Hydrophobic Keratinocytes

Indirect protein patterning Serum proteins from cell culture medium PDMS, methylated glass, bacterial grade PS Human epithelial cells, human keratinocytes, human neuroblastoma cells, human breast cancer cells, human fibroblasts, human embryonic kidney cells, murine macrophages Stencil guided plasma induced oxidation of hydrophobic surfaces 2009 [93]... 

Looking at the barrier in more detail, we find that it can be described as composed of two main components. Interspersed between the corneocytes we find the hydrophobic (water-repellent) substance, the barrier lipids. The keratinized corneocytes containing fibrous and amorphous proteins represent a hydrophilic (water-attracting) component. Neutral lipids (fatty acids, cholesterol) and ceramides dominate the lipid phase, and it is mainly these lipids that are responsible for the control and limitation of water transport through the skin.14 Visualization of the penetration pathway through the skin by tracer methods has demonstrated that the extracellular pathway is likely to be the only route through the barrier for substances other than water.15 Water diffusion through the keratinocytes... 

The epidermis is an epithelium consisting of inner viable epidermis, a living hydrophilic layer, and outer nonviable epidermis, a hydrophobic layer made from dead cells. It is differentiated into stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale In the direction of dermis (Fig. 16.2). The viable epidermal layer has a thickness of about 0.02 to 0.2 mm. It is composed of many layers of keratinocytes, a widespread distribution of melanocytes, Langerhans cells, dendritic T cells, epidermotropic lymphocytes and Merkel cells, and a number of catabolic enzymes such as esterases, proteases, phosphatases, nucleotidases and lipases [Walters and Roberts, 2002 Barry, 2001). The outer and nonviable epidermis, namely, stratum corneum, is about 10 to 20 pm thick [Gregor and Ulrich, 2010). The stratum corneum Is deemed to be the major obstacle of drug permeation. 

In Fig. 2.16 it shows the skin composition in layers, the stratum comeum, granular, spinosum, and basal. The epidermis uppermost layer, the stratum comeum, has keratinocytes tightly linked by des-mosomes in a hydrophobic cellular matrix. This sfructure CTeates an anatomical barrier against irritants, alleigens, and shear force. In addition to the physical barrier, there are mediators of resistance such as leucocytes, cytokines, complanent cascade, and host defense peptides [AMPs]. 

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