Dual-emitting polyfluorene derivatives nanoparticles coupling bifunctional coreaction promoter Ag nanoparticles for ratiometric electrochemiluminescence bioanalysis

The excellent ECL properties of polyfluorene derivatives have made them widely studied and applied. However, their studies focused on remarkable anodic emission. In fact, the dual-emission characteristics of luminophores are fascinating for building ratiometric biosensors. This work creatively modulated the dual-emission of poly [(9,9-dioctyl-fluorenyl-2,7-diacyl)-alt-co-(9-hexyl-3,6-carbazole)] (PFA) using bovine serum albumin (BSA) as functionalization reagent and stabilizer. Surprisingly, the resulting PFA nanoparticles (PFA NPs) can simultaneously emit two stable ECL signals at + 1.1 V and − 2.0 V with N,N-diisopropylethylenediamine (DPEA) and persulfate (S2O82-) as coreactants, respectively. Furthermore, silver nanoparticles (Ag NPs) were exploited as bifunctional coreaction promoter for synchronously enhancing two emissions from PFA NPs. Dual-emitting PFA NPs cleverly combined with bifunctional coreaction promoter Ag NPs to construct ratiometric ECL system for detecting tau protein phosphorylated at threonine 181 (p-tau 181). High-efficiency rolling circle amplification (RCA) integrated programmable primer exchange reaction (PER) to effectively improve the detection sensitivity. The limit of detection was as low as 6.9 fg·mL−1. PFA NPs coupling Ag NPs created an attractive single-luminophore-based ECL ratiometric sensing platform, greatly expanded the application of polyfluorene derivatives in ECL field, as well as provided a highly sensitive detection method of p-tau 181 for early diagnosis of Alzheimer's disease (AD).