Preparation and Antibacterial Properties of Nanocapsules Based on Tea Tree Oil/Octenidine·2HCl

Silica nanocapsules were synthesized in miniemulsion by using the surface of miniemulsion droplets as a template for the hydrolysis and condensation of tetraethoxysilane. In this study, we successfully used gemini emulsifier octenidine·2HCl (OCT) to encapsulate tea tree oil (TTO) in the core of silica nanocapsules (SINC-OCT/TTO). Then, we synthesized the silica nanocapsule (SINC-TTO) in the same way, in which only OCT was replaced with another emulsifier cetyltrimethylammonium chloride (CTAC). We compared the SINC-OCT/TTO with SINC-TTO in the structure and properties. Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) were used to characterize the structure of the nanocapsules. The specific surface areas and pore size of the SINCs were characterized with N₂ absorption-desorption. The hydrodynamic diameter of the capsules was evaluated by dynamic light scattering(DLS). The results showed that the content of TTO loaded in SINCs, hydrodynamic diameter, specific surface area and pore size of SINCs were controlled by the type of surfactant. The hydrodynamic diameter of the two kinds of nanocapsules were 67.36 nm and 121.7 nm, respectively, and the specific surface areas were 289 m²/g and 437 m²/g, respectively. The mass fraction of TTO in SINC-OCT /TTO (47.7%) is higher than that in SINC-TTO (33.3%). The results of fractional inhibitory concentration index showed that TTO combined with OCT had synergistic antibacterial effects on S. aureus and had accumulative antibacterial effect on E. coli. The antibacterial experiment results of nanocapsules confirmed that the antibacterial effect of SINC-OCT/TTO was much higher than that of SINC-TTO.