Au nano-flower/organic polymer heterojunction-based cathode photochemical biosensor with reduction-accelerated quenching effect of porphyrin manganese

Abstract

In this work, a novel reduction-accelerated quenching of manganese porphyrin (MnPP) based signal-off cathode photochemical (PEC) biosensor by using Au nano-flower/organic polymer (PTB7-Th) heterojunction as platform was proposed for ultrasensitive detection of Hg²⁺. Firstly, the photoactive PTB7-Th with Au nano-flower on electrode could form a typical Mott-Schottky heterojunction for acquiring an extremely high cathode signal. Meanwhile, the presence of target Hg²⁺ could bring in the formation of T-Hg²⁺-T based scissor-like DNA walker, which thus activated efficient Mg²⁺-specific DNAzyme based cleavage recycling to shear hairpin H2 on electrode to exposure abundant trigger sites of hybridization chain reaction (HCR) for in-situ decoration of quencher MnPP. Here, besides the steric hinderance and light competition effect of MnPP decorated DNA nanowires attributing to signal decrease, we for the first time testified the MnPP reduction-accelerated quenching that constantly consumed the photo-generated electron by using cyclic voltammetry (CV). As a result, the proposed biosensor had excellent sensitivity and selectivity to Hg²⁺ in the range of 1 fM-10 nM with a detection limit of 0.48 fM. The actual sample analysis showed that the biosensor could reliably and quantitatively identify Hg²⁺, indicating an excellent application prospect in routine detection.

Keywords: Mott-Schottky heterojunction; Photocathode biosensor; Quenching effect; Reduction reaction; Signal amplification.