Micro open-sandwich ELISA to rapidly evaluate thyroid hormone concentration from serum samples

Background: Thyroxine (T4) is the most commonly measured thyroid hormone for the diagnosis of thyroid function. To elucidate a rapid and sensitive assay for T4, we made a microfluidics-based noncompetitive immunodetection chip system using anti-T4 antibody fragments obtained from a phage display library. Results: Based on the open-sandwich ELISA principle that detects antigen-dependency of the interaction between the two antibody variable regions V_H and V_L, we could detect less than 1 ng/ml of T4. The assay was also successfully applied to evaluate total T4 concentration in the serum of healthy individuals. Conclusion: This would be the first micro open-sandwich ELISA constructed with antibody fragments directly selected from immunized mice. The system will be applied to the sensitive detection of many diagnostic markers.