For this, we labeled PEG-FUD and the mutated control peptide, PEG-mFUD, which has a compromised binding affinity for FN (37), with either Cyanine-5 (Cy5) fluorophore or 64Cu radiolabel, and tracked their distribution in human IPF tissue and in the murine model of the disease. This evidence concerns the gene FN1 and idiopathic pulmonary fibrosis.