Labelling of live cells using fluorescent aptamers: binding reversal with DNA nucleases

A reversible cell labelling method has been developed for non-destructive and non-invasive cell labelling and purification. Our method uses high affinity single strand DNA (ssDNA) aptamers against surface exposed target molecules on cells. The aptamers are subsequently removed from the cell surface using DNase nuclease treatment. We exemplified our method by labelling human acute lymphoblastic leukemia cells with Qdot-ssDNA aptamers, and restoring them to the label-free condition by treatment with Benzonase. Binding of the fluorescent-aptamers to the cells was evaluated by measuring fluorescence intensity and was further confirmed using flow cytometry. Removal of the aptamers can be achieved in ~10 min by the DNase nuclease digestion. Incubation of cells with aptamers or with the nucleases results in no apparent damage to the cells and does not affect their growth rates. The latter were equivalent to the rates measured for the untreated cells. Our method provides an alternative to traditional antibody-based techniques and could be especially suitable for non-invasive reversible cell labelling and cell separations where maintaining native cell activity is needed.