Ultrasensitive protein detection using an Au/ZnO SPR-based biosensor

In this study, we demonstrated that the Au/ZnO nanocomposite films could be effectively used to enhance the performance of SPR for the detection of tumor marker. CA15.3 tumor marker for breast cancer was chosen as a model analyte. We analyzed experimentally intensity response to the samples that had different concentrations (0.0125 U/ml to 160 U/ml) in pleural fluid to evaluate the detection capability of the Au/ZnO SPR-based biosensor. As a result, it was found that the linear range extended from 0.025 to 40 U/ml with correlation coefficient of R = 0.9531 and the limit of detection at S/N of 3:1 reached 0.025U/ml. Compared with the shift degree of SPR intensity by the specific binding event between antibody and antigen, the change of intensity on the Au/ZnO layers increased at least 2 fold more than that on the Au/Cr layers. In addition, we determined that the Au/ZnO layers had a detection limit 4 times lower than the Au/Cr layers that were widespread use of the sensing interfaces on SPR. In conclusion, the use of Au/ZnO films greatly enhanced the SPR signal after carrying out bimolecular interactions and presented high sensitivity and reproducibility.