Chiral Histidine-Modified Gold Nanoclusters Loaded into Cationic Lipid Nanoparticles for Treatment of Biofilm-associated Infections

Abstract

Antimicrobial resistance has heightened the risk of device-associated infections, in which Staphylococcus aureus (S. aureus) biofilms persist through extracellular-matrix protection and marked physiological heterogeneity. Gold nanoclusters (AuNCs) can disrupt biofilms via redox-associated stress, but limited in vivo stability and poor local retention constrain their translational potential. Here, we synthesized chiral histidine-modified AuNCs (D-, L-, and DL-AuNCs) and formulated them into mildly cationic lipid nanoparticles (AuNCs@LNP) by microfluidic assembly to enhance biofilm engagement while preserving nanocluster identity. The resulting particles were [~]100-120 nm with high gold loading and a modest charge reversal. In established S. aureus USA300 biofilms, free DL-AuNCs reduced viable burden by up to 5.6 log10 CFU/mL, suppressed metabolic activity, and increased ROS signaling. Notably, LNP encapsulation maintained bactericidal activity and further improved killing by [~]1 log10 CFU at matched Au dose, while substantially enhancing biomass removal (crystal violet residual biomass: 63.77% vs 45.17%), consistent with carrier-mediated matrix destabilization. In a subcutaneous implant infection model, a single perilesional dose of DL-AuNCs@LNP reduced implant-associated bacterial burden by 2.6 log10 CFU per implant versus PBS. These results establish a modular antibiofilm platform that couples nanocluster-driven killing with lipid-facilitated biofilm disruption and defines an efficacy-tolerability window to guide optimization of locally delivered antibiofilm nanomedicines. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=61 SRC="FIGDIR/small/707929v2_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@119134forg.highwire.dtl.DTLVardef@142e7b2org.highwire.dtl.DTLVardef@1799550org.highwire.dtl.DTLVardef@139c33a_HPS_FORMAT_FIGEXP M_FIG C_FIG