I. Introduction
The Epidermal Growth Factor (EGF) receptor is over-expressed in many cancer cells and can be used for targeted magnetic resonance imaging (MRI). Epidermal growth factor (EGF) is a low molecular mass protein built of 53 amino acid residues, which contains three intramolecular disulfide bonds [1], [2]. EGF manifests high affinity to EGF receptor (EGFR) at the cell surface and stimulates its specific protein-tyrosine kinase activity. EGFR targeted nanoparticulated medicine is a perspective approach in therapy of breast, colorectal, lung and prostate cancer [3]–[6]. Anticancer therapy is usually accompanied by various types of analysis. Magnetic resonance imaging (MRI) is an approved widespread method of noninvasive monitoring of malignant soft tissues. The diagnostic efficiency of MRI could be further improved by use of contrast agents [7]. The contrast agents based on iron oxide magnetic nanoparticles (MNPs) are recommended for imaging of solid tumors in liver, spleen and stomach. The contrast effect obtained with the help of MNPs is provided by nonspecific accumulation of nanoparticles in specific cells uptaking nanoparticulated objects with high magnetic moment in the process of endocytosis. The binding of iron oxide MNPs with specifically targeted bioligands gives an additional contribution to MRI contrast enhancement due to specific targeting and accumulation of contrast agent in the tumor area. A group of specific ligands used for MNP modification includes monoclonal antibodies and small peptides such as EGF [8]–[10]. The coupling of EGF and iron oxide MNPs forms complexes that can be used in MRI diagnostics as the address-nanocarriers for differentiation of EGFR-overexpressed cells in tumors and healthy tissues.