Automating High-Throughput Screening

To automate today’s high-throughout screening (HTS), researchers need a combination of hardware and software. As always, robotic arms and liquid-handling systems bring improvements to these processes, but keeping such complicated workflows efficient requires software tools that track the processes and samples. In addition, some companies make modular systems that let users expand the automation of a system over time.

In most cases, a system for HTS consists of many pieces. “To automate this,” says Matt Kirtley, product manager at Agilent (Santa Clara, Calif.), “there’s a bit of a shift toward a much more modular fashion.” That arises from some researchers seeking more flexible systems. “Many people want to invest in a tool that can be repurposed for multiple projects,” Kirtley says.

Agilent recently released such a tool, the Encore Multispan liquid handling system, which consists of an advanced liquid handler and high-level plate management. As Kirtley says, “The onboard robotic arm facilitates large automated workflows.” When using this platform to automate HTS, Kirtley points out, it really takes advantage of everything behind this system.

The Encore system includes a pipetting system that operates in two dimensions across the deck. This two-dimensional feature speeds up operations in general. “You get two-fold better throughout in comparison to one-dimensional pipetting systems,” Kirtley notes.

In many cases, pharmaceutical scientists perform primary screening in plates and then reformat them for a secondary screen of the best hits. “That requires liquid handling steps that have been the biggest bottleneck,” says Kirtley. For example, a scientist might screen a number of antibodies in search of one that binds best to a particular antigen. “The Encore can put all of the candidates on the deck and run an initial binding assessment,” Kirtley says. “It takes the plate-reader results, sets a threshold for the response, and then the system reformats the best of the hits into a new plate and runs a secondary assessment for more thorough binding data.” So the user just places the first plate on the deck and returns to get the results of the best candidates, as determined by the primary and secondary screens.

Working with the workflow
“It doesn’t make sense to collect one-thousand samples in a day if you can’t analyze that,” says Keeley Murphy, marketing specialist for the pharmaceutical and biopharmaceutical segments at Thermo Fisher Scientific (Waltham, Mass.). “So, we offer a complete workflow to collect, process, and manage the data.”

The Transcend System from Thermo Fisher Scientific provides new capabilities in data generation and collection. “It provides automated online sample preparation with the ability to connect up to four parallel liquid chromatography [LC] systems to one mass spectrometer [MS],” Murphy explains. It also provides dynamic load wash, which simultaneously cleans the injection needle and port. “That’s how we get the cycle time down to below 20 seconds per sample,” Murphy says. This system runs samples that fast while still allowing for high-performance liquid chromatography (HPLC) and even ultra HPLC.

At first, says Murphy, early discovery labs used the Transcend System the most. “But,” he adds, “we’ve been seeing customers even using these systems for lead finding.” In fact, some users get four samples per minute from this system, which lets them apply LC/MS to screens containing hundreds of thousands of compounds. “With LC/MS,” says Murphy, “you get higher quality data, because you don’t use the labels needed in plate assays.”

This system can even tie into Thermo Fisher Scientific’s Orbitrap MS technology. “Then, an untargeted or full scan analysis can be performed allowing for all components of the screening assay to be monitored simultaneously,” Murphy says. “With this approach you can better understand unexpected results as well as go back and mine the data if needed instead of having to rerun the analysis.”

Creating more consistency
Whenever possible, today’s drug researchers would rather work with cell cultures than animal models, says Keith Roby, North America operations senior tactical marketing manager for automation at Beckman Coulter Life Sciences (Brea, Calif.). “So they’re growing up cell cultures in large enough volume for high-throughput screening,” he says.

click to enlarge The Plate Auditor from Brooks Automation provides quality control during screening.

To help drug researchers automate the screening of such cells in high-throughput ways, Beckman Coulter developed the BioRAPTR FRD workstation, which works with 96-, 384-, 1536-, and 3456-well plates. Moreover, it dispenses volumes that range from 100 nL to 60 µL without cross contamination. “By using fluidic lines,” says Roby, “the BioRAPTR takes tips out of the equation.”

By using plates with more wells, researchers decrease the variability between samples. “If you grow up enough cells for a 96-well plate and then grow up more cells to test the next day,” Roby says, “your cells could be affected by different growth conditions on the second day, which adds variability to the results.” He adds, “The more experiments you can do with the same reagents and cells in one plate, the more reproducible and robust the results will be.”

This system dispenses the cells with a high-speed solenoid that doesn’t heat them up, which means the cells remain viable during the dispensing cycle. Also, the vertical tubing prohibits cells from settling while in the tubing, making the system easy to clean, so there’s less chance of leaving contaminants inside the tubes that could hurt the cells.

“The system has the option of using a 4- or 8-channel dispense head with independent reagent bottles for each channel,” Roby explains. “You can even deconvolute experimental results and export them to standard file formats for importing into [design of experiments] software for analysis.”

Success of cells
Beyond using cells over animals whenever possible, some drug researchers also use cells instead of traditional biochemical screens. “More customers are looking to cellular screening and the library is smaller and more focused,” says Andreas Niewoehner, product manager, automated systems at PerkinElmer (Waltham, Mass.), “although some niche markets still focus on traditional biochemical screening.”

The cellular transition lies behind PerkinElmer’s creation of the cell::explorer, which automates high-content and cellular screening assays. “This platform,” says Niewoehner, “provides incubation through liquid handling to detection technology in one workstation.”

The image-detection in cell::explorer comes from PerkinElmer’s Opera or Operetta platforms. The conventional multimode detection comes from the company’s EnVision or EnSpire readers. “This is not a fixed workstation,” says Niewoehner, “so we can customize it for specific needs, such as different levels of throughput.” For example, the cell::explorer works with 384- or 1536-well plates.

In addition, PerkinElmer’s plate::works software controls the cell::explorer. As Niewoehner explains, “This software was developed for high-throughput screening, and it is event-driven, which guarantees the highest possible throughput because it processes the next step whenever possible.” This software also includes added functions for cell-specific assays. For example, since cell-based assays often run much longer than biochemical ones, researchers need more flexibility, such as the ability to run assays in parallel or take an automated process offline to do some manual work. The plate::works software provides these capabilities and more.

A software solution

click to enlarge The Encore Multispan System from Agilent includes a built-in robotic arm that provides a span of up to 21 inches off-deck with patented one-touch easy teaching that enables end-to-end workflow integrations.

Automating HTS requires sophisticated control. To handle that, Brooks Automation (Poway, Calif.) developed its Sprint 6 scheduling solution. “Sprint 6 is a dynamic scheduler designed for HTS,” says Simon Sheard, the company’s product manager. “It can be supplied with Brooks hardware or as a standalone software solution for retrofit to third-party platforms.”

In creating this software, Brooks focused on control and flexibility. “Our clients want systems that are flexible and make best use of time and resources,” says Sheard. “Schedule logic, loops, and other advanced scheduling functionalities provided by Sprint 6 allow this.” For example, Sheard explains, “Operators may wish to use instruments offline during a run, and just-in-time instrument initialization allows this even when those instruments are required by the assay.” Assuming that the instruments are released back to the system when they are needed, Sprint 6 ensures that the assay is unaffected by instrument absences at other times.

Although designed for HTS, Sprint 6 is suitable for many applications and can be deployed on simple work cells, such as a robotic arm and a couple instruments, or multi-robot systems with many instruments. Regardless of application, Sprint 6 is easy to use. “It requires little technical knowledge by the user,” Sheard says. “Intelligent drag-and-drop interfaces make platform and schedule creation easy without sacrificing control and advanced users can always drill down to finer levels of control if required.”

For quality control during screening, researchers can use the Brooks Plate Auditor. This vision-based system quickly analyses plates to identify empty or partially filled wells and colored or precipitated samples. “The information provided helps avoid false negatives, saves money, and allows informed decisions,” Sheard says.

Determining the precise performance of any compound or cell being examined makes up the heart of HTS. Nonetheless, this field evolves at a fast pace. By automating the steps, and keeping up with changes, drug researchers explore more options, which will ultimately unveil tomorrow’s high-powered treatments.

About the Author
Mike May is a publishing consultant for science and technology based in Houston, Texas.

SOURCE:http://www.dddmag.com/articles/2013/02/automating-high-throughput-screening