Diese Arbeit wurde teilweise durch die Ishaya Horowitz Fund unterstützt.

IL-8-Assay: <ol><li> Das Reaktionsgemisch enthalten die folgenden vier Komponenten in 100 ul Endvolumen von Assay-Puffer in ihren jeweiligen Konzentrationen. 10 ul der magnetische Beads mit Capture-Antikörper bei 100 Perlen / ul Endkonzentrationen, 2 ul biotinylierten IL-8-Antikörper bei 1 nano-gram/μl Endkonzentration, 1 ul Streptavidin fluoreszierendes Protein bei 20 nano-gram/μl Endkonzentration, und 1 ul IL-8 Target bei 0,48 pico-gram/μl. Die Komponenten werden nacheinander auf die Assay-Puffer aufgenommen und werden dann für 30 Minuten geschüttelt. </li><li> Ein Kontroll-Reaktion ist die gleiche Art und Weise ohne die IL-8 Target vorbereitet. </li><li> Die Reaktionen sind später ohne Trenn-oder Waschschritt in die Küvetten gestellt und überprüft mit dem MMB-System. </li></ol> MMB-System: <ol><li> Setzen Sie die Küvette in seiner Position zwischen den beiden elektromagnetische Pole. </li><li> Betreiben Sie das Modulationsstrom und 30 Sekunden warten, um die Aggregation und Kondensation der Perlen ermöglichen </li><li> Messen Sie das Signal des Lock-in-Verstärker mit einem Oszilloskop. </li></ol> Repräsentative Ergebnisse: Sichtprüfung der aggregierten Perlen präsentiert einen deutlichen Unterschied zwischen der Reaktion mit dem Ziel und der Reaktion ohne das Ziel. In allen Reaktionen mit dem Ziel, bildete die Perlen einer einzigen dichten Aggregat, das in und aus den Laserstrahl in einem zu vereinen Weise bewegt. Doch in all die Reaktion ohne das Ziel, wurden die Perlen weniger aggregiert und ihre Bewegung war weniger zu vereinen (siehe Abbildung 1). <img src="/files/ftp_upload/1935/1935fig1.jpg" alt="Abbildung 1" /> Abbildung 1: Sichtprüfung der Sandwich &quot;-Immunoassay (a), ohne das Ziel IL-8 (b) Mit dem Ziel IL-8. Der Pol Modulation Uhr (gelb) und die PMT-Ausgangssignal (Magenta) beim Erkennen von 0,48 pico-Gramm-IL-8 Target sind in Abbildung 1 dargestellt (a). Die Modulationsfrequenz für jeden Pol ist mit 2 Hz. Doch wie es theoretisch zu erwarten war, wenn die Perlen der Laserstrahl passieren, erkennt der PMT das Fluoreszenzlicht und es ist ein Spitzenwert in der PMT Ausgangsspannung. Daher ist die Demodulation Frequenz 4 Hz. Wenn die PMT-Signal und das Doppelte-Modulation Uhr (bei 4 Hz), die Sperre im Verstärker gespeist werden, erkennt der sensiblen Phase-Detektor die Synchronisation und die Ergebnisse mit hoher Spannung (siehe Abbildung 2). <img src="/files/ftp_upload/1935/1935fig2.jpg" alt="Abbildung 2" /> Abbildung 2: (a) die Modulation Uhr (gelb) und die PMT-Signal (magenta), wenn Erkennung 0,48 pico-Gramm-IL-8 Target. (B) Die Folge lock in-Verstärker Spannung an zwei verschiedenen Scans. Das Schloss in Verstärker erkannte kein Signal, wenn die Kontrollprobe getestet wurde. Diese Tatsache, zusammen mit den visuellen Unterschied in Aggregation nahe, dass die MMB-System kann eindeutig die Anwesenheit von IL-8 Target.

<ol>
	<li>Danielli, A., Arie, A., Porat, N., Ehrlich, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+fluorescent-labeled+probes+at+sub-picomolar+concentrations+by+magnetic+modulation.">Detection of fluorescent-labeled probes at sub-picomolar concentrations by magnetic modulation.</a> Optics Express. 16, 19253-19259 (2008).</li><li>Danielli, A., Porat, N., Arie, A., Ehrlich, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+homogenous+detection+of+the+Ibaraki+virus+NS3+cDNA+at+pico-molar+concentrations+by+magnetic+modulation.">Rapid homogenous detection of the Ibaraki virus NS3 cDNA at pico-molar concentrations by magnetic modulation.</a> Biosensors and Bioelectronics. 25, 858-863 (2009).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Bio-Rad "Human angiogenesis assay panel". , .</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instruction+Manual.">Instruction Manual.</a> Bio-Plex Precision Pro Cytokine Assay. , .</li></ol>

Zusammenfassend haben wir gezeigt, dass die MMB-System verwendet werden, um die Anwesenheit von IL-8 Target bei niedrigen Konzentrationen (0,5 pico-Gramm liegt die Nachweisgrenze des Bio-Plex Precision Pro Zytokin-Assays [3,4]) zu erkennen. Die Fähigkeit des Systems ist nicht auf IL-8 begrenzt und kann verwendet werden, um andere Proteine ​​zu erkennen. Die Vorteile des MMB-System sind die Fähigkeit, das Ziel schnell und ohne Trenn-oder Waschschritt zu erkennen. So erleichtert es die Erkennung und ermöglicht dem ...

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		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
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<td>Bio-Plex Pro Human Cytokine IL-8 set</td>
<td>&nbsp;</td>
<td>Bio-Rad</td>
<td>171-B5008M</td>
<td>&nbsp;</td>
<tr>
<td>Recombinant human IL-8 target</td>
<td>&nbsp;</td>
<td>Thermo Scientific</td>
<td>R202625</td>
<td>&nbsp;</td>
<tr>
<td>Biotinylated monoclonal mouse anti human IL-8 antibody G265-8</td>
<td>&nbsp;</td>
<td>BD Biosciences</td>
<td>554718</td>
<td>&nbsp;</td>
<tr>
<td>Streptavidin coupled fluorescent protein</td>
<td>&nbsp;</td>
<td>Bio-Rad</td>
<td>Streptavidin PE</td>
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rapid homogeneous detection of biological assays using magnetic modulation biosensing system

Eine magnetische Modulation Biosensorik System (MMB) [1,2] schnell und homogen erkannt biologischer Targets bei niedrigen Konzentrationen ohne Waschen oder Trennschritt. Wenn die IL-8 Target anwesend war, eine &quot;sandwich&#39;-basierter Assay magnetische Beads mit IL-8 Fänger-Antikörper an gekoppelten fluoreszierenden Proteins über die IL-8 Target und einem biotinylierten IL-8-Antikörper Streptavidin. Die magnetischen Beads werden in schwingende Bewegung durch Anlegen einer Wechselspannung Magnetfeldgradienten durch zwei elektromagnetische Pole manövriert. Die fluoreszierenden Proteine, die den magnetischen Kügelchen befestigt sind, sind in den Erfassungsbereich und ihre Bewegung in und aus einem orthogonalen Laserstrahl erzeugt eine periodische Fluoreszenzsignal, demoduliert mit synchronen Erfassung wird kondensiert. Die magnetische Modulation Biosensoren wurde bereits verwendet, um die kodierenden Sequenzen des nicht-strukturellen Ibaraki Virus-Protein 3 (NS3) komplementäre DNA (cDNA) [2] zu erkennen. Die Techniken, die in dieser Arbeit für externe Manipulation und Kondensation von Teilchen nachgewiesen werden können, für andere Anwendungen, zB Lieferung von magnetisch gekoppelt Drogen verwendet werden<em&gt; In-vivo</em&gt; Oder den Kontrast für<em&gt; In-vivo</em&gt; Imaging-Anwendungen.

Watch this Scientific Journal Video about Rapid Homogeneous Detection of Biological Assays Using Magnetic Modulation Biosensing System at JoVE.com

Rapid Homogeneous Detection of Biological Assays Using Magnetic Modulation Biosensing System

Magnetic Modulation Biosensorik System wird genutzt, um schnell, feinfühlig und einfach erkennen biologischen Assays, wie DNA-Moleküle und Proteine.

Schnelle Homogene Detektion von biologischen Assays mit magnetischen Modulation Biosensorik-System

A magnetic modulation biosensing system (MMB) [1,2] rapidly and homogeneously detected biological targets at low concentrations without any washing or ...

rapid-homogeneous-detection-biological-assays-using-magnetic

Research

JoVE Journal

Biology

9.5K Aufrufe.  Tel Aviv University. Magnetic Modulation Biosensorik System wird genutzt, um schnell, feinfühlig und einfach erkennen biologischen Assays, wie DNA-Moleküle und Proteine.

Serie: Rapid Homogeneous Detection of Biological Assays Using Magnetic Modulation Biosensing System

ELIME (Enzyme Linked Immuno Magnetic Electrochemical) Method for Mycotoxin Detection

Immunoassays are a valid alternative to the more expensive and time consuming quantitative HPLC or GC1, 2 methods for the screening detection of hazardous mycotoxins in food commodities. In this protocol we show how to fabricate and interrogate an electrochemical competitive Enzyme linked immunomagnetic assay based on the use of magnetic beads as solid support for the immunochemical chain3 and screen printed electrodes as sensing platform.
Our method aims to determine the total amount of HT-2 and T-2 toxins, mycotoxins belonging to the trichothecenes family and of great concern for human health4. The use of an antibody clone with a cross reactivity of 100% towards HT-2 and T-2 allows to simultaneously detect both toxins with similar sensitivity5.
The first step of our assay is the coating step where we immobilize HT2-KLH conjugate toxin on the surface of magnetic beads. After a blocking step, necessary to avoid non-specific absorptions, the addition of a monoclonal antibody allows the competition between immobilized HT-2 and free HT-2 or T-2 present in the sample or dissolved in a standard solution.
At the end of the competition step, the amount of monoclonal antibody linked to the immobilized HT-2 will be inversely proportional to the amount of toxin in the sample solution.
A secondary antibody labeled with alkaline phosphatase (AP) is used to reveal the binding between the specific antibody and the immobilized HT-2. The final measurement step is performed by dropping an aliquot of magnetic bead suspension, corresponding to a specific sample/standard solution, on the surface of a screen-printed working electrode; magnetic beads are immobilized and concentrated by means of a magnet placed precisely under the screen-printed electrode. After two minutes of incubation between magnetic beads and a substrate for AP, the enzymatic product is detected by Differential Pulse Voltammetry (DPV) using a portable instrument (PalmSens) also able to initiate automatically eight measurements within an interval of few seconds.

ELIME Enzyme Linked Immuno Magnetic Electrochemical Method for Mycotoxin Detection

A protocol to detect trichothecenes (mycotoxins of concern for human health) using a newly developed screening method based on a competitive immunochemical method and a final electrochemical detection is demonstrated.

ELIME (Enzyme Linked Immuno Magnetic Elektrochemische) Verfahren zur Mykotoxin-Erkennung

Immunoassays are a valid alternative to the more expensive and time consuming quantitative HPLC or GC1, 2 methods for the screening detection of hazardous ...

Forschung

Biologie

Analysis of Schwann-astrocyte Interactions Using In Vitro Assays

Schwann cells are one of the commonly used cells in repair strategies following spinal cord injuries. Schwann cells are capable of supporting axonal regeneration and sprouting by secreting growth factors 1,2 and providing growth promoting adhesion molecules 3 and extracellular matrix molecules 4. In addition they myelinate the demyelinated axons at the site of injury 5.
However following transplantation, Schwann cells do not migrate from the site of implant and do not intermingle with the host astrocytes 6,7. This results in formation of a sharp boundary between the Schwann cells and astrocytes, creating an obstacle for growing axons trying to exit the graft back into the host tissue proximally and distally. Astrocytes in contact with Schwann cells also undergo hypertrophy and up-regulate the inhibitory molecules 8-13.
In vitro assays have been used to model Schwann cell-astrocyte interactions and have been important in understanding the mechanism underlying the cellular behaviour.
These in vitro assays include boundary assay, where a co-culture is made using two different cells with each cell type occupying different territories with only a small gap separating the two cell fronts. As the cells divide and migrate, the two cellular fronts get closer to each other and finally collide. This allows the behaviour of the two cellular populations to be analyzed at the boundary. Another variation of the same technique is to mix the two cellular populations in culture and over time the two cell types segregate with Schwann cells clumped together as islands in between astrocytes together creating multiple Schwann-astrocyte boundaries.
The second assay used in studying the interaction of two cell types is the migration assay where cellular movement can be tracked on the surface of the other cell type monolayer 14,15. This assay is commonly known as inverted coverslip assay. Schwann cells are cultured on small glass fragments and they are inverted face down onto the surface of astrocyte monolayers and migration is assessed from the edge of coverslip.
Both assays have been instrumental in studying the underlying mechanisms involved in the cellular exclusion and boundary formation. Some of the molecules identified using these techniques include N-Cadherins 15, Chondroitin Sulphate proteoglycans(CSPGs) 16,17, FGF/Heparin 18, Eph/Ephrins19.
This article intends to describe boundary assay and migration assay in stepwise fashion and elucidate the possible technical problems that might occur.

Analysis of Schwann-astrocyte Interactions Using In Vitro Assays

This article intends to describe in stepwise fashion the commonly used in vitro assays used in studying Schwann cell-asrtocyte interactions.

Analyse von Schwann-Astrozyten Wechselwirkungen mit In Vitro Assays

Schwann cells are one of the commonly used cells in repair strategies following spinal cord injuries. Schwann cells are capable of supporting axonal ...

Rapid PCR Thermocycling using Microscale Thermal Convection

Many molecular biology assays depend in some way on the polymerase chain reaction (PCR) to amplify an initially dilute target DNA sample to a detectable concentration level. But the design of conventional PCR thermocycling hardware, predominantly based on massive metal heating blocks whose temperature is regulated by thermoelectric heaters, severely limits the achievable reaction speed1. Considerable electrical power is also required to repeatedly heat and cool the reagent mixture, limiting the ability to deploy these instruments in a portable format.
Thermal convection has emerged as a promising alternative thermocycling approach that has the potential to overcome these limitations2-9. Convective flows are an everyday occurrence in a diverse array of settings ranging from the Earth's atmosphere, oceans, and interior, to decorative and colorful lava lamps. Fluid motion is initiated in the same way in each case: a buoyancy driven instability arises when a confined volume of fluid is subjected to a spatial temperature gradient. These same phenomena offer an attractive way to perform PCR thermocycling. By applying a static temperature gradient across an appropriately designed reactor geometry, a continuous circulatory flow can be established that will repeatedly transport PCR reagents through temperature zones associated with the denaturing, annealing, and extension stages of the reaction (Figure 1). Thermocycling can therefore be actuated in a pseudo-isothermal manner by simply holding two opposing surfaces at fixed temperatures, completely eliminating the need to repeatedly heat and cool the instrument.
One of the main challenges facing design of convective thermocyclers is the need to precisely control the spatial velocity and temperature distributions within the reactor to ensure that the reagents sequentially occupy the correct temperature zones for a sufficient period of time10,11. Here we describe results of our efforts to probe the full 3-D velocity and temperature distributions in microscale convective thermocyclers12. Unexpectedly, we have discovered a subset of complex flow trajectories that are highly favorable for PCR due to a synergistic combination of (1) continuous exchange among flow paths that provides an enhanced opportunity for reagents to sample the full range of optimal temperature profiles, and (2) increased time spent within the extension temperature zone the rate limiting step of PCR. Extremely rapid DNA amplification times (under 10 min) are achievable in reactors designed to generate these flows.

We describe a novel method to perform DNA replication via the polymerase chain reaction (PCR). Thermal convection is harnessed to continuously shuttle reagents between denaturing, annealing, and extension conditions by maintaining opposing surfaces of the reactor at constant temperature. This inherently simple design promises to make rapid PCR more accessible.

Rapid PCR Thermocycling mit Microscale thermische Konvektion

Many molecular biology assays depend in some way on the polymerase chain reaction (PCR) to amplify an initially dilute target DNA sample to a detectable ...

High-throughput Screening and Biosensing with Fluorescent C. elegans Strains

High-throughput screening (HTS) is a powerful approach for identifying chemical modulators of biological processes. However, many compounds identified in screens using cell culture models are often found to be toxic or pharmacologically inactive in vivo1-2. Screening in whole animal models can help avoid these pitfalls and streamline the path to drug development.
C. elegans is a multicellular model organism well suited for HTS. It is small (&lt;1 mm) and can be economically cultured and dispensed in liquids. C. elegans is also one of the most experimentally tractable animal models permitting rapid and detailed identification of drug mode-of-action3.
We describe a protocol for culturing and dispensing fluorescent strains of C. elegans for high-throughput screening of chemical libraries or detection of environmental contaminants that alter the expression of a specific gene. Large numbers of developmentally synchronized worms are grown in liquid culture, harvested, washed, and suspended at a defined density. Worms are then added to black, flat-bottomed 384-well plates using a peristaltic liquid dispenser. Small molecules from a chemical library or test samples (e.g., water, food, or soil) can be added to wells with worms. In vivo, real-time fluorescence intensity is measured with a fluorescence microplate reader. This method can be adapted to any inducible gene in C. elegans for which a suitable reporter is available. Many inducible stress and developmental transcriptional pathways are well defined in C. elegans and GFP transgenic reporter strains already exist for many of them4. When combined with the appropriate transgenic reporters, our method can be used to screen for pathway modulators or to develop robust biosensor assays for environmental contaminants. 
We demonstrate our C. elegans culture and dispensing protocol with an HTS assay we developed to monitor the C. elegans cap &#x2018;n&#x2019; collar transcription factor SKN-1. SKN-1 and its mammalian homologue Nrf2 activate cytoprotective genes during oxidative and xenobiotic stress5-10. Nrf2 protects mammals from numerous age-related disorders such as cancer, neurodegeneration, and chronic inflammation and has become a major chemotherapeutic target11-13.Our assay is based on a GFP transgenic reporter for the SKN-1 target gene gst-414, which encodes a glutathione-s transferase6. The gst-4 reporter is also a biosensor for xenobiotic and oxidative chemicals that activate SKN-1 and can be used to detect low levels of contaminants such as acrylamide and methyl-mercury15-16.

High-throughput Screening and Biosensing with Fluorescent C. elegans Strains

A procedure for liquid-based culturing and dispensing of C. elegans strains expressing fluorescent reporter proteins is described that does not require expensive sorting equipment. This approach can be applied to numerous inducible C. elegans genes for drug discovery or biosensing of contaminants.

High-Throughput-Screening und Biosensorik mit Fluorescent C. elegans Die Stämme

High-throughput screening (HTS) is a powerful approach for identifying chemical modulators of biological processes.  However, many compounds identified in ...

Detection of Protein Interactions in Plant using a Gateway Compatible Bimolecular Fluorescence Complementation (BiFC) System

We have developed a BiFC technique to test the interaction between two proteins in vivo. This is accomplished by splitting a yellow fluorescent protein (YFP) into two non-overlapping fragments. Each fragment is cloned in-frame to a gene of interest. These constructs can then be co-transformed into Nicotiana benthamiana via Agrobacterium mediated transformation, allowing the transit expression of fusion proteins. The reconstitution of YFP signal only occurs when the inquest proteins interact 1-7. To test and validate the protein-protein interactions, BiFC can be used together with yeast two hybrid (Y2H) assay. This may detect indirect interactions which can be overlooked in the Y2H. Gateway technology is a universal platform that enables researchers to shuttle the gene of interest (GOI) into as many expression and functional analysis systems as possible8,9. Both the orientation and reading frame can be maintained without using restriction enzymes or ligation to make expression-ready clones. As a result, one can eliminate all the re-sequencing steps to ensure consistent results throughout the experiments. We have created a series of Gateway compatible BiFC and Y2H vectors which provide researchers with easy-to-use tools to perform both BiFC and Y2H assays10. Here, we demonstrate the ease of using our BiFC system to test protein-protein interactions in N. benthamiana plants.

Detection of Protein Interactions in Plant using a Gateway Compatible Bimolecular Fluorescence Complementation BiFC System

We have developed a technique to test protein-protein interactions in plant. A yellow fluorescent protein (YFP) is split into two non-overlapping fragments. Each fragment is cloned in-frame to a gene of interest via Gateway system, enabling expression of fusion proteins. Reconstitution of YFP signal only occurs when the inquest proteins interact.

Detektion von Protein-Wechselwirkungen in Plant mit einem Gateway kompatibel bimolekularen Fluoreszenz Komplementation (BIFC) System

We have developed a BiFC technique to test the interaction between two proteins in vivo. This is accomplished by splitting a yellow fluorescent protein ...

Rapid Protocol for Preparation of Electrocompetent Escherichia coli and Vibrio cholerae

Electroporation has become a widely used method for rapidly and efficiently introducing foreign DNA into a wide range of cells. Electrotransformation has become the method of choice for introducing DNA into prokaryotes that are not naturally competent. Electroporation is a rapid, efficient, and streamlined transformation method that, in addition to purified DNA and competent bacteria, requires commercially available gene pulse controller and cuvettes. In contrast to the pulsing step, preparation of electrocompetent cells is time consuming and labor intensive involving repeated rounds of centrifugation and washes in decreasing volumes of sterile, cold water, or non-ionic buffers of large volumes of cultures grown to mid-logarithmic phase of growth. Time and effort can be saved by purchasing electrocompetent cells from commercial sources, but the selection is limited to commonly employed E. coli laboratory strains. We are hereby disseminating a rapid and efficient method for preparing electrocompetent E. coli, which has been in use by bacteriology laboratories for some time, can be adapted to V. cholerae and other prokaryotes. While we cannot ascertain whom to credit for developing the original technique, we are hereby making it available to the scientific community.

Rapid Protocol for Preparation of Electrocompetent Escherichia coli and Vibrio cholerae

Electroporation is a commonly employed method for introducing DNA into bacteria in a process known as transformation. Traditional protocols for the preparation of electrocompetent cells are time consuming and labor intensive. This article describes an alternate, rapid, and efficient method for the preparation of electrocompetent cells presently employed by some laboratories.

Rapid-Protokoll für die Herstellung von Elektrokompetente<em&gt; Escherichia coli</em&gt; Und<em&gt; Vibrio cholerae</em

Electroporation has become a widely used method for rapidly and efficiently introducing foreign DNA into a wide range of cells. Electrotransformation has ...

Rapid and Efficient Zebrafish Genotyping Using PCR with High-resolution Melt Analysis

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic tools have been introduced, including multiple strategies for inducing mutations and generating transgenic lines. However, large-scale screening is limited by traditional genotyping methods, which are time-consuming and labor-intensive. Here we describe a technique to analyze zebrafish genotypes by PCR combined with high-resolution melting analysis (HRMA).&#160;This approach is rapid, sensitive, and inexpensive, with lower risk of contamination artifacts.&#160;Genotyping by PCR with HRMA can be used for embryos or adult fish, including in high-throughput screening protocols.

PCR combined with high-resolution melt analysis (HRMA) is demonstrated as a rapid and efficient method to genotype zebrafish.

Schnelle und effiziente Verwendung von Zebrafisch-Genotypisierung PCR mit Hochauflösende Schmelzanalyse

Zebrafish is a powerful vertebrate model system for studying development, modeling disease, and performing drug screening. Recently a variety of genetic ...

Simple Bulk Readout of Digital Nucleic Acid Quantification Assays

Digital assays are powerful methods that enable detection of rare cells and counting of individual nucleic acid molecules. However, digital assays are still not routinely applied, due to the cost and specific equipment associated with commercially available methods. Here we present a simplified method for readout of digital droplet assays using a conventional real-time PCR instrument to measure bulk fluorescence of droplet-based digital assays.
We characterize the performance of the bulk readout assay using synthetic droplet mixtures and a droplet digital multiple displacement amplification (MDA) assay. Quantitative MDA particularly benefits from a digital reaction format, but our new method&#160;applies to any digital assay. For established digital assay protocols such as digital PCR, this method serves to speed up and simplify assay readout.
Our bulk readout methodology brings the advantages of partitioned assays without the need for specialized readout instrumentation. The principal limitations of the bulk readout methodology are reduced dynamic range compared with droplet-counting platforms and the need for a standard sample, although the requirements for this standard are less demanding than for a conventional real-time experiment. Quantitative whole genome amplification (WGA) is used to test for contaminants in WGA reactions and is the most sensitive way to detect the presence of DNA fragments with unknown sequences, giving the method great promise in diverse application areas including pharmaceutical quality control and astrobiology.

We describe an endpoint digital assay for quantifying nucleic acids with a simplified (analog) readout. We measure bulk fluorescence of droplet-based digital assays using a standard qPCR machine rather than specialized instrumentation and confirm our results by microscopy.

Einfache Massen Auslesen des digitalen Nukleinsäure Quantifizierung Assays

Digital assays are powerful methods that enable detection of rare cells and counting of individual nucleic acid molecules. However, digital assays are ...

High Content Screening Analysis to Evaluate the Toxicological Effects of Harmful and Potentially Harmful Constituents (HPHC)

Cigarette smoke (CS) is a major risk factor for cardiovascular and lung diseases. Because CS is a complex aerosol containing more than 7,000 chemicals1 it is challenging to assess the contributions of individual constituents to its overall toxicity. Toxicological profiles of individual constituents as well as mixtures can be however established in vitro, by applying high through-put screening tools, which enable the profiling of Harmful and Potentially Harmful Constituents (HPHCs) of tobacco smoke, as defined by the U.S. Food and Drug Administration (FDA).2
For an initial assessment, an impedance-based instrument was used for a real-time, label-free assessment of the compound&#39;s toxicity. The instrument readout relies on cell adhesion, viability and morphology that all together provide an overview of the cell status. A dimensionless parameter, named cell index, is used for quantification. A set of different staining protocols was developed for a fluorescence imaging-based investigation and a HCS platform was used to gain more in-depth information on the kind of cytotoxicity elicited by each HPHC.
Of the 15 constituents tested, only five were selected for HCS-based analysis as they registered a computable LD50 (&#60; 20 mM). These included 1-aminonaphtalene, Arsenic (V), Chromium (VI), Crotonaldehyde and Phenol. Based on their effect in the HCS, 1-aminonaphtalene and Phenol could be identified to induce mitochondrial dysfunction, and, together with Chromium (VI) as genotoxic based on the increased histone H2AX phosphorylation. Crotonaldehyde was identified as an oxidative stress inducer and Arsenic as a stress kinase pathway activator.
This study demonstrates that a combination of impedance-based and HCS technologies provides a robust tool for in vitro assessment of CS constituents.

High Content Screening Analysis to Evaluate the Toxicological Effects of Harmful and Potentially Harmful Constituents HPHC

The objective of the study was to assess the biological impact of 15 cigarette smoke constituents using a combination of an impedance-based real time cell analyzer and a high-content screening (HCS)-based platform for toxicological assessment in vitro. This study provides information on effective doses, toxicity and modes of action of the tested compounds.

High Content Screening-Analyse die toxikologischen Wirkungen von gefährlichen und potenziell gefährlichen Inhaltsstoffe (HPHC) zur Bewertung

Cigarette smoke (CS) is a major risk factor for cardiovascular and lung diseases. Because CS is a complex aerosol containing more than 7,000 chemicals1 it ...

Rapid Freezing using Sandwich Freezing Device for Good Ultrastructural Preservation of Biological Specimens in Electron Microscopy

Chemical fixation has been used for observing the ultrastructure of cells and tissues. However, this method does not adequately preserve the ultrastructure of cells; artifacts and extraction of cell contents are usually observed. Rapid freezing is a better alternative for the preservation of cell structure. Sandwich freezing of living yeast or bacteria followed by freeze-substitution has been used for observing the exquisite natural ultrastructure of cells. Recently, sandwich freezing of glutaraldehyde-fixed cultured cells or human tissues has also been used to reveal the ultrastructure of cells and tissues. 
These studies have thus far been carried out with a handmade sandwich freezing device, and applications to studies in other laboratories have been limited. A new sandwich freezing device has recently been fabricated and is now commercially available. The present paper shows how to use the sandwich freezing device for rapid freezing of biological specimens, including bacteria, yeast, cultured cells, isolated cells, animal and human tissues, and viruses. Also shown is the preparation of specimens for ultrathin sectioning after rapid freezing and procedures for freeze-substitution, resin embedding, trimming of blocks, cutting of ultrathin sections, recovering of sections, staining, and covering of grids with support films.

Here we show how to use the sandwich freezing device for rapid freezing of biological specimens, including bacteria, yeast, cultured cells, isolated cells, animal and human tissues, and viruses. We also show how to prepare specimens for ultrathin sectioning after rapid freezing.