Differential activity of superoxide dismutase in response to tetrahedral and polyhedral DNA nanostructures: A...

Although DNA tetrahedral and polyhedral nanometer cages have enormous potential for drug delivery, biosensing, and bioimaging, a lack of understanding about the impact of DNA polyhedrons on biomolecules limits their practical uses. Here, we have investigated the biomolecular interactions between a major antioxidant enzyme, Copper-Zinc superoxide dismutase (CuZnSOD), and several DNA polyhedral nanostructures, including tetrahedron, cube, prism, and square pyramid. CuZnSOD, the first line of antioxidant defence enzymes, safeguards eukaryotic cells from oxidative stress that leads to various pathophysiological sates. The activity of SOD remained unaltered with 25 or 100 nM of DNA polyhedrons after 1 or 24 h of incubation. The absorbance peak of SOD rises with a red shift following titration with DNA polyhedrons. Furthermore, the anti-parallel β-sheet structure of SOD has undergone a conformational change, as indicated by CD spectroscopic studies. The binding mechanism between the SOD and DNA polyhedrons was investigated using isothermal titration calorimetry and fluorescence spectroscopy. Out of all the investigated DNA polyhedral structures, the DNA tetrahedron has a higher affinity for SOD with least impact on its secondary conformation. Furthermore, it was noted that the activity of cellular CuZnSOD was enhanced in the presence of DNA tetrahedron. The ROS scavenging activity of SOD was enhanced in presence of DNA polyhedral nanostructures. The presence of DNA polyhedral nanostructures appears to decrease ROS production in cells, as indicated by lower absorbance values in the NBT assay. Collectively, these findings suggest that DNA polyhedrons bind to the CuZnSOD without affecting the functional behaviour of the protein.