Construction of Terpinen-4-ol Encapsulation System Based on β-Cyclodextrin-based Metal-organic Framework

In order to improve the hydrophobicity and volatility of terpinen-4-ol and extend its duration of action, β-cyclodextrin-based metal-organic framework (β-CD-MOF) was first prepared by the modified vapor diffusion method, and then terpinen-4-ol was encapsulated with the β-CD-MOF to prepare a terpinen-4-ol/β-CD-MOF inclusion complex by the solvent incubation method. The mass ratio of the prepared β-CD-MOF or β-CD used as the control to terpinen-4-ol was optimized for encapsulation. The morphological characteristics, spectral absorption properties and thermogravimetric characterisation of the terpinen-4-ol/β-CD-MOF complex were analyzed. Through in vitro bacteriostatic assays, the inhibitory effects of the complex on three food-borne pathogens were determined. The results showed that the highest drug loading and encapsulation efficiency were achieved when the mass ratio of terpinen-4-ol to β-CD-MOF was 1:1, superior to the same preparation conditions using β-CD as a carrier. Scanning electron microscope (SEM) observations indicated that irregularly arranged β-CD molecules stacked together under the bridging action of K⁺, forming an orderly arranged rectangular β-CD-MOF. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis demonstrated terpinen-4-ol was successfully encapsulated in β-CD-MOF with hydrogen bond interactions between them. Thermogravimetric analysis (TGA) proved that the volatilization rate of terpinen-4-ol could be retarded when encapsulated by β-CD-MOF, extending its application temperature range from 30~160 ℃ to 30~350 ℃. In vitro antibacterial experiments showed that the terpinen-4-ol/β-CD-MOF complex exhibited long-lasting antibacterial abilities against three common cold-chain microorganisms, including Escherichia coli, Staphylococcus aureus and Listeria monocytogenes. In conclusion, encapsulating terpinen-4-ol in β-CD-MOF allows for effective preservation, providing a theoretical basis for the development of novel, green and safe antimicrobial materials for cold-chain applications.