Oxygen-Rich Graphene/ZnO2-Ag nanoframeworks with pH-Switchable Catalase/Peroxidase activity as O2 Nanobubble-Self generator for bacterial inactivation

Abstract

The oxygen-rich organic/inorganic (reduced graphene oxide (rGO)/ZnO2-Ag) nanoframeworks as suppliers of O2 nanobubbles (NBs) with dual pH-and-temperature-sensitive behavior were developed to suppress bacterial growth. It was demonstrated that not only the rate but also the final product of oxygen-rich ZnO2 decomposition (to an intermediate product of H2O2) rate was dramatically controlled by pH adjustment. Furthermore, in the presence of Ag nanoparticles, ̇OH radical generation switched to O2 NBs evolution by shifting the pH from acidic to basic/neutral conditions, demonstrating an adjustable nanozyme function-ability between catalase and peroxidase-like activity, respectively. Antibacterial properties of the in-situ generated O2 NBs substantially enhanced against bacterial models including methicillin-resistant Staphylococcus aureus in the presence of rGO. In fact, deflecting the electrons from their main respiratory chain to an oxygen-rich bypath through rGO significantly stimulated reactive oxygen species (ROS) generation, combating bacteria more efficiently. Moreover, NIR laser irradiation-induced temperature rise (due to the inherent photothermal properties of rGO) facilitated ZnO2 decomposition and accelerated growth and collapse of NBs. The simultaneous microscale thermal and mechanical destructions induced stronger antibacterial behavior. These results hold great promises for designing simple organic/inorganic nanoframeworks as solid sources of NBs with tunable enzyme-like ability in response to environmental conditions suitable for forthcoming graphene-based bio-applications.