EGFR and breast carcinoma: With this chemistry, fd phage bearing single-chain antibody fragment (scFv) groups previously determined to bind epidermal growth factor receptor (EGFR; Heitner et al., 2001) and human EGFR 2 (HER2; Poul et al., 2000) were modified with fluorophores and polyethylene glycol 2k (PEG2k) to create phage constructs that could distinguish breast cancer cell markers using fluorescence microscopy.