IFN‐γ and IL‐10 Immunosensor with Vertically Aligned Carbon Nanotube Interdigitated Electrodes toward Pen‐Side Cattle Paratuberculosis Monitoring

Highly sensitive vertically aligned carbon nanotube arrays (VANTAs) interdigitated electrode (IDE) arrays are developed for electrochemical biosensing of two cytokines (i.e., interleukin-10 (IL-10) and interferon-gamma (IFN-γ)) that are useful for early detection Johne's disease (Bovine Paratuberculosis) in cattle. The high aspect ratio VANTA-IDEs (50-60 µm in height) are grown through a chemical vapor deposition process from an iron (Fe) catalyst that is lithographically patterned on a silicon wafer with equal finger width and inter-finger spacing of 25 µm. After functionalization with distinct antibodies the VANTA-IDEs are capable of selective detection of both IL-10 and IFN-γ within an actual biological matrix (i.e., diluted bovine implant supernatant) over concentration ranges of 0.1 to 30 pg mL^-1 (limit of detection - LOD: 0.0911 pg mL^-1) and 50-500 pg mL^-1 (LOD: 24.17 pg mL^-1), respectively with a response time of <35 min. Results demonstrate important initial steps for rapid, pen-side identification of cattle with stage-I <i>Mycobacterium avium</i> subspecies <i>paratuberculosis</i> infection before physical symptoms of Johne's disease are present. Such a rapid pen-side diagnostic test can be used on cattle at an auction or before they are introduced to a herd to ensure the larger population does not become infected with Johne's disease.