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Disorders of Keratinization and Other Genodermatoses
Published in Ayşe Serap Karadağ, Lawrence Charles Parish, Jordan V. Wang, Roxburgh's Common Skin Diseases, 2022
Roselyn Stanger, Nanette Silverberg
Overview: The differentiation process in which basal epidermal cells gradually mature and transform into stratum corneum cells is known as keratinization. In this process, which takes about 14 days, plump, cuboidal or spheroidal, hydrated, highly metabolically active cells gradually become tough, hardened, biochemically inactive, thin, shield-like structures that are programmed to desquamate off the skin surface. This process is biochemically complex; therefore, it is not surprising that it is subject to genetically determined errors. During keratinization, a tough, chemically resistant, cross-linked protein band is laid down just inside the plasma membrane, and the whole cell flattens to a thin disc, or corneocyte. The corneocyte’s water content is reduced from the usual 70% to 30%, and most of the cellular organelles, including its nucleus, are eliminated. The keratinous tonofilaments become organized in bundles and are spatially oriented. A further characteristic feature of the normal stratum corneum is the presence of an intercellular cement material that contains non-polar lipid and glycoprotein.
Bioresponsive Hydrogels for Controlled Drug Delivery
Published in Deepa H. Patel, Bioresponsive Polymers, 2020
Tamgue Serges William, Dipali Talele, Deepa H. Patel
On the basis of their chemical or physical behavior of the cross-link junctions, two types are distinguished: Chemically cross-linked networks have stable junctions, while physical cross-linked networks have temporary junctions which are the results of either polymer chain entanglements or physical interactions such as ionic interactions, hydrogen bonds or hydrophobic interactions [16].
Biological reactions to reconstructive materials
Published in Steven J. Kronowitz, John R. Benson, Maurizio B. Nava, Oncoplastic and Reconstructive Management of the Breast, 2020
Steven J. Kronowitz, John R. Benson, Maurizio B. Nava
Collagen cross-linking in ADMs has been shown to be another determinant of biologic response. The purpose of cross-linking is to mechanically strengthen the ADM and prevent its degradation.7,28 Intentional cross-linking occurs through the use of chemical agents such as gluteraldhyde, whereas unintentional cross-linking of collagen can result from processes such as gamma irradiation used to sterilize the ADM.7 Cross-linked porcine ADM has been shown to undergo less cellular infiltration and neovascularization when compared to non-cross-linked porcine ADM.29 However, newer cross-linking technologies may offer benefits of improved strength paired with improved biointegration.30
Non-genetic risk factors for keratoconus
Published in Clinical and Experimental Optometry, 2023
Minji Song, Qing Yi Fang, Ishith Seth, Paul N Baird, Mark D Daniell, Srujana Sahebjada
Recent literature has focused on the potential connection between diabetes mellitus and keratoconus. The two most recent meta-analyses in 2021 and 2022 conducted by Xing-Xuan et al.28 and Akowuah et al.29 respectively, uniformly concluded no significant association between diabetes and keratoconus but found that diabetes might have a protective effect for keratoconus. An overall estimate of OR was found to be 0.86 (95% CI 0.73, 1.02). The meta-analyses included studies conducted by Lin et al.,13 Woodward et al.,30 Naderan et al.,24 Kuo et al.,12 and Seiler et al.,31 almost all of which were retrospective in nature. Therefore, more prospective studies assessing the association between diabetes mellitus and keratoconus are needed. Furthermore, the protective effect of diabetes mellitus on keratoconus may be explained by the induction of crosslinks by glycosylation of corneal fibres due to elevated glucose, thus strengthening the cornea and reducing the risk of developing ectasia and keratoconus.28 Since there is consistent evidence in the clinical literature regarding the association of diabetes mellitus and keratoconus, there is a need to establish viable therapies aimed at raising glucose levels locally in the cornea to prevent and treat keratoconus.28
A Review of Lens Biomechanical Contributions to Presbyopia
Published in Current Eye Research, 2023
The lens capsule plays a critical role in the development of the ocular lens as well as influencing how lens properties change throughout life. Changes to the lens capsule structure can heavily influence lens behavior, especially with regard to accommodation since the lens capsule is the densest and most stiff structure in the ocular lens. It is also the thickest basement membrane in the body.3 Electron microscope analysis revealed that the lens capsule is composed of parallel lamellae which are more tightly packed near the outer surface of the lens. The lamellar structure of the lens capsule appears to disappear with age and the capsule becomes more homogeneous.3 The capsule consists mostly of collagen types I, III, and IV, with collagen IV forming the majority of the basement membrane. Type IV collagen forms a mesh network loosely resembling chicken wire, with crosslinking between the triple helical collagen strands. These cross links are thought to consist largely of 7S domain disulfide cross-link bonds. Collagen IV may also be more flexible than other collagen types like collagen I and II due to having more interruptions between its triple helical segments where crosslinking and molecular binding occurs. Collagen molecules typically interlink through bonding of triple helical domains to form thicker collagen fibrils, and these fibrils can then continue to lace together into thicker rope like fibers or intertwine into a mesh.3
Enhanced transdermal insulin basal release from silk fibroin (SF) hydrogels via iontophoresis
Published in Drug Delivery, 2022
Phimchanok Sakunpongpitiporn, Witthawat Naeowong, Anuvat Sirivat
Silk Fibroin (SF) is a protein polymer which can be extracted from the cocoons of silkworms (Bombyx mori) consisting of fibroin and sericin (Kapoor & Kundu, 2015). SF is of excellent biocompatibility, superior mechanical property, very useful in biomedical material functions (tissue and scaffold engineering, drug carrier). SF can be fabricated into various forms such as film, nanofiber, sponge, and hydrogel (Kim & Park, 2016). SF hydrogels can be formed by either a physical or chemical crosslink. The physical crosslink is preferred in TDDS because of the concern on human skin toxicity through toxic crosslinkers (Lim, 2015). The physical crosslink of SF occurs from the transformation from the random coil (silk I) to the β-sheet (silk II) (Wu et al., 2019). SF can form a gel by itself but it requires about 30 days for a complete gelation (Lim, 2015). Therefore, the external stimuli have been applied to accelerate the physical crosslinking such as ultrasonication, temperature, and electric field (Wu et al., 2019).