An in situ-boosted electrochemiluminescence biosensor for serotonin detection sensitized with Co₃O₄ nanoplates and...

Here, we described an in situ-boosted electrochemiluminescence (ECL) biosensor for serotonin detection sensitized with the catalysis of Co₃O₄ nanoplates and self-feedback DNA recycling (SFDR). Specifically, aptamer:S duplex was attached onto the surface of magnetic beads via amide bond. When serotonin presented, it competitively combined with aptamer from aptamer:S duplex. Then, the released S strands reacted with hairpin DNA (H) containing the silenced Mg²⁺-assisted DNAzyme site in the loop part that immobilized on CdS quantum dots (CdS QDs) modified electrode. The activating Mg²⁺-assisted DNAzyme cut off H and re-liberated S strands. Therefore, the Mg²⁺-DNAzyme-aided recycle happened to produce numerous residual single-stranded DNA segments and then reacted with Co₃O₄-modified P strands on the electrode surface. Such results directly introduced Co₃O₄ nanoplates close to CdS QDs, resulting in the reduction of H₂O₂ to •OH and the increase of ECL emission of CdS QDs in CdS QDs-H₂O₂ system. Based on such signal amplification strategy, a low detection limit of 1.5 pM was obtained for serotonin detection. This approach enabled the proposed ECL biosensor promising for the future application in the trace detection of serotonin.