Ultrasensitive Organic Photoelectrochemical Transistor\nBiosensor Based on DNA as Nanocarrier for Efficient Immobilization\nof Signal Probe with Pimping Background

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