CRISPR/Cas12a-Sheared ZIF-Based Heterojunction to Allow Polarity-Switchable Photoelectrochemical and Nanozyme-Enabled\nColorimetric Dual-Modal Biosensing

Modulating\nthe migration of interfacial carriers in heterojunctions\nis critical for driving the signal response of high-performance optical\nbiosensors. In this study, a polarity-switchable photoelectrochemical\n(PEC) and nanozyme-enabled colorimetric dual-modal biosensor is designed\nto modulate the interfacial carrier migration of the zeolitic imidazolate\nframework (ZIF)-based heterojunction by exploiting stem-loop DNA and\nthe CRISPR/Cas12a system. Specifically, ZIF-hemin (ZIF-Hemin) is assembled\nat the CdSe/NH<sub>2</sub>-rGO interface via stem-loop DNA to form\na ZIF-based heterojunction. Stem-loop DNA with a reinforcing rib effect\nenhances binding and accelerates the interfacial carrier migration\nof the heterojunction. In the presence of the target Cry1Ab, the CRISPR/Cas12a\nsystem is activated to shear the ZIF-based heterojunction, resulting\nin the disintegration of the heterojunction and the disappearance\nof interfacial carrier migration. At this point, ZIF-Hemin is released\nfrom the CdSe/NH<sub>2</sub>-rGO interface, with the photocurrent\nswitching from the anode to the cathode. Meanwhile, due to its rich\naccessible active sites, the released ZIF-Hemin nanosheet shows high\nperoxidase-like catalytic activity and generates colorimetric signals.\nThe dual-modal biosensor demonstrates excellent performance in selectivity\nand sensitivity, with low detection limits of 0.05 pg mL<sup>–1</sup> (PEC) and 0.4 pg mL<sup>–1</sup> (colorimetric). This work\nprovides a general strategy to improve the performance of optical\nbiosensors by modulating the migration of interfacial carriers in\nheterojunctions.