Bidirectional Enzyme Inhibition and Activation for In Situ Formation of Injectable Hydrogel Using a Bispecific Aptamer.

In situ injectable hydrogels have been explored for biomedical applications, including regenerative medicine and drug delivery. However, controlling the kinetics of their gelation to facilitate easy injection remains a challenge. The purpose of this study was to demonstrate the potential of using bispecific aptamers and complementary sequences as a bidirectional modulation system for controlling enzyme-mediated hydrogel formation kinetics. The results show that a bispecific thrombin-binding aptamer effectively inhibits thrombin activity and significantly slowed fibrin hydrogel formation. Upon interaction with its complementary sequence, this inhibition could be reversed. As a result, the aptamer-bound thrombin was activated, leading to an acceleration of the fibrin formation kinetics. Thus, bispecific aptamers and complementary sequences can effectively function as dynamic control systems for enzyme-catalyzed in situ injectable hydrogel formation.