Dual-Action Nucleic Acid Nanoparticles: Innate Immune Activation and Silver Nanocluster-Mediated Targeting of Intracellular Bacteria

Abstract

Intracellular bacterial infections, such as those caused by S. aureus, are particularly challenging to treat because pathogens reside within host cells, evading immune defenses and limiting antibiotic efficacy, subsequently promoting drug resistance. To address this, we developed immunostimulatory nucleic acid nanoparticles (NANPs) functionalized with antibacterial silver nanoclusters to enable a dual mechanism of antibacterial action. These NANPs are engineered to activate RIG-I-mediated innate immune responses, which are often bypassed by intracellular bacteria to avoid host clearance. The embedded DNA-templated and -stabilized fluorescent silver nanoclusters, composed of approximately ten silver atoms, exhibit intrinsic antibacterial activity. We systematically evaluated different architectural configurations of silver nanoclusters within NANPs and assessed their relative stabilities, immunostimulatory potentials, and effects against planktonic bacteria and biofilms. We also confirmed that enhanced host immune activation and direct antibacterial activity result in a significant reduction of intracellular S. aureus in primary murine osteoblasts, highlighting the therapeutic potential of this platform.