DNA Duplex Containing Ag+-Mediated Cytosine–Cytosine Base Pairs as a Catalyst Precursor for the 4-Nitrophenol Reduction with NaBH4

Catalytic applications of DNA duplexes containing Ag⁺-mediated cytosine–cytosine base pairs (C-Ag⁺-C) have not been well investigated. In this study, we demonstrate a novel approach for forming highly active DNA-capped Ag nanoparticle (DNA-AgNP) catalysts for the reduction of 4-nitrophenol (4-NP) using sodium borohydride (NaBH₄). This approach is based on the in situ generation of DNA-AgNPs from DNA duplexes containing C-Ag⁺-C (DNA duplex-Ag⁺). UV–vis spectroscopic analysis suggests that the DNA duplex-Ag⁺ complex acts as an excellent catalyst precursor for 4-NP reduction with NaBH₄. Transmission electron microscopy observations of the reaction solution after the 4-NP reduction reaction using DNA duplex-Ag⁺ provided detailed experimental insights into the mechanism of the catalytic activity of DNA duplex-Ag⁺ for 4-NP reduction. In the reaction solution, DNA-AgNPs were initially formed (DNA duplex-Ag⁺ + NaBH₄ → DNA-AgNPs) and then served as water-soluble catalysts for 4-NP reduction. Notably, the catalytic properties of the DNA-AgNPs generated in situ were affected by the DNA strand length and sequence. The properties of DNA duplex-Ag⁺ may provide a new application of DNA molecules containing metallobase pairs as water-soluble catalyst precursors.