Tailored Quantum Dots@Metal–Organic Frameworks for Enhanced Hypochlorite Detection in Live Cells and Ulcerative Colitis Diagnosis

Excess levels of hypochlorous acid/hypochlorite (HClO/ClO^-) are associated with the development of tissue damage and the onset of various pathological conditions. The enzymatic reaction of myeloperoxidase produces HClO/ClO^-, which is closely related to hepatic ulcerative colitis (UC). The detection of HClO is particularly important as it provides valuable insights into the early diagnosis of UC. In this study, we introduce a new class of quantum dot@metal-organic framework composites, specifically QD-PEI@ZIF-8, fabricated via the one-pot solvothermal method. These composites are based on aqueous quantum dots (QDs) of surface amine ligands (QD-PEI), which promote the epitaxial growth of zeolitic imidazolate framework (ZIF-8) structures. The resulting QD-PEI@ZIF-8 composites demonstrate enhanced optical properties and stability. The highly porous QD-PEI@ZIF-8 composites exhibit better specificity for ion selection and improve detection sensitivity. The fluorescence burst of the QD-PEI@ZIF-8 composite enabled highly specific detection of ClO^-, covering a wide linear range from 10 to 120 μM, and its limit of detection (LOD) was improved to 0.38 μM, representing a 36-fold enhancement in sensitivity compared to the QD-PEI. Furthermore, the QD-PEI@ZIF-8 composite was validated for live cell imaging applications. By optimization of the detection conditions, a "sampling-detecting" capillary sensor for ClO^- detection in the fecal samples from both mice and human subjects with UC disease was developed. This strategy provides a novel QD-PEI@ZIF-8 composite and capillary sensor for specific, sensitive, and efficient detection of HClO/ClO^-, with implications for both cellular regulation and detection of UC diseases.