Reversed Regulation Effects of ssDNA on the Mimetic Oxidase and Peroxidase Activities of Covalent Organic Frameworks

Nanomaterials with enzyme mimetic activity have attracted extensive attention, especially in the regulation of their catalytic activities by biomolecules or other polymers. Here, a covalent organic framework (Tph-BT COF) with excellent photocatalytic activity is constructed by Schiff base reaction, and its mimetic oxidase activity and peroxidase activity is inversely regulated via single-stranded DNA (ssDNA). Under light-emitting diode (LED) light irradiation, Tph-BT exhibited outstanding oxidase activity, which efficiently catalyzed oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) to produce blue oxTMB, and ssDNA, especially those with poly-thymidine (T) sequences, can significantly inhibit its oxidase activity. On the contrary, Tph-BT showed weak peroxidase activity, and the presence of ssDNA, particularly poly-cytosine (C) sequences, can remarkably enhance the peroxidase activity. The influence of base type, base length, and other factors on the activities of two enzymes is also studied, and the results reveal that the adsorption of ssDNA on the surface of Tph-BT prevented intersystem crossing (ISC) and energy transfer processes to reduce O-1(2) generation, while the electrostatic interaction between ssDNA and TMB enhanced Tph-BT's affinity for TMB to facilitate the electron transfer from TMB to (OH)-O-center dot. This study investigates multitype mimetic enzyme activities of nonmetallic D-A conjugated COFs and demonstrates their feasibility of regulation by ssDNA.

Automated summary

A covalent organic framework (Tph-BT COF) with excellent photocatalytic activity is constructed by Schiff base reaction, and its mimetic oxidase and peroxidase activities are inversely regulated by single-stranded DNA (ssDNA). Under LED light irradiation, Tph-BT exhibits outstanding oxidase activity, which is inhibited by ssDNA with poly-thymidine (T) sequences, while its weak peroxidase activity is enhanced by ssDNA with poly-cytosine (C) sequences. The study also investigates the influence of base type, base length, and other factors on the activities of the two enzymes, revealing the mechanisms behind the regulation by ssDNA.