Skin: The skin serves as the first line of defense, preventing the entry of microorganisms and potentially harmful substances. Nanoparticles designed for transdermal delivery must overcome the stratum corneum, the outermost layer of the skin. Mucosal Membranes: These membranes line various cavities in the body and are involved in the absorption and secretion processes. Effective nanoparticle delivery systems must navigate the mucus and underlying epithelial cells. Blood-Brain Barrier (BBB): The BBB is a highly selective barrier that protects the brain from toxins and pathogens. Nanoparticles intended for neurological applications must be designed to cross this barrier without causing damage. Cellular Membranes: Cellular membranes are crucial for maintaining cellular integrity and function. Nanoparticles must be able to enter cells to deliver therapeutic agents directly to intracellular targets.
