Figure 1.

A mixture of guanosine (G), 2‐formylphenylboronic acid (2‐FPBA), and putrescine is reacted to form G‐quartets stabilized with K⁺. G‐quartets self‐assemble through π–π stacking to a G‐quadruplex structure forming a supramolecular, biomimetic G₄‐hydrogel. The G₄‐hydrogel is loaded with hemin and glucose oxidase (GOx). In the first cascade reaction, GOx catalyzes the transformation of glucose and O₂ into H₂O₂, while the combination of the G‐quadruplex and hemin acts as an artificial peroxidase to produce hydroxyl radicals (•OH) from H₂O₂ in the second reaction of the cascade.