Detection of IFN-γ for latent tuberculosis diagnosis using an anodized aluminum oxide-based capacitive sensor

• An AAO capacitive sensor is described to detect IFN-γ, a biomarker of latent TB.
• Binding of IFN-γ to anti-IFN-γ results in a decrease in capacitance, allowing the realtime detection.
• Non-specific binding is effectively blocked, allowing the detection of IFN-γ in human blood.
• The concentration of IFN-γ in the clinical samples is measured and compared with the ELISA kit.

We describe a rapid, sensitive, and label-free method to detect interferon-gamma (IFN-γ), a biomarker of latent tuberculosis infection (LTBI). IFN-γ is detected by measuring the capacitance change caused by its binding to an anti-IFN-γ antibody. The antibody is immobilized on the surface of an anodized aluminum oxide (AAO)-based capacitive sensor. With this technique, IFN-γ can be detected in the range of ~0.1 pg/ml to ~10 ng/ml, with a detection limit of 0.2 pg/ml. We have also measured the concentration of IFN-γ in clinical samples using the AAO-based capacitive sensor and compared this concentration with the results of the commercial QuantiFERON-TB Gold (QFT-G) ELISA kit to determine whether the two sets of data are consistent. Comparable results were obtained with the two measurement strategies, demonstrating the applicability of the AAO-based capacitive sensor to the diagnosis of LTBI.