MEMO: A micro memo sensor detecting microRNA-RISC using an accurate cell-free expression platform

Circulating microRNAs have emerged as potential prognostic biomarkers of various diseases. They serve as micro memos sent out by cells, which scientists can intercept to gain real-time insights into cellular and disease status. However, establishing a standardized microRNA detection platform remains a challenge. Here, we integrate the RNA-induced silencing complex (RISC), which occupies mature microRNAs, into a complex cell-free synthetic genetic circuit using three different RNA polymerases, creating an innovative microRNA biosensor that is sensitive, precise, and cost-effective. The RISC protects the microRNA degradation during isolation and ensures the elimination of false target interactions, enhancing the detection robustness. With a limit of detection of 81 pM, affordability, and the possibility for on-demand use, this system proves to be a strong miRNA sensing tool.