Microfluidic paper-based photoelectrochemical sensing platform with electron-transfer tunneling distance regulation strategy for thrombin detection.

This work reports a microfluidic paper-based photoelectrochemical (μ-PEC) sensing platform for thrombin (TB) detection with electron-transfer tunneling distance regulation (ETTDR) and aptamer target-triggering nicking enzyme signaling amplification (NESA) dual strategies. Specifically, paper-based TiO2 nanosheets (PTNs) were prepared with an efficient hydrothermal process, serving as the direct pathway for the charge carriers transfer. When CeO2-labeled hairpin DNA 3 (HP3) was closely located at the PTNs, the CeO2-PTNs heterostructure was formed, which could great facilitate the photogenerated carries separation of CeO2. In addition, with the aid of aptamer target-triggering NESA strategy, the input TB could be transducted to numerous output target of DNA (tDNA), achieving the goal of desirable signal amplification. In the presence of TB, the output tDNA could be further hybridized with HP3 and unfold its hairpin loop, which forced the CeO2 away from the surface of PTNs and vanished the CeO2-PTNs heterostructure, resulting in the obviously reducing of photocurrent signal. The as-designed sensing platform exhibited a linear range from 0.02 pM to 100 pM with a detection limit of 6.7 fM. Importantly, this μ-PEC sensing platform could not only realize the highly efficient TB detection, but also pave a luciferous way for the detection of other protein in bioanalysis.