Relative Nuclease Resistance of a DNA Aptamer Covalently Conjugated to a Target Protein.

A major obstacle to the therapeutic application of an aptamer is its susceptibility to nuclease digestion. Here, we confirmed the acquisition of relative nuclease resistance of a DNA-type thrombin binding aptamer with a warhead (TBA 3 ) by covalent binding to a target protein in the presence of serum/various nucleases. When the thrombin-inhibitory activity of TBA 3 on thrombin was reversed by the addition of the complementary strand, the aptamer was instantly degraded by the nucleases, showing that the properly folded/bound aptamer conferred the resistance. Covalently binding aptamers possessing both a prolonged drug effect and relative nuclease resistance would be beneficial for in vivo translational applications.