An ITO-based point-of-care colorimetric immunosensor for ochratoxin A detection

The accurate and rapid ochratoxin A (OTA) detection at early stage can prevent people from getting cancer to a great extent due to its strong liver toxicity and renal toxicity. The development of an efficient strategy to detect OTA without sophisticated instruments is highly desired, but still remains a severe challenge. In this communication, a sandwich type point-of-care testing (POCT) immunoassay is developed for OTA detection. The 3-aminopropyltrimethoxysilane-glutaraldehyde (APTMS-GA) is used as color matrix and Au-N-TiO₂ as labels for loading more captured antibodies and glucose oxidases (GOD). When glucose is added, GOD can be catalyzed to produce H₂O₂ which can weaken the color strength to quantify OTA concentrations. The mean gray values of reacted ITO-based immunosensors can be calculated by the software of Image J. The linear range of OTA is 0.0001-1 ng mL^-1 with a low detection limit of 28 fg mL^-1 at a signal-to-noise ratio of 3 s. This strategy can achieve the excellent performance without sophisticated instruments. This POCT method may has a potential application in the undeveloped countries with only a camera-equipped cellphone.