A photofuel cell-driven self-powered genosensor with a triple-quenching tag of p-Cu2O/Ti3C2Tx for signal amplification

Herein, an ultrasensitive self-powered genosensor is constructed by modifying a model hairpin capture DNA (cDNA) on a nanostructured n-type CdS modified ITO (n-CdS|ITO) photoanode of a photofuel cell. Then, the modified hairpin cDNA is transformed into a single-stranded DNA (ssDNA) by a target DNA (tDNA) and lambda-exonuclease. Afterwards, a triple-quenching tag is specially designed by the in situ growth of p-type Cu2O nanoparticles on ultrathin (a few layers) Ti3C2Tx nanosheets to form a p-Cu2O/Ti3C2Tx composite. This is then introduced onto the photoanode surface via strong chelation between the exposed Ti ions on Ti3C2Tx and the ssDNA on n-CdS|ITO. The introduction of p-Cu2O/Ti3C2Tx dramatically decreases the open-circuit voltage (E-ocv) of the genosensor and is based on a p-n type semiconductor quenching strategy. This strategy simplifies the complex and expensive aptamer chain design and modification process for the introduction of p-type semiconductors in other biosensing platforms based on a similar quenching mechanism. Meanwhile, both p-Cu2O and Ti3C2Tx exhibit good peroxidase-like catalytic activity, which results in precipitation and steric hindrance on n-CdS|ITO to further quench the output signals. Furthermore, the large Ti3C2Tx nanosheets partially blocked the light absorption of n-CdS. Due to this triple-quenching effect, a wide linear range (1 fM similar to 100 pM) and a low detection limit (0.230 fM, S/N = 3) are obtained by the genosensor for detecting the tDNA, in this case a biomarker for chronic myelogenous leukemia.