Periodontitis is a chronic oral inflammatory disease whose treatment is often hindered by poor drug retention, prolonged therapeutic regimens, and the rise of antibiotic resistance. In this study, we developed a Hydrogel@ZIF-8@metronidazole (Hydrogel@ZIF-8@MNZ) nanocomposite dressing for targeted, sustained, and in situ antimicrobial therapy. This system integrates ZIF-8, a pH-responsive metal–organic framework, with the antimicrobial agent metronidazole (MNZ), encapsulated within a crosslinked hydrogel matrix to enhance stability and retention in the oral environment. Drug release studies demonstrated that MNZ release was significantly accelerated under acidic conditions (pH 5.0), mimicking the periodontal microenvironment. The Hydrogel@ZIF-8 composite achieved a maximum MNZ adsorption capacity of 132.45 mg·g⁻¹, with a spontaneous and exothermic uptake process best described by a pseudo-second-order kinetic model, suggesting chemisorption as the dominant mechanism. The nanoplatform exhibited strong pH-responsive behavior, with enhanced drug release under acidic conditions and potent dose-dependent bactericidal activity against Fusobacterium nucleatum (Fn). At the highest tested concentration, bacterial survival was reduced to approximately 30%, with extensive membrane disruption observed through live/dead fluorescence microscopy. In summary, the stimuli-responsive Hydrogel@ZIF-8@MNZ nanocomposite offers an intelligent and effective therapeutic strategy for periodontitis. By tailoring its action to the disease microenvironment, this platform enables sustained and localized antibacterial therapy, addressing major challenges in the treatment of chronic oral infections.

Arsenic (As) and cadmium (Cd) in rice grains are major global food safety concerns. Iron (Fe) can help reduce both, but current Fe treatments suffer from poor stability, low leaf absorption, and fast soil immobilization, with unclear underlying mechanisms. To address these issues, an Fe-based metal–organic framework (MIL-88) was modified with sodium alginate (SA) to form MIL-88@SA. Its stability as a foliar inhibitor and its leaf absorption were tested, and its effects on As and Cd accumulation in rice were compared with those of soluble Fe (FeCl₃) and chelating Fe (HA + FeCl₃) in a field study on As–Cd co-contaminated rice paddies. Compared with the control, MIL-88@SA outperformed or matched the other Fe treatments. A single foliar spray during the tillering stage increased the rice yield by 19% and reduced the inorganic As and Cd content in the grains by 22.8% and 67.8%, respectively, while the other Fe treatments required two sprays. Its superior performance was attributed to better leaf affinity and thermal stability. Laser ablation inductively coupled plasma–mass spectrometry (LA–ICP–MS) and confocal laser scanning microscopy (CLSM) analyses revealed that Fe improved photosynthesis and alleviated As–Cd stress in leaves, MIL-88@SA promoted As and Cd redistribution, and Fe–Cd co-accumulation in leaf veins enhanced Cd retention in leaves.

The karst region of Southwest China represents a typical high geological background area characterized by extensive carbonate bedrock and secondary enrichment of heavy metals, particularly cadmium (Cd), in residual soils. Under natural carbonate-buffered conditions, Cd is largely immobilized through mineral associations and surface complexation, resulting in elevated total concentrations but low bioavailability. However, intensified anthropogenic pressures–including acid deposition, mining, excessive fertilization, and improper irrigation—have accelerated soil acidification in paddy fields. Acidification disrupts carbonate geochemical equilibria, weakens buffering capacity, and drives Cd speciation shifts toward more labile forms, thereby enhancing plant uptake and accumulation. These effects are especially pronounced in paddy fields and other systems subject to hydrological and redox fluctuations that further increase Cd mobility. To evaluate these coupled geogenic and anthropogenic controls, we conducted a structured literature synthesis (2016–2026) focusing on peer-reviewed studies of Cd dynamics in Southwestern China’s karst agroecosystems. We critically examine (i) the formation mechanisms and spatial heterogeneity of high-background Cd, (ii) acidification-driven speciation transformation and soil–crop transfer pathways, and (iii) in situ remediation and precision risk assessment strategies. By integrating geological inheritance, geochemical activation, and ecological risk perspectives, this review proposes a conceptual framework to support soil quality standard refinement and adaptive risk management in high-background karst regions.