Light-Mediated Reversible Modulation of ROS Level in Living Cells by Using an Activity-Controllable Nanozyme.

Nanozymes have shown great potential in bioapplications owing to their low cost, high stability, multiple activity, and biocompatibility. However, most of the known nanozymes are always at turn-on state, hindering their further applications. Herein, a simple and versatile method for constructing activity-controllable nanozymes is presented. To the best of our knowledge, this is the first report to utilize the light-driven isomerization of azobenzene (Azo) and host-guest interaction to reversibly photoregulating the activity of nanozyme. Gold nanoparticles as a typical catalase-mimic nanozyme are used in this design. The expanded Azo-modified mesoporous silica is employed as supported material to encapsulate and disperse Au nanoparticles, which further combines with cyclodextrin (CD). The catalytic activity of the nanozyme is blocked by CD and can be activated or inhibited reversibly by UV or visible light. The results indicated that the nanozyme can reversibly regulate reactive oxygen species (ROS) level in extracellular and intracellular environment for multiple cycles and change cell viability by simply changing the irradiated light. This is a general method and can be adapted to construct various smart nanozymes with highly spatiotemporal resolution.