A homogeneous DNA assay by recovering inhibited emission of rare earth ions-doped upconversion nanoparticles

Robust and easy-to-use kits specific for a particular DNA sequence are desirable for early detection of diseases. However, the major challenge with these tests is often the background fluorescence artifacts arising from biological species due to employing UV and visible range of light. Here, we have reported a near-infrared (NIR) fluorescence “turn-on” kit based on rare earth ions doped nanoparticles, upconversion nanoparticles (UCNPs), and gold nanoparticles (AuNPs), which forms a fluorescence-quencher pair, brought together by a hairpin structure through the formation of double-stranded DNA (dsDNA), with quenched upconversion luminescence. In the presence of analytes, the molecular beacon opens to push AuNPs away from UCNPs, with a distance longer than the efficient quenching distance, so that the inhibited upconversion emission will be restored. We demonstrated that this assay provides a homogeneous, facile, simple and highly selective HIV-1 based DNA detection system with restore efficiency up to 85%, and the detection limit of 5 nm.