Biophysical and Biological Tools to Better Characterize the Stability, Safety and Efficacy of a Cosmeceutical for Acne-Prone Skin

Hair Follicle-Targeted Delivery of Azelaic Acid Micro/Nanocrystals Promote the Treatment of Acne Vulgaris

Purpose

Acne vulgaris is a chronic inflammatory skin disorder centered on hair follicles, making hair follicle-targeted delivery of anti-acne drugs a promising option for acne treatment. However, current researches have only focused on the delivering to healthy hair follicles, which are intrinsically different from pathologically clogged hair follicles in acne vulgaris.

Patients and Methods

Azelaic acid (AZA) micro/nanocrystals with different particle sizes were prepared by wet media milling or high-pressure homogenization. An experiment on AZA micro/nanocrystals delivering to healthy hair follicles was carried out, with and without the use of physical enhancement techniques. More importantly, it innovatively designed an experiment, which could reveal the ability of AZA micro/nanocrystals to penetrate the constructed clogged hair follicles. The anti-inflammatory and antibacterial effects of AZA micro/nanocrystals were evaluated in vitro using a RAW264.7 cell model stimulated by lipopolysaccharide and a Cutibacterium acnes model. Finally, both the anti-acne effects and skin safety of AZA micro/nanocrystals and commercial products were compared in vivo.

Results

In comparison to commercial products, 200 nm and 500 nm AZA micro/nanocrystals exhibited an increased capacity to target hair follicles. In the combination group of AZA micro/nanocrystals and ultrasound, the ability to penetrate hair follicles was further remarkably enhanced (ER value up to 9.6). However, toward the clogged hair follicles, AZA micro/nanocrystals cannot easily penetrate into by themselves. Only with the help of 1% salicylic acid, AZA micro/nanocrystals had a great potential to penetrate clogged hair follicle. It was also shown that AZA micro/nanocrystals had anti-inflammatory and antibacterial effects by inhibiting pro-inflammatory factors and Cutibacterium acnes. Compared with commercial products, the combination of AZA micro/nanocrystals and ultrasound exhibited an obvious advantage in both skin safety and in vivo anti-acne therapeutic efficacy.

Conclusion

Hair follicle-targeted delivery of AZA micro/nanocrystals provided a satisfactory alternative in promoting the treatment of acne vulgaris.

Effect of Aqueous Extracts of Quercus resinosa on the Mechanical Behavior of Bigels

Quercus resinosa leaves are rich in polyphenol compounds, however, they are unstable to several chemical and physical factors that limit their activity. Several methods have been developed to solve such problems, among which bigels can be mentioned and obtained using hydrogels and oleogels. The mechanical characterization of this type of materials is by using rheological methods. Although the use of these methods is well documented, the Carreau-Yasuda model has been little used to evaluate the effect of polyphenols on the mechanical behavior of bigels. Therefore, bigels were obtained from hydrogels (guar gum/xanthan gum, 0.5/0.5% w/v) and oleogels (sesame oil/sorbitan monostearate 10% w/w). Micrographs, linear viscoelasticity range, frequency sweep, and single shear tests were performed. The data were analyzed using ANOVA and Tukey test (p < 0.05); micrographs showed linear relationship between polyphenols concentration and droplet size. Liquid fraction of bigels showed a pseudoplastic behavior, while the parameters of Carreau-Yasuda model showed that the highest value of the complex viscosity at zero shear was at the lowest concentration of extract; the relaxation time presented the lowest value at higher concentrations of extracts. These results indicate that the presence of polyphenols modifyes the mechanical behavior of bigels.