There has been a perpetual demand for skin and its replacements, which has fuelled advances in the development of novel skin substitutes. The field of skin bioengineering has made mammoth progress in the last 30 years, helped by the advances in the biotechnology and understanding of wound-healing mechanisms. The options for skin substitutes currently range from the cadaveric skin of the past to a number of epidermal, dermal and composite constructs. This review focuses on the clinical applications of various skin substitutes currently available, looking into their advantages and disadvantages and the scope for future improvements.
KEYWORDS: allograft • autograft • bioengineering • skin substitute • xenograftOverview of skin substitutes, driving needs Skin is the largest and a vital organ of the body, made of multiple layers of epithelial tissues. Skin plays the most important role in protecting the body against chemicals and pathogens. Its other main functions are insulation, control of evaporation and temperature regulation. The outermost epidermis consists of stratified squamous epithelium with the underlying connective tissue, the dermis, and the hypodermis or basement membrane. The epidermis forms the waterproof, protective wrap over the body surface against mechanical, chemical or thermal stress, and consists of keratinocytes, melanocytes, Langerhans' cells and merkels cells. Keratinocytes undergo differentiation and express several proteins, such as keratins and cadherins. Dermis is situated below the epidermis and consists of dense connective tissue fibers that cushion the body from stress and strain and also gives the dermis its properties of strength, elasticity and extensibility. Collagen is a main protein of the connective tissue and forms the extracellular matrix, which is interwoven with elastin fibers and glycosaminoglycans (GAGs), that supports most tissues and gives cells their outer structure. Skin is exposed to a wide range of insults, such as burns and trauma, resulting in complex wounds, and management of such wounds poses a great challenge. Wound closure requires a material to restore epidermal barrier function and become incorporated into the healing wounds. The use of skin grafts as a wound cover was well established in early 1970. Skin substitutes in the form of allografts (cadaver skin and human amnion) and xenografts (mainly pig) were used with the greatest potential for restoring the altered physiology of skin after severe burns and ulcers. Currently, bioengineered skin products and skin equivalents have been used for treating acute and chronic burn wounds. Since the discovery of keratinocyte sheets for wound-healing applications [1], several modifications in skin substitutes with multiple compositions were designed and tested for treating wounds [1,2]. Recent skin substitutes contain live cells, such as fibroblasts and keratinocytes, in bioengineered scaffolds of natural or synthetic matrices, which provide mechanical stability for the cells to grow [3]. For long-term recovery, the str...