Label-Free Bimetallic In Situ-Grown 3D Nickel-Foam-Supported NH₂‑MIL-88B(Fe₂Co)-MOF-based Impedimetric Immunosensor for the Detection of Cardiac Troponin I

In this study, a simple and competent metal–organic framework (MOF)-based nickel foam (NF)-supported three-dimensional (3D) immunosensor (Ab-NH₂-MIL-88B­(Fe₂Co)-MOF/NF) was constructed and utilized for the specific recognition of the biomarker cardiac troponin (I) (cTnI). In the present work, biosensor fabrication was progressed through the modification of the NF substrate with the MOF material (NH₂-MIL-88B­(Fe₂Co)-MOF) to enable an amine-functionalized electrode. This amine-functionalized NF electrodes (NH₂-MIL-88B­(Fe₂Co)-MOF/NF) were then biointerfaced with anti-cTnI antibodies, which ended up as Ab-NH₂-MIL-88B­(Fe₂Co)-MOF/NF electrodes. Analytical executions of the constructed bioelectrode were investigated for the quantitative analysis of cTnI in both buffered and serum solutions. Then, the electrochemical studies were carried out using the electrochemical impedance spectroscopy (EIS) method by monitoring changes concerning the charge transfer resistance (R_ct) characteristics. The limit of detection (LOD) of the Ab-NH₂-MIL-88B­(Fe₂Co)-MOF/NF immunosensor was achieved to be 13 fg/mL with great specificity. This kind of immunosensor imparts a new platform for the construction and application of MOF-hybrid 3D electrode materials with enhanced electrochemical behavior in cTnI sensing for the first time.