Antimicrobial modification of polypropylene films by photograft and layered double hydroxides assembly

Providing antimicrobial (AM) properties to polypropylene (PP) films is an appealing strategy for food packaging and biomedical areas. In this study, PP-based platforms with AM activity were obtained by the incorporation of layered double hydroxides (LDH) nanoparticles, intercalated with antimicrobial drugs (AMD), either nalidixate (Nal−) or benzoate (Bz−), to polyacrylate (PAA)-photografted PP films (PP-g-PAA/LDH-AMD). The assembly mechanism was explored, and the composition, morphological and interfacial properties of the obtained platforms were determined. Finally, the AM activity was assayed against Staphylococcus aureus and Escherichia coli strains. LDH-AMD were successfully incorporated to the platforms by electrostatic interactions with the carboxylate groups of the photografted PAA chains and they were mainly located in the outer region of the PAA layer. This incorporation was first produced at grooves and pits of this surface layer, and then spread by aggregation of the incoming LDH-AMD particles, which increased the surface roughness of PP-g-PAA/LDH-AMD platforms. These showed significant AM activity due to their roughness, the high surface AMD concentration and the positive charge of LDH-AMD particles. Thus, Nal-incorporating platforms presented a high bactericidal effect on the proliferation of both bacterial strains. On the other hand, Bz-loaded platform slightly delayed the bacterial growth of S. aureus.