Fabrication of 3D-printed thyme and cinnamon essential oils in γ-cyclodextrin encapsulates/sodium alginate-methylcellulose antimicrobial films with a core-shell structure

In this work, we report the encapsulation of thyme and cinnamon essential oils in gamma-cyclodextrin (GCD) wall material and thereafter assess their properties so that they can be used in developing hydrogel bioink suitable for 3D printing of antimicrobial films. Encapsulation efficacy above 90 % demonstrated inhibitory and bactericidal activities of encapsulated oils against Listeria monocytogenes and Salmonella Typherium. A customized core and shell film was fabricated using GCD/EO as a core layer and selected hydrocolloid blends as the shell layer by a coaxial 3D printing process. An apparent viscosity below 100 Pa.s facilitates the printing of the hydrogel in good shape. The developed films were characterized for their printability and microstructural properties. The incorporation of cross-linkers enhances the mechanical and optical properties of printed films. This work guides the selection of GCD to encapsulate thyme and cinnamon essential oils as antimicrobial agents to inhibit pathogens in the developed films.