Percutaneous permeation study of fresh, excised rat skin: a comparison with frozen/thawed rat skin / Muhamad Nur Rashid Azizi

Skin is the largest organ of the human body (Figure 1.1 ). The primary function of human skin is to protect human body against chemical, physical and microbial injury. Moreover, it serves as a sensory organ and involves in homeostasis maintenance. The protective nature of the skin is largely depends on its highly differentiated structure. Based on a transdermal drug delivery perspective, human skin is comprised of three major layers: the outermost layer (the non-viable and viable epidermis); the overlying dermis; and the innermost subcutaneous tissues (hypodermis). The main barrier function is located in the non-viable layer of the epidermis, known as the stratum comeum (SC). Its hydrophobic nature is primarily responsible for its highly resistant property against permeation of most exogenous molecules or entities.