In this work, we investigated a new approach to shorten a measurement time of house dust mite (HDM) allergens with a surface acoustic wave (SAW) immunosensor for improvement of continuity in monitoring of airborne HDM. It was achieved by employing differential method with which a slope of phase change was used as a sensor output instead of a phase shift that was used conventionally. Compared to the conventional method, measurement time of Group 1 HDM allergens of Dermatophagoides farinae (Der f 1) was shortened by 10 min from 30 min, while a sensitivity of SAW immunosensor was comparable (limit of detection of 20.1 ng/mL). 300 ng/mL Der f 1 was repeatedly measured ten times by the differential method, and it resulted in highly reproduced sensor output as represented by a coefficient of variation of 5.7%. In addition, due to smaller amount of bound detection antibodies on the sensor surface, decline of the baseline during the semi-continuous measurement that happened in the conventional method was not observed. Selectivity of the differential method was also investigated with four different common environmental allergens including Der f 1. No significant output was observed from the samples without Der f 1, and a high selectivity of the differential method with SAW immunosensor was validated. These results suggest that use of the differential method with SAW immunosensor would lead to advanced semi-continuous measurement with high continuity of airborne HDM allergens when it is incorporated with a monitoring system.
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