Xiong et al. (Xiong et al., 2020) developed a pH-responsive Fe-based MOF system MOF@HA@PCA loaded with an anti-inflammatory protocatechuic acid (PCA) and modified with hyaluronic acid (HA), which can respond to the acidic microenvironment and gradually released for treating osteoarthritis PCA, which downregulates the expression of osteoarthritis inflammatory markers and promotes the expression of cartilage-specific markers, significantly reducing IL-1β-induced synovial inflammation in both joints and chondrocytes. The gene discussed is IL1B; the disease is osteoarthritis.