Study on the formation and anti-biofilm properties of cinnamon essential oil inclusion complexes by the structure of modified β-cyclodextrins

Abstract

Essential oils (EOs), which are plant-oriented anti-biofilm agents, are extensively encapsulated by cyclodextrins to overcome their aqueous solubility and chemical instability, and achieve slow release during long-term storage. However, the biological activities of EOs decreased after initial encapsulation in CDs. In this study, modified-β-cyclodextrins (β-CDs) were screened as wall materials to maintained the initial anti-biofilm effect of pure CEO. The inhibitory and bactericidal activities of CEO encapsulated in five types of β-CDs with different substituents (primary hydroxyl, maltosyl, hydroxypropyl, methyl, and carboxymethyl) against Staphylococcus aureus biofilm were evaluated. Crystal violet assay and 3D-View observations suggested that CEO and its inclusion complexes (CEO-ICs) inhibited Staphylococcus aureus biofilm formation through the inhibition of colonising spreading, exopolysaccharide synthesis, and cell surface properties. Molecular docking revealed the causes of the decrease in the anti-biofilm effect after encapsulation, and quantitative structure-activity relationship assays provided MIC and MBIC prediction equation for modified-β-cyclodextrins inclusion complexes. Maltosyl-β-CD was screened as the best wall material to retained the anti-biofilm activities as pure cinnamon essential oil in initial stage, and its inclusion complexes can effectively inhibited biofilm formation in milk. This study provides a theoretical guidance for the selection β-CDs to encapsulate CEO as plant-oriented anti-biofilm agents to inhibit bacterial biofilm formation.