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Natural active polysaccharides are attracting increased attention from pharmaceutical industries for their valuable biological activities. However, the application of polysaccharides has been restricted due to their relatively large molecular weight, complex structure, and instability. Metal-organic frameworks (MOFs) have emerged to help deliver cargo to specific locations, achieving the objectives of eliminating the potential damage to the body, protecting the drugs, and improving therapeutic effectiveness. Here, a pH-responsive zeolitic imidazolate framework (ZIF-8) was synthesized to encapsulated three sulfated polysaccharides (heparin, fucan sulfate, fucosylated chondroitin sulfate) and a non-sulfated polysaccharide, hyaluronic acid. The resulting polysaccharides@ZIF-8 biocomposites showed differences in terms of morphology, particle size, encapsulation, and release efficiency. These biocomposites retained antithrombotic activity and the framework ZIF-8 effectively protected these polysaccharides from degradation and prolonged shelf-life of the anticoagulants from the unfavorable environment.

The family with sequence similarity 13 member A (FAM13A) gene has been discovered in recent years and is related to metabolism. In this study, the function of FAM13A in precursor adipocyte proliferation in Qinchuan cattle was investigated using fluorescence quantitative polymerase chain reaction (PCR), western blotting, 5-ethynyl-2′-deoxyuridine staining, and other tests. FAM13A promoted precursor adipocyte proliferation. To determine the pathway FAM13A was involved in, transcriptome sequencing, fluorescence quantitative PCR, western blotting, and other tests were used, which identified the hypoxia inducible factor-1 (HIF-1) signalling pathway. Finally, cobalt chloride, a chemical mimic of hypoxia, was used to treat precursor adipocytes. mRNA and protein levels of FAM13A were significantly increased after hypoxia. Thus, FAM13A promoted bovine precursor adipocyte proliferation by inhibiting the HIF-1 signalling pathway, whereas chemically induced hypoxia negatively regulated FAM13A expression, regulating cell proliferation.

D-Glucuronyl C5-epimerase (C5-epi), which converts D-glucuronic acid to L-iduronic acid, is a crucial enzyme in the preparation of bioengineered heparin, which provides an alternative way to produc...

Flavonoids possess diverse bioactivity and potential medicinal values. Glycosylation of flavonoids, coupling flavonoid aglycones and glycosyl groups in conjugated form, can change the biological activity of flavonoids, increase water solubility, reduce toxic and side effects, and improve specific targeting. Therefore, it is desirable to synthesize various flavonoid glycosides for further investigation on their medicinal values. Compared with chemical glycosylations, biotransformations catalyzed by uridine diphospho-glycosyltransferases provide an environmentally friendly way to construct glycosidic bonds without repetitive chemical synthetic steps of protection, activation, coupling, and deprotection. In this review, we will summarize the existing knowledge on the biotechnological glycosylation reactions either in vitro or in vivo for the synthesis of flavonoid O- and C-glycosides and other rare analogs.Key points• Flavonoid glycosides usually show improved properties compared with their flavonoid aglycones.• Chemical glycosylation requires repetitive synthetic steps and purifications.• Biotechnological glycosylation reactions either in vitro or in vivo were discussed.• Provides representative synthetic examples in detail.

Titanium carbide quantum dots (Ti3C2 QDs) derived from two-dimensional (2D) Ti3C2Tx (MXene) are the rising-star material recently. Herein, nitrogen-doped Ti3C2 QDs (N-Ti3C2 QDs) were synthesized via a solvothermal method. The obtained N-Ti3C2 QDs exhibited excitation-dependent photoluminescence, antiphotobleaching, and dispersion stability. Furthermore, by combining the N-Ti3C2 QDs and DAP (2,3-diaminophenazine, the oxidative product of o-phenylenediamine) as a composite nanoprobe (N-Ti3C2 QDs@DAP), we developed a dual-emission reverse change ratiometric sensor to quantitatively monitor H2O2 based on photoinduced electron-transfer effects, where N-Ti3C2 QDs acted as the donor and DAP as the acceptor. On the basis of the xanthine converting into H2O2 through the catalysis of xanthine oxidase, the N-Ti3C2 QDs@DAP nanoprobe was also exploited for xanthine sensing. As a result, the proposed assay was demonstrated to be highly sensitive for H2O2 and xanthine with detection limits of 0.57 and 0.34 μM, respectively. In a word, we have investigated the application of N-Ti3C2 QDs in H2O2 and xanthine sensing and opened a new and exciting avenue for the N-Ti3C2 QDs in biosensing.

In this research, we attempted to develop a sensitive colorimetric sensing strategy for the detection of acid phosphatase (ACP) based on MnO2 nanosheets and explored its applications in screening and evaluating inhibitors of ACP. The MnO2 nanosheets exhibit intrinsic biomimetic oxidase activity, which can catalyze the oxidation of the colorless 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) diammonium salt (ABTS) into green oxidized ABTS (oxABTS). Upon the introduction of ACP, l-ascorbic acid-2-phosphate can be dephosphorylated to ascorbic acid, which arouses the disintegration of MnO2 nanosheets into Mn2+ ions. This disintegration weakens the enzyme mimicking activity of the MnO2 nanosheets, leading to the impediment of the oxidation of ABTS. Conversely, in the absence of ACP, the ABTS is rapidly oxidized by MnO2, leading to a significant colorimetric signal change. The absorbance difference at 420 nm displayed a linear relationship with the concentration of ACP ranging from 0.075 to 0.45 mU·mL-1, generating a detection limit of 0.046 mU·mL-1. In the inhibition assays, this sensing platform provided simple detection for parathion-methyl (PM), a representative inhibitor of ACP. The facile evaluation of the inhibitory effect of PM, including its IC50 toward ACP, was also realized.

In this paper, a flower-like molybdenum disulfide material was prepared by hydrothermal method and firstly used as adsorbents in solid-phase extraction process for enriching N-nitrosoamines. Molybdenum disulfide exhibited three-dimensional petal-like microspheres with about 500 nm in diameter. The relevant analyte extraction and elution parameters (sample volumes, solution pH, washing solvents, elution solvents and elution volumes) were optimized to improve the solid-phase extraction efficiency. The solid-phase extraction process coupled with high-performance liquid chromatography tandem mass spectrometry for determining N-nitrosoamines in environmental water samples was established. The limits of detection were in the range of 0.01-0.05 ng/mL. The satisfactory recoveries (68.9%-106.1%) were obtained at three different spiked concentrations (2, 5 and 8 ng/mL) in water samples, and the relative standard deviations were between 1.96% and 8.38%. This proposed method not only showed high sensitivity and good reusability, but also provided a new adsorbent for enriching trace N-nitrosoamines in environmental water samples. This article is protected by copyright. All rights reserved.

In this paper, magnetic zeolitic imidazolate framework-8 composites were synthesized by a simple in situ method and then used for the first time as an adsorbent in magnetic solid-phase extraction for extracting multiple strobilurin fungicides. The magnetic composites were characterized in detail. The results showed that Fe3O4 nanoparticles were attached on the surface of zeolitic imidazolate framework-8 with a uniform particle size of 150-200 nm and that the magnetic composites possessed a perfect molecular transfer rate towards strobilurin fungicides. The parameters of the magnetic solid-phase extraction process, including solution pH, adsorption time, solution volume, elution solvent, and elution volume, were investigated. Under the optimum conditions, the recoveries of all five fungicides fell within the range 80.8-109.0% with spiking levels of 10, 20 and 50 ng mL-1. A magnetic solid-phase extraction-high performance liquid chromatography-tandem mass spectrometry method based on the magnetic composites was established and confirmed to be simple, time-efficient and highly sensitive.

Transcription factors (TFs) are critical proteins that regulate the expression of genes, and the abnormal change of TFs levels is directly related to physical dysfunctions. Herein, we developed a clustered regularly interspaced short palindromic repeats (CRISPR)-based biosensor for the measurement of TFs level with the assistance of exonuclease protection assay. A dsDNA (activator) with the ability to activate Cas12a was engineered to contain TFs binding domain, and the binding between TFs and the activator can protect the dsDNA from being digested by exonuclease III (Exo III). The reserved activator then triggered a CRISPR/Cas12a reporting reaction to produce fluorescent signal for detection. In the detection of nuclear factor-kappa B (NF-κB) p50 subunit, the limit of detection of 0.2 pM and limit of quantification of 0.6 pM were obtained respectively, and the performance of this biosensor has been challenged by cell nucleoprotein extracts. Additionally, this method can be applied in the screening and evaluation of TFs inhibitors, calculating the IC50 of oridonin. Integrating merits including high sensitivity, low cost, and good portability, this method may enrich the arsenal for TFs-related applications.

The CRISPR/Cas technology, derived from an adaptive immune system in bacteria, has been awarded the Nobel Prize in Chemistry in 2020 for its success in gene editing. Increasing reports reveal that CRISPR/Cas technology has a wide scope of applications and it could be incorporated into biosensors for detecting critical analytes. CRISPR-powered biosensors have attracted significant research interest due to their advantages including high accuracy, good specificity, rapid response, and superior integrity. Now the CRISPR technology is not only admirable in nucleic acid monitoring, but also promising for other kinds of biomarkers' detection, including metal ions, small molecules, peptides, and proteins. Therefore, it is of great worth to explore the prospect, and summarize the strategies in applying CRISPR technology for the recognition of a broad range of targets. In this review, we summarized the strategies of CRISPR biosensing for non-nucleic-acid analytes, the latest development of nucleic acid detection, and proposed the challenges and outlook of CRISPR-powered biosensors.

In this work, a red emission fluorescent probe CBZ-BOD@zeolitic imidazolate framework-8 (ZIF-8) was fabricated based on metal-organic frameworks (MOFs) for detecting carboxylesterase 1 (CES1). The small molecule probe CBZ-BOD was first synthesized and then used to prepare the functionalized MOF material. ZIF-8 was chosen as an encapsulation shell to improve the detection properties of CBZ-BOD. Using this unique porous materials, ultrasensitive quantification of CES1 and chlorpyrifos was successfully realized. The low detection limit and high fluorescence quantum yield were calculated as 1.15 ng/mL and 0.65 for CBZ-BOD@ZIF-8, respectively. CBZ-BOD@ZIF-8 has good biocompatibility and was successfully applied to monitor the activity of CES1 in living cells. A molecular docking study was used to explore the binding of CES1 and CBZ-BOD, finding that CES1 can bind with the probe before and after hydrolysis. This type of materialized probe can inspire the development of fluorescent tools for further exploration of many pathological processes.

Nitrobenzene compounds are highly toxic pollutants with good stability, and they have a major negative impact on both human health and the ecological environment. Herein, it was found for the first time that fluorescent DNA-silver nanoclusters (DNA-AgNCs) can catalyze the reduction of toxic and harmful nitro compounds into less toxic amino compounds with excellent tolerance to high temperature and organic solvents. In this study, the reduction of p-nitrophenol (4-NP) as a model was systematically investigated, followed by expending the substrate to disclose the versatility of this reaction. This report not only expanded the conditions for utilizing catalytic reduction conditions of DNA-AgNCs as an efficient catalyst in the control of hazardous chemicals but also widened the substrate range of DNA-AgNCs reduction, providing a new angle for the application of noble metal nanoclusters.

Flap endonuclease 1 (FEN1), an endogenous nuclease with the ability to cleave the 5' overhang of branched dsDNA, is of significance in DNA replication and repair. The overexpression of FEN1 is common in cancer because of the ubiquitous upregulation of DNA replication; thus, FEN1 has been recognized as a potential biomarker in oncological investigations. However, few analytical methods targeting FEN1 with high sensitivity and simplicity have been developed. This work developed a signal-amplified detection of FEN1 based on the cleavage-induced ligation of a dumbbell DNA probe and rolling circle amplification (RCA). A flapped dumbbell DNA probe (FDP) was rationally designed with a FEN1 cleavable flap at the 5' end. The cleavage generated a nick site with juxtaposed 5' phosphate and 3' hydroxyl ends, which were linkable by T4 DNA ligase to form a closed dumbbell DNA probe (CDP) with a circular conformation. The CDP functioned as a template for RCA, which produced abundant DNA that could be probed using SYBR Green I. The highly sensitive detection of FEN1 with a limit of detection of 15 fM was achieved, and this method showed high specificity, which enabled the quantification of FEN1 in real samples. The inhibitory effects of chemicals on FEN1 were also evaluated. This study represents the first attempt to develop an FEN1 assay that involves signal amplification, and the novel biosensor method enriches the tools for FEN1-based diagnostics.

Antibiotics are a category of chemical compounds used to treat bacterial infections and are widely applied in cultivation, animal husbandry, aquaculture, and pharmacy. Currently, residual antibiotics and their metabolites pose a potential risk of allergic reactions, bacterial resistance, and increased cancer incidence. Residual antibiotics and the resulting bacterial antibiotic resistance have been recognized as a global challenge that has attracted increasing attention. Therefore, monitoring antibiotics is a critical way to limit the ecological risks from antibiotic pollution. Accordingly, it is desirable to devise new analytical platforms to achieve efficient antibiotic detection with excellent sensitivity and specificity. Quantum dots (QDs) are regarded as an ideal material for use in the development of antibiotic detection biosensors. In this review, we characterize different types of QDs, such as silicon, chalcogenide, carbon, and other doped QDs, and summarize the trends in QD-based antibiotic detection. QD-based sensing applications are classified according to their recognition strategies, including molecularly imprinted polymers (MIPs), aptamers, and immunosensors. We discuss the advantages of QD-derived antibiotic sensors, including low cost, good sensitivity, excellent stability, and fast response, and illustrate the current challenges in this field.

Sugar nucleotides are the principle building blocks for the synthesis of most complex carbohydrates and are crucial intermediates in carbohydrate metabolism. Uridine diphosphate (UDP) monosaccharides are among the most common sugar nucleotide donors and are transferred to glycosyl acceptors by glycosyltransferases or synthases in glycan biosynthetic pathways. These natural nucleotide donors have great biological importance, however, the synthesis and application of unnatural sugar nucleotides that are not available from in vivo biosynthesis are not well explored. In this review, we summarize the progress in the preparation of unnatural sugar nucleotides, in particular, the widely studied UDP-GlcNAc/GalNAc analogs. We focus on the ‘two-block’ synthetic pathway that is initiated from monosaccharides, in which the first block is the synthesis of sugar-1-phosphate and the second block is the diphosphate bond formation. The biotechnological applications of these unnatural sugar nucleotides showing their physiological and pharmacological potential are discussed.

Transcription factors (TFs) are the key proteins for the decision of cell fates, and they have been recognized as potent markers for diagnostic and treatment of diseases. Herein, we report on a highly sensitive biosensor for the detection of TFs based on the CRISPR/Cas12a system. This biosensor was accomplished based on the competitive binding of the Cas12a-crRNA and TFs towards a dsDNA referred to as activator. Without TFs, the activator can be recognized by Cas12a-crRNA and cause the activation of the DNase activity of Cas12a. When TFs were added, the TFs can bind with the activator because the activator was designed to contain the specific binding sites of target TFs. We find that this binding can inhibit the association between Cas12a-crRNA and the activator, which hinders the activation of Cas12a. As a proof-of-concept, the rapid detection of five kinds of TFs was presented, and the detection was extended to the analysis of TFs expression in xenograft solid tumors from mice. This investigation is the first attempt to apply CRISPR technology in the sensing of TFs, and it discloses that the blocking of activator can be applied as a new sensing mechanism for the development of CRISPR-based biosensor.

In this paper, we introduce a synthetic biomimetic receptors-based surface enhanced Raman scattering (SERS) sensor for highly specific recognition and detection of acid phosphatase in complex biological samples. It depends on the establishment of molecular imprinted polymers (MIPs) which capture the target glycoprotein via biomimetic recognition, and SERS probes which bind to glycoproteins by boronate affinity. The MIPs layer was synthesized through self-polymerization of dopamine on the surface of glycoprotein-immobilized polymeric skeletons, which was prepared by choosing 4-vinylphenylboronic acid (VPBA) as functional monomers, pentaerythritol triacrylate (PETA) as crosslinker, ethyleneglycol (EG) and cyclohexanol as porogens. The accessible and stable recognition sites allowed the rebinding of the template and offered good reproducibility. The proposed biomimetic recognition-based SERS sensor showed superb performances for acid phosphatase detection with high sensitivity (LOD of 0.1 ng mL−1) and excellent selectivity.

Transcription factors (TFs) regulate information flow from gene to protein, and they are recognized as key indicators to reflect cellular processes. Facile monitoring of TFs may aid diagnostics and treatment, but we still lack of techniques for highly efficient detection of them. In this research, a hybrid material consisting of DNA-silver nanoclusters (DNA-AgNCs) and polypyrrole nanoparticles (PPyNPs) was built for TFs detection. The designed DNA-AgNCs have a hairpin-shaped nucleic acid architecture with a double-stranded stem for recognizing TFs and a single-stranded loop for interacting with PPyNPs. In the absence of TFs, DNA-AgNCs are absorbed to PPyNPs, resulting in fluorescent quenching. While in the presence of TFs, the binding between TFs and the DNA-AgNCs caused desorption of DNA-AgNCs via steric hindrance mechanism. Accordingly, the increase of fluorescence derived from desorption is used for quantifications. Derived from low non-specific protein absorption features of PPyNPs, detection limit of 70 pM for NF-κB p50 and 110 pM for p53 were obtained. Then, by absorbing two kinds of DNA-AgNCs to PPyNPs, label-free multiplexed detection of TFs was first realized. Additionally, we suggested that this platform can be developed for drug screening by evaluating inhibitory effect of a pair of optical isomers towards TFs.

Crop residue is a source of energy and nutrients for microbial growth, and can be converted into soil organic matter (SOM). However, there are still knowledge gaps on how the interaction of crop residue and supplementary nutrients (nitrogen, phosphorus and sulfur) influence the fate of residue in microbial biomass carbon (MBC) and microbial use efficiency. Here, we quantified the carbon (C) mineralization of wheat residue (δ13C 494‰) and microbial C use efficiency at ecosystem scale (CUEE) with two levels of the residue (6.7 and 20.0 g kg−1 soil) and three levels of nutrients in Luvisol and Vertisol under a controlled laboratory condition (22 °C). Between 48 and 61% of residue-C was mineralized over 245 days. The residue CUEE was similar across the two levels of the residue on day 3 (i.e., 0.29–0.40 in the Luvisol and 0.41–0.50 in the Vertisol) and then decreased over time, likely because of greater increase in cumulative total respiration and microbial turnover, relative to microbial growth. The residue CUEE was 20–55% lower in the high-residue, compared with (cf.) low-residue, input after day 10, which may have resulted from the greater loss of C via overflow respiration (microbial respiration without the production of energy) and turnover of high MBC. Narrowing of the C-nutrient imbalance increased residue-C mineralization, residue-derived MBC, and residue CUEE only under the high-residue input scenario where nutrients were possibly a limiting factor for microbial growth. Consequently, the results indicate a higher efficiency of SOM formation from returning of residue to soils under (i) low-residue (cf. high-residue) with or without nutrients, and (ii) high-residue with nutrient inputs (cf. no nutrient). The findings of the integrated residue–nutrient management on dynamics of residue-derived MBC and residue CUEE can be used to improve predictive performance of the models on specific soil functions such as SOM storage in agro-ecosystems.

The main object of this paper is to present the analyze of the degradation mechanism of the electrical properties and polymeric materials for a batch of crystalline-silicon photovoltaic modules, which were installed in the hot-humid region in the south of China for 30 years. Although significant degradation of polymers (EVA and back-sheet) is observed, the average power output is only 6.53% below the name plate of the modules after 30 years in the field. The analysis of electrical performance indicated that the decline of short-circuit current (Isc) is, in this case, the main cause of power degradation. The degradation of polymeric materials, first observed through visual inspection followed by several analytical methods, such as XPS, optical measurements, or measurement of the degree of crosslinking and mechanical properties, is characterized by a high degree of yellowing of the Ethylene Vinyl Acetate(EVA) and cracks of the back-sheet. In addition, some corrosion of Ag grid is also observed. The high water vapor transmission rate (WVTR) of back-sheet, and the presence of cracks, accelerated the corrosion of metal, but it does not directly result in a decrease of the power output, and no obvious degradation of the filling factor is observed. The increase of the Yellow Index of the EVA directly results in optical loss, which is believed to be the main cause of the decline of the short-circuit current. The loss in short-circuit current caused by EVA discoloration is 12.6% in average, which agrees well with that of electrical performance analysis. Failure cause analysis reveals that there is no direct relationship between the power degradation and the degradation behavior of packaging materials except EVA discoloration.

In this work, based on purifying the analysis system by magnetic separation, we constructed a turn-on fluorescent assay for highly sensitive detection of possible biomarkers, employing adenosine as the model target analyte. Aptamer labeled-carbon dots (Apt-CDs) was applied as fluorescence probes as well as selective recognition elements, while Fe3O4@polypyrrole (Fe3O4@PPY) was used as fluorescence quenching and magnetic separating materials for system purification. In absence of adenosine, the Apt-CDs were attached to the surface of PPY through π-π stacking and hydrophobic interaction and its fluorescence was quenched by Fe3O4@PPY. In presence of adenosine, the aptamer could specifically bind with adenosine to form a three dimensional Apt-CDs-adenosine complex and detach from PPY, leading to the fluorescence recovery of Apt-CDs. More importantly, with analysis system purification via twice convenient magnetic separations of free CDs and Apt-CDs-adenosine complex respectively, the detection limit could be reduced from 8 nmol L−1 to 0.15 nmol L−1. This concept offers potential application for simple, rapid, cost-effective, and highly sensitive assay of biological samples.

Biomimetics affords versatile ways to develop new routes for protecting metals from corrosion. In this report, focusing on the inhibition of corrosion for magnesium alloy, different biomimetic strategies were studied. Using a facile immersion method followed by surface modification, a lotus leaf-inspired superhydrophobic surface (SHS) is achieved. However, in the water phase, the SHS is found to be vulnerable, and a hydrophilic defect spot can irreversibly deteriorate the corrosion inhibition capability. Based on the infusion of dimethyl silicone oil into a SHS matrix, a dual biomimetic slippery liquid-infused porous surface (SLIPS) in a partition matrix inspired by both Nepenthes pitcher and pomegranate fruit was prepared. In a 3.5 wt% NaCl solution, the corrosion resistance of the SLIPS is found to be four orders of magnitude larger than that of the untreated and superhydrophobic magnesium alloys. In comparison with the vulnerable SHS, the SLIPS can tolerate repeat mechanical damage, exhibiting prominent self-healing properties.

Flap endonuclease 1 (FEN1) is a nuclease overexpressed in cells with a high replicate rate, which has been recognized as a potential biomarker in the molecular diagnosis of cancers. In this work, we developed a fluorescent biosensor based on exponential amplification reaction (EXPAR) to realize the rapid and sensitive detection of FEN1. A DNA probe specific for FEN1 is used for the generation of reporter DNA (rDNA), and then the rDNA hybridizes with a template, triggering EXPAR to produce substantial rDNA exponentially. However, when no FEN1 is in the system, the EXPAR will not be initiated because of the lack of rDNA. Derived from the high amplification efficiency of EXPAR, the rapid quantification of FEN1 with a limit of detection (LOD) of 0.5 fM was realized. It is also revealed that this biosensor exhibits good selectivity towards FEN1 under the challenge from real samples including extracts of cells and solid tumors. Furthermore, this sensor was reengineered for the analysis of FEN1 inhibitors, which shows promise in the screening and evaluation of potential drugs targeting FEN1. This work integrates EXPAR into the biosensing of FEN1 for the first time, which provides a promising tool for FEN1-related biomedical investigations.

Adenosine is an endogenous nucleotide pivotally involved in nucleic acid and energy metabolism. Its excessive existence may indicate tumorigenesis, typically lung cancer. Encouraged by its significance as the clinical biomarker, sensitive assay methods towards adenosine have been popularized, with high cost and tedious procedures as the inevitable defects. Herein, we report a label-free aptamer-based exonuclease III (Exo III) amplification colorimetric aptasensor for the highly sensitive and cost-effective detection of adenosine. The strategy employed two unlabeled hairpin DNA oligonucleotides (HP1 and HP2), where HP1 contained the aptamer towards adenosine and HP2 embedded the guanine-rich sequence (GRS). In the presence of adenosine, hairpin HP1 could form specific binding with adenosine and trigger the unfolding of HP1's hairpin structure. The resulting adenosine-HP1 complex could hybridize with HP2, generating the Exo III recognition site. After Exo III-assisted degradation, the GRS was released from HP2, and the adenosine-HP1 was released back to the solution to combine another HP2, inducing the cycling amplification. After multiple circulations, the released ample GRSs were induced to form G-quadruplex, further catalyzing the oxidation of TMB, yielding a color change which was finally mirrored in the absorbance change. On the contrary, the absence of adenosine failed to unfold HP1, remaining color unchanged eventually. Thanks to the amplification strategy, the limit of detection was lowered to 17 nM with a broad linear range from 50 nM to 6 μM. The proposed method was successfully applied to the detection of adenosine in biological samples and satisfying recoveries were acquired.

This study examined the effect of root pruning (RP) and nitrogen fertilization (NF) alone or in combination (RP-NF) on growth properties of 3-year-old ‘Fuji’ apple (Malus domestica Borkh.) trees. The results of pot experiments showed that the trees were sensitive to RP and NF alone or in combination in terms of root architecture, leaf photosynthesis, and canopy growth. Compared with the control, NF and RP-NF increased root length density and tips, while RP and RP-NF decreased root surface area and volume. RP alone reduced coarse root length (2.0–4.0 and >4.0 mm diameter), while RP-NF simultaneously increased fine root length (≤1.0 mm diameter) and reduced coarse root length. Moreover, RP increased leaf chlorophyll content and transpiration rate, while RP-NF increased net photosynthetic rate and water use efficiency. RP-NF resulted in no differences in dry matter weight, root-shoot ratio, or leaf area compared with the control. Inhibiting vegetative growth by RP-NF provided an effective way to impr...

The authors describe a versatile aptasensing scheme based on the use of polypyrrole nanoparticles (PPyNPs) and DNA-silver nanoclusters (DNA-AgNCs) for multiple target detection. The DNA-AgNCs consist of two functional domains, viz. (a) a nucleation domain for attaching the metal core of the nanoclusters, and (b) a recognition domain which consists of a single-stranded aptamer. In the absence of analytes, the single-strand recognition domain will be absorbed onto the surface of the PPyNPs through π stacking and hydrophobic interactions. As a result, the red fluorescence of the DNA-AgNCs (with excitation/emission peaks at 535/625 nm) is quenched by the PPyNPs. On introducing the analytes, the DNA-AgNCs will bind them. This leads to the desorption of DNA-AgNCs and the recovery of the red fluorescence. Based on the above strategy, a versatile, sensitive and selective aptasensor was established for detection of adenosine, thrombin and interferon-gamma. The method was applied to the detection of the above targets in (spiked) serum samples and gave satisfactory results, with detection limit of 0.58 nM for IFN-γ, 0.39 nM for adenosine, and 2.2 nM for thrombin. The use of PPyNPs results in uniquely low non-specific absorption and in improved analytical results in case of real-sample analysis when compared to previously reported methods. Graphical abstract Schematic illustration of DNA-silver nanoclusters and polypyrrole nanoparticles in an aptasensor for detection of multiple targets.

Finding efficient ways to prohibit abiotic and microbiologically influenced corrosion is a critical task for metal serving in harsh seawater environment. In this paper, originated from the biomimetics principle, a lotus leaf inspired superhydrophobic matrix composed by Fe-myristic acid compound is prepared on copper surface. The preparation is realized by a facile electrodeposition approach based on a coordination-deposition mechanism, which leads to porous structure composed of hydrophobic compound from an ethanol bath via a single step. The dependent relationship between wettability and electrodeposition conditions including electrodeposition potential and time is revealed. Sophisticated techniques including scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier Transform infrared spectroscopy are employed to characterize the matrix morphology and composition. Scanning Kelvin probe and other electrochemical methods show that superhydrophobic matrix improves the corrosion resistance capability of copper in different environments including atmosphere, natural seawater and salt spray, illustrating that superhydrophobic matrix endows high abiotic corrosion inhibition to the underneath Cu metal. The inhibition efficiency of Cu by superhydrophobic coating can reach 99.85 % after immersion in seawater for 28 days. For achieving high prohibition effect to the corrosion induced by microbes, the bio-adhesion inhibition is one prerequisite. The as-obtained superhydrophobic matrix is confirmed to prohibit the representative diatoms and sulfate reducing bacteria (SRB) to grow onto metal surface due to the limited anchoring sites and the low surface energy. Superhydrophobic matrix exhibits excellent corrosion resistance in harsh SRB suspension, demonstrating a prominent role to combat microbiologically influenced corrosion in seawater environment.

Introducing magnetic nanoparticles (MNP) into the enzyme@MOF complex is one of the most promising ways to facilitate enzyme recovery but typically hampered by its complex synthetic process and low loading rate. Using lipase as an example, herein, we reported a mild and quick one-pot strategy to achieve the successful encapsulation of lipase (CRL) and Fe3O4 nanoparticle into ZIF-8 to form CRL/MNP@ZIF-8 with 88.4 % immobilization yield. It is the first time that magnetic nanoparticles and lipase were simultaneously encapsulated in ZIF‐8 through the co‐precipitation approach. The resulting magnetic MOF composite demonstrated an excellent protective capability against harsh environments and could also simplify the complex downstream separation and recovery operations. Moreover, after five successive cycles of reuse to hydrolyze p-nitrophenyl acetate, the residual CRL/MNP@ZIF-8 still reserve 82 % activity, which can significantly reduce the processing cost and might be applicable in the industries in the future.

Flap endonuclease 1 (FEN1), a ubiquitous enzyme involved in DNA repair and replication, is overexpressed in highly proliferative cancer cells. FEN1 has been recognized as a promising diagnostic marker of cancers; however, very few analytical techniques have been developed for the convenient detection of FEN1. To realize the simplified quantification of FEN1, we developed a FEN1-responsive fluorescent nanoprobe based on DNA-silver nanoclusters (DNA-AgNCs). The nanoprobe was rationally designed with a double-flapped dumbbell conformation, where its 5′ flap was produced with DNA-AgNCs, and the 3′ flap was elongated by a guanine-rich enhancer sequence (GRS). Rigidified by the DNA scaffold, DNA-AgNCs and the GRS are in close proximity, resulting in high fluorescence because of the GRS-induced activation of DNA-AgNCs. Upon the addition of FEN1, the 5’ flap of the nanoprobe is cleaved due to the structure-specific endonuclease activity of FEN1. This cleavage released the DNA-AgNCs from the nanoprobe, broke the proximity between DNA-AgNCs and the GRS, and caused decreased fluorescence. This nanoprobe can be applied in the sensitive detection of FEN1 with a detection limit of 40 fM, and it showed high specificity for the monitoring of FEN1 in clinical samples. As the first attempt to develop biosensors targeting FEN1 based on DNA-AgNCs, this work provided a potent platform for monitoring FEN1 and screening FEN1 inhibitors.

In this paper, a novel turn-on fluorescence aptasensor has been designed for adenosine detection based on fluorescence resonance energy transfer (FRET) from single-stranded DNA labeled carbon dots (ssDNA-CDs) to aptamer modified gold nanoparticles (aptamer-AuNPs). In the absence of adenosine, the fluorescence of ssDNA-CDs was quenched by aptamer-AuNPs via the formation of an aptamer–ssDNA duplex. The introduced adenosine competed to displace ssDNA-CDs by specifically binding to the aptamer, resulting in the recovery of the quenched fluorescence of ssDNA-CDs. Under optimized conditions, the increase in fluorescence intensity was proportional to the concentration of adenosine with a linear range of 10–500 nM and allowed a limit of detection as low as 4.2 nM. In addition, this method was successfully applied to adenosine determination in human serum samples with satisfactory results.

The Microcystin-Leucine-Arginine (MC-LR) is the most toxic and widely distributed microcystin, which originates from cyanobacteria produced by water eutrophication. The MC-LR has deleterious effects on the aquatic lives and agriculture, and this highly toxic chemical could severely endanger human health when the polluted food was intaken. Therefore, the monitoring of MC-LR is of vital importance in the fields including environment, food, and public health. Utilizing the complementary base pairing between DNA molecules, DNA nanotechnology can realize the programmable and predictable regulation of DNA molecules. In analytical applications, DNA nanotechnology can be used to detect targets via target-induced conformation change and the nano-assemblies of nucleic acids. Compared with the conventional analytical technologies, DNA nanotechnology has the advantages of sensitive, versatile, and high potential in real-time and on-site applications. According to the molecular basis for recognizing MC-LR, the strategies of applying DNA nanotechnology in the MC-LR monitoring are divided into two categories in this review: DNA as a recognition element and DNA-assisted signal processing. This paper introduces state-of-the-art analytical methods for the detection of MC-LR based on DNA nanotechnology and provides critical perspectives on the challenges and development in this field.

S-Linked oligosaccharide/polysaccharide and glycoconjugates including glycolipid, glycoprotein, saponin and others, in which the glycosidic oxygen is replaced by a sulfur atom, have attracted considerable attention as probes in biological investigations, due to the higher metabolic stability compared to their natural saccharide counterparts. Furthermore, these resulting S-linked glycosides maintain or even show improved biological activity than their parent O-linked glycosides when bond to proteins and are tolerated in most biological systems. Therefore, this class of saccharides is widely used as valuable tools in various biological studies such as glycosidase inhibitors, antibacterial agents and antitumor drugs as well as ligands for the purification of proteins by affinity chromatography. However, to date, there are very limited reviews published about the summarization of the synthetic approaches towards S-linked sugars and glycoconjugates. In this review, we systematically examine the remarkable progress that has been made in the chemical and enzymatic synthesis of the thioglycosides in the past ten years, and discuss their pharmacological applications as well.

As promising sensory materials, metal–organic frameworks have been extensively studied; however, the development of fluorescent MOFs relies heavily on the complex organic ligands and lanthanide metal ions, which remains a challenge. To overcome this barrier, carbon dots@metal–organic frameworks (CD@MOF) have been proposed and developed. CD@MOF composites are newly emerging as fluorescent sensors due to their ease of synthesis, high selectivity and sensitivity to analytes. CD@MOF sensors combine the advantages of both CDs and MOFs, including excellent optical properties of CDs (such as tunable emission lights and photochemical stability) and high surface areas, tunable porosity, and designable functionalities of MOFs, resulting in enhanced sensing performance. This review focuses on recent progresses in the rational design and synthesis of CD@MOF sensors and their applications in sensing of metal ions, nitroaromatic compounds, water and humidity, temperature, biomarkers, and drugs. We also briefly discuss the present challenges and future research directions for CD@MOF sensors.

Zn coating is widely used for protecting building construction surfaces exposed to atmospheric conditions. Due to the intrinsic chemical reactivity of Zn, it can be corroded by adventitious environmentally present corrosive species. Finding an effective protecting approach is critical in order to extend the life of a zinc coating and the substrate metal. In this work, using a facile salt spraying method, a porous matrix is formed on a Zn surface. After modification with dodecanethiol, the as-prepared porous matrix exhibits superhydrophobicity with a large water contact angle (WCA) of 158°. An upgraded bio-inspired slippery surface with high water-repellency is achieved by filling the nanofluid (NF) composed by nanoscale Fe3O4 and oleic acid into the pores on Zn (NF Zn). Surprisingly, this coating exhibits a sustainable anti-corrosion capability. The characteristic impedance of NF Zn coating increases 6 orders of magnitude in 3.5 wt% and 7.0 wt% NaCl aqueous solution, and the corrosion current density (Icorr) decreases by 4 and 5 orders of magnitude, respectively. After the salt spray test for 21 days, it still has a good protection effect on metallic zinc. In an acidic environment, the characteristic impedance of NF Zn increases 5 orders of magnitude, and Icorr decreases 4 orders of magnitude than that of bare Zn, performing a good anti-corrosion effect. After immersion for 16 days, the low-frequency impedance and current density of NF Zn increase and decrease by 5 and 6 orders of magnitude, respectively. NF can be used as an anti-corrosion coating to protect Zn in different environments.

Transcription factors (TFs) are sequence-specific DNA binding proteins functioned as the key regulators of cell fate and progress. The association between TFs and their binding sites gated the initiation of gene transcription, further influencing the expression of proteins. TFs are recognized as important biomarkers for the indication of various diseases including cancers, virus infections, and autoimmune diseases. However, the lack of efficient methods for the detection of TFs has hindered its application in clinical fields for a long period. Recently, the rapid development of sensing techniques has motivated the innovations in developing sensors for in vivo and in vitro detections of TFs. Exploiting antibodies, peptides, DNA, molecular tags, and fluorescent probes, the current sensors can realize the detection of TFs with improved sensitivity, simplified workflow, and reduced cost. In this critical review, we summarized the achievements and challenges in the sensing of TFs, and provided perspective in this field.

The variation patterns of transcription factors (TFs) provide direct information for the states of cell populations, which is of significance for biomedical research and clinical diagnostics. Herein, we show that through multi-channeled isothermal amplification, it is feasible to connect DNA-based signal transduction with chromatography for multiplexed detection of TFs. The described system is referred to as "PAC" which includes three major steps: (i) Protection, which uses DNA-modified magnetic beads to capture TFs and converts the capturing event into triggering signal; (ii) Amplification, which receives the triggering signal and generate DNA reporters through multi-channeled extension and nicking of oligonucleotides; and (iii) Chromatography, which separates and detects the DNA reporters in liquid chromatography. The quantitative detection of five essential TFs includes p50, p53, AP-1, MITF, and c-Myc is realized in a multiplexed manner, with the lowest detection limit of 0.5 pM. PAC can also provide effective means to measure the above five TFs in real samples, including cultured cells, xenograft tumors, and blood-based liquid biopsy. This study not only established a solution for multiplexed measurement of TFs for molecular diagnostics, but also paved avenue for bridging the gap between DNA nanotechnology and chromatography.

BiOBr nanosheets are important photocatalytic nanomaterials. However, their biological effects remain to be explored. In this study, we investigated the antifungal effect of BiOBr nanosheets on Candida albicans. Strikingly, the nanosheets strongly inhibited the growth of C. albicans [IC50=(96±4.7) mg/L], hyphal development and biofilm formation. Compareed to the antifungal effect of the cationic surfactant cetyltrimethylammonium bromide, the inhibitory effect of the nanosheets on fungal pathogen was attributed to cetyltrimethylammonium bromide adsorbed by the nanosheets. Thermal gravity analysis and cetyltrimethylammonium bromide release experiment indicated that only 0.42% cetyltrimethylammonium bromide on BiOBr nanosheets was released. Taken together, this study uncovers the contribution of surfactant released from the nanosheets to their antifungal activity.

The well-known biorefractory organic material 1,4-Dioxane (1,4-D) is difficult to degrade in groundwater by classical treatment processes. The sono-activated persulfate process was applied ...

Sensitive and efficient detection of protein markers, such as transcription factors (TFs), is an important issue in postgenomic era. In this paper, we report a DNA nanodevice, allosteric DNA-silver nanocluster switches (AgSwitches), for TFs detection. The mechanism of this nanodevice is based on the binding-induced allostery whereby the binding between AgSwitches and TFs alters the conformation of AgSwitches. This alteration brings DNA-silver nanocluster (DNA-AgNCs) and guanine-rich enhancer sequences (GRS) into close proximity, generating fluorescent enhancement for quantifications. Our results revealed that the sequence design of AgSwitches can be rationally optimized according to stimulated free energy, and we demonstrated that this method can not only be used for detecting TFs in nuclear extracts of cells, but also be developed as a tool for screening inhibitors of TFs. Overall, this work expanded the category allosteric DNA nanodevices by first introducing DNA-AgNCs into this area, and the obtained method was efficient for TFs-related investigations.

A fluorometric ATP assay is described that makes use of carbon dots and graphene oxide along with toehold-mediated strand displacement reaction. In the absence of target, the fluorescence of carbon dots (with excitation/emission maxima at 360/447 nm) is strong and in the "on" state, because the signal probe hybridizes with the aptamer strand and cannot combine with graphene oxide. In the presence of ATP, it will bind to the aptamer and induce a strand displacement reaction. Consequently, the signal probe is released, the sensing strategy will change into the "off" state with the addition of graphene oxide. This aptasensor exhibits selective and sensitive response to ATP and has a 3.3 nM detection limit. Graphical abstract Schematic of signal amplification by strand displacement in a carbon dot based fluorometric assay for ATP. This strategy exhibits high sensitivity and selectivity with a detection limit as low as 3.3 nM.

Increasing attention has been paid to persulfate activation for the degradation of organic contaminants due to its high efficiency and low cost. However, most previous studies have overlooked the detection of generated reactive oxygen species (ROS), which plays an important role in the transformation of contaminants. In this study, the activation of persulfate by ultrasonic field (UF) for the degradation of 1,1,1-trichloroethane (TCA) and solvent stabilizer 1,4-dioxane (1,4-D), and the possible reaction mechanism were investigated. The results showed that the contaminants can be efficiently degraded under the optimal conditions of pH 0 = 7.0, Temp. 15 ± 2 °C, persulfate 1.50 mmol/L, ultrasonic frequency 400 kHz, power 100 W and ultrasonic density 2.67 W/cm 2 with initial TCA ∼20 mg/L and 1,4-D ∼1.0 mg/L. Coexisting 10 mmol/L inorganic anions slowed down the contaminant degradation to different degrees, and the inhibiting effect followed the order of CO 3 2− > HCO 3 − > Cl − > SO 4 2− > NO 3 − . The electron paramagnetic resonance (EPR) technique was used to detect and identify the ROS. Results show that the applied UF could effectively activate persulfate and produce more hydroxyl radicals ( OH) and sulfate radicals (SO 4 − ), accordingly resulting in the enhanced degradation of the contaminants. Twenty-three and eight degradation intermediates were detected and identified for TCA and 1,4-D, respectively. Results indicate that the sono-activated persulfate process is a promising technique to simultaneously eliminate of TCA and 1,4-D from water or groundwater.

In this paper, a facile and one-step hydrothermal carbonization approach has been developed for the first time to synthesize β-amino alcohol functionalized fluorescent carbon dots (CDs) with L-phenylalaninol as the sole precursor source. The present CDs with β-amino alcohol moieties attached to the surface were successfully applied to fabricate a novel, simple fluorescent sensing interface for selective detection of copper ions under basic conditions based on the biuret reaction. The added copper ions, not only lead to the specific cross-linked formation of the violet complex with the two β-amino alcohol units on the surface of the CDs, but also in turn lead to the aggregation of the functionalized CDs and induce fluorescence quenching. Such fluorescence responses can be used for monitoring copper ions in the range of 0.01–100 μmol L−1 under basic conditions with the limit of detection (LOD) as low as 3.2 nmol L−1. Moreover, the proposed fluorescent sensor can resist interferences from other metal ions and can be employed for the detection of copper ions in water samples. Due to the simplicity and effectiveness, it exhibits great promise as a practical sensing platform for copper ions especially under basic conditions.

Transcription factors (TFs) regulate gene expression by binding to regulatory regions, and their dysregulation is involved in numerous diseases. Thus, they are therapeutic targets and potential diagnostic markers. However, widely used methods for TFs detection are either cumbersome or costly. Herein, we first applied DNA-Ag nanoclusters molecular beacons (AgMBs) in TFs analysis and designed an assay based on the switchable fluorescence of AgMBs. In the absence of TFs, a single-stranded DNA functioned as a reporter is released from a double-stranded DNA probe (referred as dsTFs probe) under exonuclease III (Exo III) digestion. Then, the reporter triggers downstream Exo III-assisted signal amplification by continuously consuming the guanine-rich enhancer sequences in AgMBs, resulting in significant fluorescent decrease eventually. Conversely, the presence of TFs protects the dsTFs probe from digestion and blocks the downstream reaction to keep a highly fluorescent state. To testify this rationale, we utilized nuclear factor-kappa B p50 (NF-κB p50) as a model TFs. Owing to the amplification strategy, this method exhibited high sensitivity toward NF-κB p50 with a limit of detection of 10 pM, and a broad linear range from 30 pM to 1.5 nM. Furthermore, this method could detect multiple TFs in human colon cancer DLD-1 cells and reflect the variation in their cellular levels after stimulation. Finally, by conducting an inhibition assay we revealed the potential of this method for screening TFs-targeted drugs and calculating the IC

The removal of p -chloronitrobenzene ( p -ClNB) from contaminated groundwater of certain chemical relocated site was explored by a heterogeneous nanoparticulate zero-valent iron (NZVI)-induced Fenton process. The effects of various factors, including hydrogen peroxide (H 2 O 2 ), NZVI dose, and initial pH of groundwater as well as the common components in groundwater such as Cl − , NO 3 − and SO 4 2− were evaluated. The results showed that p -ClNB can be completely degraded within 30 min at pH 3.0 and 30 °C with NZVI 268.8 mg/L, H 2 O 2 4.90 mmol/L and initial p -ClNB 60 mg/L, indicating the effectiveness of the NZVI-induced Fenton process for the p -ClNB removal. The p -ClNB degradation was fitted with a pseudo-first-order kinetic model, and the rate constants were found to increase with the increasing NZVI dose (0–358 mg/L) and H 2 O 2 dose (0–4.90 mmol/L). Acid conditions were favorable to the p -ClNB removal and elevating the initial groundwater pH (3.0–11.0) decreased the p -ClNB degradation rate. SO 4 2− anions had negative effects on p -ClNB removal, whereas the effects of Cl − and NO 3 − were negligible. On the other hand, the degradation intermediates, carboxylic acids and chloride ion during the reaction process were detected by gas chromatograph/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (HPLC/MS) and ion chromatography (IC). With these findings, a degradation pathway of p -ClNB was accordingly proposed. In conclusion, the NZVI-induced Fenton process is a highly promising remediation technique for groundwater contaminated by p -ClNB, but more complex components in groundwater should be carefully considered for its practical application.

Deposits formed on super-heater tubes decrease the heat transfer. Deposits may also cause corrosion of tube material. In kraft recovery boiler furnaces, the alkali-rich deposits are molten, and flow down along the super-heater tubes. In this work, a sub model which calculates the structure of a slag flow is implemented into a CFD model for super-heater tube sections. Specifically, it is applied to two tube bends on one of the first group of tube banks exposed to the flue gas. By taking into account deposition by inertial impaction, assuming all depositing particles fully molten and the steam temperature in super-heater constant, the slag model can provide thickness and surface temperature distributions of the flowing deposit layer. Furthermore, the thickness of solid deposit layer in contact with the tube and the temperature at the tube surface can be calculated. The local temperature at tube surface can be useful for choosing tube material.

Chlorinated solvents are the most prevalent organic contaminants in groundwater because of their extensive and widespread use as cleaning agents and metal degreasers, and they have become a significant threat to groundwater supplies. Groundwater contamination by chlorinated solvents has proven difficult and costly to remedy because of the physicochemical properties of the solvents. This study was conducted to examine the effectiveness of treating contaminated groundwater containing chlorinated solvents using air stripping, advanced oxidation, and activated carbon adsorption processes. The results showed that the stripping instrument could effectively transfer chlorinated solvents into the gas phase within several minutes at an airflow rate of 5.0 L/min and a temperature of 298 K. The residual chlorinated solvents were further oxidized into harmless by-products by the subsequent O3/H2O2 process, and the off-gas generated from the previously-mentioned processes were collected and absorbed by four t...

Total nitrogen (N) concentration (N%), N derived from 15N-fertilizer (Ndff%), amount of 15N uptake (ANU) in main organs (leaves, shoots, roots, fruits), and N use efficiency (NUE) were measured to assess N absorption, distribution, and utilization of Red Fuji apple trees across two years using a 15N-enriched urea method. The N% in leaves and fruits decreased while those in shoots and roots increased in both years. The Ndff% and ANU in roots were highest at fruitlet stage than those in leaves, shoots and fruits at mature stages. This suggested that the absorbed 15N by roots was redistributed to new organs. The N% was lower while Ndff% and ANU were greater in 2008 than 2007. The most 15N absorbed was accumulated in the trunks, main and coarse roots and smaller in the fine roots and biennial branches. The NUE in 2007 and 2008 reached 9.9% and 12.2% respectively.

This study investigated the enhancement of synergetic degradation of Fe/Cu/C (Fe: commercial iron, Cu: solid product of Fe reacted with CuSO4, C: carbon powder) for simulated groundwater contaminated by trichloroethylene (TCE). Zero valent iron (ZVI) as a reducing agent was proved to be effective for TCE removal. The Fe/Cu/C system resulted in higher reduction efficiency as a result of the synergetic role of Fe/Cu and Fe/C microelectrode than the Fe (ZVI) or Fe/Cu system, and the half-life was only about 0.4 h. When m(Fe) achieved 12.5 g L–1, the residual concentration of TCE almost leveled off. Fe:Cu = 10:1 or m(C) = 0.0086 g can induce the optimum function for TCE degradation. A neutral condition was appropriate for TCE degradation, and an acidic system slightly favored TCE dechlorination compared with an alkaline system. GC/MS analysis indicated that TCE was dechlorinated to 1,1-dichloroethene (1,1-DCE), cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC), and 1,1-DCE might be the precursor. Fe/Cu/C reduction is a highly promising technique for TCE removal, and it is an excellent alternative to enhance TCE reductive dechlorination.