The authors thank Dr. Yoav Barak from the Chemistry Faculty, Weizmann Institute, for support and advice. This study was supported by the Israel Science Foundation (grant # 913/12), and by the Minerva Foundation with funding from the Federal German Ministry for Education and Research.

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The authors have nothing to disclose.

This work describes extraction and detection methods for quantifying both endotoxins and DNA present in aerosol samples collected on filters. The methods require accurate routines and can be performed easily as long as the experimentalist adheres to a few essential and important points discussed here.
For the endotoxin detection step, note that the lysate solution is quite viscous and tends to produce bubbles upon pipetting. It is difficult to remove thee bubbles, and they lead to changes in t...

Air sampling on filters is a basic tool in atmospheric aerosols research.1 The sampled filters are the starting point for various chemical, physical, and biological characterizations of the collected ambient particles.2-11 The advantage of this approach is that various analyses can be performed off-line on the same sample. Compiling the data from all the different analyses enables the researcher to obtain a good understanding of the characteristics of the collected particles and aids in solving complex questions in the atmospheric sciences.12,13 For example, marine and inland air-samples taken during the same period can be compared with respect to the sampled particle toxicity and biological composition.14 For this study, lipopolysaccharides (LPS), components on gram-negative bacterial cell-walls, also known as endotoxins, were extracted from filters sampled on-shore and at an inland site, and were evaluated using the limulus amebocyte lysate (LAL) test. In parallel, a genomic evaluation of the bacterial content (total bacteria, gram negative, and cyanobacteria) was performed on the same sample using the quantitative polymerase chain reaction (q-PCR). The LAL test is based on measurements of turbidity formed following the addition of an aqueous extract of amebocytes from the horseshoe crab, Limulus polyphemus, to an aqueous solution containing the endotoxins. The higher the endotoxin concentration in the sample, the faster turbidity develops.15 The q-PCR analysis is based on a fluorescence signal emitted as a specific DNA fragment is amplified.16 By real time monitoring of the signal during the exponential phase of the PCR reaction and calibrating with a standard curve, the initial DNA amount can be quantified. The combination of these two analyses together with others, as detailed elsewhere,14 can provide a good estimation of the levels of endotoxin and the amount of the source bacteria in the samples.
The purpose of the method presented here is to obtain a highly accurate and reliable analysis of the endotoxin and DNA content of bio-aerosols extracted from filters. While methods for sampling the physical and inorganic chemical characteristics of aerosols are well known and, more recently, methods have been developed to investigate its organic matter component,17 there has been scant research on the biological component of aerosols.18 The rationale for the current method is to address this gap by presenting in detail a robust method for extracting, analyzing, and identifying the biological fraction of airborne aerosols.14
The method detailed here is expected to find wide-spread use in biological indoor and outdoor aerosol research projects involving filter analysis.20-24

<table><tbody><tr><td>&lt;strong&gt;Filter sampling&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>HiVol 3000 - High Volume Air Sampler</td><td>Ecotech</td><td></td><td></td></tr><tr><td>Quartz Microfiber Filters</td><td>Whatman</td><td>1851-865</td><td>203 mm x 254 mm</td></tr><tr><td>ELF - Laboratory Chamber Furnaces</td><td>Carbolite</td><td>ELF 11series</td><td></td></tr><tr><td>Aluminum foil</td><td>Opal</td><td></td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Endotoxin&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Ethanol</td><td>Sigma Aldrich</td><td>16368&amp;nbsp;</td><td>Laboratory Reagent, 96%</td></tr><tr><td>Airstream Class II Biological Safety Cabinet AC-4E1</td><td>ESCO</td><td>10011712</td><td></td></tr><tr><td>Pyrotell -T</td><td>Associates of Cape Cod, Inc.</td><td>T0051</td><td></td></tr><tr><td>Control Standard Endotoxin</td><td>Associates of Cape Cod, Inc.</td><td>E0005-1</td><td>&lt;em&gt;Escherichia coli&lt;/em&gt;&amp;nbsp;O113:H10, 0.5 &amp;micro;g/vial 1 Pack</td></tr><tr><td>LAL Reagent Water</td><td>Associates of Cape Cod, Inc.</td><td>W0051</td><td></td></tr><tr><td>10 ml sterile syringe with Luer-Lok Tip</td><td>Becton-Dickinson &amp;amp; Co.</td><td>309605</td><td></td></tr><tr><td>BD Precisionglide syringe needle</td><td>Becton-Dickinson &amp;amp; Co.</td><td>305129</td><td>Sterile&amp;nbsp;</td></tr><tr><td>Parafilm-M sealing tape</td><td>Parafilm</td><td>P7543</td><td>Sigma catalog number</td></tr><tr><td>Microtubes</td><td>Axigen</td><td>MCT-200-C</td><td>2 ml, pyrogen free</td></tr><tr><td>1.12 cm diameter Cork Borer</td><td>Boekel Scientific</td><td>1601 BD Series - Steel</td><td>Part of a cork borer set containing borers with various diameters.&amp;nbsp;</td></tr><tr><td>50 mm Petri Dish</td><td>Miniplast Ein-Shemer</td><td>72050-01</td><td>Aseptic</td></tr><tr><td>Vortex Genie 2&amp;nbsp;</td><td>Scientific Industries, inc.</td><td>SI-0297</td><td></td></tr><tr><td>Microcentrifuge 5415 D</td><td>Eppendorf</td><td>22621408</td><td></td></tr><tr><td>TC MicroWell 96 F SI w/lid</td><td>Nunc</td><td>167008</td><td>Flat bottom wells (with lid (individually wrapped)), sterile, pyrogen free</td></tr><tr><td>Synergy HT Multi-Detection Microplate Reader</td><td>Biotek</td><td>7091000</td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;DNA&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>DNA away</td><td>Sigma Aldrich</td><td>7010</td><td></td></tr><tr><td>Standard DNA of the microbial species of interest</td><td>ATCC or other culture collection</td><td></td><td>Either the appropriate microbial strain for DNA extraction or the extracted DNA</td></tr><tr><td>Neubauer-improved</td><td>Marienfeld</td><td>640030</td><td>hemocytometer</td></tr><tr><td>TE buffer, Low EDTA</td><td>Life Technologies</td><td>12090-015</td><td>10 mM Tris-HCl (pH 8.0)&amp;nbsp;0.1 mM EDTA&amp;nbsp;</td></tr><tr><td>Nuclease-free PCR-grade water&amp;nbsp;</td><td>Sigma Aldrich</td><td>3315959001</td><td></td></tr><tr><td>PCR primers</td><td>Sigma Aldrich</td><td></td><td>Targets the microbial species of interest</td></tr><tr><td>Dual-Labeled Probes</td><td>Sigma Aldrich</td><td></td><td>Targets the microbial species of interest</td></tr><tr><td>Screw cap tubes</td><td>Axigen</td><td>ST-200-SS</td><td>2 ml&amp;nbsp;</td></tr><tr><td>PowerSoil DNA extraction kit&amp;nbsp;</td><td>Mo Bio Laboratories</td><td>12888-100</td><td></td></tr><tr><td>Glass beads, acid-washed 425-600 &amp;micro;m</td><td>Sigma Aldrich</td><td>G8772-100G</td><td></td></tr><tr><td>Glass beads, acid-washed &amp;lt;106 &amp;micro;m</td><td>Sigma Aldrich</td><td>G4649-100G</td><td></td></tr><tr><td>PowerSoil Solution C1</td><td>Mo Bio Laboratories</td><td>12888-100-1</td><td>Cell lysis buffer , Power soil Kit</td></tr><tr><td>Magic Touch ice bucket</td><td>Bel-Art</td><td>18848-4001</td><td></td></tr><tr><td>Mini-Beadbeater-16</td><td>BioSpec</td><td>607EUR</td><td></td></tr><tr><td>StepOnePlus Real-Time PCR System</td><td>Applied Biosystems</td><td>4376600</td><td></td></tr><tr><td>Fast SYBR Green Master Mix</td><td>Applied Biosystems</td><td>4385612</td><td></td></tr><tr><td>TaqMan Gene Expression Master Mix</td><td>Applied Biosystems</td><td>4370048</td><td></td></tr><tr><td>MicroAmp Fast Optical 96-Well Reaction Plate with Barcode, 0.1 ml</td><td>Applied Biosystems</td><td>4346906</td><td></td></tr><tr><td>MicroAmp Splash-Free 96-Well Base</td><td>Applied Biosystems</td><td>4312063</td><td></td></tr><tr><td>MicroAmp Optical Adhesive Film</td><td>Applied Biosystems</td><td>4311971</td><td></td></tr><tr><td>Centrifuge 5810 R</td><td>Eppendorf</td><td>5811 000.010</td><td>Rotor A-4-62 with MTP buckets&amp;nbsp;</td></tr></tbody></table>

air-sampled filter analysis for endotoxins and dna content

Outdoor aerosol research commonly uses particulate matter sampled on filters. This procedure enables various characterizations of the collected particles to be performed in parallel. The purpose of the method presented here is to obtain a highly accurate and reliable analysis of the endotoxin and DNA content of bio-aerosols extracted from filters. The extraction of high molecular weight organic molecules, such as lipopolysaccharides, from sampled filters involves shaking the sample in a pyrogen-free water-based medium. The subsequent analysis is based on an enzymatic reaction that can be detected using a turbidimetric measurement. As a result of the high organic content on the sampled filters, the extraction of DNA from the samples is performed using a commercial DNA extraction kit that was originally designed for soils and modified to improve the DNA yield. The detection and quantification of specific microbial species using quantitative polymerase chain reaction (q-PCR) analysis are described and compared with other available methods.

It is common to study atmospheric aerosols using &#34;off-line&#34; analyses of sampled filters (see Figure 2).32 Chemical analyses of the sampled matter include organic (e.g. protein, hydrocarbon molecules, saccharides) and inorganic (e.g. metals, salts) content. Biological analyses include viable and non-viable microorganism content, species identification using a DNA approach or microscopy, as well as DNA-based quantification.
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Watch this Scientific Journal Video about Air-sampled Filter Analysis for Endotoxins and DNA Content at JoVE.com

Air-sampled Filter Analysis for Endotoxins and DNA Content

Two complementary analyses of atmospheric biological particles from air sampled filters are described herein: the extraction and detection of endotoxin, and of DNA.

Outdoor aerosol research commonly uses particulate matter sampled on filters. This procedure enables various characterizations of the collected particles ...

air-sampled-filter-analysis-for-endotoxins-and-dna-content

Research

JoVE Journal

Environment

9.6K Views.  Weizmann Institute of Science. Two complementary analyses of atmospheric biological particles from air sampled filters are described herein: the extraction and detection of endotoxin, and of DNA.

Video: Air-sampled Filter Analysis for Endotoxins and DNA Content

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS can be subdivided into three domains: the distal O-polysaccharide, a core oligosaccharide, and the lipid A domain consisting of a lipid A molecular species and 3-deoxy-D-manno-oct-2-ulosonic acid residues (Kdo). The lipid A domain is the only component essential for bacterial cell survival. Following its synthesis, lipid A is chemically modified in response to environmental stresses such as pH or temperature, to promote resistance to antibiotic compounds, and to evade recognition by mediators of the host innate immune response. The following protocol details the small- and large-scale isolation of lipid A from gram-negative bacteria. Isolated material is then chemically characterized by thin layer chromatography (TLC) or mass-spectrometry (MS). In addition to matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS, we also describe tandem MS protocols for analyzing lipid A molecular species using electrospray ionization (ESI) coupled to collision induced dissociation (CID) and newly employed ultraviolet photodissociation (UVPD) methods. Our MS protocols allow for unequivocal determination of chemical structure, paramount to characterization of lipid A molecules that contain unique or novel chemical modifications. We also describe the radioisotopic labeling, and subsequent isolation, of lipid A from bacterial cells for analysis by TLC. Relative to MS-based protocols, TLC provides a more economical and rapid characterization method, but cannot be used to unambiguously assign lipid A chemical structures without the use of standards of known chemical structure. Over the last two decades isolation and characterization of lipid A has led to numerous exciting discoveries that have improved our understanding of the physiology of gram-negative bacteria, mechanisms of antibiotic resistance, the human innate immune response, and have provided many new targets in the development of antibacterial compounds.

Isolation and characterization of the lipid A domain of lipopolysaccharide (LPS) from gram-negative bacteria provides insight into cell surface based mechanisms of antibiotic resistance, bacterial survival and fitness, and how chemically diverse lipid A molecular species differentially modulate host innate immune responses.

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS ...

Chemistry

Composition and Distribution Analysis of Bioaerosols Under Different Environmental Conditions

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, we described a protocol for multiple analyses of the biological compositions in environmental PM. Five experiments are presented: (1) PM number monitoring by using a laser particle counter; (2) PM collection by using a cyclonic aerosol sampler; (3) PM collection by using a high-volume air sampler with filters; (4) culturable microbes collection by the Andersen six-stage sampler; and (5) detection of biological composition of environmental PM by bacterial 16SrDNA and fungal ITS region sequencing. We selected hazy days and a livestock farm as two typical examples of the application in this protocol. In this study, these two sampling methods, cyclonic aerosol sampler and filter sampler, showed different sampling efficiency. The cyclonic aerosol sampler performed much better in terms of collecting bacteria, while these two methods showed the same efficiency in collecting fungi. Filter samplers can work under low temperature conditions while cyclonic aerosol samplers have a sampling limitation for temperature. A solid impacting sampler, such as an Andersen six-stage sampler, can be used to sample bioaerosols directly into the culture medium, which increases the survival rate of culturable microorganisms. However, this method mainly relies on culture while more than 99% of microbes cannot be cultured. DNA extracted from the culturable bacteria collected by the Andersen six-stage sampler and samples collected by cyclonic aerosol sampler and filter sampler were detected by bacterial 16S rDNA and fungal ITS region sequencing.All the methods above may have wide application in many fields of study, such as environmental monitoring and airborne pathogen detection. From these results, we can conclude that these methods can be used under different conditions and may help other researchers further explore the health impacts of environmental bioaerosols.

Understanding the biological composition of environmental particulate matter is important for the study of its significant impacts on human health and disease spread. Here, we used three types of bioaerosol sampling methods and a biological analysis of airborne microbes to better explore airborne microbial communities under different environmental conditions.

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, ...

Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate (LAL) Assays

When present in pharmaceutical products, a Gram-negative bacterial cell wall component endotoxin (often also called lipopolysaccharide) can cause inflammation, fever, hypo- or hypertension, and, in extreme cases, can lead to tissue and organ damage that may become fatal. The amounts of endotoxin in pharmaceutical products, therefore, are strictly regulated. Among the methods available for endotoxin detection and quantification, the Limulus Amoebocyte Lysate (LAL) assay is commonly used worldwide. While any pharmaceutical product can interfere with the LAL assay, nano-formulations represent a particular challenge due to their complexity. The purpose of this paper is to provide a practical guide to researchers inexperienced in estimating endotoxins in engineered nanomaterials and nanoparticle-formulated drugs. Herein, practical recommendations for performing three LAL formats including turbidity, chromogenic and gel-clot assays are discussed. These assays can be used to determine endotoxin contamination in nanotechnology-based drug products, vaccines, and adjuvants.

Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate LAL Assays

Detection of endotoxins in engineered nanomaterials represents one of the grand challenges in the field of nanomedicine. Here, we present a case study that describes the framework composed of three different LAL formats to estimate potential endotoxin contamination in nanoparticles.

When present in pharmaceutical products, a Gram-negative bacterial cell wall component endotoxin (often also called lipopolysaccharide) can cause ...

Bioengineering

Production of E. coli-expressed Self-Assembling Protein Nanoparticles for Vaccines Requiring Trimeric Epitope Presentation

Self-assembling protein nanoparticles (SAPNs) function as repetitive antigen displays and can be used to develop a wide range of vaccines for different infectious diseases. In this article we demonstrate a method to produce a SAPN core containing a six-helix bundle (SHB) assembly that is capable of presenting antigens in a trimeric conformation. We describe the expression of the SHB-SAPN in an E. coli system, as well as the necessary protein purification steps. We included an isopropanol wash step to reduce the residual bacterial lipopolysaccharide. As an indication of the protein identity and purity, the protein reacted with known monoclonal antibodies in Western blot analyses. After refolding, the size of the particles fell in the expected range (20 to 100 nm), which was confirmed by dynamic light scattering, nanoparticle tracking analysis, and transmission electron microscopy. The methodology described here is optimized for the SHB-SAPN, however, with only slight modifications it can be applied to other SAPN constructs. This method is also easily transferable to large scale production for GMP manufacturing for human vaccines.

Production of E. coli-expressed Self-Assembling Protein Nanoparticles for Vaccines Requiring Trimeric Epitope Presentation

A detailed method is provided here describing the purification, refolding, and characterization of self-assembling protein nanoparticles (SAPNs) for use in vaccine development.

Self-assembling protein nanoparticles (SAPNs) function as repetitive antigen displays and can be used to develop a wide range of vaccines for different ...

A Macrophage Reporter Cell Assay to Examine Toll-Like Receptor-Mediated NF-kB/AP-1 Signaling on Adsorbed Protein Layers on Polymeric Surfaces

The persistent inflammatory host response to an implanted biomaterial, known as the foreign body reaction, is a significant challenge in the development and implementation of biomedical devices and tissue engineering constructs. Macrophages, an innate immune cell, are key players in the foreign body reaction because they remain at the implant site for the lifetime of the device, and are commonly studied to gain an understanding of this detrimental host response. Many biomaterials researchers have shown that adsorbed protein layers on implanted materials influence macrophage behavior, and subsequently impact the host response. The methods in this paper describe an in vitro model using adsorbed protein layers containing cellular damage molecules on polymer biomaterial surfaces to assess macrophage responses. An NF-&#1082;B/AP-1 reporter macrophage cell line and the associated colorimetric alkaline phosphatase assay were used as a rapid method to indirectly examine NF-&#1082;B/AP-1 transcription factor activity in response to complex adsorbed protein layers containing blood proteins and damage-associated molecular patterns, as a model of the complex adsorbed protein layers formed on biomaterial surfaces in vivo.

This protocol provides researchers with a rapid, indirect method of measuring TLR-dependent NF-&#1082;B/AP-1 transcription factor activity in a murine macrophage cell line in response to a variety of polymeric surfaces and adsorbed protein layers that model the biomaterial implant microenvironment.

The persistent inflammatory host response to an implanted biomaterial, known as the foreign body reaction, is a significant challenge in the development ...

Endotoxin Activity Assay for the Detection of Whole Blood Endotoxemia in Critically Ill Patients

Lipopolysaccharide, also known as endotoxin, is a fundamental component of gram-negative bacteria and plays a crucial role in the development of sepsis and septic shock. The early identification of an infectious process that is rapidly evolving to a critical illness might prompt a quicker and more intensive treatment, thereby potentially leading to better patient outcomes. The Endotoxin Activity (EA) assay can be used at the bedside as a reliable biomarker of systemic endotoxemia. The detection of elevated endotoxin activity levels has been repeatedly shown to be associated with an increased disease severity in patients with sepsis and septic shock. The assay is quick and easy to perform. Briefly, after sampling, an aliquot of whole blood is mixed with an anti-endotoxin antibody and with added LPS. Endotoxin activity is measured as the relative oxidative burst of primed neutrophils as detected by chemioluminescence. The assay&#39;s output is expressed on a scale from 0 (absent) to 1 (maximal) and categorized as &#8220;low&#8221; (&#60;0.4 units), &#8220;intermediate&#8221; (0.4&#8211;0.59 units), or &#8220;high&#8221; (&#8805;0.6 units). The detailed methodology and rationale for the implementation of the EA assay are reported in this manuscript.

We hereby present a protocol to measure at the bedside the endotoxin activity of human whole blood samples. The Endotoxin Activity assay is a simple test to perform and may be a useful biomarker in critically ill patients with sepsis.

Lipopolysaccharide, also known as endotoxin, is a fundamental component of gram-negative bacteria and plays a crucial role in the development of sepsis ...

Medicine

Efficient Technique for Assessing Environmental AMR by Enriching Low-MW DNA

Enhanced Extraction of Low-Molecular Weight DNA from Wastewater for Comprehensive Assessment of Antimicrobial Resistance

Environmental surveillance is recognized as an important tool for assessing public health in the post-pandemic era. Water, in particular wastewater, has emerged as the source of choice to sample pathogen burdens in the environment. Wastewater from open drains and community water treatment plants is a reservoir of both pathogens and antimicrobial resistance (AMR) genes, and frequently comes in contact with humans. While there are many methods of tracking AMR from water,&#160;isolating good-quality DNA at high yields from heterogeneous samples remains a challenge. To compensate, sample volumes often need to be high, creating practical constraints. Additionally, environmental DNA is frequently fragmented, and the sources of AMR (plasmids, phages, linear DNA) consist of low-molecular-weight DNA. Yet, few extraction processes have focused on methods for high-yield extraction of linear and low-molecular-weight DNA. Here, a simple method for high-yield linear DNA extraction from small volumes of wastewater using the precipitation properties of polyethylene glycol (PEG) is reported. This study makes a case for increasing overall DNA yields from water samples collected for metagenomic analyses by enriching the proportion of linear DNA. In addition, enhancing low-molecular-weight DNA overcomes the current problem of under-sampling environmental AMR due to a focus on high-molecular-weight and intracellular DNA. This method is expected to be particularly useful when extracellular DNA exists but at low concentrations, such as with effluents from treatment plants. It should also enhance the environmental sampling of AMR gene fragments that spread through horizontal gene transfer.

Author Spotlight: Understanding and Detecting Environmental Antimicrobial Resistance by Combining Culture-Based Techniques and Genomics

Here, we present a simple technique to assess environmental antimicrobial resistance (AMR) by enhancing the proportion of low-molecular-weight extracellular DNA. Prior treatment with 20%-30% PEG and 1.2 M NaCl allows detection of both genomic and horizontally transferred AMR genes. The protocol lends itself to a kit-free process with additional optimization.

Environmental surveillance is recognized as an important tool for assessing public health in the post-pandemic era. Water, in particular wastewater, has ...

Biology

Gel-Clot Limulus Amoebocyte Lysate Assay: A Method for Bacterial Endotoxin Detection in Nanoparticle Formulations

Source: Neun, B. W. et al., <a href="https://www.jove.com/v/58830">Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate (LAL) Assays.</a> J. Vis. Exp. (2019).
This video describes a gel-clot assay to determine the presence of bacterial endotoxins in nano-formulations using Limulus Amoebocyte Lysate derived from the blood cells of horseshoe crabs. The assay helps test for endotoxin contamination of pharmaceutical products, including nano-based formulations.

Source: Neun, B. W. et al., Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate (LAL) Assays. J. Vis. Exp. (2019).
This video ...

JoVE Encyclopedia of Experiments

Biological Techniques

Assay Techniques

Biochemical assays

An Assay for TLR-Dependent NF-&kcy;B/AP-1 Transcription Factor Signaling in Macrophages

Source: McKiel, L. A., et al. <a href="https://app.jove.com/v/60317">A Macrophage Reporter Cell Assay to Examine Toll-Like Receptor-Mediated NF-kB/AP-1 Signaling on Adsorbed Protein Layers on Polymeric Surfaces.</a> J. Vis. Exp. (2020).
This video demonstrates an assay to examine the toll-like receptor(TLR)-dependent activity of the transcription factors nuclear factor-kappa-B (NF-&#954;B) and activator protein-1 (AP-1) in macrophages. The TLRs trigger a pro-inflammatory signaling cascade upon recognizing damage-associated molecular patterns (DAMPs), activating NF-&#954;B and AP-1. The engineered reporter macrophages produce secreted embryonic alkaline phosphatase (SEAP) enzyme upon NF-&#954;B and AP-1 activation, which is detected via a chromogenic reaction.

1. Media and Reagent Preparation

	Prepare fibroblast media. Combine 450 mL of Dulbecco&#39;s modified Eagle medium (DMEM), 50 mL of fetal bovine serum ...

Immunology

Immunodiagnostics

Specialized Assays

Endotoxin Activity Assay: A Chemiluminescence-Based Bioassay for Investigating Endotoxin Activity in Blood Sample

First, place the EA tubes to be used in tube racks and remove the caps. Use a combi-pipette to transfer 1 milliliter of the EA reagent from the bottle into tubes number 1, number 2, and number 3, by pipetting down the side of the tubes. Gently invert the blood collection tube 20 times to mix the patient&#39;s blood sample. Then, pipette 0.5 milliliters of patient blood into tube number 4 and tube number 5. Vortex tube number 4 for 10 seconds.
Place the tube racks with all of the EA test tubes into the incubator shaker, close the lid, and incubate at 37 degrees Celsius for 10 minutes. After this, open the incubator lid, and remove the tube racks from the shaker.
Vortex tube number 5. Using a sterile tip, pipette 40 microliters of blood into tubes number 1 and number 2, in duplicate.
Vortex tube number 4. Using the same pipette tip, transfer 40 microliters of blood from tube number 4 into tube number 3, in duplicate.
Vortex the six final test tubes one by one. Place the tube racks back into the incubating shaker and close the lid. Set the shaker to 100 RPM and start the motion for 14 minutes.
Insert the EA-labeled chip card into the chemiluminometer and press &#39;Start.&#39; After the 14-minute incubation, follow the instructions displayed on the chemiluminometer. Gently vortex each tube for 10 seconds before placing it onto the sample holder of the chemiluminometer.
Open the sample drawer and place tube number 1 into the sample holder. Then, close the sample drawer and wait for the Relative Light Unit reading. Repeat this reading process for tubes 2 and 3, and all duplicates as outlined in the text protocol.
After all of the tubes have been processed, the EA results will be calculated and printed automatically.
Repeat the entire assay process for each blood sample that needs to be tested. Store the EA assay kit and its components in the original sealed package, at a temperature between 2 and 25 degrees Celsius.

Air-sampled Filter Analysis for Endotoxins and DNA Content

Summary

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Detection of Endotoxin in Nano-formulations Using Limulus Amoebocyte Lysate (LAL) Assays

Production of E. coli-expressed Self-Assembling Protein Nanoparticles for Vaccines Requiring Trimeric Epitope Presentation

A Macrophage Reporter Cell Assay to Examine Toll-Like Receptor-Mediated NF-kB/AP-1 Signaling on Adsorbed Protein Layers on Polymeric Surfaces

Endotoxin Activity Assay for the Detection of Whole Blood Endotoxemia in Critically Ill Patients

Enhanced Extraction of Low-Molecular Weight DNA from Wastewater for Comprehensive Assessment of Antimicrobial Resistance

Gel-Clot Limulus Amoebocyte Lysate Assay: A Method for Bacterial Endotoxin Detection in Nanoparticle Formulations

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Endotoxin Activity Assay: A Chemiluminescence-Based Bioassay for Investigating Endotoxin Activity in Blood Sample