Research published in cosmetics Following recent concerns regarding the safety of this ingredient, we tested the stability and skin permeability of two types of zinc oxide. The authors found that both types of zinc oxide they tested did not penetrate into the deepest layers of the skin.
The authors used 20% coated and 20% uncoated zinc oxide nanoparticles. Penetration was assessed by confocal laser microscopy.
Sunscreen
There are two types of sunscreens: physical sunscreens that use inorganic filters and chemical sunscreens that use organic filters. Only zinc oxide and titanium dioxide are approved for use as physical sunscreens that reflect or scatter UV rays. Alternative organic filter sunscreens often have poor spread and other cosmetic concerns.
The use of nanoparticle formation creates transparent sunscreen formulations, which is desirable for most consumers. However, in previous studies, zinc oxide nanoparticles had a more negative effect on keratinocytes than titanium dioxide. These effects include disruption of mitochondrial function, generation of reactive oxygen species, and oxidative DNA damage, along with the potential for genotoxicity within epidermal cells.
It’s worth noting that most studies have analyzed commercially available sunscreens, rather than the main ingredients, so there is uncertainty as to which ingredients are causing the problem. The authors of this study created a simple sunscreen formulation to test zinc oxide itself, rather than other active or inactive ingredients found in sunscreens.
research result
The coated zinc oxide formulation accumulated in the skin grooves, whereas the uncoated one did not. Both formulations were found around the hair and within the hair follicle. “Coated ZnOn nanoparticles were incorporated into the formulation and accumulated in grooves and hair follicles, but were not found within keratinocytes, suggesting that they did not penetrate the epidermis where they could survive. “,” the authors write.
Regarding UVA/UVB radiation absorption, the coated nanoparticle zinc oxide formulation showed better absorption than the uncoated one.
The authors found that small-sized nanoparticles were present in both coated and uncoated samples, and that “these nanoparticles can be taken up by cells and cause cell damage.” .
After 12 hours, there were no signs of inflammation, but the authors note that penetration may have been underestimated with the uncoated zinc oxide formulation. “The increase in reflectance of skin treated with formulations containing coated ZnOn was observed only in skin grooves and hair follicles, but not within keratinocytes. This is because the nanoparticles did not enter the cells. It may suggest that.”
This study used one application of the formula. Daily use can increase zinc in the skin, which may pose safety concerns. The authors recommend that biochemical markers of oxidative stress as well as inflammation should be tested for long-term use.
sauce:
cosmetics 2024, 11(1), 6; https://doi.org/10.3390/cosmetics11010006
“Development of topical formulations containing 20% coated and uncoated zinc oxide nanoparticles: Stability and permeability evaluation by reflectance confocal laser microscopy”
Author: Assis Dias Alves, G., et al.
