Triggering isothermal exponential amplification of microRNA via liposome fusion

Lipid membrane vesicles serve as essential cellular compartments where diverse biochemical reactions are regulated through dynamic membrane remodeling, including vesicle fusion. Reconstructing these processes in vitro is crucial for advancing artificial nanobiotechnology. Among intracellular metabolic reactions, isothermal nucleic acid amplification is particularly important because it enables sensitive detection of nucleic acid biomarkers. In this study, we focused on exponential amplification reaction (EXPAR), a straightforward isothermal amplification method initiated by microRNA (miRNA), and developed a system, in which fusion of giant unilamellar vesicles (GUVs) triggers the delivery of miRNA into the reaction compartment, thereby initiating amplification. Using our previously reported microdevice with microchambers and high-aspect-ratio electrodes, we monitored both membrane fusion and the subsequent amplification reaction in situ. This platform provides a proof of concept for detecting nucleic acid biomarkers encapsulated in membrane-bound vesicles and offers promising applications in artificial cell systems and in situ analysis of extracellular vesicles such as exosomes.