Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Functional fluorescence assay of botulinum neurotoxin A in complex matrices using magnetic beads
Klisara, Nevena ; Peters, Jeroen ; Haasnoot, Willem ; Nielen, Michel W.F. ; Palaniappan, Alagappan ; Liedberg, Bo - \ 2019
Sensors and Actuators B: Chemical (2019). - ISSN 0925-4005 - p. 912 - 919.
Botulinum neurotoxin A - Fluorescence detection - Peptide - Superparamagnetic beads

The extremely toxic botulinum neurotoxin poses a threat for health and food safety, requiring rapid and easy-to-use detection platforms. To meet these requirements, we have explored a novel functional assay format for detection of botulinum neurotoxin serotype A light chain (BoNT/A LC) in complex matrices. The proposed assay utilizes a synthetic peptide designed to mimic the SNAP-25 protein (synaptosomal-associated protein 25) as substrate bound to a superparamagnetic bead and a fluorescent dye. Cleavage of the peptide by BoNT/A LC yields a reduction in fluorescence signal revealing the presence of the BoNT/A LC in the sample matrices tested. The superparamagnetic beads enable efficient separation of the cleaved peptides from food matrices, thereby improving the reliability of responses. Herein, we demonstrate a protocol offering an assay time of 6 h and a LOD of 0.5 nM (25 ng/ml). The proposed protocol is validated using carrot juice and diluted milk pending further improvements in sensitivity and overall assay time. Robustness, cost-effectiveness, low sample volume requirements in conjunction with the possibility of multiplexing for other proteolytic enzymes makes the proposed protocol competitive in comparison with conventional BoNT assays reported elsewhere.

Economic and epidemiological impact of different intervention strategies for clinical contagious mastitis
Gussmann, Maya ; Steeneveld, Wilma ; Kirkeby, Carsten ; Hogeveen, Henk ; Nielen, Mirjam ; Farre, Michael ; Halasa, Tariq - \ 2018
Journal of Dairy Science (2018). - ISSN 0022-0302
cow-specific - culling - simulation model - treatment

The overall aim of this study was to compare different intervention strategies for clinical intramammary infections (IMI). We conducted a simulation study to represent a Danish dairy cattle herd with IMI caused mostly by Staphylococcus aureus and 9 different intervention strategies for clinical IMI. A standard intervention of 3 d of treatment consisting of intramammary injections for all clinical cases was used. Two of the strategies reflected the use of more antibiotics and 6 strategies reflected cow-specific treatment or culling decisions. For these strategies, we assessed the cost and effectiveness of culling as an IMI intervention. Our results showed that nearly all strategies could reduce the number of IMI cases [e.g., a median of 37 clinical cases with the extended intramammary treatment over 5 d strategy (Basic5) and 30 clinical cases with the cow culled with recovery probability below 50% (Before50)] compared with the standard intervention (median of 42 clinical cases). This happened alongside either increased antibiotic usage (e.g., from a median of 123 treatment days up to 179 treatment days with strategy Basic5) or an increased number of cows culled in relation to IMI (e.g., from a median of 16 up to 24 cows with strategy Before50). Strategies with more antibiotics or reactive culling had a slightly higher net income (e.g., €190,014 median net income with strategy Basic5 or €196,995 with strategy Before50 compared with €187,666 with the standard strategy). This shows that a cow-specific clinical intervention approach can be cost-effective in reducing IMI incidence.

Direct Food Analysis by (transportable) Ambient Ionization Mass Spectrometry
Nielen, Michel - \ 2018
A systematic knowledge synthesis on the spatial dimensions of Q fever epidemics
Rooij, Myrna M.T. de; Leuken, Jeroen P.G. van; Swart, Arno ; Kretzschmar, Mirjam E.E. ; Nielen, Mirjam ; Koeijer, Aline A. de; Janse, Ingmar ; Wouters, Inge M. ; Heederik, Dick J.J. - \ 2018
Zoonoses and Public Health (2018). - ISSN 1863-1959
airborne exposure - Coxiella burnetii - epidemiology - Q fever - risk assessment - spatial analysis

From 2007 through 2010, the Netherlands experienced the largest Q fever epidemic ever reported. This study integrates the outcomes of a multidisciplinary research programme on spatial airborne transmission of Coxiella burnetii and reflects these outcomes in relation to other scientific Q fever studies worldwide. We have identified lessons learned and remaining knowledge gaps. This synthesis was structured according to the four steps of quantitative microbial risk assessment (QMRA): (a) Rapid source identification was improved by newly developed techniques using mathematical disease modelling; (b) source characterization efforts improved knowledge but did not provide accurate C. burnetii emission patterns; (c) ambient air sampling, dispersion and spatial modelling promoted exposure assessment; and (d) risk characterization was enabled by applying refined dose–response analyses. The results may support proper and timely risk assessment and risk management during future outbreaks, provided that accurate and structured data are available and exchanged readily between responsible actors.

Comparison of gas chromatography/quadrupole time-of-flight and quadrupole Orbitrap mass spectrometry in anti-doping analysis : I. Detection of anabolic-androgenic steroids
Abushareeda, Wadha ; Tienstra, Marc ; Lommen, Arjen ; Blokland, Marco ; Sterk, Saskia ; Kraiem, Suhail ; Horvatovich, Peter ; Nielen, Michel ; Al-Maadheed, Muhammad ; Georgakopoulos, Costas - \ 2018
Rapid Communications in Mass Spectrometry 32 (2018)23. - ISSN 0951-4198 - p. 2055 - 2064.

Rationale: The World Anti-Doping Agency (WADA) encourages drug-testing laboratories to develop screening methods that can detect as many doping substances as possible in urine. The use of full-scan high-resolution acquisition (FS/HR) with gas chromatography/mass spectrometry (GC/MS) for the detection of known and unknown trimethylsilyl (TMS) derivatives of anabolic-androgenic steroids (AAS) provides anti-doping testing bodies with a new analytical tool. Methods: The AAS were extracted from urine samples by generic liquid–liquid extraction, after enzymatic hydrolysis, and TMS derivatization. The extracted urine was analyzed by GC/Q-TOF and GC/Q-Orbitrap to compare the performance of the two instrument types for the detection of 46 AAS in human urine. The quantitation of endogenous anabolic steroids and the ability of the two analytical platforms to comply with the requirements for testing as part of the WADA Athlete Biological Passport (ABP) were also assessed. Results: The data presented show that the analytical performance for both instruments complies with the WADA specifications. The limits of detection (LODs) for both instruments are well below the WADA 50% Minimum Required Performance Levels. The mass errors in the current study for the GC/Q-Orbitrap platform are lower than those obtained for the GC/Q-TOF instrument. Conclusions: The data presented herein proved that both molecular profiling platforms can be used for antidoping screening. The mass accuracies are excellent in both instruments; however, the GC/Q-Orbitrap performs better as it provides higher resolution than the GC/Q-TOF platform.

Reactive Laser Ablation Electrospray Ionization Time-Resolved Mass Spectrometry of Click Reactions
Geenen, Fred A.M.G. van; Franssen, Maurice C.R. ; Zuilhof, Han ; Nielen, Michel W.F. - \ 2018
Analytical Chemistry 90 (2018)17. - ISSN 0003-2700 - p. 10409 - 10416.

Reactions in confined compartments like charged microdroplets are of increasing interest, notably because of their substantially increased reaction rates. When combined with ambient ionization mass spectrometry (MS), reactions in charged microdroplets can be used to improve the detection of analytes or to study the molecular details of the reactions in real time. Here, we introduce a reactive laser ablation electrospray ionization (reactive LAESI) time-resolved mass spectrometry (TRMS) method to perform and study reactions in charged microdroplets. We demonstrate this approach with a class of reactions new to reactive ambient ionization MS: so-called click chemistry reactions. Click reactions are high-yielding reactions with a high atom efficiency, and are currently drawing significant attention from fields ranging from bioconjugation to polymer modification. Although click reactions are typically at least moderately fast (time scale of minutes to a few hours), in a reactive LAESI approach a substantial increase of reaction time is required for these reactions to occur. This increase was achieved using microdroplet chemistry and followed by MS using the insertion of a reaction tube - up to 1 m in length - between the LAESI source and the MS inlet, leading to near complete conversions due to significantly extended microdroplet lifetime. This novel approach allowed for the collection of kinetic data for a model (strain-promoted) click reaction between a substituted tetrazine and a strained alkyne and showed in addition excellent instrument stability, improved sensitivity, and applicability to other click reactions. Finally, the methodology was also demonstrated in a mass spectrometry imaging setting to show its feasibility in future imaging experiments.

Consumer-friendly food allergen detection : moving towards smartphone-based immunoassays
Ross, Georgina M.S. ; Bremer, Monique G.E.G. ; Nielen, Michel W.F. - \ 2018
Analytical and Bioanalytical Chemistry 410 (2018)22. - ISSN 1618-2642 - p. 5353 - 5371.
Citizen science - Consumer - Food allergen - Immunoassay - Multiplex - Smartphone
In this critical review, we provide a comprehensive overview of immunochemical food allergen assays and detectors in the context of their user-friendliness, through their connection to smartphones. Smartphone-based analysis is centered around citizen science, putting analysis into the hands of the consumer. Food allergies represent a significant worldwide health concern and consumers should be able to analyze their foods, whenever and wherever they are, for allergen presence. Owing to the need for a scientific background, traditional laboratory-based detection methods are generally unsuitable for the consumer. Therefore, it is important to develop simple, safe, and rapid assays that can be linked with smartphones as detectors to improve user accessibility. Smartphones make excellent detection systems because of their cameras, embedded flash functions, portability, connectivity, and affordability. Therefore, this review has summarized traditional laboratory-based methods for food allergen detection such as enzyme-linked-immunosorbent assay, flow cytometry, and surface plasmon resonance, and the potential to modernize these methods by interfacing them with a smartphone readout system, based on the aforementioned smartphone characteristics. This is the first review focusing on smartphone-based food-allergen detection methods designed with the intention of being consumer-friendly. [Figure not available: see fulltext.]
Effects of reduced intramammary antimicrobial use during the dry period on udder health in Dutch dairy herds
Vanhoudt, A. ; Hees-Huijps, K. van; Knegsel, A.T.M. van; Sampimon, O.C. ; Vernooij, J.C.M. ; Nielen, M. ; Werven, T. van - \ 2018
Journal of Dairy Science 101 (2018)4. - ISSN 0022-0302 - p. 3248 - 3260.
antimicrobial - dairy cow - dry period - selective dry cow therapy - udder health
Dry cow therapy (DCT) in the Netherlands changedfrom mainly blanket to selective antimicrobial DCT.This transition was supported by a national guideline,with the individual somatic cell count (SCC) at thelast milk recording before dry-off as the main selectioncriterion for antimicrobial DCT. The aim of this retrospectiveobservational study is to evaluate the SCCdynamics during the dry period at the herd and individualdry period level following the national transitionfrom mainly blanket to selective antimicrobial DCT.At the herd level, we used 2 data sets to evaluate theSCC dynamics during the dry period: (1) a nationaldata set containing 3,493 herds with data availablefrom 2011 through 2015 and (2) a veterinary practicedata set containing 280 herds with data available from2013 through 2015. The herd level analysis was carriedout using key performance indicators provided via milkrecording (CRV, Arnhem, the Netherlands): the percentageof cows that developed a new intramammaryinfection (IMI) during the dry period and the percentageof cows cured of an IMI during the dry period.The effect of DCT at individual dry period level wasanalyzed with a mixed-effects logistic regression modelbased on 4,404 dry periods from 2,638 cows in 20 herdswithin the veterinary practice data set. For these 20herds, individual SCC data from milk recordings andindividual cow DCT were available from 2013 through2015. No significant changes were observed to the SCCdynamics during the dry period at the herd level. Thepercentage of cows that developed a new IMI duringthe dry period ranged between 16 and 18%, and thepercentage of cows cured from an IMI during the dryperiod ranged between 74 and 76%. At the individual dry period level, a low SCC at the first milk recordingfollowing a dry period was associated with the use ofintramammary antimicrobial DCT with or without theconcurrent use of an intramammary teat sealer [oddsratio (OR) = 2.16 and OR = 2.07, respectively], the useof DCT with an intramammary teat sealer only (OR =1.35), and a low SCC at the last milk recording beforedry-off (OR = 1.78). This study demonstrates that theselection of cows for DCT without antimicrobials basedon SCC thresholds at the last milk recording is possiblewithout significant changes to udder health andreduced the use of antimicrobials.
Methods and means for determining treatment of subjects with exogenous somatotropin
Smits, N.G.E. ; Blokland, M.H. ; Nielen, M.W.F. - \ 2017
Octrooinummer: US2017354717, verleend: 2017-12-14.
Described are methods for determining whether a subject has been treated with exogenous somatotropin. The disclosure further relates to kits for determining whether a subject has been treated with exogenous somatotropin, and to the use of such kits for determining whether a subject has been treated with exogenous somatotropin.
Novel Selectivity-Based Forensic Toxicological Validation of a Paper Spray Mass Spectrometry Method for the Quantitative Determination of Eight Amphetamines in Whole Blood
Teunissen, Sebastiaan F. ; Fedick, Patrick W. ; Berendsen, Bjorn J.A. ; Nielen, Michel W.F. ; Eberlin, Marcos N. ; Graham Cooks, R. ; Asten, Arian C. van - \ 2017
Journal of the American Society for Mass Spectrometry 28 (2017)12. - ISSN 1044-0305 - p. 2665 - 2676.
Amphetamines - Forensic toxicology - Paper spray mass spectrometry - Selectivity - Validation - Whole blood
Paper spray tandem mass spectrometry is used to identify and quantify eight individual amphetamines in whole blood in 1.3 min. The method has been optimized and fully validated according to forensic toxicology guidelines, for the quantification of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-methylamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), para-methoxyamphetamine (PMA), para-methoxymethamphetamine (PMMA), and 4-fluoroamphetamine (4-FA). Additionally, a new concept of intrinsic and application-based selectivity is discussed, featuring increased confidence in the power to discriminate the amphetamines from other chemically similar compounds when applying an ambient mass spectrometric method without chromatographic separation. Accuracy was within ±15% and average precision was better than 15%, and better than 20% at the LLOQ. Detection limits between 15 and 50 ng/mL were obtained using only 12 μL of whole blood. [Figure not available: see fulltext.].
Mycotoxin profiling of 1000 beer samples with a special focus on craft beer
Peters, Jeroen ; Dam, Ruud van; Doorn, Ronald van; Katerere, David ; Berthiller, Franz ; Haasnoot, Willem ; Nielen, Michel W.F. - \ 2017
PLoS One 12 (2017)10. - ISSN 1932-6203 - 27 p.

Currently beer is booming, mainly due to the steady rise of craft breweries worldwide. Previous surveys for occurrence of mycotoxins in beer, were mainly focussed on industrial produced beer. The present survey reports the presence of mycotoxins in craft beer and how this compares to industrial produced beer. More than 1000 beers were collected from 47 countries, of which 60% were craft beers. A selection of 1000 samples were screened for the presence of aflatoxin B1, ochratoxin A (OTA), zearalenone (ZEN), fumonisins (FBs), T-2 and HT-2 toxins (T-2 and HT-2) and deoxynivalenol (DON) using a mycotoxin 6-plex immunoassay. For confirmatory analysis, a liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and applied. The 6-plex screening showed discrepancies with the LC-MS/MS analysis, possibly due to matrix interference and/or the presence of unknown mycotoxin metabolites. The major mycotoxins detected were DON and its plant metabolite deoxynivalenol-3-β-D-glucopyranoside (D3G). The 6-plex immunoassay reported the sum of DON and D3G (DON+D3G) contaminations ranging from 10 to 475 μg/ L in 406 beers, of which 73% were craft beers. The popular craft beer style imperial stout, had the highest percentage of samples suspected positive (83%) with 29% of all imperial stout beers having DON+D3G contaminations above 100 μg/L. LC-MS/MS analysis showed that industrial pale lagers from Italy and Spain, predominantly contained FBs (3-69 μg/L). Besides FBs, African traditional beers also contained aflatoxins (0.1-1.2 μg/L). The presence of OTA, T-2, HT-2, ZEN, β-zearalenol, 3/15-acetyl-DON, nivalenol and the conjugated mycotoxin zearalenone 14-sulfate were confirmed in some beers. This study shows that in 27 craft beers, DON+D3G concentrations occurred above (or at) the Tolerable Daily Intake (TDI). Exceeding the TDI, may have a health impact. A better control of brewing malts for craft beer, should be put in place to circumvent this potential problem.

Gas chromatographic quadrupole time-of-flight full scan high resolution mass spectrometric screening of human urine in antidoping analysis
Abushareeda, Wadha ; Lyris, Emmanouil ; Kraiem, Suhail ; Wahaibi, Aisha Al ; Alyazidi, Sameera ; Dbes, Najib ; Lommen, Arjen ; Nielen, Michel ; Horvatovich, Peter L. ; Alsayrafi, Mohammed ; Georgakopoulos, Costas - \ 2017
Journal of Chromatography. B, Analytical technologies in the biomedical and life sciences 1063 (2017). - ISSN 1570-0232 - p. 74 - 83.
Anabolic steroids - Full scan high resolution - Gas chromatography - Human urine - Mass spectrometry

This paper presents the development and validation of a high-resolution full scan (FS) electron impact ionization (EI) gas chromatography coupled to quadrupole Time-of-Flight mass spectrometry (GC/QTOF) platform for screening anabolic androgenic steroids (AAS) in human urine samples. The World Antidoping Agency (WADA) enlists AAS as prohibited doping agents in sports, and our method has been developed to comply with the qualitative specifications of WADA to be applied for the detection of sports antidoping prohibited substances, mainly for AAS. The method also comprises of the quantitative analysis of the WADA's Athlete Biological Passport (ABP) endogenous steroidal parameters. The applied preparation of urine samples includes enzymatic hydrolysis for the cleavage of the Phase II glucuronide conjugates, generic liquid–liquid extraction and trimethylsilyl (TMS) derivatization steps. Tandem mass spectrometry (MS/MS) acquisition was applied on few selected ions to enhance the specificity and sensitivity of GC/TOF signal of few compounds. The full scan high resolution acquisition of analytical signal, for known and unknown TMS derivatives of AAS provides the antidoping system with a new analytical tool for the detection designer drugs and novel metabolites, which prolongs the AAS detection, after electronic data files’ reprocessing. The current method is complementary to the respective liquid chromatography coupled to mass spectrometry (LC/MS) methodology widely used to detect prohibited molecules in sport, which cannot be efficiently ionized with atmospheric pressure ionization interface.

The utility of sensor technology to support reproductive management on dairy farms
Rutten, C.J. - \ 2017
University. Promotor(en): Henk Hogeveen; Michel Nielen, co-promotor(en): Wilma Steeneveld. - Wageningen : Wageningen University - ISBN 9789463431934 - 232
dairy cattle - dairy farms - sensors - reproduction - reproductive behaviour - animal health - calving - activity - management - dairy farming - technology - agricultural economics - melkvee - melkveebedrijven - voortplanting - voortplantingsgedrag - diergezondheid - kalven - activiteit - bedrijfsvoering - melkveehouderij - technologie - agrarische economie

Since the 1980s, efforts have been made to develop sensors that measure a parameter from an individual cow. The development started with individual cow recognition and was followed by sensors that measure the electrical conductivity of milk and pedometers that measure activity. Some sensors like activity meters, electrical conductivity, weight floors and somatic cell count sensors are commercially available. Adoption has in general been low and mainly driven by the AMS, with a clear exception for estrus detection. In practice, the economic benefits of using sensor systems has not been proven. So, to make sensors live up to their full potential there is a need for research to shift from technical development towards practical applications and integration with operational farm management. Estrus detection sensors can have a good detection performance and are currently applied by farmers in practice, therefore this thesis focusses on sensors that support reproductive management. The main objective of this thesis is to study the utility of sensor technology to support reproductive management on dairy farms. This main objective was split in five sub objectives that each study a part of the main objective and were discussed in the separate chapters of this thesis.

We demonstrated that utility of sensors for reproductive management can be found in economic benefits (estrus and calving detection), reduction of labor (calving and estrus detection) and more detailed management information (prognosis of insemination success). So, automated estrus detection aids reproductive management.

From this thesis the following conclusions can be drawn:

The developed theoretical framework describes four levels of sensor development, which should all be included in proper development of sensor systems. The literature review showed that no studies developed sensor systems with regard to management and decision support.

It was possible to improve the prediction of the start of calving compared to a model that only uses the expected calving date. However, predicting the start of calving within an hour was not possible with a high sensitivity and specificity.

There was financial merit in the use of calving detection, because the sensor system enables more timely intervention by the farmer. The uncertainty about the positive effects was large, which caused a wide range in the simulated financial benefits.

Investment in a sensor for estrus detection was on average profitable with a return on investment of 11%. Profitability was influenced most by the heuristic culling rules and the expected increase of the estrus detection rate between detection by visual observation and the sensor.

Routinely collected farm data can be used to estimate a prognosis on insemination success and be used to determine whether an individual cow has a higher or lower than average likelihood of insemination success. Integration of this prognostic model with an estrus detection sensor has potential.

Currently farmers only adopt sensors for estrus detection or because they were standard with an AMS. A reason for this is that sensor systems do not produce clear information for farmers. Sensor technology should be focused on management support of applications. Labor benefits of sensors are important for adoption of sensors by farmers, farmers value flexibility, increased family time and less physical workload as benefits. However, economic evaluations of technical solutions are unable to quantify these benefits. Sensor research should consider the preference of farmers regarding labor. For the appraisal of sensor technology new methods to value labor benefits of sensor are needed. Furthermore, in sensor development societal acceptance should be an important consideration. Animal rights activists may frame the use of sensors as a form of industrialized farming. Only using technical arguments and considerations to explain the benefits of sensors will hamper the societal acceptance of modern dairy farming. Application of sensors on dairy farms should be communicated smartly to society in terms that relate the values of citizens.

Multiple heart-cutting two dimensional liquid chromatography quadrupole time-of-flight mass spectrometry of pyrrolizidine alkaloids
Schans, Milou G.M. van de; Blokland, Marco H. ; Zoontjes, Paul W. ; Mulder, Patrick P.J. ; Nielen, Michel W.F. - \ 2017
Journal of Chromatography. A, Including electrophoresis and other separation methods 1503 (2017). - ISSN 0021-9673 - p. 38 - 48.
Isomeric pyrrolizidine alkaloids - Mass spectrometry - Multiple heart-cutting 2D-LC - Two dimensional liquid chromatography

Pyrrolizidine alkaloids (PAs) and their and the corresponding N-oxides (PAs-ox) are genotoxic plant metabolites which can be present as unwanted contaminants in food products of herbal origin like tea and food supplements. PAs and PAs-ox come in a wide variety of molecular structures including many structural isomers. For toxicity assessment it is important to determine the composition of a sample and to resolve all isomeric PAs and PAs-ox, which is currently not possible in one liquid or gas chromatographic (LC or GC) run. In this study an online two dimensional liquid chromatography quadrupole time-of-flight mass spectrometry (2D-LC QToF-MS) method was developed to resolve isomeric PAs and PAs-ox. After comprehensive column and mobile phase selection a polar endcapped C18 column was used at pH 3 in the first dimension, and a cross-linked C18 column at pH 10 in the second dimension. Injection solvents, column IDs, flow rates and temperatures were carefully optimized. The method with column selection valve switching described in this study was able to resolve and visualize 20 individual PAs/PAs-ox (6 sets of isomers) in one 2D-LC QToF-MS run. Moreover, it was shown that all isomeric PAs/PAs-ox could be unambiguously annotated. The method was shown to be applicable for the determination and quantification of isomeric PAs/PAs-ox in plant extracts and could be easily extended to include other PAs and PAs-ox.

Ambient characterization of synthetic fibers by laser ablation electrospray ionization mass spectrometry
Geenen, F.A.M.G. van; Franssen, M.C.R. ; Schotman, A.H.M. ; Zuilhof, H. ; Nielen, M.W.F. - \ 2017
Analytical Chemistry 89 (2017). - ISSN 0003-2700 - p. 4031 - 4037.
Direct analysis of synthetic fibers under ambient
conditions is highly desired to identify the polymer, the finishes
applied and irregularities that may compromise its performance
and value. In this paper, laser ablation electrospray ionization
ion mobility time-of-flight mass spectrometry (LAESI-IMSTOF-
MS) was used for the analysis of synthetic polymers and
fibers. The key to this analysis was the absorption of laser light
by aliphatic and aromatic nitrogen functionalities in the
polymers. Analysis of polyamide (PA) 6, 46, 66, and 12 pellets
and PA 6, 66, polyaramid and M5 fibers yielded characteristic
fragment ions without any sample pretreatment, enabling their
unambiguous identification. Synthetic fibers are, in addition,
commonly covered with a surface layer for improved adhesion
and processing. The same setup, but operated in a transient infrared matrix-assisted laser desorption electrospray ionization (IRMALDESI)
mode, allowed the detailed characterization of the fiber finish layer and the underlying polymer. Differences in finish
layer distribution may cause variations in local properties of synthetic fibers. Here we also show the feasibility of mass
spectrometry imaging (MSI) of the distribution of a finish layer on the synthetic fiber and the successful detection of local surface
Biochip spray: simplified coupling of surface plasmon resonance biosensing and mass spectrometry
Joshi, S. ; Zuilhof, H. ; Beek, T.A. van; Nielen, M.W.F. - \ 2017
Analytical Chemistry 89 (2017)3. - ISSN 0003-2700 - p. 1427 - 1432.
A simplified coupling of surface plasmon resonance (SPR) immuno-biosensing with ambient ionization mass spectrometry (MS) was developed. It combines two orthogonal analysis techniques: the biosensing capability of SPR and the chemical identification power of high resolution MS. As a proof-of-principle, deoxynivalenol (DON), an important mycotoxin, was captured using an SPR gold chip containing an antifouling layer and monoclonal antibodies against the toxin and, after washing, the chip could be taken out and analyzed by direct spray MS of the biosensor chip to confirm the identity of DON. Furthermore, cross-reacting conjugates of DON present in a naturally contaminated beer could be successfully identified, thus showing the potential of rapid identification of (un)expected cross-reacting molecules.
A global inter-laboratory study to assess acquisition modes for multi-compound confirmatory analysis of veterinary drugs using liquid chromatography coupled to triple quadrupole, time of flight and orbitrap mass spectrometry
Berendsen, Bjorn J.A. ; Meijer, Thijs ; Mol, Hans G.J. ; Ginkel, Leen van; Nielen, Michel W.F. - \ 2017
Analytica Chimica Acta 962 (2017). - ISSN 0003-2670 - p. 60 - 72.
Inter-laboratory study - Liquid chromatography - Mass spectrometry - Performance criteria - Veterinary drugs residue analysis

According to EU legislation a confirmatory method used for residue analysis should be able to confirm the identity of a compound beyond reasonable doubt. To provide an adequate instrumental set-up, Commission Decision 2002/657/EC introduced the concept of "identification points". A second aspect to assure unequivocal confirmation, is the establishment of ion ratio and retention time criteria. Currently, the gold standard for confirmatory analysis of most veterinary drug residues is liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS) in selected reaction monitoring (SRM) acquisition mode, isolating one precursor ion and monitoring two a priori selected product ions, yielding 4 identification points. We comprehensively evaluated the use of different low and high resolution LC-MS(/MS) techniques and acquisition modes with respect to the selectivity of 100 veterinary drugs in liver, muscle and urine extracts aiming to critically review the currently established identification points system. A comparison among MS/MS in SRM mode with high resolution mass spectrometry (HRMS) in full scan, all ion fragmentation and targeted MS/MS was made based on a unique inter-laboratory study, which comprises 21 laboratories from four different continents and equipment from all major vendors.In total 186 samples were analysed yielding results for 9282 analyte/matrix combinations. It was observed that the false positive rate approximately doubles if no ion ratio criterion is applied indicating that this criterion is important to prevent false positive results. Full scan HRMS analysis, only monitoring the molecular ion and allowing a ±5 ppm mass tolerance is, in general, less selective than low resolution MS/MS using SRM, and thus full scan alone is considered not sufficient for confirmatory analysis. Furthermore, even though the number of data on all ion fragmentation and targeted MS/MS at high resolution was limited, based on the data obtained, it was observed that the acquisition mode as well as the mass resolution needed, very much depend on the matrix and the compound itself. For complex matrix extracts and non-selective compounds (worst-case situation), only targeted MS/MS, monitoring the precursor ion and a single product ion in HR-MS using a maximum of ±5 ppm mass deviation, leads to comparable selectivity and false positive and negative rate as SRM monitoring two product ions in LR-MS. We conclude that the currently applied identification point system as established in commission decision 2002/657/EC should be revised with respect to the allocation of identification points.

Nanostructured imaging surface plasmon resonance biosensing
Joshi, Sweccha - \ 2017
University. Promotor(en): Michel Nielen; Han Zuilhof, co-promotor(en): Teris van Beek. - Wageningen : Wageningen University - ISBN 9789463430203 - 164
methodology - techniques - biosensors - resonance - mass spectrometry - organic chemistry - physics - methodologie - technieken - biosensoren - resonantie - massaspectrometrie - organische scheikunde - fysica

The testing and further development of a prototype nanostructured imaging surface plasmon resonance (iSPR) biosensor, with a focus on surface modification and detailed characterization of the biosensor chip and in-field and at-line applicability in the food industry is described. Furthermore, a simplified coupling of SPR and MS is described that allows identification of the mycotoxins of interest along with any other cross-reacting analytes. Chapter 1 describes general information about SPR, SPR instruments along with their components, development of a multiplex SPR biosensor and coupling of SPR to mass spectrometry.

In Chapter 2, the surface modification, in-depth characterization and the antifouling performance of the nanostructured iSPR chip is described. Different types of polyethylene glycol (PEG) and zwitterionic polymers were chosen as antifouling chemistries. Various surface characterization techniques such as atomic force microscopy, scanning electron microscopy, water contact angle, X-ray photoelectron spectroscopy and direct analysis in real time high resolution mass spectrometry provided complementary information about the chip before and after the modification. Antifouling chemistry, an essential first step in the development of an SPR biosensor, prevents false positive results arising from non-specific binding of sample components to the SPR chip. Upon comparison of the surface modification and antifouling behavior with conventional flat SPR chips, the latter were only slightly better. Zwitterionic polymers and long chain PEG had the best antifouling performance. A proof-of-principle experiment was done to demonstrate the selective detection of streptavidin binding to a surface partially modified with biotin.

A 6-plex SPR assay for the detection of mycotoxins in barley was developed in Chapter 3. A benchmark double 3-plex assay was developed for the detection of deoxynivalenol (DON), zearalenone (ZEA), T-2 toxin (T-2), ochratoxin A (OTA), fumonisin B1 (FB1) and aflatoxin B1 (AFB1) using benchtop SPR instrument (Biacore). Preliminary in-house validation of the competitive inhibition assay developed using ovalbumin conjugates of the mycotoxins showed that the method is suitable for detection of DON, ZEA, T-2 and FB1 whereas further improvement is required for OTA and AFB1. The method was then transferred to the nanostructured iSPR, which although less sensitive than the benchtop SPR, was able to detect DON, T-2, ZEA and FB1 at the relevant levels.

In Chapter 4, the assay developed in Chapter 3 was further optimized and an entire assay along with in-house validation and measurement of naturally contaminated was developed using the nanostructured iSPR. The antifouling chemistry used in Chapter 3, PEG, was replaced by carboxymethylated dextran (CMD) that not only allowed direct immobilization of toxins but also helped to improve the stability of the chip whereby the chip could be used for more than 450 cycles. DON could be detected at the relevant levels in beer with minimal sample preparation whereas for OTA an enrichment step using solid phase extraction was required.

As demonstrated in Chapter 3 and 4, the nanostructured iSPR instrument can be used for screening of different mycotoxins in beer and related ingredients. However, SPR is not able to provide chemical information of the binding analyte especially in cases where the antibodies have cross-reactivity towards conjugates of the analyte. Therefore, a simplified coupling for SPR with ambient mass spectrometry was developed in Chapter 5. The method allowed identification of DON as well as its cross-reacting conjugates such as deoxynivalenol-3-glucoside and 3-acetyl DON.

The research presented in this thesis is an important step towards the use of the nanostructured iSPR instrument for label free in-field and at-line detection of various analytes. In Chapter 6, discussion of the main achievements of this thesis, challenges and future perspectives of the technology is described.

Sensor data on cow activity, rumination, and ear temperature improve prediction of the start of calving in dairy cows
Rutten, C.J. ; Kamphuis, C. ; Hogeveen, H. ; Huijps, K. ; Nielen, M. ; Steeneveld, W. - \ 2017
Computers and Electronics in Agriculture 132 (2017). - ISSN 0168-1699 - p. 108 - 118.
Calving management - Dairy farming - Wearable sensors

Management during calving is important for the health and survival of dairy cows and their calves. Although the expected calving date is known, this information is imprecise and farmers still have to check a cow regularly to identify when it starts calving. A sensor system that predicts the moment of calving could help farmers efficiently check cows for calving. Observation of a cow prior to calving is important because dystocia can occur, which requires timely intervention to mitigate adverse effects on both cow and calf. In this study, 400 cows on a Dutch dairy farm were equipped with sensors. The sensor was a single device in an ear tag, which synthesised cumulative activity, rumination activity, feeding activity, and temperature on an hourly basis. Data were collected during a one-year period. During this period, the starting moment of 417 calvings was recorded using camera images of the calving pen taken every 5 min. In total, 114 calving moments could be linked with sensor data. The moment at which calving started was defined as the first camera snapshot with visible evidence that the cow was having contractions or had started labor. Two logit models were developed: a model with the expected calving date as independent variable and a model with additional independent variables based on sensor data. The areas under the curves of the Receiver Operating Characteristic were 0.885 and 0.929 for these models, respectively. The model with expected calving date only had a sensitivity of 9.1%, whereas the model with additional sensor data has a sensitivity of 36.4%, both with a fixed false positive rate of 1%. Results indicate that the inclusion of sensor data improves the prediction of the start of calving; therefore the sensor data has value for the prediction of the moment of calving. The model with the expected calving date and sensor data had a sensitivity of 21.2% at a one-hour time window and 42.4% at a three-hour time window, both with a false positive rate of 1%. This indicates that prediction of the specific hour in which calving started was not possible with a high accuracy. The inclusion of sensor data improves the accuracy of a prediction of the start of calving, compared to a prediction based only on the expected calving date. Farmers can use the alerts of the predictive model as an indication that cows should be supervised more closely in the next hours.

Analysis of Mycotoxins in Beer Using a Portable Nanostructured Imaging Surface Plasmon Resonance Biosensor
Joshi, Sweccha ; Annida, Rumaisha M. ; Zuilhof, Han ; Beek, Teris A. van; Nielen, Michel W.F. - \ 2016
Journal of Agricultural and Food Chemistry 64 (2016)43. - ISSN 0021-8561 - p. 8263 - 8271.
beer - deoxynivalenol - imaging SPR - mycotoxins - nanoplasmonics - ochratoxin A

A competitive inhibition immunoassay is described for the mycotoxins deoxynivalenol (DON) and ochratoxin A (OTA) in beer using a portable nanostructured imaging surface plasmon resonance (iSPR) biosensor, also referred to as imaging nanoplasmonics. The toxins were directly and covalently immobilized on a 3-dimensional carboxymethylated dextran (CMD) layer on a nanostructured iSPR chip. The assay is based on competition between the immobilized mycotoxins and free mycotoxins in the solution for binding to specific antibodies. The chip surface was regenerated after each cycle, and the combination of CMD and direct immobilization of toxins allowed the chips to be used for more than 450 cycles. The limits of detection (LODs) in beer were 17 ng/mL for DON and 7 ng/mL for OTA (or 0.09 ng/mL after 75 times enrichment). These LODs allowed detection of even less than 10% depletion of the tolerable daily intake of DON and OTA by beer. Significant cross-reactivity of anti-DON was observed toward DON-3-glucoside and 3-acetyl-DON, while no cross-reactivity was seen for 15-acetyl-DON. A preliminary in-house validation with 20 different batches of beer showed that both toxins can be detected at the considered theoretical safe level for beer. The assay can be used for in-field or at-line detection of DON in beer and also in barley without preconcentration, while OTA in beer requires an additional enrichment step, thus making the latter in its present form less suitable for field applications.

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