A Liquid Crystal Sensor Supported on an Aptamer-Immobilized Surface for Specific Detection of Ochratoxin A

In this study, a label-free liquid crystal (LC) aptasensor was developed to detect ochratoxin A (OTA) based on the change in the orientation of the LCs, using highly specific aptamer sequence for OTA as a recognition element. A chemically sensitive film with a specific molecular recognition ability was decorated on the substrate surface. In the absence of OTA molecules, a homeotropic orientation of the LCs was observed owing to the orientational properties of the functional substrate. However, in the presence of OTA, the immobilized aptamer binds with OTA and this reaction causes a great topographical change, producing an abrupt change in the orientation of the LCs. Thus, a random orientation is observed under a polarized optical microscope (POM) as a dark-to-bright image transition. The sensing system has a linear detection range from 1 to 100 ng mL
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and a low limit of detection of 0.9 ng mL
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. Notably, under optimum conditions, OTA can be effectively detected in grape juice and wine with high recovery and accuracy. This method has the advantages of high specificity, fast response, low cost, simple fabrication, and being a miniaturized platform for the quantitative and qualitative detection of OTA in buffer and real samples.