Title: In vitro models of skin for topical and systemic drug delivery applications

 

In the modern drug development, drug delivery through the skin is gaining significant importance. Optimizing the delivery of a drug through the skin is imperative to use the potential of this route entirely. In the early stage of product development, optimization of skin formulations through the use of optimal carrier considered being an essential process in enhancing the pharmacokinetic parameters of a drug. Development and optimization of skin formulations need appropriate skin models which should be able to recognize and assess the characteristic properties of the formulations. Ex vivo animal/human models of the skin play a critical role for most of the current optimization of skin formulations. However, arti?cial skin models are gaining much importance nowadays because of the increasing ethical concern in use of human and animals skin (Flaten et al., 2015).
Skin is the most significant organ in the human body concerning its weight and surface area. Histologically, it is a three-layered structure consisting an outermost layer, the epidermis, followed by connective tissue layer, the dermis, and the innermost layer, the subcutis (Planz et al., 2016). Other than these layers, sweat glands, sebaceous glands, blood vessels, nerves, hair follicles, and lymphatics are also present in the skin. These different appendages of the skin help in performing essential functions of the body like protection, absorption, excretion, metabolic functions, thermoregulation, aesthetics, evaporation management, and sensation. Mainly, it acts as an active guard of an organism from environmental in?uences such as microbial invasion and hazardous UV-radiation along with thermal, chemical and physically damaging.