Poly (epsilon-lysine) dendrons and nucleic acids complexes for non-viral delivery of bacteriophage DNA into bacterial cells

Phage therapy has been advocated as an alternative to antibiotics in the treatment of bacterial infections. However, this approach can be affected by batch-to-batch variability in the harvesting, isolation and storage of specie-specific bacteriophages. The present paper presents the development of synthetic nanostructured carriers that can form complexes with isolated bacteriophage DNA, while ensuring the penetration of the carrier through bacterial wall and membrane. The complexation capability of these poly(epsilon-lysine) dendrons with bacteriophage DNA was tested by mixing the hyperbranched molecules at various charge ratios (132:1 to 0.06:1 of positively charged carriers to negatively charged DNA). These electrostatic complexes were assessed by gel retardation, ethidium bromide displacement assay and transmission electron microscopy. The self-assembly of poly(epsilon-lysine) dendrons with the nucleic acids led to charge ratio-dependent electrostatic complexes. Transfection of both complexed and naked DNA in Proteus mirabilis bacteria demonstrated that the viral DNA maintained its replicative ability with the formation of whole viral particles. Additionally, the dendron’s cytotoxicity was assayed by lactate dehydrogenase (LDH) release and 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) reduction assays. In both assays, 15% cytotoxicity and even lower (6%) necrotic effects were observed by MTT and LDH respectively. Overall, these findings demonstrate that it is possible to complex bacteriophage DNA with poly(epsilon-lysine) dendrons, of three branching generations (Gen3K), and suggests that Gen3K has the potential to be used as a reliable alternative to antibiotics.