FIG. 4.

Schematic of light-activated “caged” DNAzymes. (A) and (B) The photocleavable group (PS/thymidine, indicated by a square) in the core region and binding arms causes the DNAzyme to separate upon UV irradiation. (C, D) Circularized DNAzymes have diminished activity, photolysis of the photocleavable group restores the active form. (E) Incorporation of the photocleavable group into catalytic core and arm regions render DNAzyme inactive until removal of the group by UV irradiation activates the DNAzyme. (F, G) Incorporation of azobenzene nucleotide and overhang complementary to the catalytic core region are reversibly (cis-activation/trans-deactivation) photo-isomerized by UV irradiation. Adapted from Ref. Richards et al.[89]. (H) pH-responsive DNA tetrahedral nanocage, the enzyme/DNAzyme is integrated into the tetrahedral structure. Changes to pH allow reversible activation/deactivation.