Secretory immunoglobulin A (s-IgA), found in biological fluids, is useful for monitoring condition on mental health to prevent depression. In this study, the non-invasive detection of s-IgA in human sweat was demonstrated using field effect transistor (FET) biosensors modified with a plant lectin, jacalin, as a receptor. The s-IgA molecules were detected with greater sensitivity using the jacalin-immobilized FET biosensors as compared to the sensitivity shown by Fab-immobilized FET biosensors. Jacalin, which is a small lectin tetramer, has four glycan-binding sites and can capture a large number of s-IgA molecules within the charge-detectable region in terms of Debye length. Moreover, the jacalin-immobilized FET biosensor could detect s-IgA at concentrations ranging from 0.1 μg/mL to 100 μg/mL. Additionally, by using a filtration process to eliminate the interference of other components found in human sweat, our FET sensing system could specifically and quantitatively detect s-IgA. Therefore, our results show the utility of this device in monitoring mental stress.
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