Validating DNA-templated Silver Nanoclusters as Type II Photosensitizers using Chronoamperometry

DNA-templated silver nanoclusters (AgNCs@DNA) exhibit significant antibacterial activity. While beneficial, the mechanism of this activity remains unknown. Our research focuses on validating the hypothesis that AgNCs@DNA act as type II photosensitizers, generating radical singlet oxygen species upon photoexcitation. Initial experiments utilized fluorescent spectroscopy to measure the response of AgNCs@C12DNA in the presence of a specific fluorescent reagent that reacts with singlet oxygen species. Although the results were promising, the reliability of the reagent was questioned due to the significant optical overlap produced by AgNCs and the reagent. To overcome this challenge, we implemented another approach, chronoamperometry, to measure current generated by singlet oxygen and amplified by hydroquinone (HQ). The setup was validated using Eosin Y, a known type II photosensitizer, which responds to green excitation at 532 nm. We have optimized the experimental design using Eosin Y embedded in a polymer layer atop of the working electrode to generate a reproducible current triggered by laser illumination. Chronoamperometric measurements using the DNA-templated silver nanoclusters revealed a small but measurable current suggesting production of singlet oxygen by AgNCs@DNA. The implications of AgNCs being type II photosensitizers could be very significant, with the most obvious potential applications being in photodynamic therapy (PDT) and utilizing AgNCs as antibacterial agents.