Impact of Various Essential Oils or Their Pure Components on the Selected Properties and Microbicidal Potential of Chitosan-Based Coatings

Novel chitosan coatings incorporating antibacterial additives, including essential oils (cinnamon bark, cinnamon leaf, and thyme) or their constituents (cinnamaldehyde, eugenol, thymol, and carvacrol), were electrophoretically deposited on titanium. The electrokinetic characteristics of the emulsions and deposition parameters were determined. The increase in additive concentration (from 2 to 10 mL/L) in the emulsion resulted in poor adhesion of the coatings to the substrate (0B according to the ASTM D3359-23 standard). The coatings contained droplets of additives scattered relatively homogeneously in the chitosan matrix. The amount and dimension of the droplets were affected by the content of the additive in the emulsion. It was found that all of the additives had an impact on chitosan, as they formed new intermolecular hydrogen bonds. The roughness and wettability of the coatings were significantly affected by the concentration of additives in the dispersed systems. In most cases, increasing the concentration of additives led to lowering the wettability of coatings and increasing their roughness. Electrochemical studies confirmed that all of the investigated coatings improved resistance to corrosion compared to that of the bare titanium substrate. The coatings had different bactericidal factors with respect to the additive used. Mostly, they acted actively against Staphylococcus aureus compared to Escherichia coli bacteria. The microbicidal activity of the coatings was strongly related to the time of incubation of the bacteria strains. Of all additives, cinnamon bark oil and (cinnamaldehyde) acted the strongest against both pathogens. All coatings had a high cytotoxicity factor against both the MG-63 and FaDu cell lines. Nevertheless, they are very promising for applications that require a high antimicrobial performance.