![]() For example, bioartificial vascular grafts have been produced by seeding endothelial cells onto the luminal surface of small-diameter (6 mm or less) synthetic vascular grafts. The surface onto which cells are grown is often shaped according to the final application. The barrier function can be assessed via measurement of the electrical conductivity across the monolayer or rate of leakage of proteins as well as other relevant compounds. The cells then often form tight junctions between themselves which are similar to that found in vivo. When the barrier function of the epithelium or endothelium is an important component of the design of the tissue, cells can be cultured on a smooth surface, which allows cells to form a monolayer. Yarmush, in Encyclopedia of Physical Science and Technology (Third Edition), 2003 III.B.2 Tissue Constructs Using Epithelial Cells The mechanical enhancements of TDD are a rapidly growing technology, and we expect many applications in clinical situations in the near future.įrançois Berthiaume, Martin L. The microneedles coated with drug were developed for direct drug releasing by dissolving off in the skin. The micron-scale pores at the skin surface after inserting and removing the microneedles increase drug permeability. The solid microneedles, which were fabricated out by using silicon, metals, glass, ceramic, and polymers in a variety of shapes and sizes, were developed for pretreatment to increase skin permeability ( Kim et al., 2012). The different concepts of micron-size needles for TDD through the main barrier properties of the stratum corneum have been reported using the microfabrication techniques, for instance, solid, coated, dissolving, and hollow microneedles. ![]() The microneedles have been used to enhance the TDD of small- and large-molecule drugs by penetrating the stratum corneum. The mechanical enhancements of TDD have enhanced physically the drug permeation through the skin surface using heating, noncavitational/cavitational ultrasounds, thermal ablation, and microneedles by physical stimulations. The clinical applications of novel TDD techniques have been expanded for several diseases, because TDD can be enhanced by several approaches, typically chemical, electric, and mechanical techniques. These techniques have contributed to clinical trials for TDD of hydrophilic and macromolecule drugs and vaccines. The third generations of TDD have attempted to overcome the barrier of stratum corneum using specific instruments, which are microneedles, thermal ablation, microdermabrasion, electroporation, and cavitational ultrasound. The second generations of TDD have aimed to enhance dose amount of transdermal drug by mechanical and electric equipment, for example, noncavitational ultrasound and iontophoresis. The first generations of TDD, which achieved a delivery of small and lipophilic drug permeating the skin, have applied in clinical use and have been continued to increase positively for patience. Overall, the TDD has been gradually developed at several generations ( Prausnitz and Langer, 2008). The barrier function of the skin, which protects from permeating harmful virus and particles into the skin and avoiding evaporating water in the skin, has been an elemental problem for the TDD. Kenji Kikuchi, in Integrated Nano-Biomechanics, 2018 4.4.4 Enhancement of TDD
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