Facile fabrication of tea tree oil-loaded antibacterial microcapsules by complex coacervation of sodium alginate/quaternary ammonium salt of chitosan

In this study, flavour tea tree oil (TTO)-loaded antibacterial microcapsules were developed based on the complex coacervation of sodium alginate (SA) and a quaternary ammonium salt of chitosan (HACC). The optimum preparation conditions of the TTO-loaded microcapsules determined using the response surface methodology (RSM) were as follows: a weight ratio of the core to wall material (core-wall ratio) of 1 : 1, a pH value of 6.0 and a mass concentration of CaCl2 solution of 0.6 w/v%, at which the resultant microcapsules showed the greatest actual encapsulation efficiency (EE) of 66.06% +/- 2.53%. Thereafter, the resultant microcapsules were characterized in terms of morphology, size, components and thermal stability using scanning electron microscopy (SEM), a laser particle diameter analyzer (LPDA), Fourier transform infrared spectroscopy (FTIR), and thermal gravity-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC), respectively. Furthermore, both the in vitro drug release and antimicrobial properties of the microcapsules were also assessed. The results displayed that the TTO-loaded microcapsules had a spherical shape with the particle sizes in the range from 1.91 mu m to 13.18 mu m. The microcapsules possessed outstanding performances with respect to the thermal stability, sustained release activity, antimicrobial effect and long-term inhibition activity. The release profiles of TTO from the microcapsules could be well described by the Ritger-Peppas model. Based on the above research results, the simple and environmentally-friendly microencapsulation formulation could effectively improve the stability and prolong the antimicrobial efficacy of TTO. The microcapsules may find applications in food, cosmetics and medicine.