Enzyme responsive properties of amphiphilic urea supramolecular hydrogels

Abstract

Amphiphilic ureas with hydrophilic lactose groups form transparent supramolecular hydrogels. Their gelation abilities are sensitive to the length of the alkyl chain. Amphiphilic ureas bearing hexyl, heptyl, octyl, and nonyl groups form supramolecular hydrogels, but amphiphilic ureas bearing decyl groups or longer alkyl groups do not show gelation ability. The gradual gel-to-sol phase transition of the supramolecular hydrogel is triggered by adding β-galactosidase (β-Gal) as a result of enzymatic hydrolysis of the lactose moiety. Supramolecular hydrogels could stably entrap cationic organic dyes, such as rhodamine 6G (Rh6G), even in water. The entrapped Rh6G could be gradually released in the presence of β-Gal, along with the gel-to-sol phase transition. Lactose-coupled amphiphilic ureas are worked as low-molecular-weight hydrogelators (LMWHGs). Their gelation abilities are sensitive to the length of the hydrophobic alkyl chain. Gradual gel-to-sol phase transition of the supramolecular hydrogel was occurred by adding β-galactosidase (β-Gal) as a result of enzymatic hydrolysis of the lactose moiety. Supramolecular hydrogels could stably entrap cationic organic dyes even in water. The entrapped dye could be gradually released in the presence of β-Gal, along with the gel-to-sol phase transition.