An Aptamer‐Based Bound/Free Separation System for Protein Detection

Aptamer hybridizes with its complementary strand. However, the complementary strand has difficulties to hybridize with the aptamer bound to a target because the aptamer forms higher‐order structures. Exploiting this property, we developed simple bound/free separation systems for thrombin and IgE detection. The complementary strand was immobilized onto beads and the aptamer was labeled with pyrroquinoline quinone glucose dehydrogenase (PQQGDH). In the absence of a target, the aptamer is trapped by beads, whereas in the presence of a target, the aptamer bound to the target is not trapped. Thus the aptamer‐target complexes can be recovered easily and detected by PQQGDH activity. This system allow the detection of 270 pM thrombin and 1 nM IgE.