In vivo confocal Raman spectroscopy investigation of glabridin liposomes dermal penetration process in human skin

Encapsulating glabridin with liposome technology can contribute to the bioavailability and application in cosmetic formulations. At the same time, the small particle size of liposomes makes it feasible to penetrate the stratum corneum and enhance the dermal delivery of glabridin. Confocal Raman spectroscopy (CRS) can be employed to monitor the dermal penetration of cosmetic actives for topical applications. The method of CRS allows qualitatively and semi-quantitatively in vivo analysis of cosmetic actives based on the position and intensity of peaks in the Raman spectrum. In this work, CRS was used to evaluate epidermal penetration of glabridin and glabridin-containing liposome components. First, glabridin liposomes (GL), glabridin liposome essence (GLE), and glabridin essence (GE) were evenly applied on the forearms of six randomly-selected volunteers. Then, in vivo dermal penetration and of delivery mechanism of glabridin was clinically assessed at 0.5 h and 2 h with the non-invasive devices, confocal Raman spectrometer. The findings indicated that the glabridin transported by liposomes could penetrate the stratum corneum and reach deep layers of human skin, while the content of penetrated glabridin increased with time. Compared to the penetration of GLE and GE through the skin, it was found that the dermal penetration of liposome-encapsulated glabridin in the essence dosage form was 3.8 times higher than that of unencapsulated glabridin. From qualitative and semi-quantitative perspectives, it was demonstrated that glabridin liposomes have good skin permeability and a gradual release effect and the liposome encapsulation can efficiently enhance the poor dermal absorption and bioavailability of glabridin. We believe this in vivo confocal Raman spectroscopy research is benefit for revealing the permeability of glabridin and liposome formulations in cosmetics.