EA 7506 Biospectroscopie Translationnelle (BioSpectT), Faculty of Pharmacy, University of Reims Champagne-Ardenne, Reims, France.
Biophysic Laboratory, Faculty of Medicine and Pharmacy of Tangier, AbdelMalek Essâdi University, Tangier, Morocco.
Int J Cosmet Sci. 2022 Oct;44(5):588-601. doi: 10.1111/ics.12808. Epub 2022 Aug 17.
The objective of our research was to investigate the heat-protecting effect of a product ex vivo and in vivo on human hair fibres.
A preparatory study was carried out in order to determine an optimal threshold of thermal stress. For this, the structure of cross-sections of the hair fibre was observed by optical microscopy. Then, Scanning Electron Microscopy (SEM) and Confocal Raman Spectroscopy (CRS) were applied to analyse ex vivo and in vivo morphological and molecular damage in hair structure after heat stress. Finally, in vivo tests were used to collect consumer perception.
The preparatory study enabled us to determine an optimal stress threshold of 10 heating cycle for SEM and 5 heating cycle for CRS. Based on spectral hierarchical classification using Ward's clustering algorithm, the ex vivo Raman results show that the spectral signature of the hair treated and heated is very close to the negative control. This shows that the product preserves the keratin structure after thermal stress. These results were also confirmed by an in vivo Raman analysis performed on hair samples from 5 donors. In concordance with Raman results, SEM shows that treated hair presents lesser "bubbles" and "crackling" on the hair surface. Finally, the in vivo studies proved that hair was more protected from heat.
The authors concluded that the product shows protective properties with respect to morphological and molecular heat damage. We also demonstrate that the product promotes the α-helix keratin conformation and preserves the S-S disulfide bands.
本研究旨在探讨一种产品在人体头发纤维上的体外和体内热保护效果。
为了确定热应激的最佳阈值，我们进行了一项预备研究。为此，通过光学显微镜观察头发纤维的横截面结构。然后，应用扫描电子显微镜（SEM）和共焦拉曼光谱（CRS）分析头发结构在热应激后的体外和体内形态和分子损伤。最后，进行体内试验以收集消费者的感知。
预备研究使我们能够确定 SEM 的最佳应激阈值为 10 个加热循环，CRS 的最佳应激阈值为 5 个加热循环。基于使用 Ward 聚类算法的光谱分层分类，体外拉曼结果表明，处理和加热后的头发的光谱特征与阴性对照非常接近。这表明该产品在热应激后能保持角蛋白结构。这些结果也得到了对来自 5 名供体的头发样本进行的体内 Raman 分析的证实。与 Raman 结果一致，SEM 显示处理后的头发在头发表面出现较少的“气泡”和“爆裂”。最后，体内研究证明头发受到了更好的热保护。
作者得出结论，该产品在形态和分子热损伤方面表现出保护特性。我们还证明，该产品促进α-螺旋角蛋白构象并保持 S-S 二硫键带。
