Polyaniline metal dichalcogenide-based amplified aptasensor for SARS-CoV-2 spike glycoprotein detection in wastewater

The significance of nanocomposites (NCs) in the academic and industrial fields has been of great focus due to the combination of various qualities of different nanomaterials, with the aim of achieving controlled properties. In this work, the aptasensor fabrication consists of a SARS-CoV-2 spike glycoprotein specific thiolated aptamer (HS-Apt) immobilised on a surface of polyaniline (PANI) and 3-mercaptopropionic acid capped gadolinium telluride selenide quantum dots (3-MPA-GdTeSe) functionalised on a glassy carbon electrode (GCE). The interaction between the amine function of PANI and the carboxylic acid ligand of 3-MPA-GdTeSe was confirmed using Fourier transform infrared (FTIR) and Raman. Parameters such as pH, scan rate, and aptamer incubation of the aptasensor were optimized using cyclic voltammetry (CV). The latter parameter achieved an optimum electrochemical performance after 7 min (min) of aptamer incubation. The response of the aptasensor to a wide range concentration of SARS-CoV-2 spike glycoprotein (0–0.95 fM) was analysed using square wave voltammetry (SWV) and a linear response was observed in 0.1 M PBS during triplicate analysis. Furthermore, obtaining respective limits of detection and quantification of 0.04 and 0.4 fM. The fabricated aptasensor possessed good stability at room temperature and at 4 °C, retaining respective 74 and 75% electrochemical performance. The aptasensor showed good selectivity and achieved recoveries in a range of 98.6–101.4 and 91.5–103.1% and a relative standard deviation of < 3% for two respective wastewater effluents from Darville and Goudkoppies wastewater treatment plants. This technique could potentially find application in case of future illness outbreaks as an alternative environmental or clinical diagnostic tool.