Metal–Organic Framework Based Electrochemical Immunosensor for Label-Free Detection of Glial Fibrillary Acidic Protein as a Biomarker

Abstract

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