A Strategy Employing a TF-splinting Duplex Nanoswitch to Achieve Single-step, Enzyme-free, Signal-on Detection of L-Tryptophan

Transcription factor (TF)-based metabolite detection mainly depends on TF-regulated gene expression in cells. From TF activa-tion to gene transcription and translation, the signal travels a relatively long way before it is received. Here, we propose a TF-splinting duplex DNA nanoswitch to detect metabolites. We show its feasibility using tryptophan repressor (TrpR) to detect L-tryptophan as a model. The assay has been optimized and characterized after obtaining proof-of-concept, and the detection of L-tryptophan in complex biological samples is feasible. Unlike an equivalent gene expression approach, the whole process is a single-step, enzyme-free and signal-on method. It can be completed within 20 min. This proposed TF-splinting duplex (TFSD) has the potential to be applied to the quick and convenient detection of other metabolites or even TFs.