Fig. 4.

ELISA elution results. (A) Elution in water as a function of pH. Complexes did not elute Abs in water after incubation for 1 or 10 days. Similarly, Abs were not released in water with pH values between 4 and 12. At the extreme pH of 3.5, Abs were released—as noted by an increase in Ab concentration. (B) Elution in media as a function of pH. Unlike elution in water, complexes readily eluted Abs in DMEM (+) serum with pH adjusted between 3.5 and 10.5. (C) Elution in DMEM (+) serum, DMEM (−) serum and inorganic salt solution consisting of three most abundant inorganic salts in DMEM after 1 day incubation. (D) Elution in inorganic salt solutions after 1 day incubation, as a function of salt concentration. Increasing NaCl and NaHCO₃ salt concentration has a positive effect on Ab elution, confirming the effect of inorganic salts on desorption. (E) Evaluation of eluted Ab activity after 1 day incubation. Concentration measurements from the activity independent ELISA and an activity dependent ELISA were similar, indicating no loss of anti-TGF-β₁ activity occurred during adsorption or elution. A decrease in reported concentration by the activity dependent ELISA when compared to the activity independent ELISA would have suggested a loss in Ab activity.