Microencapsulation of Citrus aurantifolia essential oil with the optimized CaCl2 crosslinker and its antibacterial study for cosmetic textiles

Abstract

A functional fabric immobilized by the microcapsules of C. aurantifolia lime essential oil (LO) was prepared and characterized. A varied amount of CaCl₂ crosslinker was optimized to coacervate LO using alginate-gelatin biopolymers and Tween 80 emulsifier. A further evaluation of the immobilized LO microcapsules for the antibacterial effect against both Gram-positive and Gram-negative bacteria was conducted. The optimized alginate/gelatin-based microcapsules were effectively crosslinked by 15% CaCl₂ with an yield, oil content (OC), and encapsulation efficiency (EE) of 39.91 ± 3.10%, 78.33 ± 7.53%, and 90.27 ± 5.84%, respectively. A spherical shape of LO microcapsules was homogeneously found with an average particle size of 1.394 μm. A first-order kinetics mechanism for the release of LO out of the microcapsules was modeled by Avrami's kinetic equation (k = 1.60 ± 3.68 × 10^-5 s^-1). The LO microcapsules demonstrated good thermal stability up to 100 °C and maintained 51.07% OC and 43.56% EE at ambient temperature for three weeks. Using a pad dry method and citric acid binder, LO microcapsules were successfully immobilized on a cloth with a % add on 30.60 ± 1.80%. The LO microcapsules and the immobilized one exhibited a moderate ZoI of bacterial growth for Gram-positive S. aureus and S. epidermidis as well as Gram-negative E. coli and K. pneumonia. Further washing test toward the functional fabric showed that the LO microcapsules incorporated into the fabric were resistant to five cycles of normal washing with a mass reduction of 22.01 ± 1.69%.

Fig. 1. Average particle size distribution of LO microcapsule crosslinked at the various amounts of CaCl₂. A 95% confidence level statistical test of significant difference was performed. One-way ANOVA's P-value of 1.000 indicates that there is no significant difference between any of the treatments.

Fig. 2. SEM micrograph of LO microcapsules crosslinked by 15% CaCl₂: magnifications of (a) 350× and (b) 500×.

Fig. 3. Spectra of FTIR of (a) gelatin, (b) sodium alginate, (c) LO, (d) coreless microcapsules, and (e) LO microcapsules.

Fig. 4. TGA thermograph of () LO and () LO microcapsules.

Fig. 5. LO release performance out of microcapsules at various amounts of crosslinkers.

Fig. 6. LO release performance out of microcapsules at various temperatures.

Fig. 7. Stability of LO microcapsules at room temperature (mean ± SD, n = 3).

Fig. 8. Reaction between alginate, citric acid, and cotton cloth.

Fig. 9. SEM micrograph of (a) a fabric without microcapsules; (b) a fabric containing microcapsules at 250× magnification; (c) a fabric containing microcapsules at 500× magnification.

Fig. 10. Washing test of the immobilized LO microcapsules (mean ± SD, n = 2).