Cyclometalated ruthenium (II) complex-based nanoparticles for enhanced microRNAs detection and imaging in living cells

MicroRNA (miRNA) imaging in living cells is paramount for comprehending its dynamic functions and profiles, offering valuable insights into miRNA-related cellular processes. However, this remains challenging due to limited transfection agents and the low abundance of miRNAs. Herein, a smart nanosystem was proposed for miRNA imaging in living cells by ingeniously integrating cyclometalated ruthenium (II) nanoparticles (RuNPs) with a catalyzed hairpin assembly (CHA) strategy. Three cyclometalated ruthenium (II) complexes were synthesized and employed self-assembly technology to construct RuNPs. After evaluating their loading efficiency (L_E), fluorescence quenching rates (Q_E), and fluorescence recovery rates (R_E) for Hairpins, RuNPs-1 was selected to construct the Hairpins@RuNPs-1 nanosystem. With a detection limit of 1.5 pM, the Hairpins@RuNPs-1 nanosystem demonstrated high sensitivity for miR-25, live cell imaging confirmed its ability to detect intracellular miR-25 and differentiate its expression in various cells with excellent biocompatibility. We believe it has the potential to become an effective tool for nucleic acid research and would be poised to significantly influence the diagnosis and treatment of diseases.