Amphiphilic dendrimer-assisted delivery of antisense nucleic acid mimics against E. coli

The rise in antimicrobial resistance and the consequent ineffectiveness of conventional antibiotics emphasise the need for novel therapeutic strategies. Antisense nucleic acid mimics (NAMs) are emerging as promising precision therapeutic agents, inhibiting specific genes through hybridisation with selected nucleic acid targets. However, delivering NAMs into bacteria remains a significant challenge. This study explores the use of poly(amidoamine) (PAMAM) amphiphilic dendrimers (ADs) as delivery vehicles for NAMs targeting the essential acpP gene in Escherichia coli. Two ADs bearing primary amine or tertiary amine terminals, 1a and 1b, were tested for their ability to permeabilise the bacterial envelope, facilitate NAM internalisation, and enhance NAM-based antibacterial activity. Physicochemical characterisation studies, flow cytometry measurements, fluorescence and electron microscopy imaging, bacterial viability assays, and an in vivo toxicity assessment using a greater wax moth (Galleria mellonella) model were conducted. Both ADs acted as permeabilisers of the bacterial envelope and assisted in NAM internalisation and antibacterial activity. The most effective formulation, 1b combined with the peptide nucleic acid (PNA)-based NAM, achieved an 8 log₁₀ reduction in viable bacteria, with sustained activity up to 24 h against E. coli. In vivo, the most promising formulations showed no toxicity, with G. mellonella larvae maintaining overall health and no significant mortality detected for up to three days. These findings demonstrate that amphiphilic dendrimers can effectively deliver PNA-based NAMs, highlighting their potential as a novel strategy against antimicrobial-resistant pathogens.