Preparation and Characterization of GX-50 and Vitamin C Co-encapsulated Microcapsules by a Water-in-Oil-in-Water (W₁/O/W₂) Double Emulsion–Complex Coacervation Method

Abstract

Co-encapsulated xanthoxylin (GX-50) and vitamin C (Vc) microcapsules (GX-50-Vc-M) were prepared by the combination of a water-in-oil-in-water (W1/O/W2) double emulsion with complex coacervation. The W1/O/W2 double emulsion was prepared by two-step emulsification, and it has a uniform particle size of 8.388 μm and high encapsulation efficiencies of GX-50 (85.95%) and Vc (67.35%) under optimized process conditions. Complex coacervation occurs at pHs 4.0–4.7, which has the highest encapsulation efficiency of GX-50 and Vc at pH 4.5. The complex coacervate with tannic acid solidifying (namely, wet microcapsules) has better mechanical properties and also enhances the ability of co-encapsulation of active ingredients. The resulting microcapsules by freeze-drying of wet microcapsules were characterized by UV–vis absorbance spectroscopy (UV–vis), Fourier infrared spectroscopy (FI-IR), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), X-ray diffraction (XRD), 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging, and in vitro permeation measurements. Under optimal conditions, the encapsulation efficiency and drug loading of GX-50-Vc-M for GX-50 and Vc are, respectively, 78.38 ± 0.51 and 59.34 ± 0.56%, and 35.6 ± 0.68 and 29.8 ± 0.92%. A slight shift in the FTIR peak between single GX-50 or Vc and GX-50-Vc-M confirmed the successful co-encapsulation of GX-50 and Vc in microcapsules. GX-50-Vc-M has bridged irregular spherical aggregates, while GX-50 and Vc are, respectively, encapsulated in hydrophobic and hydrophilic cavities of microcapsules in an amorphous dissolved state. GX-50-Vc-M has the highest DPPH· radical scavenging rate of 62.51%, and the scavenging process of GX-50-Vc-M on DPPH· radicals is more in line with the pseudo-second-order kinetic equation model. Moreover, the in vitro permeation of GX-50 and Vc in GX-50-Vc-M can reach maximum values of 40 and 60%, respectively. This concludes that GX-50-Vc-M is a promising delivery system for the penetration of the antioxidant into the deeper layers of the skin for the antioxidant effect.

Lecithin/Cholesterol/Tween 80 Liposomes for Co-Encapsulation of Vitamin C and Xanthoxylin

“…The results indicate that although the co-encapsulated L-Vc-GX-50 liposomes do not have a synergistic effect, they have higher antioxidant capacity than single encapsulated L-GX-50 or L-Vc liposomes, which are consistent with our previous research on co-encapsulated GX-50 and Vc microcapsules by a water-in-oil-in-water (W 1 /O/ W 2 ) double emulsion−complex coacervation method. 32 3.5. Determination of Tyrosinase Activity Inhibition.…”

“…Therefore, it is difficult to directly apply them in cosmetic formulation. Moreover, studies have shown that co-encapsulation can improve the EE of another active ingredient, especially hydrophilic active ingredient. , Furthermore, the popular functional cosmetics often need a reasonable combination of multiple active ingredients to achieve multiple effects…”

“…However, there are few reports on the encapsulation of xanthoxylin (GX-50). 32 Besides, vitamin C (Vc), one of the common natural water-soluble antioxidants, not only can clear the free radicals in the human body but also can inhibit tyrosinase activity and help the reduction of dopachrome tyrosine into an intermediate of melanin, thereby reducing and inhibiting the production of melanin and inhibiting peroxidase. 45 Therefore, it is widely used in antioxidant, antiaging, and whitening cosmetics.…”

“…Moreover, studies have shown that co-encapsulation can improve the EE of another active ingredient, especially hydrophilic active ingredient. 32,46 Furthermore, the popular functional cosmetics often need a reasonable combination of multiple active ingredients to achieve multiple effects. 37 Therefore, in this study, considering the shortcomings of Vc and GX-50 and actual or potential application in cosmetics, the two ingredients were selected to be co-encapsulated in liposomes.…”

“…Colloidal delivery systems have aroused great interest due to their widespread applications in fields such as pharmaceutics, − food, − and cosmetics. − They are considered as effective means of solving some shortcomings of active ingredients, such as insolubility, instability, incompatibility, irritation, and rapid release. So far, several types of colloidal delivery systems, such as liposomes, ,,− niosomes, , double emulsions, − coacervates, − and microcapsules, − have been developed, whose amphiphilic structure can encapsulate hydrophobic active ingredients in hydrophobic cavities, or encapsulate hydrophilic active ingredients in hydrophilic cavities, or simultaneously encapsulate hydrophobic and hydrophilic active ingredients in hydrophobic and hydrophilic cavities, respectively. Among them, liposomes have significant advantages in encapsulating active ingredients in cosmetics.…”