ELISA SOLID-PHASE - STABILITY AND BINDING CHARACTERISTICS

Stability of solid-phase antibody (SP-Ab) was investigated using polystyrene surface coated, by simple physical adsorption, with a rabbit antibody against the beta subunit of human chorionic gonadotropin. SP-Ab stored wet in 0.1 M Tris-HCl buffer, pH 7.2, or in 10% ammonium sulphate solution in the Tris buffer did not lose any activity upto the entire period of the study, i.e. 95 days at 6.degree. C and room temperature and 53 days at 40.degree. C. However, SP-Ab lost some activity upon drying and decrease in activity continued when air-dried SP-Ab was stored at any of these temperatures. Secondary coating of SP-Ab with sucrose or lactose before drying offered only partial protection to the activity of SP-Ab. Using radiolabeled antibody it was found that the loss of activity was not caused by desorption of the antibody; rather it could be the result of surface denaturation of the molecules. Binding of the antibody to polystyrene was so strong that week-long storage of SP-Ab in 6 M urea or 0.1% acetic acid could not bring about desorption by more than 1.8%. It is rcommended that SP-Ab should be stored in a buffer and should not be allowed to dry.