( rough the adaptation of a technique de...)Berkeley researchers lay groundwork for cell version of DNA chip

rough the adaptation of a technique, developed earlier by Bertozzi and her research group, called the "Staudinger ligation." Bertozzi's Staudinger ligation utilizes the sugar complexes called "oligosaccharides" that reside on the surface of every cell, and a reaction between two types of molecules, a nitrogen-containing azide, and a phosphorous-containing phosphine, as a means of attaching probes and reagents to cell surfaces, or to link different molecules inside of the cells.

"The Staudinger ligation has been shown to be both cell friendly and precise, so we exploited the reaction to very specifically link a DNA molecule to the surface of a living cell," said Chandra. "DNA is not normally found on the surfaces of cells, so the ability to deliver the DNA strands, keep them there, and use them for a productive purpose is a significant advance."

Chandra, working under the direction of Francis and Bertozzi, used the Staudinger ligation to create a phosphine-DNA conjugate that makes it possible for the DNA to adhere to a cell's surface. The phosphine-DNA conjugate provides an outer layer of adhesion that is independent of the cell's natural stickiness. As a bonus, the researchers are even able to bind their phosphine-DNA conjugates to cells that are not naturally sticky, providing the first known method for attaching non-adherent cell types to other surfaces. This could prove to be a real advantage.

"For example, it should be possible to array multiple types of non-adherent cells on a chip to create a mini-immune system for evaluating potential therapies," said Chandra.

To test the ability of their phosphine-DNA conjugates to bind to cells, Chandra and his colleagues conducted a series of experiments with human embryonic kidney cells. From their results, they estimated that following treatment, each individual cell was coated with approximately 270,000 DNA molecules. Similar results were obtained using a line of human T-cells, cal
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Source:DOE/Lawrence Berkeley National Laboratory

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