A novel multimode biosensor for sensitive detection of AFB1 in food based on Mxenes nano enzymes

In this work, Ti₃C₂ nano-enzymes (Ti₃C₂ NEs) materials with simulated peroxidase activity and fluorescence quenching properties were prepared. Then Ti₃C₂ NEs was functionalized using 6-carboxyfluorescein (FAM) labeled Aflatoxin B₁ (AFB₁) aptamers to construct a novel multimode nano enzyme biosensor for the detection of AFB₁ in peanuts. Based on the fluorescence quenching characteristics and the superior simulated peroxidase activity of Ti₃C₂ NE_S and the specific binding of the aptamer to AFB₁, the sensitive and rapid fluorescence/colorimetric/smart phone detection of AFB₁ have been achieved, with detection limits of 0.09 ng mL^-1, 0.61 ng mL^-1 and 0.96 ng mL^-1, respectively. The analytical method provided can not only detect AFB₁ in multiple modes, but also has a wider detection range, lower limit of detection (LOD) and better recovery rate, and can achieve on-site accurate detection of AFB₁ content in peanuts, which has great application potential in the field of food quality testing.

Fluorescent microsphere-based lateral-flow immunoassay for rapid and sensitive determination of eugenols

In this study, a sensitive monoclonal antibody (mAb) 1B5 against eugenols was prepared based on a novel hapten. Based on this mAb, a paper-based lateral-flow immunoassay (LFIA) was developed using Eu-fluorescent microspheres sensor, that could achieve qualitative and quantitative detection of eugenols within 10 min. Results showed colorimetric values observed by the naked eye were 12.3 µg/kg, 12.3 µg/kg, 37 µg/kg and 111 µg/kg for eugenol, isoeugenol, methyl eugenol, and methyl isoeugenol, respectively, in both water and fish samples. For quantitative detection of eugenol, isoeugenol, methyl eugenol and methyl isoeugenol, the detection ranges were 4.49-48.4 µg/kg, 6.02-66.8 µg/kg, 16.5-150 µg/kg and 47.9-710 µg/kg in water, and 3.9-30.9 µg/kg, 5.9-62.6 µg/kg, 16.7-255 µg/kg, and 44.5-890 µg/kg in fish, respectively. The recovery test and detection in fish demonstrated the reliability of the LFIA in real samples. Therefore, the developed LFIA produced a promising alternative tool for the rapid on-site detection of eugenols.

Highly sensitive and stable fluorescent aptasensor based on an exonuclease III-assisted amplification strategy for ATP detection

Fluctuations in intracellular adenosine triphosphate (ATP) concentration are closely associated with some cancer diseases. Thus, it is a worthwhile undertaking to predict sickness by monitoring changes in ATP levels. However, the detection limits of current fluorescent aptamer sensors for ATP detection are in the range of nmol L^-1 to μmol L^-1. It has become crucial to employ amplification strategies to increase the sensitivity of fluorescent aptamer sensors. In the current paper, a duplex hybrid aptamer probe was developed based on exonuclease III (Exo III)-catalyzed target recycling amplification for ATP detection. The target ATP forced the duplex probe configuration to change into a molecular beacon that can be hydrolyzed with Exo III to achieve the target ATP cycling to amplify the fluorescence signal. Significantly, many researchers ignore that FAM is a pH-sensitive fluorophore, leading to the fluorescence instability of FAM-modified probes in different pH buffers. The negatively charged ions on the surface of AuNPs were replaced by new ligands bis(p-sulfonatophenyl)phenylphosphine dihydrate dipotassium salt (BSPP) to improve the drawback of FAM instability in alkaline solutions in this work. The aptamer probe was designed to eliminate the interference of other similar small molecules, showing specific selectivity and providing ultra-sensitive detection of ATP with detection limits (3σ) as low as 3.35 nM. Such detection limit exhibited about 4-500-fold better than that of the other amplification strategies for ATP detection. Thus, a relatively general high sensitivity detection system can be established according to the wide target adaptability of aptamers, which can form specific binding with different types of targets.

Development of ratiometric fluorescent probes based on peptides for sensing Pb2+ in aquatic environments and human serum

The detection of Pb²⁺ ions in aquatic environments and biofluid samples is crucial for assessment of human health. Herein, we synthesized two fluorescent probes (1 and 2) consisting of the peptide receptor for Pb²⁺ and a benzothiazolyl-cyanovinylene fluorophore that exhibited excimer-like emission when it aggregated. The peptide-based probes sensitively detected Pb²⁺ in purely aqueous solution (1% DMF) through ratiometric fluorescent response with a decrease in monomer emission at 520 nm and an increase in excimer emission at 570 nm. Specially, probe 2 showed remarkable detection features such as high selectivity for Pb²⁺over 15 metal ions, high binding affinity (K_d = 5.83 × 10^-7 M) for Pb²⁺, significant emission intensity changes, low detection limit (3.8 nM) of Pb²⁺, high water solubility, and visible light excitation (450 nm). Probe 2 was successfully used to quantify nanomolar concentration (0 ∼ 800 nM) of Pb²⁺ in real water samples (ground water and tap water). Specially, 2 was successfully applied for the quantification of Pb²⁺ in human serum by combination of microwave-assisted human serum digestion and filtration of digested serum by anion exchange cartridge. We clearly investigated the binding mode of 2 with Pb²⁺ using ¹H NMR, IR spectroscopy, pH titration, confocal microscopy, and size analysis. The peptide-based fluorescent probe might have great application potential for sensing Pb²⁺ in aquatic environments and biofluid samples.

Genetically encoded fluorescent sensors for metals in biology

Metal ions intersect a wide range of biological processes. Some metal ions are essential and hence absolutely required for the growth and health of an organism, others are toxic and there is great interest in understanding mechanisms of toxicity. Genetically encoded fluorescent sensors are powerful tools that enable the visualization, quantification, and tracking of dynamics of metal ions in biological systems. Here, we review recent advances in the development of genetically encoded fluorescent sensors for metal ions. We broadly focus on 5 classes of sensors: single fluorescent protein, FRET-based, chemigenetic, DNAzymes, and RNA-based. We highlight recent developments in the past few years and where these developments stand concerning the rest of the field.

Development of a fluorescent probe based on a tricyano structure for the detection of PhSH in environmental and biological samples

In this study, a NIR fluorescent probe based on ICT principles was developed for the detection of phenylthiophenol. An excellent fluorescent mother nucleus is constructed with tricyano groups, and benzenesulfonate was introduced as a specific recognition site for thiophene, which can be used for rapid detection of thiophenol. The probe has a significant Stokes shift (220 nm). Meanwhile, it had rapid response to thiophene and high specificity. The fluorescence intensity of the probe at 700 nm showed a good linear relationship with thiophene concentration in the range of 0 to 100 μM, and the detection limit was as low as 45 nM. The probe had also been successfully applied to the detection of thiophene in real water samples. MTT assay showed low cytotoxicity and excellent fluorescence imaging in live cells.

Domino protocol for the synthesis of diversely functionalized derivatives of a novel fused pentacyclic antioxidant/anticancer fluorescent scaffold: Pyrazolo[5'',1'':2',3']pyrimido[4',5':5,6][1,4]thiazino[2,3-b]quinoxaline

Rising to the challenge of formidable multi-step reaction needed for the synthesis of polycyclic compounds, an efficient one-pot two-step procedure for the synthesis of densely functionalized novel pyrazolo[5″,1'':2',3']pyrimido[4',5':5,6] [1,4]thiazino[2,3-b]quinoxalines from synthetically accessible starting materials 6-bromo-7-chloro-3-cyano-2-(ethylthio)-5-methylpyrazolo[1,5-a]pyrimidine, 3-aminoquinoxaline-2-thiol and some readily accessible alkyl halides was established. The domino reaction pathway involves cyclocondensation/N-alkylation sequence in K₂CO₃/N,N-dimethyl formamide under heating condition. DPPH free radical scavenging activity of all synthesized pyrazolo[5″,1'':2',3']pyrimido[4',5':5,6][1,4]thiazino[2,3-b]quinoxalines was evaluated to determine their antioxidant potentials. IC₅₀ values were recorded in the range of 29-71 μM. N-benzyl substituted derivative represented the most effective antioxidant activity as well as antiproliferative activity against MCF-7 cells. Moreover, fluorescence in solution for these compounds exhibited strong red emission in the visible region (λ_flu. = 536-558 nm) with good to excellent quantum yields (61-95%). Due to their interesting fluorescence properties, these novel pentacyclic fluorophores can be used as fluorescent markers and probes for studies in biochemistry and pharmacology.

Synthesis and application of fluorescent N-doped carbon dots/hydrogel composite for Cr(VI) adsorption: Uncovering the ion species transformation and fluorescent quenching mechanism

A fluorescent composite material fabricated from nitrogen-doped carbon dots with polyvinyl alcohol (PVA)/polyvinylpyrrolidone (PVP)/citric acid (CA) hydrogel was synthesized using a microwave-assisted hydrothermal method. The composite was used as a metal ion sensor and adsorbent to remove chromium (Cr(VI)) from water. The chemical structure and Cr(VI) removal performance of the fluorescent composite films were also characterized. Fluorescent quenching upon Cr(VI) adsorption showed that Cr(VI) binding was attributed to the N-doped carbon dots. The results were confirmed by several analytical techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS). The mechanism of Cr(VI) removal from water by the fluorescent composite film was based on the adsorption and subsequent reduction of N-doped carbon dots within the 3D porous composite film. XPS measurements showed that 53.2% Cr(III) and 46.8% Cr(VI) were present on the composite surface after Cr(VI) adsorption. Moreover, XAS revealed a change in the oxidation state of Cr(VI) to Cr(III) after adsorption and in the Cr-O bond length (1.686 Å to 2.284 Å) after reduction. The Cr(VI) adsorption capacity of the composite film was 4.90 mg g^-1 at pH 4 and fit the pseudo-second-order kinetic and Freundlich models. The results of this study could be used as a platform to further apply CDs/HD composites to remove Cr(VI) from water sources.

An amphiphilic macrocyclic acylhydrazone dimer: Facile synthesis and dual channel detection and removal of phthalate anion

Despite the large number of dicarboxylates' receptors, the dual channel ones capable of recognizing and removing of phthalate anion are rare and the task remains challenging. In this paper, a facilely synthesized amphiphilic macrocyclic acylhydrazone dimer (AMAD) can not only detect phthalate anion selectively, through both color changes and turn-on fluorescence in solution as well as in solid state, but is also able to remove it from either water or organic solvents. The current study paves the way for the search of more multiple functional receptors of dicarboxylates anions.

FRET-based fluorescent probe with favorable water solubility for simultaneous detection of SO2 derivatives and viscosity

The intracellular viscosity is an important parameter of the microenvironment and SO₂ is a vital gas signal molecule. At present, some dual-response fluorescence probes for simultaneous measurements of viscosity and SO₂ derivatives (HSO₃^-/SO₃^2-) possessed poor water solubility. In this work, we developed a water-soluble fluorescence probe CIJ (0.0864 g/100 mL of water at 20 °C) for simultaneous measurements of viscosity and SO₂ derivatives. CIJ exhibited a sensitive fluorescence enhancement to environmental viscosity from 0.97 to 28.04 cP based on a twisted intramolecular charge transfer mechanism and was applied to effective measurement of viscosity in vitro and in vivo. CIJ could also respond to SO₂ derivatives with a low detection limit (44 nM) and a fast response time (5 min) based on the nucleophilic addition reaction. Furthermore, CIJ was applied to monitor SO₂ derivatives in ratiometric response manner in living cells.

A novel RhB@MOF-808 fluorescent probe for the rapid detection of dopamine and Fe3

Dopamine (DA) and Fe³⁺ as the important bioactive ingredients, playing an indispensable role in human metabolism. Therefore, developing the accurate detection of DA and Fe³⁺ is of great significance for disease screening. Herein, we put forward a simple, rapid, and sensitive fluorescent detection strategy for the detection of dopamine and Fe³⁺ based on Rhodamine B-modified MOF-808 (RhB@MOF-808). RhB@MOF-808 produced strong fluorescence at 580 nm, and the fluorescence was significantly quenched after DA or Fe³⁺ was added, which was regarded as a static quenching process. Detection limits are as low as 60.25 nM and 48.34 nM, respectively. Furthermore, based on the responses of DA and Fe³⁺ to the probe, molecular logic gates were successfully designed. More importantly, RhB@MOF-808 had excellent cell membrane permeability and had been successfully used to label DA and Fe³⁺ in Hela cells, which presented a potential biological application value as a fluorescent probe for detecting DA and Fe³⁺.

Cu(I)-catalyzed Synthesis of Symmetrical Perfluoroterphenyl Analogues; Fluorescence, Antioxidant and Molecular Docking studies

Pentafluoroaryl analogues have been found to exhibit para specific nucleophilic aromatic substitution (S_N Ar). Herein, we describe the use of S_N Ar chemistry to create luminous perfluorinated symmetrical terphenyls. Both of S_N Ar chemistry and Cu(I)-catalyzed decarboxylative cross-coupling were applied for the synthesis of those perfluorinated symmetrical terphenyls in high yields from the corresponding derivatives of aryl iodide and potassium salt of fluorobenzoate. A series of perfluorinated symmetrical terphenyls with different para alkoxy chains were synthesized. The synthesized perfluorinated terphenyl adducts were confirmed via elemental analysis, FT-IR, ¹ H/¹³ C NMR, and ¹⁹ F NMR spectra. The absorbance and fluorescence spectra showed solvatochromic activities. The new synthesized fluoroterphenyl hybrids were screened against antioxidant inspection over DPPH performance, in assessment to Vitamin C and BHT as standard drugs exposed that fluoroterphenyl hybrid covering decyl hydrocarbons exhibited highest effectiveness through IC₅₀ values 21.74 μg/mL. Additionally, molecular docking procedures of the synthesized fluoro-terphenyl hybrids were employed by using (PDB ID: 5IKQ) protein. The docking simulation was displayed convenient and recognized findings with the antioxidant examination.

Multifunctional Cd-CP for fluorescence sensing of Cr(VI), MnO4-, acetylacetone and ascorbic acid in aqueous solutions

The development of multifunctional fluorescent chemosensors for the detection of multiple targets remains challenging but of great importance. In this paper, one novel coordination polymer (CP), denoted as [Cd₂(edda)(phen)₂]∙H₂O (compound 1, H₄edda = 5,5' (ethane-1,2-diylbis(oxy)) diisophthalic acid, phen = 1,10-phenanthroline) is successfully designed and prepared under hydrothermal conditions. Structural analysis indicates that compound 1 possesses a one-dimensional (1D) double chain structure, then self-assembles into a three-dimensional (3D) supramolecular framework via π…π interactions between phen molecules. Interestingly, compound 1 is found to be tolerant in wide range of acidic to alkaline aqueous solutions (pH = 2-13). Fluorescent spectral investigations reveal that compound 1 exhibits highly selective and sensitive fluorescence responses toward MnO₄^-, Cr(VI) ions, acetylacetone (acac) and ascorbic acid (AA) by fluorescence quenching in the aqueous phase. The detection limits are in the very low range, reaching μM level for the detection of MnO₄^-, Cr(VI) ions, nM for AA and ppm for acac detection. The distinguished multi-responsive performance suggests compound 1 to be a potential multifunctional probe. Furthermore, the possible quenching mechanisms have also been systematically investigated in this work.

Flumequine-mediated fluorescent zeolitic imidazolate framework functionalized by Eu3+ for sensitive and selective detection of UO22+, Ni2+ and Cu2+ in nuclear wastewater

Currently, antibiotics and heavy metal contaminants have posed a great threat for ecological security and human health. Herein, the lanthanide functionalized ZIF (named ZIF-90-PABA-Eu) is constructed by coordinating with Eu³⁺ via p-aminobenzoic acid intermediate. Due to the excellent fluorescence properties, the novel fluorescent probe can selectively monitor flumequine based on "turn on" mode. Furthermore, the obtained new material (named ZIF-90-PABA-Eu-Flu) can be used as "turn off" sensor for selective detection of both radioactive and nonradioactive heavy metal ions (UO₂²⁺, Ni²⁺ and Cu²⁺) which are the main component of nuclear industrial wastewater. ZIF-90-PABA-Eu-Flu shows ultra-short fluorescence response time (3 s) and ultra-low limit of detection (9.0 × 10^-3, 1.3 × 10^-2 and 6.1 × 10^-4 ppm) for three metal ions, which may be attributed to its good affinity with UO₂²⁺, Ni²⁺ and Cu²⁺. Moreover, principal component analysis (PCA) is applied to distinguish the three metal ions. Additionally, the possible sensing mechanism is investigated by the UV-vis spectra, luminescence lifetimes and theoretical calculation analysis. Based on these results, ZIF-90-PABA-Eu possesses promising potential in practical application and provides insight for the design of novel probes to continuously monitor flumequine, radioactive and nonradioactive heavy metal ions.

Variable fragment length allele-specific polymerase chain reaction (VFLASP), a method for simple and reliable genotyping

Single-nucleotide polymorphism (SNP) is a substitution of a single nucleotide at a specific position in the genome. Until now, 585 million SNPs have been identified in the human genome, and therefore, a widely applicable method is desirable to detect a specific SNP. Herein we report a simple and reliable genotyping assay, which seems to be suitable for medium and small size laboratories, as well, to easily genotype most of the SNPs. In our study, all of the possible base variations (A-T, A-G, A-C, T-G, T-C, G-C) were tested to prove the general feasibility of our technique. The basis of the assay is a fluorescent PCR, in which both allele-specific primers, differing only at the 3' end according to the sequence of the SNP, were present, and the length of one of them was modified with 3 bp by adding an adapter sequence to the 5' end of that primer. The competitive presence of both allele-specific primers excludes the false amplification of the absent allele (which can happen in simple allele-specific PCR (AS-PCR)) and ensures the amplification of the proper allele(s). Unlike other complicated genotyping methods that use of manipulation of fluorescent dyes for genotyping, we apply an approach based on the length of amplicons from different alleles to differentiate between them. In our experiment (named variable fragment length allele-specific polymerase chain reaction (VFLASP)), the investigated six SNP, containing the six available base variations, gave clear and reliable results after detecting the amplicons by capillary electrophoresis.

An ionic/thermal-responsive agar/alginate wet-spun microfiber-shaped hydrogel combined with grooved/wrinkled surface patterns and multi-functions

A dual stimuli-responsive wet-spun microfiber-shaped hydrogel is prepared by injecting a hot blend of two stimuli biopolymers alginate (i.e., ionic-responsive) and agar (i.e., temperature-responsive) into a pre-cooling and metal cation containing coagulation bath. Experimental results indicate the fiber microstructure could be manipulated by the extrusion rate and cooling temperature, achieving an anisotropic shrinkage characteristic and novel grooved/wrinkled surface patterns. Importantly, the integration of metal cations (e.g., Ca²⁺and/or Zn²⁺) was confirmed to significantly improve the hydrogel mechanical properties (i.e., double networks) and enhanced blue fluorescent intensity as a typical metal-polymer complexation formed within the agar gel matrix. Moreover, the functionality-independent double networks enabled typical pH-shape memory and sustainable antibacterial properties have also been demonstrated. Therefore, combing the facile fabricating approach and multifunctionality, this study would advance the development of stimuli-responsive hydrogel microfiber for complex biomedical systems.

A Dicationic BODIPY-Based Fluorescent Bactericide to Combat Infectious Diseases and to Eradicate Bacterial Biofilms

Increased bacterial resistance against extensively used common disinfectants has begun to emerge. The discovery of disinfectants substituting the current commercially available ones is strongly needed. For this purpose, a dicationic BODIPY-based fluorescent amphiphile has been synthesized by specific molecular design. This quaternized BODIPY behaves as a broad-spectrum disinfectant against both Gram-positive and Gram-negative bacteria strains. It exhibits potent antimicrobial activity against tested microorganisms when compared with structurally similar disinfectant benzalkonium chloride (BAC). Moreover, it shows antibiofilm activity against Staphylococcus epidermidis with a minimum biofilm eradication concentration as low as 16 μg/mL. The interaction of this compound with the bacterial cell and genomic DNA was further evaluated by fluorescence spectroscopy and microscopy to follow cell internationalization and to clarify the mechanism of antibacterial action.

Screening method toward ClbP-specific inhibitors

BACKGROUND

Colibactin is a genotoxin produced by Escherichia coli and other Enterobacteriaceae that is believed to increase the risk of colorectal cancer (CRC) of their symbiosis hosts, including human. A peptidase ClbP is the key enzyme for activation of colibactin. Inhibition of ClbP is considered to impede maturation of precolibactin into genotoxic colibactin. Therefore, ClbP-specific inhibitors could potentially prevent the onset of CRC, one of the leading causes of cancer-related deaths in the world. This study intends to establish an efficient screening system for identifying inhibitors that are specific to ClbP.

METHODS

Two types of assays were applied in the screening procedure: a probe assay and an LC-MS assay. For the probe assay, we employed the synthesized probe which we described in our previous report. This probe can be hydrolyzed efficiently by ClbP to release a fluorophore. Hence it was applied here for detection of inhibition of ClbP. For the LC-MS assay, formation of the byproduct of precolibactin maturation process, N-myristoyl-D-asparagine, was quantified using a liquid chromatography-mass spectrometry (LC-MS) technique. The probe assay can be performed much faster, while the LC-MS assay is more accurate. Therefore, our method employed the two assays in sequence to screen a large number of compounds for inhibition of ClbP.

RESULTS

A library of 67,965 standard compounds was evaluated by the screening method established in the current study, and one compound was found to show a moderate inhibitory activity against ClbP.

CONCLUSION

A simple screening method for ClbP-specific inhibitors was established. It was proven to be reliable and is believed to be useful in developing potential prophylactic agents for CRC.

Investigating the vertical distribution of dissolved organic matter in 5-m soil profiles in farmland and typical woodland on the southern loess plateau

With the implementation of the 'Grain-for-Green' program on the Chinese Loess Plateau (CLP), drought-tolerant deep-rooted plants have been increasingly introduced to the northwest in China. However, the vertical features of dissolved organic matter (DOM) in deep soil profiles on CLP during the 'Grain-for-Green' program is still not well understood. In the study, ultraviolet-visible (UV-Vis) spectroscopy and three-dimensional fluorescence excitation-emission matrices (3D-EEMs) with parallel factor analysis (PARAFAC) were used to characterize DOM in 5-m profile of farmland and forestland (Pinus tabulaeformis and Robinia pseudoacacia) in the southern CLP. The results demonstrated that the average dissolved organic carbon (DOC) content of the surface layer of farmland (119.3 mg kg^-1 soil) was lower than that of forestland (Pinus tabulaeformis 175.5 mg kg^-1 soil; Robinia pseudoacacacia 166.4 mg kg^-1 soil). The DOC content gradually decreased with increasing soil depth and reached stability after 2 m depth. Three substances, including tryptophan-like substances (C1) and two humic acid-like substances (C2, C3), were detected from all samples. Tryptophan-like substances (C1) significantly increased with soil depth while humic acid-like substances (C2, C3) significantly decreased particularly in farmland. The humic acid-like content of surface soils (Robinia pseudoacacia) was relatively higher, but the difference between the two vegetation soils was not significant. The freshness index (β/α) values of DOM as well as biological index (BIX) values were significantly higher in farmland than that in forestland, and the humification index (HIX) values were lower than in forestland soils, indicating that the change of soil DOM in farmland was more active than that in forestland and more dependent on local terrestrial sources. These results could contribute to a better understanding of the vertical distribution and features of soil DOM during the 'Grain-for-Green' program of CLP.

Monitoring cell viability in N-nitrosodiethylamine induced acute hepatitis and detection of hydrazine in solution and gas phase with Dual-function fluorescent probes

The highly toxic N-nitrosodiethylamine (NDEA) and hydrazine (N₂H₄) caused severe environmental contamination and serious health risks. Herein, we designed the two-photon ratiometric fluorescent probe (Nap-2), emission maximum shifted from 466 nm to 571 nm, to monitor cell viability of NDEA induced acute hepatitis via esterase activity detection. Furthermore, the probe Nap-2 evaluate the hydrazine (N₂H₄) content in the solution and gas phase. It is worth mentioning that we used NDEA induced acute hepatitis in the mice and evaluated the negative correlation of esterase activity in the tissue cells and serum with Nap-2. The probe Nap-2 exhibited that acute hepatitis induced by NDEA decreased cell viability. Furthermore, we made convenient test papers using Nap-2 to detect N₂H₄ in solution and gas phase. After adding N₂H₄, the fluorescence color changed from blue to yellow and was visible to the naked eye. This work provides a convenient tool and method for evaluating the toxicity of NDEA induced acute hepatitis and detecting N₂H₄ in the environment.

Simple and efficient PET and AIEE mechanism-based fluorescent probes for sensing Tabun mimic DCNP

The highly sensitive, selective, easy-to-prepare, aqueous media based on two novel probes 2-(pyren-1-yl)imidazo[1,2-a]pyridine (IMP-Py) and (2-(pyren-1-yl)imidazo[1,2-a]pyridin-3-yl)methanol (IMP-Py-OH) are synthesized for the detection of toxic chemical warfare nerve agent mimic diethylcyanochlorophosphonate (DCNP). Both probes are found effective in the detection of DCNP but comparatively, IMP-Py shows better properties in terms of instantaneous response, specificity, selectivity and a low detection limit of 16.9 nM. A significant enhancement of fluorescence intensity of IMP-Py due to aggregation-induced emission enhancement (AIEE) and photoinduced electron transfer (PET) phenomenon was inhibited due to phosphorylation of the hydroxy group of IMP-Py-OH in presence of DCNP has been observed. Taking the advantages of good sensitivity and fast response, probe IMP-Py has been fabricated into a viable paper strips portable product, tested for its potential for the detection of DCNP in tap water as well as with its vapor and response is visible under a UV lamp of 365 nm wavelength.

Selective detection of carbendazim using a upconversion fluorescence sensor modified by biomimetic molecularly imprinted polymers

The persistence of carbendazim residues in the food chain poses a potential risk to human health. Therefore, an eco-friendly selective and sensitive fluorescence nanosensor was established for carbendazim determination based on molecularly imprinted polymer (MIP) modified upconversion nanoparticles (UCNPs). The molecularly imprinted coating with methacrylamide as a functional monomer and carbendazim as a template molecule grafted on the UCNPs (UCNPs@MIP) constituted fluorescent recognition elements. The fluorescence emission of UCNPs@MIP significantly declined in the presence of carbendazim due to electron transfer induced by its selective binding with MIP cavities. The quenched fluorescence of UCNPs@MIP was recovered once the template carbendazim was eluted from the probe system. Under the optimized conditions, the proposed method offers a good linear correlation between 0.01 and 1 μg/mL, with a limit of detection (LOD) of 0.0036 μg/mL for carbendazim residues. The analytical utility and reliability of the developed biomimetic platform were examined in real food samples with good recoveries (88.790%∼102.675%) and relative standard deviation (RSD) values (0.491%∼3.779%). The method was further validated by a standard HPLC method in terms of student's t-test (p > 0.05) with no significant differences between the two methods. Hence, the proposed fluorescence sensor has prospects for rapid determination of carbendazim.

Genome Editing in Mouse and Rat by Electroporation

Many genome-edited mouse and rat strains have been produced using engineered endonucleases, including zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), or clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9. Especially, CRISPR-Cas9 is powerful tool that can be easy, rapid, and high-efficiency-produced new genome-edited strains. Furthermore, new technique, Technique for Animal Knockout system by Electroporation (TAKE), efficiently accelerate production of new strains by direct nuclease introduction into intact embryos using electroporation. This chapter presents a latest technical information in the production of genome-edited mouse and rat by TAKE method.

Electrophoretic Mobility Shift Assay (EMSA) and Microscale Thermophoresis (MST) Methods to Measure Interactions Between tRNAs and Their Modifying Enzymes

The Elongator complex is a unique tRNA acetyltransferase; it was initially annotated as a protein acetyltransferase, but in-depth biochemical analyses revealed its genuine function as a tRNA modifier. The substrate recognition and binding of the Elongator is mainly mediated by its catalytic Elp3 subunit. In this chapter, we describe protocols to generate fluorescently labeled RNAs and outline the principles underlying electrophoretic mobility shift assays (EMSA) and microscale thermophoresis (MST). These two methods allow qualitative and quantitative examinations of the binding affinity of various tRNAs toward the homologs of Elp3 from various organisms. The rather qualitative results from EMSA analyses can be nicely complemented by MST measurements allowing precise determination of the dissociation constant (K_D). We also provide detailed notes for users to mitigate potential ambiguities and technical pitfalls during the procedures.

Novel red light-emitting two-photon absorption compounds with large Stokes shifts for living cell imaging

Three novel donor-π-acceptor two-photon absorption compounds (1PZPy, 2PZIm, 3CZPy) bearing the 10-butyl-10H-phenothiazine (9-butyl-9H-carbazole) donor, the pyridinium (benzimidazolium) acceptor, and the 2,5-divinylthiophene π-bridge were synthesized and fully characterized by ¹H NMR, ¹³C NMR, FT-IR, and HRMS. The linear and nonlinear photophysical properties were systematically investigated. Their absorption properties show a strong solvent dependence, while the emission properties are nearly independent of solvent polarity. All of them possess large Stokes shifts (Δλ=149-190 nm in H₂O). 1PZPy and 3CZPy exhibit red fluorescence emission centered at about 635 and 660 nm, respectively. The two-photon absorption cross-sections measured by the open aperture Z-scan technique are determined to be 486 (1PZPy), 601 (2PZIm), and 753 GM (3CZPy) in DMF. The density functional theory calculations were further carried out to reveal their electronic structures. All the target compounds are verified to have low cytotoxicity in the working solution and good capability for one- and two-photon excitation fluorescence imaging, suggesting their potential application in bioimaging. Moreover, they show the organelle targeting ability in living cells with the high Pearson's coefficients above 0.94 for the endoplasmic reticulum.