Biodegradable, intelligent, and self-healing hydrogel beads showing peroxidase activity has been prepared by adding hemin to "DNA quadruplex hydrogel" beads prepared by assembling dG(4)-PEG-dG(4) triblock copolymers through G quadruplex formation between the dG(4) portion. Efficient binding of hemin to parallel G-quadruplexes in hydrogels was confirmed by observing hyperchromicity of hemin absorbance. The enzymatic activity of resulting hemin peroxidase was visualized both with fluorogenic and chromogenic substrates. These observations serve as the first direct evidence of the presence of G-quadruplexes in DNA quadruplex hydrogels utilizing G-quadruplexes. (C) The Author(s) 2019. Published by ECS.