Do urea/ammonium lactate combinations achieve better skin protection and hydration than either component alone?

Transdermal Co-Delivery of Urea and Recombinant Human Growth Hormone

BACKGROUND

Urea with super-hydrating and moisturizing properties is mainly used as an adjunctive treatment of diseases associated with dry skin. In this regard, the recombinant human growth hormone (rhGH) with rejuvenating properties is used as a base material in beauty creams. Although urea easily passes through the skin, the epidermal skin barrier restricts the passage of hGH due to its size.

OBJECTIVE

in this research, in order to solve this problem, hydroxy propyl-beta cyclodextrin (HP-β-CD) is used as a soluble chemical enhancer.

MATERIAL AND METHODS

UV and circular dichroism spectroscopy were used for the investigation of structural modification. The permeation process was studied in vitro on rat skin using vertical Franz diffusion cells. Enzyme-linked immunosorbent assay were used for rhGH activity assessment and evaluation of transdermal delivery.

RESULTS

First, due to the denaturing effects of urea on proteins its concentration was optimized to maintain biological structure and protein activity. UV spectroscopy and CD data proved that the secondary structure of rhGH is preserved in the presence of urea (0.5-2 M) and HP-β-CD, which elevates urea and rhGH permeation. Maximum permeability was observed at 120 min after sampling (1424.35 ng.ml.cm^-2), which was much higher than the control. Using a higher concentration of urea in the formulation will significantly decrease the level of rhGH delivery.

CONCLUSION

According to results, this strategy can be considered as a successful method for enhanced Co-delivery of rhGH and urea.

Influence of Excipients on Moisturizing Effect of Urea

Water is the most important molecule contained in the skin and is bound to the intracellular hygroscopic substances called natural moisturizing factors (NMF). The clinical characteristic of xerosis is rough and/or coarse skin. This anaesthetic alteration necessitates cosmetic products application. In this study, we tested the efficiency of urea incorporated into six different emulsions (O/W) and 10 different gels. Skin of 10 healthy women (20 to 45 years) was treated using 50 mg of emulsion or gel containing 5% of urea. A skin surface of 16 cm(2) was chosen in the area of the forearm. The gain in moisturizing was performed measuring the skin electrical capacity using a corneometer (Courage & Khazaka, model CM 825), one hour after treatment. Sodium carboxymethyl cellulose gel has the least moisturizing effect. On the other hand, the mixture of polyacrylamide and C13-14 isoparaffin polysorbate 85 can be a good vehicle in the treatment of skin dehydration. Adding various oils (6%) or collagen in aqueous solution does not improve the efficiency of the tested products. Moisturizing effect of gels (polyacrylamine with C13-14 isoparaffin polysorbate 85) is higher than the one of emulsions (L/H).

Einfluss eines ureahaltigen Lackes auf die Nagelqualität

BACKGROUND

Urea is a well-known humectant. The aim of our study was to evaluate the in vivo effect of 10% urea lacquer on nail quality.

METHODS

60 healthy probands with brittle nails were included in a randomized, controlled study. The nail lacquer was applied once (n=30) or twice daily (n=30) on one hand for 28 days, while the other hand served as untreated control. Assessments included clinical evaluations and bioengineering measurements.

RESULTS

Application of the nail lacquer was well-tolerated and led to a significant clinical improvement of nail surface morphology, nail plate consistency, reflection of the nail plate surface, appearance of the cuticle and the nail fold. Sonographic nail density was slightly increased. No relevant changes were found in nail thickness and transonychial water loss.

CONCLUSIONS

Nail lacquer containing urea improves the cosmetic appearance of fingernails.

Is Endogenous Glycerol a Determinant of Stratum Corneum Hydration in Humans?

Although stratum corneum (SC) hydration has been primarily of concern to the cosmetic industry, it serves an important biosensor function. In murine models, not only deiminated products of filaggrin-derived amino acids ("NMF") but also endogenous glycerol from circulation into the epidermis via aquaporin 3 channel and from triglyceride turnover in sebaceous glands (SG) are important determinants. We assessed here whether endogenous glycerol could also be linked to SC hydration in humans. SG-enriched sites are more hydrated than SG-impoverished sites, and SC hydration correlates with both sebum production and SC glycerol content, but the correlation is more significant for SC glycerol content than for sebum content. Moreover, gender-related differences in sebum content are not associated with altered SC hydration. SC hydration is also linked to SC glycerol content in SG-impoverished sites, suggesting a role for non-SG-derived (? from circulation) glycerol in SC hydration. Finally, short-term water immersion produces a parallel decline in SC hydration and SC glycerol content, with glycerol levels returning to normal over several hours. These results suggest that endogenous glycerol of both circulatory and SG origin comprises an H2O-extractable pool that influences SC hydration in humans. These results also provide a rationale for the development of glycerol-containing therapeutic moisturizers.