Immunosensing of S100β biomarker for diagnosis of spinal cord injuries (SCI)

S100 calcium-binding protein β (S100β), a member of the S100 protein family, is one of the spinal cord injury (SCI) biomarkers extensively studied for its diagnostic and prognostic potential. The concentration of S100β is found to increase in the blood and cerebrospinal fluid (CSF) after SCI. Here, we developed an electrochemical immunosensor that offers label-free and direct detection of S100β to aid the diagnosis and prognosis of SCI. A screen-printed graphene electrode was modified by electrochemically reducing nitrate from 4-nitrobenenediazonium tetrafluoroborate to an amine group. The covalent conjugation of S100β monoclonal antibody was then achieved on the electrode surface by activating the amine group using glutaraldehyde. Characterization of the electrode was implemented using differential pulse voltammetry (DPV) in presence of potassium ferricyanide (K3[Fe(CN)6]) redox probe. Upon testing the samples on the modified electrode with different concentrations of S100β, the DPV current peak decreased with the increase in concentration of S100β biomarker. We achieved sensitive and selective label-free detection of S100β in the dynamic range of 1 pg/ml-104 pg/ml for samples prepared in phosphate buffer saline (PBS), artificial CSF (aCSF), and human blood serum. The performance of the immunosensor was validated by correlating the results for samples tested with commercially available enzyme-linked immunosorbent assay (ELISA) method.