TFOS Lifestyle: Impact of cosmetics on the ocular surface

In this report the use of eye cosmetic products and procedures and how this represents a lifestyle challenge that may exacerbate or promote the development of ocular surface and adnexal disease is discussed. Multiple aspects of eye cosmetics are addressed, including their history and market value, psychological and social impacts, possible problems associated with cosmetic ingredients, products, and procedures, and regulations for eye cosmetic use. In addition, a systematic review that critically appraises randomized controlled trial evidence concerning the ocular effects of eyelash growth products is included. The findings of this systematic review highlight the evidence gaps and indicate future directions for research to focus on ocular surface outcomes associated with eyelash growth products.

Solubility of Foreign Molecules in Stratum Corneum Brick and Mortar Structure

The barrier function of the skin is mainly assured by its outermost layer, stratum corneum (SC). One key aspect in predicting dermal drug delivery and in safety assessment of skin exposure to chemicals is the need to determine the amount of chemical that is taken up into the SC. We here present a strategy that allows for direct measures of the amount of various solid chemicals that can be dissolved in the SC in any environmental relative humidity (RH). A main advantage of the presented method is that it distinguishes between molecules that are dissolved within the SC and molecules that are not dissolved but might be present at, for example, the skin surface. In addition, the method allows for studies of uptake of hydrophobic chemicals without the need to use organic solvents. The strategy relies on the differences in the molecular properties of the added molecules in the dissolved and the excess states, employing detection methods that act as a dynamic filter to spot only one of the fractions, either the dissolved molecules or the excess solid molecules. By measuring the solubility in SC and delipidized SC at the same RHs, the same method can be used to estimate the distribution of the added chemical between the extracellular lipids and corneocytes at different hydration conditions. The solubility in porcine SC is shown to vary with hydration, which has implications for the molecular uptake and transport across the skin. The findings highlight the importance of assessing the chemical uptake at hydration conditions relevant to the specific applications. The methodology presented in this study can also be generalized to study the solubility and partitioning of chemicals in other heterogeneous materials with complex composition and structure.

Clinical efficacy and safety of nano-microneedle-assisted phenylethyl resorcinol for the treatment of infraorbital dark circles

BACKGROUND

Infraorbital dark circles (DC) are defined as a symptom that presents darkness under infraorbital eyelids. The objective of this study was to evaluate the efficacy and safety of nano-microneedle-assisted phenylethyl resorcinol (PR) for the treatment of infraorbital dark circles.

METHODS

Twenty female participants were randomized to two groups. In the experimental group (group E), participants received topical PR gel under the left orbit once a day and topical plus nano-microneedle-assisted PR gel under the right orbit twice a week. In the control group (group C), participants were treated with gel without PR. Melanin index (MI) and erythema index (EI) were measured before the session (T0), 4 and 8 weeks during the treatment session (T4, T8), and 1 and 2 months after the last session (T12, T16). The global assessment was performed by a blinded dermatologist.

RESULTS

The mean value of MI in group E was significantly lower than the baseline at T8 (P < .05), and the right side decreased more significantly than the left side (P < .05). However, there was no difference of MI before and after treatment in group C (P > .05). There was no big difference of the mean EI between the two sides (P > .05). The treatment was well tolerated, and no serious adverse effects were reported.

CONCLUSION

PR combined with nano-microneedle could be an effective and safe method for infraorbital DC.

Characterization and topical delivery of phenylethyl resorcinol

OBJECTIVE

Phenylethyl resorcinol (PR) has been used widely in the personal care industry as a novel skin lightening ingredient. Surprisingly, there is only limited information describing the physicochemical properties of this active. Therefore, the primary objective of this study was to perform a comprehensive characterization of PR. A secondary objective was to investigate the delivery of this molecule to mammalian skin.

METHODS

Phenylethyl resorcinol was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR). A new high-performance liquid chromatographic (HPLC) method for analysis of PR was developed and validated. The log P (octanol water partition coefficient), value, solubility and short-term stability of PR in a series of vehicles were also determined using HPLC. The evaporation of the selected vehicles was examined using dynamic vapour sorption (DVS). The permeation profiles of PR were investigated under finite dose conditions in porcine and human skin.

RESULTS

The melting point of PR was determined to be 79.13 °C and the measured log P (octanol water partition coefficient) at 21 °C was 3.35 ± 0.03. The linearity of the HPLC analytical method was confirmed with an r² value of 0.99. Accuracy of the method was evaluated by average recovery rates at three tested concentrations, and the values ranged from 99 to 106%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.19 and 0.57 μg mL^-1 , respectively. The solubility of PR in PG, DMI, glycerol was within the range of 367 to 877 mg mL^-1 . The stability of PR in tested solvents was also confirmed by the 72 h stability studies. From the DVS studies, 70-125% of applied formulations were recovered at 24 h. The permeation through porcine skin at 24 h ranged from 4 to 13 μg cm^-2 , while the corresponding amounts of PR delivered through human skin were 2 to 10 μg cm^-2 .

CONCLUSION

The physicochemical properties of PR confirm it is suitable for dermal delivery. In this study, propylene glycol was the most promising vehicle for PR delivery to human skin. Future work will expand the range of vehicles studied and explore the percutaneous absorption from more complex formulations.

Discovery of new depigmenting compounds and their efficacy to treat hyperpigmentation: Evidence from in vitro study

Human skin pigmentation is a result of constitutive and facultative pigmentation. Facultative pigmentation is frequently stimulated by UV radiation, pharmacologic drugs, and hormones whereby leads to the development of abnormal skin hyperpigmentation. To date, many state-of-art depigmenting compounds have been studied using in vitro model to treat hyperpigmentation problems for cosmetic dermatological applications; little attention has been made to compare the effectiveness of these depigmenting compounds and their mode of actions. In this present article, new and recent depigmenting compounds, their melanogenic pathway targets, and modes of action are reviewed. This article compares the effectiveness of these new depigmenting compounds to modulate several melanogenesis-regulatory enzymes and proteins such as tyrosinase (TYR), TYR-related protein-1 (TRP1), TYR-related protein-2 (TRP2), microphthalmia-associated transcription factor (MITF), extracellular signal-regulated kinase (ERK) and N-terminal kinases (JNK) and mitogen-activated protein kinase p38 (p38 MAPK). Other evidences from in vitro assays such as inhibition on melanosomal transfer, proteasomes, nitric oxide, and inflammation-induced melanogenesis are also highlighted. This article also reviews analytical techniques in different assays performed using in vitro model as well as their advantages and limitations. This article also provides an insight on recent finding and re-examination of some protocols as well as their effectiveness and reliability in the evaluation of depigmenting compounds. Evidence and support from related patents are also incorporated in this present article to give an overview on current patented technology, latest trends, and intellectual values of some depigmenting compounds and protocols, which are rarely highlighted in the literatures.

Preparation of alpha-bisabolol and phenylethyl resorcinol/TiO2 hybrid composites for potential applications in cosmetics

OBJECTIVE

Bifunctional alpha-bisabolol and phenylethyl resorcinol/TiO2 hybrids were prepared to apply in cosmetic fields, particularly in anti-ageing and hyperpigmentation treatment. The synergistic effect of combined antioxidant and UV filtering properties was achieved through functionalization of TiO2 particles with skin-lightening materials such as alpha-bisabolol and phenylethyl resorcinol.

METHODS

TiO2 microspheres with a diameter of about 1 μm were synthesized through surfactant-assisted sol-gel method for use as supporting materials in the formation of hybrid composites. Carboxylation treatment was performed for surface modification of the TiO2 surface with carboxyl groups as chemical binders. Esterification reaction between carboxyl groups of carboxylated TiO2 and hydroxyl groups of alpha-bisabolol or phenylethyl resorcinol was performed. The hybrids were characterized using various techniques such as FE-SEM, DLS, EDS, ATR-FTIR, XPS and TGA. For application of prepared TiO2 composites in the field of cosmetics, the anti-radicular antioxidant abilities were evaluated using ABTS and DPPH colorimetric antioxidant assay.

RESULTS

Organic/inorganic hybrid composites were successfully formed using esterification reaction between the carboxyl groups at TiO2 surface and the hydroxyl groups of the skin-lightening materials. The results demonstrate that both functionalized microspheres show scavenging ability towards the ABTS(•) and DPPH(•) radicals. Specifically, the phenylethyl resorcinol/TiO2 composites exhibited the highest antioxidant ability among the prepared samples owing to the presence of phenolic groups to scavenge free radicals.

CONCLUSION

Using this strategy, it could be possible to prepare not only inorganic UV filter but also hybrid organic/inorganic materials with multifunctions and advantages which would be in a great demand for cosmetic applications.

Follow-up of solar lentigo depigmentation with a retinaldehyde-based cream by clinical evaluation and calibrated colour imaging

BACKGROUND AND OBJECTIVE

To assess an objective method evaluating the effects of a retinaldehyde-based cream (RA-cream) on solar lentigines; 29 women randomly applied RA-cream on lentigines of one hand and a control cream on the other, once daily for 3 months.

METHODS

A specific method enabling a reliable visualisation of the lesions was proposed, using high-magnification colour-calibrated camera imaging. Assessment was performed using clinical evaluation by Physician Global Assessment score and image analysis. Luminance determination on the numeric images was performed either on the basis of 5 independent expert's consensus borders or probability map analysis via an algorithm automatically detecting the pigmented area.

RESULTS

Both image analysis methods showed a similar lightening of ΔL* = 2 after a 3-month treatment by RA-cream, in agreement with single-blind clinical evaluation.

CONCLUSION

High-magnification colour-calibrated camera imaging combined with probability map analysis is a fast and precise method to follow lentigo depigmentation.