查看更多>>摘要：Developing non-noble metal, even metal-free chemical sensors for the detection of toxic heavy metal ions is significantly desirable for economically and environmentally sustainable application but has heretofore remained elusive. Herein, a L-cysteine functionalized graphene oxide nanosheet (CGO) nanoarchitectonics, greenly synthesized by a very simple method at room temperature, was utilized to realize the simultaneous enrichment and colorimetric detection of trace mercury ions (Hg2+). It was discovered that CGO, as a nanozyme mimic exhibited greatly enhanced peroxidase-like catalytic activity than the pristine graphene oxide. By exploring the interactions of CGO nanozyme with colorimetric substrate, 3,3',5,5'-tetramethylbenzidine (TMB) and target Hg2+ ions, we found that the sensing principle was based mainly on the competitive adsorption between Hg2+ ions and TMB over CGO. The pre-capture of Hg2+ ions hindered the TMB binding on CGO, resulting in the promoted oxidation of TMB by H2O2 to produce more colored oxidation products, from which the colorimetric sensing of Hg2+ was realized with a good detection effect on 5 mu g L-1 solution. As an enrichment-sensing integration platform, this metal-free sensor is cost-effective and sensitive, and presents considerable anti-interference ability over other metal ions. Overall, this work not only expands the application of graphene-based materials in colorimetric detection but also provides a general sensing principle to construct highly sensitive sensors.
Fang, XiaonaLi, WenjingGao, TianZahra, Qurat Ul Ain...
8页
查看更多>>摘要：In this paper, we report the development of a new strategy termed integrated digital PCR-fluorescence activated sorting based SELEX (IFS-SELEX) that enables rapid screening of aptamers against fluorescent targets. Initially, this strategy employs an integrated digital PCR system to amplify each sequence of a preliminarily enriched library, which is obtained by a traditional SELEX method, on the surface of polystyrene beads. Then, the asprepared beads are incubated with the fluorescent target and then subjected to fluorescence-activated sorting. Since only those sequences with high binding affinity for the target are collected and sequenced, unnecessary analysis of ineligible sequences is avoided by this method, and the aptamer selection process is thereby greatly streamlined. As a proof-of-concept, we applied this strategy for the screening of aptamers against two fluorescent targets, i.e., ciprofloxacin (CFX) and thioflavin T (ThT), and successfully obtained corresponding sequences with low dissociation constants. The binding affinities of aptamers for ThT were well associated with the sorting regions defined in the fluorescence channel of the flow cytometry process. The experimental results demonstrated that the as-designed IFS-SELEX method can serve as a universal platform for rapid, facile, and efficient aptamer selection against various fluorescent targets.
Balamurugan, GopalJang, Jae WoongPark, Se JeongVikneshvaran, Sekar...
8页
查看更多>>摘要：Selective detection and determination of silver ions are tricky due to the poor reactivity and the interference of various metal ions and halides. Only a few cases have been reported concerning sulfur-based functionality. This work proposes silver-selective probes exhibiting peculiar colorimetric and photothermal responses without the need for sulfur-functional groups. Tetrakis(4-dialklyaminophenyl)1,4-phenylenediamine containing hexyl and methoxytriethyleneglycol substituents, PTS1 and PTS2, respectively, are selectively oxidized by silver ions to form dicationic diimmonium salts. The resulting quinone diimminium salts show strong absorption in the near infrared (NIR) region with intense color changes. The striking color change is observed from pale brown to intense olive green with immediate responses. PTS1 shows a higher binding constant and nanomolar detection limit, whereas PTS2 shows a sub-micromolar detection limit. Job's plot studies reveal the stoichiometric ratio as 1:2 (PTS1: Ag+). Due to the strong NIR absorption of the oxidized PTS probes, the temperature rise is monitored, after adding silver ions, by a thermal camera and in-contact thermal sensors. The concentration of the actual samples can be determined based on a calibration plot with a temperature change as a function of silver ion concentration. The current results offer highly selective and ultrasensitive probes for silver ions under multiple detection mediums, including naked eye and photothermal detection.
查看更多>>摘要：Development of efficient adsorbents to inorganic anions as a solid phase extraction (SPE) material is highly desirable for chromatographic analysis and pollution control. In this work we developed a new hybrid cationic microcrystalline cellulose aerogel composite. Cationic cetylpyridinium imbedded montmorillonite (CPC-MT) was uniformly entrapped in microcrystalline cellulose (MCC) to enhance anionic adsorption efficiency and mechanical stability. The developed CPC-MT@MCC aerogel was used as an SPE adsorbent for anions from dairy wastewater by coupling with ion-column chromatography. Further quaternized CPC-MT@MCC aerogel (CPCMT@QMCC) showed unique low density (10.6 mg cm(-3)), large specific surface area (320 m(2) g(-1)), porosity 70%, 800 mg g(-1) nitrate adsorption capacity within 60 min and ease of elution in alkaline solutions. The CPCMT@QMCC aerogel showed efficient regeneration and reuse performances for up to 10 cycles. More importantly, a dynamic binding efficiency of 710 mg g(-1) highlights its excellent performance for practical applications. 96% of nitrate anion from environmental manure wastewater samples were adsorbed with 98.7% recovery. A good linear relationship was obtained in the range of 0.01-10 mg L-1 and the limits of detection was 0.5 mg L-1 using CPC-MT@QMCC aerogel as a preconcentration column. The successful synthesis of such intriguing and economic CPC-MT@QMCC aerogel may provide a promising matrix for high-performance and high efficiency chromatographic media.
查看更多>>摘要：The CRISPR-Cas system has achieved breakthrough applications in the field of molecular diagnostics. CRISPR/Cas12a can accurately identify subtle changes in a target nucleic acid sequence and has a wide range of applications such as in highly sensitive detection methods. In this study, an upconversion-magnetic probe-DNA-Fe3O4 probe was designed to replace traditional fluorescent probes using nucleic acid aptamers to design a biosensing method powered by CRISPR/Cas12a. The CRISPR/Cas12a technology can be widely used for sensitive, rapid, and stable detection of ochratoxin A. In our sensing strategy, the ochratoxin A capture probe was used to capture ochratoxin A and release the Cas protein activation chain, further triggering the single-stranded DNA degradation activity of CRISPR/Cas12a and removal of the fluorescent probe to generate a fluorescent signal. Compared with traditional commercial kits, our method was more rapid and exhibited comparable detection capability.
查看更多>>摘要：In-situ surface analysis has always been a significant but challenging issue in many analytical applications. To enable surface sampling and MS analysis on the field, a handheld liquid microjunction-surface sampling probe (hLMJ-SSP) was coupled to a miniature mass spectrometer in this study. The hLMJ-SSP was connected to the miniature mass spectrometer with a 50 cm long flexible tube and controlled by an integrated microcontroller unit (MCU). By simply pressing a button on the probe, automated surface analysis could be carried out and completed within similar to 2 min, in which solvent delivery, sample extraction, extract aspiration, injection and MS analysis were performed in sequence. A limit of detection (LOD) as low as 5 pg was achieved. The capability of in-situ surface analysis was also demonstrated by directly analyzing illicit drug residues on fingers and medicines in biological fluids. With the merits of automated operation, high sensitivity and nondestructive analysis, this LMJ-SSP-mini MS system would be a promising tool for various in-situ analytical applications.
查看更多>>摘要：Research of detection of low molecular weight compounds on human health and biological systems become increasingly important. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), a soft ionization equipment, is a rapid, reliable, high-sensitivity, high-throughput and simple test instrument. However, the application of MALDI-TOF MS in the analysis of small molecules (<500 Da) has become a great challenge because of the interference from the conventional matrices in low mass region when using conventional matrices. In this research, tricobalt tetraoxide (Co3O4) nanocrystals with rich surface hydroxyl groups were synthesized and served as novel matrices for the detection of small molecules by MALDI-TOF MS. In comparison with conventional organic matrices, the use of as-prepared Co3O4 nanocrystal matrices showed little matrix background interference, good reproducibility and high signal intensity in the analyses of amino acids, harmful additives and pesticide residues. For the detection of most amino acids, Co3O4 nanocrystal matrices have good detection performance both in the positive and negative ion modes and have a unique decarboxylation peak in the positive ion mode, which is conducive to the identification of amino acids. In addition, Co3O4 nanocrystals are completely feasible to test triadimefon, pirimicarb and other pesticide residues, as well as additives such as bisphenol A and melamine in the positive ion mode. It is also feasible to detect small molecule compounds in practical samples using Co3O4 nanocrystals as matrices. We believe the work provides an alternative approach for the detection of small molecules and expands the application scope of Co3O4 nanocrystals.
查看更多>>摘要：Organic compounds in drinking water can be potentially hazardous. In this study, we demonstrate for the first time that combining in-bottle thin-film microextraction (TFME), comprehensive two-dimensional gas chromatography, and time-of-flight mass spectrometry (GC x GC-TOFMS) can produce a powerful, green tool for determining multiple organic pollutants in drinking water and monitoring changes in water samples after treatment with a water purification system. In the developed approach, water is added to an amber sampling bottle containing TFME membranes and left to sit until equilibration is achieved. Once equilibration has been achieved, the membranes are withdrawn, and the extracted compounds are quantified via thermal desorption in the GC x GC-TOFMS system. This approach enabled a large number of organic compounds with a wide range of physicochemical properties to be identified based on their mass spectra. A series of drinking water samples (raw water, water after softener filter, and drinking water) were collected from a standard house faucet in order to analyze changes following treatment with a water purification system. The developed strategy was also applied to identify the concentrations of the 9 selected organic compounds in the water samples. Ultimately, the in-bottle TFME-GC x GC-TOFMS method is straightforward and provides comparable performance to other methods for low-level analyses of organic pollutants in drinking water samples.
查看更多>>摘要：African swine fever virus (ASFV) can cause highly contagious and fatal disease among domestic pigs, resulting in considerable economic losses for swine breeders. There is a strong demand for accurate, rapid, and simple detection methods especially for on-site application. Nucleic acid testing is the most commonly used method for ASFVdetection. However, traditional nucleic acid purification step is time- and labor-consuming. The nucleic acid purification, amplification and amplicons detection rely on laboratory settings which limits the on-site detection. Here, we proposed a simple and cost-effective detection method that utilized filter paper to purify nucleic acids from swine blood and employed CRISPR/Cas12a-mediated loop-mediated isothermal amplification (LAMP) reaction to detect ASFV. The filter paper which was made into dipsticks could effectively purify nucleic acids from whole blood in 2 min. This simple and low-cost purification method avoided multiple pipetting steps and potential amplification inhibitors (e.g., ethanol) that were generally used in traditional nucleic acids extraction processes. After nucleic acid purification, the lyophilized LAMP reagent dissolved by elution solution was employed to perform isothermal amplification reaction on a portable heating block. The CRISPR/Cas12a system was designed to specifically detect amplicons. Assisted by a portable homemade device, the fluorescent signals produced by positive samples could be observed by the naked eye, while negative samples remained colorless. The whole detection procedure could be finished within 50 min with a detection limit of one copies/mu L. This established method provided a novel strategy for rapid visualized detection and showed great potential for on-site application.
NSTL
Elsevier