Silica nanoparticles containing luminophors were utilized for quantitative information of protein. They were used for mass changes by quartz crystal microbalance and light intensity by electrogenerated chemiluminescence based on protein-protein interaction after proper surface modifications. Uniform-size Ru(bpy)32+-doped silica nanoparticles were prepared by water in oil microemulsion method and characterized by electrochemical method, photobleaching, and transmission electron microscopy (TEM). A sandwich type immunoassay system with the labeling of a luminophore, tris(2,2'-bipyridyl)- ruthenium(II), in the second antibody was demonstarted. (Fig. 1) For this purpose, Ru(bpy)32+-doped silica nanoparticles were synthesized and the particle size of the particle were controlled by various combinations of precursor. Details of interaction between IgG and anti-IgG and ECL efficiency for protein quantification will be discussed.