Fig. 3: Architecture of the Ca²⁺-responsive MNAzyme system for dual-gene adjustment.

a Secondary structure of the traditional 17E DNAzyme. b Variant structures of the 17E DNAzyme. N’ represents the alternative site and can be an A, T, G, or C deoxynucleotide. c Structure of the Ca²⁺-responsive 17E-based MNAzyme system. d The final MNAzyme system with high Ca²⁺ affinity for miRNA-21 triggered HSP70 mRNA cleavage. e The NUPACK web application simulated the equilibrium concentration of each binding chance. f Twenty percent polyacrylamide gel electrophoresis experiments for different formulations. g Verification of the Ca²⁺ concentration-dependent MNAzyme system. h Cancer biomarker response test. i Construction logic of the cancer biomarker-responsive MNAzyme system. The experiments in (f–h) were repeated three times independently with similar results. PTT photothermal therapy, T target strand, R right partzyme, L left partzyme, S substrate mRNA.