Nano-complexation of ε-poly-l-lysine with DNA: Improvement of antimicrobial activity under high phosphate conditions

ε-Poly-l-lysine (PL) has high antimicrobial activity and a wide antimicrobial spectrum and is applied broadly in the food industry. However, PL may lose part of its activity in phosphate systems, which are typically used in seafood processing. To enhance antimicrobial activity under high phosphate conditions, DNA/PL nanoparticles were fabricated via the nanoprecipitation method. The DNA/PL nanoparticle size was smallest when the ethanol to water ratio was 7:1, and the mean diameter was 101 nm. UV-vis showed hypochromism and a redshift of the DNA in the presence of PL, indicating an intercalative interaction between DNA and PL. FTIR spectroscopy revealed that strong hydrogen bonds and hydrophobic interactions were involved in DNA/PL nanoparticle formation. Compared with that of PL, the antimicrobial activity of the nanoparticles against S. aureus, B. subtilis, and E. coli was enhanced. Additionally, the DNA/PL nanoparticles still retained higher antimicrobial activity in the phosphate system than free PL. The antimicrobial mechanistic analysis provided evidence that the DNA/PL nanoparticles showed high bioactivity due to cell membrane damage. This work provides a potential method to enhance the antimicrobial activity of PL under adverse conditions, which can promote the application of PL in seafood containing phosphate compounds.