In recent years, a common strategy, to obtain more uniform and controlled synthesis of polyelectrolytes multi-layers (PEMs), relies on a previous polyethylenimine (PEI) coating of the substrate surface. PEI is a synthetic cat-ionic... more
In recent years, a common strategy, to obtain more uniform and controlled synthesis of polyelectrolytes multi-layers (PEMs), relies on a previous polyethylenimine (PEI) coating of the substrate surface. PEI is a synthetic cat-ionic polymer which provides a positive charge distribution on the materials to be covered with PEMs. Despite being an important step, this pre-layer deposition is frequently overlooked and no comprehensive characterizations or deep discussions are reported in literature. In that sense, this work reports on the synthesis of a typical PEI film that works as a precursor for PEMs, and its detailed physicochemical characterization. As many PEMs are produced for antibacterial and biomedical applications, the cytotoxicity of the film was also tested using fibro-blasts, and its antibacterial activity was studied using Staphylococcus aureus and Pseudomonas aeruginosa. Our results present the formation of an ultra-thin film of PEI with a thickness around 3.5 nm, and with a significant percent of NH 3 + (35% of the total amount of N) in its chemical structure; NH 3 + is a key chemical group because it is considered an important bacterial killer agent. The film was stable and did not present important cytotoxic effect for fibroblasts up to 7 days, contrary to other reports. Finally, the PEI film showed high antibacterial activity against the S. aureus strain: reductions in cell density were higher than 95% up to 24 h.
