. The results of this study suggested that the synthesized MMWCNTs-CeO2 nanocomposite showed an attractive prospect for application in the treatment of organic wastewater.

Amperometric detection of microRNA based on DNA-controlled current of a molybdophosphate redox probe and amplification via hybridization chain reaction.

An electrochemical sensor is described for the determination of microRNA-21 by combing the DNA generated current with target-triggered hybridization chain reaction (HCR). A thiol-modified hairpin capture probe was first immobilized on a gold electrode. In the presence of microRNA-21, hybridization leads to a conformational change of the capture probe. The conformational change triggers HCR to generate a long DNA strand on the surface of the electrode. The phosphate backbone of the long DNA strand then reacts with molybdate to form the redox redox probe molybdophosphate, and this generates an electrochemical current. The HCR triggered by microRNA increases the amount of phosphate groups due to the extension of the DNA length, and thus increases the response current. The electrode, best operated at a voltage of 0.20 V, was successfully applied to the analysis of microRNA-21 in (spiked) human serum samples. In our perception, it represents a promising tool for analyzing a variety of microRNA biomarkers. Graphical abstract Electrochemical sensor for detection of microRNA-21 by combing the DNA generated electrochemical current concept with target-triggered hybridization chain reaction (HCR) strategy is reported. DNA strands (S1 and S2) were assembled onto electrode through HCR reaction. MCH: 6-mercapto-1-hexanol.

Synthesis and photophysical properties of europium(III)-ß-diketonate complexes applied in LEDs.

Six ß-diketonate ligands were used to prepare the corresponding antenna europium(III) ternary complexes using 1,10-phenanthroline as an ancillary ligand. All the complexes exhibited high decomposition temperatures. Photophysical properties such as FT-IR spectra, UV-Vis absorption spectra, excitation and emission spectra, relative luminescent intensity ratios, luminescence decay curves and quantum yields based on the complexes were systematically studied and compared with each other. The energy-transfer mechanism was proposed as a ligand-sensitized luminescence process. Bright red light-emitting diodes (LEDs) were then fabricated by coating the complexes onto 395 nm-emitting InGaN chips. The light emission from the InGaN chips could be completely absorbed in the spectra of LEDs. The Commission International de I'Eclairage (CIE) chromaticity coordinates are close to the National Television Standard Committee (NTSC) standard value for the red color. All these findings indicate that these Eu(III) complexes are promising red phosphors for fabrication of near UV-based white LEDs.

A universal amplified strategy for aptasensors: enhancing sensitivity through allostery-triggered enzymatic recycling amplification.

A universal amplified sensing strategy based on endonuclease was developed for designing fluorescence aptasensors. By employing hairpin-structured design for both recognition and reporter probes to decrease background signal, and a nicking endonuclease to perform target-triggered enzymatic recycling amplification, the proposed biosensor showed high sensitivity to target protein. To demonstrate the feasibility of the design, immunoglobulin E (IgE) was studied as a model target. Upon the addition of target protein, the specific formation of IgE/aptamer complex induced the releasing of the 37-mer fragment which partially hybridized with the molecular beacon (MB) probe. In the presence of endonuclease Nt.BbvCI, the MB was cleaved into two parts. Then, the released 37-mer fragment hybridized with another MB, and triggered the second cycle of cleavage, leading to an accumulation of fluorescence signals. Under the optimal conditions, a detection limit of 5 pM was obtained. The proposed sensing system was used for detection of IgE in complex biological samples with satisfactory results.

Label-free optical bifunctional oligonucleotide probe for homogeneous amplification detection of disease markers.

Oligonucleotide-based detection schemes that avoid chemical modification possess significant advantages, including simplified design, intrinsic affinity for targets, low cost and ease to extend applications. In this contribution, we developed a label-free self-locked bifunctional oligonucleotide probe (signaling probe) for the detection of different disease markers in parallel. Two signal enhancement techniques based on isothermal circular strand-displacement polymerization reaction, cyclical nucleic acid strand-displacement polymerization (CNDP) and cyclical common (nonnucleic acid) target-displacement polymerization (CCDP), were employed to implement the amplification assay for p53 gene and PDGF-BB, respectively. The attractive assay properties confirmed the effectiveness of isothermal polymerization in common biosensing systems without evolving any chemical modification: PDGF could be detected down to 0.87ng/mL, and a dynamic response range of 8-5000ng/mL was achieved; The capability to screen the p53 gene was also considerably improved, including the detection limit, sensitivity, dynamic range and so on. Moreover, because no any chemical modification of the signaling probe was acquired and different targets were separately detected in homogeneous solution. This interrogating platform exhibits the design flexibility, convenience, simplicity and cost-effectiveness. The success achieved here is expected to serve as a significant step toward the development of robust label-free oligonucleotide probes in biomarker profiling and disease diagnostics.

High-sensitive electrochemical detection of point mutation based on polymerization-induced enzymatic amplification.

Here a highly sensitive electrochemical method is described for the detection of point mutation in DNA. Polymerization extension reaction is applied to specifically initiate enzymatic electrochemical amplification to improve the sensitivity and enhance the performance of point mutation detection. In this work, 5'-thiolated DNA probe sequences complementary to the wild target DNA are assembled on the gold electrode. In the presence of wild target DNA, the probe is extended by DNA polymerase over the free segment of target as the template. After washing with NaOH solution, the target DNA is removed while the elongated probe sequence remains on the sensing surface. Via hybridizing to the designed biotin-labeled detection probe, the extended sequence is capable of capturing detection probe. After introducing streptavidin-conjugated alkaline phosphatase (SA-ALP), the specific binding between streptavidin and biotin mediates a catalytic reaction of ascorbic acid 2-phosphate (AA-P) substrate to produce a reducing agent ascorbic acid (AA). Then the silver ions in solution are reduced by AA, leading to the deposition of silver metal onto the electrode surface. The amount of deposited silver which is determined by the amount of wild target can be quantified by the linear sweep voltammetry (LSV). The present approach proved to be capable of detecting the wild target DNA down to a detection limit of 1.0×10(-14) M in a wide target concentration range and identifying -28 site (A to G) of the ß-thalassemia gene, demonstrating that this scheme offers a highly sensitive and specific approach for point mutation detection.

An aptazyme-based electrochemical biosensor for the detection of adenosine.

In this work, an aptazyme-based electrochemical biosensor for the detection of adenosine is reported. Aptazyme activity was modulated by appending an "inhibitor" oligonucleotide strand containing a 32-base adenosine aptamer to the 8-17 DNAzyme. In the absence of adenosine, the DNAzyme could not form appropriate catalytic structure due to the binding with the inhibitor strand. Upon adenosine binding to the aptamer, the inhibitor strand was dissociated from the DNAzyme sequence. This allowed the DNAzyme to open and bind with the hairpin substrate, and DNAzyme activity was thereby induced, cleaving the substrate at its ribonucleotide site in the presence of Pb(2+). Cleavage of the substrate yields two single-stranded products, one of which was ferrocene-tagged and acted as the signal probe. The thiolated probe modified on the gold electrode could capture the signal probe. As a result, the ferrocene (Fc) moiety was brought in close proximity to the electrode surface and the Faradaic current was observed. This electrochemical biosensor was proved to have a wide dynamic range from 5 nM to 2000 nM with a detection limit of 5 nM. The fabricated sensor is shown to exhibit high sensitivity and desirable selectivity, which might be promising for the rational construction of aptazyme-based biosensors and the determination of adenosine in clinical examination.

Electrochemical detection of thrombin by sandwich approach using antibody and aptamer.

The goal of this work was to introduce a modified electrochemical sandwich model for target protein detection, exploiting antibody as the capturing probe, aptamer as the detection probe and methylene blue as the electrochemical active marker intercalating in the probing aptamer without previous labeling. With appropriate design of the sequence of the aptamer, the aptamer was successfully utilized instead of antibody for obtaining the electrochemical detection. A special immobilization interface consisting of nanogold-chitosan composite film was used to improve the conductivity and performance characteristics of the electrode. The capturing antibody was linked to the glassy carbon electrodes modified with composite film via a linker of glutaraldehyde. Differential pulse voltammetry was performed to produce the response signal. Thrombin was taken as the model target analyte to demonstrate the feasibility of proposed methodology. The sensor shows the linear response for thrombin in the range 1-60 nM with a detection limit of 0.5 nM. The proposed approach provides an alternative approach for sandwich protein assay using aptamers.

Electrochemical immunosensor with aptamer-based enzymatic amplification.

An electrochemical immunosensor is reported by using aptamer-based enzymatic amplification with immunoglobulin E (IgE) as the model analyte. In this method, the IgE antibody is covalently immobilized as the capture probe on the gold electrode via a self-assembled monolayer of cysteamine. After the target is captured, the biotinylated anti-IgE aptamer is used as the detection probe. The specific interaction of streptavidin-conjugated alkaline phosphatase to the surface-bound biotinylated detection probe mediates a catalytic reaction of ascorbic acid 2-phosphate substrate to produce a reducing agent ascorbic acid. Then silver ions in the solution can be reduced, leading to the deposition of metallic silver on the electrode surface. The amount of deposited silver, which is determined by the amount of IgE target bound on the electrode surface, can be quantified using the stripping voltammetry. The results obtained demonstrated that the electrochemical immunosensor possesses high specificity and a wide dynamic range with a low detection limit that possibly arises from the combination of the highly specific aptamer and the highly sensitive stripping determination of enzymatically deposited silver.