BioSource International and Whatman Schleicher & Schuell are set to launch the first commercially available planar phosphoarray later this year, the companies said last week.
The array, called the Mercatur Phosphoarray, contains 10 analytes — each specific for a different phosphosite. The decision to make the new array grew out of customers’ demand for a product that could analyze multiple phosphosites at the same time, said Chris Brotski, senior product manager for Camarillo, Calif.-based BioSource International.
“We were making single phosphosite-specific ELISA kits and a lot of customers said it would be useful to be able to look at several phosphorylations at the same time,” said Brotski. “That’s when we decided to collaborate with [Whatman] Schleicher & Schuell, who have the FAST technology for spotting.”
The new phosphoarray will cost $295 for a single slide, or $995 for four slides. The arrays expire in one year and are guaranteed to last that long.
The 10 analytes were chosen after numerous meetings with marketing and business-development representatives at both companies, said Brotski. The current array contains a panel of phosphoanalytes that range from receptors on the membrane, to kinases in the cytoplasm, to some transcription factors.
“We had help from market research to target what’s most popular,” said Brotski. “This array represents a complete pathway.”
Robert Negm, the director of business development for Whatman Schleicher & Schuell, said partnering with BioSource International was perfectly in line with his company’s strategy.
“It’s a perfect fit,” said Negm. “They have the expertise in developing phospho-specific antibodies, and we have the expertise and marketing strategy already in protein arrays.”
According to Brotski, BioSource International has been making phorphorylation site-specific antibodies for the past 10 years. The antibodies are used as reagents for ELISA assays and Western blots.
Making high-quality phosphorylation site-specific antibodies is a task that requires considerable experience, Brotski noted.
“From the very get-go, selecting a sequence to make an immunogen to inject into a rabbit is difficult,” she said. “Then purifying and selecting from all the breeds of animal which is going to produce the cleanest, purified antibody is difficult as well.”
After purification, antibodies at BioSource go through quality control tests, Brotski said. One test is to put non-specific peptides with the antibodies to see if they block the signal. Another test is to create a mutant with a point mutation and to then make sure that it completely obliterates the signal.
“In the manufacturing process we put the antibodies through rigorous quality control tests to make sure we get the most specific antibody,” said Brotski.
Brotski and Negm said the companies plan to introduce two to three additional phosphoarrays with different menus over the next year. The other arrays will be more disease-specific than the first one, Brotski said.
“A lot of what we have on the roadmap is disease specific,” she noted. “The next one will probably be related to insulin regulation and diabetes. Another one will be specific to neurobiology, especially Alzheimer’s disease. Another will be a more specific cancer panel.”
In deciding what arrays to make, the companies listened to what customers said would be interesting, said Brotski. In addition, the arrays draw upon the phosophorylation-site-specific antibodies that BioSource has already developed over the past decade.
“A lot of what we have are cancer cell lines,” said Brotski. “So we thought the arrays would work very well for cancer.”
With phorphorylation-site- specific antibodies already developed, the biggest challenge in producing the phosphoarray was ensuring that there was no cross-talk between antibodies on the array, said Brotski.
“Cross-talk in any multiplexing type of product is always the biggest hurdle,” she added.
In addition, antibodies had to be titered to make sure that they were within the relevant range for analysis.
Development of the new phosphoarray began early in 2004. The product was tested in-house by Whatman Shleicher & Schuell during the summer of 2004, and last week, the product was sent out to various sites for beta testing. Testers include researchers that use phosphorylation-site-specific antibodies for Western blots and ELISA tests, as well as researchers that use BioSource’s Luminex assays.
The Luminex phosphoassays were introduced at the end of 2003. They consist of phophorylation-site-specific antibodies attached to Luminex beads.
“Using the phospholuminex beads, some researchers have already multiplexed these analytes on their own,” said Brotski.
In addition to receiving feedback from beta testers, Brotski said she also plans to test out her company’s new product by following the directions that come with the array to do a few laboratory experiments of her own.
“That’s the true test,” said Brotski. “Take someone who only knows how to hold a pipette and see how hard or easy it is to use the array based on the instructions. Then I’ll have my own perspective to add to it.”
— TSL (This article originally appeared in the Jan. 21, 2005, issue of BioArray News’ sister publication ProteoMonitor.)