Scaffold also can be used to provide adequate signals (e.g., through the use of adhesion peptides and growth factors) to the cells, to induce and maintain them in their desired differentiation stage, and to maintain their survival and growth. In addition, the incorporation of drugs (i.e., inflammatory inhibitors and/or antibiotics) into scaffolds may be used to prevent infection after surgery and other disease for longer duration. Their application of late has extended to delivery of drugs and genetic materials, including plasmid DNA, at a controlled rate over a long period of time. They also are used in joint pain inflammation, diabetes, heart disease, osteochondrogenesis, and wound dressings. Scaffold are used successfully in various fields of tissue engineering such as bone formation, periodontal regeneration, repair of nasal and auricular malformations, cartilage development, as artificial corneas, as heart valves, in tendon repair ,in ligament replacement, and in tumors. These techniques allow the preparation of porous structures with regular porosity. Techniques used for fabrication of a scaffold include particulate leaching, freeze-drying, supercritical fluid technology, thermally induced phase separation, rapid prototyping, powder compaction, sol-gel, and melt moulding. Bioceramics such as hydroxyapatites and tricalcium phosphates also are used. Biomaterials used for fabrication of scaffold may be natural polymers such as alginate, proteins, collagens, gelatin, fibrins, and albumin, or synthetic polymers such as polyvinyl alcohol and polyglycolide. Scaffold matrices can be used to achieve drug delivery with high loading and efficiency to specific sites. A scaffold provides a suitable substrate for cell attachment, cell proliferation, differentiated function, and cell migration. Different forms of polymeric scaffolds for cell/drug delivery are available: (1) a typical three-dimensional porous matrix, (2) a nanofibrous matrix, (3) a thermosensitive sol-gel transition hydrogel, and (4) a porous microsphere. Scaffolds are implants or injects, which are used to deliver cells, drugs, and genes into the body.
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