Fig. 1

Selection of the five anti-EGFR sdAbs from a fully human sdAb phage library. a The P/N ratios of sdAbs derived from a fully human sdAb phage library increased along with each round of library screening. b The output phages derived from each round of library screening against the EGFR protein fragment were used for polyclonal phage ELISA. PBS was included as a control. Data are shown as mean ± S.D. (n = 5). *P < 0.01 vs. the respective PBS control. c The output phages derived from the fifth round of library screening were collected. After TG1 was infected with the phages, phage clones were randomly picked, and their binding to the EGFR protein fragment were tested by monoclonal phage ELISA. The results of representative 32 clones were shown. The arrow marked the phage clone which could specifically bind to EGFR. d The specific binding of EGFR to the phage clones were further examined by monoclonal phage ELISA with the EGFR protein fragment and the other eight unrelated proteins (VEGF, EndoF1, CampH, HER2, BMP2, SPB2, FGF21 and CXCR4) as negative controls. The results of representative 12 clones were shown. The arrows marked the phage clones which specifically bound to EGFR. e The peptide sequences of the five anti-EGFR sdAbs (aEG1B4, aEG2C7, aEG2E12, aEG4D9 and aEG6B2) were predicted from their nucleotide sequences by the DNAMAN software. Complementarity determining regions (CDR) and framework region (FR) were indicated