Metal–Organic Framework Based Electrochemical\nImmunosensor for Label-Free Detection of Glial Fibrillary Acidic Protein\nas a Biomarker

Abstract

A novel electrochemical\ndetection system for glial fibrillary acidic\nprotein (GFAP) using a label-free manner based on zeolitic imidazolate\nframeworks and reduced graphene oxide anchored with gold nanoparticles\n(Au@ZIF-8@rGO) as a recognition element was developed in urine samples.\nThe chosen immobilization technique was based on increasing more covalent\nbonding using hydroxyl moieties on the Au@ZIF-8@rGO. The concept of\nthe immunosensor is to detect the signal perturbation obtained by\nmeasuring the changes in the charge transfer resistance of the electrode\nby using [Fe­(CN)₆]^3–/4– measurements\nafter binding of the protein during 45 min of incubation without complicated\nprocedures and expensive equipment. Under the optimal conditions,\nthe developed biosensor exhibited a wide linear concentration range\nof 50.0–10 000.0 fg/mL GFAP and an extremely low detection\nlimit of 50.0 fg/mL (detectable). However, the real concentrations\nof GFAP protein in the human body are in the concentration range of\nour immunosensor, indicating that the developed immunosensor looks\npotentially compatible with practical applications. Moreover, the\ndeveloped immunosensor has been applied to the assay of GFAP in urine\nsamples with satisfying results, indicating the applicability of the\nas-fabricated biosensor. This work provides a new sensing platform\nfor GFAP detection and dramatically expands the application of metal–organic\nframeworks (MOFs) in the electrochemical field.