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Sidebar: Selected Suppliers Of Tools For Cell Culture BIOREACTOR: Bellco Glass offers the E/Z Access Reactor for culturing mammalian, plant, and insect cells. Early in this century, 1912 Nobel Prize winner Alexis Carrel of the Rockefeller Institute for Medical Research was a leader in cell and tissue culture. Among his accomplishments, Carrel showed how to transfer and study colonies of animal cells. At the time, some cell culture researchers were exceedingly formal. In Carrel's lab, assistants even wore full-length rubber gowns and head coverings to keep experiments sterile. Things have changed. Today's labs are more casual places. Walk into a lab doing cell culture, and you're likely to find jean-clad graduate students joking around and humming along with a CD player perched atop a lab bench. Still, the basic ideas-and needs-driving cell culture haven't changed since Carrel's time. To grow cells in the lab, a scientist needs at least four things: an isolated cell or set of cells to study; a nutritional medium in which those cells can grow; a way to study and track growing cells; and a method for propagating those cells. But today's technology makes it much easier to keep samples sterile. Companies constantly refine and streamline the tools scientists use to accomplish these basic cell culture steps. For the first task --simply getting the cell to be studied -- researchers often must dissociate a cell from surrounding tissue. They do so by treating a tissue sample with an enzyme that breaks down the extracellular matrix outside cells. One commonly used enzyme is trypsin, a pancreatic protein. A number of companies sell trypsin. Intergen Co. of Purchase, N.Y., is a leading manufacturer of trypsin for cell culture. "We sell kilograms and kilograms of trypsin to the cell culture industry, in both solution and powder forms," says Michael O. Budnick, the company's associate director of technical services. In addition to initial cell isolation, researchers use trypsin to dissociate and count cells or change media, Budnick notes. As soon as researchers get their prized cells growing in culture, they typically freeze some for safekeeping. That way, they have a pure source of cells if current cultures become contaminated. THE BIG CHILL: PCG Scientifics offers NUNC Cryotube Vials to store cells at temperatures from -196°C and up. PGC Scientifics Corp. in Gaithersburg, Md., offers a range of NUNC Cryotube Vials and Greiner Sterile Cryo Vials to store cells at temperatures from -196°C and up. The vials come in self-standing varieties or fit inside polycarbonate cryoboxes. PGC also supplies aprons and gloves to protect researchers working with freezers or autoclaves. When it comes to cell culture, there's one thing every scientist constantly uses: media. Cells growing outside their natural tissue need a steady stream of nutrients. These needs change depending on the type of cell. Mammalian cells, for example, need a host of vitamins, amino acids, salts, and sugars. Because basal media like these are pretty standard, scientists often shop around for bargains. Take Rochelle Diamond, manager of an immunology lab at the California Institute of Technology. "We tend to buy the [medium] that's available at the best price," she explains. Her lab grows immune cells to study genes controlling cell development. Diamond says she has been happy with powder and liquid versions of cellgro media produced by Mediatech Inc. of Herndon, Va., and distributed through Fisher Scientific Inc. in Pittsburgh. Plant cells are more finicky than their animal counterparts, contends June Bourque, a plant pathology research associate at the University of Missouri. "Plant cells have to have a much more defined growth environment [than animal cells]," she says. "They are very picky about subtle changes. And they also must maintain a certain density." Plant cells require a medium that is rich in nitrogen and phosphorous, among other things. Bourque has used GIBCO BRL plant cell media exclusively for years. Life Technologies Inc. of Gaithersburg produces GIBCO BRL plant cell media. The company also offers component-deficient media for special cell growth conditions. For example, Life Technologies produces D-MEM, a medium lacking phenol red, which is a pH indicator that can exhibit estrogen-like activity in cells. Over the past decade, the biggest media trend has been toward serum-free alternatives. Traditionally, manufacturers have added animal serum-the nutrient-rich liquid part of blood-to media to help cells grow. But serum contains a hodgepodge of vaguely identified chemicals that add uncertainty to an experiment. In contrast, serum-free media is a "chemically defined" combination of core nutrients and growth proteins that a particular cell type needs (H. Ahern, The Scientist, April 1,1996, page 18). "Serum-free media continues to grow more and more popular," notes Michael Lamarque, president of Biomedical Technologies Inc. in Stoughton, Mass. A number of companies, including Biomedical Technologies, Life Technologies, and Wako BioProducts in Richmond, Va., provide serum-free media. ELISA ASSAY: Intergen's Cytokine Direct assay offers high sensitivity in the picogram range. The move toward these media opens a market for companies providing specific elements that cells once got from serum-for example, lipids or fats. "When you take away serum, some cells still need a source of lipids," Budnick says. Intergen offers a cell package of cholesterol and lipids. Many companies also sell individual proteins-such as growth factors-that, when added to serum-free media, help certain cells grow or express lots of protein. Scientists add these proteins to cell media during a variety of projects. For example, Biomedical Technologies sells 2.5S Nerve Growth Factor to scientists studying brain cells. BioSource International Inc. of Camarillo, Calif., also sells cytokines in bulk. In nature, cytokines stimulate immune system response to disease. In cell culture, these proteins can prompt a cell to differentiate, or mature from a basic cell type into its specialized form. BioSource offers a number of interleukin cytokines. Science occasionally precedes technology. At one time or another, many a researcher has flipped over a petri dish, struggled to squeeze it above a microscope stage, and then peered-hard-toward the light below. "It's just difficult to see clearly," according to David Prentice, a life science professor at Indiana State University. "And when you flip your dish over, things can get runny." The problem is that in the traditional microscope, the objectives are above the stage, while the light shines from below. In between, there is a small space perfect for a glass slide-but not a round dish, and certainly not a flask. That's why companies now offer "inverted microscopes," in which the objectives extend from beneath the stage and the light shines from above. VWR Scientific Products in West Chester, Pa., distributes two inverted scopes. Both offer an optional mechanical stage with special holders for petri dishes, microtiter or microtest plates, plastic flasks, and plankton chambers. The ID 03 Inverted Microscope, made by Carl Zeiss Inc. of Thornwood, N.Y., offers a built-in phase contrast system. The Televal 31 Inverted Microscope, also by Zeiss, adds a built-in camera port for easy photomicrographs. Applikon Inc. Bellco Glass Inc. Biomedical Technologies Inc. BioSource International Inc. Boehringer Mannheim Inc. Cole-Parmer Instrument Co Fisher Scientific Inc. Intergen Co. Life Technologies Inc. Mediatech Inc. PGC Scientifics Corp. Promega Corp Synthecon Inc. VWR Scientific Products Wako BioProducts Carl Zeiss Inc. Of course, you can't fully analyze cells in culture by just staring at them through a scope. To track cell proliferation, researchers typically perform an assay. Promega Corp. of Madison, Wis., recently announced the CellTiter 96 AQueous One Solution Cell Proliferation Assay. An updated version of an existing Promega assay, the CellTiter 96 is a one-step color reaction that doesn't use any radioactive agents. "That's a benefit for a lot of researchers who want to limit their radiation exposure," explains Pam Guthmiller, a marketing representative at Promega. She says CellTiter 96 also is particularly convenient because -- unlike most cell proliferation assays -- it doesn't require a researcher to prepare reagents. "This is ready to go as is," Guthmiller says. "So it cuts down on time as well." Intergen and Boehringer Mannheim Inc. of Indianapolis also offer ELISA assays. Boehringer's assays can assess cell death within populations of cells or track death in single cells by measuring DNA fragmentation or plasma membrane permeability. Intergen's Cytokine Direct is a "sandwich" enzyme immunoassay that measures natural and recombinant forms of a particular cytokine in cell culture and other biological matrices. The company recommends it for cell culture assays requiring high sensitivity in the picogram range. The drive to save time inspired the new 0-15 Liter Fermentation System, made by Applikon Inc. of Foster City, Calif., and distributed by Cole-Parmer Instrument Co. in Vernon Hills, Ill. Assembling a fermentation system can be as complicated-and frustrating-as installing a new computer. "Until now, our customers have had to buy pieces of a fermentation system and put them together themselves," notes John Wilson, a product group manager of analytical instruments at Cole-Parmer. "It's a hassle." But Wilson says the company's all-in-one fermentation system makes growing cells easy. The system includes an impeller, filters, module cabinet, pump system, and controllers for pH, oxygen, and temperature. "It's everything they need to get started," Wilson says. According to the company, the system will benefit biotech researchers making vaccine cultures, food companies working on enzyme technology, and others. It can be scaled up for large projects. MICROGRAVITY-BASED: Synthecon's Rotary Cell Culture System allows cells to grow into tissues. Growing cells on a large scale is vital if you're testing potential drugs. In large labs, scientists often raise cells in bioreactors. Bellco Glass Inc. of Vineland, N.J., sells the E/Z Access Reactor for culturing mammalian, plant, and insect cells, as well as bacterial fermentation. Synthecon Inc. of Houston offers the Rotary Cell Culture System, a unique, microgravity-based bioreactor that allows cells to grow into tissues. If Carrel got a little carried away 80 years ago, he did have the right idea: In culturing cells, sterility is essential. Any bit of contamination can affect the way a cell grows-or if it grows at all. The classic piece of equipment in a sterile environment is the hood, a cabinet that vents air away from the work area. PGC Scientifics offers a range of hoods, depending on the user's requirements. One popular product is the Vertical Laminar Flow Hood, which has an automatic filter monitoring system. This hood comes in a variety of styles, with a stainless-steel or laminated bench that can be adjusted to different heights. For scientists who don't like to clutter their workspace with pipettes and flasks, PGC also offers the Hood Organizer, a self-standing steel shelf. When it comes to sterility, every little bit counts. The tops of flasks, for example, are a prime invasion spot for microbes. It doesn't help when scientists simply cover a flask with a patch of tin foil, either. Foil is far from sterile, and it leaves gaps of air in which microbes can enter. But rubber stoppers-the classic air-tight plug for flasks-can get annoyingly jammed, like a wine cork that won't come loose. What's a researcher to do? Bourque at the University of Missouri reaches for Bellco's Silicone Sponge Plug Closures. She spotted the spongy pink plugs in someone s lab years ago, and she has used them ever since. "They're more convenient than a rubber stopper and less contaminating than aluminum foil," Bourque says. "These stoppers are soft, pliable, and reusable." While cell contamination is a serious issue, Bourque acknowledges that she likes the Bellco plugs mostly because they're easy to use. "It's really a comfort benefit," she says. When one considers the painstaking nature of cell culture, a little comfort is well deserved. Kathryn S. Brown is a freelance science writer based in Columbia, Mo.

Easy-To-Use Tools Are On Cell Culture Researchers' Holiday Wish List

Dec 8, 1996

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