A one-step immunoassay for carbohydrate antigen 19-9 by biosensor based on imaging ellipsometry.

Cancer markers can offer much more information for developing or developed cancers. Simple and short-time assay of cancer biomarker is essential for clinic diagnosis and management. In this study, a one-step immunoassay for carbohydrate antigen 19-9 (CA19-9) by biosensor based on imaging ellipsometry (BIE) is described and its analysis performances are evaluated. Anti-CA19-9 monoclonal antibody as ligand covalently immobilized on carboxyl-modified silicon substrate and its immobilization concentration concurrently screened. Then, bovine serum albumin (BSA) is used to block for acquisition of sensing layer. The detection linear range is from 15.0 to 120.0 U/mL with a minimum limit of 10.0 U/mL (S/N=3). The intra-slide and inter-slide reproducibility, expressed as coefficient variation (CV%), are 9.9, 5.9, 5.4% and 9.6, 7.6, 5.3% for 31.9, 57.4, and 99.2 U/mL of CA19-9, respectively. Accuracy determined by spiked-recovery is among 95.1-106.7%. Specificity expressed as cross-reaction rate are all below 5.8% evaluated by three analogous biomarkers alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and carbohydrate antigen 242 (CA242). Application of BIE to 25 clinic samples demonstrated that the results are in high correlate with electrochemiluminescent immunoassay (ECLIA, R2=0.997). The proposed immunoassay has the potential for clinic application.