Anisotropic Au Nanorods with Dual SPR Absorption Enable Programmable DNA-Assembled Dye-Sensitized Upconversion Nanoprobe.

The unique anisotropy of gold nanorods (Au NRs) endows them with two intense SPR absorption bands, making them widely used for constructing fluorescent probes that operate in a "quench-and-recover" mode. Nevertheless, most existing Au NR-based probes utilize only one SPR absorption to quench the fluorescence and thus do not fully exploit the quenching potential of Au NRs. Herein, we employ dye-sensitized upconversion nanoparticles (UCNPs) as the energy donor and harness both SPR absorptions to quench the emissions from the dye and the UCNPs, thereby achieving full utilization of the quenching capacity of Au NRs. A DNA-programmed nanosatellite assembly probe that integrates near-infrared (NIR) dye-sensitized UCNPs with Au NRs through DNA base pairing was designed. In the nanosatellites, the longitudinal SPR absorption quenches the NIR dye, suppressing dye sensitization and decreasing the emission of UCNPs, while the transverse SPR absorption quenches the emission of the UCNPs, enabling efficient quenching of the total emission of the dye-sensitized UCNPs. This dual-SPR quenching achieves a high quenching efficiency of 98.5%. In the presence of target miRNA, the nanosatellites disassemble into Au NRs and dye-sensitized UCNPs, restoring the luminescence of UCNPs, with a maximum signal-to-background ratio of 16.4 and a detection limit of 71 fM. The probe performs well in complex biological samples, offering a programmable strategy that takes full advantage of the anisotropic plasmonic properties of Au NRs for sensitive nucleic acid analysis.