Characterization of photodamaged skin, development and clinical efficacy of dermocosmetic formulations by biophysical and skin imaging techniques

Author(s)

Daiane Garcia Mercurio

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2015-12-01

Examining board members

Patricia Maria Berardo Gonçalves Maia Campos; Ediléia Bagatin; Luis Alexandre Pedro de Freitas; Carolina Baraldi Araújo Restini

• Advisor: Patricia Maria Berardo Gonçalves Maia Campos

Abstract

Photoaging is a subject of great interest in cosmetics and dermatology. Thus, it is important to characterize photodamaged skin and the development of appropriate dermocosmetic formulations for this purpose. Vitamins A and E and their derivatives have emerged as active substances for this purpose, and, based on this concept, an innovative compound was proposed, the Tocoretinate (ester of all-trans retinoic acid and D-?-tocopherol), which is a potential active ingredient to replace retinoic acid, acting on the improvement of photodamaged skin conditions. The objective of this project is to characterize the skin changes due to photoaging and to develop, evaluate the stability and clinical efficacy of anti-aging cosmetic formulations containing Tocoretinate, retinyl palmitate and tocopheryl acetate. An experimental design of three factors in three levels of experience (Box-Behnken) with response surface methodology (RSM) was performed to evaluate the main effects and interactions of raw materials of the formulations. Three formulations were selected containing, or not, 0.5% retinyl palmitate, 5% tocopheryl acetate and 0.1% Tocoretinate, which were submitted to stability tests. The characterization of the brazilian photodamaged skin on the face, forearms and back of the hands was carried out on 80 volunteers in two age groups through self-assessment questionnaires and biophysical and skin imaging techniques. The same evaluation was performed on the volar forearm and face of 41 French volunteers aged between 40-65 years old. The developed formulations were evaluated by biophysical and skin imaging techniques before, and after 84 days of application of the formulations. RSM allowed the evaluation of the effects of the raw materials on the responses: rheological behavior, sensory properties and hydration. The formulations were considered stable in stability tests. The clinical and morphological features related to photoaging were: loss of the elastic quality, more wrinkles, less echogenicity, higher individual typological angle and larger size of corneocytes and a thicker stratum corneum. For the morphological analysis, an irregular pigmentation pattern was observed, keratinocytes irregularly distributed, flattening of the dermal-epidermal junction and the presence of damaged collagen fibers. Different morphological, structural and biophysical characteristics were found in Brazilian and French skin, that are exposed to different environmental factors and has distinct habits. The formulation containing Tocoretinate acted on skin hydration, elasticity, reduced stratum corneum thickness, increased epidermal thickness, improved uniformity, reduced skin pigmentation, and also increased depth of dermal papillae. Formulations containing derivatives of vitamins A and E acted on skin barrier function and hydration, increasing the portion of the viscoelastic curve and improved the interkeratinocyte reflectance after 84 days of the study. The characterization of the skin by biophysical techniques and skin imaging analysis was fundamental in effectively defining the clinical study protocol applying these techniques. The clinical study showed the efficacy of the formulations developed containing Tocoretinate in improving photodamaged skin conditions, and provides relevant scientific basis for the use of this innovative active ingredient both in dermocosmetics and in dermatology. (AU)

• FAPESP's process: 12/01573-1 - Characterization of photodamaged skin, development and clinical efficacy of dermocosmetic formulations by biophysical and skin imaging techniques
• Grantee: Daiane Garcia Mercurio
• Support Opportunities: Scholarships in Brazil - Doctorate