Vigilant management of maintenance and downtime in automated platforms is an important part of a successful implementation
Sean Keating
Managing Editor 

Often, when there is an explosion in demand, technology rushes in to fill the supply. So it is with the increased use of cell-based assays in high-throughput screening (HTS). A number of pharmaceutical companies, many running 50% or more of their HTS assays as cell-based, have invested in cell culture automation systems and are running them around the clock. But reliance on the output of such systems goes hand-in-hand with careful management of their maintenance.

SelecT was designed by TAP with a consortium of six major pharmaceutical companies: GlaxoSmithKline, Merck, Pfizer, Bristol-Myers Squibb, AstraZeneca, and Parke-Davis (now Pfizer). (Source: The Automation Partnership)

Cell culture automation systems can be found in the fermentation labs of the expression and fermentation technologies group, Pfizer Global Research and Development, Groton, Conn. Kim Stutzman-Engwall, PhD, associate research fellow and project coordinator, says the group supplies mammalian, bacterial, and insect cells for isolating proteins on a large scale. "A lot of the cells and cell lines that we provide are producing proteins that are used in either high-throughput screening assays, or they're used in primary or secondary assays by different therapeutic area discovery teams."

Within Pfizer as a whole, Stutzman-Engwall estimates 50% of assays are either whole-cell or cell-fraction-based. "I don't see [the percentage of cell-based assays] growing dramatically, but since the automation allows us to produce larger numbers of plates for assays and more cells, it's probably going to go up."

The Pfizer group uses the Cellmate and SelecT systems from The Automation Partnership Ltd., Royston, UK. "[Cellmate] is primarily used for making large volumes of cells for non-whole-cell-based assays." Cells are grown in roller bottles and the instrument functions as a harvester, removing cells either enzymatically or by physically scraping them out to form a concentration of cell fractions. The system has been in use at Pfizer for more than five years.

For whole cells, the group uses SelecT, which allows them to maintain cultures of a number of different cell lines. The instrument "automatically transfers those cells, counts them, measures their viabilities, and at the appropriate time that you've programmed into the machine, will plate them, even into 96-well or 384-well plates," she says. SelecT was designed by TAP with a consortium of major pharmaceutical companies which included Pfizer, and the system has been in use at Pfizer for approximately three years.

A net positive
Early on, as with all technologies in their infancy, the SelecT system needed a lot of tweaking to get it to work correctly, says Stutzman-Engwall. "When it was first set up here, we had technicians from TAP that, essentially, lived here for the summer, trying to get the machine to work as it was supposed to."

Although the research group overall is very satisfied with the system, Stutzman-Engwall pointed out that SelecT eliminated one time-consuming task but created another. "You free up people's time from sitting in a hood and doing that work manually. But, you also increase people's time in actually programming the equipment," she says, adding that this can be a complicated step. In total, however, the system does result in a net savings in effort, just not quite as much as Stutzman-Engwall and the group had originally anticipated.

Maintenance and downtime
A significant part of the output Stutzman-Engwall's group relies on its automated cell culturing systems, so maintenance needs to be well planned. "We do have teams that are used to having their 15 plates twice a week, or ten plates every other Monday. And so, when we know that's its going to be coming down for maintenance, we give them plenty of warning so that they're aware that the plates will not be coming." Occasionally, depending on what assays are running or the particular cell line, the group will take over the job manually. But neither the SelecT nor the Cellmate is mirrored by a back-up unit at Pfizer.

“I think that TAP understands the issues that we had in the beginning [with the SelecT], and that they’ve worked to resolve them . . . I think that there were growing pains there for both sides.” - Angela Cacace, PhD, Bristol-Myers Squibb

Depending on exactly what goes wrong with the systems, actually fixing them can either fall to people at Pfizer or TAP. "We've had people here that have been trained by TAP to do some of the very basic types of things. Anything that's serious, there will be someone from TAP that comes over to take care of it. But by and large, the majority of things are taken care of in house."

While not a barrier to cell culture automation systems, downtime remains a challenge that needs to be worked around in other companies as well. The group that Angela Cacace, PhD, senior research investigator II, lead discovery and profiling with Bristol-Myers Squibb (BMS), works in currently maintains 180 cell lines and services the whole of BMS's Pharmaceutical Research Institute. Like their counterparts at Pfizer, the group uses both TAP's SelecT and Cellmate without redundant backups (for specifics on BMS's implementation, see Lab Masters Learning Curve in Cell Culture Automation in the August 2004 Drug Discovery & Development).

"If you have a plating failure [on the SelecT], it can be kind of drastic because that means [for example] that people who report data to chemistry every week, their assays are now stopped. So these malfunctions aren't trivial," she says. Her group's backup strategy involves maintaining extra flasks on the SelecT system that can be pulled off if plating fails. Also, plating is generally done on Sunday and Monday, allowing time for recovery during the week in the event of a failure.

Becoming more robust
Back in 2003, Cacace's group was hesitant to enable Sunday operation of the SelecT because, at the time, the instrument tended to fail if unattended. "But now we're very comfortable. It's become more robust in our hands, maybe because we understand it a bit better than we did back in 2003. So we do run on Sundays."

Cacace credits this change to the learning curve of both her group and TAP. "I think that TAP understands the issues that we had in the beginning, and that they've worked to resolve them." This includes improvements to the software and a better understanding of how to control, maintain, and fix pieces of equipment peripheral to the system. "I think that there were growing pains there for both sides."

Gary Allenby, PhD, associate principal scientist with the hit identification group within the lead generation unit of AstraZeneca Plc., Loughborough, UK, works primarily on respiratory and inflammatory diseases. His group uses the acCellerator cell culturing system from RTS Life Science International, Manchester, UK, in the development of cell-based assays that they themselves screen (for specifics on AstraZeneca's implementation, see the story in the August 2004 issue mentioned above). "We do approximately 15 screens per annum. Each of those is about a million wells in 384-well format. And it's steadily on the increase, but now it's about 70% cell based," he says.

For its system, Allenby's group manages downtime via maintenance regimes. "There are certain parts of the system where the mean time between failure is greater than other parts of the system. But we generally have a failure about every week. Probably about eight times out of 10, those failures are the consequence of human error." Dealing with this level of failure, however, is not too much of a challenge, he says.

Allenby's group also recently added a failure notification system to their setup. "It's able to page a mobile phone to say 'There's a problem, come and fix me!' " he says. "There's never a point where it is 100% reliable, and so you live with that paranoia. People were actually going in on a Saturday or a Sunday, not necessarily to do anything to the system, but just to make sure that it was working properly." With the notification system, however, "it relieves that stress in the night, because they know if the system does stop it will let them know."