Improving Spinach2-and Broccoli-based biosensors for single and double analytes

The use of “Spinach”-based RNA sensors for the detection of small metabolites and proteins has received growing interest in the recent years. While this approach can be used in vivo for cell sensing and in vitro for microfluidic assays, their overall utility is limited as a result of a high magnesium ion dependence. Here, we alleviate this limitation through incorporating a human tRNA^Lys3 or an engineered viral F30 (a three-way junction RNA motif) scaffold to facilitate aptamer folding in vitro and improve the performance of selected streptavidin, tyrosine, and thrombin aptamers as exemplary cases. Furthermore, we demonstrate the use of a Broccoli aptamer scaffold in conjunction with the viral F30 to enable simultaneous sensing of two molecules in a logic gate type fashion. Our proof-of-concept results demonstrate the ability to redesign these aptamer sensors for improved brightness as well as signal stability without the need for high magnesium—both traits that can further enhance downstream screening applications.