Encapsulated cholesterol oxidase in metal-organic framework and biomimetic Ag nanocluster decorated MoS₂ nanosheets for sensitive detection of cholesterol

Herein, a nano-porous metal-organic-framework (MOF) was applied as a safe host for cholesterol oxidase (ChOx) enzyme to improve its stability and implement an efficient oxidation process for substrate molecules. Subsequently, a fluorometric method based on the conversion of non-fluorescent terephthalic acid (TA) to 2-Hydroxyterephthalate with a great fluorescence emission was used for fluorescence detection of the generated H₂O₂. On the other hand, Ag nanocluster (AgNC) decorated MoS₂ nanosheets (MoS₂-NS) nanocomposite as a new mimetic peroxidase catalyst was exploited in TA-H₂O₂ reaction. The synthesized enzyme encapsulated MOF and AgNC/MoS₂-NS nanocomposites were characterized using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction and some other analyzing techniques. The results showed a high porous MOF with a high capacity to uptake ChOx enzymes, improving their catalytic activity. The ChOx-MOF hybrid displayed good efficiency for oxidation of cholesterol. Also, an improved peroxidase-like activity was discovered for AgNC/MoS₂-NS composite, in comparison with each of the constituents or natural peroxidase enzyme (HRP). As a result, the performance of designed cholesterol probe based on ChOx-MOF and peroxidase-like AgNC/MoS₂-NS, was improved significantly, in which it presented a dynamic linear range of 0.06 μM–15 μM with a detection limit (3S) of 0.03 μM. The studied method showed a good selectivity and sensitivity for practical determination of cholesterol and its potential application for cholesterol detection in human blood samples.