Lidong Wu

Nanographene-based tyrosinase biosensor for rapid detection of bisphenol A.

Hydrophilic nanographene (NGP) prepared by ball milling of graphite was used as the support to construct a novel tyrosinase biosensor for determination of bisphenol A (BPA). The performances of the nanographene-based tyrosinase biosensor were systematically compared with those of multiwall carbon nanotubes (MWNTs) modified tyrosinase biosensors. The results indicated that the nanographene-based tyrosinase biosensor provided significant advantages over MWNTs-based tyrosinase biosensor in term of response, repeatability, background current and limit of detection (LOD), which could be attributed to its larger specific surface area and unique hierarchical tyrosinase-NGP nanostructures. The nanographene-based tyrosinase biosensor displayed superior analytical performance over a linear range from 100 nmol L(-1) to 2000 nmol L(-1), with LOD of 33 nmol L(-1) and sensitivity of 3108.4 mA cm(-2)M(-1). The biosensor was further used for detecting BPA (leaching from different vessels) in tap water, and the accuracy of the results was validated by high performance liquid chromatography (HPLC). The nanographene-based tyrosinase biosensor proved to be a promising and reliable tool for rapid detection of BPA leached from polycarbonate plastic products and for on-site rapid analysis of emergency pollution affairs of BPA.

3D metal-organic framework as highly efficient biosensing platform for ultrasensitive and rapid detection of bisphenol A

As is well known, bisphenol A (BPA), usually exists in daily plastic products, is one of the most important endocrine disrupting chemicals. In this work, copper-centered metal-organic framework (Cu-MOF) was synthesized, which was characterized by SEM, TEM, XRD, FTIR and electrochemical method. The resultant Cu-MOF was explored as a robust electrochemical biosensing platform by choosing tyrosinase (Tyr) as a model enzyme for ultrasensitive and rapid detection of BPA. The Cu-MOF provided a 3D structure with a large specific surface area, which was beneficial for enzyme and BPA absorption, and thus improved the sensitivity of the biosensor. Furthermore, Cu-MOF as a novel sorbent could increase the available BPA concentration to react with tyrosinase through π-π stacking interactions between BPA and Cu-MOF. The Tyr biosensor exhibited a high sensitivity of 0.2242A M(-1) for BPA, a wide linear range from 5.0×10(-8) to 3.0×10-6moll(-1), and a low detection limit of 13nmoll(-1). The response time for detection of BPA is less than 11s. The proposed method was successfully applied to rapid and selective detection of BPA in plastic products with satisfactory results. The recoveries are in the range of 94.0-101.6% for practical applications. With those remarkable advantages, MOFs-based 3D structures show great prospect as robust biosensing platform for ultrasensitive and rapid detection of BPA.

Comparative study of graphene nanosheet- and multiwall carbon nanotube-based electrochemical sensor for the sensitive detection of cadmium

A novel nanocomposite was obtained through the controlled surface modification of graphene nanosheets (nanographene) with Nafion by ultrasonic oscillation. The composite was used as an ultrasensitive platform for the detection of cadmium ions (Cd(2+)) by differential pulse anodic stripping voltammetry (DPASV) analysis. The performance of the nanographene-based sensor was systematically compared with that of a multiwall carbon nanotube (MWCNT)-modified sensor. The results indicate that the nanographene-based sensor exhibits significant advantages over the MWCNT-based sensor in terms of repeatability, sensitivity and limit of detection (LOD). The nanographene-based sensor displayed superior analytical performance over a linear range of Cd(2+) concentrations from 0.25μgL(-1) to 5μgL(-1), with a LOD of 3.5ngL(-1). This sensor was also used to systematically screen for 6 types of chemicals, including sodium salts, magnesium salts and zinc salts. It was observed that the sensor could successfully differentiate cadmium ions from interferents (magnesium salts, zinc salts, etc.). The nanographene-based sensor was also demonstrated to be a promising and reliable tool for the rapid detection of cadmium existing in tap water and for the rapid on-site analysis of critical pollution levels of cadmium.

Response Characteristics of Bisphenols on a Metal–Organic Framework-Based Tyrosinase Nanosensor

Bisphenols (BPs), which have more than ten kinds of structural analogues, are emerging as the most important endocrine disrupting chemicals that adversely affect human health and aquatic life. A tyrosinase nanosensor based on metal-organic frameworks (MOFs) and chitosan was developed to investigate the electrochemical response characteristics and mechanisms of nine kinds of BPs for the first time. The developed tyrosinase nanosensor showed a sensitive response to bisphenol A, bisphenol F, bisphenol E, bisphenol B, and bisphenol Z, and the responsive sensitivities were highly dependent on their respective log Kow values. However, the nanosensor showed no response to bisphenol S (BPS), bisphenol AP (BPAP), bisphenol AF (BPAF), or tetrabromobisphenol A, although BPS, BPAP, and BPAF have structures similar to those of the responsive BPs. The obtained results reveal that the electrochemical response of different BPs is affected not only by the molecular structure, especially the available ortho positions of phenolic hydroxyl groups, but also by the substituent group properties (electron acceptor or electron donor) on the bisphenol framework. The electronic cloud distribution of the phenolic hydroxyl groups, which is affected by the substituent group, determines whether the available ortho positions of phenolic hydroxyl groups can be oxidized by the tyrosinase biosensor. These response mechanisms are very significant as they can be used for predicting the response characteristics of many BPs and their various derivatives and metabolites on biosensors. The unexpected anti-interference ability of the biosensor to nine heavy metal ions was also discovered and discussed. The MOF-chitosan nanocomposite proves to be a promising sensing platform for the construction of diverse biosensors for selective detection of targets even in the presence of a high concentration of heavy metal ions.

Rapid determination of tricaine mesylate residues in fish samples using modified QuEChERS and high-performance liquid chromatography-tandem mass spectrometry

A rapid and effective modified, quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed for the determination of tricaine mesylate (MS-222) in fish samples using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Samples were extracted with the mixture of acetonitrile and acetate buffer, and then cleaned with primary/secondary amino (PSA) absorbents. The determination of MS-222 was achieved in less than 4.0 min using an electrospray ionization source in the positive mode (ESI+). The QuEChERS method was validated by evaluating the repeatability, linearity, precision, and trueness. The limit of detection (LOD) was 2.5 μg kg−1 and the limit of quantification (LOQ) was 10.0 μg kg−1. The calibration curve was linear in the range of 2–1000 μg L−1 (R2 > 0.9999). Average recoveries of MS-222 were in the range of 79.6–119.7%, with a relative standard deviation (RSD) lower than 6%.

Gold Nanoparticles dotted Reduction Graphene Oxide Nanocomposite Based Electrochemical Aptasensor for Selective, Rapid, Sensitive and Congener-Specific PCB77 Detection

Gold nanoparticles (AuNP) dotted reduction graphene oxide (RGO-AuNP) is used as a platform for an aptamer biosensor to selectively detect 3,3′4,4′-polychlorinated biphenyls (PCB77). By anchoring aptamers onto the binding sites of RGO-AuNP and making use of the synergy effect of RGO and AuNP, the RGO-AuNP based biosensor exhibits superior analytical performances to AuNP based biosensor in terms of sensitivity and repeatability. The sensitivity of RGO-AuNP based aptamers (RGO-AuNP-Ap) biosensor (226.8 μA cm−2) is nearly two times higher than that of Au based biosensors (AuNP-Ap/Au electrode, 147.2 μA cm−2). The RGO-AuNP-Ap/Au biosensor demonstrated a linear response for PCB77 concentrations between 1 pg L−1 and 10 μg L−1, with a low limit of detection (LOD) of 0.1 pg L−1. The superb LOD satisfies the exposure thresholds (uncontaminated water < 0.1 ng L−1) set out by International Agency for Research on Cancer (IARC) and the Environmental Protection Agency (EPA). The proposed biosensor can be a powerful tool for rapid, sensitive and selective detection of PCBs on site.

A comparative study of primary secondary amino (PSA) and multi-walled carbon nanotubes (MWCNTs) as QuEChERS absorbents for the rapid determination of diazepam and its major metabolites in fish samples by high-performance liquid chromatography–electrospray ionisation–tandem mass spectrometry

BACKGROUND A simple and fast modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method is presented for the determination of diazepam and its three major metabolites, nordiazepam, temazepam and oxazepam (benzodiazepines) in fish samples by liquid chromatography-electrospray ionisation-tandem mass spectrometry. RESULTS Muscle tissues were extracted with acetonitrile, and then cleaned with primary secondary amino (PSA) adsorbents. The cleanup effect of PSA was compared with that of multi-walled carbon nanotubes (MWCNTs) in term of extraction efficiency. The better results were obtained when PSA was used. The chromatography separation was achieved within 5.0 min on a C18 column. The limit of detection was 0.5 µg kg(-1) and the limit of quantification was 2.5 µg kg(-1). Average recoveries of diazepam and its main metabolites were in the range of 88.5-110.1%, with a relative standard deviation lower than 10.0%. CONCLUSION The proposed method for fish samples gives good recoveries, linearity, precision and accuracy.

A novelty strategy for the fast analysis of sulfonamide antibiotics in fish tissue using magnetic separation with high-performance liquid chromatography-tandem mass spectrometry.

A simple, fast and low-cost extraction method with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) determination was developed on sulfonamide antibiotics (SAs) in fish tissue. Magnetic separation was first introduced into the rapid sample preparation procedure combined with acetonitrile extraction for the analysis of SAs. Partitioning was rapidly achieved between acetonitrile solution and solid matrix by applying an external magnetic field. Acetonitrile solution was collected and concentrated under a nitrogen stream. The residue was redissolved with 1‰ formic acid aqueous solution and defatted with n-hexane before analysis. The recoveries of SAs were in the range of 74.87-104.74%, with relative standard deviations <13%. The limits of quantification and the limits of detection for SAs ranged from 5.0 to 25.0 μg (kg-1) and from 2.5 to 10.0 μg (kg-1) , respectively. The presented extraction method proved to be a rapid method which only took 20 min for one sample preparation procedure. Copyright

Preparation, characterization and application of octadecyl modified magnesium oxide microspheres

A new solid-phase extraction sorbent, octadecyl modified magnesium oxide (C18-MgO) microspheres, was successfully prepared in the present work. Its composition, morphology and structure were studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N(2) adsorption-desorption technique, and solid-state nuclear magnetic resonance (NMR). The as-synthesized C18-MgO was employed as a solid-phase extraction sorbent for the enrichment of polycyclic aromatic hydrocarbons (PAHs) in aqueous solutions. Several factors affecting the extraction efficiency of PAHs, including the type and concentration of organic modifiers, flow rate, sample volume, and the types of rinsing solvents and eluting solvents, were investigated systematically. The results demonstrated that C18-MgO was superior to MgO in terms of large volume in loading samples. In comparison with MgO and Sep-Pak C18, C18-MgO exhibited excellent extraction efficiency (>91% except for naphthalene) in respect of high recoveries under the optimized conditions. The limits of detection varied from 0.001 to 0.603 ng mL(-1) for 15 PAHs using high-performance liquid chromatography coupled with a fluorescence detector, indicating that the analytical method was highly sensitive. The proposed method was applied to enrich PAHs in tap water and acceptable recoveries (18-96%) were obtained.

An electrochemical deoxyribonucleic acid biosensor for rapid genotoxicity screening of chemicals

A sensitive electrochemical biosensor based on double-stranded deoxyribonucleic acid (DNA) has been proposed for rapid screening of chemicals genotoxicity potential. A DNA probe from the clone RP3-402G11 gene of the human DNA sequence and electroactive methylene blue (MB) have been used as a biorecognition element and signal amplification molecules respectively for evaluating the genotoxic potential of target analytes with high sensitivity. The biosensing mechanism of genotoxicity screening is based on the damage of targets for the DNA double helix, which results in the subsequent distinct change of the electrochemical signal. More than 10 kinds of genotoxic chemicals have been used as testing analytes including highly toxic dioxins (polychlorinated dibenzodioxins, polychlorinated dibenzofurans) and polychlorinated biphenyls (PCBs). Dioxins and dioxin-like chemicals have been identified as highly genotoxic chemicals by the proposed DNA biosensor, which is consistent with the conclusion from International Agency for Research on Cancer. The results obtained demonstrated that the signal response of the biosensor for dioxins and PCBs correlated well with their toxic equivalent factor (TEF) values and concentrations of tested targets. The biosensor proved to be a promising in vitro screening tool for rapid estimation of chemicals genotoxicity potential.