Optical detection of organophosphorus compounds based on Mn-doped ZnSe d-dot enzymatic catalytic sensor

Enzymeless voltammetric sensor for simultaneous determination of parathion and paraoxon based on Nd-based metal-organic framework

The aim of this work is to fabricate a sensitive and novel enzymeless electrochemical sensor for the simultaneous determination of parathion and paraoxon using the Nd-UiO-66@MWCNT nanocomposite. For this purpose, Neodymium (Nd) was introduced into a Universitetet i Oslo (UiO-66) structure to construct Nd-UiO-66 and then, adding multi-walled carbon nanotubes to the Nd-UiO-66 to increase the electrocatalytic activity and surface area of the obtained composite. The Nd-UiO-66@MWCNT has numerous advantages like excellent conductivity, tunable texture, and large surface area and can be used as a distinctive structure for the construction of modified glassy carbon electrode (GCE) to enhance the charge-transfer and the efficiency of electrochemical sensors. This modified electrode showed sensitive and selective determination of paraoxon and parathion over the linear ranges of 0.7-100 and 1-120 nM, with detection limits of 0.04 and 0.07 nM, respectively. The proposed Nd-UiO-66@MWCNT/GCE sensor in this study can be applied in environmental and toxicological laboratories and field tests to detect parathion and paraoxon levels.

Comparative metabolomics analysis of milk components between Italian Mediterranean buffaloes and Chinese Holstein cows based on LC-MS/MS technology

Buffalo and cow milk have a very different composition in terms of fat, protein, and total solids. For a better knowledge of such a difference, the milk metabolic profiles and characteristics of metabolites was investigated in Italian Mediterranean buffaloes and Chinese Holstein cows were investigated by liquid chromatography tandem-mass spectrometry (LC-MS/MS) in this study. Totally, 23 differential metabolites were identified to be significantly different in the milk from the two species of which 15 were up-regulated and 8 down-regulated in Italian Mediterranean buffaloes. Metabolic pathway analysis revealed that 4 metabolites (choline, acetylcholine, nicotinamide and uric acid) were significantly enriched in glycerophospholipid metabolism, nicotinate and nicotinamide metabolism, glycine, serine and threonine metabolism, as well as purine metabolism. The results provided further insights for a deep understanding of the potential metabolic mechanisms responsible for the different performance of Italian Mediterranean buffaloes' and Chinese Holstein cows' milk. The findings will offer new tools for the improvement and novel directions for the development of dairy industry.

Carbon dot composites for bioapplications: a review

Recent advancements in the synthesis of carbon dot composites and their applications in biomedical fields (bioimaging, drug delivery and biosensing) have been carefully summarized. The current challenges and future trends of CD composites in this field have also been discussed.

Recent advances and perspectives of enzyme-based optical biosensing for organophosphorus pesticides detection

The overuse or abuse of organophosphorus pesticides (OPs) can bring about severe contamination problems in foodstuff and the environment, which will seriously threaten human health and the ecosystem's cycle. Hence, it is in high demand to establish sensitive, portable, specific, and cost-effective methods for monitoring OPs to control food safety, protect the ecosystem, and prevent disease. The optical biosensor with enzyme as bio-recognition elements has been an effective alternative for OPs detection. Herein, we firstly introduce various enzymes, sensing mechanisms, advantages and disadvantages used as bio-recognition elements in optical sensing for OPs detection. Then, we review various optical biosensing strategies based on enzymes as recognition elements that were ingeniously designed and successfully utilized for OPs detection, with a particular emphasis on photoluminescence (PL), chemiluminescence (CL), electrochemiluminescence (ECL), and colorimetric (CM) biosensing strategies. We not only highlight the state-of-art developments and the construction strategies of the enzyme-based optical biosensing method but also summarize the existing deficiencies, current challenges, and the future perspectives of OPs detection.

Recent Advances on Detection of Insecticides Using Optical Sensors

Insecticides are enormously important to industry requirements and market demands in agriculture. Despite their usefulness, these insecticides can pose a dangerous risk to the safety of food, environment and all living things through various mechanisms of action. Concern about the environmental impact of repeated use of insecticides has prompted many researchers to develop rapid, economical, uncomplicated and user-friendly analytical method for the detection of insecticides. In this regards, optical sensors are considered as favorable methods for insecticides analysis because of their special features including rapid detection time, low cost, easy to use and high selectivity and sensitivity. In this review, current progresses of incorporation between recognition elements and optical sensors for insecticide detection are discussed and evaluated well, by categorizing it based on insecticide chemical classes, including the range of detection and limit of detection. Additionally, this review aims to provide powerful insights to researchers for the future development of optical sensors in the detection of insecticides.

A dual-signal sensor for the analysis of parathion-methyl using silver nanoparticles modified with graphitic carbon nitride

A highly sensitive and selective method was developed for both UV-vis spectrophotometric and fluorimetric determination of organophosphorus pesticides (OPs). This method used silver nanoparticles (AgNPs) modified with graphitic carbon nitride (g-C3N4). The AgNPs reduced the fluorescence intensity of g-C3N4. Acetylthiocholine (ATCh) could be catalytically hydrolyzed by acetylcholinesterase (AChE) to form thiocholine, which induces aggregation of the AgNPs. This aggregation led to the recovery of the blue fluorescence of g-C3N4, with excitation/emission peaks at 310/460 nm. This fluorescence intensity could be reduced again in the presence of OPs because of the inhibitory effect of OPs on the activity of AChE. The degree of reduction was found to be proportional to the concentration of OPs, and the limit of fluorometric detection was 0.0324 μg/L (S/N = 3). In addition, the absorption of the g-C3N4/AgNPs at 390 nm decreased because of the aggregation of the AgNPs, but was recovered in presence of OPs because of the inhibition of enzyme activity by OPs. This method was successfully applied to the analysis of parathion-methyl in real samples.

Enzyme-based optical biosensors for organophosphate class of pesticide detection

A systematic review of enzyme based optical detection schemes for the detection and analysis of organophosphate pesticides has been presented.

Displaying of acetylcholinesterase mutants on surface of yeast for ultra-trace fluorescence detection of organophosphate pesticides with gold nanoclusters

Acetylcholinesterase (AChE) has been widely applied on the enzyme inhibition-based detection of organophosphate pesticides (OPs). To improve the sensitivity of fluorometric OPs assay, great efforts were made to change the fluorometric probes or analytical strategies rather than improve the sensitivity of AChE towards OPs. In this work, AChE wild-type (WT) and mutants (E69Y and E69Y/F330L) from Drosophila were successfully displayed on the surface of yeast through a-agglutinin-mediated microbial surface display system. The location of AChE on yeast surface was confirmed by immunofluorescence analysis. Further, a fluorescence OPs detection method was developed by combining yeast surface-displayed AChE mutants and protein-directed electronegative fluorescent gold nanoclusters (Au NCs). Yeast surface-displayed AChE can catalyze the hydrolysis of acetylthiocholine to produce thiocholine. The electropositive thiocholine can not only bind with AuNCs by Au-S bond but also absorb Au NCs by the electrostatic interaction, leading to the aggregation of AuNCs and corresponding fluorescence quenching. When AChE was incubated with paraoxon, a typical model of OPs, the activity of AChE was inhibited and the thiocholine-induced aggregation of AuNCs was reduced. The fluorescence assay based on Au NCs and yest-AChE-E69Y/F330L exhibited the ultra-sensitivity for ultra-trace OPs and 2-6 orders of magnitude lower detection limit (3.3 × 10^-14 M) than those of AChE-WT-based method and other reported methods. In addition, the proposed method showed excellent reliability for the real samples assay. This work would provide an alternative strategy for the improvement of bio-analysis at its source.

Construction of a luminescent sensor based on a lanthanide complex for the highly efficient detection of methyl parathion

A highly sensitive and selective luminescent sensor for the detection of methyl parathion (MP) pesticide was described in this study. The target molecule HL was synthesized by modifying the structure of 4-hydroxybenzlidene imidazolinone (HBI) with nitrogen-containing heterocyclic 1,10-phenanthroline. In the presence of Eu3+, a HL-Eu3+ complex was formed which could emit strong red fluorescence due to the removal of coordinated water molecules and an intramolecular energy transfer from HL to Eu3+. Addition of MP into the strongly fluorescent solution of HL-Eu3+ induced quenching of the complex's fluorescence, and this quenching behavior occurred because of the competition coordination of MP and HL for Eu3+. A calibration curve was developed that related the extent of fluorescence quenching to MP concentration, making the HL-Eu3+ system a sensitive and selective fluorescent sensor for MP. Under the experimental conditions, the detection limit for MP was down to 95 nM based on LOD = 3σ/S. Moreover, the fluorescence assay developed here allowed the detection of MP in two different types of real samples including pond water and pear juice, and satisfactory results demonstrate that this fluorescent sensor based on HL-Eu3+ has potential application in environment and food analysis.

A poly(thymine)-templated fluorescent copper nanoparticle hydrogel-based visual and portable strategy for an organophosphorus pesticide assay

Since fluorescence assays with high sensitivity for organophosphorus pesticides (OPs) are urgently required to protect the ecosystem and prevent disease, an environmentally friendly and label-free fluorescent probe is desirable. Herein, a poly-thymine30 DNA-templated copper nanoparticle (poly T30-Cu NPs) hydrogel fluorescent probe was explored for the construction of an OPs sensing platform via tyrosinase (TYR) enzyme-controlled quenching. Initially, TYR can efficiently quench the fluorescence of poly T30-Cu NPs; however, when OPs are mixed with a certain amount of TYR, the fluorescence of poly T30-Cu NPs can be recovered. Based on this phenomenon, we designed a functionalized hydrogel based on poly T30-Cu NPs for portable and visible detection of OPs with high sensitivity and selectivity. This proposed fluorescent platform was demonstrated to enable rapid detection of OPs (paraoxon as the model analyte) and provide excellent sensitivity with a detection limit of 3.33 × 10-5 ng μL-1 and a linear range of 1.0 × 10-4-1.0 ng μL-1. The fluorescent probe does not require a sophisticated synthesis and labeling process; in addition, it is environmentally friendly because of the presence of a biotemplate of DNA and biocompatible copper. Moreover, the functional hydrogel combines the features of portability, visualization, fast signal response and environmental anti-interference that make the proposed strategy more feasible in complex practical detection.

Template protection of gold nanoclusters for the detection of organophosphorus pesticides

A simple and economic fluorescence sensing method has been developed. This method based on trypsin digestion of the template of BSA-AuNCs for the sensitive detection of OPs.

Colorimetric recognition of 6-benzylaminopurine in environmental samples by using thioglycolic acid functionalized silver nanoparticles

A simple and selective colorimetric sensor thioglycolic acid capped silver nanoparticles (TGA-AgNPs) was developed for the detection of 6-benzylaminopurine (6-BAP). The synthesized TGA-AgNPs were characterized by UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopic (TEM) techniques. The TGA-AgNPs as a sensor for binding 6-BAP through hydrogen-bonding and π-π bonding that causes large conjugate clusters, resulting in a color change from yellow to reddish orange. The surface plasmon resonance (SPR) band of TGA-AgNPs at 397nm is red-shifted to 510nm, which confirms that 6-BAP induces the aggregation of TGA-AgNPs. Under the optimized conditions, a linear relationship between the absorption ratio (A510nm/A397nm) and 6-BAP concentration was found in the range of 4-26μM. The detection limit of 6-BAP was 0.2μM, which is lower than the other analytical techniques. Moreover, the proposed sensor was successfully applied for the detection of 6-BAP in environmental samples with good recoveries. The proposed assay provides a simple and cost-effective method for the analysis of 6-BAP in vegetable and water samples.

Quantum Dots Applied to Methodology on Detection of Pesticide and Veterinary Drug Residues

The pesticide and veterinary drug residues brought by large-scale agricultural production have become one of the issues in the fields of food safety and environmental ecological security. It is necessary to develop the rapid, sensitive, qualitative and quantitative methodology for the detection of pesticide and veterinary drug residues. As one of the achievements of nanoscience, quantum dots (QDs) have been widely used in the detection of pesticide and veterinary drug residues. In these methodology studies, the used QD-signal styles include fluorescence, chemiluminescence, electrochemical luminescence, photoelectrochemistry, etc. QDs can also be assembled into sensors with different materials, such as QD-enzyme, QD-antibody, QD-aptamer, and QD-molecularly imprinted polymer sensors, etc. Plenty of study achievements in the field of detection of pesticide and veterinary drug residues have been obtained from the different combinations among these signals and sensors. They are summarized in this paper to provide a reference for the QD application in the detection of pesticide and veterinary drug residues.

L-tyrosine methyl ester-stabilized carbon dots as fluorescent probes for the assays of biothiols

Over the past few decades, assays of biothiols had attracted much attention due to the essential role they played in human physiology, especially using the fluorescent analysis. In most cases, competitive mechanism was often employed, where the metal ions were often introduced as the quenchers and thiols competed with metal ions due to the high binding affinity and strong thiophilicity for 'signal-on' assays. To develop a metal ions-free approach for the assays of thiols, here, L-tyrosine methyl ester capped carbon dots (Tyr-CDs) were employed and prepared as the fluorescent probes. The as-prepared Tyr-CDs displayed narrow size distribution and distinct blue fluorescence with high quantum yield (12.9%) compared with the unmodified CDs. Moreover, Tyr-CDs exhibited higher quenching efficiency due to the efficient energy transfer between Tyr-CDs and the quinone products in the presence of tyrosinase. When the targeted biothiols was present, the catalytic reaction of the tyrosinase to the formation of quinone was inhibited and the fluorescence signal was recovered in a biothiols-concentration-dependent manner, which provided the basis for the analysis of biothiols. The practical application of the present system was demonstrated by testing the biothiols in human plasma samples and good recovery was obtained, indicating that the sensing platform we proposed hold great promise in the accurate detection of biothiols in complex biosystems.

Oxidase-mimicking activity of ultrathin MnO2 nanosheets in colorimetric assay of acetylcholinesterase activity

In the present study, a novel colorimetric sensing platform was constructed for quantitative detection of acetylcholinesterase (AChE) activity and its inhibitor. Manganese dioxide (MnO₂) nanosheets as an oxidase-mimicking nanomaterial could directly oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into oxTMB without the need for horseradish peroxidase and H₂O₂. When AChE was introduced, acetylthiocholine could be catalytically hydrolyzed to produce thiocholine, which easily triggers the decomposition of MnO₂ nanosheets, causing the decrease of solution absorbance. Owing to the inhibition effect of organophosphorus pesticides, the enzymatic activity was suppressed, preventing the decomposition of MnO₂ and resulting in the increase of absorbance. Under optimal conditions, the colorimetric platform shows sensitive responses to AChE and paraoxon in the range of 0.1-15 mU mL^-1 and 0.001-0.1 μg mL^-1, respectively. The detection limits of AChE and paraoxon reached 35 μU mL^-1 and 1.0 ng mL^-1, respectively. Furthermore, the MnO₂-TMB platform has been used to fabricate test strips for rapid and convenient visual detection of AChE and its inhibitor with highly promising performance.

Morphology-controlled synthesis and electron field emission properties of ZnSe nanowalls

Novel ZnSe nanowalls on a Zn substrate with optimum morphology exhibit enhanced field emission performance.

An on–off–on gold nanocluster-based fluorescent probe for sensitive detection of organophosphorus pesticides

In this study, a highly sensitive fluorescent probe based on bovine serum protein-protected gold nanoclusters (BSA-AuNCs) was developed for the determination of organophosphorus pesticides (OPs).

Electrospun nanofibres in agriculture and the food industry: a review

The interesting characteristics of electrospun nanofibres, such as high surface-to-volume ratio, nanoporosity, and high safety, make them suitable candidates for use in a variety of applications. In the recent decade, electrospun nanofibres have been applied to different potential fields such as filtration, wound dressing, drug delivery, etc. and a significant number of review papers have been published in these fields. However, the use of electrospun nanofibres in agriculture is comparatively novel and is still in its infancy. In this paper, the specific applications of electrospun nanofibres in agriculture and food science, including plant protection using pheromone-loaded nanofibres, plant protection using encapsulation of biocontrol agents, preparation of protective clothes for farm workers, encapsulation of agrochemical materials, deoxyribonucleic acid extraction in agricultural research studies, pre-concentration and measurement of pesticides in crops and environmental samples, preparation of nanobiosensors for pesticide detection, encapsulation of food materials, fabrication of food packaging materials, and filtration of beverage products are reviewed and discussed. This paper may help researchers develop the use of electrospun nanofibres in agriculture and food science to address some serious problems such as the intensive use of pesticides. © 2016 Society of Chemical Industry.

Highly-sensitive organophosphorus pesticide biosensors based on CdTe quantum dots and bi-enzyme immobilized eggshell membranes

An optical biosensing method using CdTe quantum dots (QDs) and bi-enzyme-immobilized eggshell membranes for the determination of organophosphorus pesticides (OPs) has been developed.

A new water-soluble and colorimetric fluorescent probe for highly sensitive detection of organophosphorus pesticides

A new water-soluble fluorescent probe bearing 1,8-naphthalimide dye, a quaternary ammonium salt and a boronate group was developed for the detection of organophosphorus pesticides.

An immobilization multienzyme microfluidic chip for acetylcholinesterase inhibition assay by fluorescence method

A bi-enzyme immobilized microfluidic device was developed for the rapid enzyme inhibition assay by fluorescence detection.

A ratiometric fluorescent quantum dots based biosensor for organophosphorus pesticides detection by inner-filter effect

In this work, we develop a novel and sensitive sensor for the detection of organophosphorus pesticides based on the inner-filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent quantum dots (RF-QDs). The RF-QDs has been designed by hybridizing two differently colored CdTe QDs, in which the red emissive QDs entrapped in the silica sphere acting as the reference signal, and the green emissive QDs covalently attached on the silica surface serving as the response signal.The fluorescence of RF-QDs could be quenched by AuNPs based on IFE. Protamine could effectively turn on the fluorescence due to the electrostatic attraction between protamine and AuNPs. Trypsin can easily hydrolyze protamine, leading to the quench of the fluorescence. Then, the fluorescence could be recovered again by the addition of parathion-methyl (PM) which could inhibit the activity of trypsin. By measuring the fluorescence of RF-QDs, the inhibition efficiency of PM to trypsin activity was evaluated. Under the optimized conditions, the inhibition efficiency was proportional to the logarithm of PM concentration in the range of 0.04-400 ng mL(-1), with a detection limit of 0.018 ng mL(-1). Furthermore, the simple and convenient method had been used for PM detection in environmental and agricultural samples with satisfactory results.

A potentiometric biosensing system based on an isolated degrading bacterium Klebsiella sp. MP-6 for the determination of methyl parathion

A potentiometric system for methyl parathion using bacterial cells as bioreceptors and an anion-sensitive electrode as a transducer is described.

A highly sensitive multi-catalytic sensing system for organophosphorus and organochlorine pesticides based on the peroxidase-like activity of ferric ions

A novel and highly sensitive multi-catalytic sensing system was successfully developed for OPs and organochlorine pesticides, on the basis of the color reaction of TMB catalyzed by Fe³⁺ ions.

Biosensors containing acetylcholinesterase and butyrylcholinesterase as recognition tools for detection of various compounds

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are enzymes expressed in the human body under physiological conditions. AChE is an important part of the cholinergic nerves where it hydrolyses neurotransmitter acetylcholine. Both cholinesterases are sensitive to inhibitors acting as neurotoxic compounds. In analytical applications, the enzymes can serve as a biorecognition element in biosensors as well as simple disposable sensors (dipsticks) and be used for assaying the neurotoxic compounds. In the present review, the mechanism of AChE and BChE inhibition by disparate compounds is explained and methods for assaying the enzymes activity are shown. Optical, electrochemical, and piezoelectric biosensors are described. Attention is also given to the application of sol-gel techniques and quantum dots in the biosensors’ construction. Examples of the biosensors are provided and the pros and cons are discussed.