Highly Efficient Electrochemiluminescent Silver Nanoclusters/Titanium Oxide Nanomaterials as a Signal Probe for Ferrocene-Driven Light Switch Bioanalysis.

In this work, a ferrocene (Fc)-driven light switch biosensor for ultrasensitive detection of amyloid-β (Aβ) was designed by utilizing the highly efficient electrochemiluminescent nanomaterials of silver nanoclusters/titanium oxide nanoflowers (Ag NCs/TiO2 NFs) as signal labels. Through combining the TiO2 NFs as the coreaction accelerator and dissolved O2 as the intrinsic coreactant to in situ generate the strong oxidizing intermediate radical OH•, the electrochemiluminescence (ECL) of Ag NCs on the TiO2 NFs surface could be significantly promoted in comparison with that of pure Ag NCs in solution. Further, Fc-labeled DNA as the ECL quenching probe was introduced to dramatically restrain the ECL emission of nanomaterials, which facilitated improving the sensitivity of the prepared biosensor to a large extent. Surprisingly, tiny amounts of target protein could be recognized by the immunoreaction-induced DNA nanostructure for outputting numerous secondary-target DNAs, which further triggered the release of Fc to recover the ECL signal, realizing the ultrasensitive detection of target. As a result, this developed assay for Aβ detection demonstrated excellent sensitivity with a linear range from 50 fg/mL to 500 ng/mL and limit of detection down to 32 fg/mL, which opened up a new research direction for ultrasensitive ECL bioanalysis-based metal NCs.