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