DNA Programmable Peroxidase Activity of Oxidized Polypyrrole Quantum Dots

Significant progress has recently been made in the application of oxidized graphene (GO) quantum dots as enzyme mimics in various biomedical fields due to their bio-compatibility and excellent solubility in physiological media. However, their catalytic performance and controllability are barely satisfactory. Here, this study constructs oxygen-functionalized polypyrrole quantum dots (o-ppy QDs) with excellent peroxidase activity in a mild condition. Compared with oxidized graphene QDs, o-ppy QDs exhibit superior catalytic efficiency (120 times higher than HRP). More importantly, it is found that guanine (G) and adenine (A) bases possess higher binding affinities to o-ppy QDs. G base is able to significantly increase the peroxidase activity while A base decreases the activity, providing a fascinating method to precisely regulate the catalytic activity of o-ppy QDs in a programmable manner by the design of DNA sequences. The enhancement on the peroxidase by G base regulation is attributed to the existence of carbonyl group that promotes its catalytic activity, while A base tends to block the original carbonyl group on o-ppy QDs. Based on this feature, a colorimetric and fluorescent dual-mode biosensor for detecting DNA methylation is developed. This study holds significant theoretical and practical implications for the development of nanozymes and precise regulation of their catalytic activity.