Electrochemical microsensors for cutaneous surface analysis: Application to the determination of pH and the antioxidant properties of stratum corneum

Potentiometry and cyclic voltammetry were proposed as simple, reliable and non invasive methods for the simultaneous determination of pH and antioxidant properties of skin. Experiments were performed with microelectrodes just deposited on skin surface without any gel or water added. pH was measured by means of the zero current potential of a tungsten W/WO3 sensor. A nerstian response was recorded in pH range 4 to 6 corresponding to the normal skin pH values. The global antioxidant capacity was deduced from the anodic charge passed during the plotting of cyclic voltammograms on platinum or gold microelectrodes. Comparing the half wave or peak potentials of these curves with those recorded for experiments performed in aqueous solution, the main hydrophilic antioxidants species were detected, i.e. ascorbic acid, uric acid and glutathione. This relatively easy-to-use analytical method made it possible to follow in real time the efficiency of topic treatment as well as to study the influence of oxidative stres

Elaboration of integrated microelectrodes for the detection of antioxidant species

(Pt–Pt–Ag/AgCl) and (Au–Pt–Ag/AgCl) electrochemical microcells (ElecCell) were developed for the detection of redox species by cyclic voltammetry. A special emphasis was placed on the SU-8 waferlevel passivation process in order to optimize the electrochemical properties of the different “thin film” metallic layers, i.e. gold or platinum for the working electrode, platinum for the counter electrode and silver/silver chloride for the reference electrode. (Au–Pt–Ag/AgCl) microcells were applied for the detection of antioxidant species such as ascorbic and uric acids in phosphate buffer solution, evidencing high sensitivity but low selectivity. Works were extended to skin analysis, demonstrating that a good electrical contact with the skin hydrolipidic film allowed the effective evaluation of the skin global antioxidant capacity

Exploration of the global antioxidant capacity of the stratum corneum by cyclic voltammetry

Cyclic voltammetry is proposed as a new method for evaluating the antioxidant capacity of skin based on the reducing properties of low molecular weight antioxidants (LMWA). Experiments were performed simply by recording the anodic current at 0.9 V/SCE of a platinum microelectrode placed directly on the epidermis surface without any gel or water. This method ensured a direct, rapid (less than 1 min), reliable (accuracy 12%) and non-invasive measurement of the global antioxidant capacity of the stratum corneum with a high spatiotemporal resolution. At the same time, the pH of the skin surface was determined by recording the cathodic current at 0 V/SCE. Based on an exploratory study involving nine volunteer subjects, the evolution of the amperometric response of the microelectrode with time revealed a periodic modification of the redox properties

Raman characterization of human skin aging

Skin aging is a complex biological process mixing intrinsic and extrinsic factors, such as sun exposure. At the molecular level, skin aging affects in particular the extracellular matrix proteins. Materials and Methods: Using Raman imaging, which is a nondestructive approach appropriate for studying biological samples, we analyzed how aging modifies the matrix proteins of the papillary and reticular dermis. Biopsies from the buttock and dorsal forearm of volunteers younger than 30 and older than 60 were analyzed in order to identify chronological and photoaging processes. Analyses were performed on skin section, and Raman spectra were acquired separately on the different dermal layers. Results: We observed differences in dermal matrix structure and hydration state with skin aging. Chronological aging alters in particular the collagen of the papillary dermis, while photoaging causes a decrease in collagen stability by altering proline and hydroxyproline residues in the reticular dermis. Moreover, chronological aging alters glycosaminoglycan content in both dermal compartments. Conclusion: Alterations of the papillary and reticular dermal matrix structures during photo-and chronological aging were clearly depicted by Raman spectroscopy

Les produits topiques dépigmentants (essai de mesure de leur efficacité par microscopie confocale in vivo)

Les produits dépigmentants sont de plus en plus utilisés en Europe. En effet, l'augmentation des expositions solaires et le vieillissement de la population induisent une augmentation de l'incidence des taches hyperpigmentées telles que les lentigos actiniques. Ce travail s'intéresse aux tests d'objectivation des produits dépigmentants. Matre objectif est d'utiliser la microscopie confocale in vivo pour quantifier l'effet dépigmentant d'une crème sur le lentigo. La microscopie confocale in vivo est une nouvelle technique d'observation non invasive de la peau. Elle permet l'acquisition de coupes optiques de la peau et donne donc une grande quantité d'informations, tout en évitant les biopsies. La microscopie confocale a été utilisée pour l'exploration des troubles hyperpigmentés, et, de manière illustrative, dans les tests d'objectivation de leurs traitements. L'utilisation de cette technique comme outil de mesure biométrologique est cependant une première. Ce travail relate l'essai clinique mis en place afin d'étudier la possibilité de quantifier l'effet d'un produit dépigmentant par mièroscopie confocale in vivo. Ce document présente les fondements du projet, en particulier sur la pigmentation cutanée et la microscopie confocale. Puis la méthodologie de l'étude clinique y est décrite, ainsi que les raisons nous ayant poussé à la choisir. Enfin, il explique les difficultés rencontrées durant l'étude clinique et l'analyse des résultatsLYON1-BU Santé (693882101) / SudocSudocFranceF

The use of suction blisters to measure sunscreen protection against UVR- induced DNA damage

International audienc

DNA photoproducts released by repair in biological fluids as biomarkers of the genotoxicity of UV radiation

International audienceUV-induced formation of photoproducts in DNA is a major initiating event of skin cancer. Consequently, many analytical tools have been developed for their quantification in DNA. In the present work, we extended our previous liquid chromatography-mass spectrometry method to the quantification of the short DNA fragments containing photoproducts that are released from cells by the repair machinery. We designed a robust protocol including a solid phase extraction step (SPE), an enzymatic treatment aimed at releasing individual photoproducts, and a liquid chromatography method combining on-line SPE and ultra-high performance liquid chromatography for optimal specificity and sensitivity. We also added relevant internal standards for a better accuracy. The method was validated for linearity, repeatability and reproducibility. The limits of detection and quantification were found to be in the fmol range. The proof of concept of the use of excreted DNA repair products as biomarkers of the genotoxicity of UV was obtained first in in vitro studies using cultured HaCat cells and ex-vivo on human skin explants. Further evidence were obtained from the detection of pyrimidine dimers in the urine of human volunteers collected after recreational exposure in summer

DNA photoproducts released by repair in biological fluids as biomarkers of the genotoxicity of UV radiation

International audienceUV-induced formation of photoproducts in DNA is a major initiating event of skin cancer. Consequently, many analytical tools have been developed for their quantification in DNA. In the present work, we extended our previous liquid chromatography-mass spectrometry method to the quantification of the short DNA fragments containing photoproducts that are released from cells by the repair machinery. We designed a robust protocol including a solid phase extraction step (SPE), an enzymatic treatment aimed at releasing individual photoproducts, and a liquid chromatography method combining on-line SPE and ultra-high performance liquid chromatography for optimal specificity and sensitivity. We also added relevant internal standards for a better accuracy. The method was validated for linearity, repeatability and reproducibility. The limits of detection and quantification were found to be in the fmol range. The proof of concept of the use of excreted DNA repair products as biomarkers of the genotoxicity of UV was obtained first in in vitro studies using cultured HaCat cells and ex-vivo on human skin explants. Further evidence were obtained from the detection of pyrimidine dimers in the urine of human volunteers collected after recreational exposure in summer

Efficacy of D-pigment dermocosmetic lightening product for solar lentigo lesions of the hand: A randomized controlled trial.

Solar lentigo, benign lesions which mostly appear on chronically, sun-exposed surfaces, are associated with ageing. Patients are increasingly requesting a more uniform skin texture, especially for hands. Treatment options include dermoabrasion, intense pulsed light, cryotherapy, peelings, and laser therapy. Topical compounds can be employed, in alternative or associated with dermatologic procedures. The current study was designed to evaluate solar lentigo hyperpigmentation, skin architecture and clinician and patient assessments comparing a dermocosmetic lightening product (active) with a moisturizing product (control) according to clinical, digital and subjective analyses in 72 lesions over 12-month follow up period. Statistically significant differences were observed between the lesions treated with the active compared to the control in terms of papillary brightness (p = 0.03) and contrast (p = 0.03), and in the limitation of dermal-epidermal junction destructuring (p = 0.03) according to dermal-epidermal junction destructuring score at Reflectance Confocal Microscopy. Luminance (p = 0.04) and redness (p = 0.03) were improved at color analysis, and physician and patient evaluations favored the active in efficacy and patient satisfaction investigations. The dermocosmetic lightening product utilized in the current study proved to be more effective, according to clinical, digital and subjective analyses in reducing lesion hyperpigmentation, stabilizing the lesion skin architecture and increasing patient satisfaction compared to the control in a cohort of 36 subjects, over a 12-month period. Beside demonstrating the efficacy of this topical lightening product, we propose a "destructuring score", which improves the robustness of solar lentigo's evaluation, and can be used in future studies to standardize the quantitative comparisons of different treatment options

Sub-optimal Application of a High SPF Sunscreen Prevents Epidermal DNA Damage in vivo

International audienceThis is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Acta Derm Venereol 2018; 98: 880-887 880 SIGNIFICANCE Skin cancer is an increasing public health burden in many countries. Most skin cancers are caused by DNA damage from ultraviolet radiation in sunlight. This study shows that a very high sun protection factor sunscreen can inhibit DNA damage in the skin caused by high doses of artificial sunlight , even when the sunscreen is used less than optimally. The data suggest that sunscreen use is likely to reduce skin cancer and that there should be more emphasis in communicating how to best use sunscreens in public health campaigns. The cyclobutane pyrimidine dimer (CPD) is a potentially mutagenic DNA photolesion that is the basis of most skin cancers. There are no data on DNA protection by sunscreens under typical conditions of use. The study aim was to determine such protection, in phototypes I/II, with representative sunscreen-user application. A very high SPF formulation was applied at 0.75, 1.3 and 2.0 mg/cm 2. Unprotected control skin was exposed to 4 standard erythema doses (SED) of solar simulated UVR, and sunscreen-treated sites to 30 SED. Holiday behaviour was also simulated by UVR exposure for 5 consecutive days. Control skin received 1 SED daily, and sunscreen-treated sites received 15 (all 3 application thicknesses) or 30 (2.0 mg/cm 2) SED daily. CPD were assessed by quantitative HPLC-tandem mass spectrometry (HPLC-MS/MS) and semi-quantitative immunostaining. In comparison with unprotected control sites, sunscreen significantly (p ≤ 0.001-0.05) reduced DNA damage at 1.3 and 2.0 mg/cm 2 in all cases. However, reduction with typical sunscreen use (0.75 mg/cm 2) was non-significant, with the exception of HPLC-MS/MS data for the 5-day study (p < 0.001). Overall, these results support sunscreen use as a strategy to reduce skin cancer, and demonstrate that public health messages must stress better sunscreen application to get maximal benefit