Highly selective and label-free Love-mode surface acoustic wave biosensor for carcinoembryonic antigen detection using a self-assembled monolayer bioreceptor

A Love-mode surface acoustic wave (SAW) biosensor based on ST-cut quartz was developed for highly selective and label-free detection of carcinoembryonic antigen (CEA). The delay line area of an interdigital transducer (IDT) based SAW device was coated with gold and then chemically modified through thioglycolic acid-EDC/NHS reaction mechanism. A self-assembled monolayer of anti-CEA was further immobilized on the bioreceptors through the coupling layer. The biosensing capability of the SAW device was evaluated using solutions of CFA with various concentrations and limit of detection was obtained at 0.31 ng/ml of CEA, which is better than the results reported by the literatures available for CFA detection using SAW device. The real-time detection capability of the biosensor was evaluated using clinical serum samples and selectivity was evaluated using mixed solutions of CFA with other common tumor marking proteins. Long-term stability of the biosensor was also evaluated over a period of 30 days and the immunoassay response has shown only 8% decrease in performance within the whole period. The binding of CEA onto the bioreceptor was evaluated through Langmuir and Freundlich sorption isotherm kinetic studies as well.