Ultrasensitive Organic Photoelectrochemical Transistor Biosensor Based on DNA as Nanocarrier for Efficient Immobilization of Signal Probe with Pimping Background

Organic photoelectrochemical transistor (OPECT) assays are mainly focused on the improvement of photoactive materials at the gating interface, which leads to an enhanced initial signal alongside significant background noise. This phenomenon can cause considerable deviations and impose limits on target detection. In this study, we achieved sensitive and low-background detection of alkaline phospholipase (ALP) activity using single-stranded DNA (ssDNA) as a nanocarrier to effectively immobilizing CdS quantum dots (QDs) sensitizing UiO-66. Specifically, ssDNA-labeled CdS QDs could be connected to UiO-66 via Zr-O-P bonds, while sodium tripolyphosphate (STPP) interfered with the binding of CdS QD-ssDNA to UiO-66 due to an occupancy effect. The hydrolysis of STPP, catalyzed by ALP, diminished this occupancy effect, allowing for increased binding of CdS QDs-ssDNA to UiO-66 and thereby enhancing the responsive signal. The competitive dynamic between STPP and ssDNA allowed for controlled binding of CdS QDs-ssDNA photosensitizers on UiO-66, thus realizing sensitive detection of ALP. This organic integration of biological modulation and signal amplification in OPECT has led to the creation of a novel sensing platform for detecting ALP concentrations ranging from 0.005 to 100 U·L^-1, and the detection limit is 0.0012 U·L^-1, thus paving the way for innovative approaches to sensitively monitor ALP activity.