An ELISA plate was coated with 50 ml mAbs 50 mg/ml. After washing and blocking, amplified phage diluted 5-fold was added to coated plate and incubated at RT for 1 h. After washing, 1:5000 diluted HRP-conjugated anti-M13 antibody (GE Healthcare) was added at RT for 1 h. OPD developed and was terminated with HCl. Optical density was measured at 490 nm.