Fig. 6

Smart delivery of 4-hexylresorcinol (4HR) using hydrophobic and hydrophilic domains of silk fibroin. Silk fibroin is a macromolecule composed of hydrophilic and hydrophobic domains. As 4HR is composed of a long alkyl group (hydrophobic) and 2 hydroxyl groups (hydrophilic), 4HR can be bound to each domain according to its molecular interaction. As hydrophilic interactions are much weaker than hydrophobic interactions, 4HR in the hydrophilic domain of silk fibroin is released first. 4HR in the hydrophobic domain is released during proteolysis