PROJECT SUMMARY In this proposal, we aim to characterize the multi-enzymatic and chondroprotective functions of a bioactive biomaterial, manganese dioxide (MnO2) nanoparticles (NPs), as a therapeutic strategy to mitigate oxidative stress in osteoarthritis (OA). The motivation for this work is the critical need to address limitations for treating OA as a looming public health crisis, projected to affect 130 million people worldwide by 2050 due to an aging population. Oxidative stress, the imbalance between reactive oxygen species (ROS) generation and antioxidant function, is known to contribute to OA progression and may represent an important therapeutic target. There have been numerous studies to evaluate the use of antioxidants and small molecules as therapeutic agents, however these therapies are limited by poor bioavailability and stability within the joint. The objective of this proposal is to utilize a metal-oxide biomaterial (MnO2) to overcome limitations of retention and bioavailability and seeks to explore enzyme-mimicking functions to reduce the effects of oxidative stress. We have previously shown that MnO2 can be engineered with cartilage-targeting properties, such as size and charge, that can overcome limitations of traditional antioxidant therapies. Leveraging these properties we have seen improved retention of MnO2 NPs in healthy and OA joints. Due to the barriers for targeting cartilage, this advancement is critical in the development of a chondroprotective therapy. We hypothesize that MnO2 NPs possess enzyme mimicking properties that will reduce oxidative stress in the joint thereby alleviating pain and disease pathogenesis. Characterization of enzyme mimicking functions is critical in the use of MnO2 NPs for biomedical applications and may further classify the biomaterial as a ‘nanozyme.’ Our lab has already characterized the hydrogen peroxide scavenging properties of MnO2 NPs and we anticipate ‘nanozyme’ classification will outline catalase-like, superoxide-like, and peroxidase-like functions of MnO2. In Aim 1, we will examine how MnO2 NPs influence compartment specific H2O2 production and the downstream effects of oxidative stress. Specifically, we will characterize the antioxidant-like properties of MnO2 NPs and their impact on redox signaling, chondroprotection, and inflammatory effects. In Aim 2 we will evaluate the therapeutic efficacy of MnO2 NPs in vivo using a rodent model of post traumatic OA (PTOA) through comprehensive evaluation of NP retention in the joint, joint remodeling, and behavior. Immediate treatment following joint trauma, which leads to PTOA, is a critical opportunity for translation of a cartilage targeting therapy by leveraging cartilage that is still intact and may be responsive to mitigating oxidative stress. The proposed work is significant and innovative by revealing key mechanisms for mitigating oxidative stress and advancing the use of an enzyme-mimicking therapy that may facilitate translation ...