Cinnamon Oils and Their Main Constituents as Natural Antibacterial Agents of Sodium Alginate Coatings Electrophoretically Deposited on Austenitic Stainless Steel Substrates

Abstract A novel approach consisting of surface treatment of stainless steel substrates and a two-step electrophoretic deposition process was developed to enhance the adhesion strength of sodium alginate-based coatings. A series of different single-layer and double-layer coatings incorporated in leaf and bark cinnamon essential oils, or their main constituents, eugenol and cinnamaldehyde, were successfully deposited for the first time. The processing conditions, the chemical composition, and electrokinetic properties of the dispersed systems as well as the kinetics and mechanisms of deposition of single- and double-layer coatings were studied. The coatings obtained in a two-step process, including deposition of an intermediate sodium alginate layer and an outer oil-enriched layer, were found to exhibit the highest adhesion to the chemically treated and anodically oxidized substrates. The mechanisms of interactions between the molecules of the introduced additives and the polymer chains were proposed. The surface of the coatings exhibited high roughness and a hydrophilic character. The double-layer coatings with cinnamaldehyde had the highest bactericidal activity against S. aureus . The viability of the MG-63 and FaDu cell lines for coatings with essential oils was low. The results obtained will be useful for the further development of similar coatings to enhance the resistance to bacteria and reduce the cytotoxic response of stainless steel used for temporary bone implants.