Rapid and Dense Immobilization of Nucleic Acids on Lanthanide-Doped Nanoparticles for Enhanced-Sensitivity Förster Resonance Energy Transfer-Based Diagnostics.

Rapid and dense DNA functionalization of upconversion nanoparticles (UCNPs) remains a critical bottleneck, as conventional covalent and electrostatic methods suffer from low labeling efficiency and time-consuming processing. We report a microwave-assisted rapid dehydration method for efficient DNA immobilization on UCNPs within 3 min, drastically outperforming conventional strategies. This rapid dehydration method demonstrates broad applicability across diverse UCNP compositions, morphologies, and different DNA chain lengths. Molecular dynamics simulations confirm the underlying mechanism: strong noncovalent interactions between DNA phosphate groups/bases and lanthanide ions. Utilizing this approach, we constructed a FRET biosensor by integrating the DNA-functionalized UCNPs with Nb2CTx MXene nanosheets. This platform achieved an ultralow limit of detection of 8.5 pM for SARS-CoV-2 oligonucleotides, representing a 107.5-fold improvement. Importantly, the biosensor was successfully validated using real COVID-19 clinical samples, effectively distinguishing between negative and positive results. The presented DNA functionalization strategy holds immense potential for advancing the design and synthesis of diverse nucleic acid-functionalized nanomaterials for advanced therapeutic and diagnostic applications.