Open three-dimensional network, microporous hydrogels containing substrates attached to binding molecules is disclosed. The hydrogel is comprised of a hydrated gel matrix containing substrates embedded in the matrix. The substrates are attached to binding molecules that selectively bind specific molecules that encounter the hydrogel. Thus the hydrogel serves to selectively bind out target molecules from an aqueous environment or sample that the hydrogel comes in contact with and concentrates them within the hydrogel.
