Combination of Carbon Nanofiber-Based Electrochemical Biosensor and Cotton Fiber: A Device for the Detection of the Middle-East Respiratory Syndrome Coronavirus.

The miniaturization of biosensors for point-of-care diagnosis is highly important in infection control. Electrochemical biosensors offer several advantages in diagnosis in terms of cost, disposability, portability, and sensitivity. Here, a miniaturized electrochemical immunosensor combined with cotton fiber for the detection of the Middle-East respiratory syndrome coronavirus (MERS-CoV) is described. Taking advantage of the absorption capability of cotton, the nasal and saliva samples can be collected and directly transferred to the immunosensor surface for detection using a single tool. The immunosensor was fabricated on a disposable screen-printed electrode precoated with carbon nanofibers. The electrodes were functionalized with carboxyphenyl groups that were used for the immobilization of the spike protein of the MERS-CoV. A competitive detection scheme was employed using the antibody for the MERS-CoV spike protein, and the square-wave voltammetry technique was used for measurements. The biosensor tested after the cotton coating of the electrode exhibited excellent performance. The biosensor was capable of detecting the MERS-CoV spike protein within a concentration range from 0.1 pg·mL to 1 μg·mL with a limit of detection of 0.07 pg·mL, implying the high sensitivity of the method. The immunosensor did not exhibit any cross-reactivity against proteins from HCoV and Influenza A, indicating the excellent selectivity of this approach. Testing of the biosensor in nasal samples showed very high recovery percentages. This disposable biosensor can be used as a miniaturized device for the collection of samples and detection of the virus using a portable potentiostat connected to a smartphone.