Assessment of the potential vaping-related exposure to carbonyls and epoxides using stable isotope-labeled precursors in the e-liquid

The formation of carbonyls and epoxides in e-cigarette (EC) aerosol is possible due to heating of the liquid constituents. However, high background levels of these compounds have inhibited a clear assessment of exposure during use of ECs. An EC containing an e-liquid replaced with 10% of ¹³C-labeled propylene glycol and glycerol was used in a controlled use clinical study with 20 EC users. In addition, five smokers smoked cigarettes spiked with the described e-liquid. Seven carbonyls (formaldehyde, acetaldehyde, acrolein, acetone, crotonaldehyde, methacrolein, propionaldehyde) were measured in the aerosol and the mainstream smoke. Corresponding biomarkers of exposure were determined in the user’s urine samples. ¹³C-labeled formaldehyde, acetaldehyde and acrolein were found in EC aerosol, while all seven labeled carbonyls were detected in smoke. The labeled biomarkers of exposure to formaldehyde (¹³C-thiazolidine carboxylic acid and ¹³C-N-(1,3-thiazolidine-4-carbonyl)glycine), acrolein (¹³C₃-3-hydroxypropylmercapturic acid) and glycidol (¹³C₃-dihydroxypropylmercapturic acid) were present in the urine of vapers indicating an EC use-specific exposure to these toxicants. However, other sources than vaping contribute to a much higher extent by several orders of magnitude to the overall exposure of these toxicants. Comparing data for the native (unlabeled) and the labeled (exposure-specific) biomarkers revealed vaping as a minor source of user’s exposure to these toxicants while other carbonyls and epoxides were not detectable in the EC aerosol.

Ultrasensitive and Simultaneous SERS Detection of Multiplex MicroRNA Using Fractal Gold Nanotags for Early Diagnosis and Prognosis of Hepatocellular Carcinoma

Sensitive and simultaneous detection of multiple cancer-related biomarkers in serum is essential for diagnosis, therapy, prognosis, and staging of cancer. Herein, we proposed a magnetically assisted sandwich-type surface-enhanced Raman scattering (SERS)-based biosensor for ultrasensitive and multiplex detection of three hepatocellular carcinoma-related microRNA (miRNA) biomarkers. The biosensor consists of an SERS tag (probe DNA-conjugated DNA-engineered fractal gold nanoparticles, F-AuNPs) and a magnetic capture substrate (capture DNA-conjugated Ag-coated magnetic nanoparticles, AgMNPs). The proposed strategy achieved simultaneous and sensitive detection of three miRNAs (miRNA-122, miRNA-223, and miRNA-21), and the limits of detection of the three miRNAs in human serum are 349 aM for miRNA-122, 374 aM for miRNA-223, and 311 aM for miRNA-21. High selectivity and accuracy of the SERS biosensor were proved by practical analysis in human serum. Moreover, the biosensor exhibited good practicability in multiplex detection of three miRNAs in 92 clinical sera from AFP-negative patients, patients before and after hepatectomy, recurred and relapse-free patients after hepatectomy, and hepatocellular carcinoma patients at distinct Barcelona clinic liver cancer stages. The experiment results demonstrate that our SERS-based assay is a promising candidate in clinical application and exhibited potential for the prediction, diagnosis, monitoring, and staging of cancers.

Quantitative detection of human adenovirus from river water by monolithic adsorption filtration and quantitative PCR

Water contaminated with fecally derived viruses, also known as enteric viruses, represents a particularly high risk for human health. However, they have not been included in water quality regulations yet. The detection of these viruses is often more expensive and time-consuming compared to the analysis of conventional fecal indicator organisms. In addition, most methods are not sensitive enough to detect small viral loads that may already cause serious health issues if present in water. In this study, we established a workflow for the successful and direct enrichment of human adenovirus (HAdV) from artificially contaminated river water based on monolithic adsorption filtration (MAF) and quantitative polymerase reaction (qPCR). With a clear focus on efficiency, we used targeted synthetic DNA fragments as standard for the quantification of HAdV by qPCR, leading to accurate and robust results with a qPCR efficiency of 95 %, a broad working range over 6 orders of magnitude and an LOD of 1 GU/μL. We carried out a cascade of spiking experiments, enhancing the complexity of the spiking matrix with each step to progressively evaluate MAF for the direct concentration of HAdV. We found that negatively charged MAF using monoliths with hydroxyl groups (MAF-OH) showed a better reproducibility and a significantly faster turnaround time than skimmed milk flocculation (SMF) when concentrating HAdV35 from artificially contaminated, acidified mineral water. We then validated positively charged MAF using monoliths with diethyl aminoethyl groups (MAF-DEAE) for the direct concentration of HAdV5 without pre-conditioning of water samples using tap water as spiking matrix with a less defined and controlled water chemistry. Finally, we evaluated MAF-DEAE for the direct concentration of HAdV5 from surface water using river water as representative matrix with an undefined water chemistry. We found, that MAF-DEAE achieved reproducible recoveries of HAdV5, independently of the spiked concentration level or sample volume. Furthermore, we showed, that MAF-DEAE drastically reduced the limit of detection (LOD) of HAdV5 by a factor of 115 from 6.0 ∙ 10³ GU/mL before to 5.2 ∙ 10¹ GU/mL after MAF-DEAE. We identified that recoveries increased for smaller processing volumes with a peak at 0.5 L of 84.0 % and showed that recovery efficiency depends on sample volume and matrix type. The here presented workflow based on MAF-DEAE and qPCR offers an easy-to-implement and highly efficient alternative to existing approaches and allows for a fast detection of HAdV in water.

Bacteria Detection: From Powerful SERS to Its Advanced Compatible Techniques

The rapid, highly sensitive, and accurate detection of bacteria is the focus of various fields, especially food safety and public health. Surface-enhanced Raman spectroscopy (SERS), with the advantages of being fast, sensitive, and nondestructive, can be used to directly obtain molecular fingerprint information, as well as for the on-line qualitative analysis of multicomponent samples. It has therefore become an effective technique for bacterial detection. Within this progress report, advances in the detection of bacteria using SERS and other compatible techniques are discussed in order to summarize its development in recent years. First, the enhancement principle and mechanism of SERS technology are briefly overviewed. The second part is devoted to a label-free strategy for the detection of bacterial cells and bacterial metabolites. In this section, important considerations that must be made to improve bacterial SERS signals are discussed. Then, the label-based SERS strategy involves the design strategy of SERS tags, the immunomagnetic separation of SERS tags, and the capture of bacteria from solution and dye-labeled SERS primers. In the third part, several novel SERS compatible technologies and applications in clinical and food safety are introduced. In the final part, the results achieved are summarized and future perspectives are proposed.

A novel quantification method for sulfur-containing biomarkers of formaldehyde and acetaldehyde exposure in human urine and plasma samples

A novel method for the quantification of the sulfur-containing metabolites of formaldehyde (thiazolidine carboxylic acid (TCA) and thiazolidine carbonyl glycine (TCG)) and acetaldehyde (methyl thiazolidine carboxylic acid (MTCA) and methyl thiazolidine carbonyl glycine (MTCG)) was developed and validated for human urine and plasma samples. Targeting the sulfur-containing metabolites of formaldehyde and acetaldehyde in contrast to the commonly used biomarkers formate and acetate overcomes the high intra- and inter-individual variance. Due to their involvement in various endogenous processes, formate and acetate lack the required specificity for assessing the exposure to formaldehyde and acetaldehyde, respectively. Validation was successfully performed according to FDA's Guideline for Bioanalytical Method Validation (2018), showing excellent performance with regard to accuracy, precision, and limits of quantification (LLOQ). TCA, TCG, and MTCG proved to be stable under all investigated conditions, whereas MTCA showed a depletion after 21 months. The method was applied to a set of pilot samples derived from smokers who consumed unfiltered cigarettes spiked with ¹³C-labeled propylene glycol and ¹³C-labeled glycerol. These compounds were used as potential precursors for the formation of ¹³C-formaldehyde and ¹³C-acetaldehyde during combustion. Plasma concentrations were significantly lower as compared to urine, suggesting urine as suitable matrix for a biomonitoring. A smoking-related increase of unlabeled biomarker concentrations could not be shown due to the ubiquitous distribution in the environment. While the metabolites of ¹³C-acetaldehyde were not detected, the described method allowed for the quantification of ¹³C-formaldehyde uptake from cigarette smoking by targeting the biomarkers ¹³C-TCA and ¹³C-TCG in urine.Graphical abstract.

TUM-ParticleTyper: A detection and quantification tool for automated analysis of (Microplastic) particles and fibers

TUM-ParticleTyper is a novel program for the automated detection, quantification and morphological characterization of fragments, including particles and fibers, in images from optical, fluorescence and electron microscopy (SEM). It can be used to automatically select targets for subsequent chemical analysis, e.g., Raman microscopy, or any other single particle identification method. The program was specifically developed and validated for the analysis of microplastic particles on gold coated polycarbonate filters. Our method development was supported by the design of a filter holder that minimizes filter roughness and facilitates enhanced focusing for better images and Raman measurements. The TUM-ParticleTyper software is tunable to the user's specific sample demands and can extract the morphological characteristics of detected objects (coordinates, Feret's diameter min / max, area and shape). Results are saved in csv-format and contours of detected objects are displayed as an overlay on the original image. Additionally, the program can stitch a set of images to create a full image out of several smaller ones. An additional useful feature is the inclusion of a statistical process to calculate the minimum number of particles that must be chemically identified to be representative of all particles localized on the substrate. The program performance was evaluated on genuine microplastic samples. The TUM-ParticleTyper software localizes particles using an adaptive threshold with results comparable to the "gold standard" method (manual localization by an expert) and surpasses the commonly used Otsu thresholding by doubling the rate of true positive localizations. This enables the analysis of a statistically significant number of particles on the filter selected by random sampling, measured via single point approach. This extreme reduction in measurement points was validated by comparison to chemical imaging, applying both procedures to the same area at comparable processing times. The single point approach was both faster and more accurate proving the applicability of the presented program.

Nanoplastic Analysis by Online Coupling of Raman Microscopy and Field-Flow Fractionation Enabled by Optical Tweezers

Nanoplastic pollution is an emerging environmental concern, but current analytical approaches are facing limitations in this size range. However, the coupling of nanoparticle separation with chemical characterization bears potential to close this gap. Here, we realize the hyphenation of particle separation/characterization (field-flow fractionation (FFF), UV, and multiangle light scattering) with subsequent chemical identification by online Raman microspectroscopy (RM). The problem of low Raman scattering was overcome by trapping particles with 2D optical tweezers. This setup enabled RM to identify particles of different materials (polymers and inorganic) in the size range from 200 nm to 5 μm, with concentrations in the order of 1 mg/L (10⁹ particles L^-1). The hyphenation was realized for asymmetric flow FFF and centrifugal FFF, which separate particles on the basis of different properties. This technique shows potential for application in nanoplastic analysis, as well as many other fields of nanomaterial characterization.

Nondestructive Chemical Analysis of the Iron-Containing Protein Ferritin Using Raman Microspectroscopy

Ferritin is a ubiquitous intracellular iron storage protein of animals, plants, and bacteria. The cavity of this protein acts like a reaction chamber for natural formation and storage of nano-sized particles via biomineralization. Knowledge of the chemical composition and structure of the iron core is highly warranted in the fields of nano technologies as well as biomolecules and medicine. Here, we show that Raman microspectroscopy (RM) is a suitable nondestructive approach for an analysis of proteins containing such nano-sized iron oxides. Our approach addresses: (1) synthesis of suitable reference materials, i.e., ferrihydrite, maghemite and magnetite nanoparticles; (2) optimization of parameters for Raman spectroscopic analysis; (3) comparison of Raman spectra from ferritin with apoferritin and our reference minerals; and (4) validation of Raman analysis by X-ray diffraction and Mössbauer spectroscopy as two independent complementary approaches. Our results reveal that the iron core of natural ferritin is composed of the iron(III) hydroxide ferrihydrite (Fe₂O₃ ∙ 0.5 H₂O).

Flow-based regenerable chemiluminescence receptor assay for the detection of tetracyclines

For the first time, a flow-based regenerable chemiluminescence receptor assay is established that is eminently suited as screening method for the detection of widely used tetracyclines (TCs) in environmental and food samples. The complex functionality and high reactivity of TCs complicate the creation of immunogens which is currently the bottleneck for developing sensitive immunoassays. In this case, competitive bioreceptor assays for the analysis of small organic molecules are preferable and, moreover, flow-based regenerable bioassays are optimally suited for automated analysis applications. Therefore, the solution for rapid and sensitive analysis of TCs is the regenerable CL receptor assay with a covalently immobilized DNA oligonucleotide containing the specific operator sequence tetO to which the repressor protein TetR binds only in the absence of TCs. The TC measurements are performed on the CL microarray analysis platform MCR 3 within 30 min per sample. The LoD in spiked tap water was determined to be 0.1 μg L⁻¹, and for 1 μg L⁻¹ TET, recoveries of 77% ± 16% were obtained. Due to the stability of the immobilized DNA oligonucleotide and the resulting regenerability of the assay for various measurements, the new method is highly cost- and resource-efficient and ideally suited for the monitoring of environmental samples in the field.

Microcystin-LR Enrichment from Freshwater by a Recombinant Plant-derived Antibody Using Sol-Gel-Glass Immunoextraction

Eutrophication of water bodies can promote cyanobacterial (blue-green algae) blooms, which has become a source of increasing concern for both recreational and drinking water use. Many bacterial species can produce toxins that pose threats to wildlife, domestic animals and humans. Microcystin-leucine-arginine (MC-LR) is the most frequent and most toxic microcystin congener. For the first time, lab-scale investigations were performed to test the application of a recombinant plant-derived anti-MC-LR antibody immobilized on an immunoaffinity support material to selectively extract the toxin from spiked freshwater samples. As a comparison, its hybridoma-derived counterpart (murine monoclonal antibody) was evaluated. The antibody-doped material was prepared via an optimized sol-gel process; its stability and binding efficiency of MC-LR in spiked freshwater samples were thoroughly tested using the ELISA and orthogonal LC-MS methods. For removal, two column-based procedures with sequential or continuous cyclic sample addition and a suspension mode (moving adsorbent) were tested. Noteworthy the results obtained with a crude antibody fraction were fully compatible with the highly purified preparation. This study paves the way for further investigation being focused on novel applications of plant-derived anti-MC-LR antibodies in bioremediation to selectively deplete the toxin from freshwater: a green and promising technology without secondary pollution.

Surface-enhanced Raman spectroscopy of microorganisms: limitations and applicability on the single-cell level

Detection and characterization of microorganisms is essential for both clinical diagnostics and environmental studies. An emerging technique to analyse microbes at single-cell resolution is surface-enhanced Raman spectroscopy (surface-enhanced Raman scattering: SERS). Optimised SERS procedures enable fast analytical read-outs with specific molecular information, providing insight into the chemical composition of microbiological samples. Knowledge about the origin of microbial SERS signals and parameter(s) affecting their occurrence, intensity and/or reproducibility is crucial for reliable SERS-based analyses. In this work, we explore the feasibility and limitations of the SERS approach for characterizing microbial cells and investigate the applicability of SERS for single-cell sorting as well as for three-dimensional visualization of microbial communities. Analyses of six different microbial species (an archaeon, two Gram-positive bacteria, three Gram-negative bacteria) showed that for several of these organisms distinct features in their SERS spectra were lacking. As additional confounding factor, the physiological conditions of the cells (as influenced by e.g., storage conditions or deuterium-labelling) were systematically addressed, for which we conclude that the respective SERS signal at the single-cell level is strongly influenced by the metabolic activity of the analysed cells. While this finding complicates the interpretation of SERS data, it may on the other hand enable probing of the metabolic state of individual cells within microbial populations of interest.

Palindromic Molecular Beacon Based Z-Scheme BiOCl-Au-CdS Photoelectrochemical Biodetection

This work presented an innovative and rationally engineered palindromic molecular beacon (PMB) based "Z-scheme" photoelectrochemical (PEC) biosensing protocol for the selective screening of kanamycin (Kana) through DNA hybridization-induced conformational conversion. Interestingly, the ingeniously designed PMB integrated the multifunctional elements including recognition region, primer-like palindromic fragment, and polymerization-nicking template. The cosensitized structures consisted of CdS quantum dot functionalized hairpin DNA2 (QD-HP2) and region-selectively deposited gold nanoparticles onto {001} facets of bismuth oxychloride (BiOCl-Au). Compared with BiOCl-Au alone, the attachment of CdS QDs onto BiOCl-Au (i.e., BiOCl-Au-CdS QDs) exhibited evidently enhanced photocurrent intensity thanks to the synergistic effect of Z-scheme BiOCl-Au-CdS QDs. After incubation with target Kana, Kana-aptamer binding could induce the exposure of PMB region for hairpin DNA1 (HP1). The exposed palindromic tails hybridized with each other (like a molecular machine) to consume the substrates (dNTPs) and fuels (enzyme) for the releasing of numerous nick fragments (Nick). The as-generated nick fragments could specifically hybridize with the complementary region of QD-HP2, thus resulting in decreasing photocurrent because of the increasing spatial distance for electron transfer between two-type photosensitizers. Under optimum conditions, the PMB-based sensing system exhibited satisfying photocurrent responses toward target Kana within the working range from 50 to 5000 fM at a low detection limit of 29 fM. Impressively, the concept of a palindromic fragment-mediated primer-free biosensing strategy offers a new avenue for advanced development of efficient and convenient biodetection systems.

Raman microspectroscopic identification of microplastic particles in freshwater bivalves (Unio pictorum) exposed to sewage treatment plant effluents under different exposure scenarios

We investigated the uptake of microplastic (MP, <5 mm) particles by using freshwater bivalves (Unio pictorum) as biological samplers in the environment. They were exposed either directly to the biologically purified sewage of a North Bavarian sewage treatment plant (STP) or placed in a small river up- and downstream of the wastewater discharge for 28 days and 6 months, respectively. A control group was maintained in a pond. After acid digestion, the soft tissue was analyzed for MP particles by means of Raman microspectroscopy (RM, over 3000 particles individually measured), which allows for identification and quantification of particles down to 1 μm. Only in the bivalve collective exposed to STP effluents MP was found, however a very small amount (maximum of nine MP particles in the bivalve sample exposed for 6 months). In the bivalves up- and downstream of the wastewater discharge and in control organisms from a pond, no microplastic was identified. The amount of microplastic particles was small in absolute terms and small in relative terms (ca. 1:100 (6 months) and below 1:1000 (28 days)) as hundreds of particles per sample were analyzed which turned out to be non-plastic. Including the results for the river, this indicates a rather low MP contamination level for organisms in close vicinity to a sewage treatment plant.

Correction: Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood

Correction for ‘Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood’ by Kaisong Yuan et al., Chem. Sci., 2018, DOI: 10.1039/c8sc04637a.

Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood

A SERS based biosensor has been developed for isolation, detection and killing of multiple bacterial pathogens.

In this study, a new biosensor based on a sandwich structure has been developed for the isolation and detection of multiple bacterial pathogens via magnetic separation and SERS tags. This novel assay relies on antimicrobial peptide (AMP) functionalized magnetic nanoparticles as “capturing” probes for bacteria isolation and gold coated silver decorated graphene oxide (Au@Ag-GO) nanocomposites modified with 4-mercaptophenylboronic acid (4-MPBA) as SERS tags. When different kinds of bacterial pathogens are combined with the SERS tags, the “fingerprints” of 4-MPBA show corresponding changes due to the recognition interaction between 4-MPBA and different kinds of bacterial cell wall. Compared with the label-free SERS detection of bacteria, 4-MPBA here can be used as an internal standard (IS) to correct the SERS intensities with high reproducibility, as well as a Raman signal reporter to enhance the sensitivity and amplify the differences among the bacterial “fingerprints”. Thus, three bacterial pathogens (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) were successfully isolated and detected, with the lowest concentration for each of the strains detected at just 10¹ colony forming units per mL (CFU mL^–1). According to the changes in the “fingerprints” of 4-MPBA, three bacterial strains were successfully discriminated using discriminant analysis (DA). In addition, the AMP modified Fe₃O₄NPs feature high antibacterial activities, and can act as antibacterial agents with low cellular toxicology in the long-term storage of blood for future safe blood transfusion applications. More importantly, this novel method can be applied in the detection of bacteria from clinical patients who are infected with bacteria. In the validation analysis, 97.3% of the real blood samples (39 patients) could be classified effectively (only one patient infected with E. coli was misclassified). The multifunctional biosensor presented here allows for the simultaneous isolation, discrimination and killing of bacteria, suggesting its high potential for clinical diagnosis and safe blood transfusions.

Detecting Nonvolatile Life- and Nonlife-Derived Organics in a Carbonaceous Chondrite Analogue with a New Multiplex Immunoassay and Its Relevance for Planetary Exploration

Potential martian molecular targets include those supplied by meteoritic carbonaceous chondrites such as amino acids and polycyclic aromatic hydrocarbons and true biomarkers stemming from any hypothetical martian biota (organic architectures that can be directly related to once living organisms). Heat extraction and pyrolysis-based methods currently used in planetary exploration are highly aggressive and very often modify the target molecules making their identification a cumbersome task. We have developed and validated a mild, nondestructive, multiplex inhibitory microarray immunoassay and demonstrated its implementation in the SOLID (Signs of Life Detector) instrument for simultaneous detection of several nonvolatile life- and nonlife-derived organic molecules relevant in planetary exploration and environmental monitoring. By utilizing a set of highly specific antibodies that recognize D- or L- aromatic amino acids (Phe, Tyr, Trp), benzo[a]pyrene (B[a]P), pentachlorophenol, and sulfone-containing aromatic compounds, respectively, the assay was validated in the SOLID instrument for the analysis of carbon-rich samples used as analogues of the organic material in carbonaceous chondrites or even Mars samples. Most of the antibodies enabled sensitivities at the 1-10 ppb level and some even at the ppt level. The multiplex immunoassay allowed the detection of B[a]P as well as aromatic sulfones in a water/methanol extract of an Early Cretaceous lignite sample (c.a., 140 Ma) representing type IV kerogen. No L- or D-aromatic amino acids were detected, reflecting the advanced diagenetic stage and the fossil nature of the sample. The results demonstrate the ability of the liquid extraction by ultrasonication and the versatility of the multiplex inhibitory immunoassays in the SOLID instrument to discriminate between organic matter derived from life and nonlife processes, an essential step toward life detection outside Earth.

Variation in plastic abundance at different lake beach zones - A case study

Plastic particles in marine and freshwater environments span from macroscopic to microscopic size classes. Each may have a different impact on individuals, populations and ecosystems, but still the wide variety of methods used in beach sediment sampling inhibit comparisons among studies and therefore hampers a risk assessment. A large portion of the uncertainties is due to differing sampling strategies. By quantifying the alongshore distribution of macro- and microplastic particles within five beaches of Lake Garda, we aim to shed light on the accumulation behavior of microplastic particles at an exemplary lake which might give indications for potential sampling zones. The identification of plastic at the single particle level with a spatial resolution down to 1μm was performed by Raman microspectroscopy. Given the time consuming approach we reduced the number of samples in the field but increased the spatial area where a single sample was taken, by utilizing a transect approach in combination with sediment cores (5cm depth). The study revealed that, in comparison to the water line and the high-water line, the drift line of all five beaches always contained plastic particles. Since the drift line accumulate particulate matter on a relatively distinct zone, it will enable a comparable sampling of microplastic particles. The applied sampling approach provided a representative method for quantifying microplastic down to 1μm on a shore consisting of pebbles and sand. Hence, as first step towards a harmonization of beach sediment sampling we suggest to perform sampling at the drift line, although further methodological improvements are still necessary.

Cloning and plant-based production of antibody MC10E7 for a lateral flow immunoassay to detect [4-arginine]microcystin in freshwater

Antibody MC10E7 is one of a small number of monoclonal antibodies that bind specifically to [Arg4]-microcystins, and it can be used to survey natural water sources and food samples for algal toxin contamination. However, the development of sensitive immunoassays in different test formats, particularly user-friendly tests for on-site analysis, requires a sensitive but also cost-effective antibody. The original version of MC10E7 was derived from a murine hybridoma, but we determined the sequence of the variable regions using the peptide mass-assisted cloning strategy and expressed a scFv (single-chain variable fragment) format of this antibody in yeast and a chimeric full-size version in leaves of Nicotiana tabacum and Nicotiana benthamiana to facilitate inexpensive and scalable production. The specific antigen-binding activity of the purified antibody was verified by surface plasmon resonance spectroscopy and ELISA, confirming the same binding specificity as its hybridoma-derived counterpart. The plant-derived antibody was used to design a lateral flow immunoassay (dipstick) for the sensitive detection of [Arg4]-microcystins at concentrations of 100-300 ng/L in freshwater samples collected at different sites. Plant-based production will likely reduce the cost of the antibody, currently the most expensive component of the dipstick immunoassay, and will allow the development of further antibody-based analytical devices and water purification adsorbents for the efficient removal of toxic contaminants.

Metabolomic Fingerprinting in Various Body Fluids of a Diet-Controlled Clinical Smoking Cessation Study Using a Validated GC-TOF-MS Metabolomics Platform

Untargeted GC-TOF-MS analysis proved to be a suitable analytical platform to determine alterations in the metabolic profile. Several metabolic pathways were found to be altered in a first clinical study comparing smokers against nonsmokers. Subsequently, we conducted a clinical diet-controlled study to investigate alterations in the metabolic profile during the course of 3 months of smoking cessation. Sixty male subjects were included in the study, and plasma, saliva, and urine samples were collected during four 24 h stationary visits: at baseline, while still smoking, after 1 week, after 1 month, and after 3 months of cessation. Additionally, subjects were monitored for their compliance by measurements of CO in exhaled breath and salivary cotinine throughout the study. GC-TOF-MS fingerprinting was applied to plasma, saliva, and urine samples derived from 39 compliant subjects. In total, 52 metabolites were found to be significantly altered including 26 in plasma, 20 in saliva, and 12 in urine, respectively. In agreement with a previous study comparing smokers and nonsmokers, the fatty acid and amino acid metabolism showed significant alterations upon 3 months of smoking cessation. Thus these results may indicate a partial recovery of metabolic pathway perturbations, even after a relatively short period of smoking cessation.

Quantification of viable and non-viable Legionella spp. by heterogeneous asymmetric recombinase polymerase amplification (haRPA) on a flow-based chemiluminescence microarray

Increasing numbers of legionellosis outbreaks within the last years have shown that Legionella are a growing challenge for public health. Molecular biological detection methods capable of rapidly identifying viable Legionella are important for the control of engineered water systems. The current gold standard based on culture methods takes up to 10 days to show positive results. For this reason, a flow-based chemiluminescence (CL) DNA microarray was developed that is able to quantify viable and non-viable Legionella spp. as well as Legionella pneumophila in one hour. An isothermal heterogeneous asymmetric recombinase polymerase amplification (haRPA) was carried out on flow-based CL DNA microarrays. Detection limits of 87 genomic units (GU) µL^-1 and 26GUµL^-1 for Legionella spp. and Legionella pneumophila, respectively, were achieved. In this work, it was shown for the first time that the combination of a propidium monoazide (PMA) treatment with haRPA, the so-called viability haRPA, is able to identify viable Legionella on DNA microarrays. Different proportions of viable and non-viable Legionella, shown with the example of L. pneumophila, ranging in a total concentration between 10¹ to 10⁵GUµL^-1 were analyzed on the microarray analysis platform MCR 3. Recovery values for viable Legionella spp. were found between 81% and 133%. With the combination of these two methods, there is a chance to replace culture-based methods in the future for the monitoring of engineered water systems like condensation recooling plants.

Stable-isotope Raman microspectroscopy for the analysis of soil organic matter

We examined the potential of stable-isotope Raman microspectroscopy (SIRM) for the evaluation of differently enriched ¹³C-labeled humic acids as model substances for soil organic matter (SOM). The SOM itself can be linked to the soil water holding capacity. Therefore, artificial humic acids (HA) with known isotopic compositions were synthesized and analyzed by means of SIRM. By performing a pregraphitization, a suitable analysis method was developed to cope with the high fluorescence background. Results were verified against isotope ratio mass spectrometry (IRMS). The limit of quantification was 2.1 × 10^{-1 13}C/C _tot for the total region and 3.2 × 10^{-2 13}C/C _tot for a linear correlation up to 0.25 ¹³C/C _tot. Complementary nanoscale secondary ion mass spectrometry (NanoSIMS) analysis indicated small-scale heterogeneity within the dry sample material, even though-owing to sample topography and occurring matrix effects-obtained values deviated in magnitude from those of IRMS and SIRM. Our study shows that SIRM is well-suited for the analysis of stable isotope-labeled HA. This method requires no specific sample preparation and can provide information with a spatial resolution in the micrometer range. Graphical abstract Analysis of the isotopic composition of humic acids by Raman microspectroscopy in combination with isotope ratio mass spectrometry and nanoscale secondary ion mass spectrometry.

Tight Molecular Recognition of Benzo[a]pyrene by a High-Affinity Antibody

Benzo[a]pyrene, which is produced during the incomplete combustion of organic material, is an abundant noxious pollutant because of its carcinogenic metabolic degradation products. The high-affinity (K_D ≈3 nm) monoclonal antibody 22F12 allows facile bioanalytical quantification of benzo[a]pyrene even in complex matrices. We report the functional and X-ray crystallographic analysis of 22F12 in complex with 3-hydroxybenzo[a]pyrene after cloning of the V-genes and production as a recombinant Fab fragment. The polycyclic aromatic hydrocarbon is bound in a deep pocket between the light and heavy chains, surrounded mainly by aromatic and aliphatic amino acid side chains. Interestingly, the hapten-antibody interface is less densely packed than expected and reveals polar, H-bond-like interactions with the polycyclic aromatic π-electron system, which may allow the antibody to maintain a large, predominantly hydrophobic binding site in an aqueous environment while providing sufficient complementarity to its ligand.

Photoacoustic Spectroscopy for the Quantification of N2O in the Off-Gas of Wastewater Treatment Plants

Different configurations of photoacoustic (PA) setups for the online-measurement of gaseous N₂O, employing semiconductor lasers at 2.9 and 4.5 μm, were developed and tested. Their performance was assessed with respect to the analysis of N₂O emissions from wastewater treatment plants. For this purpose, the local N₂O emissions of a wastewater treatment bioreactor was sampled by a dedicated mobile sampling device, and the total N₂O emissions were analyzed in the gastight headspace of the bioreactor. We found that the use of a quantum-cascade laser emitting at about 4.53 μm, operated in a wavelength modulation mode, in combination with a conventional longitudinal PA cell yielded the highest sensitivity (<100 ppbv). However, we also observed a strong cross-sensitivity to humidity, which can be explained by increased V-T relaxation. This observation in combination with the limited dynamic range (max conc. ∼ 3000 ppmv) led us to the use of the less-sensitive but spectroscopically more robust 2.9 μm laser. A detection limit below 1 ppmv, a dynamic range of more than 4 orders of magnitude, no influence of humidity or any other substance relevant to the off-gas analysis, as well as a comparable low price of the laser source made it the ideal tool for N₂O analyses of the off-gas of a wastewater treatment plant. Such a system was implemented successfully in a full-scale wastewater treatment plant. The results regarding the comparison of different PA setups can be transferred to other systems, and the optimum performance can be selected according to the specific demands.

Validation Procedure for Multiplex Antibiotic Immunoassays Using Flow-Based Chemiluminescence Microarrays

Small molecules like antibiotics or other pharmaceuticals can be detected and quantified, among others, with indirect competitive immunoassays. With regard to multiplex quantification, these tests can be performed as chemiluminescence microarray immunoassays, in which, in principle, the analyte in the sample and the same substance immobilized on the chip surface compete for a limited number of specific antibody binding sites. The amount of the specific primary antibody that has been bound to the surface is visualized by means of a chemiluminescence reaction.Validated quantitative confirmatory methods for the detection of contaminants, for example drug residues, in food samples usually comprise chromatographic analysis and spectrometric detection, e.g., HPLC-MS, GC-MS, or GC with electron capture detection. Here, we describe a validation procedure (according to the Commission Decision of the European Communities 2002/657/EC) for multiplex immunoassays performed as flow-through chemiluminescence microarrays, using the example of a small molecule microarray for the simultaneous detection of 13 antibiotics in milk. By this means, we suggest to accept multianalyte immunoassays as confirmatory methods as well, to benefit from the advantages of a fast automated method that does not need any pretreatment of the sample. The presented microarray chip is regenerable, so an internal calibration is implemented. Therefore, the analytical results are highly precise, combined with low costs (the aim for commercialization is less than 1 € per analyte per sample, this is significantly less than HPLC-MS).

Detection of Legionella-contaminated aerosols in the vicinity of a bio-trickling filter of a breeding sow facility - A pilot study

The urbanization of agricultural areas results in a reduction of distances between residential buildings and livestock farms. In the public debate, livestock farming is increasingly criticized due to environmental disturbance and odor nuisance originating from such facilities. One method to reduce odor and ammonia is by exhaust air treatment, for example, by biological exhaust air purification processes with bio-trickling filters filled with tap water. Higher temperatures in the summer time and the generation of biofilms are ideal growth conditions for Legionella. However, there are no studies on the presence of Legionella in the water of bio-trickling filters and the release of Legionella-containing aerosols. Therefore, the aim of this study was to investigate Legionella in wash water and emitted bioaerosols of a bio-trickling filter system of a breeding sow facility. For this purpose, measurements were carried out using a cyclone sampler. In addition, samples of wash water were taken. Legionella were not found by culture methods. However, using molecular biological methods, Legionella spp. could be detected in wash water as well as in bioaerosol samples. With antibody-based methods, Legionella pneumophila were identified. Further studies are needed to investigate the environmental health relevance of Legionella-containing aerosols emitted by such exhaust air purification systems.

A fully validated GC-TOF-MS method for the quantification of fatty acids revealed alterations in the metabolic profile of fatty acids after smoking cessation

We developed and validated an efficient and robust method for the simultaneous quantification of 44 fatty acid species in human plasma via GC-TOF-MS. The method is characterized by its robustness, accuracy and precision covering a wide range of fatty acid species with various saturation degrees including short chain fatty acids (beginning with FA 4:0) and long chain fatty acids (up to FA 32:0). The fatty acids were methylated prior to analyses and subsequently detected as fatty acid methyl esters by means of GC-TOF-MS. A highly substituted polar column allowed the separation of geometrical and positional isomers of fatty acid species. The method was applied to plasma samples of a strictly diet controlled clinical smoking cessation study including 39 smokers followed over the course of three months after having quit. Statistical significant alterations within the fatty acid profile were observed when comparing the baseline (subjects still smoking) with one week, one month and three months of smoking cessation. After 3 months of smoking cessation, a partial recovery of alterations in the fatty acid profile evoked by smoking was observed. In conclusion, the developed fatty acid profiling method using GC-TOF-MS has proven as a reliable tool for the quantitative determination of 44 individual fatty acid species within clinical studies.

Long amplicon (LA)-qPCR for the discrimination of infectious and noninfectious phix174 bacteriophages after UV inactivation

Waterborne viruses are increasingly being considered in risk assessment schemes. In general, virus detection by culture methods is time consuming. In contrast, detection by quantitative polymerase chain reaction (qPCR) is more rapid and therefore, more suitable for monitoring. At present, qPCR lacks the essential ability for discriminating between infectious and non-infectious viruses, thus limiting its applicability for monitoring disinfection processes. In this study, a method was developed to quantify UV inactivation by long amplicon (LA)-qPCR. Bacteriophage phiX174 was used as a surrogate for human pathogenic viruses. A qPCR protocol was developed with new sets of primers, resulting in amplicon lengths of 108, 250, 456, 568, 955, 1063, 1544, and 1764 nucleotides. The log reduction of gene copies increased with increasing amplicon length. Additional treatment with the intercalating dye, PMA, had no effect, indicating that the bacteriophage capsids were not damaged by low pressure UV irradiation. A qPCR of nearly the complete genome (approx. 5000 nucleotides) showed similar results to the plaque assay. The log reduction in qPCR correlates with [specific amplicon length x UV dose]. The normalized DNA effect constant can be applied to calculate phiX174 inactivation based on qPCR detection.

Pigments and plastic in limnetic ecosystems: A qualitative and quantitative study on microparticles of different size classes

Recently, macroplastic (>5 mm) and especially microplastic (<5 mm) particles have been reported as emerging contaminants in marine and limnetic ecosystems. Their coloration is gained by the addition of pigments to the polymer blend which is the major component of the respective product. However, color is also a feature of paint and coatings whereby the pigment is the major component. Once abraded from a surface, paint particles may enter the environment via similar pathways as microplastic particles. So far no detailed studies of microplastic particles (pigmented and non-pigmented) as well as paint particles have been performed focusing on very small microparticles (1-50 μm), in either marine or limnetic ecosystems. Using Raman microspectroscopy with a spatial resolution down to 1 μm, we report a remarkable increase in the occurrence of (pigmented) microplastic particles below 500 μm. Among those, most particles were found at a size of ∼130 μm in a freshwater ecosystem (subalpine Lake Garda, Italy). Moreover, our qualitative and quantitative analyses revealed that the number of paint microparticles significantly increased below the size range of 50 μm due to their brittleness (the smallest detected paint particle had a size of 4 μm). Inductively coupled plasma mass spectrometry measurements showed that both colored particles found in nature as well as virgin particles contain a high variety of metals such as cadmium, lead and copper. These additives may elicit adverse effects in biota ingesting these microparticles, thus paints and associated compounds may act as formerly overlooked contaminants in freshwater ecosystems.

Competitive Upconversion-Linked Immunosorbent Assay for the Sensitive Detection of Diclofenac

Photon-upconverting nanoparticles (UCNPs) emit light of shorter wavelength under near-infrared excitation and thus avoid optical background interference. We have exploited this unique photophysical feature to establish a sensitive competitive immunoassay for the detection of the pharmaceutical micropollutant diclofenac (DCF) in water. The so-called upconversion-linked immunosorbent assay (ULISA) was critically dependent on the design of the upconversion luminescent detection label. Silica-coated UCNPs (50 nm in diameter) exposing carboxyl groups on the surface were conjugated to a secondary anti-IgG antibody. We investigated the structure and monodispersity of the nanoconjugates in detail. Using a highly affine anti-DCF primary antibody, the optimized ULISA reached a detection limit of 0.05 ng DCF per mL. This performance came close to a conventional enzyme-linked immunosorbent assay (ELISA) without the need for an enzyme-mediated signal amplification step. The ULISA was further employed for analyzing drinking and surface water samples. The results were consistent with a conventional ELISA as well as liquid chromatography-mass spectrometry (LC-MS).

Gold nanoparticle-catalyzed uranine reduction for signal amplification in fluorescent assays for melamine and aflatoxin B1

A multifunctional fluorescence platform has been constructed based on gold nanoparticle (AuNP)-catalyzed uranine reduction. The catalytic reduction of uranine was conducted in aqueous solution using AuNPs as nanocatalyst and sodium borohydride as reducing reagent, which was monitored by fluorescence and UV-vis spectroscopy. The reaction rate was highly dependent on the concentration, size and dispersion state of AuNPs. When AuNPs aggregated, their catalytic ability decreased, and thereby a label-free fluorescent assay was developed for the detection of melamine, which can be used for melamine determination in milk. In addition, a fluorescent immunoassay for aflatoxin B1 (AFB1) was established using the catalytic reaction for signal amplification based on target-induced concentration change of AuNPs, where AFB1-BSA-coated magnetic beads and anti-AFB1 antibody-conjugated AuNPs were employed as capture and signal probe, respectively. The detection can be accomplished in 1 h and acceptable recoveries in spiked maize samples were achieved. The developed fluorescence system is simple, sensitive and specific, which could be used for the detection of a wide range of analytes.

The origin of the band at around 730 cm−1 in the SERS spectra of bacteria: a stable isotope approach

A stable isotope approach combined with SERS analysis of bacteria allows clarification of the origin of a pronounced band at 730 cm⁻¹.

On-Chip Isothermal Nucleic Acid Amplification on Flow-Based Chemiluminescence Microarray Analysis Platform for the Detection of Viruses and Bacteria

This work presents an on-chip isothermal nucleic acid amplification test (iNAAT) for the multiplex amplification and detection of viral and bacterial DNA by a flow-based chemiluminescence microarray. In a principle study, on-chip recombinase polymerase amplification (RPA) on defined spots of a DNA microarray was used to spatially separate the amplification reaction of DNA from two viruses (Human adenovirus 41, Phi X 174) and the bacterium Enterococcus faecalis, which are relevant for water hygiene. By establishing the developed assay on the microarray analysis platform MCR 3, the automation of isothermal multiplex-amplification (39 °C, 40 min) and subsequent detection by chemiluminescence imaging was realized. Within 48 min, the microbes could be identified by the spot position on the microarray while the generated chemiluminescence signal correlated with the amount of applied microbe DNA. The limit of detection (LOD) determined for HAdV 41, Phi X 174, and E. faecalis was 35 GU/μL, 1 GU/μL, and 5 × 10(3) GU/μL (genomic units), which is comparable to the sensitivity reported for qPCR analysis, respectively. Moreover the simultaneous amplification and detection of DNA from all three microbes was possible. The presented assay shows that complex enzymatic reactions like an isothermal amplification can be performed in an easy-to-use experimental setup. Furthermore, iNAATs can be potent candidates for multipathogen detection in clinical, food, or environmental samples in routine or field monitoring approaches.

Investigation of coatings of natural organic matter on silver nanoparticles under environmentally relevant conditions by surface-enhanced Raman scattering

The widespread use of engineered inorganic nanoparticles (EINP) leads to a growing risk for an unintended release into the environment. Despite the good characterization of EINP in regard to their function scale and the application areas, there is still a gap of knowledge concerning their behaviour in the different environmental compartments. Due to their high surface to volume ratio, surface properties and existence or development of a coating are of high importance for their stability and transport behaviour. However, analytical methods to investigate organic coatings on nanoparticles in aqueous media are scarce. We used Raman microspectroscopy in combination with surface-enhanced Raman scattering (SERS) to investigate humic acid coatings on silver nanoparticles under environmentally relevant conditions and in real world samples. This setup is more challenging than previous mechanistic studies using SERS to characterize the humic acids in tailored settings where only one type of organic matter is present and the concentrations of the nanoparticles can be easily adjusted to the experimental needs. SERS offers the unique opportunity to work with little sample preparation directly with liquid samples, thus significantly reducing artefacts. SERS spectra of different natural organic matter brought into contact with silver nanoparticles indicate humic acid in close proximity to the nanoparticles. This coating was also present after several washing steps by centrifugation and resuspension in deionized water and after an increase in ionic strength.