In one aspect, the disclosure provides cross-linked materials that include multivalent lectins with at least two binding sites for glucose, wherein the lectins include at least one covalently linked affinity ligand which is capable of competing with glucose for binding with at least one of said binding sites and conjugates that include two or more separate affinity ligands bound to a conjugate framework, wherein the two or more affinity ligands compete with glucose for binding with the lectins at said binding sites and wherein conjugates are cross-linked within the material as a result of non-covalent interactions between lectins and affinity ligands on different conjugates. These materials are designed to release amounts of conjugate in response to desired concentrations of glucose. Depending on the end application, in various embodiments, the conjugates may also include a drug and/or a detectable label.
