Nanobubbles Suppressing Singlet Oxygen-Mediated Oxidation via Size-Dependent Interfacial Effects

Abnormal accumulation of reactive oxygen species (ROS) induces oxidative stress, a central pathological factor in many human diseases. Traditionally, antioxidants are suggested to relieve oxidative stress in the body; however, their efficacy is limited by poor stability in vivo and inadequate tissue targeting in clinical practice. Therefore, there is a great need for an effective, safe, biocompatible, and environmentally friendly antioxidant strategy to reduce damage caused by oxidative stress. Previous work has demonstrated that nanobubbles (NBs) can regulate hydroxyl radical (^•OH)-mediated redox reactions. However, it remains unclear whether NBs can exert similar regulatory control on singlet oxygen (¹O₂), and the molecular mechanisms that control this interaction need to be elucidated. In this work, we employed photodynamic reactions to generate ¹O₂ and systematically investigated the effects of NBs of different particle sizes and different encapsulated gas compositions (N₂ or O₂) on ¹O₂-mediated oxidation of selective fluorescent probes. Our findings indicate that ultrasmall NBs exhibit remarkable antioxidant activity across all test systems and that even NBs prepared with O₂, a gas that typically enhances ROS-driven oxidation, inhibit ¹O₂-mediated substrate oxidation. These insights establish a basic framework for the rational design of NB-based antioxidant platforms, which hold significant promise for applications in biomedical antioxidant therapy, material protection, and food preservation.