Imaging intracellular metabolite and protein changes in live mammalian cells with bright fluorescent RNA-based genetically encoded sensors

Engineered aptamers for molecular imaging

Molecular imaging, including quantification and molecular interaction studies, plays a crucial role in visualizing and analysing molecular events occurring within cells or organisms, thus facilitating the understanding of biological processes. Moreover, molecular imaging offers promising applications for early disease diagnosis and therapeutic evaluation. Aptamers are oligonucleotides that can recognize targets with a high affinity and specificity by folding themselves into various three-dimensional structures, thus serving as ideal molecular recognition elements in molecular imaging. This review summarizes the commonly employed aptamers in molecular imaging and outlines the prevalent design approaches for their applications. Furthermore, it highlights the successful application of aptamers to a wide range of targets and imaging modalities. Finally, the review concludes with a forward-looking perspective on future advancements in aptamer-based molecular imaging.

A universal orthogonal imaging platform for living-cell RNA detection using fluorogenic RNA aptamers

MicroRNAs (miRNAs) are crucial regulators of gene expression at the post-transcriptional level, offering valuable insights into disease mechanisms and prospects for targeted therapeutic interventions. Herein, we present a class of miRNA-induced light-up RNA sensors (miLS) that are founded on the toehold mediated principle and employ the fluorogenic RNA aptamers Pepper and Squash as imaging modules. By incorporating a sensor switch to disrupt the stabilizing stem of these aptamers, our design offers enhanced flexibility and convertibility for different target miRNAs and aptamers. These sensors detect multiple miRNA targets (miR-21 and miR-122) with detection limits of 0.48 and 0.2 nM, respectively, while achieving a robust signal-to-noise ratio of up to 44 times. Capitalizing on the distinct fluorescence imaging channels afforded by Pepper-HBC620 (red) and Squash-DFHBI-1T (green), we establish an orthogonal miRNA activation imaging platform, enabling the simultaneous visualization of different intracellular miRNAs in living cells. Our dual-color orthogonal miLS imaging platform provides a powerful tool for sequence-specific miRNA imaging in different cells, opening up new avenues for studying the intricate functions of RNA in living cells.