MR of carcinoma-specific monoclonal antibody conjugated to monocrystalline iron oxide nanoparticles: the potential for noninvasive diagnosis.

PURPOSE To determine if tumor-specific monoclonal antibodies conjugated to superparamagnetic monocrystalline iron oxide nanoparticles can be used to yield specific diagnoses with the use of MR imaging. METHODS Monoclonal antibodies conjugated to monocrystalline iron oxide nanoparticles were given to nude rats with intracranial tumors either by intravenous injection, intraarterial injection with osmotic blood-brain barrier disruption, or direct intratumoral inoculation. Either L6, a tumor-specific antibody, or P-1.17, a control isotype-matched antibody, was used. Coronal T1-weighted, T2-weighted, and spoiled gradient-recalled acquisition in the steady state images were obtained before, 30 minutes after, 6 hours after, and 24 hours after injection. RESULTS Intravenous injection of greater than 2 mg of the tumor-specific antibody showed a specific pattern of enhancement of the tumors with the largest concentration of antibody in the area with the greatest density of tumor cells. The control antibody showed nonspecific changes. After intraarterial injection with barrier disruption to increase delivery globally or direct inoculation to increase delivery focally, no specific enhancement pattern was seen. CONCLUSION Monoclonal antibodies conjugated with monocrystalline iron oxide particles may provide a method to obtain specific diagnoses with the use of MR imaging.