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Here, the facile strategy of preparing filamentous copper phthalocyanine (CuPc) based gas sensors using a solution method was studied. Electrical and gas sensitive properties of filamentous CuPc films transistors were studied in detail. The filamentous CuPc films had a three-dimensional and porous structure, the gas analytes could interact more effectively with the gas sensitive layers, and the efficiency of charge carrier conversion into conductive channel increased, thus improving the sensing performance of the sensors. The relative responsivities of 75 mg mL−1 filamentous CuPc films sensors to 20 ppm NO2 gas were 32797%. The response rate was 80%. The sensitivity was 1492%/ppm. The LOD was 0.3 ppm. The successful preparation of filamentous CuPc films and their application in sensors lay a foundation for the future application of phthalocyanine materials in the field of flexible sensing. [ABSTRACT FROM AUTHOR]

The overuse of fipronil (FPN, a broad-spectrum insecticide) in agriculture has brought great concerns for environmental pollution and food safety. The development of a rapid, reliable, and portable analytical method for the on-site monitoring of FPN is therefore of great significance but is full of challenge. Herein, a novel supramolecular probe using human serum albumin (HSA) as the host and an aggregation-induced emission-active fluorescence probe LIQ-TPA-TZ as the guest was developed for the colorimetric and ratiometric detection of FPN, displaying fast response (30 s), high sensitivity (LOD ∼ 0.05 μM), and good selectivity and anti-interference performance. Moreover, portable paper-based test strips could be facilely obtained and utilized for the determination of FPN, showing colorimetric changes from yellow to orange. This supramolecular probe also demonstrated great potential in real applications for choosing the best cleaning method to reduce the residue rate of FPN on apples. This study provides a versatile tool for the fast and real-time analysis of FPN, which greatly benefits the on-site determination of pesticides with the use of simple testing apparatus. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are not only important electronic functional materials, but also considered as the most promising intelligent basic materials, because they show good application prospects. Therefore, it is an urgent task to develop and explore new ferroelectric material systems. In addition, the most important feature of crown ethers is their ability to complex with positive ions, which is extremely useful in synthesis. We report that [NH3C2H4Cl(18-crown-6)](CF3SO3) (1) has a phase transition temperature Tc = 255 K, and there is an obvious SHG switch below Tc. At the same time, the saturation polarization value Ps = 1.25 μC cm−2 is obtained from the hysteresis loop, which directly proves the ferroelectric nature of compound 1. It is noteworthy that the second harmonic response test of compound 1 shows a symmetric transition from a non-centrosymmetric to a centrosymmetric point group, that is a symmetry break from the paraelectric phase to the ferroelectric phase. This work is expected to promote the further exploration of organic crown ether ferroelectrics and provide a way to design and synthesize organic crown ether ferroelectrics. [ABSTRACT FROM AUTHOR]

We develop a new strategy for single-molecule monitoring of telomerase based on proximity ligation-transcription circuit-powered exponential amplifications. This strategy exhibits high sensitivity with a detection limit of 0.1 aM for the synthetic telomerase product TPC4 in vitro and 1 HeLa cell in vivo. Moreover, it can screen potential inhibitors, discriminate telomerase from interferents, and distinguish cancer cells from normal cells. [ABSTRACT FROM AUTHOR]

An Rh-catalyzed tandem reaction was performed to construct an AIE-active furo[2,3-c]pyridine-based photosensitizer, named LIQ-TF. LIQ-TF showed near-infrared emission with high quantum yield, and high 1O2 and ˙OH generation efficiency, and could be used for specific imaging and photodynamic ablation of Gram-positive bacteria in vitro and in vivo, showing great potential for combating multiple drug-resistant bacteria. [ABSTRACT FROM AUTHOR]

We develop a new fluorescence method for the sensitive detection of protein tyrosine phosphatase 1B (PTP1B) based on dephosphorylation-directed tricyclic DNA amplification cascades. This method exhibits good specificity and high sensitivity with a detection limit of 0.24 pM. Moreover, it can be applied for kinetics analysis, inhibitor screening, and the accurate detection of PTP1B in a variety of cancer cells. [ABSTRACT FROM AUTHOR]

Three 9-substituted acridines, namely 9-carboxyacridine (CA), 9-methylacridine (MA), and 9-aminoacridine (AA), were designed and synthesized for the development of effective inhibitors for mild steel corrosion in a 15% HCl solution. The corrosion-resistance ability was tested by weight-loss tests, electrochemical techniques, surface-topography analyses (SEM, SECM, and XPS), and contact angle measurements. The results indicated the inhibition performance followed the order of η(AA) > η(MA) > η(CA), and these acridines acted as mixed type inhibitors with a predominant restrained cathode process. The adsorption of the three acridines on a mild steel surface obeyed the Langmuir adsorption isotherm and involved both physisorption and chemisorption modes. Surface analysis and characterization confirmed the existence of an adsorbed film. Quantum chemical calculations were performed to provide mechanistic insights into the roles of the different substituents (−COOH, −CH3, and −NH2) on the corrosion-inhibition behavior of the three acridines. Molecular dynamics (MD) simulations were carried out to explore the configurational adsorption behavior of these 9-substituted acridines on the Fe(110) surface. [ABSTRACT FROM AUTHOR]

Single nucleotide polymorphisms (SNPs) have been proven to be important biomarkers for disease diagnosis, prognosis and disease pathogenesis. Here, taking the advantages of a self-assembled oligonucleotide sandwich structure and robust chemical reactions, we have developed a simple, high-throughput and effective colorimetric analytical technique termed CuAAC-based ligation-assisted assays (CuAAC-LA) for SNP detection using a DNA-BIND 96-well plate. With the 5′-azide and 3′-alkyne groups labelled on two oligonucleotide probes, the target DNA can direct a Cu(I)-catalyzed alkyne–azide cycloaddition (CuAAC) click reaction. Since the small difference in duplex stability caused by a single-nucleotide mismatch was amplified by the steric effects of these reactive groups for the ligation reaction of an unstable duplex, CuAAC-LA exhibited an ultra-sensitive discrimination ability for a mutant type target in the presence of large amounts of wild type targets. As low as 0.05% SNP could be clearly detected, which was better than most previously reported methods by various DNA ligases, indicating that a simple and rapid synthetic method i.e., the DNA template-directed click reaction held the potential to replace the ligase for SNP detection. [ABSTRACT FROM AUTHOR]

Herein, the synergistic effect of 1-(2,5-dioxoimidazolidin-4-yl)urea (DMU) and Tween-80 on the corrosion of mild steel in a 1 mol L−1 HCl solution was investigated by weight-loss tests, electrochemical methods and surface analysis (SEM/SECM). The experiments revealed that the combination of DMU and Tween-80 strongly inhibited the corrosion of mild steel as compared to individual inhibitors, and the adsorption mode belonged to the Langmuir isothermal type. Based on the electrochemical results, DMU and DMU–Tween-80 behaved as mixed-type inhibitors, and their best inhibition efficiencies were 77.31% and 96.35%, respectively. The calculated synergistic parameter value was larger than unity, indicating that the enhancement of inhibition efficiency was due to the synergistic effect of DMU and Tween-80. Surface analysis techniques confirmed the presence of inhibitors on the mild steel surface. Quantum chemical parameters based on density functional theory provided a further insight into the mechanism of inhibition. Moreover, molecular dynamics simulations were carried out to explore the configurational adsorption behaviour of DMU on an Fe(110) surface. [ABSTRACT FROM AUTHOR]

The inhibition performance of three pyrido[1,2-a]benzimidazoles, namely, benzo[4,5]imidazo[1,2-a]pyridine (BIP), 2-methylbenzo[4,5]imidazo[1,2-a]pyridine (MBIP), and 2-(trifluoromethyl)benzo[4,5]imidazo[1,2-a]pyridine (TBIP), for steel corrosion in hydrochloric acid solution were researched through a weight loss test, electrochemical techniques, surface morphology (SEM, XPS) studies, and theoretical methods. The experimental results revealed that TBIP, BIP, and MBIP had excellent inhibition performance, and their maximum inhibition efficiencies at 0.25 mmol L−1 were 95.48%, 97.65%, and 98.96%, respectively. The properties of these inhibitors are considered to be mixed-type, and their adsorption mode belongs to the Langmuir isothermal type. The formation and properties of an adsorbed film on a steel surface were investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Quantum chemical calculations provided insightful quantitative information to conclude the correlation between the molecular structures and inhibition performance. Molecular dynamics (MD) simulations were carried out to explore the configurationally adsorption behavior of these pyrido[1,2-a]benzimidazoles on Fe(110) surface, and the binding energy of these three inhibitors followed the order MBIP ＞ BIP ＞ TBIP, which is consistent with the experimental evaluation results. [ABSTRACT FROM AUTHOR]

DNA methyltransferase (MTase) is an important epigenetic modification enzyme responsible for DNA methylation, and the dysregulation of DNA MTase activity is associated with various diseases in humans. Herein, we take advantage of the DNA lesion repair mechanism in vivo to develop a new fluorescence approach for the specific and sensitive detection of DNA methyltransferase (DNA MTase) on the basis of the DNA lesion repair-directed cascade isothermal amplification. Due to the high amplification efficiency of the uracil repair-mediated exponential isothermal amplification reaction (EXPAR), the efficient cleavage of endonuclease IV (Endo IV)-induced cyclic catalysis, and the low background signal caused by single uracil repair-mediated inhibition of nonspecific amplification, this approach exhibits high sensitivity with a detection limit of 0.014 U mL−1 for pure Dam MTase and 0.61 × 10−6 mg mL−1 for Dam MTase in E. coli cells and it can be further applied for the screening of DNA MTase inhibitors. More importantly, this approach can be applied to detect other DNA MTases by designing appropriate substrates, showing great potential in biomedical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Alkaline phosphatase (ALP) is an important diagnostic indicator for various human diseases including bone diseases, liver dysfunction, diabetes, breast and prostatic cancers. However, the conventional methods for ALP assay are usually cumbersome and time-consuming with low sensitivity. Here, we develop a new fluorescent method for ultrasensitive detection of ALP activity on the basis of primer dephosphorylation-initiated isothermal circular exponential amplification. We design two dual-functional hairpin probes (HP1 and HP2), which function as both the templates for exponential amplification reaction (EXPAR) and the generators for signal output. In the presence of ALP, the 3′-phosphorylated primer is dephosphorylated and subsequently hybridizes with the 3′ protruding end of HP1 to initiate the first strand displacement amplification (SDA), producing trigger 1 and fluorescence signal. The released trigger 1 is complementary to the 3′ protruding end of HP2 for the initiation of the second SDA, producing trigger 2 and fluorescence signal. Notably, trigger 2 is complementary to the 3′ protruding end of HP1 and may subsequently initiate two consecutive SDAs, enabling circular EXPAR to generate an amplified fluorescence signal. This method exhibits high sensitivity with a detection limit of 2.0 × 10−10 U μL−1 and a large dynamic range of 5 orders of magnitude from 1.0 × 10−9 to 1.0 × 10−4 U μL−1, and it can measure ALP at the single-cell level. Importantly, this method can be applied for the measurement of kinetic parameters and the screening of potential inhibitors, providing a powerful tool for ALP-related biomedical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

We developed a simple and rapid method for terminal deoxynucleotidyl transferase (TdT) assay on the basis of the polymerization-directed exonuclease-assisted construction of a single quantum dot (QD)-based fluorescence resonance energy transfer (FRET) nanosensor. This method is very sensitive with a detection limit as low as 1 × 10−6 U μL−1, and it can be used for the screening of TDT inhibitors and accurate quantification of TdT activity even in 5 cancer cells. [ABSTRACT FROM AUTHOR]

We develop a new fluorescence method for real-time monitoring of thymine DNA glycosylase (TDG) activity through cyclic enzymatic repairing-mediated dual-signal amplification. This method exhibits excellent sensitivity with a detection limit of 5.6 × 10−7 U μL−1, and it can be used to determine kinetic parameters and quantify TDG activity from even single cancer cells. [ABSTRACT FROM AUTHOR]

A telomere-triggered isothermal exponential amplification-based DNAzyme biosensor is developed for highly sensitive detection of telomerase in cancer cells even at the single-cell level. This biosensor can be further applied for the screening of telomerase inhibitors for anticancer drug development. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are not only important electronic functional materials, but also considered as the most promising intelligent basic materials, because they show good application prospects. Therefore, it is an urgent task to develop and explore new ferroelectric material systems. In addition, the most important feature of crown ethers is their ability to complex with positive ions, which is extremely useful in synthesis. We report that [NH 3 C 2 H 4 Cl(18-crown-6)](CF 3 SO 3 ) (1) has a phase transition temperature T c = 255 K, and there is an obvious SHG switch below T c . At the same time, the saturation polarization value P s = 1.25 μC cm -2 is obtained from the hysteresis loop, which directly proves the ferroelectric nature of compound 1. It is noteworthy that the second harmonic response test of compound 1 shows a symmetric transition from a non-centrosymmetric to a centrosymmetric point group, that is a symmetry break from the paraelectric phase to the ferroelectric phase. This work is expected to promote the further exploration of organic crown ether ferroelectrics and provide a way to design and synthesize organic crown ether ferroelectrics.

An Rh-catalyzed tandem reaction was performed to construct an AIE-active furo[2,3- c ]pyridine-based photosensitizer, named LIQ-TF. LIQ-TF showed near-infrared emission with high quantum yield, and high 1 O 2 and ˙OH generation efficiency, and could be used for specific imaging and photodynamic ablation of Gram-positive bacteria in vitro and in vivo , showing great potential for combating multiple drug-resistant bacteria.

The eye is a complex structure with a variety of anatomical barriers and clearance mechanisms, so the provision of safe and effective ophthalmic drug delivery technology is a major challenge. In the past few decades, a number of reports have shown that nano-delivery platforms based on polymeric micelles are of great interest, because of their hydrophobic core that encapsulates lipid-soluble drugs and small size with high penetration, allowing long-term drug retention and posterior penetration in the eye. Furthermore, as an ocular delivery platform, polymeric micelles not only cover the single micellar drug delivery system formed by poloxamer, chitosan or other polymers, but also include composite drug delivery systems like micelle-encapsulated hydrogels and micelle-embedded contact lenses. In this review, a number of ophthalmic micelles that have emerged in the last three years will be systematically reviewed, with a summary of and discussion on their unique advantages or unique drug delivery performance. Last but not least, the current challenges of polymeric micelle formulations in potential clinical ophthalmic therapeutic applications will also be proposed, which might be helpful for future design of ocular drug delivery formulations., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Single nucleotide polymorphisms (SNPs) have been proven to be important biomarkers for disease diagnosis, prognosis and disease pathogenesis. Here, taking the advantages of a self-assembled oligonucleotide sandwich structure and robust chemical reactions, we have developed a simple, high-throughput and effective colorimetric analytical technique termed CuAAC-based ligation-assisted assays (CuAAC-LA) for SNP detection using a DNA-BIND 96-well plate. With the 5'-azide and 3'-alkyne groups labelled on two oligonucleotide probes, the target DNA can direct a Cu(i)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction. Since the small difference in duplex stability caused by a single-nucleotide mismatch was amplified by the steric effects of these reactive groups for the ligation reaction of an unstable duplex, CuAAC-LA exhibited an ultra-sensitive discrimination ability for a mutant type target in the presence of large amounts of wild type targets. As low as 0.05% SNP could be clearly detected, which was better than most previously reported methods by various DNA ligases, indicating that a simple and rapid synthetic method i.e., the DNA template-directed click reaction held the potential to replace the ligase for SNP detection.

Genomic DNA damage and repair are involved in multiple fundamental biological processes, including metabolism, disease, and aging. Inspired by the natural repair mechanism in vivo , we demonstrate for the first time the construction of a self-directed replication system for label-free and real-time sensing of repair glycosylases with zero background. The presence of DNA glycosylase can catalyze the excision repair of the damaged base, successively autostarting the self-directed replication through recycling polymerization extension and strand-displacement DNA synthesis for the generation of exponentially amplified dsDNAs. The resultant dsDNA products can be label-free and real-time monitored with SYBR Green I as the fluorescent indicator. Owing to the high efficiency of self-directed exponential replication and the absolute zero background resulting from the efficient inhibition of nonspecific amplification induced by multiple primer-dependent amplification, this strategy exhibits high sensitivity with a detection limit of 1 × 10 -8 U μL -1 in vitro and 1 cell in vivo , and it can be further used to screen inhibitors, quantify DNA glycosylase from diverse cancer cells, and even monitor various repair enzymes by simply changing the specific damaged base in the DNA template. Importantly, this assay can be performed in a label-free, real-time and isothermal manner with the involvement of only a single type of polymerase, providing a simple, robust and universal platform for repair enzyme-related biomedical research and clinical therapeutics., (This journal is © The Royal Society of Chemistry 2020.)

DNA methylation is an important epigenetic modification in human genomes. Herein, we develop a single quantum dot (QD)-based nanosensor for sensitive detection of DNA methylation at both CpG and non-CpG sites using tricyclic ligation chain reaction (LCR)-mediated QD-based fluorescence resonance energy transfer (FRET). We design two sets of DNA probes (X and Y, X' and Y') for methylated DNA assay. In the presence of thermostable DNA ligase, probes X and Y may adjacently hybridize with the methylated DNA to obtain the ligated XY products which may function as the templates for probes X' and Y' to generate the X'Y' products. The resultant X'Y' products may in turn act as the templates to ligate probes X and Y for the generation of XY products, consequently inducing tricyclic LCR amplification under thermal denaturation conditions to generate a large number of XY products. The subsequent hybridization of XY products with the capture and reporter probes results in the formation of sandwich hybrids which may assemble on the 605QD surface to obtain 605QD-oligonucleotide-Cy5 nanostructures, inducing efficient FRET from the 605QD to Cy5 and the emission of Cy5. This nanosensor can detect DNA methylation at single 5-methylcytosine (5-mC) resolution with a detection limit of as low as 1.0 aM and a large dynamic range of 7 orders of magnitude. Moreover, this nanosensor can distinguish as low as a 0.01% methylation level, and it can detect DNA methylation in human lung cancer cells as well, holding great potential for accurate epigenetic evaluation and early cancer diagnosis.

We develop a new method for ultrasensitive detection of folate receptors (FRs) using a target-triggered isothermally exponential amplification reaction (EXPAR)-based DNAzyme biosensor. This method exhibits excellent specificity and high sensitivity with a detection limit as low as 0.23 fM and a large dynamic range of 6 orders of magnitude from 1 fM to 1 nM. It might be further applied for the detection of various small molecule-binding proteins by simply changing the linked small molecule moiety of the hairpin probes.

Soy lipophilic protein nanoparticles (LPP), which present a novel delivery vehicle for conjugated linoleic acid (CLA), were fabricated by ultrasonication of the soy lipophilic protein (LP), which exhibits unique characteristics including a high loading capacity, oxidation protection and a sustained releasing profile in vitro for CLA. The CLA-loaded LPP exhibited a mean diameter of 170 ± 0.63 nm and a loading capacity of 26.3 ± 0.40% (w/w). A coating of sodium caseinate (SC) on the surface improved the colloidal stability of the CLA-loaded LPP. This encapsulation conferred protection against the oxidation of CLA, by which the head space-oxygen consumption and hydrogen peroxide value were obviously decreased in comparison with the SC-encapsulated CLA and CLA alone. The delivery system enables a sustained releasing profile of CLA in a simulated gastrointestinal tract (GIT). These findings illustrate that the LPP could act as an effective delivery device for CLA, which could provide oxidation stability and a sustained release property.

A carbonyl reductase gene (yueD) from Bacillus sp. ECU0013 was heterologously overexpressed in Escherichia coli, and the encoded protein (BYueD) was purified to homogeneity and characterized. The NADPH-dependent reductase showed a broad substrate spectrum towards different aromatic ketones, and α- and β-ketoesters. Although the enantioselectivity was high to moderate for the reduction of α-ketoesters, all the tested β-ketoesters and aromatic ketones were reduced to the corresponding chiral alcohols in enantiomerically pure forms. Furthermore, the practical applicability of this enzyme was evaluated for the reduction of ethyl 4-chloro-3-oxobutanoate (1a). Using Escherichia coli cells coexpressing BYueD and glucose dehydrogenase, 215 g L(-1) (1.3 M) of 1a was stoichiometrically converted to ethyl (R)-4-chloro-3-hydroxybutanoate ((R)-1b) in an aqueous-toluene biphasic system by using a substrate fed-batch strategy, resulting in an overall hydroxyl product yield of 91.7% with enantiomeric purity of 99.6% ee.