Sponge-liked Silica Nanoporous Particles for Sustaining Release and Long-Term Antibacterial Activity of Natural Essential Oil

To improve the sustained release and long-term antibacterial activity of Chimonanthus nitens Oliv. essential oil (CEO), novel sponge-liked nanoporous silica particles (SNP) were synthesized via the soft template method, which was employed as a biocompatible carrier to prepare spong-liked nanoporous silica particles loading with CEO (CEO-SNP) through physical adsorption. The structure and properties of the samples were characterized via N2 adsorption/desorption measurements, thermogravimetry (TGA), Fourier transform infrared, SEM and TEM. The result showed that the SNP exhibited an excellent loading capability of CEO up to 76.3%. The thermal stability and release behavior of the CEO were significantly improved via the physical adsorption of the SNP materials. The release profile of CEO was in accordance with the first-order kinetic model, which meant that the release mechanism was drug Fick’s diffusion. The antibacterial evaluation results demonstrated that the CEO-SNP exhibited strong antibacterial activity against S. aureus, E. coli and P. aeruginosa. The antibacterial results have shown that the CEO-SNP could destroy the cell structure of bacteria, and result in the generation of oxidative stress and the release of nucleic acid. After storage of 30 d at 25 °C, the CEO-SNP still had the stronger antibacterial activity towards S. aureus, E. coli and P. aeruginosa in comparison with CEO. Therefore, the sponge-like silica nanoporous particles seemed to be a promising carrier for long-term stability and antibacterial delivery of CEO.