Targeting molecules are provided for use in delivering imaging agents to epithelial tissue. The targeting molecule comprises a polypeptide that forms a closed covalent loop, contains at least three peptide domains having -sheet character, each of the domains being separated by domains lacking -sheet character. The targeting molecule specifically binds to a basolateral factor attached to a basolateral domain of an epithelial cell surface causing internalization of a linked imaging agent into the cells. The polypeptide or imaging agent may be linked to a peptide amino acid sequence that directs delivery of the imaging agent to a carcinoma cell, a nucleus, or an endoplasmic reticulum.