ABSTRACT
A simple competitive enzyme-linked immunosorbent assay (cELISA) was established for rapid measurement of secretory immunoglobulin A (sIgA) in saliva. The method was based on competitive reaction between the immobilized IgA and free IgA in the solution for the limited amount of horseradish peroxidase-conjugated rabbit anti-human IgA. In comparison with the conventionally used Sandwich ELISA, the cELISA is simpler, low-cost, and shows better reproducibility since it is not affected by the variation of capture antibodies from different batches. The assay time was also significantly reduced from more than 5h to less than 3h. Different curve-fitting models were compared, among which the fully specified logit-log model gave the best results. The linear working range and limit of detection were found to be 0.1-100 microg mL(-1) and 0.05 microg mL(-1), respectively. Matrix effects of saliva samples were investigated and a reasonable range of dilution factors were proposed. The developed method offers a very practical approach for high-throughput measurement of sIgA in saliva samples.
