Cinnamon oil-loaded composite emulsion hydrogels with antibacterial activity prepared using concentrated emulsion templates

Cinnamon oil (CMO) has a wide variety of promising applications due to its multifunctional activity, especially excellent antibacterial activity. However, CMO is highly unstable and volatile, which clearly limit its application fields. In this work, CMO is encapsulated in composite emulsion hydrogels to solve the above issue. The CMO-loaded composite emulsion hydrogels are facilely and effectively fabricated by free radical polymerization of acrylamide in the continuous phase of oil-in-water concentrated emulsion templates. Gelatin serves as the effective polymer emulsifier to prepare the CMO-in-water concentrated emulsions. The study results display that the CMO can be effectively loaded into the hydrogel matrix. And the microstructure and mechanical properties of the composite hydrogels can be easily tuned by changing internal phase fraction of the concentrated emulsion templates. Increasing internal phase fraction leads to the increase of pore sizes and the decrease of the Young's modulus and compressive stress. Moreover, the release studies indicate that the CMO-loaded composite hydrogels display the sustained CM release profiles. Furthermore, the antibacterial assays verify that the CMO-loaded composite hydrogels demonstrate an excellent and long-term antibacterial activity against Staphylococcus aureus and Escherichia coli. All the results indicate that the CMO-loaded composite emulsion hydrogels prepared in this study can be applied as promising long-term antibacterial materials. Free radical polymerization based on concentrated emulsion templates is a promising alternative approach to fabricate antibacterial essential oil loaded composite emulsion hydrogels, which could be acted as antibacterial materials.