Preconcentration of chlorophenols in water samples using threedimensional graphene-based magnetic nanocomposite as absorbent

In this paper, a novel magnetic solid-phase extraction method using three-dimensional graphene-based magnetic nanocomposite as adsorbent for the preconcentration of several chlorophenols from water samples prior to high-performance liquid chromatography analysis was developed. Various experimental parameters were investigated. Under the optimum conditions, the enrichment factors of the method were in the range of 186–312, and the limit of detection(S/N = 3) was 0.10 ng/mL. The recoveries of the method were in the range between 85.1% and 101.2%. The developed method has been successfully applied to the determination of chlorophenols in environmental water samples.     

TiO2 nanotubes： A novel solid phase extraction adsorbent for the sensitive determination of nickel in environmental water samples

A novel method was developed for the sensitive determination of nickel in environmental water samples by using TiO2 nanotubes, a new nanomaterial, as solid phase extraction absorbent. In general, TiO2 nanomaterials were often used for catalytic degradation of pollutants in environmental field, and only a very few application in environmental analytic chemistry. In present work, TiO2 nanotubes was firstly used for the enrichment of nickel and the factors would influence the preconcentration performance were optimized. Under the optimal conditions, TiO2 nanotubes exhibited its good enrichment capacity for nickel and the detection limit of the proposed method was 1 ng· mL^-1. The proposed method was validated with real water samples, and excellent results were obtained with the spiked recoveries in the range of 94.4-99.2%, respectively.     

Multi-walled carbon nanotube as a solid phase extraction adsorbent for analysis of indole-3-butyric acid and 1-naphthylacetic acid in plant samples

In this work,a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples.Owing to its large surface area and high adsorption capacity, multi-walled carbon nanotube(MWCNT) was chosen as the adsorbent for the extraction of auxins from plant samples.In this study,two important auxins were selected as model analytes,namely indole-3-butyric acid(IRA) and 1-naphthylacetic acid(NAA).They could be extracted and concentrated due to theirπ-πstacking interactions with MWCNT.Then HPLC-UV was introduced to detect IBA and NAA after sample pretreatment.Factors that may affect the enrichment efficiency were investigated and optimized.Comparative studies showed that MWCNT was superior to C18 for the extraction of the two analytes.Validation experiments showed that the optimized method had good linearity(0.9998 and 0.9960),high recovery(81.4%-85.4%),and low detection limits(0.0030 mg/L and 0.0012 mg/L).The results indicated that the novel method had advantages of convenience,good sensitivity,high efficiency, and it was feasible for the determination of auxins in plant samples.     

Ultra-sensitive detection of uranyl ions with a specially designed high-efficiency SERS-based microfluidic device

The uranyl ion(UO_2~(2+)) poses high risks to human health and the environment, hence its detection and monitoring is of utmost significance. However, the development of an ultra-sensitive, high-efficiency and convenient approach for on-site detection of UO_2~(2+) remains a challenge. Herein, a reliable and reusable surface-enhanced Raman spectroscopy(SERS)-based microfluidic biosensor was developed for rapid detection of UO_2~(2+) in real samples. The detection protocol involved the reaction of 5′-Rhodamine B(RhB)-labeled double-stranded DNA for UO_2~(2+)-specific DNAzyme-cleavage reaction in a U-shaped microchannel. Then, the reaction products were delivered into three parallel samples for high-throughput tests by SERS biochips,where 3 D ZnO-Ag mesoporous nanosheet arrays(MNSs) were modified with a single-stranded DNA(ssDNA). The ssDNAwas sequence-complementary with the 5′-RhB-labeled cleaved-stranded DNA(csDNA) from the reaction products. By the hybridization of ssDNA and csDNA, the signal probe RhB was fixed close to the surface of the ZnO-Ag MNSs to enhance the Raman signal. The limit of detection for UO_2~(2+) with the microfluidic-SERS biosensor was 3.71×10~(-15) M. An over 20,000-fold selectivity towards UO_2~(2+) response was also achieved in the presence of 15 other metal ions. The high-throughput microfluidicSERS biosensor operated well for practical UO_2~(2+) detection, with excellent recoveries in contaminated river and tap water from95.2% to 106.3%(relative standard deviation(RSD) 6.0%, n=6). Although the SERS-based microfluidic biosensor developed in this study was deployed for the detection of UO_2~(2+), the reusable and high-efficiency system may be expanded to the detection of other analytes on-site.     

Determination of Nickel and Palladium in Environmental Samples by Low Temperature ETV-ICP-OES Coupled with Liquid-liquid Extraction with Dimethylglyoxime as Both Extractant and Chemical Modifier

A novel method for the determination of nickel and palladium in environmental samples by low temperature ETV-ICP-OES with dimethylglyoxime(DMG)as both the extractant and chemical modifier has been developed.In this study,it was found that nickel and palladium can form complexes with dimethylglyoxime(0.05%,mass fraction)at pH 6.0 and can be extracted into chloroform quantitatively.The complexes can be evaporated into plasma at a suita-ble temperature(1400 ℃)for ICP-OES detection.Under the optimized conditions,the detection limits of nickel and palladium are 0.48 and 0.40 ng/mL,respectively,while the RSD values are separately 5.0% and 3.1%(ρ=50 ng/mL,n=7).The proposed method was applied to the determination of the target analytes in environmental samples with satisfactory results.     

A novel method for the determination of trace copper in cereals by dispersive liquid-liquid microextraction based on solidification of floating organic drop coupled with flame atomic absorption spectrometry

A novel,simple,rapid,efficient and environment-friendly method for the determination of trace copper in cereal samples was developed by using dispersive liquid-liquid microextraction based on solidification of floating organic drop(DLLME-SFO) followed by flame atomic absorption spectrometry.In the DLLME-SFO,copper was complexed with 8-hydroxy quinoline and extracted into a small volume of 1-dodecanol,which is of low density,low toxicity and proper melting point near room temperature. The experimental parameters affecting the extraction efficiency were investigated and optimized.Under the optimum conditions, the calibration graph exhibited linearity over the range of 0.5—500 ng/mL with the correlation coefficient(r) of 0.9996.The enrichment factor was 122 and the limit of detection was 0.1 ng/mL.The method was applied to the determination of copper in the complex matrix samples such as rice and millet with the recoveries for the spiked samples at 5.0 and 10.0 u,g/g falling in the range of 92.0-98.0%and the relative standard deviation of 3.9-5.7%.     

Porous boronate affinity monolith for on-line extraction coupled to high-performance liquid chromatography for sensitive analysis of heterocyclic aromatic amines in food samples

A novel on-line solid-phase microextraction–high-performance liquid chromatography(SPME–HPLC)system was developed for the determination of heterocyclic aromatic amines(HAAs) in food samples. A poly(vinylphenylboronic acid-co-ethylene glycol dimethacrylate) polymer monolith was prepared for on-line efficient extraction and large-volume injection was used to increase the sensitivity of detection.The polymermonolith, based on a ternary porogen, was prepared by in situ polymerization of vinylphenylboronic acid(VPBA) and ethylene glycol dimethacrylate(EGDMA) in a fused-silica capillary column. It showed good permeability, high extraction capacity, and high selectivity. The column-tocolumn reproducibility was satisfactory, and the enrichment factors for HAAs were 3746–7414.Conditions influencing the on-line extraction efficiency, including p H of sample solutions, flow rate of extraction and desorption, and desorption volume, were investigated. The proposed method had low limit of detection(0.10–0.15 ng/L) and good linearity. Trace HAAs in roast beef and lamb samples were determined, and the amounts of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline, and 2-amino-3,4,7,8-tetramethyl-3H-imidazo[4,5-f]quinoxaline in these samples were 0.235–2.08 ng/g. The recoveries for the five HAAs ranged from74.3% to 119%, and the relative standard deviation(RSDs) were less than 8.2%. The results showed that the proposed on-line method was highly sensitive for monitoring HAAs in different food samples.     

Analysis of nitrobenzene compounds in water and soil samples by graphene composite-based solid-phase microextraction coupled with gas chromatography–mass spectrometry

In this work, solid-phase microextraction coupled with gas chromatography–mass spectrometry was developed to determine trace levels of nitrobenzene compounds in water and soil samples. Graphene was chosen as the extraction material and its composite was coated on a stainless steel wire through sol–gel technique for the solid phase microextraction. The key parameters influencing the extraction efficiency were optimized. Under the optimal conditions, the linearity for the compounds was observed in the range of 0.02–15.0 mg/L for water samples, and 0.2–60.0 mg/kg for soil samples, with the correlation coefficients（r） of 0.9966–0.9987. The limits of detection of the method were 0.0025–0.005 mg/L for water samples, and 0.02–0.04 mg/kg for soil samples. The recoveries for the spiked samples were in the range of 72.0%–113.2%, and the precision, expressed as the relative standard deviations, was less than 12.1%.     

Determination of uracil in the culture fluid of Glomerella cingulata and infected hosts by high-performance liquid chromatographyEI北大核心CSCD

A CRISPR-Cas system holds great promise as a next-generation biosensing technology for molecular diagnostics. In this paper, a portable biosensor based on the trans-cleavage activity of CRISPR-Cas12a and a personal glucose meter has been developed for quantitative, sensitive and specific detection of melamine. The presence of the target melamine binds to the aptamer, leading to the release of locker DNA. And then, the leasing locker DNA activates the trans-cleavage activity of CRISPR-Cas12a to cleave the single-strand DNA (ssDNA) linker on sucrase-ssDNA modified electrode, releasing a short DNA fragment labeled with sucrase in the resulting solution. The sucrase could further catalyze sucrose to glucose, which could be detected by the PGM. Under the optimized conditions, the increase of PGM signal was relative with the concentration of melamine ranging from 0.1 to 2.5 μmol/L and the limit of detection (LOD) was 37 nmol/L. Moreover, the portable biosensor has strong specificity and can be used for the quantitative detection of melamine in milk samples. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Portable biosensor for quantitative detection of melamine based on CRISPRCas12a and a personal glucose meterEI北大核心CSCD

A CRISPR-Cas system holds great promise as a next-generation biosensing technology for molecular diagnostics. In this paper, a portable biosensor based on the trans-cleavage activity of CRISPR-Cas12a and a personal glucose meter has been developed for quantitative, sensitive and specific detection of melamine. The presence of the target melamine binds to the aptamer, leading to the release of locker DNA. And then, the leasing locker DNA activates the trans-cleavage activity of CRISPR-Cas12a to cleave the single-strand DNA (ssDNA) linker on sucrase-ssDNA modified electrode, releasing a short DNA fragment labeled with sucrase in the resulting solution. The sucrase could further catalyze sucrose to glucose, which could be detected by the PGM. Under the optimized conditions, the increase of PGM signal was relative with the concentration of melamine ranging from 0.1 to 2.5 μmol/L and the limit of detection (LOD) was 37 nmol/L. Moreover, the portable biosensor has strong specificity and can be used for the quantitative detection of melamine in milk samples. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

An Intelligent DNA Nanorobot for Autonomous Anticoagulation

Artificial nanorobots that can recognize molecular triggers and respond with programable operations provide an inspiring proof‐of‐principle for personalized theragnostic applications. We have constructed an intelligent DNA nanorobot for autonomous blood anticoagulation in human plasma. The DNA nanorobot comprises a barrel‐shaped DNA nanostructure as the framework and molecular reaction cascades embedded as the computing core. This nanorobot can intelligently sense the concentration of thrombin in the local environment and trigger an autonomous anticoagulation when excess thrombin is present. The triggering concentration of thrombin at which the nanorobot responds can be tuned arbitrarily to avoid possible side effects induced by excess thrombin. This makes the nanorobot useful for autonomous anticoagulation in various medical scenarios and inspires a more efficient and safer strategy for future personalized medicine.     

A novel technology for the detection, enrichment, and separation of trace amounts of target DNA based on amino-modified fluorescent magnetic composite nanoparticles

A novel, highly sensitive technology for the detection, enrichment, and separation of trace amounts of target DNA was developed on the basis of amino-modified fluorescent magnetic composite nanoparticles (AFMN). In this study, the positively charged amino-modified composite nanoparticles conjugate with the negatively charged capture DNA through electrostatic binding. The optimal combination of AFMN and capture DNA was measured by dynamic light scattering (DLS) and UV–vis absorption spectroscopy. The highly sensitive detection of trace amounts of target DNA was achieved through enrichment by means of AFMN. The detection limit for target DNA is 0.4 pM, which could be further improved by using a more powerful magnet. Because of their different melting temperatures, single-base mismatched target DNA could be separated from perfectly complementary target DNA. In addition, the photoluminescence (PL) signals of perfectly complementary target DNA and single-base mismatched DNA as well as the hybridization kinetics of different concentrations of target DNA at different reaction times have also been studied. Most importantly, the detection, enrichment, and separation ability of AFMN was further verified with milk. Simple and satisfactory results were obtained, which show the great potential in the fields of mutation identification and clinical diagnosis.     

Specific enrichment of prokaryotic DNA using a recombinant DNA-binding protein

Targeted enrichment of DNA is often necessary for its detection and characterization in complex samples. We describe the development and application of the novel molecular tool for the specific enrichment of prokaryotic DNA. A fused protein comprising the DNA-binding subunit of the bacterial topoisomerase II, gyrase, was expressed, purified, and immobilized on magnetic particles. We demonstrated the specific affinity of the immobilized protein towards bacterial DNA and investigated its efficiency in the samples with high background of eukaryotic DNA. The reported approach allowed for the selective isolation and further detection of as few as 5 pg Staphylococcus aureus DNA from the sample with 4?×?10⁶-fold surplus of human DNA. This method is a promising approach for the preparation of such type of samples, for example in molecular diagnostics of sepsis.     

Facile fabrication of hydrophilic PAA-Ti/TiO2 nanocomposite for selective enrichment and detection of phosphopeptides from complex biological samples

Highly selective enrichment of trace phosphorylated proteins or peptides from complex biological samples is of profound significance for the discovery of disease biomarkers in biological systems. In this study, a novel affinity material has been synthesized to improve the enrichment specificity for phosphopeptides by using PAAS as coupling molecule. In the resulting materials, highly abundant titanium is available for selective enrichment of phosphopeptides, with plenty of carboxylate groups that can inhibit nonspecific adsorption. The enrichment results demonstrated that the hydrophilic PAA-Ti/TiO₂ composite possesses excellent selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/non-phosphopeptides (1:1000), extreme sensitivity (the detection limit was at the fmol level), and high recovery of phosphopeptides (as high as 78%). Moreover, the as-prepared nanocomposite provides effective enrichment of phosphopeptides from real samples (mouse liver), showing great potential in the detection of low-abundance phosphopeptides in biological samples.     

气泡富集-高效液相色谱法测定地表水样中微量土霉素

建立了气泡富集-高效液相色谱（HPLC）测定地表水样中微量土霉素的方法。采用新型样品前处理方法--气泡富集法,对水溶液中的微量土霉素进行富集,考察了气泡富集条件对富集效果的影响。研究发现,在优化的气泡富集和色谱条件下,土霉素的富集倍数可达37.06,土霉素含量测定的RSD为4.8%（n=11）,LOD为0.038 mg/L。将该方法用于地表水样中土霉素的测定,平均加标回收率为101.9%。可见,气泡富集法对土霉素的富集效果好,能与色谱结合用于地表水样中土霉素的快速、灵敏、准确检测。同时,在进行样品前处理时无需任何有机溶剂,而且装置简单、成本低廉、易操作。可见气泡富集法是一种非常有研究和推广价值的绿色样品前处理方法,有望用于复杂样品中其他微量甚至痕量物质的分析。     

Screening of microdialysates taken before and after induced liver damage; on-line solid phase extraction-electrospray ionization-mass spectrometry

A novel method is described to follow known and unknown compounds in biological processes using microdialysis sampling and mass spectrometric detection. By implementation of internal standard, desalting/enrichment for the sample work-up, and multivariate data analysis, this methodology is a basis for future applications in early diagnosis of diseases and organ damage, as a complement to the routinely used clinical methods for biological samples. The present study includes screening without specific target analytes, of samples collected by microdialysis from liver of anaesthetized rats before and after local damage to this organ. Sample series were classified by principal component analysis, and the stimulation was identified in the chemical patterns produced by the presented analytical tool.     

A microfluidic chip‐based fluorescent biosensor for the sensitive and specific detection of label‐free single‐base mismatch via magnetic beads‐based “sandwich” hybridization strategy

A novel microfluidic chip‐based fluorescent DNA biosensor, which utilized the electrophoretic driving mode and magnetic beads‐based “sandwich” hybridization strategy, was developed for the sensitive and ultra‐specific detection of single‐base mismatch DNA in this study. In comparison with previous biosensors, the proposed DNA biosensor has much more robust resistibility to the complex matrix of real saliva and serum samples, shorter analysis time, and much higher discrimination ability for the detection of single‐base mismatch. These features, as well as its easiness of fabrication, operation convenience, stability, better reusability, and low cost, make it a promising alternative to the SNPs genotyping/detection in clinical diagnosis. By using the biosensor, we have successfully determined oral cancer‐related DNA in saliva and serum samples without sample labeling and any preseparation or dilution with a detection limit of 5.6 × 10^?11 M, a RSD (n = 5) < 5% and a discrimination factor of 3.58–4.54 for one‐base mismatch.     

Applications of aptamers in cancer cell biology

Identifying cells associated with specific disease states is critically important for the early detection and diagnosis of cancer. To facilitate this task, molecular probes, which bind biomarkers that are either specifically or differentially expressed in diseased cells relative to healthy cells, provide a simple and effective method. This review focuses on the use of DNA aptamers as molecular probes for cancer cells. These aptamers are created by means of the cell-based Systematic Evolution of Ligands by EXponential enrichment (SELEX) process, which uses whole disease cells as targets. We describe at length the steps of the cell-SELEX process and discuss several applications for the aptamers, including profiling leukemia patient samples and discovering cell-surface cancer biomarkers. We conclude with a discussion of an aptamer-conjugated nanoparticle enrichment and detection scheme.     

An electrochemical microRNA biosensor based on protein p19 combining an acridone derivate as indicator and DNA concatamers for signal amplification

The new acridone derivative 5, 7-dinitro-2-sulfo-acridone (DSA) with excellent electrochemical activity was synthesized and reported for the first time in this paper. Then an electrochemical biosensor was fabricated for the signal amplified detection of microRNA (miRNA) via applying home-made DSA as signal unit. The p19 protein-functionalized magnetic beads (PFMBs) for specific recognition and enrichment of miRNA. Then DSA is combined with the long DNA concatamers, which functions as a signal enhancement platform to facilitate the high selectivity and sensitivity determination of miRNA. The usage of this novel electrochemical activity made a contribution to the performance of the approach, such as achieving a detection limit of 6 aM. To the best of our knowledge, this is the first attempt to apply DSA, PFMBs and long DNA concatamers for the fabrication of the electrochemical biosensors, which may represent a promising path toward early diagnosis of cancer at the point of care.     

水溶性硼酸亲和富集材料的制备及基于酶联免疫吸附法检测人肝微粒体糖蛋白的应用

生物样品中的糖蛋白丰度低,且在检测中易受到其它非糖蛋白的抑制和干扰,需在分析检测前对糖蛋白进行富集,但常规的基于固相材料的糖蛋白富集方法不易与生物技术中最经典的酶联免疫吸附法(ELISA)兼容.本研究以树枝状聚合物PAMAM 4.0为载体, 结合硼酸亲和技术,制备了新型水溶性硼酸亲和富集材料(DBC),并将其应用于基于ELISA的人肝微粒体中糖蛋白的检测.采用标准糖蛋白对DBC富集条件进行优化,然后考察其灵敏度和抗干扰能力,将优化后的方法应用于复杂样品人肝微粒体糖蛋白富集.结果表明,DBC对糖蛋白的富集选择性可高达100000倍,可将糖蛋白的富集信号提高100倍.以DBC为富集材料,与ELISA分析技术相结合,只需一步简单的孵育,即可实现生物样品中糖蛋白的高灵敏度、高选择性检测,为疾病相关的糖蛋白组学研究提供了一种有效的检测手段.