3′ Poly(dA)-Tailed Thrombin DNA Aptamer to Increase DNase-Resistance and Clotting Inhibitory Activity

Aptamers are an attractive candidate for a molecular-targeted drug since they can show ability to precisely recognize proteins with a large affinity similar to antibodies. A drawback of aptamers is that they can be easily degraded under biological conditions by DNase (or RNase). In this study, we attached poly(dA) tail to the 3′ end of thrombin DNA aptamer and found that its survival time in human plasma was prolonged by about threefold compared to the original aptamers (i.e., without the tail). We found that the attachment of a poly(dA) tail at the 3′ end caused an increase of the clotting inhibitory activity. A preliminary in vivo assay using BALB/c mice confirmed a considerably elongated clotting time for the tailed aptamer. When the poly(dA) tail was attached to three other DNA aptamers, DNase resistance was increased, indicating that the present finding can be universally applied to increase stability of DNA aptamers.