FIGURE 2.

Graphical overview of the routes toward nanocarrier-mediated administration. (A) Injections: nanopreparations are administered via intramuscular, subcutaneous, intravenous, and intradermal. (B) Nano-based eye drop: enhanced ability to penetrate the ocular barrier and prolonged drug residence time at the ocular surface. (C) Intranasal transport route of therapeutic nanomaterials from the nasal cavity to the brain through nasal mucosa, trigeminal nerve and respiratory epithelium. Intranasal drugs may be transported to the olfactory bulb by paracellular or transcellular transport along olfactory neurons or across the nasal epithelium. Within the nasal respiratory epithelial region, the drug would travel via the trigeminal nerve to the CNS, or traverse the respiratory epithelium to access the bloodstream prior to entering the CNS. (D) Oral: nanocarrier-encapsulated drug protects the drug from destruction by digestive enzymes and improves drug absorption through the intestinal epithelium. (E) Transdermal: the interaction between nanocarriers and skin is influenced by regulating the lipophilicity, size, shape, and surface charge of the nanocarriers, which improves the skin penetration efficiency of the nanocarriers.