Dual‐Enhanced Lanthanide MOF‐Based Fluorescent Bio‐Barcode via Conformational Regulation for Ultrasensitive Detection of DNA Epigenetic Biomarker

Aberrant epigenetic modifications (EMs) serve as critical biomarkers but remain challenging to detect due to their low abundance in biological samples. A lanthanide metal-organic framework (Ln-MOF) bio-barcode method integrating the dual actions of ultrahigh DNA loading density and anion-π interaction-driven fluorescence enhancement for the ultrasensitive detection of EMs, such as 5-formylcytosine (5fC), is developed. The system employs streptavidin-functionalized magnetic beads to selectively capture biotinylated 5fC-modified nucleic acids, which then capture Er-organic framework probes (UiO-66 (Er)) tagged with thousands of quenched fluorescent oligonucleotides (FAM-ODN). After magnetic separation, phosphate-induced desorption restores the fluorescence of oligonucleotides, signaling the presence of 5fC. Subsequently, free phosphate, functioning as both a strong base and an anion, further amplifies fluorescence by altering the conformation of FAM molecules. This dual-action mechanism combines high nucleic acid loading capacity of Ln-MOF and conformation-regulated fluorescence enhancement enables the fluorescent bio-barcode to achieve a detection limit of 0.0225% content. The detection results of 5fC in cellular and thyroid cancer tissue samples confirm global 5fC downregulation as a robust epigenetic hallmark of cancer. The enzyme- and amplification-free design ensures robustness and cost-efficiency, while modular probe architecture enables adaptation to diverse low-abundance targets, from epigenetic modifications to protein biomarkers.