Sensitive detection and accurate bioimaging of circRNA based on sponge amplification using a DNA tetrahedral nanoprobe

Circular RNAs (circRNAs) have attracted significant attention due to their unique stable structure and specific expression in various cells and tissues, emerging as promising biomarkers for various diseases. Sensitive detection and accurate bioimaging of circRNAs are crucial for the diagnosis of related diseases. Hence, a novel fluorescent DNA tetrahedron nanoprobe (DTNP), based on the miRNA sponge amplification property of circRNAs, was developed for highly sensitive detection of circRNAs in clinical samples and accurate <i>in situ</i> bioimaging of endogenous circRNAs in living cells. Due to the excellent sponge amplification and programmability of DNA tetrahedra, DTNP demonstrates excellent selectivity, single-base resolution and high sensitivity for circMTO1 with a low limit of detection (LOD) of 79 pM. DTNP allows for direct and highly sensitive detection of circRNA expression levels in clinical samples. Furthermore, owing to DTNP's efficient cellular uptake capabilities, it achieved <i>in situ</i> imaging of endogenous circRNAs in living cells and precisely distinguished between tumor cells and normal cells. This developed strategy is crucial for exploring the potential applications of circRNA-related clinical diagnostics in the biomedical field.