A DNAzyme-Based DNA Nanofirework for Amplified Imaging of Intracellular and Intratumoral miRNA

DNAzymes, a class of functional nucleic acids known for their enzyme-like catalytic properties and efficient substrate cleavage activity, have emerged as versatile tools for constructing miRNA detection systems. However, when applied in the complex intracellular environment with interference from highly homologous miRNAs, simple DNAzyme-based sensing probes often suffer from poor cellular permeability and low stability. Herein, we designed a spherical DNA nanostructure (termed DNA nanofirework, abbreviated as DNF) based on DNAzyme for intracellular miRNA-21 imaging. One end of the DNAzyme is initially locked by a locking strand, while the other end is hybridized with a hairpin substrate. The two ends of the hairpin are noncomplementary and can respectively bind to the two termini of a single-stranded linker. Through stepwise connection of substrates based on the linker strands, the DNF is ultimately assembled. The DNF exhibits excellent sensitivity with a detection limit of 42.3 pM, enhanced stability, effective cellular imaging performance, and the ability to distinguish cells with varying miRNA-21 expression levels. Furthermore, upon intratumoral administration, the DNF enabled robust miRNA imaging within the tumor tissue. This DNF system provides an innovative strategy for tumor imaging and holds promise as a reliable tool for local tumor diagnosis.