Electrochemical immunosensor for determination of cardiac troponin I using two-dimensional metal-organic framework/Fe 3 O 4 -COOH nanosheet composites loaded with thionine and pCTAB/DES modified electrode.

Cardiac troponin-I (CTnI) is one of the most popular biomarkers which can be utilized for the diagnosis and control of acute myocardial infarction in clinical practice. Here, a sandwich-type electrochemical immunosensor has been established using the zinc-based metal-organic framework/Fe ₃ O ₄ -COOH/thionine labeled anti-CTnI monoclonal antibody (Ab ₁ -Zn-MOF/Fe ₃ O ₄ -COOH/Thi) nanocomposite as signaling molecule and a polymer film of cetyltrimethylammonium bromide (pCTAB) in the presence of choline chloride-urea deep eutectic solvent (DES) and anti-CTnI polyclonal antibody (Ab ₂ ) as immobilization substance of detecting surface. The porous ultrathin layers of Zn-MOF nanosheets successfully prepare a well-defined structure for Fe ₃ O ₄ -COOH electrocatalyst and Thi within a certain two dimensional (2D) regions, which enhances electrochemical reduction of Thi. The Ab ₁ -Zn-MOF/Fe ₃ O ₄ -COOH/Thi nanocomposites were introduced to CTnI in the specimen and on the surface of pCTAB/DES-Au-SPE quantitative determination of CTnI was achieved using differential pulse voltammetry after sandwiching the CTnI target between Ab ₁ -nanocomposite and Ab ₂ which was encapsulated into the pCTAB/DES-Au-SPE. This immunosensor indicated the appropriate assay performance for CTnI with the detection range of 0.04 ng mL ^-1 to 50 ng mL ^-1 and the limit of detection of 0.0009 ng mL ^-1 . This study provides convenient plan for sensitive detection of bioanalytes and opens a path for the establishment of user-friendly and cost-effective device.
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