Abstract

The highly sensitive analysis of small-molecule targets holds profound significance across diverse fields, ranging from clinical diagnosis and environmental monitoring to food safety. Herein, we developed a label-free electrochemical CRISPR platform gated by allosteric transcription factors (aTFs) for the ultrasensitive detection of various small molecules. In this system, the specific binding of target analytes to their cognate aTFs induces the release of programmable DNA adaptors, which subsequently trigger Cas12a to trans-cleave DNA probes anchored to the electrode surface. Consequently, the truncated DNA probes serve as initiators to form electroactive G-quadruplex/hemin complexes in situ via terminal deoxynucleotidyl transferase (TdT)-mediated elongation, generating a robust electrochemical response signal. Using TetR as a model aTF, this integrated electrochemical CRISPR biosensor achieved tetracycline detection with picomolar sensitivity. Furthermore, the versatility of this platform was demonstrated by extending its application to p-hydroxybenzoic acid and copper ions through the simple substitution of the aTF modules. The practical utility of the assay was further demonstrated by the robust detection of tetracycline in complex matrices such as milk. Ultimately, this study not only provides a novel strategy for constructing universal, label-free electrochemical CRISPR platforms but also paves the way for the sensitive detection of low-abundance non-nucleic acid targets.