Due to the small size of a nanoconfinement, the property of water contained inside is rather challenging to probe. Herein, we measured the amount of water molecules released during the folding of individual G-quadruplex and i-motif structures, from which water activities are estimated in the DNA nanocages prepared by 5 × 5 to 7 × 7 helix bundles (cross-sections, 9 × 9 to 15 × 15 nm). We found water activities decrease with reducing cage size. In the 9 × 9-nm cage, water activity was reduced beyond the reach of regular cosolutes such as polyethylene glycol (PEG). With this set of nanocages, we were able to retrieve the change in water molecules throughout the folding trajectory of G-quadruplex or i-motif. We found that water molecules absorbed from the unfolded to the transition states are much fewer than those lost from the transition to the folded states. The overall loss of water therefore drives the folding of G-quadruplex or i-motif in nanocages with reduced water activities.

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Artificial enzymes such as nanozymes and DNAzymes are economical and stable alternatives to natural enzymes. By coating Au nanoparticles (AuNPs) with a DNA corona (AuNP@DNA), we amalgamated nanozymes and DNAzymes into a new artificial enzyme with catalytic efficiency 5 times higher than AuNP nanozymes, 10 times higher than other nanozymes, and significantly greater than most of the DNAzymes on the same oxidation reaction. The AuNP@ DNA demonstrates excellent specificity as its reactivity on a reduction reaction does not change with respect to pristine AuNP. Single-molecule fluorescence and force spectroscopies and density functional theory (DFT) simulations indicate a long-range oxidation reaction initiated by radical production on the AuNP surface, followed by radical transport to the DNA corona, where the binding and turnover of substrates take place. The AuNP@DNA is named coronazyme because of its natural enzyme mimicking capability through the well-orchestrated structures and synergetic functions. By incorporating different nanocores and corona materials beyond DNAs, we anticipate that the coronazymes represent generic enzyme mimics to carry out versatile reactions in harsh environments.

One-pot synthesis of nitrogen doped mesoporous graphitic carbon spheres with dispersed metal oxide nanoparticles using a single temperature treatment step serves as one of the big challenges in materials research.