Abstract: In accordance with the present invention, there is provided a nucleic acid target-dependent adapter linked to a nucleic acid sequence. The adapter comprises linked together a biosensor having a specific sequence complementary to a target sequence of a substrate, the biosensor improving the specificity of the nucleic acid sequence for the substrate, and a blocker stem sequence complementary to a portion of the nucleic acid sequence. In absence of the target sequence of the substrate, the blocker stem sequence forms an intramolecular stem with the nucleic acid sequence linked thereto, preventing exposition of the sequence of the nucleic acid sequence, thus locking the nucleic acid sequence so linked to the adapter in an inactive conformation, and in presence of the target sequence, the blocker stem sequence dissociating from the nucleic acid sequence, thus exposing the nucleic acid sequence linked to the adapter in an active conformation.