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A research group led by Prof. Wang Hui and Prof. Zhang Xin from the Hefei Institutes of ÃÈÃÃÉçÇøical Science of the Chinese Academy of Sciences introduced a new strategy to prepare ultrahigh density copper single-atom enzymes for tumor self-cascade catalytic therapy.

"The powerful enzymes can help to fight tumors," said Dr. Liu Hongji, a member of the research team.

The study is in Chemical Engineering Journal.

The low-valence Cu single atom enzymes (Cu^Ⅰ SAEs) contribute to alleviating the inefficient generation of ·OH dilemma in the tumor microenvironment, especially in the presence of overexpressed glutathione (GSH). However, the conveniently controlled synthesis of Cu^Ⅰ SAEs with high atom density remains a challenging task due to the cumbersome process, compositional heterogeneity, poor water solubility, and uncontrollable metal valence.

To solve this dilemma, the researchers proposed a well-controlled one-step solvent self-carbonization-reduction strategy to fabricate Cu^â…  SAEs with ultrahigh atomic density. Formamide can easily be condensed into a linear macromolecular chain for chelating Cu^â…¡ because of its high N content and vacant ligand sites. The resultant carbon nitride-based fragments reduce Cu^â…¡ to Cu^â… .

"The obtained Cu^â…  SAEs has an incredibly high density of 23.36 wt. %, surpassing previously reported metal- or carbon-based supported Cu single-atom catalysts," explained Liu.

This comes from the well-defined Cu^â…  species, whereas aberration-corrected scanning transmission electron microscopy and the X-ray absorption fine structure spectroscopy corroborate the Cu^â…  species existed in the form of single atoms.

"The Cu^â…  SAEs showed remarkable self-cascade catalytic activities, leading to a tumor inhibition rate up to 89.17 %," he added.

This study provides a novel strategy for fabricating valence-controlled SAEs supported on C₃N₄ for catalytic applications, according to the team.