Controlled, partially exfoliated, self-supported functionalized flexible graphitic carbon foil for ultrasensitive detection of SARS-CoV-2 spike protein

Muhammad Adeel; Kanwal Asif; Vincenzo Canzonieri; Hasi Rani Barai; Md Mahbubur Rahman; Salvatore Daniele; Flavio Rizzolio

doi:10.1016/j.snb.2022.131591

Controlled, partially exfoliated, self-supported functionalized flexible graphitic carbon foil for ultrasensitive detection of SARS-CoV-2 spike protein

Sens Actuators B Chem. 2022 May 15:359:131591. doi: 10.1016/j.snb.2022.131591. Epub 2022 Feb 21.

Authors

Muhammad Adeel^{1

2}, Kanwal Asif^{1

2}, Vincenzo Canzonieri^{2

3}, Hasi Rani Barai⁴, Md Mahbubur Rahman⁵, Salvatore Daniele¹, Flavio Rizzolio^{1

2}

Affiliations

¹ Department of Molecular Sciences and Nanosystems, Ca'Foscari University of Venice, 30123 Venezia, Italy.
² Pathology Unit, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy.
³ Department of Medical, Surgical and Health Sciences, University of Trieste, 34127 Trieste, Italy.
⁴ Department of Mechanical Engineering, Yeungnam University, Gyeongsan 38541, South Korea.
⁵ Department of Applied Chemistry, Konkuk University, Chungju 27478, South Korea.

Abstract

This paper reports on an ultrasensitive and label-free electrochemical immunosensor for monitoring the SARS-CoV-2 spike protein (SARS-CoV-2 SP). A self-supported electrode, which can simultaneously serve as an antibody immobilization matrix and electron transport channel, was initially fabricated by a controlled partial exfoliation of a flexible graphitic carbon foil (GCF). Mild acidic treatment enabled the partial oxidation and exfoliation (down to a few layers) of the flexible GCF; this also provided a high percentage of oxygen functionality and an enhanced surface roughness. The substrate electrode was further functionalized with ethylenediamine (EDA) to provide a suitable platform with even a higher surface roughness, for the covalent immobilization of an anti-SARS-CoV-2 antibody. The change in the current response for the [Fe(CN)₆]^3-/4- redox couple, induced by the binding of SARS-CoV-2 SP to the antibody immobilized on the electrode surface, was used to determine the SARS-CoV-2 SP concentration. The immunosensor thus prepared could detect SARS-CoV-2 SP within 30 min with high reproducibility and specificity over a wide concentration range (0.2-100 ng/mL). Detection limits of 25 pg/mL and 27 pg/mL were found in a phosphate buffer solution (pH 7.4), and diluted blood plasma, respectively. The immunosensor was also employed to detect SARS-CoV-2 SP in artificial human saliva.

Keywords: COVID-19; Functionalized flexible graphite foil; Immunosensors; Mild-oxidation; Self-supported electrode.