Magneto-responsive UiO-66/Fe@Au NPs for dual-modal detection of exosomal miRNA-92a-3p

Single-sensing strategies for microRNA (miRNA) detection often suffer from high false-positive rates and poor interference resistance. Dual-modal approaches can significantly enhance detection reliability and accuracy. In this study, we developed a fluorescent-colorimetric dual-modal biosensor for exosomal miR-92a-3p detection based on a synergistic system comprising magnetic-driven Fe 3 O 4 -SiO 2 -NH 2 (MB), iron-doped zirconium-based metal-organic framework/gold (UFA) nanoparticles, and catalytic hairpin assembly (CHA). For the colorimetric assay, the oxidase-like (OXD-like) activity of UFA-H1 probes was utilized. The introduction of MB-H2 probes into the system triggered the CHA reaction only in the existence of the target miR-92a-3p, leading to the formation of a UFA-H1-H2-MB sandwich structure. Subsequent magnetic separation drove the UFA nanozymes out of the supernatant, enabling quantitative analysis of target miR-92a-3p through the attenuated colorimetric signal from TMB oxidation. Concurrently, as the fluorescent assay, the probe UFA-H1 was designed with a FAM fluorophore modified at the 3′ end of the H1 hairpin, which was quenched due to Förster Resonance Energy Transfer (FRET) effect. The target initiated CHA reaction forced the H1-H2 hybridization, distancing the FAM fluorophore from the NP surface. This invalidated the FRET effect and led to a significant fluorescence recovery. The proposed biosensor demonstrated a low detection limit of 0.64 pM with excellent selectivity. The assay confirmed the feasibility of quantifying exosomal miR-92a-3p in clinical samples, underscoring its diagnostic utility for cancer liquid biopsy.