Electrochemical Sensitive Detection of Alpha-Fetoprotein Using HRP-Gold Nanostructures on Fe–Co MOF-Derived Nanocomposites

A highly sensitive and selective electrochemical immunosensor was developed for the detection of the cancer biomarker alpha-fetoprotein (AFP), a key indicator of cancer. This sensor utilizes the enhanced electrochemical current response generated by a composite material consisting of gold nanoparticles (Au NPs) decorated on a metal-organic framework (MOF) containing iron and cobalt (FeCo). The Au NP-decorated FeCo-based MOF labeled with primary antibodies (Ab₁) significantly enhances the electrochemical response, enabling accurate detection of AFP. Similarly, HRP-Au nanoprism (Au NPR) nanocomposites were prepared via a one-pot assembly, where horseradish peroxidase (HRP) and the secondary antibody (Ab₂) were coimmobilized on Au NPRs to form a stable nanocomposite. The immunosensor was fabricated by assembling Au NPs@ FeCo-MOF and capture antibodies (Ab₁) onto a glassy carbon electrode. The MOF served as a conductive matrix, AuNPs enhanced electron transfer, and Ab₁ ensured specific antigen recognition. When the AFP antigen is present, labeled Ab₂ binds to the Au NP-decorated FeCo-MOF via specific antigen-antibody interactions, leading to enhanced electrochemical signals for sensitive detection. The immunosensor response was measured by differential pulse voltammetry (DPV) in phosphate-buffered solution (PBS) containing hydrogen peroxide (H₂O₂) and 3,3',5,5'-tetramethylbenzidine (TMB). Under controlled conditions, the immunosensor exhibited a linear response to AFP over the range of 0.0001 to 100 ng mL^-1, with a detection limit of 1.2 pg mL^-1 (S/N = 3), indicating high sensitivity. The immunosensor's performance was validated by detecting AFP in human serum samples, demonstrating its potential for ultrasensitive detection of AFP and other biomarkers.