Comparative study of SPR and ELISA methods based on analysis of CD166/ALCAM levels in cancer and control human sera.

Surface plasmon resonance (SPR), as a label free method for analysis of various analytes, has significantly advanced in recent years. However, assessment of the performance of SPR compared to label-based immunoassays such as the commonly used multiplexed enzyme-linked immunosorbent assay (ELISA) is limited, particularly for applications involving complex media. In this work, an optimized SPR assay was implemented and its performance compared with an ELISA assay for CD166/activated cell leukocyte adhesion molecule (ALCAM), as candidate pancreatic cancer marker, based on direct and amplified detection in buffer and in human serum samples from healthy individuals and subjects with cancer. ALCAM antibody was immobilized on the surface of a four-channel SPR sensor via physical adsorption onto charged amine-terminated alkanethiolates to mimic the ELISA plate surface. Excellent correlations between SPR and ELISA results were achieved in buffer and in human serum. SPR detected the target protein with a similar sensitivity to sandwich ELISA, with a detection limit below ng/mL. The detection time, sample consumption, throughput, signal referencing, and surface blocking and washing for detection in human serum were evaluated. It is demonstrated that SPR can distinguish between ALCAM levels in cancer and control sera using direct detection without the need for additional amplification steps.