Controlled release mechanism of thymol loaded into mesoporous silica nanoparticles for active packaging films

In order to overcome the poor water solubility and instability of thymol to enhance its bioavailability, mesoporous silica nanoparticles (MSNPs: SBA-15, SBA-16 and MCM-41) with different pore structures were developed using solution-gel method to carry and release thymol. The N2 adsorption-desorption test showed thymol-loaded MSNPs contained significantly low surface areas, pore sizes and pore volumes. When the ratio of thymol to MSNPs was 3:1, the loading capacity (LC) of MSNPs reached the highest (SBA-15: 35.20%, SBA-16: 30.84%, and MCM-41: 44.23%). The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and microstructure characterization confirmed that thymol encapsulation process was successful. TGA results showed that the encapsulation of MSNPs improved thymol stability. The zeta-potential results confirmed that thymol loading increased the intermolecular repulsion of thymol-loaded MSNPs, which was beneficial to its dispersibility in the film. Additionally, thymol release experiment revealed a sustainable release behavior of thymol for MSNPs within 10 d. The release mechanism was adjusted according to the Korsmeyer-Peppas model, which showed thymol obeyed Fickian diffusion process. Notably, both thymol-loaded MSNPs and thymol-loaded MSNPs/potato starch films showed a remarkable antimicrobial efficiency against S. aureus. Therefore, thymolloaded MSNPs provide feasible guidelines for the development of active packaging films and the on-demand release of active substances.