Estibalitz Fernández

Photodamage determination of human hair.

Sunlight on human hair causes photo-degradation. This results in bleaching due to melanin oxidation through free radicals, and induces keratin impairment. Protein degradation, tryptophan degradation, lipidic peroxidation and electron paramagnetic resonance can be used to evaluate proteic and lipidic photodecomposition and free radical formation in hair fibres subjected to antioxidant action and different UV intensities. All these methodologies have been optimised to determine protein, lipid and melanin degradation in hair subjected to different UV intensities.

Efficacy of antioxidants in human hair

Hair is exposed every day to a range of harmful effects such as sunlight, pollution, cosmetic treatments, grooming practices and cleansing. The UV components of sunlight damage human hair, causing fibre degradation. UV-B attacks the melanin pigments and the protein fractions (keratin) of hair and UV-A produces free radical/reactive oxygen species (ROS) through the interaction of endogenous photosensitizers. Hair was dyed and the efficacy of two antioxidant formulations was demonstrated after UV exposure by evaluating, surface morphology, protein and amino acid degradation, lipidic peroxidation, colour and shine changes and strength/relaxation properties. UV treatment resulted in an increase in protein and lipid degradation, changes in colour and shine and in adverse consequences for the mechanical properties. Natural antioxidants obtained from artichoke and rice applied to pretreated hair improved mechanical properties and preserved colour and shine of fibres, coating them and protecting them against UV. Furthermore, the lipidic peroxidation of the protein degradation caused by UV was reduced for some treated fibres, suggesting an improvement in fibre integrity. This was more marked in the case of the fibres treated using the artichoke extract, whereas the rice extract was better preserving shine and colour of hair fibres.

A rhenium tris-carbonyl derivative as a model molecule for incorporation into phospholipid assemblies for skin applications.

A rhenium tris-carbonyl derivative (fac-[Re(CO)3Cl(2-(1-dodecyl-1H-1,2,3,triazol-4-yl)-pyridine)]) was incorporated into phospholipid assemblies, called bicosomes, and the penetration of this molecule into skin was monitored using Fourier-transform infrared microspectroscopy (FTIR). To evaluate the capacity of bicosomes to promote the penetration of this derivative, the skin penetration of the Re(CO)3 derivative dissolved in dimethyl sulfoxide (DMSO), a typical enhancer, was also studied. Dynamic light scattering results (DLS) showed an increase in the size of the bicosomes with the incorporation of the Re(CO)3 derivative, and the FTIR microspectroscopy showed that the Re(CO)3 derivative incorporated in bicosomes penetrated deeper into the skin than when dissolved in DMSO. When this molecule was applied on the skin using the bicosomes, 60% of the Re(CO)3 derivative was retained in the stratum corneum (SC) and 40% reached the epidermis (Epi). Otherwise, the application of this molecule via DMSO resulted in 95% of the Re(CO)3 derivative being in the SC and only 5% reaching the Epi. Using a Re(CO)3 derivative with a dodecyl-chain as a model molecule, it was possible to determine the distribution of molecules with similar physicochemical characteristics in the skin using bicosomes. This fact makes these nanostructures promising vehicles for the application of lipophilic molecules inside the skin.

Lamellar body mimetic system: An up-to-down repairing strategy of the stratum corneum lipid structure

Epidermal lamellar bodies (LBs) are organelles that secrete their content, mainly lipids and enzymes, into the intercorneocyte space of the stratum corneum (SC) to form the lamellar structure of this tissue. Thus, LBs have a key role in permeability and the microbial cutaneous barrier. In this work, a complex lipid system that mimics the morphology, structure and composition of LBs has been designed. To evaluate the effect of this system on delipidized SC, in vitro experiments using porcine skin were performed. The microstructure of SC samples (native, delipidized and, delipidized after treatment) was evaluated by freeze substitution transmission electron microscopy (FSTEM) and grazing-incidence small-angle X-ray scattering (GISAXS). Delipidized SC samples showed no evidence of lipid lamellae after extraction with organic solvents. However, after treatment with the LB mimetic system, new lamellar structures between corneocytes were detected by FSTEM, and high intensity peaks and reflections were found in the GISAXS pattern. These results demonstrate a strong effect of the treatment in repairing part of the lipid lamellar structure of the SC. Accordingly, future research could extend the use of this system to repair skin barrier dysfunction.

Monitoring bicosomes containing antioxidants in normal and irradiated skin

This study evaluates the penetration of bicosome systems incorporating two different antioxidants into normal skin and skin exposed to ultraviolet-visible radiation (UV-VIS) by Fourier-transform infrared microspectroscopy (FT-IR) using synchrotron radiation. Bicosomes are phospholipid assemblies based on mixtures of discoidal lipid structures protected by spherical lipid vesicles able to incorporate different molecules. In the current work, the antioxidants incorporated in these systems were β-carotene and a Mn complex as a superoxide dismutase (SOD) mimic. Additionally, a rhenium tri-carbonyl derivative was incorporated in the bicosome systems in order to map their penetration following the tag specific carbonyl signal by FT-IR microspectroscopy. The characterization of bicosome systems using the dynamic light scattering technique (DLS) showed a modification in the size of the systems containing β-carotene (Bcβ) or MnII complex (BcMn). After skin permeation, FT-IR results indicated a higher and deeper penetration of the BcMn system than the Bcβ system into the skin. Likely, the different physicochemical properties of both antioxidants could be responsible for this effect. Moreover, the penetration of both bicosome systems in irradiated skin was lower in comparison with the normal skin. This fact could be a consequence of the alteration of water transport in the skin during the irradiation process. In conclusion, these results indicated the effectiveness of bicosome systems as skin carriers, and provide information to protect skin under radiation using antioxidants.

Bicelles and bicosomes as free radical scavengers in the skin

In the present work, β-carotene antioxidant was incorporated in two different lipid nanoaggregates, bicelles and bicosomes, and its effectiveness against free radical formation in porcine skin in vitro was determined using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin trap and Electron Paramagnetic Resonance spectroscopy (EPR). Bicelles are discoidal nanostructures formed by self-assembly of phospholipids dispersed in aqueous solution. Bicosomes emerge as a strategy to stabilize and protect bicelles encapsulating these nanostructures in liposomes. Results from Dynamic Light Scattering (DLS) and cryo Transmission Electron Microscopy (cryo-TEM) demonstrated a slight modification in the size of both systems when β-carotene was incorporated. EPR revealed that after skin irradiation both systems presented free radical scavenging activity. This activity was statistically significant for bicosomes containing β-carotene. Differences regarding this scavenging activity between bicelles and bicosomes would probably be due to the different interaction of both systems with the skin. In this study, six different radicals were identified in skin spectra: two originated from oxygen centred radicals (primary/secondary and tertiary alkoxyl radicals) and another from carbon-centred radicals. Additionally, the presence of 5,5-dimethyl-2-oxo-pyrroline-1-hydroxyl (DMPO-OH), 5,5-dimethyl-2-oxo-pyrroline-1-hydrogen (DMPO-H) adducts and aminoxyl radicals (RR′NO˙) were detected. Considering these results, bicelles and bicosomes could be useful lipid systems for future dermopharmaceutical applications.

A lamellar body mimetic system for the treatment of oxazolone-induced atopic dermatitis in hairless mice

BACKGROUND Atopic dermatitis is a common skin disease characterized by a Th2 cell-dominant inflammatory infiltrate, elevated serum IgE levels and impaired epidermal barrier function. It is associated to abnormal epidermal lamellar body secretion, producing alteration in lipid composition and extracellular lamellar membrane organization. OBJECTIVES The oxazolone-induced atopic dermatitis in hairless mice was used to evaluate in vivo the effect of the application of a lipid system that mimics the morphology, structure and composition of epidermal lamellar bodies. METHODS The skin barrier function was evaluated measuring TEWL and skin hydration in vivo. Inflammation was assessed by analysis of serum IgE levels and histological analysis. The microstructure of the intercellular lipid region was also evaluated before and after treatment. RESULTS The skin condition was improved after 10 days of treatment indicated by decreased TEWL, decreased serum IgE levels, reduced epidermal thickness and reduced lymphocyte-dominated infiltrate. However, the treatment did no improve skin hydration. CONCLUSIONS The treatment with this lipid system seems to improve the skin condition by reinforcing the barrier function and reducing the skin inflammation. Therefore, the present study provides evidence that this lipid system combining appropriate lipid composition and morphology could be of interest for the development of future treatments for atopic dermatitis.

Sorption–desorption test for functional assessment of skin treated with a lipid system that mimics epidermal lamellar bodies

Many skin diseases are associated with either increases or decreases in lamellar body secretion, or dysfunctional lamellar bodies. Consequently, diseased skin is characterized by reduced barrier function and altered lipid composition and organization. Human skin is commonly evaluated in vivo with non‐invasive biophysical techniques. The dynamic functions of the skin are evaluated with repeat measurements such as the sorption–desorption test (SDT).

Reducing the Harmful Effects of Infrared Radiation on the Skin Using Bicosomes Incorporating β-Carotene.

Aim: In this work the effect of infrared (IR) radiation, at temperatures between 25 and 30°C, on the formation of free radicals (FRs) in the skin is studied. Additionally, the influence of IR radiation at high temperatures in the degradation of skin collagen is evaluated. In both experiments the protective effect against IR radiation of phospholipid nanostructures (bicosomes) incorporating β-carotene (Bcb) is also evaluated. Methods: The formation of FRs in skin under IR exposure was measured near physiological temperatures (25-30°C) using 5,5-dimethyl-1-pyrroline-N-oxide spin trap and electron paramagnetic resonance (EPR) spectroscopy. The study of the collagen structure was performed by small-angle X-ray scattering using synchrotron radiation. Results: EPR results showed an increase in the hydroxyl radical in the irradiated skin compared to the native skin. The skin collagen was degraded by IR exposure at high temperatures of approximately 65°C. The treatment with Bcb reduced the formation of FRs and kept the structure of collagen. Conclusions: The formation of FRs by IR radiation does not depend on the increase of skin temperature. The decrease of FRs and the preservation of collagen fibers in the skin treated with Bcb indicate the potential of this lipid system to protect skin under IR exposure.

Synchrotron Radiation for Diagnosis of Skin Conditions

The skin acts as a physical barrier at the interface with the external environment. This barrier is designed to protect the organism against insults, including desiccant, mechanical, chemical, and microbial damage. It is primarily composed of three layers: the epidermis, dermis, and hypodermis. The epidermis, which contains the stratum corneum (SC), works as a barrier, preventing water loss from the body and protecting it from the environment. The dermis contains fibroblasts as the predominant cell type within a matrix of structural proteins (collagen or elastin), proteoglycans, nervous fibres and sebaceous glands. The hypodermis acts as a thermal and mechanical insulator. Skin contains non-crystalline material, such as collagen, SC lipids and fat, with characteristic scattering patterns that are altered under specific conditions. These changes can be useful for understanding the structure and state of the tissue.