Aptamers as Reversible Sorting Ligands for Preparation of Cells in Their Native State.

Although antibodies are routinely used to label and isolate a desired cell type from a more complex mixture of cells, via either fluorescence-activated cell sorting (FACS) or magnetic-activated cell sorting (MACS), such antibody labeling is not easily reversible. We describe an FACS and MACS compatible method to reversibly label and purify cells using aptamers. Magnetic beads loaded with the epidermal growth factor receptor (EGFR)-binding antagonistic aptamer E07 specifically isolated EGFR-expressing cells, and pure, label-free cells were recovered via treatment with an "antidote" oligonucleotide complementary to the aptamer. Additionally, while FACS sorting cells with E07 or EGFR antibody yielded EGFR(+) cells with impeded EGFR signaling, stripping off the aptamer via antidote treatment restored receptor function, returning cells to their native state, which was not possible with the antibody. The ability to reversibly label or isolate cells without compromising their function is a valuable, versatile tool with important implications for both the laboratory and clinic.