Ratiometric detection of transcription factor based on Europium(III) complex-doped silicon nanoparticles and a G-quadruplex-selective Iridium(III) complex

To sensitively detect transcription factor (TF) in complicated biological systems, a ratiometric luminescent detection system based on europium(III) complex-doped silicon nanoparticles (SiNPs) and a G-quadruplex (G4)-selective iridium(III) complex has been successfully constructed. During the biosensor fabrication, the G-rich hairpin DNA H1 was immobilized on the surface of SiNPs which was doped with the europium(III) complex Eu(III)(EDTA)(DPA). The dsDNA (S1/S2) contains TF recognition site, and one of its ssDNA S2 is protected by TF from the digestion of exonuclease III (Exo III). The survived S2 starts a signal amplification process at the aid of Exo III, then a lot of G4 DNA was generated which can be recognized by the G4-selective iridium(III) complex (Ir(III)-2G). So, the emission intensity of Ir(III)-2G is enhanced with the increase of TF concentration, while the emission of Eu(III)(EDTA)(DPA) keeps stable. Ascribed to the long lifetimes of both metal complexes, the constructed detection platform can perform time-resolved emission spectroscopy (TRES) measurement in complicated biological systems. The ratiometric TF detection platform not only can detect NF-κB P50 in buffered system in the linear range of 0.05–5 nM with the limit of detection (LOD) 0.014 nM, but also is able to monitor NF-κB P50 in 10% human serum in the linear range of 0.05–5 nM with the LOD of 0.010 nM through TRES measurement. The two-metal complex-based ratiometric TF biosensor provides new strategy for low concentrations of biomarker detection in the complicated biological systems.