News | June 7, 1999

Gel Microdrop Secretion Assay

One Cell Systems Inc. (Cambridge, MA) has developed a new method of screening cell lines for rare, high secretors. The Gel Microdrop (GMD) Secretion Assay isolates individual, viable cells based on the amount of secreted protein, providing a rapid, efficient flow cytometric alternative to limiting dilution cloning.

In the GMD Secretion Assay, a unique, derivatized gel matrix (CelBioGel Encapsulation Matrix) surrounding each cell functions similarly to an antibody-coated microwell. Cells of interest are first encapsulated in CelBioGel using the CelSys 100 Microdrop Maker, forming GMDs. Streptavidin is added, creating a bridge to which a biotinylated "capture" antibody will subsequently be bound. The GMDs with the cells and bound capture antibody are incubated for secretion and capture of the target protein. A fluorescent-labeled "detection" antibody is incubated with the GMDs, and the samples are prepared for flow cytometry and sorting. The fluorescence intensity of each GMD is quantified, and high producers are isolated and recovered based on secretion of the specific target protein.

Using the GMD Secretion Assay, producer cells can be identified shortly after transfection or fusion. Rare, high secretors can be recovered for cloning or gene analysis in days instead of the weeks to months that are required for limiting dilution cloning. The assay dramatically reduces manual limiting dilution cloning, improving yields and productivity while reducing product development time and costs.

This diagram illustrates the basis for the GMD Secretion Assay. Each cell is encapsulated within CelBioGel Encapsulation Matrix (left). Using streptavidin as a bridge, biotinylated antibody specific for the secreted protein of interest is distributed throughout the Microdrop (magnified view). After a secretion incubation, frequently as short as 15 minutes, the secreted protein bound in the Microdrop is quantified by the addition of a second antibody which is fluorochrome-labeled. Each cell can then be evaluated for secretion of specific proteins via the intensity of the Microdrop-associated fluorescence.

About One Cell
One Cell Systems develops, manufactures, and commercializes proprietary assays for the rapid detection, isolation, and analysis of single cells. The company's technologies encompass the processes, materials, and methods of encapsulating cells in Gel Microdrops permitting rapid detection and selection using flow cytometry and digital image analysis. The technology and products are covered by numerous issued and pending US and International Patents.

For More Information: Howard Kartstein, Director of Marketing and Sales, One Cell Systems Inc., 100 Inman St., Cambridge, MA 02139. Tel: 617-868-2399, ext. 309. Fax: 617-492-7921. Email: