Name: using tomoauto: a protocol for high-throughput automated cryo-electron tomography
Uploaded: 2016-01-30T15:00:00
Description: Watch this Scientific Journal Video about Using Tomoauto: A Protocol for High-throughput Automated Cryo-electron Tomography at JoVE.com

We thank Dr. William Margolin for comments. We are grateful for the support on SerialEM from Drs. David Mastronarde and Chen Xu. D.M., B.H. and J.L. were supported by Grant R01AI087946 from the National Institute of Allergy and Infectious Diseases, Grants R01GM110243 and R01GM107629 from the National Institute of General Medical Sciences (NIGMS), and Grant AU-1714 from the Welch Foundation. The direct electron detector was funded by National Institutes of Health Award S10OD016279.

1. Minicell Preparation
<ol>
	<li>To make S. flexneri minicells, transform 1 &#181;l of plasmid pBS58, which constitutively expresses Escherichia coli cell division genes ftsQ, ftsA, and ftsZ from a low-copy spectinomycin-resistant plasmid into 5 &#181;l electrocompetent Streptomycin-resistant serotype 5a (M90T-Sm) cells by electroporation at 2.5 kV for 5 msec in 1 mm cuvettes.</li>
	<li>Store minicell samples at -80 &#176;C in 15% glycerol in a 1.5 ml cryogenic microtube. When ready...

<ol>
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N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+electron+microscope+tomography+using+robust+prediction+of+specimen+movements.">Automated electron microscope tomography using robust prediction of specimen movements.</a> J. Struct. Biol. 152 (1), 36-51 (2005).</li><li>Zheng, S. Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=UCSF+tomography:+an+integrated+software+suite+for+real-time+electron+microscopic+tomographic+data+collection,+alignment+and+reconstruction.">UCSF tomography: an integrated software suite for real-time electron microscopic tomographic data collection, alignment and reconstruction.</a> J. Struct. 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The high-throughput method described here enabled us to process 1,917 cryo tilt-series and produce over 4,500 sub-tomograms of the intact S. flexneri injectisome19. The collected data led to the detailed characterization of in situ injectisome, including the cytoplasmic sorting complex. The method was also utilized to visualize several mutant cells with specific deletion of putative protein components, which helped elucidate the composition of the sorting platform of the injectisome....

Type III secretion systems (T3SS) are essential virulence determinants for many Gram-negative pathogens. The injectisome, also known as the needle complex, is the central T3SS machine required for direct translocation of effector proteins from the bacterium into eukaryotic host cells1, 2. The injectisome comprises an extracellular needle, a basal body, and a cytoplasmic complex also known as the sorting complex3. Previous studies have elucidated 3-D structures of purified injectisomes from Salmonella and Shigella, along with the atomic structures of major basal body proteins4, 5. Recent in situ structures of injectisomes from Salmonella, Shigella, and Yersinia were revealed by cryo-ET6, 7. However, the cytoplasmic complex, essential for effector selection and needle assembly, has not been visualized in those structures.
Cryo-ET is the most suitable technique for imaging molecular machinery at nanometer resolution within its native cellular context (in situ). Nevertheless, the achievable resolution by cryo-ET is limited by specimen thickness. To overcome the drawback, we imaged intact injectisomes in a virulent Shigella flexneri strain that was genetically modified to produce minicells thin enough for cryo-ET. Another limitation of cryo-ET is the sensitivity of the sample to the radiation induced by the electron beam, which very quickly destroys the high-resolution information in the sample. As a result, extremely low doses are used for individual tilt-images so that a suitable dose can be distributed amongst the full tilt-series. This greatly lowers the signal-to-noise ratio (SNR) in the final reconstruction, which makes it difficult to differentiate the structural features of the subject from the large amount of noise in the tomogram and limits the resolution that can be achieved by cryo-ET. Conventional image processing such as Fourier and real-space filters as well as down sampling can be used to increase contrast, but at the expense of filtering out much of the high-resolution information. Recently, sub-tomogram averaging has made it possible to greatly increase the SNR and subsequently the final resolution in some cases to sub-nanometer levels8, 9. A more detailed analysis of complexes is made possible by computationally extracting thousands of sub-tomograms containing the areas of interest from the original tomograms and then aligning and averaging the sub-tomograms to determine in situ complex structures with higher SNR and higher resolution. These methods can be integrated with genetic approaches to provide even greater insights into macromolecular assemblies and their dynamic conformations in the native cellular context.
In general, tens or even hundreds of thousand sub-tomograms need to be averaged in order to determine high-resolution structures in situ. The acquisition of a sufficient number of tilt-series needed to produce this large number of sub-tomograms quickly becomes a bottleneck. The resulting tilt-series are often affected by beam-induced shift, stage backlash, as well as magnification, rotation and skew defects, which must be solved to bring the tilt-series into alignment prior to reconstruction. The tilt series is typically aligned by tracking gold fiducial markers, which are traditionally selected manually through inspection of the tilt-series, causing yet another bottleneck. Many software packages have been developed for automated tilt-series acquisition through computer-controlled electron microscopes10, 11, 12, tilt-series alignment and reconstruction13, 14 and sub-tomogram averaging15-18. As these packages handle discrete operations in the workflow of cryo-ET, it becomes desirable to build a higher level of abstraction into the process to systematically streamline the entire scheme into a single pipeline. Therefore, we developed a software wrapper library &#34;tomoauto&#34; designed to organize a number of these packages into a single semi-automated unit, allowing for simple user operation while maintaining full configuration of each component in a centralized manner. The library is open-source, well documented, continually developed and freely available for use, tailored development or further integration by means of an online remote source code repository (http://github.com/DustinMorado/tomoauto).
This high-throughput cryo-ET pipeline has been utilized to visualize intact injectisomes in S. flexneri minicells. A total of 1,917 tomograms were generated using this method, revealing a high-resolution in situ structure of the intact machine including the cytoplasmic sorting platform determined by sub-tomogram averaging19. Together with molecular modeling of wild-type and mutant machines, our high-throughput pipeline provides a new avenue to understand the structure and function of the intact injectisome in the native cellular context.

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		<tr height="21">
			<td height="21" style="height:21px;width:160px;">Glycerol</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:116px;">G9012</td>
			<td style="width:164px;"></td>
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			<td height="21" style="height:21px;width:160px;">Tyrptic Soy Broth</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:116px;">22092</td>
			<td style="width:164px;"></td>
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			<td height="21" style="height:21px;width:160px;">Spectinomycin</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:116px;">S0692</td>
			<td style="width:164px;"></td>
		</tr>
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			<td height="42" style="height:42px;width:160px;">Electroporation Apparatus</td>
			<td style="width:211px;">Bio-rad</td>
			<td>165-2100</td>
			<td style="width:164px;"></td>
		</tr>
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			<td height="21" style="height:21px;width:160px;">1 mm Cuvette</td>
			<td style="width:211px;">BTX</td>
			<td>45-0124</td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:160px;">1.5 mL Cryogenic Tube</td>
			<td style="width:211px;">Thermoscientific</td>
			<td>5000-1020</td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">1.5 mL Microcentrifuge Tube</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td>Z336769</td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:160px;">Holey Carbon Grids</td>
			<td style="width:211px;">Quantifoil 
			(Electron Microscopy Sciences)</td>
			<td style="width:116px;">Q2100CR2</td>
			<td style="width:164px;">R2/2 200 Cu</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Glow Discharge Device</td>
			<td style="width:211px;">In-House</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">Commercial Alternative Available</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Vacuum Desiccator</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:116px;">Z119016&#160;</td>
			<td style="width:164px;">Used in In-House Glow Discharge Device</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:160px;">High-Frequency Generator</td>
			<td style="width:211px;">Electro-Technic Products</td>
			<td style="width:116px;">BD-10A</td>
			<td style="width:164px;">Used in In-House Glow Discharge Device.&#160; CAUTION: This device generates high voltages.</td>
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			<td height="21" style="height:21px;width:160px;">Centrifuge</td>
			<td style="width:211px;"></td>
			<td style="width:116px;"></td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:160px;">Forceps</td>
			<td style="width:211px;">Dumont 
			(Electron Microscopy Sciences)</td>
			<td style="width:116px;">72705-D</td>
			<td style="width:164px;">Style 5 Anti-magnetic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:160px;">Colliodal Gold</td>
			<td style="width:211px;">Aurion</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">BSA 10nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:160px;">Filter Paper</td>
			<td style="width:211px;">Whatman</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">#2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:160px;">Ethane&#160;</td>
			<td style="width:211px;">Matheson Tri-Gas</td>
			<td style="width:116px;">UN1035</td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:160px;">Nitrogen</td>
			<td style="width:211px;">Matheson Tri-Gas</td>
			<td style="width:116px;">UN1977</td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Plunger Device</td>
			<td style="width:211px;">In-House</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">Commercial Alternative Available</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Cryogenic Grid Storage Box</td>
			<td style="width:211px;">Electron Microscopy Sciences</td>
			<td style="width:116px;">71166-30</td>
			<td style="width:164px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Transmission Electron Microscope</td>
			<td style="width:211px;">FEI</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">Tecnai Polara F30 
			(300 KeV)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Direct Detection Device Camera</td>
			<td style="width:211px;">Gatan</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">K2 Summit</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:160px;">Tomogram Acquisiton Software</td>
			<td style="width:211px;">SerialEM</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">http://bio3d.colorado.eud/SerialEM Alternatives: UCSF Tomography, Leginon, FEI Batch Tomography</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:160px;">Beam-induced Motion Correction Software</td>
			<td style="width:211px;">MOTIONCORR</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">http://cryoem.ucsf.edu/software/driftcorr.html Requires &#62;2GB Nvidia GPU</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:160px;">Tilt-Series Alignment Software</td>
			<td style="width:211px;">IMOD</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">http://bio3d.colorado.edu/IMOD Alternatives: XMIPP, Protomo</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:160px;">Automatic Fiducial Marker Modelling Software</td>
			<td style="width:211px;">IMOD</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">Alternatives: RAPTOR (Included in IMOD0 
			(Usable in tomoauto)</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:160px;">CTF Determination Software</td>
			<td style="width:211px;">IMOD</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">Alternatives: CTFFIND http://grigoriefflab.janelia.org/ctf 
			(Usable in tomoauto)</td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:160px;">Tilt-Series Reconstruction Software</td>
			<td style="width:211px;">tomo3d</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">https://sites.google.com/site/3demimageprocessing/tomo3d Alternatives: IMOD, XMIPP http://xmipp.cnb.csic.es , Protomo</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:160px;">Tilt-Series Automated Processing Software</td>
			<td style="width:211px;">tomoauto</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">https://github.com/DustinMorado/tomoauto</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:160px;">Particle Picking Software</td>
			<td style="width:211px;">i3</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">http://www.electrontomography.org Alternatives: IMOD</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:160px;">Subvolume Averaging Software</td>
			<td style="width:211px;">i3</td>
			<td style="width:116px;"></td>
			<td style="width:164px;">Alternatives: PEET http://bio3d.colorado.edu/PEET, Dynamo https://dynamo.bioz.unibas.ch , PyTom http://pytom.org</td>
		</tr>
	</tbody>
</table>

using tomoauto: a protocol for high-throughput automated cryo-electron tomography

Cryo-electron tomography (Cryo-ET) is a powerful three-dimensional (3-D) imaging technique for visualizing macromolecular complexes in their native context at a molecular level. The technique involves initially preserving the sample in its native state by rapidly freezing the specimen in vitreous ice, then collecting a series of micrographs from different angles at high magnification, and finally computationally reconstructing a 3-D density map. The frozen-hydrated specimen is extremely sensitive to the electron beam and so micrographs are collected at very low electron doses to limit the radiation damage. As a result, the raw cryo-tomogram has a very low signal to noise ratio characterized by an intrinsically noisy image. To better visualize subjects of interest, conventional imaging analysis and sub-tomogram averaging in which sub-tomograms of the subject are extracted from the initial tomogram and aligned and averaged are utilized to improve both contrast and resolution. Large datasets of tilt-series are essential to understanding and resolving the complexes at different states, conditions, or mutations as well as obtaining a large enough collection of sub-tomograms for averaging and classification. Collecting and processing this data can be a major obstacle preventing further analysis. Here we describe a high-throughput cryo-ET protocol based on a computer-controlled 300kV cryo-electron microscope, a direct detection device (DDD) camera and a highly effective, semi-automated image-processing pipeline software wrapper library tomoauto developed in-house. This protocol has been effectively utilized to visualize the intact type III secretion system (T3SS) in Shigella flexneri minicells. It can be applicable to any project suitable for cryo-ET.

Samples of minicells S. flexneri were collected and processed as showed in the schematic Figure 1 using tomoauto following the pipeline detailed in Figure 2. Tilt-series were collected using SerialEM10, which allows for high-throughput tilt-series acquisition at points designated by the user on low-magnification montage maps (Figure 3). Micrographs were collected using dose-fractionation mode on a dire...

Watch this Scientific Journal Video about Using Tomoauto: A Protocol for High-throughput Automated Cryo-electron Tomography at JoVE.com

Using Tomoauto: A Protocol for High-throughput Automated Cryo-electron Tomography

We present a protocol on how to utilize high-throughput cryo-electron tomography to determine high resolution in situ structures of molecular machines. The protocol permits large amounts of data to be processed, avoids common bottlenecks and reduces resource downtime, allowing the user to focus on important biological questions.

Cryo-electron tomography (Cryo-ET) is a powerful three-dimensional (3-D) imaging technique for visualizing macromolecular complexes in their native ...

The overall goal of this procedure is to help users establish a high-throughput collection and processing pipeline of cryo-electron tomography. This method can help answer key questions in the cryo-electron tomorgraphy field, such as:how do I handle data collected with new generation detectors, and process a huge amount of data produced by automated tilt-series collection software? The main advantage with this technique is that the user can configure multiple software packages in a unifying manner, to finding an efficient pipeline for automated tilt-series processing, allowing for more time to be spent on tomogram analysis.Generally, individuals new to cryo-ET will struggle because many tedious steps are required to handle massive data generated from the electron microscope. We first had the idea for this development five years ago when we had to manually go through hundreds of steps to get a 3D reconstruction of one bacteria. In advance, consult the text protocol on preparing the Shigella flexneri minicells.Then, prepare the electron microscopy grids as explained by an existing JoVE publication and also documented in the text protocol. After having loaded the EM stage with the collection of minicells embedded in vitrified ice, start collecting low-magnification maps for the tilt-series. While viewing the fluorescent screen at low magnification, of about 2300x, find grid squares that are acceptable to image.This location should contain thin ice and the subject of interest with no contaminants. Next, adjust the view to the center of the grid square, and click on the Add Stage Position button to save the location. Then, repeat the process until all the acceptable grid squares have had their location saved.The next step begins with opening a new montage file. In the setup dialog, set the X and Y so that the entire grid square is captured. For a standard, 200 mesh grid, make a 10 by 10 space with a high Binning value, like eight.Also toggle the move stage instead of shifting image option and the skip correlations used to align pieces option. Now, in the Navigator window, select the first stage position to be acquired using the Acquire toggle. Continue doing this for each stage position.Next, under the Navigator menu, click on Acquire at Points. In the dialog box that opens up, toggle acquire map image and rough eucentricity. Untoggle all the other options.Then, click proceed, and a montage will be made for each stage position. Continue working with the SerialEM software. In the Navigator, select the acquired maps, and click on Load Map.Then, click on Add Points, and select the points on the map where the tilt-series should be acquired. After making the selections, click Stop Adding Points and repeat the process with each collected map. Next, open the parameters under the Camera menu, and set the Focus, Trial, and Record modes.The option to record dose-fractionated data may be of special interest, and that can be specified under the Record options. To proceed, select one of the points in the currently viewed map, and toggle the tilt-series option in the Navigator window. In the dialog box that opens, choose the parameters for the tilt-series.Then, repeat the process of toggling tilt-series option for each of the selected points in the map. Next, from the Navigator start the Acquire at Points option. Under the dialog box, toggle the Preliminary Tasks, Realign to item, Autofocus, and rough eucentricity.Then, set the Primary Task to acquire tilt-series, and choose close column vals at end to close the column when all the points have been collected. When the process is executed, a tilt-series will be collected at each point toggled for tilt-series collection in each map. With the original tilt-series, the output log from SerialEM, and the individual dose-fractionated images all in the current working directory, in a terminal, execute the following command to remove the beam-induced motion artifact.Proceed with aligning and reconstructing the tilt-series. Type in tomoauto command in the terminal as follows. To the command, append the filename of the tilt-series to process, followed by the fiducial diameter in nanometers.If CTF processing is not desired, simply omit the option from the command. This command is the main use of tomoauto, allowing users to execute all the processes involved in aligning a tilt-series, which originally required manual user intervention, in a single command, allowing users to quickly script batch processing. Now, using the 3dmod command, look over the aligned tilt-series for any glaring errors.Here filename is the name of the tilt-series without suffix. Then, inspect the estimated CTF with the command shown here. Again, filename is the name of the tilt-series without suffix.Also, in the output log produced by the tomoauto command, check the residual error of the alignment. This is a quantitative measure of the alignment's overall quality. If the alignment is acceptable, then proceed with computing the reconstruction.This command is set to correct the CTF, and erase the fiducial markers used in alignment from the tilt-series. To skip the visual inspection, and go directly to the reconstruction, use this command. Tomoauto has many accessible options.One in particular is the ability to include local configurations described by an auxiliary file, according to the tomoauto documentation. Include this file's name in the commandline dialog using the local configuration option before appending the tilt-series filename. The ability to create local configuration files is the most powerful feature of tomoauto, allowing users to fully configure every command used, tuning execution to specific or difficult data sets while maintaining the automated processing.Within the test protocol are additional instructions on how to execute sub-tomogram averaging. Following the described protocols, two aligned tilt-series were made with tomoauto. The fine alignment is calculated from a model that ideally defines fiducial marker coordinates.At 50 degrees, one tilt-series tracked the gold particles correctly, indicating an acceptable alignment. While, in the case of the second tilt-series, several model points, shown in red, strayed from their corresponding gold marker, illustrating the model did not produce suitable alignment. When tilt-series are collected, tomoauto successfully aligns 80 to 90%of the collected tilt-series.After reconstruction, the final tomogram is a 3D volume of the image sample. This can then be used for cellular annotation by segmentation, or sub-tomogram averaging to obtain higher resolution information of the molecular machinery within the sample. The 2.7 nanometers sub-tomogram average of the attached Shigella flexneri deposited in the EMDB shows the large improvement of this technique over viewing the injectisome in a single tomogram.After watching this video, you should have a good understanding of how to collect and process cryo-electron tomography data using SerialEM and tomoauto in an automated, high-throughput manner. Once mastered, this technique can be used to collect almost 100 tilt-series in a day, if it is performed properly, and align a tilt-series in 20 minutes. While attempting this procedure, it is important to remember to always check the quality of tilt-series alignment.If a set of tilt-series does not align well, try aligning manually, and transfer the parameters to a local configuration. Following this procedure, other methods like sub-tomogram averaging can be performed in order to answer additional questions, like determining the higher-resolution structure of macro-molecular complexes. After its development, this technique paved the way for researchers in the field of cryo-EM to explore high-resolution in situ structures in bacteria, viruses, and other organisms.

using-tomoauto-protocol-for-high-throughput-automated-cryo-electron

Research

JoVE Journal

Bioengineering

Polymer Microarrays for High Throughput Discovery of Biomaterials

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a combinatorial library of materials to be screened in a parallel, high throughput format1. Herein is described the formation and characterization of a polymer microarray using an on-chip photopolymerization technique 2. This involves mixing monomers at varied ratios to produce a library of monomer solutions, transferring the solution to a glass slide format using a robotic printing device and curing with UV irradiation. This format is readily amenable to many biological assays, including stem cell attachment and proliferation, cell sorting and low bacterial adhesion, allowing the ready identification of 'hit' materials that fulfill a specific biological criterion3-5. Furthermore, the use of high throughput surface characterization (HTSC) allows the biological performance to be correlated with physio-chemical properties, hence elucidating the biological-material interaction6. HTSC makes use of water contact angle (WCA) measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In particular, ToF-SIMS provides a chemically rich analysis of the sample that can be used to correlate the cell response with a molecular moiety. In some cases, the biological performance can be predicted from the ToF-SIMS spectra, demonstrating the chemical dependence of a biological-material interaction, and informing the development of hit materials5,3.

A description of the formation of a polymer microarray using an on-chip photopolymerization technique. The high throughput surface characterization using atomic force microscopy, water contact angle measurements, X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry and a cell attachment assay is also described.

The discovery of novel biomaterials that are optimized for a specific biological application is readily achieved using polymer microarrays, which allows a ...

High-throughput Protein Expression Generator Using a Microfluidic Platform

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and high-fidelity measurements of large systems. Microfluidics promises to fulfill many of these requirements, such as performing high-throughput screening experiments on-chip, encompassing biochemical, biophysical, and cell-based assays1. Since the early days of microfluidics devices, this field has drastically evolved, leading to the development of microfluidic large-scale integration2,3. This technology allows for the integration of thousands of micromechanical valves on a single device with a postage-sized footprint (Figure 1). We have developed a high-throughput microfluidic platform for generating in vitro expression of protein arrays (Figure 2) named PING (Protein Interaction Network Generator). These arrays can serve as a template for many experiments such as protein-protein 4, protein-RNA5 or protein-DNA6 interactions.
The device consist of thousands of reaction chambers, which are individually programmed using a microarrayer. Aligning of these printed microarrays to microfluidics devices programs each chamber with a single spot eliminating potential contamination or cross-reactivity Moreover, generating microarrays using standard microarray spotting techniques is also very modular, allowing for the arraying of proteins7, DNA8, small molecules, and even colloidal suspensions. The potential impact of microfluidics on biological sciences is significant. A number of microfluidics based assays have already provided novel insights into the structure and function of biological systems, and the field of microfluidics will continue to impact biology.

We present a microfluidic approach for the expression of protein arrays. The device consists of thousands of reaction chambers controlled by micro-mechanical valves. The microfluidic device is mated to a microarray-printed gene library. These genes are then transcribed and translated on-chip, resulting in a protein array ready for experimental use.

Rapidly increasing fields, such as systems biology, require the development and implementation of new technologies, enabling high-throughput and ...

High-throughput, Automated Extraction of DNA and RNA from Clinical Samples using TruTip Technology on Common Liquid Handling Robots

TruTip is a simple nucleic acid extraction technology whereby a porous, monolithic binding matrix is inserted into a pipette tip. The geometry of the monolith can be adapted for specific pipette tips ranging in volume from 1.0 to 5.0 ml. The large porosity of the monolith enables viscous or complex samples to readily pass through it with minimal fluidic backpressure. Bi-directional flow maximizes residence time between the monolith and sample, and enables large sample volumes to be processed within a single TruTip. The fundamental steps, irrespective of sample volume or TruTip geometry, include cell lysis, nucleic acid binding to the inner pores of the TruTip monolith, washing away unbound sample components and lysis buffers, and eluting purified and concentrated nucleic acids into an appropriate buffer. The attributes and adaptability of TruTip are demonstrated in three automated clinical sample processing protocols using an Eppendorf epMotion 5070, Hamilton STAR and STARplus liquid handling robots, including RNA isolation from nasopharyngeal aspirate, genomic DNA isolation from whole blood, and fetal DNA extraction and enrichment from large volumes of maternal plasma (respectively).

TruTip is a simple nucleic acid extraction technology whereby a porous, monolithic binding matrix is inserted into a pipette tip. Consequently, the sample preparation format is compatible with most liquid handling instruments, and can be used for many medium to high-throughput clinical applications and sample types.

TruTip is a simple nucleic acid extraction  technology whereby a porous, monolithic binding matrix is inserted into a  pipette tip. The geometry of the ...

A Microfluidic Platform for High-throughput Single-cell Isolation and Culture

Studying the heterogeneity of single cells is crucial for many biological questions, but is technically difficult. Thus, there is a need for a simple, yet high-throughput, method to perform single-cell culture experiments. Here, we report a microfluidic chip-based strategy for high-efficiency single-cell isolation (~77%) and demonstrate its capability of performing long-term single-cell culture (up to 7 d) and cellular heterogeneity analysis using clonogenic assay. These applications were demonstrated with KT98 mouse neural stem cells, and A549 and MDA-MB-435 human cancer cells. High single-cell isolation efficiency and long-term culture capability are achieved by using different sizes of microwells on the top and bottom of the microfluidic channel. The small microwell array is designed for precisely isolating single-cells, and the large microwell array is used for single-cell clonal culture in the microfluidic chip. This microfluidic platform constitutes an attractive approach for single-cell culture applications, due to its flexibility of adjustable cell culture spaces for different culture strategies, without decreasing isolation efficiency.

Here, we present a protocol for isolating and culturing single cells with a microfluidic platform, which utilizes a new microwell design concept to allow for high-efficiency single cell isolation and long-term clonal culture.

Studying the heterogeneity of single cells is crucial for many biological questions, but is technically difficult. Thus, there is a need for a simple, yet ...

Automated Lipid Bilayer Membrane Formation Using a Polydimethylsiloxane Thin Film

An artificial lipid bilayer, or black lipid membrane (BLM), is a powerful tool for studying ion channels and protein interactions, as well as for biosensor applications. However, conventional BLM formation techniques have several drawbacks and they often require specific expertise and laborious processes. In particular, conventional BLMs suffer from low formation success rates and inconsistent membrane formation time. Here, we demonstrate a storable and transportable BLM formation system with controlled thinning-out time and enhanced BLM formation rate by replacing conventionally used films (polytetrafluoroethylene, polyoxymethylene, polystyrene) to polydimethylsiloxane (PDMS). In this experiment, a porous-structured polymer such as PDMS thin film is used. In addition, as opposed to conventionally used solvents with low viscosity, the use of squalene permitted a controlled thinning-out time via slow solvent absorption by PDMS, prolonging membrane lifetime. In addition, by using a mixture of squalene and hexadecane, the freezing point of the lipid solution was increased (~16 &#176;C), in addition, membrane precursors were produced that can be indefinitely stored and readily transported. These membrane precursors have reduced BLM formation time of &#60; 1 hr and achieved a BLM formation rate of ~80%. Moreover, ion channel experiments with gramicidin A demonstrated the feasibility of the membrane system.

We demonstrate a storable, transportable lipid bilayer formation system. A lipid bilayer membrane can be formed within 1 hr with over 80% success rate when a frozen membrane precursor is brought to ambient temperature. This system will reduce laborious processes and expertise associated with ion channels.

An artificial lipid bilayer, or black lipid membrane (BLM), is a powerful tool for studying ion channels and protein interactions, as well as for ...

High-throughput Identification of Bacteria Repellent Polymers for Medical Devices

Medical devices are often associated with hospital-acquired infections, which place enormous strain on patients and the healthcare system as well as contributing to antimicrobial resistance. One possible avenue for the reduction of device-associated infections is the identification of bacteria-repellent polymer coatings for these devices, which would prevent bacterial binding at the initial attachment step. A method for the identification of such repellent polymers, based on the parallel screening of hundreds of polymers using a microarray, is described here. This high-throughput method resulted in the identification of a range of promising polymers that resisted binding of various clinically relevant bacterial species individually and also as multi-species communities. One polymer, PA13 (poly(methylmethacrylate-co-dimethylacrylamide)), demonstrated significant reduction in attachment of a number of hospital isolates when coated onto two commercially available central venous catheters. The method described could be applied to identify polymers for a wide range of applications in which modification of bacterial attachment is important.

A high-throughput microarray method for the identification of polymers which reduce bacterial surface binding on medical devices is described.

Medical devices are often associated with hospital-acquired infections, which place enormous strain on patients and the healthcare system as well as ...

Generic Protocol for Optimization of Heterologous Protein Production Using Automated Microbioreactor Technology

A core business in industrial biotechnology using microbial production cell factories is the iterative process of strain engineering and optimization of bioprocess conditions. One important aspect is the improvement of cultivation medium to provide an optimal environment for microbial formation of the product of interest. It is well accepted that the media composition can dramatically influence overall bioprocess performance. Nutrition medium optimization is known to improve recombinant protein production with microbial systems and thus, this is a rewarding step in bioprocess development. However, very often standard media recipes are taken from literature, since tailor-made design of the cultivation medium is a tedious task that demands microbioreactor technology for sufficient cultivation throughput, fast product analytics, as well as support by lab robotics to enable reliability in liquid handling steps. Furthermore, advanced mathematical methods are required for rationally analyzing measurement data and efficiently designing parallel experiments such as to achieve optimal information content.
The generic nature of the presented protocol allows for easy adaption to different lab equipment, other expression hosts, and target proteins of interest, as well as further bioprocess parameters. Moreover, other optimization objectives like protein production rate, specific yield, or product quality can be chosen to fit the scope of other optimization studies. The applied Kriging Toolbox (KriKit) is a general tool for Design of Experiments (DOE) that contributes to improved holistic bioprocess optimization. It also supports multi-objective optimization which can be important in optimizing both upstream and downstream processes.

This manuscript describes a generic approach for tailor-made design of microbial cultivation media. This is enabled by an iterative workflow combining Kriging-based experimental design and microbioreactor technology for sufficient cultivation throughput, which is supported by lab robotics to increase reliability and speed in liquid handling media preparation.

A core business in industrial biotechnology using microbial production cell factories is the iterative process of strain engineering and optimization of ...

Use of High-Throughput Automated Microbioreactor System for Production of Model IgG1 in CHO Cells

Automated microscale bioreactors (15 mL) can be a useful tool for cell culture engineers. They facilitate the simultaneous execution of a wide variety of experimental conditions while minimizing potential process variability. Applications of this approach include: clone screening, temperature and pH shifts,&#160;media and supplement optimization. Furthermore, the small reactor volumes are conducive to large Design of Experiments that investigate a wide range of conditions. This allows upstream processes to be significantly optimized before scale-up where experimentation is more limited in scope due to time and economic constraints. Automated microscale bioreactor systems offer various advantages over traditional small scale cell culture units, such as shake flasks or spinner flasks. However, during pilot scale process development&#160;significant care must be taken to ensure that these advantages are realized. When run with care, the system can enable high level automation, can be programmed to run DOE&#39;s with a higher number of variables&#160;and can reduce sampling time when integrated with a nutrient analyzer or cell counter. Integration of the expert-derived heuristics presented here, with current automated microscale bioreactor experiments can minimize common pitfalls that hinder meaningful results. In the extreme, failure to adhere to the principles laid out here can lead to equipment damage that requires expensive repairs. Furthermore, the microbioreactor systems have small culture volumes&#160;making characterization of cell culture conditions difficult. The number and amount of samples taken in-process in batch mode culture is limited as operating volumes cannot fall below 10 mL. This method will discuss the benefits and drawbacks of microscale bioreactor systems.

A detailed protocol for the concurrent operation of 48 parallel cell cultures under varied conditions in a microbioreactor system is presented. Cell culture process, harvest and subsequent antibody titer analysis are described.

Automated microscale bioreactors (15 mL) can be a useful tool for cell culture engineers. They facilitate the simultaneous execution of a wide variety of ...

Process Optimization using High Throughput Automated Micro-Bioreactors in Chinese Hamster Ovary Cell Cultivation

Optimization of bioprocesses to increase the yield of desired products is of importance in the biopharmaceutical industry. This can be achieved by strain selection and by developing bioprocess parameters. Shake flasks have been used for this purpose. They, however, lack the capability to control the process parameters such as pH and dissolved oxygen (DO). This limitation can be overcome with the help of an automated micro-bioreactor. These bioreactors mimic cultivation at a larger scale. One of the major advantages of this system is the integration of the Design of Experiment (DOE) in the software. This integration enables establishing a design where multiple process parameters can be varied simultaneously. The critical process parameters and optimum bioprocess conditions can be analyzed within the software. The focus of the work presented here is to introduce the user to the steps involved in process design in the software and incorporation of the DOE within the cultivation run.

Here, we present a detailed procedure to run a Design of Experiment in an automated micro-bioreactor followed by cell harvest and protein quantification using a Protein A column.

Optimization of bioprocesses to increase the yield of desired products is of importance in the biopharmaceutical industry. This can be achieved by strain ...

High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay

Tomato is an agronomically important crop that can be infected by Pseudomonas syringae, a Gram-negative bacterium, resulting in bacterial speck disease. The tomato-P. syringae pv. tomato pathosystem is widely used to dissect the genetic basis of plant innate responses and disease resistance. While disease was successfully managed for many decades through the introduction of the Pto/Prf gene cluster from Solanum pimpinellifolium into cultivated tomato, race 1 strains of P. syringae have evolved to overcome resistance conferred by the Pto/Prf gene cluster and occur worldwide.
Wild tomato species are important reservoirs of natural diversity in pathogen recognition, because they evolved in diverse environments with different pathogen pressures. In typical screens for disease resistance in wild tomato, adult plants are used, which can limit the number of plants that can be screened due to their extended growth time and greater growth space requirements. We developed a method to screen 10-day-old tomato seedlings for resistance, which minimizes plant growth time and growth chamber space, allows a rapid turnover of plants, and allows large sample sizes to be tested. Seedling outcomes of survival or death can be treated as discrete phenotypes or on a resistance scale defined by amount of new growth in surviving seedlings after flooding. This method has been optimized to screen 10-day-old tomato seedlings for resistance to two P. syringae strains and can easily be adapted to other P. syringae strains.

High-Throughput Identification of Resistance to Pseudomonas syringae pv. Tomato in Tomato using Seedling Flood Assay

The seedling flood assay facilitates rapid screening of wild tomato accessions for the resistance to the Pseudomonas syringae bacterium. This assay, used in conjunction with the seedling bacterial growth assay, can assist in further characterizing the underlying resistance to the bacterium, and can be used to screen mapping populations to determine the genetic basis of resistance.

Tomato is an agronomically important crop that can be infected by Pseudomonas syringae, a Gram-negative bacterium, resulting in bacterial speck disease. ...