Search

The avian influenza A H7N9 virus is known as one of the newly discovered highly pathogenic avian influenzas with serious threat to public health and the poultry industry. In this work, an ultrasensitive surface-enhanced Raman scattering (SERS) determination of H7N9 virus via exonuclease III-assisted cycling amplification was proposed to meet the needs of rapid, sensitive and accurate detection of H7N9-related genes. The SERS strategy aims to simultaneously determine the characteristic gene fragments of H7 and N9 by specially designing Capture, Replace, and Probe single-strand DNAs to realize exonuclease III-assisted cycling amplifications, and then integrating the cyclic amplification with SERS-active Ag nanorods array substrate to achieve an ultrasensitive SERS determination of H7N9. After characterizing the effectiveness of the sensing mechanism and further investigating the surface blocking and the dosage of exonuclease III, the optimal surface blocking was achieved by using 10 μM and 100 μM mercaptohexanol for H7 and N9 detection respectively, and the optimal Exo III concentrations for sensing H7 and N9 were 0.10 U μL -1 and 0.30 U μL -1 respectively. Under the optimal conditions, dual and specific detections of H7 and N9 gene fragments were obtained with detection linear interval from 1 fM to 100 pM and limit of detections low to 31 aM of H7 and 44 aM of N9, as well as recovery in the range of 93.8-106.2% with relative standard deviation less than 6.12%. The proposed ultrasensitive SERS strategy can provide a powerful tool for determining H7N9 virus and other avian influenza viruses., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Saliva is progressively becoming a useful alternative to urine and blood to assess human exposure to toxics in biomonitoring campaigns, because of its easy and stress-free collection by unskilled personnel. This evaluation is highly challenging owing to the large number of compounds and individuals involved. In this article, we propose a new strategy to simplify sample treatment in the human biomonitoring of toxics in saliva. It is based on the in situ formation of supramolecular solvents (SUPRASs) in the sample. For this purpose, SUPRASs were produced in colloidal suspensions of aggregates of hexanol in THF under the addition of saliva, which played the dual role of inductor of the self-assembly process leading to SUPRAS formation and the sample to be analysed. The SUPRAS formation region was delimited from the phase diagram constructed for the ternary mixture saliva/hexanol/THF. An equation was derived for predicting the volume of SUPRASs produced as a function of the proportion of their components. The new strategy was explored for simplifying sample treatment in the biomonitoring of thirteen free bisphenol analogues and derivatives by liquid chromatography tandem mass spectrometry. Absolute recoveries for bisphenols were in the range 95-105.6%, the method was interference free (signal suppression/enhancement was between 93 and 106%), and the repeatability and within laboratory reproducibility were in the intervals 0.6-10% and 2-16%, respectively. The proposed method was fully validated and it was applied to the determination of the target bisphenols in saliva from 13 volunteers. Free bisphenol A was found in all samples (0.057-0.8 μg L -1 ), and bisphenol F, bisphenol S and bisphenol AF were found with a frequency of detection of 46%, 62% and 8%, respectively. So, saliva can be a suitable biological sample for studying human exposure to bisphenols. To the best of our knowledge, this is the first report dealing with the use of saliva for biomonitoring human exposure to bisphenols., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Monitoring of amphetamine-type stimulant (ATS) confronts clinical labs with a high number of samples involving a variety of biological matrices. Liquid chromatography-tandem mass spectrometry (LC-MS/MS), routinely used for confirmation of ATS abuse, requires of laborious and matrix-dependent sample treatment methods, this increasing analysis time and cost. In this work, a universal and single-step sample treatment, based on supramolecular solvents (SUPRAS), was proposed for simplifying ATS confirmation in seven biological matrices. The SUPRAS was synthesized in situ in the sample (900 µL of basified oral fluid, urine, serum, sweat or breast milk or 50 mg of digested hair or fingernails) by the addition of hexanol (200 µL) and tetrahydrofuran (900 µL). The mixture was vortex-shaken and centrifuged and the SUPRAS extract was subsequently analyzed by positive ion mode electrospray LC-MS/MS. The method was fully validated for amphetamine (AMP), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), N-ethyl-3,4-methylenedioxyamphetamine (MDEA) and N-methyl-3,4-methylenedioxyamphetamine (MDMA). Maximum ion suppression or enhancement was 9% and 7%, respectively, and extraction recoveries (87-111%) and within- (0.1-6.7%) and between-day (0.3-9.7%) CVs were all within required values. The lower limits of quantification (LLOQ) for biological fluids (5 ng/mL), and hair and fingernails (100 ng/g) were all well below the cut-offs established by worldwide organizations. Confirmation of MDA was carried out in five urine samples that tested positive for ATS by immunoassay. The SUPRAS-LC-MS/MS methodology succeeded in developing a hitherto unexplored and universal tool for quantifying ATS in a comprehensive pool of biological matrices of interest in forensic and clinical samples., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this paper, a FRET (Forster resonance energy transfer) based fluorescence method was developed for the quickly detection of ochratoxin A (OTA) in agricultural products (e.g., flour and beer). A highly fluorescent nitrogen doped carbon dots (CD) were served as energy donor, the DNA and MCH (6-mercapto-1-hexanol) modified Ag nanoparticles were served as energy acceptor in the FRET system. OTA can be detected in a concentration range between 10 and 5000 nM, the limit of detection is 8.7 nM. This method has three advantages: (1) an enhanced fluorescent intensity can be acquired by utilizing the nitrogen doped CD synthesized by one-step approach without sophisticated modification of nanoparticles; (2) OTA detection was accomplished quickly (less than 30 min) by using MCH as assistant molecule; (3) an extended OTA detection linear range was acquired, which may facilitate the OTA detection in real agricultural samples, and is helpful for solving food safety problems., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Fabrication of a new electrochemical impedance-based biosensor for the analysis of parathyroid hormone (PTH), using self-assembled monolayers (SAMs) of mercaptohexanol and (3-Aminopropyl) triethoxysilane on gold electrodes, was investigated for the first time in the field. Anti-PTH was used as a biorecognition element. To monitor immobilization processes in the biosensor fabrication, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) techniques were successfully operated. CV and EIS techniques were also used in quantification of PTH. Energy-dispersive X-ray analysis (EDAX) was also applied to identify surface modifications. Fabrication and working parameters of the biosensor were optimized. Moreover, Kramers-Kronig transformations were performed for validation of obtained EIS data in all steps of biosensor fabrication. The linear PTH detection range of the presented biosensor was 10-50 pg/mL PTH. The chrono-impedance technique for real-time monitoring of PTH binding was also implemented. The biosensor has exhibited good repeatability (with a correlation) and reproducibility. Finally, artificial serum samples spiked with known concentrations of PTH were analyzed by the proposed biosensor. To demonstrate the feasibility of the biosensor in practical analysis, real human serum samples and the artificial serum samples were analyzed., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid-liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d × 250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r(2)>0.99) were obtained within the range 1-5000 μg L(-1) for all compounds except for 3-F (10-5000 µg L(-1)) and PAT (0.5-100 μg L(-1)). The limits of detection (0.28-3.2 µg L(-1)) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape)., (© 2013 Published by Elsevier B.V.)

We report a simple and sensitive method for label-free detection of single-stranded DNA-binding protein (SSBP) based on an array of microfabricated cantilevers. The single-stranded DNA (ssDNA) was immobilized on the surface of the sensing cantilevers to detect SSBP, while the reference cantilevers were modified with 6-mercapto-1-hexanol to detect any unwanted cantilever deflection. The differential deflection signals that reveal specific SSBP-ssDNA binding have been found to depend on the SSBP concentration. Using the cantilever array sensor we can detect SSBP in the concentration range from 0.01 to 7 μg mL(-1). Other proteins, such as thrombin or bovine serum albumin induced no significant deflection of the cantilevers. Our results show the potential for the application of cantilever array sensor system as a powerful tool to detect proteins with high sensitivity and specificity., (Copyright © 2013 Elsevier B.V. All rights reserved.)

While high storage stability of sequence-selective DNA biosensors is crucial towards their routine applications, commonly used electrochemical hybridization biosensors are characterized with limited storage stability. In this article we demonstrate that recently developed ternary thiolated monolayers impart dramatic improvement in the storage stability of DNA electrochemical biosensors. In particular, highly stable multicomponent interfaces are prepared by co-immobilizing the thiolated capture probe (SHCP) with 1,6-hexanedithiol (HDT) on gold substrates, followed by the incorporation of 6-mercapto-1-hexanol (MCH) diluent. The resulting (SHCP/HDT+MCH) DNA hybridization recognition platform offers substantially higher storage stability compared to conventional binary (SHCP+MCH) monolayers. The (SHCP/HDT+MCH) ternary monolayers maintain their initial signal (S)-to-noise (N) ratio (S/N) over a prolonged 3 months period upon storage at 4 °C, compared to the rapid sensitivity loss observed using the common binary interfaces. This attractive stability performance promises the convenient usage of pre-prepared electrodes after prolonged time storage without any treatment. Such dramatic improvements in the storage stability have been achieved through a rational optimization of the concentration ratio of the SHCP and the other components of the ternary SAM. The improved storage stability of SHCP/HDT+MCH interfaces observed at higher concentrations of SHCP is attributed to a hindered displacement of SHCP by MCH in the resulting compact layers. The ability to design highly stable nucleic acid interfaces using common chemicals obviates the need of using specialized expensive reagents., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The development of rapid, low-cost and reliable diagnostic methods is crucial for the identification and treatment of many diseases. Screen-printed gold electrodes (Au/SPEs), coated with a ternary monolayer interface, involving hexanedithiol (HDT), a specific thiolated capture probe (SHCP), and 6-mercapto-1 hexanol (MCH) (SHCP/HDT/MCH) are shown here to offer direct and sensitive detection of nucleic acid hybridization events in untreated raw biological samples (serum, urine and crude bacterial lysate solutions). The composition of the ternary monolayer was modified and tailored to the surface of the Au/SPE. The resulting SHCP/HDT/MCH monolayer has demonstrated to be extremely useful for enhancing the performance of disposable nucleic acid sensors based on screen-printed electrodes. Compared to common SHCP/MCH binary interfaces, the new ternary self-assembled monolayer (SAM) resulted in a 10-fold improvement in the signal (S)-to-noise (N) ratio (S/N) for 1 nM target DNA. The SHCP/HDT/MCH-modified Au/SPEs allowed the direct quantification of the target DNA down to 25 pM (0.25 fmol) and 100 pM (1 fmol) in undiluted/untreated serum and urine samples, respectively, and of 16S rRNA Escherichia coli (E. coli) corresponding to 3000 CFU μL(-1) in raw cell lysate samples. The new SAM-coated screen-printed electrodes also displayed favorable non-fouling properties after a 24h exposure to raw human serum and urine samples, offering great promise as cost-effective nucleic acid sensors for a wide range of decentralized genetic tests., (Copyright © 2011 Elsevier B.V. All rights reserved.)