1. Center for Drug Evaluation and Research (B.S.Z., N.S.), Office of Pharmaceutical Science, Food and Drug Administration, Silver Spring, Maryland 20993;
2. Área de Inmunología and Unidad Compartida Complejo Hospitalario Universitario de Vigo (Á.G.-F.), Edificio Ciencias Experimentales, University of Vigo, Campus Lagoas Marcosende, 36310 Vigo, Pontevedra, Spain;
3. Nanotechnology Characterization Laboratory (M.A.D.), Science Apllications Internation Corp.-Frederick Inc., National Cancer Institute-Frederick, Frederick, Maryland 21703