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Basics of Hierarchical and Functionally Graded Structures and Mechanical Characterization by Nanoindentation: A Paradigm Shift for Nano/Microstructural Length Scale
Published in Arjun Dey, Anoop Kumar Mukhopadhyay, Nanoindentation of Natural Materials, 2018
Arjun Dey, Deeksha Porwal, Nilormi Biswas, Aniruddha Samanta, Manjima Bhattacharya, Mohammed Adnan Hasan, A. K. Gupta, Anoop Kumar Mukhopadhyay
Now, the cortex region is protected from harsh environment by multilayered sheet-like scales of cuticle cells. The lamellar structure of cuticle is schematically shown in Figure 1.9. The amount of cystine is rich at the outer layer of cuticle. The amount of cystine subsequently diminishes while it grows toward the cuticle-cortex junction. Thus, the graded mechanical properties are observed in cuticle layers. As described earlier, high cystine guarantees the superior mechanical integrity in outer layers of cuticle. However, lower mechanical properties are observed in the inner side of cuticle due to its lower cystine content. Further, the outer layer of hair, that is, the cuticle, provides chemical resistance, water inertness, and protective nature.
Biology of the Hair and Skin
Published in Randy Schueller, Perry Romanowski, Conditioning Agents for Hair and Skin, 2020
Hair damage results from both mechanical and chemical trauma that alters any of the physical structures of the hair. Conditioning agents cannot enhance repair, since repair does not occur, but can temporarily increase the cosmetic value and functioning of the hair shaft until removal of the conditioner occurs with cleansing. The cuticle is the main hair structure affected by conditioning agents (80), An intact cuticle is responsible for the strength, shine, smoothness, softness, and manageability of healthy hair. A layer of sebum coating the cuticle also adds to hair shine and manageability.
Proteins in Cosmetics
Published in E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
E. Desmond Goddard, James V. Gruber
In a greatly simplified description, which omits the fine details of hair architecture, human hair fiber is composed of two main structural components: the cuticle, composed of 5- 10 layers of overlapping flat cells containing nonfibrous keratin with a high content of cystine residues ( 1 for 2.7 amino acids on average); and the cortex, the dominant structural element of the hair (60-90% of the fiber), which is responsible for its mechanical and elastic properties. The cortex is composed of long, spindle-like cells aligned with the fiber’s axis, filled with microfibrils of low-sulfur α-keratin embedded in a high-sulfur β keratin matrix (88). Whereas the interior of the hair fiber is widely believed to have little significance with respect to hair condition, the outside layer, the cuticle, is responsible for the tactile and optical perception of hair, governs the frictional properties of the fibers, and, by extensive disulfide cross-linking of its keratin, protects the inner cortex from fibrillation by mechanical or chemical aggression. Even though the cuticle is highly resistant to physical and chemical aggression, it is not immune to damages caused by a variety of mechanical stresses (friction, pulling, bending), exposure to environmental factors (ultraviolet radiation, wind, moisture) and chemical substances. Repeated and long-term exposure to these causes alteration of its surface geometry (roughness) and optical properties (opacity), breakdown and loss of cuticle cells, and exposure of the cortex, which can result in brittleness, splitting, complete fibrillation of the fiber, and finally breakage. Daily grooming procedures of combing, brushing, and towel drying progressively cause uplifting of the cuticles, resulting in an increase of the frictional forces between the hair fibers and the comb and triboelectric charging of the hair (flyaway effect) (89). Exposure of the fibers to high temperature during washing, blow drying, or by heat-styling procedures with hot rollers, curling, and straightening irons accelerates hair damage. Cosmetic treatments involving the use of alkali, reducing agents, and oxidizers cause cystine damage, with solubilization and loss of keratin peptides and amino acids. Shampooing alone can progressively abrade the cuticle and lead to keratin loss. Wet hair has a lower resistance to abrasion and chemical aggression than dry hair, because of its swelling and partial replacement of keratin-keratin cross-links by water bridges, with water-keratin bonds.
Extraction of keratin from unhairing of bovine hide
Published in Chemical Engineering Communications, 2022
Franck da Rosa de Souza, Jaqueline Benvenuti, Michael Meyer, Hauke Wulf, Enno Klüver, Mariliz Gutterres
The keratins are defined as a family of scleroproteins, characterized by the high sulfur content (3%–5%), which is specifically related to cysteine and cystine amino acid residues. They are found in the epidermis layer and in the related appendages, providing mechanical stability and having protective functions (Seifter and Gallop 1966). The hair (in dry basis) is composed of 90%–97% of protein (keratins), 2% of lipids, and the remainder consists of nucleic acid, carbohydrates, and inorganic substances. The chemical composition is around 50% carbon, 22% oxygen, 16% nitrogen, 7% hydrogen, and 5% sulfur (Popescu and Hocker 2007). The hairs are formed by two structures (Wagner and Bailey 1999): the cuticle is the external layer and because of the presence of lipids, it is a hydrophobic in nature; and the cortex, which is the hydrophilic layer inside. The cortex is formed basically by the keratin, packed as α-helix arrangements with high cystine content (Edwards and Routh 1944), assembled in microfibrils (intermediate filament protein, IFP) (Jones et al. 1997), and immersed in a matrix (intermediate filament associated protein, IFAP) (Rogers 1988). Keratin in its α-helix arrangements is the protein that builds up microfibrils. These bigger structures, also called IFP, are locked inside a matrix, which is formed by another class of protein, IFAP. The “A” means that this class of protein is associated to the IFP. The keratins from the matrix contain high sulfur contents, and therefore promote the stability of the structure by introducing crosslinks in the form of disulfide bonds. The range of the IFAP molecular weight is between 10 and 25 kDa. The keratins from intermediate filament (IFP) have a lower content of sulfur and the helical conformation gives support to the structure having molecular weight from 40 to 60 kDa (Rouse and Van Dyke 2010).
Bacteriostasis and cleaning effect of trace ozone replacing personal care products
Published in Environmental Technology, 2023
Yanyan Peng, Zhou Chen, Yanzeng Li, Yuantao Wang, Chengsong Ye, Junming Xu, Shenghua Zhang
Table 5 shows SEM images of the simulated human hair without treatment and after ozone treatment (0.4 mg/L) for 5 min and 10 min. The cuticle crimp degree and cuticle edge integrity of the simulated human hair were scored. Four different grades of simulated human hair damage scores were established to evaluate the degree of damage caused by trace ozone. In the original hair, the hair cuticle overlaps the hair shaft, forming a layered structure around the central cortex that protects the integrity of the hair [42]. However, adverse environmental factors (solar radiation, wind, pollution, perm, dyeing) can damage the morphological structure of hair (warps, cracks, holes) and change its surface properties [43]. As presented in Table S1, before ozone treatment and after ozone treatment (0.4 mg/L) for 5 min and 10 min, the average scores of simulated human hair injury were 0.36, 0.40, and 0.37, respectively, corresponding to the second grade (0.25–0.5). Accordingly, no significant difference (P = 0.820–0.932) was observed between the control group and the treatment group. In this study, some broken edges, warps, and holes were observed on all simulated human hair, likely because the hair fibres had been exposed to adverse environmental conditions prior to ozone treatment. Consequently, the hair morphology and structure were already damaged. The results showed that trace ozone had minimal impact on the fibre quality of simulated human hair. Simulated human hair could be efficiently cleaned using trace ozone for 5 min with no apparent damage. The literature indicates that although prolonged exposure to toxic levels of ozone dose can alter or oxidize the lipid and protein composition of the skin, brief exposure at low and controllable ozone concentrations may be non-toxic [44,45]. This is because ozone immediately reacts with polyunsaturated fatty acids and water in the cuticle of the skin after brief exposure, producing reactive oxygen species (ROS) and lipopeptides (LOP) that are degraded by antioxidants in the skin [45]. Ozone is also an ideal drug at the right concentration, for example, short-term use of ozonated water or ozonated oil can effectively treat skin wound infections [46]. Previous literature has reported the development of an ozone generator for patients with atopic dermatitis that produces the optimal dose of ozonated water during treatment by controlling and measuring accurate ozone concentrations in real time to bathe or soak skin lesions, providing a better option for those who cannot tolerate the adverse effects of medication [47,48]. Therefore, trace ozone may become a new bath tool with great development prospect.