Last year, Kao researchers developed a “Fine Fiber” technology method with
 direct spraying that creates a light, soft and natural layered
 ultra-thin membrane on the skin surface that is composed of
 sub-micron sized super-fine fibers. Recently, Kao’s Skincare
 Research Laboratory and Analytical Science Laboratory focused on technology used to create a membrane with moisture permeability¹ formed by a formula to control 
water evaporation on the surface of skin. Test results 
showed that control of water evaporation on skin is related 
to the expression of proteins, the raw materials of the stratum corneum, which are associated with a healthy skin condition.
 

The findings of this study were presented at the 25th IFSCC Conference in Milan, Italy. In addition, the results were made public atthe 44th Annual Meeting of the Japan Cosmetic Society in Tokyo, Japan in June, and the 2019 Academic Meeting of the Japan Proteome Society in Miyazaki Prefecture, Japan in July. 
 
The stratum corneum in the outermost skin layer has a barrier function that is important for maintaining homeostasis of the skin, as it acts to prevent external stimulatory substance invasion and control water evaporation. However, it is not uncommon for the barrier function of the stratum corneum to decline as an effect of environmental factors as well as aging, consequently causing deterioration in physical appearance and beauty. Kao researchers are trying to find solutions that complement the function of the stratum corneum, as current formulas have shown insufficient performance in regard to uniformity and durability.
The fine fiber technology developed by Kao forms an ultra-thin layered membrane consisting of fine fibers on the skin surface by direct spraying of a specialized polymer solution through a small-sized applicator nozzle developed exclusively for this use. The ultra-thin membrane is formed with interwoven thin fibers smaller than 1μm in diameter, and characterized by lightness, softness and a high capillary force.²  Use of this fine fiber membrane in combination with a liquid formula demonstrated a performance capability of quick and even distribution of that combined formulation throughout the application area, and then it remained firmly held by the entire membrane.



Moisture Permeability of Membrane Formed by Combination of Fine Fibers and Formula 


For wound treatment, a “moist healing” technique is widely used, in which the wound is treated via an artificially moisturized environment, thus taking advantage of the self-healing ability of the body. Inspired by related findings, Kao investigated methods to maintain a moderate hydric environment on the skin surface for enhancing skin improvement. Results showed that application of the high capillary force of fine fibers improved the uniformity and durability of membranes applied to skin by use of a specially developed formulation. Furthermore, attention was given to control of water evaporation from the skin by the formula in combination with the fine fibers. In that regard, moisture permeation characteristics were compared among different preparations; namely, conventional formula alone, fine fibers alone and fine fibers plus formula.

 
Membranes formed by use of the conventional formula showed high moisture permeability as fine spaces were present. Accordingly, the control of water evaporation was limited. Similarly, those formed by use of the fine fiber alone showed porous spaces in the layered membrane composed of fine fibers and moisture permeability that was not considerably different from that of membranes formed with the conventional formula.

 
In contrast, when the fine fiber membrane was used in combination with the moisturizer formula, even spreading caused by the capillary force of the fine fibers to fill the fine spaces was noted, which lowered measured moisture permeability as compared to that of the conventional formula and provided suppression of moisture evaporation from the skin surface. Results of repeated experiments confirmed that moisture permeability could be controlled by the composition of the formula. Furthermore, researchers considered that the water evaporation suppressive effect caused by control of moisture permeation may have a longer effective period with the fine fiber plus formula application, as the produced membrane was found to possess greater adhesion strength in comparison to that formed by the conventional formula. 


Effects of Fine Fiber Plus Formula


Forty-five women in their 30s and 40s with dry skin or awareness of skin dryness were enrolled for a two-week application test using Kao’s moisturizing formula designed to control water evaporation without causing damage to the structure of the fine fiber membrane. They were divided into two groups; those who applied the formula alone and subjects who applied the fine fibers along with use of the formula.
 

For verifying the condition inside the stratum corneum to detect changes within a short period, Kao developed a time-series proteome analytical method with application of proteome analysis using mass spectrometry. Expression of 245 different proteins in the stratum corneum was comprehensively analyzed before and after application. Furthermore, the skin surface appearance was observed in each subject.


Results


Time-series proteome analysis—Expression of proteins in stratum corneum
Expression of proteins in the stratum corneum was analyzed before the start of continuous applications, and then again 7 and 14 days later. In the subject group that applied the fine fiber plus water evaporation-control formula, there was increased expression of a greater number of proteins within a short period as compared to that in the group that applied the formula alone.
 Notably, in the group with the combined formula, proteins (CAPN1, BLMH) that promote production of raw materials for natural moisturizing factor (NMF) showed a greater increase as compared to the formula alone group. Additionally, other proteins (GGCT, HAL, ARG1) known to promote the production of raw materials for NMF had a greater increase after 14 days of continuous application as compared to after 7 days. Our findings also confirmed that expression of the protein (SBSN) involved in promotion of production of lamellar granules,³ which are deeply involved in the barrier function of skin, was specifically increased.

 
Skin care effects—In both the fine fiber plus water evaporation-control formula and formula alone groups, water content in the skin showed a significant increase from the third day of application in comparison to that just prior to starting the applications. As for skin appearance, brightness and gloss were significantly improved within three days of starting applications in the combined use group, earlier as compared to the group with formula alone.

 
Inspired by moist-healing methods widely used for wound treatment, Kao researchers studied application of a formula combined with fine fibers for water evaporation control. Results showed that moisture permeability of the stratum corneum could be controlled by use of this novel combination formula. Furthermore, researchers observed increased expression of several different proteins that provide favorable skin conditions in the stratum corneum within a short period of time, along with early improvements in dry skin appearance. Based on these findings, Kao researchers intend to develop products with an added dimension gained by applying this fine fiber technology. In addition, they will continue to pursue technological developments for application in therapeutic settings to contribute to the needs of society.
 

 
References

1 Amount of vapor permeation through membrane fibers. Higher moisture permeability = easier escape of water vapor.

2 Force caused by a narrow space in an object to draw in fluid.
 
3 Granules containing enzymes indispensable for ceramide and normal skin metabolism.