Characterizations of Antibacterial and Anti-biofilm Properties of Dendrimers G6 and G9

Dendrimers are nanosized molecules with potential antimicrobial applications. This study evaluates the antibacterial and anti-biofilm properties of two cationic dendrimers, NVX-G6 (G6) and NVX-G9 (G9), against clinically relevant bacterial pathogens. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC ₉₉ ) were determined for Escherichia coli, Pseudomonas aeruginosa , methicillin-sensitive Staphylococcus aureus (MSSA), and methicillin-resistant Staphylococcus aureus (MRSA). The synergy of dendrimers with ceftazidime and vancomycin was evaluated using checkerboard assays. Furthermore, biofilm formation inhibition assays and fluorescent microscopy were performed to assess dendrimer interactions with bacterial biofilms. The results indicate that G6 and G9 exhibit limited direct antibacterial activity at high concentrations (MIC > 1024 µg/mL) but demonstrate synergistic effects when combined with ceftazidime against E. coli and P. aeruginosa (FIC < 0.5). Notably, both dendrimers penetrated and colocalized within established biofilms, with time-dependent reductions in biomass observed after extended incubation, suggesting a role in progressive biofilm disruption rather than acute inhibition of formation, although significant biomass reduction was not observed under standard assay conditions. These findings contribute to the understanding of dendrimer-antibiotic interactions and their implications in antimicrobial and nanomedicine therapy.