The label-free electrochemical S100B-TBI immunosensor for sensitive detection of S100B protein as a biomarker for traumatic brain injury using FFT-SWV voltammetry.

S100B protein is an established biomarker related to prognosis in traumatic brain injury (TBI). Developing sensitive methods for the serum S100B quantification is clinically valuable. This paper proposes a simple label-free electrochemical TBI-immunosensor for the timely detection of S100B in the sera of TBI patients. In the first step of bioelectrode fabrication, gold nanoparticles-reduced graphene oxide (AuNPs-rGO) nanocomposite was layered onto a glassy carbon electrode (GCE) to improve the amplification of electrochemical signals. The anti-S100B was immobilized onto a modified-GCE via self-assembly monolayers using 11-Mercaptoundecanoic acid and EDC-NHS. Electrochemical immunoassay was planned based on forming of an immunocomplex bioaccumulation among S100B and anti-S100B, resulting in a decline peak current in the [Fe (CN)6]3-/4- redox couple. The modification steps of immobilization were morphologically or electrochemically characterized by scanning electron microscopy, cyclic voltammetry, and impedance spectroscopy techniques. A fast Fourier transform square wave voltammetry was applied to peak current change in accordance with the concentration of S100B under optimal experimental conditions. The fabricated immunosensor detected sensitively the S100B in the linear range of 0.75-75,000 pg mL-1, with a detection limit of 1.31 pg mL-1, which comprises the whole biosynthesis broad of S100B in healthy and TBI patients. Likewise, no cross-reactivity was observed with other interfering S100 family proteins, denoting the excellent selectivity and specificity. Moreover, good reproducibility and stability were obtained for the fabricated immunosensor. Immunosensor performance for S100B-spiked serum exhibited a recovery range of 93.33-106.64%. Given its analytical performance, this immunosensor shows promise as a tool for rapid serum S100B measurement in patients with TBI.