The anti-HER2-modified TiO2 micrometer sphere will bind to the surface of the MBT2 cell via interaction between anti-HER2 antibodies and extracellular domains of HER2 membrane proteins. Micrometer spheres bonded to cells scatter light of various wavelengths to various extents. The extinction coefficient of a particular wavelength is recorded to identify binding or its absence. (The scheme is simplified.)