Monoclonal antibody-coated magnetite particles as contrast agents for MR imaging and laser therapy of human tumors.

Abstract Attempts to improve human tumor detection by nonradioactive magnetic resonance techniques have led several investigators to develop antibody-linked para-magnetic contrast agents. Initial studies focused on gadolinium conjugated to monoclonal antibodies. However, very high levels of this contrast agent were needed to significantly reduce proton relaxation times and obtain improved MR images. The use of magnetite (Fe3O4) as an MR contrast agent provides a magnetic moment that is approximately one order of magnitude larger than gadolinium. In this study monoclonal antibodies 44 × 14 (specific for squamous cell carcinoma) and 436G10 (specific for melanoma) were obtained from ammonium sulfate precipitation of tumor ascitic fluid. Equal volumes of magnetite solution (1.87 mg Fe/ml) and antibody solution 44 × 14 (5.24 mg protein/ml) and 436G10 (0.64 mg protein/ml) were mixed and sonicated. The 44 × 14magnetite and 436G10-magnetite solutions were then added to equal volumes of M20 and P3 squamous cell ca...