Ultrasensitive Determination of Glial-Fibrillary-Acidic-Protein (GFAP) in Human Serum-Matrix with a Label-Free Impedimetric Immunosensor

Label-free electrochemical immunosensing of glial fibrillary acidic protein (GFAP) at synthesized rGO/MoS2/AgNPs nanocomposite. Application to the determination in human cerebrospinal fluid

An electrochemical bioplatform involving screen-printed carbon electrodes modified with rGO/MoS2/AgNPs nanocomposites, the covalent immobilization of the specific capture antibody, and label-free detection has been developed for the determination of Glial Fibrillary Acidic Protein (GFAP). The resulting immunosensor profits the benefits of the rGO high conductivity, the pseudo-peroxidase activity of MoS2 and the electrocatalytic effect provided by AgNPs for improving the reduction current responses of hydrogen peroxide at the electrode surface. GFAP is a biomarker of central nervous system injuries has been proposed for the detection and monitoring of neurological diseases as epilepsy, encephalitis, or multiple sclerosis. For the first time, amperometric detection of the immunosensing event was performed by measuring the electrocatalytic response of hydrogen peroxide reduction at the modified electrode. Several techniques including scanning (SEM) and transmission (TEM) electron microscopies were used for the characterization of the synthesized composite whilst electrochemical impedance spectroscopy (EIS) using the redox probe Fe(CN)63-/4- was employed to evaluate the success of the steps implied in the fabrication of the immunosensor. After optimization of the involved experimental variables, a linear calibration plot for GFAP was constructed over the 0.6-100 ng mL-1 range, and a detection limit of 0.16 ng mL-1 was achieved. The developed immunosensor was successfully applied to the determination of GFAP in human cerebrospinal fluid (CSF) of patients diagnosed with encephalitis.

Prediction of clinical progression in nervous system diseases: plasma glial fibrillary acidic protein (GFAP)

Glial fibrillary acidic protein (GFAP), an intracellular type III intermediate filament protein, provides structural support and maintains the mechanical integrity of astrocytes. It is predominantly found in the astrocytes which are the most abundant subtypes of glial cells in the brain and spinal cord. As a marker protein of astrocytes, GFAP may exert a variety of physiological effects in neurological diseases. For example, previous published literatures showed that autoimmune GFAP astrocytopathy is an inflammatory disease of the central nervous system (CNS). Moreover, the studies of GFAP in brain tumors mainly focus on the predictive value of tumor volume. Furthermore, using biomarkers in the early setting will lead to a simplified and standardized way to estimate the poor outcome in traumatic brain injury (TBI) and ischemic stroke. Recently, observational studies revealed that cerebrospinal fluid (CSF) GFAP, as a valuable potential diagnostic biomarker for neurosyphilis, had a sensitivity of 76.60% and specificity of 85.56%. The reason plasma GFAP could serve as a promising biomarker for diagnosis and prediction of Alzheimer's disease (AD) is that it effectively distinguished AD dementia from multiple neurodegenerative diseases and predicted the individual risk of AD progression. In addition, GFAP can be helpful in differentiating relapsing-remitting multiple sclerosis (RRMS) versus progressive MS (PMS). This review article aims to provide an overview of GFAP in the prediction of clinical progression in neuroinflammation, brain tumors, TBI, ischemic stroke, genetic disorders, neurodegeneration and other diseases in the CNS and to explore the potential therapeutic methods.