Single nonfouling hydrogels with mechanical and chemical functionality gradients.

Hydrogels are widely studied as tissue engineering scaffolds, but the biological tissues they are designed to mimic are often complex tissues with non-uniform chemical and mechanical profiles. This work reports a new strategy to create hydrogels composed of a continuous sheet of a single nonfouling but functionalizable material with mechanical and/or chemical functionality gradients. By using different combinations of functionalizable or nonfunctionalizable versions of nonfouling carboxybetaine methacrylate (CBMA) and carboxybetaine dimethacrylate crosslinker (CBMAX), various hydrogels with gradients of crosslinking densities and/or functionalizable groups can be created. In this work, we demonstrate this concept with two nonfouling hydrogels, both with a mechanical gradient: one with uniform functionalizability and the other with a gradient in chemical functionalizability. With this versatile system, hydrogels with built-in gradient profiles of various types can be controlled at will for a given application.