SEATTLE – In a bid to further move high-content screening into high-throughput, primary screening applications, TTP Labtech launched the second generation of its Acumen Explorer high-content screening system at the Society for Biomolecular Sciences annual meeting held here this week.
TTP believes that the instrument, which uses three laser excitation and photomultiplier tube-based detection, will significantly increase the throughput of the types of high-content cell-based assays traditionally run on CCD-based imaging platforms, company executives told CBA News at the conference.
Still, TTP maintains that the platform is meant to complement such readers, and as such, is in heavy discussions with various vendors of these instruments about designing a platform that would integrate the two instruments. In addition, the company hopes to collaborate with cell-based assay reagent vendors to develop next-generation dyes and labels that will maximize the multiplexing capability of the new instrument, the executives said.
“The market is moving toward us, and that’s been very important over the past two years,” Jas Sanghera, TTP Labtech’s commercial director, told CBA News. “People generally want high throughput combined with high content.
“In addition, we will always have a bridge to the imaging systems,” Sanghera added. “Our systems already connect to a microscope, and that’s another area we’re going to expand. But we don’t see ourselves in direct competition with imaging systems – people who have imaging systems will actually have an advantage in buying our technology because they can link the two together.”
Wayne Bowen, TTP Labtech’s chief scientific officer, added that “we think very shortly they will be physically linked together. We see them as complementary, and actually we’ve thought about integrating them for many years.”
The new platform, called the Acumen eX3, can be equipped with up to three laser lines – 405 nm, 488 nm, and 633 nm – an improvement over its predecessor, the Acumen Explorer, which accommodated only one laser line, either the 405 nm or 488 nm.
According to Bowen, the new array of laser lines greatly expands the number of assays that can be performed on the Acumen.
“One of the issues we’ve had in the past is that the instrument has four data collection channels, but it’s been difficult to find four fluorescent reporters that you could excite with the single laser line that we fitted,” Bowen said. “That basically limited the number of assays in which you could use all four channels.
“Adding more lasers now allows people to access a broader selection of reagents – dyes, antibody conjugates, and the range of fluorescent proteins,” Bowen added. “Really one of the drivers was to allow customers to select different lasers to fill up all four detection channels and run higher levels of multiplexing.”
As an example, Bowen said that TTP Labtech and some of its customers had in the past shown that an Acumen Explorer fitted with a 405-nm laser could improve the performance of Invitrogen’s β-lactamase-based GeneBLAzer assay as compared with bulk fluorescence readers.
“But people had committed heavily, for instance, in bulk fluorescence readers, and there wasn’t enough justification to buy an [Acumen] just for that assay,” Bowen said. “Now we have the 405 and 488 in the same instrument, so people can buy an instrument for the high-content capabilities, and then switch the other laser on and run some of these whole-cell assays like beta lactamase.”
Another possible benefit provided by the new instrument is its ability to more smoothly transition high-content cell-based assays from the development stage to the screening stage, Bowen said.
“People want to be able to move their assays from microscope-based CCD imagers into the screening environment,” he said. “Ideally, they want to do that without changing their protocol. And people usually have to use a nuclear dye to run those assays – either Hoechst or increasingly, Draq-5. We couldn’t see that with the 488 laser line.
“Now we can offer excitation wavelengths that are compatible with those dyes,” Bowen added. “People can take the very same assay plate off the CCD imager and put them on the Acumen eX3, and run them at much higher throughputs without any changes.”
TTP also believes that the multiplexing capabilities of the new instrument actually exceed the multiplexing options afforded by the current available stable of cellular labeling reagents – something the company touts as “future-proofing.”
As a result, the company is putting the onus on reagent companies to further expand the HCS field by designing new and improved cellular labeling technologies. TTP already has a collaboration in place with Cell Signaling Technology to develop “the next generation of antibody labels,” Bowen said, but the company is also actively exploring partnerships with other reagent vendors.
“Basically, by taking the technology to the developers of the antibodies, you almost ensure compatibility,” Bowen said. “There are a number of other companies we’re talking with to further develop the whole high-content area.
“The fact that we now have three lasers, and can put more in if demand requires it, means that the pressure is back on reagent companies,” he added. “The field has moved toward reagents, Invitrogen got on board, and we’ve now brought in the other lasers, and [Invitrogen] needs to respond.”
High Throughput, High Content
All of this translates into moving high-content cell-based assays into the primary screening territory of the drug-discovery pipeline. Following the advent and eventual acceptance of CCD-based high-content imaging in pharmaceutical labs, many researchers have desired to increase the speed of the platforms to combine multiplexed data with throughputs more reminiscent of biochemical screens.
But the fact remains that automated microscopy is inherently slow because of the time it takes for image acquisition. High-speed confocal systems, such as those offered by Evotec Technologies, GE Healthcare, and Molecular Devices, have attempted to push the envelope in this area, but still often suffer from bottlenecks in image acquisition or image and data analysis.
In contrast, the Acumen offers the object recognition capabilities of CCD imaging systems because it employs whole-well scanning techniques, but sports the fast read times of bulk fluorescence readers. In addition, the platform offers sub-cellular resolution of individual cells, but doesn’t acquire actual images, allowing for increased throughput and decreased data-analysis and storage bottlenecks.
The flip side of this is that because it doesn’t take actual images, it may not be as high-content as CCD-based microscopy platforms, which allow a user to return to individual pictures, pick out specific important sub-cellular features, and identify the cause of unexpected results or off-target drug effects.
But TTP has also tried to address this shortcoming with the new instrument – namely by rejiggering the analysis software to allow users to export raw data files as TIF images that are equivalent to those obtained with a 20X microscope objective.
Regardless, the company doesn’t expect to compete with CCD imagers in this area, and still sees Acumen as complementary to such platforms
“The idea is that, as we’ve been saying for many years, you get your high-throughput screen done on the Acumen eX3,” Bowen said. “You pick out which wells you’re interested in, basically get a yes-no answer, get rid of 99 percent of your compounds, and then select those wells, take those plates onto a CCD imager, and spend much more time interrogating those particular cells.”
TTP said that the Acumen upgrades did not significantly affect the cost of the platform. This is primarily because the cost of semiconductor lasers has recently decreased significantly, almost by 50 percent over the past three years, Sanghera said.
“The fact that we now have three lasers, and can put more in if demand requires it, means that the pressure is back on reagent companies. The field has moved toward reagents, Invitrogen got on board, and we’ve now brought in the other lasers, and [Invitrogen] needs to respond.”
“People talk about lasers now as plug and play, almost like you put a card in your PC,” Bowen said. “That’s how we’ve designed our machine.” This is an industry-wide trend, and Molecular Devices uttered a similar sentiment in January when it released its new ImageXpress Ultra confocal HCS system, which is also armed with multiple laser lines but at a significantly reduced cost from previous iterations.
According to TTP, a fully loaded three-laser instrument tops out at around $400,000, while an entry-level instrument, typically containing one laser, will retail in the $200,000 range. “As we go forward, the prices, if anything, should go down,” Sanghera added.
TTP has already sold “about a half-dozen” eX3 platforms to undisclosed pharmaceutical customers in the US, and “hopes to get about 10 total placements by the end of the year,” Sanghera said.
The company will discontinue its previous version of the instrument, the Acumen Explorer, of which there are about 40 placed at various pharmaceutical companies, academic institutions, and government labs. These instruments are not field-upgradeable, Sanghera said, but the company plans to offer upgrade paths to its current customers.
“The idea is that we’ve made improvements not only with three lasers, but also to get all the technology into one box,” Sanghera said. “It doesn’t mean it’s a fixed three-laser. You can have a one-laser option, but this will essentially become our base instrument.
“We’ve obviously thought about this very carefully, and there will be a number of different options depending on what the customer wants to do,” he added. “We will never leave people stranded. It sometimes happens, I think, where people bought instruments and they’re left stranded in terms of the service and support not being provided, or there is no upgrade path. We always make sure there is an upgrade path or even a swap-out of capabilities.”