Dual-Enhanced Lanthanide MOF-Based Fluorescent Bio-Barcode via Conformational Regulation for Ultrasensitive Detection...

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.