Onion-like carbon re-inforced electrospun polyacrylonitrile fibres for ultrasensitive electrochemical immunosensing of Vibrio cholerae toxin

5•Electrospun onion-like carbon-polyacrylonitrile (OLC-PAN) hybrid is an excellent electrode material for immunosensors.5•OLC-PAN allows for an ultra-low detection (~ 10−17 g/mL) of V. cholerae toxin in water.5•The electrode performance decreases as OLC-PAN >> PAN >>> OLC.5•The ultrasensitive detection of OLC-PAN-based immunoelectrode is confirmed with both culture and PCR techniques.5•OLC-PAN hybrids provide an opportunity for future development of point-of-care diagnostic device for cholera. This work describes the use of electrospun onion-like carbon-polyacrylonitrile fibre (OLC-PAN) hybrids as an efficient electrode platform for electrochemical immunosensor for Vibrio cholerae toxin in water samples. First, the OLC-PAN nanohybrid was obtained by electrospinning technique. The immunosensor was constructed by covalent integration of the V. cholerae antibody on OLC-PAN hybrid-based glassy carbon electrode. The electrochemical detection of the antigen of the V. cholerae present in water samples was studied using the square wave voltammetry (SWV). The OLC-PAN-based electrode, unlike those of the individual components (OLC and PAN), showed excellent electrochemical sensing properties: as ultralow detection limit (LoD ≈ 2.5 × 10−17 g mL−1) and quantification limit (LoQ ≈ 3 × 10−15 g mL−1) and wide linear concentration range (10−13–10−5 g mL−1). The OLC-PAN-based electrochemical immunosensor was used to test for real water samples suspected to be infected with cholera, and successfully validated with both the gold-standard culture method and the polymerase chain reaction (PCR) technique. The PCR method showed poor sensitivity (LoD ≈ 5.0 × 10−7 g mL−1) compared with the SWV, proving the extremely high sensitivity and low-cost advantages of the electrochemical techniques over the conventional PCR. This work reveals the unique synergy between OLC and PAN that can be harnessed for potential development of high-performance electrochemical immunosensors for cholera disease in resource-limited communities. [Display omitted]