Development of Highly Efficient KinExA Immunosensor-Based Assay for the Measurement of Carcinoembryonic Antigen in Serum

Background: Elevated levels of Carcinoembryonic antigen (CEA) have been documented in different types of cancers, including ovarian, breast, cervical, small intestine, gastric, pancreatic, colon, rectal, and non-small-cell lung cancers. In addition, higher CEA levels have been found also in heavy smokers. CEA provides important evidence regarding the patient prognosis, recurrence of tumors postsurgical removal, and efficacy of treatment. For these reasons, a sensitive method is needed for determination of CEA levels. Objective: This study was devoted to the development of a new highly efficient kinetic exclusion analysis (KinExA) immunosensor-based assay for measurement of CEA in serum, and to overcome several drawbacks confronted in the conventional existing immunoassays for CEA. Methods: Polymethylmethacrylate (PMMA) beads were coated with CEA and charged into a microbead column in the observation cell of the KinExATM 3200 instrument. A pre-equilibrated mixture of CEA and its specific antibody was passed through the beads column, followed by passing a secondary fluorescently-labeled antibody through the beads column. The fluorescence signals were monitored by a camera installed inside the flow cell of the instrument, and used for generating the calibration curve of the assay. Results: The limit of detection for CEA with this assay was 0.2 μg/L. The advantage of KinExA platform was the instrument automation and high sensitivity that resulted in rapid and reliable quantification of CEA without any matrix effect. The analytical recovery of serum-spiked CEA was 93.3 – 106.9% and the relative standard deviation (%RSD) for the recovery ranged from 1.6 – 9.0%. The precisions of the assay were satisfactory; %RSD were 7.6 – 9.5 and 4.3 – 9.6% for the intra- and interassay precision, respectively. Conclusion: The automated analysis by the KinExA-based assay described herein facilitated the processing of a large number of specimens, and the new sensor-based assay is anticipated to have a great value in measurement of CEA. The proposed sensor-based assay provides a format to overcome the problems encountered in conventional immunoassays for CEA.