Development of an Au/ZnO thin film surface plasmon resonance-based biosensor immunoassay for the detection of carbohydrate antigen 15-3 in human saliva.

OBJECTIVE: To evaluate a novel surface plasmon resonance (SPR) system for the direct measurement of tumor marker carbohydrate antigen 15-3 (CA15-3) in human saliva. DESIGN AND METHODS: We measured the presence of the tumor marker carbohydrate antigen 15-3 (CA15-3) in human saliva using 2 different surface plasmon resonance (SPR) systems. To compare the sensitivity of an SPR biosensor based on thin-film Au/ZnO and the Biacore SPR system, we prepared CA15-3 samples in saliva and analyzed intensity responses to the samples at various concentrations of CA15-3.
RESULTS: The linear detection range of CA15-3 in human saliva with the SPR system based on thin-film Au/ZnO was 2.5-20 U/mL (the cut-off point in cancer patients is around 4 U/mL). The linear range with the Biacore SPR system was 40-300 U/mL.
CONCLUSIONS: These results show that thin-film Au/ZnO-based SPR systems have higher sensitivity and can be used for measuring the levels of CA15-3 in human saliva without concentrating the samples.