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

We describe a rapid, sensitive, and label-free method to detect interferon-gamma (IFN-gamma), a biomarker of latent tuberculosis infection (LTBI). IFN-gamma is detected by measuring the capacitance change caused by its binding to an anti-IFN-gamma antibody. The antibody is immobilized on the surface of an anodized aluminum oxide (AAO)-based capacitive sensor. With this technique, IFN-gamma can be detected in the range of similar to 0.1 pg/ml to similar to 10 ng/ml, with a detection limit of 0.2 pg/ml. We have also measured the concentration of IFN-gamma 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. (C) 2013 Elsevier B.V. All rights reserved.